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Are extrafloral nectaries efficient against herbivores? Herbivory and plant defenses in contrasting tropical species
Cássio Cardoso Pereira, Maria Gabriela Boaventura, Gislene Carvalho de Castro and Tatiana Cornelissen
J Plant Ecol    2020, 13 (4): 423-430.   DOI: 10.1093/jpe/rtaa029
Online available: 31 May 2020

Abstract11)      PDF       Save
Aims

Plants have limited resources for defenses and species that invest in biotic defenses might exhibit leaves that invest less in other types of defenses. We have investigated whether plants that have few mechanical defenses, but have extrafloral nectaries (EFNs) patrolled by ants, are less prone to herbivory, compared with plants without EFNs that have tougher leaves.

Methods

Data from the literature were extracted to examine the reported levels of herbivory in plants with or without EFNs. In a savanna vegetation in southern Brazil, field data were collected in leaves from six tropical species and herbivory and specific leaf area (SLA) levels were measured. We further evaluated differences in herbivory and SLA among species and between plants with or without EFNs. In order to test the relationship between herbivory and leaf toughness we regressed average herbivory and average SLA per plant.

Important Findings

Plants exhibited variable levels of leaf damage, but plants without ant defenses experienced the highest levels of leaf area loss to herbivory. Levels of mechanical defenses were also variable among the plant species. Plants without EFNs were tougher, exhibiting lower values of SLA. Although plants without EFNs had more sclerophyllous leaves, this mechanical defense was not sufficient to impair and/or reduce herbivore feeding, suggesting that the biotic defenses performed by patrolling ants might be more effective than investment in mechanical defenses associated with leaf palatability.

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A sweet new study: tropical forest species use nonstructural carbohydrates in different ways during drought
Jennifer S. Powers
J Plant Ecol    2020, 13 (4): 387-388.   DOI: 10.1093/jpe/rtaa020
Online available: 27 May 2020

Abstract50)      PDF       Save
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The ultraviolet colour component enhances the attractiveness of red flowers of a bee-pollinated plant
Zhe Chen, Chang-Qiu Liu, Hang Sun and Yang Niu
J Plant Ecol    2020, 13 (3): 354-360.   DOI: 10.1093/jpe/rtaa023
Online available: 25 May 2020

Abstract39)      PDF       Save
Aims

Bee-pollinated flowers are rarely red, presumably because bees (which lack red receptors) have difficulty detecting red targets. Although the response of bees to red colour has been investigated in lab experiments, most stimuli have been pure red, while the subtle diversity of red as perceived by humans (human-red) has received very limited attention. Here we test the hypothesis that ultraviolet (UV) reflected from human-red flowers enhances their attractiveness to bees, through increased chromatic contrast.

Methods

Using Onosma confertum (Boraginaceae), a plant with UV-reflecting red flowers that are pollinated by bumblebees, we investigated the effects of UV reflection on pollinator responses by conducting phenotypic manipulation experiments in the field. Colour preferences of flower-naïve bumblebees were also examined. Colour perception by bumblebees was estimated in terms of chromatic and achromatic contrast, based on two different colour perception models.

Important Findings

We found that both natural and flower-naïve bumblebees strongly preferred visiting UV-reflecting targets compared with UV-absorbing ones. Colour models show that the UV-reflecting flowers exhibit higher spectral purity and higher chromatic contrast against the foliage background, whereas they have similar achromatic contrast in terms of green receptor contrast. These results indicate that the component of UV reflection increases chromatic contrast in O. confertum, enhancing the visual attractiveness of these red flowers to bumblebees. We further infer that the secondary reflectance might be a necessary component in human-red flowers that are primarily pollinated by animals without red receptors, such as bees.

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The role of soluble sugars during drought in tropical tree seedlings with contrasting tolerances
Michael J. O’Brien, Annabelle Valtat, Samuel Abiven, Mirjam S. Studer, Robert Ong and Bernhard Schmid
J Plant Ecol    2020, 13 (4): 389-397.   DOI: 10.1093/jpe/rtaa017
Online available: 13 April 2020

Abstract54)      PDF       Save
Aims

Non-structural carbohydrates (NSCs) are plant storage compounds used for metabolism, transport, osmoregulation and regrowth following the loss of plant tissue. Even in conditions suitable for optimal growth, plants continue to store NSCs. This storage may be due to passive accumulation from sink-inhibited growth or active reserves that come at the expense of growth. The former pathway implies that NSCs may be a by-product of sink limitation, while the latter suggests a functional role of NSCs for use during poor conditions.

Methods

Using 13C pulse labelling, we traced the source of soluble sugars in stem and root organs during drought and everwet conditions for seedlings of two tropical tree species that differ in drought tolerance to estimate the relative allocation of NSCs stored prior to drought versus NSCs assimilated during drought. We monitored growth, stomatal conductance, stem water potential and NSC storage to assess a broad carbon response to drought.

Important Findings

We found that the drought-sensitive species had reduced growth, conserved NSC concentrations in leaf, stem and root organs and had a larger proportion of soluble sugars in stem and root organs that originated from pre-drought storage relative to seedlings in control conditions. In contrast, the drought-tolerant species maintained growth and stem and root NSC concentrations but had reduced leaf NSCs concentrations with a larger proportion of stem and root soluble sugars originated from freshly assimilated photosynthates relative to control seedlings. These results suggest the drought-sensitive species passively accumulated NSCs during water deficit due to growth inhibition, while the drought-tolerant species actively responded to water deficit by allocating NSCs to stem and root organs. These strategies seem correlated with baseline maximum growth rates, which supports previous research suggesting a trade-off between growth and drought tolerance while providing new evidence for the importance of plasticity in NSC allocation during drought.

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Soil nitrogen availability intensifies negative density-dependent effects in a subtropical forest
Fengmin Huang, Minxia Liang, Yi Zheng, Xubing Liu, Yuxin Chen, Wenbin Li, Shan Luo and Shixiao Yu
J Plant Ecol    2020, 13 (3): 281-287.   DOI: 10.1093/jpe/rtaa012
Online available: 21 March 2020

Abstract45)      PDF       Save
Aims

The importance of density-dependent mortality in maintaining tree species diversity is widely accepted. However, density-dependent effects may vary in magnitude and direction with different abiotic conditions in forests. Theoretical predictions surmise that density-dependent effects may vary with soil available nitrogen (AN), but this still needs to be tested.

Methods

We analyzed the density-dependent effects on survival of newly germinated seedlings for 18 common species based on a long-term seedling census across environmental gradients in a subtropical forest. We also conducted a root lesion detection experiment for five species to investigate the potential effects of pathogens on variation in density-dependent disease between rich and poor AN environments.

