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Patterns and ecological determinants of woody plant height in eastern Eurasia and its relation to primary productivity
Zhiheng Wang, Yaoqi Li, Xiangyan Su, Shengli Tao, Xiao Feng, Qinggang Wang, Xiaoting Xu, Yunpeng Liu, Sean T. Michaletz, Nawal Shrestha, Markku Larjavaara, and Brian J. Enquist
J Plant Ecol    2019, 12 (5): 791-803.   DOI: 10.1093/jpe/rtz025
Abstract125)      PDF (2852KB)(35)       Save
Aims

Plant height is a key functional trait related to aboveground biomass, leaf photosynthesis and plant fitness. However, large-scale geographical patterns in community-average plant height (CAPH) of woody species and drivers of these patterns across different life forms remain hotly debated. Moreover, whether CAPH could be used as a predictor of ecosystem primary productivity is unknown.

Methods

We compiled mature height and distributions of 11 422 woody species in eastern Eurasia, and estimated geographic patterns in CAPH for different taxonomic groups and life forms. Then we evaluated the effects of environmental (including current climate and historical climate change since the Last Glacial Maximum (LGM)) and evolutionary factors on CAPH. Lastly, we compared the predictive power of CAPH on primary productivity with that of LiDAR-derived canopy-height data from a global survey.

Important Findings

Geographic patterns of CAPH and their drivers differed among taxonomic groups and life forms. The strongest predictor for CAPH of all woody species combined, angiosperms, all dicots and deciduous dicots was actual evapotranspiration, while temperature was the strongest predictor for CAPH of monocots and tree, shrub and evergreen dicots, and water availability for gymnosperms. Historical climate change since the LGM had only weak effects on CAPH. No phylogenetic signal was detected in family-wise average height, which was also unrelated to the tested environmental factors. Finally, we found a strong correlation between CAPH and ecosystem primary productivity. Primary productivity showed a weaker relationship with CAPH of the tallest species within a grid cell and no relationship with LiDAR-derived canopy height reported in the global survey. Our findings suggest that current climate rather than historical climate change and evolutionary history determine the geographical patterns in CAPH. However, the relative effects of climatic factors representing environmental energy and water availability on spatial variations of CAPH vary among plant life forms. Moreover, our results also suggest that CAPH can be used as a good predictor of ecosystem primary productivity.

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Climatic and fire determinants of early life-history stages in the Mediterranean shrub Cistus albidus
Sandra Saura-Mas, Anna Saperas and Franciso Lloret
J Plant Ecol    2020, 13 (1): 3-11.   DOI: 10.1093/jpe/rtz040
Online available: 20 November 2019

Abstract95)      PDF       Save
Aims

Cistus albidus reproductive traits have been studied on typical Mediterranean shrublands along a water availability gradient in Northeastern Iberian Peninsula. Germination of this species is known to be highly favoured by fire. Moreover, Mediterranean species are particularly dependent on water availability. Therefore, we establish the hypothesis that in addition to fire disturbance, seedling recruitment in this Mediterranean seeder will be improved in drought-induced episodes resulting in generalized canopy die-off.

Methods

Individuals of several populations of C. albidus were collected and the size, weight and number of fruits and seeds were measured. Germination tests were also carried out on five pre-germination treatments: seeds’ exposure to heat shock, imbibition, two cycles of imbibition/desiccation and the combination of heat shock and imbibition and imbibition/desiccation cycles. Moreover, the number of seedlings after a drought event was surveyed in the field and correlated with canopy die-off.

Important findings

Our study shows the variability of the C. albidus reproductive traits, such as germination rate or fruit production, along the water availability gradient. This variability resulted in a decrease in fruit production but an increase in successful germination under drier conditions. Cistus albidus seeds increased germination with heat, demonstrating their ability to successfully establish after fire. However, recruitment was not exclusively fire dependent since seedling establishment was higher under C. albidus canopies that had collapsed after the extreme drought. Finally, adult density increased C. albidus die-off and mortality, as well as seedling establishment. These results suggest that this species exhibits a trade-off between different reproductive outcomes (i.e. seed production vs. viability), which in turn is determined by climate. This study also provides evidence of how intra-specific competition, climate, particularly drought events and fire disturbance, can determine the success of key early stages of the life history of a common, representative Mediterranean fire-prone seeder shrub.

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Intraspecific trait variation improves the detection of deterministic community assembly processes in early successional forests, but not in late successional forests
Shuai Fang, Marc William Cadotte, Zuoqiang Yuan, Fei Lin, Ji Ye, Zhanqing Hao and Xugao Wang
J Plant Ecol    2019, 12 (4): 593-602.   DOI: 10.1093/jpe/rty053
Abstract87)      PDF       Save
Aims

Intraspecific trait variation (ITV) has been increasingly recognized to play an important role in understanding the underlying processes influencing community assembly. However, gaps remain in our understanding of how incorporating ITV will influence the relative importance of deterministic (e.g. habitat filtering, limiting similarity) and stochastic processes in driving community assembly at different successional stages.

Methods

We used data for eight functional traits from 55 woody species in early (24 ha) and late (25 ha) successional temperate forest plot in northeast China. We employed an approximate Bayesian computation approach to assess the relative contribution of stochastic processes, habitat filtering and limiting similarity in driving community structure. We then compared the results with and without intraspecific trait variation to investigate how ITV influences the inferred importance of each process.

Important Findings

We found that when analyzing interspecific trait variation only (i.e. without ITV), stochastic processes were observed most frequently in driving community composition, followed by habitat filtering and limiting similarity in both forests. However, ITV analyses showed that the relative importance of both deterministic processes (habitat filtering and limiting similarity) increased in early successional forest, but remained virtually unchanged in late successional forest. Our study reveals the distinctive influence of ITV on the inference of underlying processes in a context of succession and reinforces the need to estimate ITV for making correct inferences about underlying ecological processes.


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Examining residual spatial correlation in variation partitioning of beta diversity in a subtropical forest

Ke Cao, Xiangcheng Mi, Liwen Zhang, Haibao Ren, Mingjian Yu, Jianhua Chen, Jintun Zhang and Keping Ma
J Plant Ecol    2019, 12 (4): 636-644.   DOI: 10.1093/jpe/rty058
Online available: 07 January 2019

Abstract79)      PDF       Save
Aims

The relative roles of ecological processes in structuring beta diversity are usually quantified by variation partitioning of beta diversity with respect to environmental and spatial variables or gamma diversity. However, if important environmental or spatial factors are omitted, or a scale mismatch occurs in the analysis, unaccounted spatial correlation will appear in the residual errors and lead to residual spatial correlation and problematic inferences.

Methods

Multi-scale ordination (MSO) partitions the canonical ordination results by distance into a set of empirical variograms which characterize the spatial structures of explanatory, conditional and residual variance against distance. Then these variance components can be used to diagnose residual spatial correlation by checking assumptions related to geostatistics or regression analysis. In this paper, we first illustrate the performance of MSO using a simulated data set with known properties, thus making statistical issues explicit. We then test for significant residual spatial correlation in beta diversity analyses of the Gutianshan (GTS) 24-ha subtropical forest plot in eastern China.

Important Findings

Even though we used up to 24 topographic and edaphic variables mapped at high resolution and spatial variables representing spatial structures at all scales, we still found significant residual spatial correlation at the 10 m × 10 m quadrat scale. This invalidated the analysis and inferences at this scale. We also show that MSO provides a complementary tool to test for significant residual spatial correlation in beta diversity analyses. Our results provided a strong argument supporting the need to test for significant residual spatial correlation before interpreting the results of beta diversity analyses.

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Opposite effects of nitrogen fertilization and plastic film mulching on crop N and P stoichiometry in a temperate agroecosystem
Fan Ding, Shuangyi Li, Xiao-Tao Lü, Feike A. Dijkstra, Sean Schaeffer, Tingting An, Jiubo Pei, Liangjie Sun and Jingkuan Wang
J Plant Ecol    2019, 12 (4): 682-692.   DOI: 10.1093/jpe/rtz006
Online available: 24 January 2019

Abstract71)      PDF       Save
Aims

Crop nitrogen (N) and phosphorus (P) stoichiometry can influence food nutritive quality and many ecosystem processes. However, how and why N and P stoichiometry respond to long-term agricultural management practices (e.g. N fertilization and film mulching) are not clearly understood.

Methods

We collected maize tissues (leaf, stem, root and seed) and soil samples from a temperate cropland under 30-year continuous N fertilization and plastic film mulching treatments, measured their C, N and P concentrations (the proportion (%) relative to the sample mass), and used structural equation models to uncover the responding mechanisms for crop N and P contents (the total amount (g/m2) in crop biomass).

Important Findings

Long-term N fertilization increased N concentrations in all crop tissues but sharply decreased P concentrations in vegetative tissues (leaf, stem and root), thereby reducing their C/N ratio and increasing C/P and N/P ratios. The drop in P concentration in vegetative tissues was due to the dilution effect by biomass increment and the priority of P supply for seed production. In contrast, film mulching decreased N concentration but increased P concentrations in most crop tissues, thereby increasing C/N ratio and reducing C/P and N/P ratios. Film mulching increased crop P content by increasing soil temperature and moisture; whereas, mulching showed little effect on crop N content, because a positive effects of soil temperature may have canceled out a negative effect by soil moisture. This indicated a decoupling of P and N uptake by crops under film mulching. In conclusion, N fertilization and plastic film mulching showed opposite effects of on crop N and P stoichiometry.

