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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
Abstract353)      PDF (2852KB)(227)       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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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
Abstract310)      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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The response of soil respiration to different N compounds addition in a saline–alkaline grassland of northern China
Huajie Diao, Xiaopeng Chen, Ge Wang, Qiushi Ning, Shuya Hu, Wei Sun, Kuanhu Dong and Changhui Wang
J Plant Ecol    2022, 15 (5): 897-910.   DOI: 10.1093/jpe/rtac006
Abstract114)      PDF (4162KB)(140)       Save

The increase in atmospheric nitrogen (N) deposition has profound effects on soil respiration (SR). However, the responses of SR to the addition of different N compounds, particularly in saline–alkaline grasslands remain unclear. A 3-year controlled field experiment was conducted to investigate the responses of SR to different N compounds (NH4NO3, (NH4)2SO4 and NH4HCO3) during the growing seasons in a saline–alkaline grassland located in the agro-pastoral ecotone of northern China. Our results demonstrated that SR showed a bimodal pattern and a significant interannual difference that was regulated by air or soil temperature and precipitation. Nitrogen addition had a significant effect on SR, and the effect of N addition on SR varied yearly, which was related to seasonal precipitation. The mean SR across 3 years (2017–2019) was increased by 19.9%, 13.0% and 16.6% with the addition of NH4NO3, (NH4)2SO4 and NH4HCO3, respectively. The highest effect of NH4NO3 addition on SR across 3 years was ascribed to the highest aboveground net primary production, belowground net primary production (BNPP) and soil NO3 concentrations. SR (C loss) was significantly increased while plant productivity (C input) did not significantly change under NH4HCO3 addition, indicating a decrease in C sequestration. In addition, BNPP was the main direct factor influencing SR in this saline–alkaline grassland, and soil salinization (e.g. soil base cations and pH) indirectly affected SR through soil microorganisms. Notably, NH4NO3 addition overestimated the response of SR to N addition, and different N compounds should be considered, especially in saline–alkaline grassland.

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Crown and leaf traits as predictors of subtropical tree sapling growth rates
Ying Li, Wenzel Kröber, Helge Bruelheide, Werner Härdtle, Goddert von Oheimb
J Plant Ecol    2017, 10 (1): 136-145.   DOI: 10.1093/jpe/rtw041
Abstract349)      PDF       Save
Aims Growth rates of plants are driven by factors that influence the amount of resources captured and the efficiency of resource use. In trees, the amount of light captured and the efficiency of light use strongly depends on crown characteristics and leaf traits. Although theory predicts that both crown and leaf traits affect tree growth, few studies have yet to integrate these two types of traits to explain species-specific growth rates. Using 37 broad-leaved tree species of subtropical forests in SE China, we investigated how interspecific differences in wood volume growth rates were affected by crown and leaf traits. We tested the hypotheses that (i) larger crown dimensions promote growth rates, (ii) species-specific growth rates are positively related to leaf stomatal conductance, leaf water potential and leaf chemical components, and negatively related to leaf C/N and leaf toughness and (iii) the two sets of traits better explain growth rates in combination than either alone.
Methods Our study was conducted in a large-scale forest Biodiversity and Ecosystem Functioning experiment in China (BEF-China), located in a mountainous region in Jiangxi Province. We related 17 functional traits (two crown dimension and three crown structure traits; six physiological and six morphological leaf traits) to the mean annual growth rate of wood volume of young trees of the studied species. Interrelationships between crown and leaf traits were analyzed using principal component analysis. Simple linear regression analysis was used to test the effect of each trait separately. We used multiple regression analysis to establish the relationship of growth rate to each set of traits (crown traits, physiological and morphological leaf traits) and to the combination of all types of traits. The coefficients of determination (R 2 adj) of the best multiple regression models were compared to determine the relative explanatory power of crown and leaf traits and a combination of both.
Important findings The species-specific growth rates were not related to any of the single crown traits, but were related positively to leaf stomatal conductance and leaf water potential individually, and negatively to leaf toughness, with approximately 13% variance explained by each of the traits. Combinations of different crown traits did not significantly explain the species-specific growth rates, whereas combinations of either physiological or morphological leaf traits explained 24% and 31%, respectively. A combination of both crown and leaf traits explained 42% of variance in species-specific growth rates. We concluded that sets of traits related to carbon assimilation at the leaf-level and to overall amount of leaves exposed at the crown-level jointly explained species-specific growth rates better than either set of traits alone.
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Plant diversity and ecological intensification in crop production systems
Rob W. Brooker, Cathy Hawes, Pietro P. M. Iannetta, Alison J. Karley, Delphine Renard
J Plant Ecol    2023, 16 (6): 0-rtad015.   DOI: 10.1093/jpe/rtad015
Abstract61)      PDF (650KB)(114)       Save
Ecological intensification (EI) is the enhancement of ecosystem services to complement or substitute for the role of anthropogenic inputs in maintaining or increasing yields. EI has potential to increase farming’s environmental sustainability, e.g. reducing environmentally harmful management activities while sustaining yields. EI is based upon ecological processes which in turn are influenced by biodiversity. We review how biodiversity, particularly vascular plant diversity, can regulate ecosystem processes relevant to EI at multiple spatial scales. At an individual plant genotype level, complementarity in functional traits has a direct impact on productivity. At in-field, population level, mixtures of crop types confer resilience to minimize the risk of pest and disease incidence and spread. Scaling up to the field level, a diversity of non-crop plants (i.e. weeds) provides resources necessary for in-field functional processes, both below ground (carbon inputs, decomposition) and above ground (resource continuity for pollinators and natural enemies). At the landscape scale, mosaics of semi-natural and managed vegetation provide buffers against extreme events through flood and drought risk mitigation, climate amelioration and pest population regulation. Overall this emphasizes the importance of heterogeneity across scales in maintaining ecosystem functions in farmland. Major research challenges highlighted by our review include the need: to better integrate plant functional diversity (from traits to habitat scales) into cropping system design; to quantify the (likely interactive) contribution of plant diversity for effective EI relative to other management options; and to optimize through targeted management the system function benefits of biodiversity for resilient, efficient and productive agroecosystems.
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Using intraspecific variation of functional traits and environmental factors to understand the formation of nestedness patterns of a local forest community
Weitao Wang, Yun Jiang, Yongfa Chen, Wenqi Luo, Dong He, Youshi Wang, Chengjin Chu, Buhang Li
J Plant Ecol    2022, 15 (6): 1185-1198.   DOI: 10.1093/jpe/rtac039
Abstract111)      PDF (1251KB)(111)       Save
The concept of nestedness originated from the field of biogeography decades ago and has been widely used in metacommunities and biological interaction networks, but there is still a lack of research within local communities. Moreover, studies on nestedness usually rarely incorporate the functional traits of the species and the environmental characteristics of the sites. In this study, we constructed a species presence–absence matrix of a 50-ha forest plot, used the simulated annealing algorithm to reveal the maximum nested structure and further tested the significance of nestedness patterns by constructing null ensembles. The nested ranks were used to represent the orders of species and quadrats in the maximum nestedness matrix. The regression tree analysis was used to reveal the relationships of nested ranks with environmental factors and functional traits. We found that the co-occurrence pattern of local plant communities was significantly nested. The regression tree results showed that the nested ranks of quadrats were determined by soil available phosphorus, soil water content, soil organic carbon and soil pH. Intraspecific variation of functional traits, including leaf C, leaf pH, leaf dry matter content and maximum photosynthetic rate rather than means of functional traits, provided a better explanation for the formation of species’ nested ranks. Understanding the causes of species and quadrats nested ranks provides novel lens and useful insights into ecological processes underlying nestedness, and further improves our knowledge of how local plant communities are assembled.
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Carbon–water coupling and its relationship with environmental and biological factors in a planted Caragana liouana shrub community in desert steppe, northwest China
Ling-Tong Du, Long-Long Ma, Hai-Zhu Pan, Cheng-Long Qiao, Chen Meng, Hong-Yue Wu, Jing Tian and Hong-Yi Yuan
J Plant Ecol    2022, 15 (5): 947-960.   DOI: 10.1093/jpe/rtac064
Abstract75)      PDF (3778KB)(109)       Save