Important Findings

The seedling dynamics analysis revealed that the strength of density-dependent effects increased with AN, shifting from neutral or positive with low AN to negative with high AN. Three of the five tree species had stronger density-dependent effects on root lesions in rich AN environments than in poor AN environments, which is consistent with the results of a long-term seedling dynamics analysis. We also found higher species diversity in rich AN environments, which may be promoted by the stronger negative density-dependent effects. Both the seedling dynamic analysis and root lesion detection experiment revealed stronger negative density-dependent effects in higher AN environment, resulting from stronger disease pressure by soil pathogens. Our study emphasized the importance of considering context dependence when testing the density dependence hypotheses.

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Woody plant encroachment may decrease plant carbon storage in grasslands under future drier conditions
Yun-Hua Liu, Jun-Hui Cheng, Bernhard Schmid, Li-Song Tang and Jian-Dong Sheng
J Plant Ecol    2020, 13 (2): 213-223.   DOI: 10.1093/jpe/rtaa003
Online available: 23 January 2020

Abstract53)      PDF       Save
Aims

Woody plants are widely distributed in various grassland types along the altitudinal/climatic gradients in Xinjiang, China. Considering previously reported change in carbon (C) storage following woody plant encroachment in grasslands and the mediating effect of climate on this change, we predicted that a positive effect of woody plants on plant C storage in semiarid grasslands may revert to a negative effect in arid grasslands. We first investigated the spatial variation of aboveground C (AGC) and belowground C (BGC) storage among grassland types and then tested our prediction.

Methods

We measured the living AGC storage, litter C (LC) and BGC storage of plants in two physiognomic types, wooded grasslands (aboveground biomass of woody plants at least 50%) and pure grasslands without woody plants in six grassland types representing a gradient form semiarid to arid conditions across Xinjiang.

Important Findings Living AGC, LC, BGC and total plant C storage increased from desert to mountain meadows. These increases could also be explained by increasing mean annual precipitation (MAP) or decreasing mean annual temperature (MAT), suggesting that grassland types indeed represented an aridity gradient. Woody plants had an effect on the plant C storage both in size and in distribution relative to pure grasslands. The direction and strength of the effect of woody plants varied with grassland types due to the mediating effect of the climate, with wetter conditions promoting a positive effect of woody plants. Woody plants increased vegetation-level AGC through their high AGC relative to herbaceous plants. However, more negative effects of woody plants on herbaceous plants with increasing aridity led to a weaker increase in the living AGC in arid desert, steppe desert and desert steppe than in the less arid other grassland types. Under greater aridity (lower MAP and higher MAT), woody plants allocated less biomass to roots and had lower BGC and had a more negative impact on herbaceous plant production, thereby reducing vegetation-level BGC in the desert, steppe desert and desert steppe. In sum, this resulted in a negative effect of woody plants on total plant C storage in the most arid grasslands in Xinjiang. As a consequence, we predict that woody plant encroachment may decrease rather than increase C storage in grasslands under future drier conditions.

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Changes in niche differentiation and environmental filtering over a hydric stress gradient
Alejandra Martínez-Blancas, and Carlos Martorell
J Plant Ecol    2020, 13 (2): 185-194.   DOI: 10.1093/jpe/rtz061
Online available: 10 January 2020

Abstract82)      PDF       Save
Aims

Diversity in communities is determined by species’ ability to coexist with each other and to overcome environmental stress that may act as an environmental filter. Niche differentiation (ND) results in stronger intra- than interspecific competition and promotes coexistence. Because stress affects interactions, the strength of ND may change along stress gradients. A greater diversity of plant growth forms has been observed in stressful habitats, such as deserts and alpine regions, suggesting greater ND when stress is strong. We tested the hypothesis that niche differences and environmental filters become stronger with stress.

Methods

In a semiarid grassland in southern Mexico, we sowed six annual species in the field along a hydric stress gradient. Plants were grown alone (without interactions), with conspecific neighbors (intraspecific interactions) or with heterospecific neighbors (interspecific interactions). We analyzed how the ratio of intra- to interspecific competition changed along the gradient to assess how water availability determines the strength of ND. We also determined if hydric stress represented an environmental filter.

Important Findings

We observed stronger intra- than interspecific competition, especially where hydric stress was greater. Thus, we found ND in at least some portion of the gradient for all but one species. Some species were hindered by stress, but others were favored by it perhaps because it eliminates soil pathogens. Although strong ND was slightly more frequent with stress, our species sample was small and there were exceptions to the general pattern, so further research is needed to establish if this is a widespread phenomenon in nature.

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Changes in carbon storages of Fagus forest ecosystems along an elevational gradient on Mt. Fanjingshan in Southwest China
Qiong Cai, Chengjun Ji, Xuli Zhou, Helge Bruelheide, Wenjing Fang, Tianli Zheng, Jiangling Zhu, Lei Shi, Haibo Li, Jianxiao Zhu and Jingyun Fang
J Plant Ecol    2020, 13 (2): 139-149.   DOI: 10.1093/jpe/rtz055
Online available: 16 December 2019

Abstract67)      PDF       Save
Aims

There are different components of carbon (C) pools in a natural forest ecosystem: biomass, soil, litter and woody debris. We asked how these pools changed with elevation in one of China’s ecologically important forest ecosystem, i.e. beech (Fagus L., Fagaceae) forests, and what were the underlying driving factors of such variation.

Methods

The four C pools in nine beech forests were investigated along an elevational gradient (1095–1930 m) on Mt. Fanjingshan in Guizhou Province, Southwest China. Variance partitioning was used to explore the relative effects of stand age, climate and other factors on C storage. In addition, we compared the four C pools to other beech forests in Guizhou Province and worldwide.

Important Findings

The total C pools of beech forest ecosystems ranged from 190.5 to 504.3 Mg C ha–1, mainly attributed to biomass C (accounting for 33.7–73.9%) and soil C (accounting for 23.9–65.5%). No more than 4% of ecosystem C pools were stored in woody debris (0.05–3.1%) and litter (0.2–0.7%). Ecosystem C storage increased significantly with elevation, where both the biomass and woody debris C pools increased with elevation, while those of litter and soil exhibited no such trend. For the Guizhou beech forests, climate and stand age were found to be key drivers of the elevational patterns of ecosystem and biomass C storage, while for beech forests globally, stand age was the most important predictor. Compared to beech forests worldwide, beech forests in Guizhou Province displayed a relatively higher biomass C accumulation rate, which may be explained by a much higher precipitation in this area. The present study provides basic data for understanding the C budgets of Chinese beech forests and their possible roles in regional C cycling and emphasizes the general importance of stand age and climate on C accumulation.

