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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

Abstract121)      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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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

Abstract92)      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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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

Abstract89)      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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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

Abstract88)      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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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

Abstract85)      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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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

Abstract78)      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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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

Abstract74)      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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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

Abstract69)      PDF       Save
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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

Abstract68)      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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Changes in vegetation and soil properties following 6 years of enclosure in riparian corridors
Di Wang, Yi-Ran Zhang, Yu-Long Feng, Zhi Liu and Bo Qu
J Plant Ecol    2020, 13 (2): 131-138.   DOI: 10.1093/jpe/rtaa002
Online available: 06 March 2020

Abstract68)      PDF       Save
Aims

Riparian corridors play vital roles in the maintenance of biodiversity. Nonetheless, plant species diversity and vegetation coverage in riparian corridors are seriously threatened by increasing pressure owing to livestock consumption and anthropogenic disturbance; even the stability of river courses has been threatened. The establishment of enclosures is a widely used strategy to restore degraded grassland ecosystems, but its impact on degraded herbaceous riparian vegetation and soil properties remains unclear. The aim of this study was to evaluate whether species composition, richness, diversity, and soil properties can be recovered by the enclosure.

Methods

Twenty long-term monitoring sample plots were set in the Liaohe main stream river, Liaohe main stream river was enclosed for grazing and farmland exclusion in 2012. The height, coverage and individual numbers of plant were recorded for species richness and diversity evaluation from 2012 to 2017; soil nutrients were measured for comparative analysis in 2012 and 2017. We examined the effects of the establishment of enclosures on plant species diversity and soil properties from 2012 to 2017 in the riparian corridors of the Liaohe River system in China.

Important Findings

Plant species richness and diversity significantly increased from 2012 to 2017. The dominance of Asteraceae plants increased, while the abundance of Gramineae plants decreased over time. The difference in abundance increased each year since enclosure was implemented in 2012. The concentrations of phosphorus and potassium in the soil significantly decreased as a result of the combined effects of vegetation restoration and prohibition of farming practices following the establishment of enclosures. There was also a lag time related to the response of soil organic matter to the establishment of enclosures. In conclusion, our study provides new evidence regarding the response of species diversity, species composition and soil properties following riparian vegetation restoration efforts through enclosure development.

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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

Abstract63)      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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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

Abstract63)      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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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

Abstract63)      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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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

Abstract62)      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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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

Abstract58)      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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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

Abstract53)      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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Species-specific responses to drought, salinity and their interactions in Populus euphratica and P. pruinosa seedlings
Lei Yu, Haojie Dong, Zhijun Li, Zhanjiang Han, Helena Korpelainen and Chunyang Li
J Plant Ecol    2020, 13 (5): 563-573.   DOI: 10.1093/jpe/rtaa043
Online available: 17 July 2020

Abstract52)      PDF       Save
Aims

Drought and salinity are severe abiotic stress factors, which limit plant growth and productivity, particularly in desert regions. In this study, we employed two desert poplars, Populus euphratica Oliver and Populus pruinosa Schrenk seedlings, to compare their tolerance to drought, salinity and combined stress.

Methods

We investigated species-specific responses of P. euphratica and P. pruinosa in growth, photosynthetic capacity and pigment contents, nonstructural carbohydrate concentrations, Cl allocation, osmotic regulation and the accumulation of reactive oxygen species (ROS) under drought, salinity and the combined stress.

Important Findings

Populus pruinosa exhibited greater growth inhibitory effects, photosynthesis decline, stomatal closure and ROS accumulation, and lower antioxidant enzyme activities and osmotic regulation compared with P. euphratica under drought, salinity and especially under their combined stress. On the other hand, salt-stressed P. euphratica plants restricted salt transportation from roots to leaves, and allocated more Cl to coarse roots and less to leaves, whereas salt-stressed P. pruinosa allocated more Cl to leaves. It was shown that there is species-specific variation in these two desert poplars, and P. pruinosa suffers greater negative effects compared with P. euphratica under drought, salinity and especially under the combined stress. Therefore, in ecological restoration and afforestation efforts, species-specific responses and tolerances of these two poplar species to drought and salinity should be considered under climate change with increasing drought and soil salinity developing.

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Resource enrichment combined with biomass removal maintains plant diversity and community stability in a long-term grazed grassland
Feng-Wei Xu, Jian-Jun Li, Li-Ji Wu, Xiao-Ming Lu, Wen Xing, Di-Ma Chen, Biao Zhu, Shao-Peng Wang, Lin Jiang and Yong-Fei Bai
J Plant Ecol    2020, 13 (5): 611-620.   DOI: 10.1093/jpe/rtaa046
Online available: 21 July 2020

Abstract50)            Save
Aims

Long-term heavy grazing reduces plant diversity and ecosystem function by intensifying nitrogen (N) and water limitation. In contrast, the absence of biomass removal can cause species loss by elevating light competition and weakening community stability, which is exacerbated by N and water enrichment. Hence, how to maintain species diversity and community stability is still a huge challenge for sustainable management of worldwide grasslands.

Methods

We conducted a 4-year manipulated experiment in six long-term grazing blocks to explore combination of resource additions and biomass removal (increased water, N and light availability) on species richness and community stability in semiarid grasslands of Inner Mongolia, China.

Important Findings

In all blocks treated with the combination of resource additions and biomass removal, primary productivity increased and species richness and community stability were maintained over 4 years of experiment. At both species and plant functional group (PFG) levels, the aboveground biomass of treated plants remained temporally stable in treatments with the combination of N and/or water addition and biomass removal. The maintenance of species richness was primarily caused by the biomass removal, which could increase the amount of light exposure for grasses under resource enrichment. Both species asynchrony and stability of PFGs contributed to the high temporal stability observed in these communities. Our results indicate that management practices of combined resource enrichment with biomass removal, such as grazing or mowing, could not only enhance primary productivity but also maintain plant species diversity, species asynchrony and community stability. Furthermore, as overgrazing-induced degradation and resource enrichment-induced biodiversity loss continue to be major problems worldwide, our findings have important implications for adaptive management in semiarid grasslands and beyond.