The carbon and water cycle, an important biophysical process of terrestrial ecosystems, is changed by anthropogenic revegetation in arid and semiarid areas. However, there is still a lack of understanding of the mechanisms of carbon and water coupling in intrinsic ecosystems in the context of human activities. Based on the CO2 and H2O flux measurements of the desert steppe with the planted shrub Caragana liouana, this study explored the carbon and water flux coupling of the ecosystem by analyzing the variations in gross primary productivity (GPP), evapotranspiration (ET) and water use efficiency (WUE) and discussing the driving mechanisms of biological factors. The seasonal variation in climate factors induced a periodic variation pattern of biophysical traits and carbon and water fluxes. The GPP and ET fluctuated in seasons, but the WUE was relatively stable in the growing season. The GPP, ET and WUE were significantly driven by global radiation (Rg), temperature (Ta and Ts), water vapor pressure deficit, leaf area index and plant water stress index (PWSI). However, Rg, temperature and PWSI were the most important factors regulating WUE. Rg and temperature directly affected WUE with a positive effect but indirectly inhibited WUE by rising PWSI. Plant water stress inhibited photosynthesis and transpiration of the planted shrub community in the desert steppe. When the plant water stress exceeded a threshold (PWSI >0.54), the WUE would decrease since the GPP responded more quickly to the plant water stress than ET. Our findings suggest that policies related to large-scale carbon sequestration initiatives under afforestation must first fully consider the status of water consumption and WUE.