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Spatiotemporal variation in leaf size and shape in response to climate
Yaoqi Li, Dongting Zou, Nawal Shrestha, Xiaoting Xu, Qinggang Wang, Wen Jia and Zhiheng Wang
J Plant Ecol    2020, 13 (1): 87-96.   DOI: 10.1093/jpe/rtz053
Online available: 02 December 2019

Abstract54)      PDF       Save
Aims

Morphological variation of leaves is a key indicator of plant response to climatic change. Leaf size and shape are associated with carbon, water and energy exchange of plants with their environment. However, whether and how leaf size and shape responded to climate change over the past decades remains poorly studied. Moreover, many studies have only explored inter- but not intraspecific variation in leaf size and shape across space and time.

Methods

We collected >6000 herbarium specimens spanning 98 years (1910–2008) in China for seven representative dicot species and measured their leaf length and width. We explored geographical patterns and temporal trends in leaf size (i.e. leaf length, leaf width and length × width product) and shape (i.e. length/width ratio), and investigated the effects of changes in precipitation and temperature over time and space on the variation in leaf size and shape.

Important Findings

After accounting for the effects of sampling time, leaf size decreased with latitude for all species combined, but the relationship varied among species. Leaf size and shape were positively correlated with temperature and precipitation across space. After accounting for the effects of sampling locations, leaf size of all species combined increased with time. Leaf size changes over time were mostly positively correlated with precipitation, whereas leaf shape changes were mostly correlated with temperature. Overall, our results indicate significant spatial and temporal intraspecific variation in leaf size and shape in response to climate. Our study also demonstrates that herbarium specimens collected over a considerable period of time provide a good resource to study the impacts of climate change on plant morphological traits.

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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
Abstract66)      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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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
Abstract84)      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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Detecting the driving forces underlying the divergence of spruce forests in China: evidence from phytocoenology, morphology and phylogenetics
Guo-Hong Wang, Hai-Wei Zhao, Meng An, He Li and Wei-Kang Zhang
J Plant Ecol    2020, 13 (1): 59-69.   DOI: 10.1093/jpe/rtz047
Online available: 21 October 2019

Abstract61)      PDF       Save
Aims

We aimed to elucidate the driving forces underlying the geographical distribution of spruce forests, as well as the morphological and phylogenetic divergence among spruce species in China.

Methods

One hundred and seventy two sites across the entire range of spruce forests in China (23°–53° N, 75°–134° E, 250–4300 m a.s.l.) were sampled for species composition, geographical coordinates, and topographic and climatic variables. Sixteen spruce taxa, which are naturally distributed in China, were respectively grouped into morphologically defined sections and phylogenetically distinct clades. Multivariate approaches, including two-way indicator species analysis, principal components analysis, detrended correspondence analysis, canonical correspondence analysis (CCA), and partial CCA, were used for data analysis.

Important Findings

The 172 samples grouped into 13 spruce forests, the geographical distributions of which were closely related to climate and geographical location. The variation in species composition explained by the geographical coordinates (32.01%) was significantly higher than that explained by the climatic (27.76%) and topographic variables (23.32%). Of the three morphologically defined sections, sect. Omoricaoccurred mainly in wetter habitats with a mean annual precipitation of ca. 229 mm and 426 mm higher than the habitats of sect. Casicta and sect. Picea (P < 0.01), respectively. Of the two phylogenetically distinct clades, Clade-II (an older clade) occurred in habitats with warm winters and cool summers whose mean temperature in the coldest month was ca. 8–10°C higher, yet accumulated temperature during the growing season (≥ 5°C) was ca. 297–438°C lower, than the habitats of Clade-III (a younger clade) (P< 0.01). Our data support the hypothesis that geographical location may be a greater determinant of variation in species composition. In addition, moisture conditions tend to be the key determinants that account for the divergence among the morphologically defined sections, while the phylogenetic divergence among spruce species is mainly affected by temperature conditions. While the clades or sections of the spruce species in question carry strong climatic signals, their divergences are subject to different selective pressures.

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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
Abstract158)      PDF (2852KB)(37)       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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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
Abstract103)      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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Climatic niche shift of an invasive shrub (Ulex europaeus): a global scale comparison in native and introduced regions
Mathias Christina, Fawziah Limbada and Anne Atlan
J Plant Ecol    2020, 13 (1): 42-50.   DOI: 10.1093/jpe/rtz041
Online available: 16 August 2019

Abstract80)      PDF       Save
Aims

Invasive species, which recently expanded, may help understand how climatic niche can shift at the time scale of the current global change. Here, we address the climatic niche shift of an invasive shrub (common gorse, Ulex europaeus) at the world and regional scales to assess how it could contribute to increasing invasibility.

Methods

Based on a 28 187 occurrences database, we used a combination of 9 species distribution models (SDM) to assess regional climatic niche from both the native range (Western Europe) and the introduced range in different parts of the world (North-West America, South America, North Europe, Australia and New Zealand).

Important Findings

Despite being restricted to annual mean temperature between 4°C and 22°C, as well as annual precipitation higher than 300 mm/year, the range of bioclimatic conditions suitable for gorse was very large. Based on a native versus introduced SDM comparison, we highlighted a niche expansion in North-West America, South America and to a lesser degree in Australia, while a niche displacement was assessed in North Europe. These niche changes induced an increase in potential occupied areas by gorse by 49, 111, 202 and 283% in Australia, North Europe, North-West America and South America, respectively. On the contrary, we found no evidence of niche change in New Zealand, which presents similar climatic condition to the native environment (Western Europe). This study highlights how niche expansion and displacement of gorse might increase invasibility at regional scale. The change in gorse niche toward new climatic conditions may result from adaptive plasticity or genetic evolution and may explain why it has such a high level of invasibility. Taking into account the possibility of a niche shift is crucial to improve invasive plants management and control.

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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

Abstract110)      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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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

Abstract84)      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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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

Abstract80)      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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Comparison of leaf area index inversion for grassland vegetation through remotely sensed spectra by unmanned aerial vehicle and field-based spectroradiometer
Zongyao Sha, Yuwei Wang, Yongfei Bai, Yujin Zhao, Hua Jin, Ya Na and Xiaoliang Meng
J Plant Ecol    2019, 12 (3): 395-408.   DOI: 10.1093/jpe/rty036
Online available: 15 September 2018

Abstract116)      PDF       Save
Aims

Remote sensing technology has been proved useful in mapping grassland vegetation properties. Spectral features of vegetation cover can be recorded by optical sensors on board of different platforms. With increasing popularity of applying unmanned aerial vehicle (UAV) to mapping plant cover, the study aims to investigate the possible applications and potential issues related to mapping leaf area index (LAI) through integration of remote sensing imagery collected by multiple sensors.

Methods

This paper applied the collected spectral data through field-based (FLD) and UAV-borne spectroradiometer to map LAI in a Sino–German experiment pasture located in the Xilingol grassland, Inner Mongolia, China. Spectroradiometers on FLD and UAV platforms were taken to measure spectral reflectance related to the targeted vegetation properties. Based on eight vegetation indices (VIs) computed from the collected hyperspectral data, regression models were used to inverse LAI. The spectral responses between FLD and UAV platforms were compared, and the regression models relating LAI with VIs from FLD and UAV were established. The modeled LAIs by UAV and FLD platforms were analyzed in order to evaluate the feasibility of potential integration of spectra data for mapping vegetation from the two platforms.

