群落时间稳定性对刈割和养分富集的响应随时间的变化

土地利用和养分富集能对生物多样性和生态系统功能产生巨大的影响。然而,群落时间稳定性对土地利用和养分富集的响应是如何随时间变化的尚不清楚。作为历经15年(2005-2019)野外实验的一部分,本研究旨在探索在蒙古高原温带草原上,刈割、氮添加和磷添加对群落时间稳定性的效应。经过15年的实验,氮添加和磷添加均降低了群落时间稳定性,尤其是灌木和半灌木功能群的时间稳定性。刈割仅在实验早期(2005-2009)增加群落时间稳定性。氮添加在实验早期和末期(2015-2019)降低了群落时间稳定性,但在实验中期(2010-2014)反而提高了群落时间稳定性。磷添加在实验早期只轻微降低群落时间稳定性,但在实验末期显著降低群落时间稳定性。氮添加引起的群落时间稳定性变化的波动主要归因于其对物种异步性和种群时间稳定性的不同影响。我们的发现强调了植物功能群和物种异步性在调控群落时间稳定性方面的重要作用,以及仍然需要进行更长期的研究,以准确预测全球变化背景下的生态系统响应模式。

Warming changes plant competitive hierarchy in a temperate steppe in northern China

Aims Quantifying changes in plant growth and interspecific interactions,both of which can alter dominance of plant species,will facilitate explanation and projection of the shifts in species composition and community structure in terrestrial biomes expected under global warming.We used an experimental warming treatment to examine the potential influence of global warming on plant growth and interspecific interactions in a temperate steppe in northern China.Materials and methods Six dominant plant species were grown in monoculture and all 15 two-species mixtures for one growing season under ambient and elevated temperatures in the field.Temperature was manipulated with infrared radiators.Important findings Total biomass of all the six plant species was increased by 34–63%in monocultures and 20–76%in mixtures.The magnitude of the warming effect on biomass was modified by plant interactions.Experimental warming changed the hierarchies of both competitive response and competitive effect.The competitive ability(in terms of response and effect)of one C4 grass(Pennisetum centrasiaticum)was suppressed,while the competitive abilities of one C3 forb(Artemisia capillaris)and one C3 grass(Stipa krylovii)were enhanced by experimental warming.The demonstrated alterations in growth and plant interactions may lead to changes in community structure and biodiversity in the temperate steppe in a warmer world in the future.

Global patterns of the responses of leaf-level photosynthesis and respiration in terrestrial plants to experimental warming

Aims The balance between leaf photosynthesis and respiration of terrestrial plants determines the net carbon(C)gain by vegetation and consequently is important to climate–C cycle feedback.This study is to reveal the global patterns of the responses of leaf-level net photosynthesis and dark respiration to elevated temperature.Methods Data for leaf-level net photosynthesis rate(P_(n))and dark respiration rate(R_(d))in natural terrestrial plant species with standard deviation(or standard error or confidence interval)and sample size were collected from searched literatures on Web of Science.Then a metaanalysis was conducted to estimate the effects of experimental warming on leaf-level P_(n) and R_(d) of terrestrial plants.Important findings Across all the plants included in the analysis,warming enhanced P_(n) and R_(d) significantly by 6.13 and 33.14%,respectively.However,the responses were plant functional type(PFT)specific.Specifically,photosynthesis of C_(4) herbs responded to experimental warming positively but that of C_(3) herbs did not,whereas their respiratory responses were similar,suggesting C_(4) plants would benefit more from warming.The photosynthetic response declined linearly with increasing ambient temperature.The respiratory responses linearly enhanced with the increase in warming magnitude.In addition,a thermal acclimation of R_(d),instead of P_(n),was observed.Although greater proportion of fixed C was consumed(greater R_(d)/P_(n) ratio),warming significantly enhanced the daily net C balance at the leaf level.This provides an important mechanism for the positive responses of plant biomass and net primary productivity to warming.Overall,the findings,including the contrastive responses of different PFTs and the enhancement in daily leaf net C balance,are important for improving model projection of the climate–C cycle feedback.