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Coculturing rice with aquatic animals promotes ecological intensification of paddy ecosystem
Zi-Jun Ji, Lu-Feng Zhao, Tao-Jie Zhang, Ran-Xin Dai, Jian-Jun Tang, Liang-Liang Hu, Xin Chen
J Plant Ecol    2023, 16 (6): 0-rtad014.   DOI: 10.1093/jpe/rtad014
Abstract84)      PDF (370KB)(108)       Save
Species coculture can increase agro-biodiversity and therefore constitutes an ecological intensification measure for agriculture. Rice-aquatic animal coculture, one type of species coculture, has been practiced and researched widely. Here, we review recent studies and present results of a quantitative analysis of literature on rice-aquatic animal coculture systems. We address three questions: (i) can rice yield and soil fertility be maintained or increased with less chemical input through rice-aquatic animal coculture? (ii) how do aquatic animals benefit the paddy ecosystem? (iii) how can coculture be implemented for ecological intensification? Meta-analysis based on published papers showed that rice-aquatic animal cocultures increased rice yield, soil organic carbon and total nitrogen and decreased insect pests and weeds compared with rice monocultures. Studies also showed that rice-aquatic animal cocultures reduced pesticide and fertilizer application compared with rice monocultures. Rice plants provide a beneficial environment for aquatic animals, leading to high animal activities in the field. Aquatic animals, in turn, help remove rice pests and act as ecological engineers that affect soil conditions, which favor the growth of rice plants. Aquatic animals promote nutrient cycling and the complementary use of nutrients between rice and aquatic animals, which enhances nutrient-use efficiency in the coculture. To generate beneficial outcomes, how to develop compatible partnerships between rice and aquatic animals, and compatible culturing strategies for coculture systems are the key points. Investigating which traits of aquatic animals and rice varieties could best match to create productive and sustainable coculture systems could be one of the future focuses.
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Asian tropical forests assimilating carbon under dry conditions: water stress or light benefits?
Lian-Yan Yang, Rui Yu, Jin Wu, Yongjiang Zhang, Yoshiko Kosugi, Natalia Restrepo-Coupe, Afredo Huete, Jie Zhang, Yu-Hai Liu, Xiang Zhang, Wen-Jie Liu, Jun-Fu Zhao, Jiye Zeng, Qing-Hai Song, Ya-Jun Chen, Liang Song, Zheng-Hong Tan
J Plant Ecol    2023, 16 (3): 0-rtac106.   DOI: 10.1093/jpe/rtac106
Abstract75)      PDF (3169KB)(107)       Save
Tropical forests are characterized by vast biomass, complex structures and mega-biodiversity. However, the adaptation processes of these forests to seasonal water availability are less understood, especially those located in the monsoonal and mountainous regions of tropical Southeast Asia. This study used four representative tropical forests spanning from 2° N to 22° N in continental Southeast Asia to address dry-condition photosynthesis at the seasonal scale. We first provided novel and reliable estimations of ecosystem photosynthesis (gross primary production; GPP) seasonality at all four sites. As expected, both evergreen and deciduous seasonal forests exhibited higher GPPs during the rainy season than during the dry season. A bimodal pattern corresponding to solar radiation occurred in the GPP of the perhumid forest. The surface conductance (Gs) was consistently lower both in the dry season and during dry spells (DSPs) than during the wet season and non-dry spells. However, this did not prevent GPP from increasing alongside increasing irradiance in the perhumid forest, suggesting that other ecosystem physiological properties, for example, the light-saturated photosynthetic rate, must have increased, thus surpassing the effect of Gs reduction. Thus, perhumid forests could be defined as light-demanding ecosystems with regard to their seasonal dynamics. Seasonal forests are water-stressed ecosystems in the dry season, as shown by the reductions in GPP, Gs and related ecosystem physiological properties. At all four forest sites, we observed a lack of consistent adaptive strategy to fit the water seasonality due to the diversity in leaf phenology, soil nutrient availability, root depth and other potential factors.
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Interactive effects of plant density and nitrogen availability on the biomass production and leaf stoichiometry of Arabidopsis thaliana
Zheng-Bing Yan, Di Tian, Han-Yue Huang, Yuan-Feng Sun, Xing-Hui Hou, Wen-Xuan Han, Ya-Long Guo, Jing-Yun Fang
J Plant Ecol    2023, 16 (3): 0-rtac101.   DOI: 10.1093/jpe/rtac101
Abstract62)      PDF (1309KB)(106)       Save
Plant density and nitrogen (N) availability influence plant survival and nutrient use strategies, but the interaction between these two factors for plant growth and the balance of elements remains poorly addressed. Here, we conducted experimental manipulations using Arabidopsis thaliana, with the combination of four levels of plant density and four levels of N addition, and then examined the corresponding changes in plant biomass production (indicated by total plant biomass and biomass partitioning) and nutrient use strategies (indicated by leaf N and phosphorus (P) stoichiometry). The biomass-density relationship was regulated by N availability, with a negative pattern in low N availability but an asymptotic constant final yield pattern at high N availability. Excessive N addition reduced plant growth at low plant density, but this effect was alleviated by increasing plant density. The root to shoot biomass ratio increased with plant density at low N availability, but decreased at high N availability. N availability was more important than plant density in regulating leaf N and P stoichiometry, with the increasing leaf N concentration and decreasing leaf P concentration under increasing N addition, resulting in a negative scaling relationship between these two elemental concentrations. Our results show that N availability and plant density interactively regulate plant biomass production and leaf stoichiometry of A. thaliana, and highlight that the interactive effects of these two factors should be considered when predicting plant growth behaviour under intraspecific competitive environments in the context of nutrient changes.
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Spatial patterns and determinants of Moraceae richness in China
Hua-Feng Wang, Xiaoting Xu, Xia-Lan Cheng, Yunpeng Liu, Ao Luo, Tong Lyu, Wen-Long Wang, Mir Muhammad Nizamani, Zhiheng Wang
J Plant Ecol    2022, 15 (6): 1142-1153.   DOI: 10.1093/jpe/rtac025
Abstract143)      PDF (1074KB)(105)       Save
Understanding large-scale patterns of biodiversity and their drivers remains central in ecology. Many hypotheses have been proposed, including hydrothermal dynamic hypothesis, tropical niche conservatism hypothesis, Janzen’s hypothesis and a combination model containing energy, water, seasonality and habitat heterogeneity. Yet, their relative contributions to groups with different lifeforms and range sizes remain controversial, which have limited our ability to understand the general mechanisms underlying species richness patterns. Here we evaluated how lifeforms and species range sizes influenced the relative contributions of these three hypotheses to species richness patterns of a tropical family Moraceae. The distribution data of Moraceae species at a spatial resolution of 50 km × 50 km and their lifeforms (i.e. shrubs, small trees and large trees) were compiled. The species richness patterns were estimated for the entire family, different life forms and species with different range sizes separately. The effects of environmental variables on species richness were analyzed, and relative contributions of different hypotheses were evaluated across life forms and species range size groups. The species richness patterns were consistent across different species groups and the species richness was the highest in Sichuan, Guangzhou and Hainan provinces, making these provinces the hotspots of this family. Climate seasonality is the primary factor in determining richness variation of Moraceae. The best combination model gave the largest explanatory power for Moraceae species richness across each group of range size and life forms followed by the hydrothermal dynamic hypothesis, Janzen’s hypothesis and tropical niche conservatism hypothesis. All these models has a large shared effects but a low independent effect (< 5%), except rare species. These findings suggest unique patterns and mechanisms underlying rare species richness and provide a theoretical basis for protection of the Moraceae species in China.
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Community-level predictions in a megadiverse hotspot:comparison of stacked species distribution models to forest inventory data
Victor Pereira Zwiener, Valéria Andressa Alves
J Plant Ecol    2023, 16 (3): 0-rtac099.   DOI: 10.1093/jpe/rtac099
Abstract76)      PDF (1220KB)(104)       Save
Given the current scenario of climate change and anthropogenic impacts, spatial predictions of biodiversity are fundamental to support conservation and restoration actions. Here, we compared different stacked species distribution models (S-SDMs) to forest inventories to assess if S-SDMs capture emerging properties and geographic patterns of species richness and composition of local communities in a biodiversity hotspot. We generated SDMs for 1499 tree species sampled in 151 sites across the Atlantic Forest. We applied four model stacking approaches to reconstruct the plant communities: binary SDMs (bS-SDMs), binary SDMs cropped by minimum convex polygons (bS-SDMs-CROP), stacked SDMs constrained by the observed species richness (cS-SDMs) and minimum convex polygons of species occurrences (MCPs). We compared the stacking methods with local communities in terms of species richness, composition, community prediction metrics and components of beta diversity—nestedness and turnover. S-SDMs captured general patterns, with bS-SDMs-CROP being the most parsimonious approach. Species composition differed between local communities and all stacking methods, in which bS-SDMs, bS-SDMs-CROP and MCPs followed a nested pattern, whereas species turnover was most important in cS-SDMs. S-SDMs varied in terms of performance, omission and commission errors, leading to a misprediction of some vulnerable, endangered and critically endangered species. Despite differing from forest inventory data, S-SDMs captured part of the variation from local communities, representing the potential species pool. Our results support the use of S-SDMs to endorse biodiversity synthesis and conservation planning at coarse scales and warn of potential misprediction at local scales in megadiverse regions.
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Moss C, N, P and K stoichiometry and their relationships are related to soil nutrients and environment in a temperate desert of central Asia
Yong-Gang Li, Xiao-Bing Zhou, Yongxing Lu, Yuan-Ming Zhang
J Plant Ecol    2023, 16 (3): 0-rtac070.   DOI: 10.1093/jpe/rtac070
Abstract144)      PDF (1442KB)(95)       Save
Previous studies showed that moss stoichiometric characteristics were influenced by moss patch size, shrubs and the environment in the desert. The study of moss stoichiometry in different spatial distribution areas is crucial for an understanding of growth and adaptation strategy of the mosses. In this study, the dominant moss (Syntrichia caninervis) of biological soil crusts and soil under the moss patches in the Gurbantunggut Desert were selected to determine their stoichiometry in different dunes and sites. Moss stoichiometry and soil available nutrients were significantly influenced by different distribution areas except for moss C. The Naboveground vs. Nbelowground' Paboveground vs. Pbelowground and Kaboveground vs. Kbelowground scaling exponents of moss were 0.251, 0.389 and 0.442, respectively. The N vs. P scaling exponents were 0.71, 0.84 in above- and below-ground parts of moss. Moss stoichiometry was disproportionately distributed in the above-ground and below-ground parts. Moreover, moss N, P and K elements were influenced by mean annual precipitation (MAP), longitude and soil nutrients. The nutrients of moss were affected by spatial distribution, mean annual temperature (MAT), MAP and soil nutrients. The growth of moss was limited by N element in the temperate desert. This study provides the stoichiometric characteristics of C, N, P and K of moss at different spatial scales and explores their relationships with environmental variables, which can help understand nutrient patterns and utilization strategy of N, P and K, and their potential responses to global climate changes in desert.
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Dominant species play a leading role in shaping community stability in the northern Tibetan grasslands
Ge Hou, Peili Shi, Tiancai Zhou, Jian Sun, Ning Zong, Minghua Song, Xianzhou Zhang
J Plant Ecol    2023, 16 (3): 0-rtac110.   DOI: 10.1093/jpe/rtac110
Abstract75)      PDF (817KB)(92)       Save
Dominant species may strongly influence biotic conditions and interact with other species, and thus are important drivers of community dynamics and ecosystem functioning, particularly in the stressed environment of alpine grasslands. However, the effects of dominant species on the community stability of different ecosystems remain poorly understood. We examined the mechanisms underlying temporal stability (2014-2020 year) of aboveground productivity and community stability in four alpine grasslands (alpine meadow, alpine meadow steppe, alpine steppe and alpine desert steppe) of the northern Tibetan with different species composition and dominance. Our results showed that community stability was significantly higher in the alpine meadow than in the other three types of grasslands. This difference was mainly attributed to the higher compensatory effect and selection effect in the alpine meadows. Furthermore, dominant species strongly affected community stability by increasing dominant species stability and species asynchrony. However, species richness had little effect on community stability. Our findings demonstrate that dominant species, as foundation species, may play leading roles in shaping community stability in the alpine grasslands, highlighting the importance of conserving dominant species for stable ecosystem functioning in these fragile ecosystems under increasing environmental fluctuations.
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Reduction in leaf size at higher altitudes across 39 broad-leaved herbaceous species on the northeastern Qinghai-Tibetan Plateau
Xinran Ke, Huixing Kang, Yanhong Tang
J Plant Ecol    2022, 15 (6): 1227-1240.   DOI: 10.1093/jpe/rtac051
Abstract122)      PDF (1840KB)(91)       Save