Important Findings

Results indicated that the spectral reflectance between FLD and UAV showed critical gaps in the green and near-infrared regions of the spectrum over densely vegetated areas, while the gaps were small over sparsely vegetated areas. The VI values from FLD spectra were greater than their UAV-based counterparts. Out of all the VIs, broadband generalized soil-adjusted vegetation index (GESAVI) and narrow-band nNDVI2 were found to achieve the best results in terms of the accuracy of the inversed LAIs for both FLD and UAV platforms. We conclude that GESAVI and nNDVI2 are the two promising VIs for both platforms and thus preferred for LAI inversion to carry spectra integration of the two platforms. We suggest that accuracy on the LAI inversion could be improved by applying more advanced functions (e.g. non-linear) considering the observed bias for the difference between the UAV- and FLD-inversed LAIs, especially when LAI was low.

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Directional changes of species spatial dispersion and realized environmental niches drive plant community assembly during early plant succession
Werner Ulrich, Markus Klemens Zaplata, Susanne Winter and Anton Fischer
J Plant Ecol    2019, 12 (3): 409-418.   DOI: 10.1093/jpe/rty038
Online available: 01 October 2018

Abstract119)      PDF       Save
Aims

Probabilistic models of species co-occurrences predict aggregated intraspecific spatial distributions that might decrease the degree of joint species occurrences and increase community richness. Yet, little is known about the influence of intraspecific aggregation on the co-occurrence of species in natural, species-rich communities. Here, we focus on early plant succession and ask how changes in intraspecific aggregation of colonizing plant species influence the pattern of species co-existence, richness and turnover.

Methods

We studied the early vegetation succession in a six ha constructed catchment within the abandoned part of a lignite mine in NE Germany. At two spatial scales (1- and 25-m2 plots), we compared for each pair of species the intraspecific degree of aggregation and the pattern of co-occurrence and compared observed relationships with temporal changes in important species functional traits.

Important Findings

The majority of species occurred in an aggregated manner, particularly in the first 2 years of succession. In pairwise comparisons, we found an excess of segregated species occurrences leading to a positive link between intraspecific aggregation and pairwise species segregation as predicted by the aggregation hypothesis, particularly at the lower spatial resolution. The degree of intraspecific aggregation was negatively correlated with the community-wide level of species spatial turnover and with plot species richness. Our results are the first direct confirmation that increasing intraspecific aggregation and interspecific competitive interactions counteract in shaping plant community structure during succession. The respective effects of aggregation were strongest at intermediate states of early succession.

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Smoke interacts with fire history to stimulate soil seed bank germination in Mediterranean woodlands
Neta Manela, Ella Dagon, Hagai Semesh and Ofer Ovadia
J Plant Ecol    2019, 12 (3): 419-427.   DOI: 10.1093/jpe/rty052
Online available: 07 December 2018

Abstract90)      PDF       Save
Aims

Fire has important consequences on vegetation dynamics. In fire-prone areas, natural selection favors plant species, characterized by a large soil seed bank, and that their germination is stimulated by fire. Although seed germination stimulated by fire heat is common in the eastern Mediterranean Basin, only little is known about germination stimulation by smoke. We examined the interactive effect of aerosol smoke and fire history on the germinable soil seed bank (GSSB) community in eastern Mediterranean woodlands.

Methods

We collected soil samples from sites that have been subjected to different fire frequencies during the last four decades and exposed them to aerosol smoke, with or without watering. By documenting the seed germination patterns characterizing these samples, we could test for changes in the abundance and richness of the germinable seeds in the soil.

Important Findings

Total GSSB density was higher in sites that were burned more frequently during the last four decades. Exposure to aerosol smoke increased the GSSB density, and this pattern was more pronounced in samples originating from sites burned more frequently, as well as among annual species. Notably, exposing wet samples to aerosol smoke caused a significant reduction in GSSB density and richness. These results highlight the importance of exploring germination responses using intact soil samples, rather than synthetic seed communities. Moreover, our findings emphasize the important role smoke plays in shaping post-fire succession processes in the Mediterranean Basin, mainly by stimulating the germination of annual species.

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C:N:P stoichiometry of Ericaceae species in shrubland biomes across Southern China: influences of climate, soil and species identity
Qiang Zhang, Qing Liu, Huajun Yin, Chunzhang Zhao, Lin Zhang, Guoying Zhou, Chunying Yin, Zhijun Lu, Gaoming Xiong, Yuelin Li, Jiaxiang Li, Wenting Xu, Zhiyao Tang and Zongqiang Xie
J Plant Ecol    2019, 12 (2): 346-357.   DOI: 10.1093/jpe/rty033
Online available: 30 August 2018

Abstract132)      PDF       Save
Aims

Carbon (C), nitrogen (N) and phosphorus (P) stoichiometry strongly affect functions and nutrient cycling within ecosystems. However, the related researches in shrubs were very limited. In this study, we aimed to investigate leaf stoichiometry and its driving factors in shrubs, and whether stoichiometry significantly differs among closely related species.

Methods

We analyzed leaf C, N and P concentrations and their ratios in 32 species of Ericaceae from 161 sites across southern China. We examined the relationships of leaf stoichiometry with environmental variables using linear regressions, and quantified the interactive and independent effects of climate, soil and species on foliar stoichiometry using general linear models (GLM).

Important Findings

The foliar C, N and P contents of Ericaceae were 484.66, 14.44 and 1.06 mg g?1, respectively. Leaf C, N and P concentrations and their ratios in Ericaceae were significantly related with latitude and altitude, except the N:P insignificantly correlated with latitude. Climate (mean annual temperature and precipitation) and soil properties (soil C, N and P and bulk density) were significantly influenced element stoichiometry. The GLM analysis showed that soil exerted a greater direct effect on leaf stoichiometry than climate did, and climate affected leaf traits mainly via indirect ways. Further, soil properties had stronger influences on leaf P than on leaf C and N. Among all independent factors examined, we found species accounted for the largest proportion of the variation in foliar stoichiometry. These results suggest that species can largely influence foliar stoichiometry, even at a lower taxonomic level.