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Changes in productivity and carbon storage of grasslands in China under future global warming scenarios of 1.5°C and 2°C
Zhaoqi Wang, Jinfeng Chang, Shushi Peng, , Shilong Piao, Philippe Ciais and Richard Betts
J Plant Ecol    2019, 12 (5): 804-814.   DOI: 10.1093/jpe/rtz024
Abstract69)      PDF       Save
Aims

The impacts of future global warming of 1.5°C and 2°C on the productivity and carbon (C) storage of grasslands in China are not clear yet, although grasslands in China support ~45 million agricultural populations and more than 238 million livestock populations, and are sensitive to global warming.

Methods

This study used a process-based terrestrial ecosystem model named ORCHIDEE to simulate C cycle of alpine meadows and temperate grasslands in China. This model was driven by high-resolution (0.5° × 0.5°) climate of global specific warming levels (SWL) of 1.5°C and 2°C (warmer than pre-industrial level), which is downscaled by EC-EARTH3-HR v3.1 with sea surface temperature and sea-ice concentration as boundary conditions from IPSL-CM5-LR (low spatial resolution, 2.5° × 1.5°) Earth system model (ESM).

Important Findings

Compared with baseline (1971–2005), the mean annual air temperature over Chinese grasslands increased by 2.5°C and 3.7°C under SWL1.5 and SWL2, respectively. The increase in temperature in the alpine meadow was higher than that in the temperate grassland under both SWL1.5 and SWL2. Precipitation was also shown an increasing trend under SWL2 over most of the Chinese grasslands. Strong increases in gross primary productivity (GPP) were simulated in the Chinese grasslands, and the mean annual GPP (GPPMA) increased by 19.32% and 43.62% under SWL1.5 and SWL2, respectively. The C storage increased by 0.64 Pg C and 1.37 Pg C under SWL1.5 and SWL2 for 50 years simulations. The GPPMA was 0.670.880.39 (0.82) (model meanmaxmin0.670.390.88 (0.82) (model meanminmax (this study)), 0.851.240.45 (0.97)0.850.451.24 (0.97) and 0.941.300.61 (1.17)0.940.611.30 (1.17) Pg C year−1 under baseline, SWL1.5 and SWL2 modeled by four CMIP5 ESMs (phase 5 of the Coupled Model Inter-comparison Project Earth System Models). In contrast, the mean annual net biome productivity was −18.554.47−40.37 (−3.61),−18.55−40.374.47 (−3.61),18.6564.03−2.03 (10.29)18.65−2.0364.03 (10.29) and 24.1538.778.38 (24.93)24.158.3838.77 (24.93) Tg C year−1 under baseline, SWL1.5 and SWL2 modeled by the four CMIP5 ESMs. Our results indicated that the Chinese grasslands would have higher productivity than the baseline and can mitigate climate change through increased C sequestration under future global warming of 1.5°C and 2°C with the increase of precipitation and the global increase of atmospheric CO2 concentration.

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Review on global change status and its impacts on the Tibetan Plateau environment
Aamir Latif, Sana Ilyas, Yangjian Zhang, Yuqin Xin, Lin Zhou and Quan Zhou
J Plant Ecol    2019, 12 (6): 917-930.   DOI: 10.1093/jpe/rtz038
Abstract65)      PDF       Save

The Tibetan Plateau (TP) holds fundamental ecological and environmental significances to China and Asia. The TP also lies in the core zone of the belt and road initiative. To protect the TP environment, a comprehensive screening on current ecological research status is entailed. The teased out research gap can also be utilized as guidelines for the recently launched major research programs, i.e. the second TP scientific expedition and silk and belt road research plan. The findings showed that the TP has experienced significant temperature increase at a rate of 0.2°C per decade since 1960s. The most robust warming trend was found in the northern plateau. Precipitation also exhibited an increasing trend but with high spatial heterogeneity. Changing climates have caused a series of environmental consequences, including lake area changes, glacier shrinkage, permafrost degradation and exacerbated desertification. The rising temperature is the main reason behind the glaciers shrinkage, snow melting, permafrost degradation and lake area changes on the TP and neighboring regions. The projected loss of glacial area on the plateau is estimated to be around 43% by 2070 and 75% by the end of the century. Vegetation was responsive to the changed environments, varied climates and intensified human activities by changing phenology and productivity. Future global change study should be more oriented toward integrating various research methods and tools, and synthesizing diverse subjects of water, vegetation, atmosphere and soil.

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Size- and age-dependent increases in tree stem carbon concentration: implications for forest carbon stock estimations
Su-Hui Ma, Anwar Eziz, Di Tian, Zheng-Bing Yan, Qiong Cai, Min-Wei Jiang, Cheng-Jun Ji and Jing-Yun Fang
J Plant Ecol    2020, 13 (2): 233-240.   DOI: 10.1093/jpe/rtaa005
Online available: 04 February 2020

Abstract63)      PDF       Save
Aims

Forest biomass carbon (C) stocks are usually estimated by multiplying biomass by a C conversion factor, i.e. C concentration. Thus, tree C concentration is crucial to the assessments of forest C cycles. As stems contribute to the large fraction of tree biomass, the canonical value of 50% or other simplified values of stem C concentration are widely used to represent the values of tree C concentration in the estimations of forest C stocks at different scales. However, C concentration variations between tree organs and within tree size and their impacts on forest C stocks are still unclear.

Methods

We conducted a global analysis of organ C concentration in age-specific trees based on 576 records of tree age, size (diameter at breast height and biomass) and C concentration data to evaluate the relationships between organ C concentrations and the changes of stem C concentration with tree age and size.

Important Findings

Tree C concentration varied significantly with organs. Stem C concentration of trees was significantly correlated with that of other tree organs, except for barks and reproductive organs. The stem C concentration increased significantly with tree size and age, which contributed to the increases in C contents of stems and trees. Using the C concentration in stems to represent the C concentrations of other organs and the whole tree could produce considerable errors in the estimations of forest C stocks (−8.6% to 25.6% and −2.5% to 5.9%, respectively). Our findings suggest that tree C accumulation in forests is related to the size- and age-dependent increases in stem C concentration and using specific C concentration values of tree organs can improve the estimations of forest C stocks.

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The invasive potential of a hybrid species: insights from soil chemical properties and soil microbial communities
Feng Sun, Yuyi Ou, Qiaojing Ou, Lingda Zeng, Hanxia Yu, Jin Zheng, Lei Gao, Weihua Li, Na Li and Changlian Peng
J Plant Ecol    2020, 13 (1): 20-26.   DOI: 10.1093/jpe/rtz050
Online available: 15 November 2019

Abstract63)      PDF       Save
Aims

Natural hybridization between invasive and native species, as a form of adaptive evolution, threatens biodiversity worldwide. However, the potential invasive mechanisms of hybrids remain essentially unexplored, especially insights from soil chemical properties and soil microbial communities.

Methods

In a field experiment, soil microbial community, potassium-solubilizing bacteria, phosphorus-solubilizing bacteria, enzyme activities, and light-saturated photosynthetic rate were measured in invasive Sphagneticola trilobata and its hybrid with native Sphagneticola calendulacea in 2 years.

Important Findings

In general, soil dissolved organic carbon and the biomass of phosphorus-solubilizing bacteria were significantly higher under the hybrid treatment than S. trilobata and S. calendulacea. However, there were no significant differences in acid phosphatase, total PLFAs, bacterial PLFAs, fungi PLFAs, cellulase, and urase in these treatments. The hybrids had significantly higher light-saturated photosynthetic rate, photosynthetic nitrogen-, phosphorus-, potassium- use efficiencies than the invasive S. trilobata, but no significant difference with S. calendulacea. The total biomass and root biomass of hybrids were higher than S. calendulacea. Our results indicate that the hybrids species have a higher invasive potential than S. calendulacea, which may aggravate the local extinction of S. calendulaceain the future.

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Resorption-related nitrogen changes in the leaves and roots of Larix kaempferi seedlings under nutrient-sufficient and nutrient-starvation conditions
Tao Yan, Jiaojun Zhu, Huanhuan Song and Kai Yang
J Plant Ecol    2019, 12 (4): 615-623.   DOI: 10.1093/jpe/rty056
Online available: 27 December 2018

Abstract63)      PDF       Save
Aims

Larch is the dominant timber species in Northeast China. However, compared with the adjacent secondary forests, soil available nitrogen (N) significantly declined in ~40-year-old larch plantations. Thus, it is of great importance to determine how N use strategies in larch change in response to declining soil N availability.

Methods

We investigated the changes in N concentration and 15N natural abundance (δ15N) from 18 August to 25 October in the leaves, stems, branches and roots of 1-year-old Larix kaempferi seedlings under nutrient-sufficient (NSu) and nutrient-starvation (NSt) conditions with a pot experiment in Northeast China.