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Stoichiometry of leaf carbon, nitrogen, and phosphorus along a geographic, climatic, and soil gradients in temperate desert of Hexi Corridor, northwest China
Ke Zhang, Mengmeng Li, Yongzhong Su and Rong Yang
J Plant Ecol    2020, 13 (1): 114-121.   DOI: 10.1093/jpe/rtz045
Online available: 20 November 2019

Abstract49)      PDF       Save
Aims

Understanding the regional pattern of leaf stoichiometry and its contributing variables are of importance for predicting plant responses to global change and modelling the productivity and nutrient fluxes of ecosystems. In this study, we investigated leaf stoichiometry of plants that sampled from Hexi Corridor, a typical arid region in China, and tried to explore the contribution variables on leaf stoichiometry along the geographic, climatic, and soil gradients.

Methods

In August 2012, 70 sites in Hexi Corridor were investigated. Plant leaves and soils from five equivalent plots within each site were sampled. C, N, and P contents of leaf and soil were measured.

Important findings

Compared with leaf N and P contents in regional and global scales, leaf N content in Hexi Corridor was close to them with the value of 20.19 mg g-1, while leaf P content was lower than them with the value of 1.34 mg g-1. Overall, leaf N:P value in Hexi Corridor was 15.70. Individually, leaf N:P values of shrubs and herbs were 16.81 and 14.80, respectively. Scaling exponents for leaf N vs. P of overall and shrubs in Hexi Corridor were 1.29, higher than the scaling exponent of herbs (1.08). Leaf stoichiometry of shrubs and herbs did not show significant latitudinal and longitudinal patterns, meanwhile, it has no significant correlation with mean annual precipitation (MAP), mean annual temperature (MAT), and soil elements. However, only leaf stoichiometry of herbs has significant correlation with altitude and aridity degree. These results indicate that plants in Hexi Corridor are possibly co-limited by N and P, while shrubs are mainly limited by soil P and herbs are limited by soil N. Scaling relationship reveals that leaf N vs. P of herbs is isometric. With increasing altitude, the quadratic regression for leaf C and N contents and the linear regression for leaf P content of herbs reflect the difference responses of the three elements on the variation of MAT along the altitude and it could be explained by plant physiology hypothesis and biogeochemical hypotheses. With decreasing aridity, leaf N and N:P of herbs increased significantly, inferring that herbs growth would be limited by P increasingly and strengthening the increasing nitrogen availability with increasing precipitation. In conclusion, different altitude and aridity patterns for leaf stoichiometry of herbs and shrubs reveal the plastic survive strategies of different xerophytes in Hexi Corridor. Moreover, leaf stoichiometry of herbs in Hexi Corridor could be as indicator of the changing environment that caused by aridity.

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Species turnover drives grassland community to phylogenetic clustering over long-term grazing disturbance
Juntao Zhu , Yangjian Zhang, Wenfeng Wang, Xian Yang , Ning Chen , Ruonan Shen , Li Wang and Lin Jiang
J Plant Ecol    2020, 13 (2): 157-164.   DOI: 10.1093/jpe/rtz057
Online available: 23 December 2019

Abstract49)      PDF       Save
Aims

Grazing exerts profound effects on grassland ecosystem service and functions by regulating species composition and diversity, and structuring community assembly worldwide. However, adaptions of phylogenetic diversity and phylogenetic community structure to long-term grazing disturbance remain poorly studied, especially for ecosystems distributed in extreme environments.

Methods

Here, we conducted an experiment with multigrazing intensities to explore the impacts of grazing disturbance on plant phylogenetic diversity and community structure in an alpine grassland of the Tibetan Plateau.

Important Findings

Grazing disturbance enriched plant species richness (SR), and stimulated species turnover from regional species pool, consequently changing community species composition. Under low intensities, grazing exerted no obvious effects on phylogenetic diversity and community structure, whereas communities changed from overdispersion to clustering under high grazing intensity. High grazing intensity resulted in stronger environmental filtering, which consequently selected those species with high resilience to grazing disturbance. The observed clustering structure was associated with the colonizing species which were closely related to resident species, and locally extinct species, and distantly related to residents. At the plant functional trait level, high grazing intensity increased species colonization largely by altering the effect of root depth on species colonization compared to light grazing. Our results highlight that solely utilization of SR and diversity cannot fully represent grassland communities responses to grazing. The effects of species turnover on community phylogenetic diversity and structure are entailed to be explored in the future grazing studies.

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Physiological dormancy broken by endozoochory: Austral parakeets (Enicognathus ferrugineus) as legitimate dispersers of calafate (Berberis microphylla) in the Patagonian Andes
Carolina Bravo, Daniel Chamorro, Fernando Hiraldo, Karina Speziale, Sergio A. Lambertucci, José L. Tella and Guillermo Blanco
J Plant Ecol    2020, 13 (5): 538-544.   DOI: 10.1093/jpe/rtaa041
Online available: 16 July 2020

Abstract48)      PDF       Save
Aims

Seed dispersal by endozoochory is an important process in plant regeneration and the establishment of new populations. Seeds with dormancy may especially benefit after disperser gut passage. However, the ways in which gut passage affect the germination of plant species with physiological dormancy remain unclear. Here, we experimentally assessed the mutualistic interaction between the Austral parakeet (Enicognathus ferrugineus) as a disperser of calafate (Berberis microphylla), a thorny bush inhabiting the understory of the Austral temperate forests of South America with seeds that are characterized by deep physiological dormancy.