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Do subtropical grasslands recover spontaneously after afforestation?
Fábio Piccin Torchelsen, Monica Cadenazzi, Gerhard Ernst Overbeck
J Plant Ecol    2019, 12 (2): 228-234.   DOI: 10.1093/jpe/rty011
Online available: 09 March 2018

Abstract74)      PDF       Save
Aims

South American Pampa grasslands are habitats of great conservation interest, with a distinct and rich flora, but have been intensely converted to other land uses, including tree plantations. While necessity for restoration grows, no information on restoration potential of grasslands after afforestation exists. Here, we aim at analyzing composition and structure of grassland vegetation with a history of eucalyptus plantations in order to assess recovery potential of these areas. We hypothesized that areas with history of eucalyptus would differ from reference grasslands with no history of land-use change in terms of floristic and functional composition and would present lower species richness.

Methods

Our study region comprised four sites in the southeastern part of the Pampa biome, in the coastal plain in the extreme south of Brazil, always with sites with long (50 years) history of eucalyptus plantation and reference grassland. We sampled vegetation at post-eucalyptus sites (with and without resprouting) 10 years after clearclutting and in natural grasslands. We analyzed data by analysis of variance and ordination techniques, considering compositional parameters and life forms, and indicator species analysis.

Important Findings

Species richness and vegetation cover were higher in reference grassland than in resprout areas but did not differ from post-eucalyptus areas. Exotic species cover was significantly higher in areas with afforestation history. In terms of total composition, natural grasslands differed significantly from areas with past plantation use. Indicator species analyses revealed considerable differences between grassland types. In conclusion, vegetation development led to grassland communities that are still quite distinct from reference sites. Likely, the specificity of grassland management has a high importance in defining vegetation trajectories in time and importance for grassland recovery, and restoration needs to be addressed in more studies.

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Latitudinal pattern and the driving factors of leaf functional traits in 185 shrub species across eastern China
Yongkai Luo, Huifeng Hu, Mengying Zhao, He Li, Shangshi Liu and Jingyun Fang
J Plant Ecol    2019, 12 (1): 67-77.   DOI: 10.1093/jpe/rtx065
Online available: 17 November 2017

Abstract122)      PDF       Save
Aims

To explore the pattern of the leaf functional traits of shrub species along a latitudinal gradient in eastern China and determine the driving factors of leaf trait variation at a large scale.

Methods

We investigated the leaf thickness (LT), leaf area (LA), specific leaf area (SLA) and leaf dry mass content (LDMC) of 185 shrub species from 13 sites across eastern China. The trends of these four-leaf traits were analyzed with respect to latitude, and the differences between different life forms (e.g., evergreen and deciduous) and habitats (e.g., understory and typical) were compared. We quantified the effects of the plant life forms and environmental factors on the leaf traits via mixed-model analyses.

Important Findings

The LT and LA decreased, whilst and the LDMC increased, as the latitude increased, and significant differences in these traits were observed between the different plant life forms. The LT and LA were smaller, whereas the SLA and LDMC were larger in deciduous shrubs than in evergreen shrubs. Among the different habitats, the LA and SLA were larger, while the LDMC was smaller in understory shrubs than in typical shrub species. These results indicate that typical shrub species are better adapted to drier environments, as indicated by a reduced LT and increased LDMC. Furthermore, general linear models showed that variations in the four-leaf traits with respect to latitude were mainly caused by a shift in plant life forms.

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Size-asymmetric root competition in deep, nutrient-poor soil
Camilla Ruø Rasmussen, Anne Nygaard Weisbach, Kristian Thorup-Kristensen and Jacob Weiner
J Plant Ecol    2019, 12 (1): 78-88.   DOI: 10.1093/jpe/rtx064
Online available: 20 November 2017

Abstract108)      PDF       Save
Aims

There is much evidence that plant competition below ground is size symmetric, i.e. that competing plants share contested resources in proportion to their sizes. Several researchers have hypothesized that a patchy distribution of soil nutrients could result in size-asymmetric root competition. We tested this hypothesis.

Methods

In a greenhouse experiment, Triticum aestivum (wheat) individuals of different initial sizes were grown alone or with below-ground competition from one neighbour, in 1 m tall, narrow containers in a nitrogen-poor field soil with (i) no added nitrogen, (ii) nitrogen fertilizer mixed into the upper 50 cm, and (iii) the same amount of fertilizer mixed into a 20–30 cm deep layer. We measured total leaf length throughout the experiment, and above-ground biomass and nitrogen concentration at harvest. We also measured root depth and frequency over time in a subset of containers.

Important Findings

Competing plants were half the size of non-competing plants, meaning that root competition was very strong. Root competition was size-asymmetric to some degree in all soil treatments. Neighbours larger than the target plant showed a greater per-unit-size effect on target growth than neighbours smaller than the target. Size variation increased over time for competing individuals, but decreased for non-competing pairs. Contrary to expectations, the presence of a high-nutrient patch reduced the strength and size asymmetry of competition temporarily. Size asymmetry in poor, deep soils may result from directionality in resource interception as roots compete for limited nutrients by growing deeper into soil layers that have not yet been exploited. Root competition can be size asymmetric, but not to the same degree as competition for light.

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Comparative water relations of co-occurring trees in a mixed podocarp-broadleaf forest
Julia Kaplick, Michael J. Clearwater and Cate Macinnis-Ng
J Plant Ecol    2019, 12 (1): 163-175.   DOI: 10.1093/jpe/rty004
Online available: 31 January 2018

Abstract77)      PDF       Save
Aims

As extreme climatic events including droughts and heat waves become more common in a changing climate, tree mortality has increased across the globe. In order to determine whether certain species have a competitive advantage over others, we explored the water-relations and leaf-gas exchange of four co-occurring species in a forest in northern Aotearoa-New Zealand. We studied the ecologically and culturally significant foundation species, Agathis australis (a conifer), two additional conifers, Phyllocladus trichomanoides and Podocarpus totara and the angiosperm Knightia excelsa.

Methods

We measured sap flow, leaf-gas exchange and xylem water potentials of leaves and terminal branches with concurrent measures of micrometeorological data on days with very few clouds. We derived whole tree hydraulic conductance and instantaneous water-use efficiency (WUEi) at our remnant forest in west Auckland during February 2015 (southern hemisphere summer).

Important Findings

The four species behaved similarly in their diurnal curves of gas exchange and water potential. Rates of assimilation, stomatal conductance and WUEi were similar among trees of different species. Whole tree hydraulic conductance was also similar among species. These results indicate functional convergence in water relations, possibly driven by low nutrient soils at the site. Our results suggest that there is no species with a clear adaptive advantage over the others in the context of climate change.