Important Findings

Stem and branch N concentrations exhibited upward trends, and leaf N concentration exhibited a downward trend. Root N concentration exhibited an upward trend under NSu conditions, but a downward trend under NSt conditions. These results suggested that stems and branches were served as N storage organs, but roots shifted from storage to resorption organs when switched from NSu to NSt. Leaf nutrient resorption was intensely occurred on 11 October, as indicated by the sharply decreased leaf N concentration and increased stem, root and branch N concentrations. The δ15N of roots, branches and leaves overlapped between NSu and NSt approximately on 11 October, which may be regulated by isotope discrimination during N resorption. Leaf N resorption efficiency under NSt (76.33%) was significantly higher than that of NSu (56.76%), indicating that nutrient stress stimulates leaf N resorption. Taken together, larch seedlings enhance leaf nutrient resorption and shift roots from nutrient storage to nutrient resorption to adapt to NSt conditions. These changes might relieve the adverse effects of declining soil nutrient availability on seedling survival and regeneration.

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Geographic patterns of plant–herbivore interactions are driven by soil fertility
Joshua S. Lynn and Jason D. Fridley
J Plant Ecol    2019, 12 (4): 653-661.   DOI: 10.1093/jpe/rtz002
Online available: 14 January 2019

Abstract61)      PDF       Save
Aims

Geographic patterns of the intensity of plant herbivory in relation to climate factors have garnered little general support and appear to be species specific. However, plant–herbivore interactions are also driven by resource availability, such as soil nutrient content, and it remains unclear whether broad-scale variation in soil factors is reflected in herbivore consumption rates across species’ ranges. Additionally, we know little of how intraspecific variation in tissue quality associates with edaphic and climatic factors, and how this variation controls herbivore consumption. The resource availability hypothesis (RAH) predicts that plant individuals growing in low-resource environments will have lower leaf nutritional quality and more constitutive defenses, which will result in lower rates of leaf consumption.

Methods

We collected leaves from the old-field dominant species, Solidago altissima L., from 20 sites across 10 degrees of latitude in the Eastern USA to determine the percentage leaf area consumed by insect folivores. We obtained soil and climate data for each site, as well as plant functional and defensive traits, including specific leaf area (SLA), leaf carbon:nitrogen (C:N), and trichome density.

Important Findings

Although we found no significant latitudinal trend of leaf consumption rate, there was strong evidence that leaf herbivory decreased with leaf C:N and trichome density, which themselves decreased with soil N, supporting our hypothesis that the RAH applies for intraspecific variation across spatial gradients. Additionally, high precipitation seasonality and soil nitrogen predicted decreased herbivory. The results suggest that spatial variation in herbivory can be driven by factors other than herbivore communities and climatic gradients, and that bottom-up processes, where plant traits and soil fertility control leaf consumption, must be incorporated into spatial predictions of herbivory.

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Relative contributions of biotic and abiotic factors to the spatial variation of litter stock in a mature subtropical forest
Jing Wang, Qingsong Yang, Yang Qiao, Deli Zhai, Lifen Jiang, Guopeng Liang, Xiaoying Sun, Ning Wei, Xihua Wang and Jianyang Xia
J Plant Ecol    2019, 12 (4): 769-780.   DOI: 10.1093/jpe/rtz018
Online available: 26 March 2019

Abstract61)      PDF       Save
Aims

Dead plant material (i.e. litter) is the major source of soil organic matter and thus plays a fundamental role in regulating soil carbon cycling in global forest ecosystems. The storage of litter is jointly determined by its production from plants and decomposition in a given environment. However, only few studies have explored the relative importance of environmental (i.e. abiotic) and plant (i.e. biotic) factors in driving the spatial variation of litter mass. The objective of this study is to quantify the relative contributions of biotic and abiotic factors in affecting the spatial variation of aboveground litter stock in a mature subtropical forest.

Methods

The aboveground litter mass was sampled in 187 grids of a 20-hm forest dynamics plot in a subtropical broad-leave forest in eastern China. The contributions of environmental variables, topographical and species variables on litter stocks were quantified by the boosted regression tree analysis.

Important Findings

The mean aboveground litter stock was 367.5 g m?2 in the Tiantong dynamics forest plot across all the 187 grids. The litter stock ranged from 109.2 to 831.3 g m?2 and showed a large spatial variation with the coefficient of variance as 40.8%. The boosted regression tree analysis showed that slope elevation and soil moisture were the most influential variables on the spatial variation of litter stock. The relatively influence of abiotic factors (environmental and topographical factors) was 71.4%, which is larger than biotic factors (28.6%). Overall, these findings suggest that abiotic factors play a more important role than plants in driving the spatial variation of aboveground litter stock in the subtropical forest. Given that the global carbon-cycle models have been aiming to refine from the hundred kilometers to sub-kilometer scale, this study highlights the urgency of a better understanding of the spatial variation of litter stock on the fine scale.

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Pure and mixed plantations of Persian walnut (Juglans regia L.) for high quality timber production in Chile, South America
Verónica Loewe-Muñoz, Mónica Balzarini, Marta Ortega González
J Plant Ecol    2020, 13 (1): 12-19.   DOI: 10.1093/jpe/rtz042
Online available: 22 August 2019

Abstract61)      PDF       Save
Aims

Persian walnut (Juglans regia L.), an interesting forest species for the veneering industry, requires adequate management to produce valuable high-quality logs. Since species associations and management level can improve stand productivity, the novelty of this work was to assess Persian walnut performance in different planting mixtures and in pure plantations conditioned to management intensity.

Methods

Growth, straightness and survival measurements were taken annually for 7 years after planting pure and mixed plantations under two contrasting management scenarios. Diseases were recorded at Age 7 in all plantations. Under each management intensity, besides the monoculture, three mixtures were tested: a mixture of only main forest species, main forest species plus one arboreal companion species, Black alder (Alnus glutinosa L.) and main species plus the shrub Russian olive (Elaeagnus angustifolia L.) as nurse species. A test of interaction between plantation type and management scenario was conducted using repeated growth data.

Important Findings

The interaction was significant, indicating the presence of different mechanisms underlying plantation effects under high and low management level. Compared with pure plantations, Persian walnut associated with the nurse shrub exhibited 78% higher height and 53% higher diameter growth in plantations under low management. Health benefits (lower presence of walnut blight than in the monoculture) and better straightness were also found in the association including the shrub when the management intensity was not high. These beneficial effects in the presence of Russian olive were not present under high management intensity (irrigation, fertilization, tutoring and frequent pruning). Site-specific designs for Persian walnut plantations would depend on the foreseen management intensity.

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Fraying around the edges: negative effects of the invasive Tradescantia zebrina Hort. ex Bosse (Commelinaceae) on tree regeneration in the Atlantic Forest under different competitive and environmental conditions
Wagner A. Chiba de Castro, Rafael O. Xavier, Federico H. L. Garrido, Jair H. C. Romero, Cleto K. Peres and Ruberval C. da Luz
J Plant Ecol    2019, 12 (4): 713-721.   DOI: 10.1093/jpe/rtz009
Online available: 13 February 2019

Abstract60)      PDF       Save
Aims

Invasive plants modify the structure and functioning of natural environments and threat native plant communities. Invasive species are often favored by human interference such as the creation of artificial forest edges. Field removal experiments may clarify if invasive plants are detrimental to native plant regeneration and how this is related to other local factors. We assessed the joint effect of environment and competition with the invasive Tradescantia zebrina on tree species recruitment in an Atlantic Forest fragment.

Methods

We carried out the experimental study in the Igua?u National Park, located in southern Brazil, using 30 plots distributed across five invaded sites during 6 months. We counted T. zebrina leaves and recorded the abundance and height of tree recruits over time under contrasting environmental (forest edge vs. forest interior) and removal (all aboveground biomass, only T. zebrina removal, and control) treatments. We analyzed the effects of environment and removal treatment using generalized linear mixed models.

Important Findings

The invasive species performed better at the forest edge than in the interior. The higher competitive pressure of T. zebrina led to higher mortality and lower height of tree recruits. Invader removal favored tree recruitment, especially in the forest interior. Our study shows that T. zebrina hampers woody species regeneration in tropical Atlantic Forests, especially at the forest edge.

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Effects of clonal integration and nitrogen supply on responses of a clonal plant to short-term herbivory
Bi-Cheng Dong, Li-Min Zhang, Kai-Yu Li, Xiao-Ting Hu, Pu Wang, Yong-Jian Wang, Fang-Li Luo, Hong-Li Li and Fei-Hai Yu
J Plant Ecol    2019, 12 (4): 624-635.   DOI: 10.1093/jpe/rty057
Online available: 02 January 2019

Abstract59)      PDF       Save
Aims

Clonal integration, i.e. resource sharing between interconnected ramets, can help clonal plants tolerate abiotic stress. However, few studies have directly examined the ecological significance of clonal integration in the ability of clonal plants to tolerate biotic stress such as herbivory.

Methods

We grew clonal fragments of an invasive clonal plant Alternanthera philoxeroides, each consisting of an apical part (relatively young) and a basal part (relatively old), at two levels (low and high) of soil nitrogen (N). For each fragment, the apical part was subjected to either no herbivory or herbivory for 2 weeks by a specialist insect, Agasicles hygrophila, and was either connected with or disconnected from the basal part not subjected to herbivory.