Leaf size varies conspicuously within and among species under different environments. However, it is unclear how leaf size would change with elevation, whether there is a general elevational pattern, and what determines the altitudinal variation of leaf size. We thus aimed to address these questions by focusing on the broad-leaved herbaceous species at high altitudes on the northeastern Qinghai-Tibetan Plateau. We measured the leaf size, leaf length, leaf width and leaf mass per area for 39 broad-leaved herbaceous species inhabited in the open areas along two mountain slopes from 3200 to 4400 m at the Lenglongling and the Daban Mountain, the northeastern Qinghai-Tibetan Plateau. We analyzed the altitudinal patterns in leaf size in relation to leaf inclination and leaf surface features, and applied a leaf energy balance model to discuss the underlying mechanisms. Leaf size decreased significantly at higher altitudes. The altitudinal reduction of leaf size was mainly attributed to the reduction of leaf length, and differed in different species, and in leaves with different inclination and leaf surface features. A leaf energy balance model with local environmental measurements demonstrates that leaf temperature tracks air temperature more closely in small than in large leaves, and that the leaf-size impact is stronger at higher latitudes. Based on the observational findings, we propose that the distribution upper-limit for broad-leaved herbaceous species would be at an elevation of about 5400 m on the northeastern Qinghai-Tibetan Plateau.

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Ecological intensification of agriculture through biodiversity management: introduction
Bernhard Schmid, Christian Schöb
J Plant Ecol    2023, 16 (6): 0-rtad018.   DOI: 10.1093/jpe/rtad018
Abstract68)      PDF (195KB)(88)       Save
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Correction of leaf nutrient resorption efficiency on the mass basis
Meixia Zhang, Yan Luo, Qingquan Meng, Wenxuan Han
J Plant Ecol    2022, 15 (6): 1125-1132.   DOI: 10.1093/jpe/rtac041
Abstract94)      PDF (571KB)(85)       Save

Nutrient resorption is a crucial mechanism for plant nutrient conservation, but most previous studies did not consider the leaf-mass loss during senescence due to lack of measured data. This would lead to an underestimation of nutrient resorption efficiency (NuRE), or calculating NuRE of various species based on the average mass loss at plant-functional-group level in the literature, thus affecting its accuracy. Here we measured the leaf-mass loss to correct NuRE with the species-specific mass loss correction factor (MLCF), so as to foster a more accurate calculation of the nutrient fluxes within and between plants and the soil. Green leaves and senesced leaves were collected from 35 dominant woody plants in northern China. Mass of green and senesced leaves were measured to calculate the MLCF at species level. The MLCF was reported for each of the 35 dominant woody plants in northern China. These species averagely lost 17% of the green-leaf mass during leaf senescence, but varied greatly from 1.3% to 36.8% mass loss across the 35 species, or 11.7% to 19.6% loss across the functional types. Accordingly, the MLCF varied from 0.632 to 0.987 across the 35 species with an average value 0.832. The NuRE corrected with MLCF was remarkably increased on the whole (e.g. both the average nitrogen and phosphorus NuRE became about 9% higher, or more accurate), compared with the uncorrected ones, especially in the case of low resorption efficiencies. Our field data provide reliable references for the MLCF of plants in related regions at both species and functional-type levels, and are expected to promote more accurate calculations of NuRE.

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Variability in evapotranspiration shifts from meteorological to biological control under wet versus drought conditions in an alpine meadow
Mingjie Xu, Tingting An, Zhoutao Zheng, Tao Zhang, Yangjian Zhang and Guirui Yu
J Plant Ecol    2022, 15 (5): 921-932.   DOI: 10.1093/jpe/rtac033
Abstract79)      PDF (2078KB)(84)       Save

The Tibetan Plateau is generally referred to as the Chinese water tower, and evapotranspiration (ET) affects the water budget and stability of alpine meadows on the Tibetan Plateau. However, its variability and controlling mechanisms have not been well documented under the drier conditions induced by global warming. Therefore, this study aimed to clarify whether meteorological or biological factors primarily affected the variability in ET under contrasting water conditions in the alpine meadow ecosystem on the Tibetan Plateau. Based on 6-year (2013–2018) eddy covariance observations and the corresponding meteorological and biological data, linear perturbation analyses were employed to isolate the contributions of meteorological and biological factors to the variability in evapotranspiration (δET). The results showed that δET was mainly driven by meteorological factors in wet peak seasons (July and August), and was dominated by net radiation (Rn) and air temperature (Ta), indicating that the inadequate available energy is the factor limiting ET. However, the dominant factors affecting δET shifted from meteorological to biological in dry peak seasons when the canopy stomatal conductance (gs) and leaf area index were dominant. At this point, the ecosystem was limited by the water conditions. These results provide empirical insights into how meteorological and biological factors regulate variability in ET under contrasting water conditions. These findings can further improve our understanding of water cycle processes and can help effectively manage water resources in alpine meadow ecosystems under future climate change 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
Abstract184)      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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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
Abstract181)      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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Seasonal and interannual variations of ecosystem photosynthetic characteristics in a semi-arid grassland of Northern China
Cuihai You, Yanbing Wang, Xingru Tan, Bingwei Zhang, Tingting Ren, Boyu Chen, Mengzhen Xu and Shiping Chen
J Plant Ecol    2022, 15 (5): 961-976.   DOI: 10.1093/jpe/rtac065
Abstract107)      PDF (4131KB)(82)       Save

The ecosystem apparent quantum yield (α), maximum rate of gross CO2 assimilation (Pmax) and daytime ecosystem respiration rate (Rd), reflecting the physiological functioning of ecosystem, are vital photosynthetic parameters for the estimation of ecosystem carbon budget. Climatic drivers may affect photosynthetic parameters both directly and indirectly by altering the response of vegetation. However, the relative contribution and regulation pathway of environmental and physiological controls remain unclear, especially in semi-arid grasslands. We analyzed seasonal and interannual variations of photosynthetic parameters derived from eddy-covariance observation in a typical semi-arid grassland in Inner Mongolia, Northern China, over 12 years from 2006 to 2017. Regression analyses and a structural equation model (SEM) were adopted to separate the contributions of environmental and physiological effects. The photosynthetic parameters showed unimodal seasonal patterns and significantly interannual variations. Variations of air temperature (Ta) and soil water content (SWC) drove the seasonal patterns of photosynthetic parameters, while SWC predominated their interannual variations. Moreover, contrasting with the predominant roles of Ta on α and Rd, SWC explained more variance of Pmax than Ta. Results of SEM revealed that environmental factors impacted photosynthetic parameters both directly and indirectly through regulating physiological responses reflected by stomatal conductance at the canopy level. Moreover, leaf area index (LAI) directly affected α, Pmax and Rd and dominated the variation of Pmax. On the other hand, SWC influenced photosynthetic parameters indirectly through LAI and canopy surface conductance (gc). Our findings highlight the importance of physiological regulation on the photosynthetic parameters and carbon assimilation capacity, especially in water-limited grassland ecosystems.