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Water availability drives gradients of tree diversity, structure and functional traits in the Atlantic–Cerrado–Caatinga transition, Brazil
Marcela de Castro Nunes Santos Terra, Rubens Manoel dos Santos, Jamir Afonso do Prado Júnior, José Marcio de Mello, José Roberto Soares Scolforo, Marco Aurélio Leite Fontes, Ivan Schiavini, Aliny Aparecida dos Reis, Inacio Thomaz Bueno, Luiz Fernando Silva Magnago and Hans ter Steege
J Plant Ecol    2018, 11 (6): 803-814.   DOI: 10.1093/jpe/rty017
Online available: 04 June 2018

Abstract101)      PDF       Save
Aims

Climate and soil are among the most important factors determining variation in tree communities, but their effects have not been thoroughly elucidated to date for many vegetation features. In this study, we evaluate how climate and soil gradients affect gradients of vegetation composition, species diversity and dominance, structure and functional traits (seed mass and wood density) using over 327 000 trees in 158 sites distributed along environmental gradients in the transitions among the Atlantic forest, Cerrado and Caatinga in Minas Gerais State (MG), Brazil (nearly 600 000 km2).

Methods

Gradients in species, genus and family abundance in addition to basal area, stem density, species diversity (Fisher’s alpha), dominance percentage, seed mass and wood density were correlated using multiple regressions with environmental variables, as summarized in four principal component analysis axes (two climatic—precipitation seasonality and temperature range—and two edaphic—soil fertility and soil moisture). Additionally, ordinary kriging maps were used to better illustrate the gradients.

Important Findings

Multiple regression models indicate that all variables but dominance percentage were affected by one or more of the environmental gradients, but the average R2 was low (26.25%). Kriging maps reinforced the patterns observed in the regression models. Precipitation seasonality and soil moisture gradients were the most important gradients affecting vegetation features. This finding suggests that water availability is an important determinant of vegetation features in these vegetation transitions.

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Nutrient resorption from senescing leaves of epiphytes, hemiparasites and their hosts in tropical forests of Sri Lanka
Lalith D. B. Suriyagoda, Ranil Rajapaksha, Gamini Pushpakumara and Hans Lambers
J Plant Ecol    2018, 11 (6): 815-826.   DOI: 10.1093/jpe/rtx049
Online available: 28 August 2017

Abstract105)      PDF       Save
Aims

Epiphytes and hemiparasites do not have direct access to soil nutrients. Epiphytes acquire nutrients through symbiosis, foliar leachates and throughfall, whilst hemiparasites have specialized structures (haustoria) to acquire nutrients from their host. Irrespective of the green leaf nutrient concentrations of epiphytes, hemiparasites and their hosts, nutrient-resorption efficiency and proficiency are expected to be the greater in epiphytes than in their hosts and in hemiparasites. These hypotheses were tested.

Methods

Green and senescing leaves of epiphytes (n = 23), hemiparasites (n = 9) and their hosts were collected, and leaf area, leaf dry weight, nutrient (nitrogen-N, phosphorus-P, potassium-K, calcium-Ca) and sodium (Na) concentrations were measured, and resorption efficiency (%) and proficiency were calculated.

Important Findings

Concentrations of N, P, K, Ca and Na in green leaves of epiphytes and hemiparasites were either similar or greater than those of their hosts, except for lower green leaf N concentration in hemiparasites. Epiphytes resorbed N, P, K and Na, while their hosts resorbed only N, P and K. Hemiparasites and their hosts resorbed P, K and Na while N was not resorbed. Overall, resorption efficiency was greatest in epiphytes > hemiparasites = hosts, while the resorption proficiencies were similar or greater for epiphytes and hemiparasites compared with their hosts, except for N in hemiparasites. Relatively high nutrient concentrations in epiphytes were associated with greater resorption efficiency. Understanding contrasting nutrient concentrations in epiphytes, hemiparasites and their hosts will be important in recognising their contribution to ecosystem nutrient cycling.

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The differences in carbon dynamics between boreal dwarf shrubs and Scots pine seedlings in a microcosm study
Liisa Kulmala, Maria del Rosario Dominguez Carrasco and Jussi Heinonsalo
J Plant Ecol    2018, 11 (5): 709-716.   DOI: 10.1093/jpe/rtx051
Abstract112)      PDF       Save
Aims

The ground level of boreal pine forests consists of a dense layer of ericaceous shrubs, herbs, grasses, mosses and lichens. The primary productivity of this forest floor vegetation is notable but the role the most common ericoid dwarf shrub plant species, Calluna vulgarisVaccinium myrtillus and Vaccinium vitis-idaea, play in carbon (C) cycling in these ecosystems is poorly understood. Here, we studied their C dynamics in detail using plants of similar size (age 14–19 months) in a microcosm study.

Methods

We determined the full C balances of these dwarf shrubs for the first time and compared them to those of Pinus sylvestris by using long-term biomass accumulation, 13C pulse labelling and CO2 exchange measurements in a controlled laboratory experiment.

Important Findings

Pinus sylvestris had significantly higher biomass-based C fluxes than dwarf shrubs, both aboveground and belowground, but the dwarf shrubs did not differ in the biomass-based fluxes. We showed that root respiration of the evergreen ericoid dwarf shrubs was sensitive to the aboveground light conditions as belowground respiration was 50–70% higher under light compared with dark conditions. Such light-related differences were not observed for Scots pine. The observed differences in C dynamics are important in estimating the origin of belowground CO2 fluxes and in evaluating their biological relevance. Our results improve current understanding of CO2 sources and sinks in boreal ecosystems.

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Plant responses to variable timing of aboveground clipping and belowground herbivory depend on plant age
Minggang Wang, T. Martijn Bezemer, Wim H. van der Putten, E. Pernilla Brinkman and Arjen Biere
J Plant Ecol    2018, 11 (5): 696-708.   DOI: 10.1093/jpe/rtx043
Online available: 03 August 2017

Abstract83)      PDF       Save
Aims

Plants use different types of responses such as tolerance and induced defense to mitigate the effects of herbivores. The direction and magnitude of both these plant responses can vary with plant age. However, most studies have focused on aboveground herbivory, whereas important feeding occurs belowground. Here, we tested the hypothesis that plant tolerance and defense following shoot damage or root herbivory depends on plant age.

Methods

In order to test our hypothesis, we exposed the perennial grass species Holcus lanatus to defoliation and root nematode inoculation at three growth stages (young, intermediate and old plants), and examined responses of plant traits related to tolerance (regrowth following defoliation) and defense (leaf and root nitrogen and phenolics).

Important Findings

Defoliation overall reduced plant shoot and root biomass as well as foliar concentrations of phenolics regardless of plant age at defoliation. In contrast, defoliation increased foliar N concentrations, but only when defoliation occurred at intermediate and old plant age. Inoculation with root-feeding nematodes reduced root N concentrations after a prolonged period of growth, but only when nematodes had been inoculated when plants were young. The relative shoot regrowth rate of plants increased immediately after defoliation but this was independent of the plant age at which defoliation occurred, i.e. was not stronger in plants that were defoliated at a more advanced age, as hypothesized. Similarly, relative root growth rates increased shortly after defoliation, but this was only observed for plants defoliated when they were young. We conclude that plant responses to aboveground and belowground herbivory in traits related to both defense and tolerance are affected by plant age, but do not generally change with plant age.