Important Findings

Herbivory in the apical part severely reduced leaf growth (leaf mass, leaf number or leaf area) and ramet production of both apical and basal parts, and increased root to shoot ratio of the apical part. Irrespective of herbivory and soil N, stem connection between the apical and the basal part decreased root to shoot ratio of the apical part, but did not change its growth measures. Meanwhile, connection increased stem N concentration of the apical part growing under high-N supply and decreased stem carbon (C) concentration of the apical part under low-N supply. By contrast, connection increased root to shoot ratio of the basal part, but reduced its leaf and ramet production. Connection also increased leaf and stem C concentrations of the basal part under low-N supply. Thus, clonal integration can be beneficial for the early development of young A. philoxeroides ramets, but not for their local adaptation to herbivory damage by A. hygrophila.

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Weighted average regression and environmental calibration as a tool for quantifying climate-driven changes in vegetation
Kuber Prasad Bhatta, Harry John Betteley Birks, John-Arvid Grytnes and Ole Reidar Vetaas
J Plant Ecol    2019, 12 (4): 787-789.   DOI: 10.1093/jpe/rtz015
Online available: 08 May 2019

Abstract59)      PDF       Save
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Effects of fire and nitrogen addition on photosynthesis and growth of three dominant understory plant species in a temperate forest
Mengjun Hu and Shiqiang Wan
J Plant Ecol    2019, 12 (4): 759-768.   DOI: 10.1093/jpe/rtz014
Online available: 12 March 2019

Abstract57)      PDF       Save
Aims

Fire and atmospheric nitrogen (N) deposition have the potential to influence growth and productivity of forest canopy. However, their impacts on photosynthesis and growth traits of understory plants in forests remain largely unexplored. This study was conducted to examine the effects of burning and N addition on foliar N content, net photosynthesis and growth traits of three dominant shrub species (Vitex negundoLindera glauca and Symplocos chinensis) in a temperate forest in Central China.

Methods

The experiment used a pair-nested design, with four treatments (control, burning, N addition and burning plus N addition) and five replicates. Leaf mass area (LMA), area-based concentrations of foliar N and chlorophyll (Narea and Chlarea), net photosynthesis (An), stomatal conductance (gs), maximum photosynthetic rate (Amax) and maximal carboxylation rate (Vcmax), basal diameter, height and branch length (BL) of the three species were measured.

Important Findings

Across the three species, burning stimulated LMA, Narea, ChlareaAngsAmax and Vcmax, and consequently enhanced basal diameter, height and BL. Nitrogen addition increased An and gs but did not affect LMA, Narea, ChlareaAmaxVcmax, basal diameter, height or BL. However, N addition strengthened the positive effects of burning on gsVcmaxAn and BL. The findings indicate the primary role of light resources in determining plant photosynthesis and growth of understory shrub species after fire and highlight that understory plants should be considered in projection of biomass accumulation and productivity of forests under environmental perturbations.

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Impacts of short-term nitrogen addition on the thallus nitrogen and phosphorus balance of the dominant epiphytic lichens in the Shennongjia mountains, China
Ming Wang, Chuanhua Wang, Lin Yang and Hua Guo
J Plant Ecol    2019, 12 (4): 751-758.   DOI: 10.1093/jpe/rtz013
Online available: 07 March 2019

Abstract56)      PDF       Save
Aims

To better understand whether and how nitrogen addition impacts the epiphytic lichens in the Shennongjia Nature Reserve (China).

Methods

Five dominant epiphytic lichen species, including Usnea longissimaU. luridorufaRamalina calicaris var. japonicaU. dasopoga and U. betulina, were selected as materials, and then field and laboratory nitrogen addition experiments were performed. The phosphomonoesterase (PME) activity and nitrogen (N) and phosphorus (P) content of these lichens were measured, and then the effects of nitrogen addition on thallus nutrient balance and PME activity were discussed.

Important Findings

Our results showed that with an increased N deposition from 0.6 to 50 kg N ha?1 a?1, the thallus N content of the five lichen species increased significantly, suggesting that those lichens had strong ability to take up and accumulate N, and an universality of N intolerance in epiphytic lichens. Meanwhile, the P content of five lichens increased slower than N content among N treatments, indicating the supply of P was deteriorated when the supply of N increased. The N addition also led to the N:P ratios of five lichens increased from about 10 to 20, and reached a maximum at 50 kg N ha?1 a?1, and the PME activity of the five lichen species was upregulated by the N addition, indicated that the balance between N and P was deteriorated in these lichens. We concluded that increases in N deposition will lead to nutrient imbalance in lichens and that nitrogen enrichment will change these five lichen species from being N limited to being P limited. Our research will be of value in the conservation of lichen diversity in the Shennongjia Nature Reserve (China).

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Longer conserved alpine forests ecosystem exhibits higher stability to climate change on the Tibetan Plateau
Jian Li, Nan Cong, Jiaxing Zu, Yuqin Xin, Ke Huang, Quan Zhou, Yaojie Liu, Lin Zhou, Li Wang, Yang Liu and Ge Zhang
J Plant Ecol    2019, 12 (4): 645-652.   DOI: 10.1093/jpe/rtz001
Online available: 08 January 2019

Abstract55)      PDF       Save
Aims

Vegetation dynamics are simultaneously regulated by climate change and anthropogenic activities. Since the 1980s, climate has been warming on the Tibetan Plateau (TP) at a rate higher than North Hemisphere average. Anthropogenic activities, including grazing, farming, and urbanization, are also influencing the alpine ecosystem on the TP. Especially, an ensemble of large engineering projects, such as power transported from west to east by State Grid, has been in operation on the TP. While studies disentangling effects of climate and anthropogenic activities interference are still lacking for the forest ecosystems on the TP. The overarching objectives of this study were to separate effects of natural climates and human interferences on forest ecosystem dynamics on the TP.

Methods

We compared vegetation activities of two typical natural reserves (Gongbu natural reserve, GNR, and Yarlung zangbo river grand canyon natural reserve, YNR) and their surroundings in southeastern Tibet (outside of the natural reserves, ONR) using long-term satellite normalized difference vegetation index (NDVI) dataset. Linear regression and partial correlation analyses were constructed for the relationship between vegetation activity and climates to evaluate the distinct climate effects on the two natural reserves.

Important Findings

The two natural reserves were established at different time, which were related to anthropogenic activities impact durations. The results showed that the annual mean NDVI fluctuated between 0.5 and 0.6 in the relatively longer reserved YNR, which was remarkably higher than those in other regions (with NDVI lower than 0.45). The vegetation vigor in the YNR showed neither a significant temporal trend nor significant relationship with climate. Nevertheless, vegetation vigor exhibited a significant increasing trend during the last three decades (0.012/decade) at the GNR. The inter-decadal analysis turned out positive relationships between vegetation vigor and annual temperature since late 1990s until early 2000s when the GNR was officially established. This study underlined the importance of considering human interference duration when assessing the relationships between vegetation dynamics and climates.

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Influence of smoke, heat and fire on germination of woody species occurring in the dry valleys of southwest China
Mareike Roeder, Weidong Yang and Kyle W. Tomlinson
J Plant Ecol    2019, 12 (6): 931-940.   DOI: 10.1093/jpe/rtz030
Abstract55)      PDF       Save
Aims

Savannahs depend on fire for their persistence. Fire influences regeneration from seeds in several ways: it converts the environment into a more open space which can benefit the establishment of seedlings, and fire itself can also enhance germination by chemical and physical cues, such as smoke and heat. There is limited information as to how seed of Asian savannah species respond to fire, even though Asia has several dry vegetation types that are associated with fire. Our main question was whether fire enhances or triggers the germination of woody species occurring in southwest Chinese dry valleys, which have savannah vegetation.

Methods

We conducted tests with heat (80°C) and smoke solution treatments, and tests with real fire by burning grass on top of sand trays containing seeds. We tested 35 species, including savannah species, and gully and forest species. Depending on seed availability, not all species were tested for all treatments. Twenty-six species had total germination >4% and these were used for analysis.

Important Findings

Heat increased germination of three species (strongest reaction: Dodonaea viscosa), smoke increased germination of five species (strongest reaction: Calotropis gigantea). Both treatments decreased germination for five and seven species, respectively. Real fire was detrimental for most species, except for D. viscosa, which is known to respond positively to heat shock. Even though fire-related cues were not a trigger for germination for most species in our study, fire could still be crucial for regeneration by competition release.

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The shift in the abundance of two Stipa species in response to land use change is associated with their divergent reproductive strategies
Xiaoshuai Wang, Frank Yonghong Li, Yuanheng Li, Xin Song, Xudong Guo, Xiangyang Hou and Taogetao Baoyin
J Plant Ecol    2019, 12 (4): 722-729.   DOI: 10.1093/jpe/rtz012
Online available: 04 January 2019

Abstract52)      PDF       Save
Aims

The divergent changes of plant species under land use changes are key mechanisms underlying vegetation succession. Stipa grandis steppe and Stipa krylovii steppe are two plant communities widely distributed on the Mongolian Plateau. They have been speculated to be able to succeed into each other under different land use types and intensities based on the observations on their presence and abundance at the sites with different land use history. However, no direct evidence, neither the underlying mechanisms, have been reported for this speculation. Here, we verified this speculation and explored the underlying mechanisms in the typical steppe region of Inner Mongolia.