Methods

Germination success and viability of calafate seeds obtained from faeces and from intact fruits were tested under four treatments: (i) digested seeds, (ii) digested seeds with faecal extract, (iii) intact seeds from fruit and (iv) intact seeds from fruit with pulp.

Important Findings

About 65% of the Austral parakeet droppings contained calafate seeds. Viability of seeds did not differ between treatments. However, germination was significantly higher in digested seeds than in intact seeds from fruits, while no difference was found between faecal and pulp extracts. Neither faecal matter nor fruit pulp provided seeds with any ecological advantages derived from enhancing germinability, but did confer some disadvantage in germination time. Faecal matter is expected to be completely lacking around seeds after several months under snow before germinating in the following spring, given intense washing due to persistent rain and the spring thaw in the Patagonian Andes. The higher germinability along with faster germination of digested seeds supports the hypothesis of a legitimate mutualistic interaction between Austral parakeets and calafate. We hypothesized that the passage through the disperser digestive tract might break physiological dormancy as differences in germinability between ingested and non-ingested seeds. Our results highlight the relevant role of endozoochory in plant species with physiological dormancy living in highly seasonal environments.

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Trans-generational effects in the clonal invader Alternanthera philoxeroides
Rubén Portela, Bi-Cheng Dong, Fei-Hai Yu, Rodolfo Barreiro, Sergio R. Roiloa, and Dalva M. Silva Matos
J Plant Ecol    2020, 13 (1): 122-129.   DOI: 10.1093/jpe/rtz043
Online available: 26 August 2019

Abstract44)      PDF       Save
Aims

Recent studies have revealed heritable phenotypic plasticity through vegetative generations. In this sense, changes in gene regulation induced by the environment, such as DNA methylation (i.e. epigenetic changes), can result in reversible plastic responses being transferred to the offspring generations. This trans-generational plasticity is expected to be especially relevant in clonal plants, since reduction of sexual reproduction can decrease the potential for adaptation through genetic variation. Many of the most aggressive plant invaders are clonal, and clonality has been suggested as key to explain plant invasiveness. Here we aim to determine whether trans-generational effects occur in the clonal invader Alternanthera philoxeroides, and whether such effects differ between populations from native and non-native ranges.

Methods

In a common garden experiment, parent plants of A. philoxeroides from populations collected in Brazil (native range) and Iberian Peninsula (non-native range) were grown in high and low soil nutrient conditions, and offspring plants were transplanted to control conditions with high nutrients. To test the potential role of DNA methylation on trans-generational plasticity, half of the parent plants were treated with the demethylating agent, 5-azacytidine.

Important Findings

Trans-generational effects were observed both in populations from the native and the non-native ranges. Interestingly, trans-generational effects occurred on growth variables (number of ramets, stem mass, root mass and total mass) in the population from the native range, but on biomass partitioning in the population from the non-native range. Trans-generational effects of the population from the native range may be explained by a ‘silver-spoon’ effect, whereas those of the population from the non-native range could be explained by epigenetic transmission due to DNA methylation. Our study highlights the importance of trans-generational effects on the growth of a clonal plant, which could help to understand the mechanisms underlying expansion success of many clonal plants.

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Physiological and biomass partitioning shifts to water stress under distinct soil types in Populus deltoides saplings
Senlin Yang, Jian Shi, Lianghua Chen, Jian Zhang, Danju Zhang, Zhenfeng Xu, Jiujin Xiao, Peng Zhu, Yang Liu, Tiantian Lin, Li Zhang, Hanbo Yang and Yu Zhong
J Plant Ecol    2020, 13 (5): 545-553.   DOI: 10.1093/jpe/rtaa042
Online available: 16 July 2020

Abstract43)      PDF       Save
Aims

Although soil environments exist extensive heterogeneity for many plants with a wide range of distribution, researches about effects of soil conditions on plants’ tolerance and adaptation are particularly inadequate. In our study, the aims are to reveal physiological strategies of Populus deltoides against drought stress under different soil conditions and to select the most suitable soil type for Pdeltoides plantation.

Methods

Under controlled conditions, we used P. deltoides as a model species to detect differences in gas exchange rate, antioxidative capacity, nitrogen metabolism and biomass accumulation and partitioning in response to drought stress under three mineral soil types with distinct physicochemical characters, i.e. red soil (RS), yellow soil (YS) and yellow-brown soil (BS).

Important Findings

Exposure to 25% of field water holding capacity in soil for 3 months had significantly decreased biomass of all organs, photosynthetic rate, enzyme activities related to N assimilation, but increased H2O2, malondialdehyde and content of both NO3 and NH4+, when P. deltoideswas planted in both RS and YS. In contrast, under BS, there are slightly negative effects exerted by water deficit on total biomass, gas exchange rate, activities of enzymes related to nitrogen metabolism and membrane damage caused by reactive oxygen species, which can be associated with a consistent increase in superoxide dismutase, peroxidase and catalase, and a higher ratio of root mass to shoot mass. It is concluded that, such higher capacity in tolerance and adaptation against drought stress under BS relative to both RS and YS could be accounted for more sufficient nutrient provision in soil parental materials and better soil aeration conditions which play a vital role in plant acclimation to water shortage. Our study also revealed that, distribution areas of BS might be preferable for cultivation of Pdeltoides, when compared with those of RS and YS.

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Variability of water supply affected shoot biomass and root depth distribution of four temperate grassland species in monocultures and mixtures
Eamon Haughey, Jennifer C. McElwain and John A. Finn
J Plant Ecol    2020, 13 (5): 554-562.   DOI: 10.1093/jpe/rtaa044
Online available: 21 July 2020

Abstract43)      PDF       Save
Aims

Research on the effects of extreme rainfall events on ecosystem function has primarily focussed on drought or flooding events, which usually include changes to mean or total rainfall, annually or over a season. However, less is known about the effects of increased rainfall variability without change to mean or total amounts. We investigated the effects of increased variation of water supply on shoot and root biomass as well as the distribution of root biomass of four grassland plant species, grown in monoculture and mixture communities.