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The abundance effect on network nestedness is stronger for parasitic than herbivory interactions
Bin Lan, Xiaoli Hu, Ying Wang, Shucun Sun
J Plant Ecol    2022, 15 (6): 1133-1141.   DOI: 10.1093/jpe/rtac052
Abstract87)      PDF (587KB)(82)       Save
It has been suggested that the importance of network architecture to species diversity and stability should be based on preference networks (comprised of niche differentiations), rather than observational networks, because species abundance may significantly affect interaction frequencies. Considering that resource abundance is usually greater for herbivores than parasites, we hypothesize that the abundance effect is stronger for parasitic than herbivory interactions. To test this hypothesis, we collected 80 quantitative observational networks including 34 herbivorous and 46 parasitic networks from the published literature, and derived preference networks by removing the effects of species abundance. We then determined the network nestedness using both weighted NODF and spectral radius. We also determined species degree distribution, interaction evenness, weighted connectance and robustness for both observational and preference networks. The observational networks (including both herbivory and parasitic networks) were more nested judged by weighted NODF than spectral radius. Preference networks were less nested for parasitic than herbivory networks in terms of both weighted NODF and spectral radius, possibly because removing the abundance effect increased interaction evenness. These trends indicate that the abundance effect on network nestedness is stronger for parasitic than herbivory networks. Weighted connectance and robustness were greater in most preference networks than observational networks, indicating that preference networks may have high network stability and community persistence compared with observational ones. The data indicate that future network analyses should not only address the structural difference between mutualistic and antagonistic interactions, but also between herbivory and parasitic interactions.
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Diverse plant mixtures sustain a greater arbuscular mycorrhizal fungi spore viability than monocultures after 12 years
Peter Dietrich, Christiane Roscher, Adam Thomas Clark, Nico Eisenhauer, Bernhard Schmid and Cameron Wagg
J Plant Ecol    2020, 13 (4): 478-488.   DOI: 10.1093/jpe/rtaa037
Abstract169)      PDF       Save
Aims

Intensive land management practices can compromise soil biodiversity, thus jeopardizing long-term soil productivity. Arbuscular mycorrhizal fungi (AMF) play a pivotal role in promoting soil productivity through obligate symbiotic associations with plants. However, it is not clear how properties of plant communities, especially species richness and composition influence the viability of AMF populations in soils.

Methods

Here we test whether monocultures of eight plant species from different plant functional groups, or a diverse mixture of plant species, maintain more viable AMF propagules. To address this question, we extracted AMF spores from 12-year old plant monocultures and mixtures and paired single AMF spores with single plants in a factorial design crossing AMF spore origin with plant species identity.

Important Findings

AMF spores from diverse plant mixtures were more successful at colonizing multiple plant species and plant individuals than AMF spores from plant monocultures. Furthermore, we found evidence that AMF spores originating from diverse mixtures more strongly increased biomass than AMF from monocultures in the legume Trifolium repens L. AMF viability and ability to interact with many plant species were greater when AMF spores originated from 12-year old mixtures than monocultures. Our results show for the first time that diverse plant communities can sustain AMF viability in soils and demonstrate the potential of diverse plant communities to maintain viable AMF propagules that are a key component to soil health and productivity.

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Frequency-dependent seedling predation by rodents: growth and survival of Quercus wutaishanica in two habitats
Jinfeng Zhang, Jingru Ge, Xingfu Yan, Buddhi Dayananda, Yonghong Luo, Junqing Li
J Plant Ecol    2023, 16 (3): 0-rtac086.   DOI: 10.1093/jpe/rtac086
Abstract79)      PDF (837KB)(79)       Save
Rodents attack oak (Quercus wutaishanica) seeds based on their sizes and frequencies before germination. However, the predation of oak seeds post-germination (seedling cotyledons) is not well studied. Here, we not only tested the preference of rodents for Q. wutaishanica seedling cotyledons based on the frequency of large- versus small-seeded (FLS), but also evaluated the effects of predation on seedlings growth and survival in different habitats. We transplanted seedlings with the FLS set as 9:1, 7:3, 5:5, 3:7 and 1:9, respectively, in the forest gap and under the canopy in the Liupan Mountains National Nature Reserve in Ningxia Hui Autonomous Region, Northwest China. The results showed that: (i) in 1-7 days after transplanting seedlings, rodents prefer the cotyledon of large-seeded seedings while small-seeded seedlings were preferred in 8-60 days, and the positive frequency-dependent predation was observed. (ii) The cotyledons were preyed on, the apical buds were bitted off, and the whole seedlings were uprooted, which mostly occurred under the forest canopy. At the end of a growing season, the survival rate of seedlings in the forest gaps was more than twice that under forest canopies. (iii) If cotyledons were preyed on, the growth of Q. wutaishanica seedlings would not be affected, but the seedlings growth was severely inhibited when the apical bud was bitten off. These results not only provide new insights into the coexistence between rodents and seedlings of different phenotypes, but also reveal the ecological characteristics of deciduous Quercus regeneration.
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Aboveground carbon sequestration rate in alpine forests on the eastern Tibetan Plateau: impacts of future forest management options
Yang Lin, Jiang-Tao Xiao, Yong-Ping Kou, Jia-Xing Zu, Xin-Ran Yu, Yuan-Yuan Li
J Plant Ecol    2023, 16 (3): 0-rtad001.   DOI: 10.1093/jpe/rtad001
Abstract66)      PDF (1756KB)(79)       Save
Alpine forests in the eastern Tibetan Plateau are important ecological barriers in the upper reaches of the Yangtze River. However, due to continuous high-intensity harvesting, a large number of plantings, and the complete harvesting ban measures in recent decades, the forest tree species and age cohorts have become relatively homogenous, and the biodiversity and ecological functions have been reduced. To design effective forest management options to optimize forest structure and increase carbon sequestration capacity, Mao County in Sichuan Province was selected as the study site and six forest management options (harvesting, planting) of different intensities were tested using the LANDIS-II model to simulate and compare the differences in forest aboveground carbon sequestration rate (ACSR) between these options and the current management option over the next 100 years. Our results showed that (i) the different harvesting and planting intensities significantly changed the ACSR compared with the current management options; (ii) different communities responded differently to the management options, with the ACSR differing significantly in cold temperate conifers and temperate conifers but not in broad-leaved trees (P < 0.05); and (iii) a comprehensive consideration of forest management options at the species, community and landscape levels was necessary. Our results suggest that implementing a longer harvesting and planting interval (20 years) at the study site can maximize forest ACSR. This study provides an important reference for evaluating the ability of forest management options to restore forest ecological functions and increase carbon sequestration capacity and for selecting effective forest management programs in the eastern Tibetan Plateau.
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Ecological role of physical dormancy in seeds of Oxytropis racemosa in a semiarid sandland with unpredictable rainfall
Dandan Hu, Jerry M. Baskin, Carol C. Baskin, Xuejun Yang, Zhenying Huang
J Plant Ecol    2018, 11 (4): 542-552.   DOI: 10.1093/jpe/rtx063
Abstract345)      PDF       Save
Aims Seed dormancy and the soil seed bank are crucial to plant regeneration strategy, especially in semiarid ecosystems with unpredictable precipitation. The aim of this study was to investigate how seed dormancy is controlled by environmental factors and how it is correlated with the soil seed bank and regeneration of the perennial legume Oxytropis racemosa, a dominant perennial herb in Mu Us Sandland of semiarid China.
Methods Germination and imbibition experiments on fresh intact and scarified seeds of O. racemosa were used to identify physical dormancy (PY) in seeds of this species. Soil seed bank dynamics, timing of seedling emergence and the fate of buried seeds in the natural habitat were investigated.
Important findings PY was broken by mechanical scarification or wet heat/ice water cycles but not solely by dry heat or wet heat treatment. The soil seed bank exhibited seasonal changes in the number of seeds, which was highest in September and lowest in July. Seeds buried at different sand depths gradually lost dormancy; 20–42% of the seeds remained dormant after 20 months of burial. Dormancy break occurs gradually throughout the year. Our results indicate that O. racemosa exhibits hardcoatedness heterogeneity that spreads germination of a seed cohort between seasons and years in the semiarid environment, where the amount of precipitation during the growing season is highly variable.
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Shade and microbes enhance drought stress tolerance in plants by inducing phytohormones at molecular levels: a review
Muhammad Ahsan Asghar, Bushra Ahmad, Ali Raza, Bilal Adil, Hafz Hassan Javed, Muhammad Umer Farooq, Abuzar Ghafoor, Muhammad Iftikhar Hussain, Iram Shafq, Hassan Karim, Xin Sun, Wenyu Yang, Gábor Kocsy and Junbo Du
J Plant Ecol    2022, 15 (6): 1107-1117.   DOI: 10.1093/jpe/rtac038
Abstract109)      PDF (1599KB)(77)       Save