Methods

We investigated the abundance and reproductive behavior of S. krylovii and S. grandis under different land use types and intensities. We used 18 grassland paddocks to run a 6-year experiment with 6 management treatments (T0—unused, T1—grazing monthly in plant growing season, T2, T4, T6—grazing in different months in plant growing season, and T8—mowing) replicated three times. We measured the relative density and cover of S. krylovii and S. grandis using line sampling method and examined their number and biomass of vegetative and reproductive tillers using quadrat method in each paddock after treatments for 4 and 6 years. We also determined these plant attributes in 14 pairs of heavily versus lightly used grassland plots in a wide area (150 km × 200 km) of the typical steppe region.

Important Findings

1. Grazing largely and mowing moderately decreased the density ratio and coverage ratio of S. grandis to S. krylovii in grasslands (P < 0.05), and the differences in these ratios between grazed and unused grasslands increased with time.

2. Grazing, but not mowing, significantly enhanced the relative density (Nrep = reproductive tiller number/total tiller number) of, and biomass allocation (Brep = reproductive tiller biomass/total biomass) to, reproductive tillers of S. krylovii (P < 0.05), but not S. grandis. This grazing enhancement to sexual reproduction of S. krylovii, and additionally inhibition to Nrep of S. grandis (P < 0.05), were found across the 14 pairs of heavily versus lightly used plots.

3. Seasonal pattern of grazing affected sexual reproduction of S. krylovii. The Nrep and Brep was higher under grazing in July and September (T4) than in July and August (T6) or in May and July (T2) (P < 0.05), suggesting a relatively positive effect of grazing on sexual reproduction in July (tasseling phenophase) than in May or August.

Our results provide direct evidence to the reciprocal change of S. grandis and S. krylovii in steppe communities under different management and indicate that gazing or mowing enhancement of sexual reproduction of S. krylovii relative to S. grandis is one of the mechanisms for the change.

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Indirect effect of nitrogen enrichment modified invertebrate herbivory through altering plant community composition in an alpine meadow
Fei Chen, Xiang Liu and Shurong Zhou
J Plant Ecol    2019, 12 (4): 693-702.   DOI: 10.1093/jpe/rtz003
Online available: 10 January 2019

Abstract51)            Save
Aims

Nitrogen enrichment may affect ‘community invertebrate herbivory’ (hereafter ‘herbivory’) directly by changing plant species’ specific herbivory, or indirectly by altering the composition of natural plant communities. Here, we investigated how community composition altered the community herbivory in natural ecosystems and compared the relative importance of direct and indirect effects of nitrogen addition on community herbivory.

Methods

We conducted a 7-year nitrogen addition experiment in an alpine meadow to evaluate the effects of fertilization on both herbivory frequency and severity, and we divided plants into four functional groups to investigate how changes in plant community functional composition affect community herbivory frequency. To separate the relative importance of direct and indirect effects of fertilization on community herbivory frequency, we build a serious of generalized models to select variables and used SEM methods to estimate relative contributions of the direct and indirect effects.

Important findings

We found that nitrogen addition increased community herbivory frequency, but not community herbivory severity in our 7-year nitrogen addition experiment. Although the most parsimonious model for explaining the variation in community herbivory frequency included fixed average of herbivory frequency and nitrogen addition, community fixed average of herbivory was the best single predictor for community herbivory frequency in our study. Changes in fixed average of herbivory frequency mediated by plant community composition (indirect effect) outperformed changes in species-specific herbivory frequency (direct effect) under fertilization in driving community herbivory frequency. Our research suggested that indirect effects caused by changes in plant community composition played a more important role in invertebrate herbivory under the condition of anthropogenic nitrogen enrichment.

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Soil resource availability and its effect on the ecophysiology and establishment of Stipa pulchra
Robert L. Fitch, Erin J. Questad and Edward G. Bobich
J Plant Ecol    2019, 12 (4): 603-614.   DOI: 10.1093/jpe/rty055
Online available: 20 December 2019

Abstract51)      PDF       Save
Aims

The objectives of this study were to (i) determine the importance of soil moisture and soil nitrogen availability as resource requirements for the establishment of Stipa pulchra, (ii) to examine how changes in slope within a local habitat can affect the accumulation of soil moisture and soil nitrogen and (iii) to measure the physiological responses of S. pulchra among such slope locations.

Methods

The field experiment occurred in the San José Hills of Southern California on the California State Polytechnic University, Pomona campus. Plots were established within three different slope locations (shallow, moderate and steep) within four separate canyons. Three nitrogen treatments (ambient, addition and removal) were replicated within each slope location for all four canyons, and five S. pulchra plants were planted in each plot. Soil nitrogen accumulation and soil moisture, as well as other abiotic variables, were measured across the varied slope locations and nitrogen treatments. We measured the cover, stress, and reproduction of S. pulchra plants for 2 years and used a mesocosm experiment to determine how S. pulchra responds to varying water and nitrogen availability.

Important Findings

Stipa pulchra had a strong positive response to the wettest watering treatment and a weak response to nitrogen addition in the mesocosm experiment. In the field experiment, S. pulchra responded positively in moderate slope locations and did not respond to nitrogen treatments, possibly due to drought. Field patterns of soil moisture were driven by slope, soil compaction and solar radiation. Soil nitrogen accumulation did not vary among slope locations. For restoration of S. pulchra, priority should be placed on managing soil moisture availability and determining suitable edaphic factors.

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Effects of physiological integration on defense strategies against herbivory by the clonal plant Alternanthera philoxeroides
Rubén Portela, Bi-Cheng Dong, Fei-Hai Yu, Rodolfo Barreiro and Sergio R. Roiloa
J Plant Ecol    2019, 12 (4): 662-672.   DOI: 10.1093/jpe/rtz004
Online available: 16 January 2019

Abstract51)      PDF       Save
Aims

The plant–herbivore interaction is one of the most fundamental interactions in nature. Plants are sessile organisms, and consequently rely on particular strategies to avoid or reduce the negative impact of herbivory. Here, we aimed to determine the defense strategies against insect herbivores in the creeping invasive plant Alternanthera philoxeroides.

Methods

We tested the defense response of A. philoxeroides to herbivory by a leaf-feeding specialist insect Agasicles hygrophila and a polyphagous sap-feeding insect Planococcus minor. We also tested the mechanisms triggering defense responses of A. philoxeroides by including treatments of artificial leaf removal and jasmonic acid application. Furthermore, we examined the effect of physiological integration on these defense strategies.

Important Findings

The combination of artificial leaf removal and jasmonic acid application produced a similar effect to that of leaf-feeding by the real herbivore. Physiological integration influenced the defense strategies of A. philoxeroides against herbivores, and increased biomass allocation to aboveground parts in its apical ramets damaged by real herbivores. Our study highlights the importance of physiological integration and modular plasticity for understanding the consequences of herbivory in clonal plants.

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Temperature and precipitation, but not geographic distance, explain genetic relatedness among populations in the perennial grass Festuca rubra
Maria Šurinová, Věroslava Hadincová, Vigdis Vandvik and Zuzana Münzbergová
J Plant Ecol    2019, 12 (4): 730-741.   DOI: 10.1093/jpe/rtz010
Online available: 07 March 2019

Abstract49)      PDF       Save
Aims

Knowledge of genetic structure of natural populations and its determinants may provide key insights into the ability of species to adapt to novel environments. In many genetic studies, the effects of climate could not be disentangled from the effects of geographic proximity. We aimed to understand the effects of temperature and moisture on genetic diversity of populations and separate these effects from the effects of geographic distance. We also wanted to explore the patterns of distribution of genetic diversity in the system and assess the degree of clonality within the populations. We also checked for possible genome size variation in the system.

Methods

We studied genetic variation within and among 12 populations of the dominant grass Festuca rubra distributed across a unique regional-scale climatic grid in western Norway, Europe and explored the importance of temperature, precipitation and geographic distance for the observed patterns. We also explored the distribution of genetic diversity within and among populations, identified population differentiation and estimated degree of clonality. The analyses used microsatellites as the genetic marker. The analyses were supplemented by flow cytometry of all the material.

Important Findings

All the material corresponds to hexaploid cytotype, indicating that ploidy variation does not play any role in the system. The results indicate that temperature and precipitation were better predictors of genetic relatedness of the populations than geographic distance, suggesting that temperature and precipitation may be important determinants of population differentiation. In addition, precipitation, alone and in interaction with temperature, strongly affected population genotypic diversity suggesting increased clonality towards the coldest and especially the coldest wettest climates. At the same time, individuals from the coldest and wettest climates also had the highest individual genetic diversity, suggesting that only the most heterozygous individuals survive under these harsh climates. Most of the genetic variation was distributed within populations, suggesting that most populations have sufficient genetic diversity to adapt to novel climatic conditions. The alpine populations, i.e. populations which are likely the most endangered by climate change, however, lack this potential due to the high levels of clonality as detected in our study.

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Protecting endemic seed plants on the Tibetan Plateau under future climate change: migration matters
Yujing Yan and Zhiyao Tang
J Plant Ecol    2019, 12 (6): 962-971.   DOI: 10.1093/jpe/rtz032
Abstract49)      PDF       Save
Aims

Climate change in the near future may become a major threat to high-altitude endemics by greatly altering their distribution. Our aims are to (i) assess the potential impacts of future climate change on the diversity and distribution of seed plants endemic to the Tibetan Plateau and (ii) evaluate the conservation effectiveness of the current National Nature Reserves (NNRs) in protecting the endemic plants in the face of climate change.