Methods

Perennial ryegrass (Lolium perenne L., shallow-rooting grass), chicory (Cichorium intybus L., deep-rooting forb), white clover (Trifolium repens L., shallow-rooting legume) and red clover (Trifolium pratense L., deep-rooting legume) were established in mesocosms. Four plants of the same species were grown in monoculture communities and one of each species grown in four-species communities. Water supply was manipulated such that; compared with a baseline level with low variation in water supply, there was a treatment with medium variation (±40%) and another with high variation (±80%). Shoot and root biomass were measured, and vertical root distribution models fitted.

Important Findings

Compared with the low variation treatment, shoot biomass was significantly reduced under high variation for white clover, red clover and four-species communities. Under all conditions, four-species communities produced more shoot and root biomass than predicted by species performance in monoculture (overyielding). Under increased water variation, chicory monocultures allocated a higher proportion of root biomass to deeper soil layers while the total root biomass of white clover monocultures was significantly reduced. These results indicate that increased variability of water supply can negatively affect the shoot and root biomass production of single and multi-species grasslands. There is a need for further investigation of water variation effects on the functioning of multi-species grassland systems at field 

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New development phase of JPE
Wen-Hao Zhang, Bernhard Schmid, Lijuan Liu and Pu Wang
J Plant Ecol    2020, 13 (1): 1-2.   DOI: 10.1093/jpe/rtaa009
Online available: 10 April 2020

Abstract43)      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

Abstract43)      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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Aboveground biomass and seasonal patterns of aboveground net primary productivity in five bamboo species in northern Laos
Singkone Xayalath, Isao Hirota, Shinsuke Tomita and Michiko Nakagawa
J Plant Ecol    2020, 13 (2): 150-156.   DOI: 10.1093/jpe/rtz056
Online available: 23 December 2019

Abstract40)      PDF       Save
Aims

Accurate estimates of bamboo biomass and net primary productivity (NPP) are required to evaluate the carbon sequestration potential of bamboo forests. However, relevant data that are important for climate change mitigation, have rarely been collected in regions outside of East Asia and India. Information on seasonal patterns of NPP and its components will enable the quantification of factors that influence the carbon balance in bamboo forests. In this study, we quantified the aboveground biomass (AGB) and aboveground NPP of five major bamboo species in northern Laos using monthly data collected over a 12-month period.

Methods

All live culms in 10, 2 m × 2 m plots (for one monopodial bamboo species: Indosasa sinica) and 30 clumps per species (for four sympodial bamboo species: Bambusa tuldaCephalostachyum virgatumDendrocalamus membranaceus and Gigantochloa sp.) were numbered and measured at breast height. We set 10 or 20 litter traps per species to collect litterfall. Censuses of dead and recruited culms and litterfall collection were performed once per month for 12 months.

Important Findings

The AGB was highest in I. sinica (59.87 Mg ha−1) and lowest in Cvirgatum (11.54 Mg ha−1), and was mostly below the plausible global range for bamboos (32–256 Mg ha−1). The sympatric distribution of multiple bamboo species at the study sites may have suppressed the AGB in four of the five studied species. The aboveground NPP estimates were between 3.43 and 14.25 Mg ha−1 yr−1; those for D. membranaceus (8.20 Mg ha−1 yr−1) and I. sinica(14.25 Mg ha−1 yr−1) were comparable to mean global estimates for temperate evergreen forests (8.78 Mg ha−1 yr−1) and tropical moist forests (10.56 Mg ha−1yr−1). High culm recruitment rates (15.20–23.39% yr−1) were major contributors to aboveground NPP estimates. Seasonal patterns of aboveground NPP were largely influenced by the phenology of the new culms. In the four sympodial bamboo species, new culms began to emerge following the onset of persistent rainfall, mainly in July and August. However, the sprouting of new culms in the monopodial species I. sinica followed a trend of increasing temperatures, mainly in March and April. Thus, our results indicate that bamboos have considerable potential for sequestering carbon in northern Laos, but that this potential may be affected by climate change.

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Differences in seed properties and germination between native and introduced populations of Triadica sebifera
Jialiang Zhang, Evan Siemann, Baoliang Tian, Wei Huang and Jianqing Ding
J Plant Ecol    2020, 13 (1): 70-77.   DOI: 10.1093/jpe/rtz048
Online available: 24 October 2019

Abstract39)      PDF       Save
Aims

Seeds of many invasive plants germinate more quickly than those of native species, likely facilitating invasion success. Assessing the germination traits and seed properties simultaneously for introduced and native populations of an invasive plant is essential to understanding biological invasions. Here, we used Triadica sebifera as a study organism to examine intraspecific differences in seed germination together with seed characteristics.

Methods

We measured physical (volume, mass, coat hardness and coat thickness of seeds) and chemical (crude fat, soluble protein, sugar, gibberellins [GA] and abscisic acid [ABA] of kernels) properties of T. sebifera seeds collected in 2017 from 12 introduced (United States) populations and 12 native (China) populations and tested their germination rates and timing in a greenhouse experiment in China. Furthermore, we conducted an extra experiment in the United States using seeds collected in 2016 and 2017 to compare the effects of study sites (China vs. United States) and seed collection time (2016 vs. 2017) on seed germination.