Precipitation regulates plant gas exchange and its long-term response to climate change in a temperate grassland

Aims Climate change largely impacts ecosystem carbon and water cycles by changing plant gas exchange,which may further cause positive or negative feedback to global climate change.However,long-term global change manipulative experiments are seldom conducted to reveal plant ecophysiological responses to climatic warming and altered precipitation regimes.Methods An 8-year field experiment with both warming and increased precipitation was conducted in a temperate grassland in northern China.We measured leaf gas exchange rates(including plant photosynthesis,transpiration and instantaneous water use efficiency[WUE])of two dominant plant species(Stipa sareptana var.krylovii and Agropyron cristatum)from 2005 to 2012(except 2006 and 2010)and those of other six species from 2011 to 2012.Important Findings Increased precipitation significantly stimulated plant photosynthetic rates(A)by 29.5%and 19.9%and transpiration rates(E)by 42.2%and 51.2%for both dominant species S.sareptana var.krylovii and A.cristatum,respectively,across the 8 years.Similarly,A and E of the six plant functional types were all stimulated by increased precipitation in 2011 and 2012.As the balance of A and E,the instantaneous WUEs of different plant species had species-specific responses to increased precipitation.In contrast,neither warming nor its interaction with increased precipitation significantly affected plant leaf gas exchange rates.Furthermore,A and E of the two dominant species and their response magnitudes to water treatments positively correlated with rainfall amount in July across years.We did not find any significant difference between the short-term versus long-term responses of plant photosynthesis,suggesting the flexibility of leaf gas exchange under climate change.The results suggest that changing precipitation rather than global warming plays a prominent role in determining production of this grassland in the context of climate change.

Different responses of arbuscular mycorrhizal fungal community to day-time and night-time warming in a semiarid steppe

Arbuscular mycorrhizal(AM) fungi form mutualistic symbioses with most plant species and play important roles in ecosystems.Knowledge of the response of AM fungi to temperature change will improve our understanding of the function of AM fungal community under global climate change scenarios in ecosystems.The effects of constant warming on AM fungal communities have been investigated previously,but responses to asymmetrical warming over 24-h periods have never been documented in natural ecosystems.In this study,we examined AM fungal communities in a full factorial design including day-time and night-time warming in a semiarid steppe in northern China.Day-time and 24-h warming,but not night-time warming,significantly increased AM fungal spore density.In contrast,none of the three warming regimes had a significant effect on AM fungal extra radical hyphal density.Atotal of 161 operational taxonomic units(OTUs) of AM fungi were recovered by 454 pyrosequencing of 18 S r DNA.Day-time,night-time,and 24-h warming all significantly increased AM fungal OTU richness.Some AM fungal OTUs showed a significant bias toward day-time,night-time or24-h warming.The AM fungal community composition was significantly affected by night-time warming,but not by day-time and 24-h warming.Our finding highlighted different responses of AM fungal spore density and community composition to asymmetrical warming.This study might improve our understanding of ecosystem functioning of AM fungal community under global climate change scenarios in a semiarid steppe ecosystem.

Foreword to the special issue:looking into the impacts of global warming from the roof of the world

To most people,the Qinghai-Tibetan Plateau is a place full of mystery.It is also mysterious to many ecologists.The vast central Asian plateau lies at an average elevation>4000 m and covers about 370 million km2.Spanning the highest range of elevations of any ecosystem in the world makes the plateau unique even among alpine ecosystems due to the presence of extreme abiotic environments:the lowest atmospheric pressure and thus,the lowest partial pressures of CO_(2) and O_(2),low temperatures and high levels of radiation,including high ultraviolet radiation.