Methods

We projected range shifts of 993 endemic species to the years 2050 and 2070 under two representative concentration pathway scenarios using an ensemble species distribution modeling framework and evaluated range loss, species-richness change and coverage of the current conservation network considering two dispersal scenarios.

Important Findings

In a full-dispersal scenario, 72–81% of the species would expand their distribution by 2070, but 6–20% of the species would experience >30% range loss. Most species would shift to the west. The projected species net richness would increase across the region on average. In a no-dispersal scenario, 15–59% of the species would lose >30% of their current habitat by 2070. Severe species loss may occur in the southeastern and the eastern peripheral plateau. Seventeen percent of species ranges are covered by the NNRs on average and may increase in the future if species disperse freely. We found a significant difference of species redistribution patterns between different dispersal scenarios and highlighted the importance of migration in this region.

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Prickly pairs: the proportion of spinescent species does not differ between islands and mainlands
Floret L. Meredith, Marianne L. Tindall, Frank A. Hemmings and Angela T. Moles
J Plant Ecol    2019, 12 (6): 941-948.   DOI: 10.1093/jpe/rtz031
Abstract48)      PDF       Save
Aims

Organisms on islands are thought to escape biotic pressure and lose defensive capabilities. However, broadscale, evidence-based tests of this idea are rare. In this study, we asked: (i) whether the proportion of spinescent plant species differed between islands and mainlands and (ii) whether the proportion of spinescent species increased with increasing island area and with decreasing island distance to mainland.

Methods

We compiled species lists for 18 island–mainland pairs around Australia. We classified 1129 plant species as spinescent or non-spinescent using published species descriptions.

Important Findings

There was no significant difference between the proportion of spinescent species found on islands and on mainlands. Proportions of spinescent species were not significantly related to island area or distance to mainland. Our results suggest that spinescence is just as important to island plants as it is to mainland plants, even for plants inhabiting small or distal islands. This is unexpected, given prevailing thought and previous work on island–mainland comparisons. Our study demonstrates the importance of testing well-accepted yet untested ideas.

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Seed provenance determines germination responses of Rumex crispus (L.) under water stress and nutrient availability
María Pérez-Fernández, Carole P. Elliott, Alex Valentine and José Antonio Oyola
J Plant Ecol    2019, 12 (6): 949-961.   DOI: 10.1093/jpe/rtz034
Abstract42)      PDF       Save
Aims

Seeds of Rumex crispus from six provenances were studied in relation to their germination under drought and presence of nitrogen in the germination and emergence media. We also investigated whether adaptation to soil increases the ability of the species to colonize and establish in contrasting environments along a longitudinal gradient in western Spain by means of a reciprocal transplantation experiment.

Methods

We conducted a germination trial in the lab to test for the germination responses to water scarcity along a polyethylene glycol gradient and to varying concentrations of nitrogen compounds. Simultaneously reciprocal transplantations experiment was conducted, where seeds from six provenances were grown in the soils from the very same provenances. Seedling emergence, survivorship and fitness-related variables were measured in all plots.

Important Findings

We found that R. crispus has a cold-stratification requirement that enhances its germination. Significant differences between the six provenances were detected for time-to-germination, total seedling emergence, plant mortality and reproductive effort in all the experiments. The differences between provenances with respect to germination were confirmed by the significant statistical analyses of the variance, thus providing evidence that seeds from parent plants grown in different environmental conditions have an intrinsically different abilities to germinate and establish. Soil nitrogen content where seed germination and seedlings establish also play an important role in their performance in terms of survivorship and reproduction, being the higher levels of inorganic nitrogen and of microbial biomass those that increased biomass production, enhanced inflorescence formation and reduced plant mortality. We conclude that one of the main reasons for the spread and maintenance of R. crispus would be the increased levels of nitrogen in agricultural soils.

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Seasonal distribution of increased precipitation in maternal environments influences offspring performance of Potentilla tanacetifolia in a temperate steppe ecosystem
Yang Li, Longyu Hou, Bing Song, Shiqiang Wan, Xiaoqin Sun and Linghao Li
J Plant Ecol    2019, 12 (4): 742-750.   DOI: 10.1093/jpe/rtz011
Online available: 27 February 2019

Abstract42)      PDF       Save
Aims

Precipitation is predicted to increase in arid and semiarid regions under climate change, with greater changes in intra- and inter-annual distribution in the future. As a major limiting factor in these regions, changes in precipitation undoubtedly influence plant growth and productivity. However, how the temporal shifts in precipitation will impact plant populations are uncertain.

Methods

A 3-year field experiment and a greenhouse experiment were conducted in a temperate grassland in northern China to examine the impacts of seasonal (spring and summer) increased precipitation on offspring performance of a common species, Potentilla tanacetifolia.

Important Findings

Our results showed that the amounts and timing of increased precipitation both played important roles in regulating offspring performance of P. tanacetifolia in the temperate steppe ecosystem. Increased precipitation in spring at maternal stage stimulated seed production, germination percentage and seedling biomass, whereas increased precipitation in summer at maternal stage stimulated seedling biomass. The timing of increased precipitation influenced seed attributes, whereas the amount of increased precipitation influenced offspring seedling biomass. Our results indicate that population development of P. tanacetifolia may be underestimated under future increased precipitation regime, if the transgenerational effect is not taken into account.

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Hydrologic balance, net primary productivity and water use efficiency of the introduced exotic Eucalyptus grandis × Eucalyptus urophylla plantation in south-western China
Yanting Hu, Ping Zhao, Yuqing Huang, Liwei Zhu, Guangyan Ni, Xiuhua Zhao and Zhihong Huang
J Plant Ecol    2019, 12 (6): 982-992.   DOI: 10.1093/jpe/rtz033
Abstract42)      PDF       Save
Aims

Land cover changes can disrupt water balance and alter the partitioning of precipitation into surface runoff, evapotranspiration and groundwater recharge. The widely planted Eucalyptustrees in south-western China have the potential to bring about hydrologic impacts. Our research aims to elucidate the hydrologic balance characteristics of the introduced exotic Eucalyptus grandis× Eucalyptus urophylla plantation and to assess whether its high productivity results from high water use efficiency (WUE) or large water consumption.

Methods

A 400-m2 experimental plot was established in an E. grandis × E. urophylla plantation in south-western China. Water balance components, including stand transpiration (Tr), evapotranspiration (Et) and runoff (R) were obtained as follows: Tr was estimated based on sap flow measurements, Et was estimated as the average of surface transpiration and evaporation weighted by the fractional green vegetation cover using a modeling approach, and R was collected using the installed metal frame. Net primary productivity (NPP) was obtained from allometric equation and annual diameter at breast height (DBH) increment determination.

Important Findings

Annual Et and Tr were 430 ± 31 and 239 ± 17 mm, respectively. Annual Traccounts for 56 ± 8% of total evapotranspiration on average. WUE (NPP/Tr) of the E. grandis × E. urophylla was estimated to be 3.3–3.9 mmol·mol−1. Based on the comparative analysis of Tr and WUE, E. grandis × E. urophylla had a high productivity due to its high WUE without exhibiting prodigal water use. Meteorological factors including vapor pressure deficit and global solar radiation (Rs) were key factors regulating Et and Tr in our research site. Annual surface runoff, Etand canopy interception occupied 7%, 27–30% and 16% of total precipitation, while the remaining 46–50% of precipitation was used for sustaining groundwater recharge and altering soil water storage. The higher runoff coefficient (7.1%) indicated the weaker capability of E. grandis × E. urophylla to reserve water resource than natural forests and less disturbed plantations. The planting and protection of understory vegetation may decrease the surface runoff and exert beneficial effects on water conservation capacity of Eucalyptus plantation.

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Impacts of nitrogen deposition on terrestrial plant diversity: a meta-analysis in China
Wen-Juan Han, Jia-Yu Cao, Jin-Liang Liu, Jia Jiang and Jian Ni
J Plant Ecol    2019, 12 (6): 1025-1033.   DOI: 10.1093/jpe/rtz036
Abstract40)      PDF       Save
Aims

With the global atmospheric nitrogen (N) deposition increasing, the effect of N deposition on terrestrial plant diversity has been widely studied. Some studies have reviewed the effects of N deposition on plant species diversity; however, all studies addressed the effects of N deposition on plant community focused on species richness in specific ecosystem. There is a need for a systematic meta-analysis covering multiple dimensions of plant diversity in multiple climate zones and ecosystems types. Our goal was to quantify changes in species richness, evenness and uncertainty in plant communities in response to N addition across different environmental and experimental contexts.

Methods

We performed a meta-analysis of 623 experimental records published in English and Chinese journals to evaluate the response of terrestrial plant diversity to the experimental N addition in China. Three metrics were used to quantify the change in plant diversity: species richness (SR), evenness (Pielou index) uncertainty (Shannon index).