Plants are frequently exposed to adverse environments during their life span. Among them drought stress is one of the major threats to agricultural productivity. In order to survive in such unstable environment, plants have developed mechanisms through which they recognize the severity of the stress based on the incoming environmental stimuli. To combat the detrimental effects of drought, the plants have evolved various strategies to modulate their physio-hormonal attributes. These strategies that can be modulated by shade and microbes contribute to enhancing tolerance to drought and reducing yield loss. Plant hormones, such as abscisic acid, auxin and ethylene have a major role in the shade- and microbe-associated improvement of drought tolerance through their effects on various metabolic pathways. In this process, the CLAVATA3/EMBRYOSURROUNDING REGION-RELATED 25 peptide has a major role due to its effect on ABA synthesis as shown in our regulatory model.

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Effects of long-term phosphorus addition on soil ratios of phosphomonoesterase to phosphodiesterase in three tropical forests
Taiki Mori, Senhao Wang, Cong Wang, Ji Chen, Cheng Peng, Mianhai Zheng, Juan Huang, Faming Wang, Zhanfeng Liu, Jiangming Mo, Wei Zhang
J Plant Ecol    2023, 16 (3): 0-rtac091.   DOI: 10.1093/jpe/rtac091
Abstract49)      PDF (390KB)(77)       Save
Soil microorganisms in tropical forests can adapt to phosphorus (P)-poor conditions by changing the activity ratios of different types of phosphatases. We tested whether microorganisms in P-poor tropical forest soils increased the phosphomonoesterase (PME) to phosphodiesterase (PDE) activity ratio, because a one-step enzymatic reaction of monoester P degradation might be more adaptive for microbial P acquisition than a two-step reaction of diester P degradation. A continuous 10-year P addition experiment was performed in three tropical forests. The activities of PME and PDE, and their ratio in soil, were determined under the hypothesis that the P-fertilized plots where P shortage is relieved would have lower PME:PDE ratios than the unfertilized controls. We demonstrated that long-term P addition in tropical forest soil did not alter the PME:PDE ratio in primary and secondary forests, whereas P fertilization elevated the PME:PDE ratio in planted forest. These results were in contrast to previous results. The long-term, large-scale P fertilization in our study may have reduced litter- and/or throughfall-derived PDE, which negated the lowered PME:PDE ratio via exogenous P inputs.
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Composition, distribution and environmental drivers of Mongolian rangeland plant communities
Kohei Suzuki, Radnaakhand Tungalag, Amartuvshin Narantsetseg, Tsagaanbandi Tsendeekhuu, Masato Shinoda, Norikazu Yamanaka, Takashi Kamijo
J Plant Ecol    2023, 16 (3): 0-rtac100.   DOI: 10.1093/jpe/rtac100
Abstract54)      PDF (973KB)(77)       Save
In Mongolia, overgrazing and the resulting degradation of rangelands are recognized as serious issues. To address rangeland degradation, we sought to develop a broad-scale vegetation classification of Mongolian rangeland communities focusing on regional characteristics. Moreover, we sought to clarify the spatial distributions of communities and the environmental drivers of the distributions. Between 2012 and 2016, we surveyed vegetation in 278 plots (each 10 m × 10 m) in different regions of Mongolia (43-50° N, 87-119° E) in plots where grazing pressure is low relative to adjacent areas. The data were grouped into vegetation units using a modified two-way indicator species analysis (TWINSPAN). We then explored the regional characteristics of species compositions and community distributions, as well as relationships between distributions and climatic variables. The modified TWINSPAN classified the vegetation data into three cluster groups, each of which corresponds to a particular type of zonal vegetation (i.e. forest steppe, steppe and desert steppe). The aridity index was identified as an important driver of the distributions of all cluster groups, whereas longitude and elevation were important determinants of the distribution of clusters within cluster groups. Western regions, which are characterized by higher elevation and continentality compared with eastern regions, have lower mean temperature and precipitation during the wettest quarter, leading to differences in species composition within cluster groups. Regional differences in species composition reflect differences in phytogeographic origin. Thus, the framework of species composition and distributional patterns in Mongolian rangeland communities was demonstrated in relation to climatic and geographical factors.
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Seasonal and diurnal variation in ecosystem respiration and environmental controls from an alpine wetland in arid northwest China
Hu Yao, Haijun Peng, Bing Hong, Hanwei Ding, Yetang Hong, Yongxuan Zhu, Jie Wang and Cheng Cai
J Plant Ecol    2022, 15 (5): 933-946.   DOI: 10.1093/jpe/rtac050
Abstract84)      PDF (3180KB)(73)       Save

Wetlands store large amounts of carbon stocks and are essential in both global carbon cycling and regional ecosystem services. Understanding the dynamics of wetland carbon exchange is crucial for assessing carbon budgets and predicting their future evolution. Although many studies have been conducted on the effects of climate change on the ecosystem carbon cycle, little is known regarding carbon emissions from the alpine wetlands in arid northwest China. In this study, we used an automatic chamber system (LI-8100A) to measure ecosystem respiration (ER) in the Bayinbuluk alpine wetland in northwest China. The ER showed a significant bimodal diurnal variation, with peak values appearing at 16:30 and 23:30 (Beijing time, UTC + 8). A clear seasonal pattern in ER was observed, with the highest value (19.38 µmol m−2 s−1) occurring in August and the lowest value (0.11 µmol m−2 s−1) occurring in late December. The annual ER in 2018 was 678 g C m−2 and respiration during the non-growing season accounted for 13% of the annual sum. Nonlinear regression revealed that soil temperature at 5 cm depth and soil water content (SWC) were the main factors controlling the seasonal variation in ER. The diurnal variation in ER was mainly controlled by air temperature and solar radiation. Higher temperature sensitivity (Q10) occurred under conditions of lower soil temperatures and medium SWC (25% ≤ SWC ≤ 40%). The present study deepens our understanding of CO2 emissions in alpine wetland ecosystems and helps evaluate the carbon budget in alpine wetlands in arid regions.