Effects of fire and nitrogen addition on photosynthesis and growth of three dominant understory plant species in a temperate forest

Aims Fire and atmospheric nitrogen(N)deposition have the potential to influence growth and productivity of forest canopy.However,their impacts on photosynthesis and growth traits of understory plants in forests remain largely unexplored.This study was conducted to examine the effects of burning and N addition on foliar N content,net photosynthesis and growth traits of three dominant shrub species(Vitex negundo,Lindera glauca and Symplocos chinensis)in a temperate forest in Central China.Methods The experiment used a pair-nested design,with four treatments(control,burning,N addition and burning plus N addition)and five replicates.Leaf mass area(LMA),area-based concentrations of foliar N and chlorophyll(N_(area) and Chl_(area)),net photosynthesis(A_(n)),stomatal conductance(g_(s)),maximum photosynthetic rate(A_(max))and maximal carboxylation rate(V_(cmax)),basal diameter,height and branch length(BL)of the three species were measured.Important Findings Across the three species,burning stimulated LMA,N_(area),Chl_(area),A_(n),g_(s),A_(max) and V_(cmax),and consequently enhanced basal diam-eter,height and BL.Nitrogen addition increased A_(n) and gs but did not affect LMA,N_(area),Chl_(area),A_(max),V_(cmax),basal diameter,height or BL.However,N addition strengthened the positive effects of burning on g_(s),V_(cmax),A_(n) and BL.The findings indicate the primary role of light resources in determining plant photosynthesis and growth of understory shrub species after fire and highlight that understory plants should be considered in projection of biomass accumulation and productivity of forests under environmental perturbations.

Carbon fluxes and species diversity in grazed and fenced typical steppe grassland of Inner Mongolia, China

Aim Grasslands are dominant vegetation of China,support outstanding biodiversity and sequester bulk amount of atmospheric CO_(2).These grasslands are highly degraded and fragmented due to remarkable anthropogenic and grazing loads.Chinese Government has made great attempt to restore by grazing exclusion.The relations of carbon fluxes with species composition and diversity in the communities sensitive to grazing by large herbivores are needed to be analysed under the global climate change scenario.The objective of present study was to comprehend the effects of grazing and fencing on the ecosystem structure and function of the typical steppe grassland.Methods To meet the objectives,overgrazed and fenced(since year 2001)sys-tems were selected in typical steppe grassland at the Duolun Restoration Ecology Research Station,Inner Mogolia,China.Within each system,three dominant communities with three replicates were selected.In each replicate community,three 1×1 m plots,were randomly located.Each plot was divided into four 50×50 cm quadrats.A total of 216,50×50 cm quadrats were sampled.From each quadrat,number of individuals and above-ground herbaceous biomass for each species,soil respiration(SR),ecosystem respira-tion(ER),net(NEE)as well as gross(GEE)ecosystem CO_(2) exchanges were recorded in June 2015.Data were well analysed using statistical software.Canonical correspondence analysis showed dif-ferential responses of communities to the structure and function of the typical steppe grassland.Important Findings Across the communities,fencing reduced the soil tempera-ture by 12%and at the same time increased the soil moisture by 44.30%,thus,increased the species richness by 28%,evenness by 21%,above-ground biomass by 19%and plant carbon by 20%.Interestingly,fencing increased NEE by 128%,GEE by 77%,SR by 65%and ER by 39%.Under fencing,species composition partially governed the CO_(2) exchange processes.Conclusions Fencing reduces soil temperature and thereby improves species diversity and more efficient CO_(2) sequestration and long-term and in-depth study is desirable for a better understanding of the relation-ship between species diversity and ecosystem carbon uptake.

Seasonal distribution of increased precipitation in maternal environments influences offspring performance of Potentilla tanacetifolia in a temperate steppe ecosystem

Aims Precipitation is predicted to increase in arid and semiarid regions under climate change,with greater changes in intra-and interannual distribution in the future.As a major limiting factor in these regions,changes in precipitation undoubtedly influence plant growth and productivity.However,how the temporal shifts in pre-cipitation will impact plant populations are uncertain.Methods A 3-year field experiment and a greenhouse experiment were conducted in a temperate grassland in northern China to examine the impacts of seasonal(spring and summer)increased precipitation on offspring performance of a common species,Potentilla tanacetifolia.Important Findings Our results showed that the amounts and timing of increased precipitation both played important roles in regulating offspring performance of P.tanacetifolia in the temperate steppe ecosystem.Increased precipitation in spring at maternal stage stimulated seed production,germination percentage and seedling biomass,whereas increased precipitation in summer at maternal stage stimulated seedling biomass.The timing of increased precipitation influenced seed attributes,whereas the amount of increased precipitation influenced offspring seedling biomass.Our results indicate that population development of P.tanacetifolia may be underestimated under future increased precipitation regime,if the transgenerational effect is not taken into account.