Important Findings

Results showed that (i) N addition negatively affected SR in temperate, Plateau zones and subtropical zone, but had no significant effect on Shannon index in subtropical zones; (ii) N addition decreased SR, Shannon index and Pielou index in grassland, and the negative effect of N addition on SR was stronger in forest than in grassland; (iii) N addition negatively affected plant diversity (SR, Shannon index and Pielou index) in the long term, whereas it did not affect plant diversity in the short term. Furthermore, the increase in N addition levels strengthened the negative effect of N deposition on plant diversity with long experiment duration; and (iv) the negative effect of ammonium nitrate (NH4NO3) addition on SR was stronger than that of urea (CO(NH2)2) addition, but the negative effect of NH4NO3 addition on Pielou index was weaker than that of CO(NH2)2 addition. Our results indicated that the effects of N addition on plant diversity varied depending on climate zones, ecosystem types, N addition levels, N type and experiment duration. This underlines the importance of integrating multiple dimensions of plant diversity and multiple factors into assessments of plant diversity to global environmental change.

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Traits uncover quasi-neutral community assembly in a coastal heath vegetation
José Luiz Alves Silva, Alexandre Fadigas Souza and Louis Stephen Santiago
J Plant Ecol    2019, 12 (4): 703-712.   DOI: 10.1093/jpe/rtz007
Online available: 23 January 2019

Abstract40)      PDF       Save
Aims

Trait-based approaches are increasingly being used in ecology due to their potential to explain and predict community structure and dynamic regardless of species identities. Here, we asked whether coastal heath vegetation established in stressful habitats could be assembled by quasi-neutral mechanisms based on functional trait distribution. Communities are organized through quasi-neutral dynamics if abiotic gradients and/or species interactions impose sorting on functional traits and species performances, but not on species phylogenetic relatedness and occurrence.

Methods

The study was conducted in a coastal area containing tall dunes near the sea, and relatively flat areas punctuated by short palaeodunes further inland, Northeastern South America. We evaluated 10 traits of the 21 most abundant species, as well as eight abiotic variables in 70 plots (25?m2) established in dune tops, valleys, flat and steep microenvironments. The effect of environmental filter was tested by linear mixed models (LMM) between each community-weighted mean (CWM) trait and the abiotic variables, and by two indices of environmental filtering based on intra- and interspecific-trait variability relative to null models. To evaluate the effect of species interactions, we used an index of niche overlap relative to null models, and LMMs between this index and the species richness of plots.

Important Findings

The environmental filtering index did not deviate from null expectations for any trait. Models that included individual variability performed similarly to models that used species mean traits. However, the explicit consideration of environmental gradients by CWM analyses revealed functional patterns that would remain undetected if trait distribution was analyzed only. In addition, intraspecific variation in the stem length was an important driver of species diversity as suggested by the relationship between species richness and the niche overlap index. Based on the occurrence and phylogenetic relatedness of species, previous work in the same system found neutral community assembly. We concluded that to ignore functional traits may lead to underestimations of niche-based processes, and that analyses of species occurrence and phylogenetic relatedness should be complemented with functional traits to reinforce our interpretation of processes underpinning community assembly. In this regard, the study heath vegetation is influenced by quasi-neutral effects on functional trait distribution.

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Root production, mortality and turnover in soil profiles as affected by clipping in a temperate grassland on the Loess Plateau
Lin Wei, Pengwei Yao, Guanghua Jing, Xiefeng Ye and Jimin Cheng
J Plant Ecol    2019, 12 (6): 1059-1072.   DOI: 10.1093/jpe/rtz039
Abstract39)      PDF       Save
Aims

Clipping or mowing for hay, as a prevalent land-use practice, is considered to be an important component of global change. Root production and turnover in response to clipping have great implications for the plant survival strategy and grassland ecosystem carbon processes. However, our knowledge about the clipping effect on root dynamics is mainly based on root living biomass, and limited by the lack of spatial and temporal observations. The study aim was to investigate the effect of clipping on seasonal variations in root length production and mortality and their distribution patterns in different soil layers in semiarid grassland on the Loess Plateau.

Methods

Clipping was performed once a year in June to mimic the local spring livestock grazing beginning from 2014. The minirhizotron technique was used to monitor the root production, mortality and turnover rate at various soil depths (0–10, 10–20, 20–30 and 30–50 cm) in 2014 (from 30 May to 29 October) and 2015 (from 22 April to 25 October). Soil temperature and moisture in different soil layers were also measured during the study period.

Important Findings

Our results showed that: (i) Clipping significantly decreased the cumulative root production (P < 0.05) and increased the cumulative root mortality and turnover rates of the 0–50 cm soil profile for both years. (ii) Clipping induced an immediate and sharp decrease in root length production and an increase in root length mortality in all soil layers. However, with plant regrowth, root production increased and root mortality decreased gradually, with the root production at a depth of 30–50 cm even exceeding the control in September–October 2014 and April–May 2015. (iii) Clipping mainly reduced root length production and increased root length mortality in the upper 0–20 cm soil profile with rapid root turnover. However, roots at deeper soil layers were either little influenced by clipping or exhibited an opposite trend with slower turnover rate compared with the upper soil profile, leading to the downward transport of root production and living root biomass. These findings indicate that roots in deeper soil layers tend to favour higher root biomass and longer fine root life spans to maximize the water absorption efficiency under environmental stress, and also suggest that short-term clipping would reduce the amount of carbon through fine root litter into the soil, especially in the shallow soil profile.

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Differences in physiological integration between invasive and noninvasive introduced clonal species of Carpobrotus
Sergio R. Roiloa, Peter Alpert and Rodolfo Barreiro
J Plant Ecol    2019, 12 (6): 972-981.   DOI: 10.1093/jpe/rtz035
Abstract39)      PDF       Save
Aims

Clonal growth is associated with invasiveness in introduced plant species, but few studies have compared invasive and noninvasive introduced clonal species to investigate which clonal traits may underlie invasiveness. To test the hypothesis that greater capacity to increase clonal growth via physiological integration of connected ramets increases invasiveness in clonal plants, we compared the effects of severing connections on accumulation of mass in the two species of the creeping, succulent, perennial, herbaceous genus Carpobrotus that have been introduced on sand dunes along the Pacific Coast of northern California, the highly invasive species Carpobrotus edulis and the co-occurring, noninvasive species Carpobrotus chilensis.

Methods

Pairs of ramets from four mixed populations of the species from California were grown in a common garden for 3 months with and without severing the stem connecting the ramets. To simulate the effect of clones on soils in natural populations, the older ramet was grown in sand amended with potting compost and the younger in sand alone.

Important Findings

Severance decreased net growth in mass by ~60% in C. edulis and ~100% in C. chilensis, due mainly to the negative effect of severance on the shoot mass of the younger ramet within a pair. Contrary to the hypothesis, this suggests that physiological integration increases growth more in the less invasive species. However, severance also decreased allocation of mass to roots in the older ramet and increased it in the younger ramet in a pair, and the effect on the younger ramet was about twice as great in C. edulis as in C. chilensis. This indicates that the more invasive species shows greater phenotypic plasticity in response to physiological integration, in particular greater capacity for division of labor. This could contribute to greater long-term growth and suggests that the division of labor may be a trait that underlies the association between clonal growth and invasiveness in plants.

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Genetic diversity and offspring fitness in the red and white fruit color morphs of the wild strawberry Fragaria pentaphylla
Lu-Xi Chen, Su-Ting Xu, Wei-Hang Ding, Jun-Min Li and Peter Alpert
J Plant Ecol    2020, 13 (1): 36-41.   DOI: 10.1093/jpe/rtz054
Online available: 07 December 2019

Abstract38)      PDF       Save
Aims

Fruit color polymorphisms are widespread in plants, but what maintains them is largely unclear. One hypothesis is that some morphs are preferred by dispersers while others have higher pre- or postdispersal fitness. This leads to the prediction that fruit color morphs will differ in pre- or postdispersal fitness.

Methods

We compared genetic and clonal diversity, mating system, morphological traits that might be associated with resistance to freezing, and germination, survival and seed production of progeny of the red and white fruit morphs in a population of a diploid, wild strawberry, Fragaria pentaphylla, from south-central China.

Important Findings

The red morph was much more abundant than the white but did not show higher genetic diversity as measured by observed and effective numbers of alleles, Shannon information index, or expected or observed heterozygosities. AMOVA showed that most of the genetic variation in the population was within rather than between morphs. Morphs did not differ in mating system parameters, and no significant biparental inbreeding was found in either morph. Gene flow between two morphs was high (Nm = 6.89). Seeds of the red morph germinated about 2 days earlier and had a 40% higher rate of germination than those of the white morph, but survival of seedlings and seed production by surviving offspring did not differ between morphs. The whole postdispersal fitness of the red morph was about two times higher than that of the white morph. Red morphs had hairier petioles but not more surface wax on leaves. Overall, results showed partial evidence for difference in pre- and postdispersal fitness between fruit color morphs in F. pentaphylla. Differences in fitness independent of dispersal may thus partially account for fruit color polymorphism in all cases.