Important Findings

Seeds from the introduced range germinated faster than those from the native range. Physical and chemical measurements showed that seeds from the introduced range were larger, had higher GA concentrations and GA:ABA ratio, but lower crude fat concentrations compared to those from the native range. There were no significant differences in seed mass, coat hardness and coat thickness or kernel ABA, soluble protein or sugar concentrations between seeds from introduced vs. native ranges. Germination rates were correlated between United States and China greenhouses but germination rates for populations varied between collection years. Our results suggest that larger seeds and higher GA likely contribute to faster germination, potentially facilitating T. sebifera invasion in the introduced range.

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Climate drives differences in the germination niche of a globally distributed invasive grass
Rebecca A. Fletcher, Kayla M. Varnon and Jacob N. Barney
J Plant Ecol    2020, 13 (2): 195-203.   DOI: 10.1093/jpe/rtz062
Online available: 06 January 2020

Abstract38)      PDF       Save
Aims

Exotic invasive species are often exposed to strong selection pressures in their new ranges that can often lead to substantial intraspecific variation. Population differentiation in the timing of life history events in response to climate gradients is thought to be an important mechanism facilitating the range expansion of many invasive species. For seed producing plants, the timing of seed germination determines the first environmental conditions experienced by newly emerged germinates, and can have important implications for the successful colonization, establishment and spread of invasive plants—though the role of germination in the success of invasive plants remains poorly understood.

Methods

We assessed the variation in seed germination dynamics among 10 populations of the invasive plant Johnsongrass (Sorghum halepense) across its North American distribution, capturing both a temperature and precipitation gradient, and whether that variation is associated with home climate. Seeds were exposed to a wide range of temperatures (11–48°C) and two water availability treatments.

Important Findings

We found that Johnsongrass seeds germinated across a wide range of temperatures, but there was substantial variation among populations in the proportion of seeds that germinated in response to both temperature and water availability. Evidence indicates that as Johnsongrass expanded its range from warmer climates into cooler climates, there was a concurrent shift in the germination temperature niche to cooler temperatures. Our results suggest that the germination of Johnsongrass seeds has adapted to home climate allowing this invader to maximize germination throughout its range, and that this may be an important contributing factor to its invasion into new environments.

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The asymmetric relationships of the distribution of conspecific saplings and adults in forest fragments
Jinliang Liu, Yuchen Zhong, Lei Zhong, Boliang Wei, Shilu Zheng, Yuchu Xie, Yi Jin and Mingjian Yu
J Plant Ecol    2020, 13 (4): 398-404.   DOI: 10.1093/jpe/rtaa026
Online available: 26 May 2020

Abstract38)      PDF       Save
Aims

With the increase of land-use change, habitat fragmentation has become a major factor affecting plant diversity. Generally, when the adult density is high, the survival rate of conspecific saplings may decline and provide more resources and space for other species to maintain a high local species diversity. Therefore, the spatial relationship of conspecific saplings and adults (SRCSA) can regulate plant diversity. However, very few studies have assessed SRCSA within fragmented forests, and we still largely unknown the relationship between SRCSA and species diversity in fragmented landscapes.

Methods

We calculated the mean strength of SRCSA using the spatial distribution data of saplings and adults with a log-transformed hierarchical offset-power model on 27 islands in a land-bridge island system. The higher strength of SRCSA reflects a more negative relationship between the density of conspecific saplings and adults on an island (i.e. the looser pattern of SRCSA). We tested the relationships among island attributes (i.e. island area, the distance to the mainland—MD, and the distance to the nearest island—ND), SRCSA and species diversity.

Important Findings

The strength of SRCSA increased with ND. Meanwhile, the species diversity significantly increased with the strength of SRCSA, and island area and the strength of SRCSA independently explained 26% and 6% of variation of species diversity, respectively, and their interactions explained 8%. Shade-intolerant and low-abundant species showed looser patterns of SRCSA. Our study suggests that SRCSA may have the effect of excluding species with a relatively low abundance in isolated island forests, which illustrates the importance of biotic interactions in maintaining plant diversity in fragmented forests. Our results also emphasize that we should consider forest connectivity when testing the conspecific negative density dependence.

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In the beginning, there was only bare regolith—then some plants arrived and changed the regolith
Jun Zhou, Alejandra Zúñiga-Feest and Hans Lambers
J Plant Ecol    2020, 13 (5): 511-516.   DOI: 10.1093/jpe/rtaa030
Online available: 06 July 2020

Abstract37)      PDF       Save
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Variation in the methods leads to variation in the interpretation of biodiversity–ecosystem multifunctionality relationships
Xin Jing, Case M. Prager, Aimée T. Classen, Fernando T. Maestre, Jin-Sheng He and Nathan J. Sanders
J Plant Ecol    2020, 13 (4): 431-441.   DOI: 10.1093/jpe/rtaa031
Online available: 11 June 2020

Abstract36)      PDF       Save
Aims

Biodiversity is often positively related to the capacity of an ecosystem to provide multiple functions simultaneously (i.e. multifunctionality). However, there is some controversy over whether biodiversity–multifunctionality relationships depend on the number of functions considered. Particularly, investigators have documented contrasting findings that the effects of biodiversity on ecosystem multifunctionality do not change or increase with the number of ecosystem functions. Here, we provide some clarity on this issue by examining the statistical underpinnings of different multifunctionality metrics.

Methods

We used simulations and data from a variety of empirical studies conducted across spatial scales (from local to global) and biomes (temperate and alpine grasslands, forests and drylands). We revisited three methods to quantify multifunctionality including the averaging approach, summing approach and threshold-based approach.