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Effects of the frequency and the rate of N enrichment on community structure in a temperate grassland
Yunhai Zhang, Jing Wang, Carly J Stevens, Xiaotao Lü, Nianpeng He, Changhui Wang, Xingguo Han
J Plant Ecol    2018, 11 (5): 685-695.   DOI: 10.1093/jpe/rtx041
Online available: 19 July 2017

Abstract128)      PDF       Save
Aims

Nitrogen (N) enrichment caused by human activities threatens biodiversity and alters plant community composition and structure. It has been found that heavy and infrequent N inputs may over-estimate species extinction, but it remains unclear whether plant community structure will equally respond to frequent reactive N enriched conditions.

Methods

We independently manipulated the rates and the frequencies of N addition in a temperate steppe, northern China, between 2008 and 2013.

Important Findings

We found that plant community structure changes, measured by ‘Euclidean distance’ involving species richness, composition and productivity, were significantly positively related to increasing N enrichment rates rather than frequencies. Changes in aboveground net primary productivity (ANPP), plant species richness and shifts in dominant species were observed. Community ANPP increased with N enrichment, whereas species richness reduced. The frequency of N enrichment increased species richness but had no impacts on community ANPP and the relative ANPP of the two dominant species, C3perennial bunchgrass Stipa grandis and C3 perennial rhizome grass Leymus chinensis. The ANPP and relative ANPP of the two dominant species were significantly negatively correlated with each other. Moreover, changes in the relative ANPP of S. grandis was negatively associated with the changes in community structure. After 5 years’ treatment, direct influence of the frequency of N enrichment on plant community structure was not observed, but the effects of the rate of N enrichment were apparent. Our results suggested that further study in various ecosystems and with long-term and well-controlled comparisons the frequency vs. the rate of N enrichment may still be needed.