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Elevational patterns of carbon, nitrogen and phosphorus in understory bryophytes on the eastern slope of Gongga Mountain, China
Zhe Wang, Chunyan Pi, Xiaoming Li and Weikai Bao
J Plant Ecol    2019, 12 (4): 781-786.   DOI: 10.1093/jpe/rtz008
Online available: 13 February 2019

Abstract38)      PDF       Save
Aims

The nutrient uptake, requirement and releasing rates of bryophytes are very different from those of tracheophytes. However, it is difficult to make a quantitative evaluation of bryophytes’ roles in nutrient cycling and their specific eco-physiological adaptations due to lack of knowledge of their concentrations and stoichiometric ratios of carbon (C), nitrogen (N) and phosphorus (P). To fill this gap, the present study aims to investigate: (i) what are the elevational trends of C, N and P concentrations and stoichiometric ratios of bryophytes? (ii) whether C, N and P concentrations and stoichiometric ratios of bryophytes differ between different bryophyte types (in terms of the growth form and living substrate)? and (iii) how do the exponent scalings of N and P of bryophytes change along the elevational gradient?

Methods

We measured and calculated the C, N, P concentrations and stoichiometric ratios of bryophytes from four elevations on the eastern slope of Gongga Mountain (22 species in total). Differences in these traits among elevations, and between different bryophyte types were compared. The log-log allometric regression parameters of N and P at each elevation were also determined and compared.

Important Findings

The C, N and P concentrations of bryophytes showed decreasing trends with increasing elevations. More specifically, erect bryophytes possessed higher C and N concentrations than those of prostrate species, and terricolous species had higher P concentration than that of corticolous and saxicolous species. Bryophytes from different elevations had an invariant allometric regression slope for P versus N. Future research at a larger scale is in need for a more generalized law of bryophytes.

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Strong restrictions on the trait range of co-occurring species in the newly created riparian zone of the Three Gorges Reservoir Area, China
Aiying Zhang, Will Cornwell, Zhaojia Li, Gaoming Xiong, Dayong Fan and Zongqiang Xie
J Plant Ecol    2019, 12 (5): 825-833.   DOI: 10.1093/jpe/rtz016
Abstract37)      PDF       Save
Aims

Community assembly links plant traits to particular environmental conditions. Numerous studies have adopted a trait-based approach to understand both community assembly processes and changes in plant functional traits along environmental gradients. In most cases these are long-established, natural or semi-natural environments. However, increasingly human activity has created, and continues to create, a range of new environmental conditions, and understanding community assembly in these ‘novel environments’ will be increasingly important.

Methods

Built in 2006, the Three Gorges Dam, largest hydraulic project in China, created a new riparian area of 384 km2, with massively altered hydrology. This large, newly created ecosystem is an ideal platform for understanding community assembly in a novel environment. We sampled environment variables and plant communities within 103 plots located in both the reservoir riparian zone (RRZ) and adjacent non-flooded and semi-natural upland (Upland) at the Three Gorges Reservoir Area. We measured six traits from 168 plant species in order to calculate community-level distribution of trait values. We expected that the altered hydrology in RRZ would have a profound effect on the community assembly process for the local plants.

Important Findings

Consistent with previous work on community assembly, the distribution of trait values (range, variance, kurtosis and the standard deviation of the distribution neighbor distances) within all plots was significantly lower than those from random distributions, indicating that both habitat filtering and limiting similarity simultaneously shaped the distributions of traits and the assembly of plant communities. Considering the newly created RRZ relative to nearby sites, community assembly was different in two main ways. First, there was a large shift in the mean trait values. Compared to Upland communities, plant communities in the RRZ had higher mean specific leaf area (SLA), higher nitrogen per unit leaf mass (Nmass), and lower maximum height (MH). Second, in the RRZ compared to the Upland, for the percentage of individual plots whose characteristic of trait values was lower than null distributions, the reductions in the community-level range for SLA, Nmass, nitrogen per unit leaf area (Narea) and phosphorus per unit leaf area (Parea) were much larger, suggesting that the habitat filter in this newly created riparian zone was much stronger compared to longer established semi-natural upland vegetation. This stronger filter, and the restriction to a subset of plants with very similar trait values, has implications for predicting riparian ecosystems’ responses to the hydrological alterations and further understanding for human’s effect on plant diversity and plant floras.

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Elevated nitrogen deposition may advance invasive weed, Solidago canadensis, in calcareous soils
Ling-Yun Wan, Shan-Shan Qi, Chris B. Zou, Zhi-Cong Dai, Guang-Qian Ren, Qi Chen, Bin Zhu and Dao-Lin Du
J Plant Ecol    2019, 12 (5): 846-856.   DOI: 10.1093/jpe/rtz019
Abstract37)      PDF       Save
Aims

Change in nitrogen (N) availability regulates phosphorus (P) acquisition and potentially alters the competition among native species and invasive weeds. This study determines how current and projected N deposition affect the growth, the intraspecific and interspecific competitive ability of native and invasive plants in calcareous soils with low P availability.

Methods

A controlled greenhouse experiment was conducted using sparingly soluble hydroxyapatite (HAP) to simulate the calcareous soils with low P availability. The growth and competitive intensity between an invasive weed (Solidago canadensis) and a native weed (Pterocypsela laciniata) exposed to two levels of N addition representative of current and future N deposition in China were experimentally determined.

Important Findings

P acquisition and the growth of both S. canadensis and P. laciniata growing alone significantly increased with increasing N level. However, the effect of N addition was reduced when intraspecific or interspecific competition existed. N addition altered the competitive relationship between S. canadensis and P. laciniata allowing S. canadensisto out-compete P. laciniata due to variation in P acquisition from HAP. Elevated N deposition might assist the invasion of S. canadensis in the widely distributed calcareous soils under environmental changes.

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Effects of environmental conditions and space on species turnover for three plant functional groups in Brazilian savannas
Hélio Menegat, Divino Vicente Silvério, Henrique A. Mews, Guarino R. Colli, Ana Clara Abadia, Leonardo Maracahipes-Santos, Lorrayne A. Gonçalves, Jhany Martins and Eddie Lenza
J Plant Ecol    2019, 12 (6): 1047-1058.   DOI: 10.1093/jpe/rty054
Abstract37)      PDF       Save
Aims

Different plant functional groups display diverging responses to the same environmental gradients. Here, we assess the effects of environmental and spatial predictors on species turnover of three functional groups of Brazilian savannas (Cerrado) plants—trees, palms and lianas—across the transition zone between the Cerrado and Amazon biomes in central Brazil.

Methods

We used edaphic, climatic and plant composition data from nine one-hectare plots to assess the effects of the environment and space on species turnover using a Redundancy Analysis and Generalized Dissimilarity Modeling (GDM), associated with variance partitioning.

Important Findings

We recorded 167 tree species, 5 palms and 4 liana species. Environmental variation was most important in explaining species turnover, relative to geographic distance, but the best predictors differed between functional groups: geographic distance and silt for lianas; silt for palms; geographic distance, temperature and elevation for trees. Geographic distances alone exerted little influence over species turnover for the three functional groups. The pure environmental variation explained most of the liana and palm turnover, while tree turnover was largely explained by the shared spatial and environmental contribution. The effects of geographic distance upon species turnover leveled off at about 300 km for trees, and 200 km for lianas, whereas they were unimportant for palm species turnover. Our results indicate that environmental factors that determine floristic composition and species turnover differ substantially between plant functional groups in savannas. Therefore, we recommend that studies that aim to investigate the role of environmental conditions in determining plant species turnover should examine plant functional groups separately.

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The role of shaded cocoa plantations in the maintenance of epiphytic orchids and their interactions with phorophytes
Jonas Morales-Linares, José G. García-Franco, Alejandro Flores-Palacios, Thorsten Krömer and Tarin Toledo-Aceves
J Plant Ecol    2020, 13 (1): 27-35.   DOI: 10.1093/jpe/rtz052
Online available: 20 November 2019

Abstract36)      PDF       Save
Aims

Habitat loss and fragmentation are the main threats to biodiversity in tropical forests. Agroecosystems such as shaded cocoa plantations (SCP) provide refuge for tropical forest biota. However, it is poorly known whether the interspecific ecological interactions are also maintained in these transformed habitats. We evaluated the diversity, reproductive status and photosynthetic metabolism (CAM or C3) of the epiphytic orchid community, and their interactions with host trees (phorophytes) in SCP compared to tropical rainforest (TRF).

Methods

In southeastern Mexico, three sites each in TRF and SCP were studied, with four 400 m2 plots established at each site to record all orchids and their phorophytes. We determined the reproductive (adult) or non-reproductive (juvenile) status of each orchid individual in relation to the presence or absence, respectively, of flowers/fruits (or remnants), and assigned the photosynthetic pathway of each orchid species based in literature. We used true diversity and ecological networks approaches to analyze orchid diversity and orchid–phorophyte interactions, respectively.

Important Findings

In total, 607 individuals belonging to 47 orchid species were recorded. Orchid diversity was higher in TRF (19 effective species) than in SCP (11 effective species) and only seven species were shared between the two habitats. CAM orchid species were more frequent in SCP (53%) than in TRF (14%). At the community level the proportion of non-reproductive and reproductive orchid species and the nested structure and specialization level of the TRF orchid–phorophyte network were maintained in SCP. However, only a subset of TRF epiphytic orchids remains in SCP, highlighting the importance of protecting TRF. Despite this difference, shaded agroecosystems such as SCP can maintain some of the diversity and functions of natural forests, since the SCP epiphytic orchid community, mainly composed of CAM species, and its phorophytes constitute a nested interaction network, which would confer robustness to disturbances.

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Impact Factor
1.833
5 year Impact Factor
2.299
Editors-in-Chief
Wen-Hao Zhang
Bernhard Schmid