Important Findings

Biodiversity–multifunctionality relationships either did not change or increased as more functions were considered. These results were best explained by the statistical underpinnings of the averaging and summing multifunctionality metrics. Specifically, by averaging the individual ecosystem functions, the biodiversity–multifunctionality relationships equal the population mean of biodiversity-single function relationships, and thus will not change with the number of functions. Likewise, by summing the individual ecosystem functions, the strength of biodiversity–multifunctionality relationships increases as the number of functions increased. We proposed a scaling standardization method by converting the averaging or summing metrics into a scaling metric, which would make comparisons among different biodiversity studies. In addition, we showed that the range-relevant standardization can be applied to the threshold-based approach by solving for the mathematical artefact of the approach (i.e. the effects of biodiversity may artificially increase with the number of functions considered). Our study highlights different approaches yield different results and that it is essential to develop an understanding of the statistical underpinnings of different approaches. The standardization methods provide a prospective way of comparing biodiversity–multifunctionality relationships across studies.

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Characteristics of fungal community structure during the decomposition of mixed foliage litter from Pinus massoniana and broadleaved tree species in southwestern China
Yan Zhang, Xun Li, Danju Zhang, Yu Qin, Yang Zhou, Simeng Song and Jian Zhang
J Plant Ecol    2020, 13 (5): 574-588.   DOI: 10.1093/jpe/rtaa045
Online available: 26 July 2020

Abstract35)      PDF       Save
Aims

The conifer litter is fairly recalcitrant and nutrient poor, and broadleaved litter promotes coniferous litter decomposition by increasing degradable nutrients and promoting microbial metabolism. Mixing Pinus massoniana litter and three broadleaved litters may increase the diversity and abundance of fungal decomposers compared with those in P. massoniana litter and vary depending on the number and proportion of broadleaved species included.

Methods

We analysed the composition and diversity of fungal communities during mixed litter decomposition in southwestern China with 35 treatments (P. massonianaToona sinensisCinnamomum camphora and Sassafras tzumu litter) using Illumina high-throughput sequencing.

Important Findings

The mixed litters increased fungal diversity and richness compared with those in the single-species litter, except in the following treatments: P. massoniana litter accounting for 70%–80% in the P. massoniana + T. sinensisP. massoniana + S. tzumu + T. sinensis and P. massoniana + S. tzumu + C. camphora combinations, and P. massoniana + S. tzumu + C. camphora + T. sinensis combination with small proportion of T. sinensis litter. The diversity and richness of the 7:1:2 combination of P. massoniana + C. camphora + T. sinensis were significantly higher than those in the other treatments. Ascomycota and Basidiomycota were the dominant phyla, and Aspergillus was the most abundant genus. The decomposition of litters from one needleleaf and one broadleaved species (6:4) and one needleleaf species and two broadleaved species (broadleaved litter accounting for 30%–40%) exhibited synergistic interactions throughout the decomposition process, and the relative abundance of fungi that decompose refractory substances increased. The P. massoniana + C. camphora + T. sinensis combination and a 30%–40% broadleaf litter proportion increased fungal diversity and accelerated the decomposition of recalcitrant coniferous litter. Therefore, C. camphora and T. sinensis are a potential candidate species for mixed planting with P. massoniana.

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Genotypic diversity and genotype identity of resident species drive community composition
Věroslava Hadincová, Hana Skálová and Zuzana Münzbergová
J Plant Ecol    2020, 13 (2): 224-232.   DOI: 10.1093/jpe/rtaa004
Online available: 04 February 2020

Abstract34)      PDF       Save
Aims

Species-rich plant communities are more resistant to invasions. In the past decade it was demonstrated that genetic variation also has many ecological effects. In our study we aimed to test whether the patterns of response to the genetic diversity of a resident species differ between colonizing species of different growth forms and whether the response is affected by soil nutrients.

Methods

We established experimental stands of a common grass, Festuca rubra, harbouring three levels of genetic diversity (1, 6 or 18 clonal genotypes, referred to as genotypic diversity) under two soil nutrient levels. In the fourth year after the stands were established, we sowed a mixture of four colonizers into the stands: a stoloniferous legume (Trifolium repens), a broad-leaf tussock grass (Anthoxanthum odoratum), a large-rosette forb (Plantago lanceolata) and a small-rosette forb (Campanula rotundifolia). We observed species establishment and growth over 3 years. We tested whether colonization success depended on genotypic diversity, specific Festuca genotypes, soil nutrients and colonizer growth form.

Important Findings

The colonization success and biomass of the colonizers were significantly affected by the genotypic diversity and the genotype identity of the resident clonal grass. The response, however, differed between the colonizers. The strongest response to the genotypic diversity of the resident species was observed in the tussock grass with a growth form and architecture similar to the resident species. The large-rosette species responded in early stages of growth whereas the stoloniferous legume did not respond at all. The intraspecific genotypic diversity and genotype identity of the resident species play an important role in the assembly of plant communities.

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Linking the spatiotemporal variation of litterfall to standing vegetation biomass in Brazilian savannas
Alan N. Costa, Jeane R. Souza, Karyne M. Alves, Anderson Penna-Oliveira, Geisciele Paula-Silva, Ingrid S. Becker, Kelly Marinho-Vieira, Ana L. Bonfim, Alessandra Bartimachi and Ernane H. M. Vieira-Neto
J Plant Ecol    2020, 13 (5): 517-524.   DOI: 10.1093/jpe/rtaa039
Online available: 16 July 2020

Abstract31)      PDF       Save
Aims

Litterfall at a global scale is affected by climate, edaphic features and vegetation structure, with litter production increasing from grasslands to forests following the rise in standing biomass. However, at landscape scales, the same relationship between litter production and vegetation structure has rarely been studied and comparisons of litterfall patterns between adjacent, structurally distinct communities are lacking. Here, we use a standardized methodology to describe the structural differences among four savanna physiognomies and analyze their relationship with changes in litterfall across the Cerrado.

Methods

We evaluated the woody vegetation structure and composition in 48 sites, equally distributed across four physiognomies and monitored the monthly litter production from April 2014 to March 2015.