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Temporal change in community temporal stability in response to mowing and nutrient enrichment: evidence from a 15-year grassland experiment
Heng Li, Jiajia Zhang, Jingyi Ru, Jian Song, Zhensheng Chi, Yujin Zheng, Lin Jiang, Shiqiang Wan
J Plant Ecol    2023, 16 (4): 0-rtac098.   DOI: 10.1093/jpe/rtac098
Abstract67)      PDF (1165KB)(73)       Save
Land use and nutrient enrichment can substantially affect biodiversity and ecosystem functioning. However, whether and how the responses of community temporal stability to land use and nutrient enrichment change with time remain poorly understood. As part of a 15-year (2005-2019) field experiment, this study was conducted to explore the effects of mowing, nitrogen (N) and phosphorus (P) additions on community temporal stability in a temperate steppe on the Mongolian Plateau. Over the 15 years, N and P additions decreased community temporal stability by reducing the population stability, especially the shrub and semi-shrub stability. However, mowing increased community temporal stability in the early stage (2005-2009) only. Nitrogen addition suppressed community temporal stability in the early and late (2015-2019) stages, whereas enhanced it in the intermediate stage (2010-2014). Phosphorus addition decreased community temporal stability marginally in the early stage and significantly in the late stage. The fluctuations of N-induced changes in community temporal stability are mainly explained by its diverse effects on species asynchrony and population stability over time. Our findings highlight the important role of plant functional groups and species asynchrony in regulating community temporal stability, suggesting that more long-term studies are needed to accurately forecast ecosystem response patterns in the context of global change.
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Germination strategies under climate change scenarios along an aridity gradient
Alexander Zogas, Evsey Kosman and Marcelo Sternberg
J Plant Ecol    2020, 13 (4): 470-477.   DOI: 10.1093/jpe/rtaa035
Abstract184)      PDF       Save
Aims

Climate change in the eastern Mediterranean region will have a strong impact on ecosystem functioning and plant community dynamics due to a reduction in annual rainfall and increased variability. We aim to understand the role of seed banks as potential buffers against climatic uncertainty determined by climate change.

Methods

We examined germination strategies of 18 common species present along an aridity gradient. Data were obtained from soil seed banks germinated during nine consecutive years from arid, semi-arid, Mediterranean and mesic Mediterranean ecosystems. At the semi-arid and Mediterranean sites, rainfall manipulations simulating 30% drought and 30% rainfall increase were applied. Germination strategies were tested under optimal irrigation conditions during three consecutive germination seasons to determine overall seed germinability in each soil sample. Changes in germination strategy were examined using a novel statistical approach that considers the climatic and biotic factors that may affect seed germinability.

Important Findings

The results showed that dominant species controlled their germination fractions by producing seeds with a different yearly germination fraction probability. The amount of rainfall under which the seeds were produced led to two major seed types with respect to germinability: high germinability, seeds leading to transient seed banks, and low germinability, seeds leading to persistent seed banks. We conclude that differential seed production among wet and dry years of both seed types creates a stable balance along the aridity gradient, enabling the soil seed bank to serve as a stabilizing mechanism buffering against rainfall unpredictability. Additionally, we present a general model of germination strategies of dominant annual species in Mediterranean and arid ecosystems that strengthens the notion of soil seed banks as buffers against climatic uncertainty induced by climate change in the region.

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Relative stable interannual variation in plant-plant pollen transfer rather than the plant-pollinator network of a subalpine meadow
Qiang Fang, Shiyun Guo, Tao Zhang, Xiaoxin Tang
J Plant Ecol    2023, 16 (3): 0-rtac094.   DOI: 10.1093/jpe/rtac094
Abstract76)      PDF (1683KB)(72)       Save
Previous studies have shown that plant-pollinator mutualistic interactions experience highly interannual variation. Given that pollinators often move across multiple plant species, the plant-plant interactions that take place via heterospecific pollen (HP) transfer may also vary temporally, which could have important implications for floral evolution and community assembly. Here, we evaluated the interannual variation in plant-pollinator networks and plant-plant heterospecific pollen transfer (HPT) networks of a subalpine meadow community in Southwest China for three consecutive years. The interactions largely varied among years for both network types. The composition of donor-species HP deposited on the plants varied less than did the visit composition of the pollinators, suggesting that HP could be transferred from identical donor species to recipient species through different shared pollinators among years. The plant species were at more similar positions in the HPT network than they were in the plant-pollinator network across years. Moreover, the more generalized plant species in the plant-pollinator network tended to export their pollen grains and more strongly influence HPT. We evaluated the relatively stable structure of the HPT network compared with the plant-pollinator network, which represents an important step in the integration of plant-pollinator and plant-plant interactions.
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Retraction: Species-abundance distributions of tree species varies along climatic gradients in Chinas forests
Jiaxin Zhang, Xiujuan Qiao, Yining Liu, Junmeng Lu, Mingxi Jiang, Zhiyao Tang, Jingyun Fang
J Plant Ecol    2016, 9 (2): 240-240.   DOI: 10.1093/jpe/rtw018
Abstract199)      PDF       Save
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Satellite remote sensing of grasslands: from observation to management
Iftikhar Ali, Fiona Cawkwell, Edward Dwyer, Brian Barrett, Stuart Green
J Plant Ecol    2016, 9 (6): 649-671.   DOI: 10.1093/jpe/rtw005
Abstract272)      PDF       Save
Aims Grasslands are the world's most extensive terrestrial ecosystem, and are a major feed source for livestock. Meeting increasing demand for meat and other dairy products in a sustainable manner is a big challenge. At a field scale, Global Positioning System and ground-based sensor technologies provide promising tools for grassland and herd management with high precision. With the growth in availability of spaceborne remote sensing data, it is therefore important to revisit the relevant methods and applications that can exploit this imagery. In this article, we have reviewed the (i) current status of grassland monitoring/observation methods and applications based on satellite remote sensing data, (ii) the technological and methodological developments to retrieve different grassland biophysical parameters and management characteristics (i.e. degradation, grazing intensity) and (iii) identified the key remaining challenges and some new upcoming trends for future development.
Important findings The retrieval of grassland biophysical parameters have evolved in recent years from classical regression analysis to more complex, efficient and robust modeling approaches, driven by satellite data, and are likely to continue to be the most robust method for deriving grassland information, however these require more high quality calibration and validation data. We found that the hypertemporal satellite data are widely used for time series generation, and particularly to overcome cloud contamination issues, but the current low spatial resolution of these instruments precludes their use for field-scale application in many countries. This trend may change with the current rise in launch of satellite constellations, such as RapidEye, Sentinel-2 and even the microsatellites such as those operated by Skybox Imaging. Microwave imagery has not been widely used for grassland applications, and a better understanding of the backscatter behaviour from different phenological stages is needed for more reliable products in cloudy regions. The development of hyperspectral satellite instrumentation and analytical methods will help for more detailed discrimination of habitat types, and the development of tools for greater end-user operation.
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Differential responses of three coastal grassland species to seawater flooding
Mick E. Hanley, Tom L. Gove, Gregory R. Cawthray, Timothy D. Colmer
J Plant Ecol    2017, 10 (2): 322-330.   DOI: 10.1093/jpe/rtw037
Abstract182)      PDF       Save
Aims Supratidal plant communities fulfil a vital role in coastal protection, but despite an increased likelihood of seawater flooding resulting from anthropogenic climate change, we understand little about how tidal inundation affects these habitats or interactions between their component species. Our aim was to determine how three common coastal grassland species responded to simulated seawater flooding and how subsequent changes to their ecophysiology, growth and survival might affect plant–plant interactions in mixed assemblages.
Methods Seeds of three widely distributed European coastal grassland species (Leontodon autumnalis Asteraceae, Plantago lanceolata Plantaginaceae and Trifolium pratense Fabaceae) were collected from a coastal grassland site in South West England. In Experiment 1, we quantified changes in leaf ion (K +, Na +, Cl ?) concentrations as a response to short-duration (0, 2, 8 or 24h) immersion in seawater of the root-zone before monitoring longer-term effects on plant survival and growth. In a second experiment, we examined community-level responses by subjecting mixed assemblages of all three species to seawater immersion for (0, 12, 24 or 96h).
Important findings When grown individually, one species (Trifolium) had markedly reduced survival with increasing soil immersion time, but a consistent decline in plant growth for all species with flooding duration was most likely linked to osmotic and ionic stresses caused by salt ion accumulation. In mixed assemblages, all species suffered increased mortality and reduced growth following seawater flooding, although the relative contribution of one species (Leontodon) to total biomass increased in flooded microcosms. We thus demonstrate a number of species-specific responses to simulated seawater flooding and show that when grown together, interactions between plants are altered as a consequence. We argue that variation in the responses of component plant species will dictate how coastal plant communities respond to, and recover from, expected changes in sea levels and transient floods following storm surge events. Such information is vital in order to predict future impacts of seawater floods on supratidal vegetation.
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Plant invasions
Bruce Osborne, Margherita Gioria
J Plant Ecol    2018, 11 (1): 1-3.   DOI: 10.1093/jpe/rtx070
Abstract206)      PDF       Save
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Nutrient uptake and gas exchange of Great Basin plants provide insight into drought adaptations and coexistence
Ricardo Mata-González, Matthew Hovland, Mohamed A.B. Abdallah, David W. Martin and Jay S. Noller
J Plant Ecol    2021, 14 (5): 854-869.   DOI: 10.1093/jpe/rtab037
Abstract110)      PDF       Save
Aims