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Emergent interactions influence functional traits and success of dune building ecosystem engineers
Joseph K. Brown, Julie C. Zinnert, Donald R. Young
J Plant Ecol    2018, 11 (4): 524-532.   DOI: 10.1093/jpe/rtx033
Abstract144)      PDF       Save
Aims Dune building processes are affected by interactions between the growth of ecosystem engineering dune grasses and environmental factors associated with disturbance such as sand burial and sea spray. Research investigating how species interactions influence dune community structure and functional trait responses in high abiotic stress environments is minimal. We investigated how species interactions influence the functional trait responses of three dominant dune grasses to common abiotic stressors.
Methods We performed a multi-factorial greenhouse experiment by planting three common dune grasses (Ammophila breviligulata Fern., Uniola paniculata L. and Spartina patens Muhl.) in different interspecific combinations, using sand burial and sea spray as abiotic stressors. Sand burial was applied once at the beginning of the study. Sea spray was applied three times per week using a calibrated spray bottle. Morphological functional trait measurements (leaf elongation, maximum root length, aboveground biomass and belowground biomass) were collected at the end of the study. The experiment continued from May 2015 to August 2015.
Important findings Species interactions between A. breviligulata and U. paniculata negatively affected dune building function traits of A. breviligulata, indicating that interactions with U. paniculata could alter dune community structure. Furthermore, A. breviligulata had a negative interaction with S. patens, which decreased S. patens functional trait responses to abiotic stress. When all species occurred together, the interactions among species brought about coexistence of all three species. Our data suggest that species interactions can change traditional functional trait responses of dominant species to abiotic stress.
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Simulated N and S deposition affected soil chemistry and understory plant communities in a boreal forest in western Canada
Kangho Jung, Jin-Hyeob Kwak, Frank S. Gilliam, Scott X. Chang
J Plant Ecol    2018, 11 (4): 511-523.   DOI: 10.1093/jpe/rtx030
Abstract156)      PDF       Save
Aims We conducted a simulated nitrogen (N) and sulfur (S) deposition experiment from 2006 to 2012 to answer the following questions: (i) does chronic N and S deposition decrease cation concentrations in the soil and foliage of understory plant species, and (ii) does chronic N and S deposition decrease plant diversity and alter species composition of the understory plant community in a boreal forest in western Canada where intensifying industrial activities are increasing N and S deposition?
Methods Our field site was a mixedwood boreal forest stand located ~100 km southeast of Fort McMurray, Alberta, Canada. The experiment involved a 2 × 2 factorial design, with two levels each of N (0 and 30 kg N ha-1 yr-1; applied as NH4NO3) and S addition (0 and 30 kg S ha-1 yr-1; applied as Na2SO4). Four blocks were established in July 2006, each with four plots of 20 × 20 m randomly assigned to the treatments. Soil and understory vegetation were sampled and cover (%) of individual species of herb (height ≤ 0.5 m) and shrub (height 0.5–1 m) layers was determined in August 2012.
Important findings Seven years after the treatments began, N addition increased dissolved organic carbon and N in the mineral soil (P < 0.05), whereas S addition decreased exchangeable cations (P < 0.05) in the forest floor. In the shrub layer, species evenness, and overall diversity were decreased by N addition (P < 0.05) due to increases in abundance of nitrophilous species and S addition (P < 0.01) due to decreased cation concentrations in soils. Total shrub cover decreased with S addition (P < 0.10). Nitrogen and S addition affected neither species richness nor evenness in the herb layer. However, permutational multivariate analysis of variance and non-metric multidimensional scaling analyses (based on plant cover) indicated that the effect of N and S addition on understory plant species composition in the both shrub and herb layers was species-specific. Addition of N decreased foliar phosphorus and potassium concentrations in some species, suggesting potential risk of N-meditated nutrient imbalance in those species. Our results indicate that long-term elevated levels of N and S deposition can negatively impact plant nutrition and decrease the diversity of the understory plant community in boreal forests in northern Alberta, Canada. However, considering that the current N and S deposition rates in northern Alberta are much lower than the rates used in this study, N and S deposition should not negatively affect plant diversity in the near future.
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Plant responses to simulated warming and drought: a comparative study of functional plasticity between congeneric mid and high elevation species
Elena Hamann, Halil Kesselring, Jürg Stöcklin
J Plant Ecol    2018, 11 (3): 364-374.   DOI: 10.1093/jpe/rtx023
Abstract122)      PDF       Save
Aims Effects of climate change, especially changes in temperatures and precipitation patterns, are particularly pronounced in alpine regions. In response, plants may exhibit phenotypic plasticity in key functional traits allowing short-term adjustment to novel conditions. However, little is known about the degree of phenotypic plasticity of high elevation species relative to mid elevation congeners.
Methods We transplanted 14 herbaceous perennial species from high elevation into two common gardens (1050 and 2000 m.a.s.l.) in the Swiss Alps, and we examined plastic responses in key functional traits to changes in temperature and soil water availability. This design was replicated with 14 congeneric species from mid elevation to assess if the degree of phenotypic plasticity differs between mid and high elevation species. Survival was assessed across two growing seasons, while aboveground biomass and specific leaf area (SLA) were measured after the first growing season, and biomass allocation to belowground and reproductive structures after the second. Moreover, a phenotypic plasticity index was calculated for the functional traits to compare the degree of plasticity between mid and high elevation species.
Important findings Aboveground biomass was higher in mid elevation species relative to high elevation congeners in all treatments, yet decreased for both with elevation and drought. Similarly, SLA decreased with elevation and drought. Root mass fraction (RMF) was generally higher in high elevation species, and decreased with drought at the lower site. Drought increased the allocation to reproductive structures, especially when plants were grown at their elevation of origin. Interestingly, no difference was found in the degree of phenotypic plasticity averaged across mid and high elevation species for any of the studied functional traits. These results indicate that phenotypic plasticity in the focal traits did not depend on the elevation of origin of the species. Plasticity was not related to environmental heterogeneity, nor constrained by selective pressures at high elevation. However, both species groups showed a remarkable capacity for short-term acclimation to a prospective climate through rapid adjustments in key functional traits.
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Aboveground resilience to species loss but belowground resistance to nitrogen addition in a montane plant community
Quentin D. Read, Jeremiah A. Henning, Aimée T. Classen, Nathan J. Sanders
J Plant Ecol    2018, 11 (3): 351-363.   DOI: 10.1093/jpe/rtx015
Abstract103)      PDF       Save
Aims Decades of empirical work have demonstrated how dominant plant species and nitrogen fertilization can influence the structure and function of plant communities. More recent studies have examined the interplay between these factors, but few such studies use an explicit trait-based framework. In this study, we use an explicit trait-based approach to identify potential mechanisms for community-level responses and to test ecological niche theory.
Methods We experimentally manipulated plant communities (control, ?dominant species, ?random biomass) and nitrogen (N) inputs (control, +organic N, +inorganic N) in a fully factorial design. We predicted that traits related to plants' ability to take up different forms of soil N would differ between dominant and subordinate species, resulting in interactive effects of dominant species loss and N fertilization on plant community structure and function. The study took place in a montane meadow in the Rocky Mountains, Colorado, USA.
Important findings After four years, the plant community in removal plots converged toward a species composition whose leaf and root functional traits resembled those of the previously removed dominant species. Ecosystem productivity generally increased with N addition: soil carbon efflux was ~50% greater when either form of N was added, while inorganic N addition increased aboveground biomass production by ~60% relative to controls. The increase in production was mediated by increased average height, leaf mass:area ratio and leaf dry matter content in plant communities to which we added inorganic N. Contrary to our predictions, there were no interactive effects of N fertilization and dominant species loss on plant community structure or ecosystem function. The plant community composition in this study exhibited resistance to soil N addition and, given the functional convergence we observed, was resilient to species loss. Together, our results indicate that the ability of species to compensate functionally for species loss confers resilience and maintains diversity in montane meadow communities.
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Variation of carbon and nitrogen stoichiometry along a chronosequence of natural temperate forest in northeastern China
Xingyun Liang, Shirong Liu, Hui Wang, Jingxin Wang
J Plant Ecol    2018, 11 (3): 339-350.   DOI: 10.1093/jpe/rtx008
Abstract164)      PDF       Save
Aims Carbon (C) and nitrogen (N) stoichiometry contributes to understanding elemental compositions and coupled biogeochemical cycles in ecosystems. However, we know little about the temporal patterns of C:N stoichiometry during forest development. The goal of this study is to explore the temporal patterns of intraspecific and ecosystem components' variations in C:N stoichiometry and the scaling relationships between C and N at different successional stages.
Methods Along forest development in a natural temperate forest, northeastern China, four age gradients were categorized into ca. 10-, 30-, 70- and 200-year old, respectively, and three 20 m × 20 m plots were set up for each age class. Leaves, branches, fine roots and fresh litter of seven dominant species as well as mineral soil at depth of 0–10 cm were sampled. A Universal CHN Elemental Analyzer was used to determine the C and N concentrations in all samples.
Important findings Intraspecific leaf C, N and C:N ratios remained stable along forest development regardless of tree species; while C, N concentrations and C:N ratios changed significantly either in branches or in fine roots, and they varied with tree species except Populus davidiana (P < 0.05). For ecosystem components, we discovered that leaf C:N ratios remained stable when stand age was below ca. 70 years and dominant tree species were light-demanding pioneers such as Betula platyphylla and Populus davidiana, while increased significantly at the age of ca. 200 years with Pinus koraiensis as the dominant species. C:N ratios in branches and fresh litter did not changed significantly along forest development stages. C concentrations scaled isometrically with respect to N concentrations in mineral soil but not in other ecosystem components. Our results indicate that, leaf has a higher intraspecific C:N stoichiometric stability compared to branch and fine root, whereas for ecosystem components, shifts in species composition mainly affect C:N ratios in leaves rather than other components. This study also demonstrated that C and N remain coupled in mineral soils but not in plant organs or fresh litter during forest development.
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A guide to analyzing biodiversity experiments
Bernhard Schmid, Martin Baruffol, Zhiheng Wang, Pascal A. Niklaus
J Plant Ecol    2017, 10 (1): 91-110.   DOI: 10.1093/jpe/rtw107
Abstract230)            Save
Aims The aim of this guide is to provide practical help for ecologists who analyze data from biodiversity–ecosystem functioning experiments. Our approach differs from others in the use of least squares-based linear models (LMs) together with restricted maximum likelihood-based mixed models (MMs) for the analysis of hierarchical data. An original data set containing diameter and height of young trees grown in monocultures, 2- or 4-species mixtures under ambient light or shade is used as an example.
Methods Starting with a simple LM, basic features of model fitting and the subsequent analysis of variance (ANOVA) for significance tests are summarized. From this, more complex models are developed. We use the statistical software R for model fitting and to demonstrate similarities and complementarities between LMs and MMs. The formation of contrasts and the use of error (LMs) or random-effects (MMs) terms to account for hierarchical data structure in ANOVAs are explained.
Important findings Data from biodiversity experiments can be analyzed at the level of entire plant communities (plots) and plant individuals. The basic explanatory term is species composition, which can be divided into contrasts in many ways depending on specific biological hypotheses. Typically, these contrasts code for aspects of species richness or the presence of particular species. For significance tests in ANOVAs, contrast terms generally are compared with remaining variation of the explanatory terms from which they have been 'carved out'. Once a final model has been selected, parameters (e.g. means or slopes for fixed-effects terms and variance components for error or random-effects terms) can be estimated to indicate the direction and size of effects.
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Impact Factor
1.833
5 year Impact Factor
2.299
Editors-in-Chief
Wen-Hao Zhang
Bernhard Schmid