Important Findings

Results showed that the density, basal area, cylindrical volume and aboveground biomass of woody vegetation differ among physiognomies, increasing consistently from cerrado ralocerrado típicocerrado denso and cerradão. Indeed, we found a strong and positive relationship between aboveground biomass and annual litter production, with litter yield increasing from 0.9 to 8.4 Mg ha−1 across different physiognomies, following the increment in vegetation structure. Monthly production was seasonal and similar among vegetation types, increasing during the dry season. Leaves comprised the dominant fraction (approx. 85%) and litterfall seasonality primarily resulted from the concentration of leaf shedding during dry months. However, the temporal pattern of litterfall throughout the year showed a gradual reduction in the seasonality from open to closed vegetation types, likely following the decrease of deciduous species abundance in the plant community. Our results showed that changes in vegetation structure may affect spatial and temporal litterfall patterns in different physiognomies, which co-occur across the Cerrado landscape, with potential implications for the overall functioning of this ecosystem. Moreover, these findings highlight the use of standardized methods as essential to correctly compare litterfall patterns among different environments.

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Cumulative cellulolytic enzyme activities and initial litter quality in prediction of cellulose degradation in an alpine meadow of the eastern Tibetan Plateau
Yamei Chen, Yang Liu, Jian Zhang, Wanqin Yang, Changchun Deng and Runlian He
J Plant Ecol    2020, 13 (1): 51-58.   DOI: 10.1093/jpe/rtz044
Online available: 06 September 2019

Abstract31)      PDF       Save
Aims

Plant litter decomposition is a key ecosystem process that determines carbon and nutrient cycling in terrestrial ecosystems. As a main component of litter, cellulose is a vital energy source for the microbes associated with litter decomposition. The important role of cellulolytic enzymes in litter cellulose degradation is well understood, but seasonal patterns of cellulose degradation and whether cumulative enzyme activities and litter quality forecast cellulose degradation in an alpine meadow remain elusive, which limits our understanding of cellulose degradation in herbaceous plant litter.

Methods

A two-year field litterbag experiment involving three dominant species (Ajuga ovalifoliaFestuca wallichanica, and Pedicularis roylei) was conducted in an alpine meadow of the eastern Tibetan Plateau to explore the seasonal patterns of cellulose degradation and how cumulative cellulolytic enzyme activities and initial litter quality impact cellulose degradation.

Important findings

Our study demonstrates that cellulose degraded rapidly and exceeded 50% during the first year, which mainly occurred in the first growing season (31.9%–43.3%). At two years of decomposition, cellulose degradation was driven by cumulative endoglucanase (R= 0.70), cumulative cellobiohydrolase (R= 0.59) and cumulative 1,4-β-glucosidase (R= 0.57). In addition, the concentrations of cellulose, dissolved organic carbon, total phenol, lignin and lignin/N accounted for 52%–78% of the variation in cellulose degradation during the two years of decomposition. The best model for predicting cellulose degradation was the initial cellulose concentration (R= 0.78). The enzymatic efficiencies and the allocation of cellulolytic enzyme activities were different among species. The cellulolytic enzyme efficiencies were higher in the litter of F. wallichanica with relatively lower quality. For the complete cellulose degradation of the leaf litter, A. ovalifolia and F. wallichanicarequired 4-fold and 6.7-fold more endoglucanase activity, 3-fold and 4.5-fold more cellobiohydrolase activity and 1.2-fold and 1.4-fold more 1,4-β-glucosidase activity, respectively, than those required by P. roylei. Our results demonstrated that although microbial activity and litter quality both have significant impacts on cellulose degradation in an alpine meadow, using cellulose concentration to predict cellulose degradation is a good way to simplify the model of cellulose degradation and C cycling during litter decomposition.

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Effect of nitrate supply on the facilitation between two salt-marsh plants (Suaeda salsa and Scirpus planiculmis)
Hua Ma, Li-Juan Cui, Xu Pan, Wei Li, Yu Ning and Jian Zhou
J Plant Ecol    2020, 13 (2): 204-212.   DOI: 10.1093/jpe/rtaa001
Online available: 07 January 2020

Abstract30)      PDF       Save
Aims

In estuarine salt-marshes, nitrate supply and soil salinity, which are known as two main environmental drivers, simultaneously affect the interspecific interactions between plant species. However, to date, their interactive effects on interspecific interactions have not been closely examined for salt-marsh plant species.

Methods

Juvenile plants of Suaeda salsa L. (Chenopodiaceae) and Scirpus planiculmis Fr. (Cyperaceae) were grown in rinsed river sand to conduct a greenhouse experiment with three treatment categories: interspecific interaction (mixed culture or monoculture), three salinity levels (1, 50 and 100 mmol L−1) and three nitrate levels (0.5, 5 and 10 mmol L−1). First, height and biomass of all plants were measured. Then, the growth data, relative interaction index and competitive important index of the two species were analyzed.

Important Findings

The interspecific interactions between S. salsa and S. planiculmis were facilitation across the salinity gradients. The promotion of S. salsa growth with high nitrate supply did not enhance the facilitative effect of the species, especially at low salinity. However, high nitrate supply significantly shifted the interspecific interactions of S. planiculmisfrom facilitation to competition at high salinity. Our results suggest that excessive nitrate application changes the prediction of the stress-gradient hypothesis along a salinity gradient, leading to collapse of the two species coexistence in the salt-marshes. These findings make a contribution to the understanding of how S. salsaand S. planiculmis, as well as salt-marsh communities, respond to the human modification of estuarine nutritional levels.