Although increases in precipitation variability in arid ecosystems are projected due to climate change, the response of desert shrub communities to precipitation change has not been fully elucidated. Such knowledge is important since drought-adapted plants exhibit varied mechanisms of survival that may contribute to species coexistence.

Methods

We tested the responses of eight drought-adapted plants, a mix of graminoids, shrubs and forbs to three summer precipitation scenarios (1.3, 2.6 and 3.9 cm per month) in a common garden experiment in the Great Basin (Owens Valley, California). Changes in mineral nutrient uptake (carbon, nitrogen, phosphorus, potassium, calcium, magnesium, manganese, copper, boron, zinc, iron and sodium) and gas exchange parameters (photosynthetic rate and stomatal conductance) were investigated in the studied species.

Important Findings

Two graminoids (Sporobolus airoides and Leymus triticoides) and one salt tolerant shrub species (Atriplex confertifolia) responded to increased water availability with increases in photosynthetic rate and/or stomatal conductance. There was a significant correlation between water availability and uptake of nutrients for five out of eight species. Artemisia tridentata, with higher rates of photosynthesis, contained greater amounts of potassium, copper and boron, while Juncus arcticus, with higher rates of photosynthesis, contained greater amounts of magnesium and iron, and less sodium. Juncus arcticus and three salt-adapted species (A. confertifoliaDistichlis spicata and S. airoides) exhibited correlations with stomatal conductance and concentrations of nutrients. Results indicate that differential physiological response mechanisms to increased moisture and associated nutrient uptake strategies in drought-adapted species may mediate coexistence under increased summer precipitation.

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Stoichiometric homeostasis in response to variable water and nutrient supply in a Robinia pseudoacacia plant–soil system
Bingqian Su and Zhouping Shangguan
J Plant Ecol    2022, 15 (5): 991-1006.   DOI: 10.1093/jpe/rtac011
Abstract91)      PDF (2229KB)(71)       Save

All organisms need elements in fixed proportions for carrying out normal metabolic processes and how flexible they are depends on how effective they are utilizing these resources from external sources. It is important to understand the interactions among plant, soil and microbial biomass carbon (C), nitrogen (N) and phosphorus (P) stoichiometry under different conditions of resource supply. We conducted a pot experiment on 1-year-old Robinia pseudoacacia seedlings for nearly 5 months under different water, nitrogen and phosphorus supplies, and we determined plant, soil and microbial biomass C, N and P stoichiometry. We found that plant, soil and microbial nutrients and stoichiometry exhibited a certain degree of plasticity in response to the changes in water and nutrient conditions in their environments. Variation partitioning analysis showed that root stoichiometry accounted for a large part of the variance in microbial stoichiometry. Structural equation modeling further revealed that root stoichiometry and leaf stoichiometry were two direct factors affecting microbial biomass C:N and C:P, and that root stoichiometry had the greatest direct effect. In addition, the degree of homeostasis for microbial biomass C and C:P was more sensitive to changes in soil nutrients than changes in other factors, and other elements and elemental ratios displayed strict homeostasis. These results highlight the importance of studying microbial stoichiometry in improving our understanding of nutrient cycling of the plant–soil system under different water and nutrient supply.

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Soil respiration is driven by fine root biomass along a forest chronosequence in subtropical China
Chao Wang, Yinlei Ma, Stefan Trogisch, Yuanyuan Huang, Yan Geng, Michael Scherer-Lorenzen, Jin-Sheng He
J Plant Ecol    2017, 10 (1): 36-46.   DOI: 10.1093/jpe/rtw044
Abstract272)      PDF       Save
Aims Soil respiration (Rs) is a major process controlling soil carbon loss in forest ecosystems. However, the underlying mechanisms leading to variation in Rs along forest successional gradients are not well understood. In this study, we investigated the effects of biotic and abiotic factors on Rs along a forest successional gradient in southeast China.
Methods We selected 16 plots stratified by forest age, ranging from 20 to 120 years. In each plot, six shallow collars and six deep collars were permanently inserted into the soil. Shallow and deep collars were used to measure Rs and heterotrophic respiration (Rh), respectively. Autotrophic soil respiration (Ra) was estimated as the difference between Rs and Rh. Litter layer respiration (R L) was calculated by subtracting soil respiration measured in collars without leaf litter layer (R NL) from Rs. Rs was measured every 2 months, and soil temperature (ST) and soil volumetric water content (SVWC) were recorded every hour for 19 months. We calculated daily Rs using an exponential model dependent on ST. Daily Rs was summed to obtain cumulative annual Rs estimates. Structural equation modelling (SEM) was applied to identify the drivers of Rs during forest succession.
Important findings Rs showed significant differences among three successive stages, and it was the highest in the young stage. Ra was higher in the young stage than in the medium stage. Cumulative annual Rs and Ra peaked in the young and old stages, respectively. Cumulative annual Rh and respiration measured from soil organic matter (R SOM) decreased, whereas R L increased with forest age. The SEM revealed that cumulative annual Rs was influenced by fine root biomass and SVWC. Our results indicated that the dominant force regulating Rs on a seasonal scale is ST; however, on a successional scale, belowground carbon emerges as the dominant influential factor.
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Editors-in-Chief
Yuanhe Yang
Bernhard Schmid
CN 10-1172/Q
ISSN 1752-9921(print)
ISSN 1752-993X(online)