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Growth, phenology and N-utilization by invasive populations of Gunnera tinctoria
Maurício Cruz Mantoani , Alberto Benavent González, Leopoldo García Sancho and Bruce Arthur Osborne
J Plant Ecol    2020, 13 (5): 589-600.   DOI: 10.1093/jpe/rtaa047
Online available: 21 July 2020

Abstract30)      PDF       Save
Aims

Gunnera tinctoria is an unusual N-fixing plant species that has become invasive worldwide, generally in environments with a low evaporative demand and/or high rainfall. Amongst the many mechanisms that may explain its success as an introduced species, a contrasting phenology could be important but this may depend on an ability to grow and utilize nutrients under sub-optimal conditions. We examined whether G. tinctoria has an advantage in terms of a contrasting phenology and N-fixing capability, in comparisons with Juncus effusus, the native species most impacted by G. tinctoria invasions.

Methods

We made phenological assessments on a weekly or bi-weekly basis on long-established populations on Achill Island, Ireland, during 2016–2017. Data on leaf and inflorescence number, total leaf area, light interception and above-ground biomass were collected alongside measurements of soil temperature, moisture and oxidation–reduction potential. The significance of N-fixing ability for supporting seasonal growth was assessed using δ 15N isotopic assessments, together with in situ acetylene reduction measurements.

Important Findings

The timing of the initiation of growth of G. tinctoria and J. effusus varied between 2016 and 2017, with the earlier emergence and expansion of leaves of G. tinctoria, and the largest above-ground biomass associated with higher water availability. The early growth of G. tinctoria was dependent on preformed structures, with maximum canopy development occurring in late May, prior to that of J. effusus. Whilst N-fixation was observed in March, this made a more significant contribution to growth during the later stages of canopy development. Based on δ 15N isotopic analyses, early growth was predominantly associated with N-remobilization from the rhizomes, whilst seedlings were largely reliant on N-fixation. This emphasizes the importance of nutrient mobilization for early growth and shows that the importance of an N-fixing capability may vary developmentally, as well as during different stages of the invasion process.

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Impact of forest fire on soil seed bank composition in Himalayan Chir pine forest
Bobbymoore Konsam, Shyam S. Phartyal and Nagendra P. Todaria
J Plant Ecol    2020, 13 (2): 177-184.   DOI: 10.1093/jpe/rtz060
Online available: 27 December 2019

Abstract28)      PDF       Save
Aims

To explain how plant community copes with a recurring anthropogenic forest fire in Himalayan Chir pine forest, it is important to understand their postfire regeneration strategies. The primary aim of the study was to know: (i) how fire impact soil seed bank composition and (ii) how much soil seed bank composition differs with standing vegetation after the forest fire.

Methods

Soil samples were collected from burned and adjoining unburned sites in blocks using three layers down to 9 cm depth immediately after a forest fire and incubated in the net-house for seedling emergence. Same sites were revisited during late monsoon/early autumn season to know the species composition of standing vegetation recovered after a forest fire.

Important Findings

Soil contained viable seeds of >70 species. The average seed bank density was 8417 and 14 217 seeds/m2 in the burned and unburned site, respectively. In both sites, it decreased with increasing soil depth. Overall fire had no significant impact on seed density; however, taking individual layers into consideration, fire had a significant impact on seed density only in the uppermost soil layer. The species richness of soil seed bank and standing vegetation was 73 and 100, respectively (with 35 shared species), resulting in a similarity of about 40%. In contrast, >80% species in soil seed bank was found similar between burned and unburned sites. Further, there were no significant differences in species richness of standing vegetation in burned (87 spp.) and unburned (78 spp.) sites. Our results showed that fire had an insignificant impact on soil seed bank composition and restoration potential of a plant species from seeds. The understory herb and shrub plant community’s ability to form a fire-resistant viable soil seed bank and capable to recover in the postfire rainy season, explains how they reduce the risk of recurring fire damage in maintaining their population.

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The assembly of plant-patch networks in Mediterranean alpine grasslands
David S. Pescador, José María Iriondo, Gianalberto Losapio and Adrián Escudero
J Plant Ecol    2020, 13 (3): 273-280.   DOI: 10.1093/jpe/rtaa011
Online available: 14 March 2020

Abstract28)      PDF       Save
Aims

Harsh environmental conditions in alpine ecosystems shape vegetation structure into patches, where many different plant species cluster and grow together. Yet, which factors are important for the structure and dynamics of such plant–patch networks remains poorly understood. We aim to assess which and how environmental and biotic factors predict the assembly of plant–patch networks along a mountain range.

Methods

We examined the distribution of plant species in more than 5500 vegetation patches in 37 Mediterranean alpine grasslands distributed along a 500 m altitudinal gradient (National Park of Sierra Guadarrama, Spain). We established a plant–patch network for each grassland community and analyzed how nestedness and modularity vary with environmental (altitude, insolation and soil conditions) and biotic factors (number of species per plot, mean patch area and total pasture area).

Important Findings

Plant–patch networks showed consistent, non-random patterns characterized by a nested, but not modular, structure, which suggests that positive associations among co-occurring specialists promote their growth within patches as subsets of a pool with more generalist species. Both nestedness and modularity of plant–patch networks varied among grasslands. Specifically, nestedness decreased with increasing species per plot and increased with mean patch area, while it was independent of environmental variables; modularity increased with increasing pasture area and species per plot. The negative relationship between species per plot and nested patterns may be linked to the restricted number of species that can coexist within the same patch at a given size. Moreover, the positive relationship between patch size and nestedness indicates that the growth of rare plant species within vegetation patches occupied by more abundant species is facilitated in bigger rather than smaller patches. Furthermore, these results indicate that the nested assembly of vegetation patches may be independent of abiotic conditions. These findings suggest that large and unfragmented vegetation patches are fundamental for the maintenance of plant diversity in alpine grasslands. Looking at species distribution at fine spatial scales may shed new light on the biotic processes underlying plant network assembly and provide novel ways for conserving biodiversity.

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