The first 10 years of JPE

Ten years ago,the Botanical Society of China together with the Institute of Botany of the Chinese Academy of Sciences decided to launch the new international Journal of Plant Ecology,or in short JPE,to introduce the works of Chinese ecologists to the international community and promote ecological research in China.The new journal,which could be considered as an off-spring of the corresponding Chinese-language journal,offers authors from all over the world,but also specifically from China,a platform to publish peer-reviewed original research and reviews in the broad field of plant ecology.During initial discussions in the editorial board and with Oxford University Press,we decided that it would be best if the authors with their submissions are allowed to define the scope of the journal,because in this way we could gain a unique profile with least overlap with other international journals.The prime goal was to publish good and relevant science,which would produce long-term impact as a secondary result.

Plant carbon substrate supply regulated soil nitrogen dynamics in a tallgrass prairie in the Great Plains, USA: results of a clipping and shading experiment

Land use management affects plant carbon(C)supply and soil environments and hence alters soil nitrogen(N)dynamics,with consequent feedbacks to terrestrial ecosystem productivity.The objective of this study was to better identify mechanisms by which land-use management(clipping and shading)regulates soil N in a tallgrass prairie,OK,USA.Methods We conducted 1-year clipping and shading experiment to investigate the effects of changes in land-use management(soil microclimates,plant C substrate supply and microbial activity)on soil inorganic N(NH_(4)^(+)-N and NO_(3)^(-)-N),net N mineralization and nitrification in a tallgrass prairie.Important Findings Land-use management through clipping and/or shading significantly increased annual mean inorganic N,possibly due to lowered plant N uptake and decreased microbial N immobilization into biomass growth.Shading significantly increased annual mean mineralization rates(P<0.05).Clipping slightly decreased annual mean N nitrification rates whereas shading significantly increased annual mean N nitrification rates.Soil microclimate significantly explained 36%of the variation in NO_(3)^(-)-N concentrations(P=0.004).However,soil respiration,a predictor of plant C substrate supply and microbial activity,was negatively correlated with NH_(4)^(+)-N concentrations(P=0.0009),net N mineralization(P=0.0037)and nitrification rates(P=0.0028)across treatments.Our results suggest that change in C substrate supply andmicrobial activity under clipping and/or shading is a critical control on NH_(4)^(+)-N,net N mineralization and nitrification rates,whereas clipping and shading-induced soil microclimate change can be important for NO_(3)^(-)-N variation in the tallgrass prairie.

Response to Smith’s comment

A commentary on our recent article on Journal of Plant Ecology(Liang et al.2013)by Smith(2014)argues that it is not appro-priate to lump data from different experiments together to demonstrate the thermal acclimation of leaf dark respiration.We agree that many factors,as listed by Smith(2014),would impact the responses of leaf carbon exchanges to warming and the consequent thermal acclimation.Although not all factors were included,we discussed in the article that light and vapor pressure deficit(VPD)could have affected our conclusions(Liang et al.2013).The“acclimation”in our paper did not exactly accord with the physiological definition(Atkin and Tjoelker 2003;Smith and Dukes 2013).It is hard to make the environ-mental factors as well as warming magnitude coherent in a syn-thesis study because the data were from different experiments.Therefore,the“acclimation”in our meta-analysis was more like an apparent one rather than the physiologically intrinsic one as defined by Atkin et al.

Editorial

Launched by the Oxford University Press on behalf of the Botanical Society of China and the Institute of Botany of Chinese Academy of Sciences,the new Journal of Plant Ecology(JPE)publishes original research articles,reviews and forum pieces covering the entire field of plant ecology.We feel there is a great need for this journal in a time when many other journals are only able to publish a small amount of suitable manuscripts,often those for which they expect the highest impact in terms of citations.To achieve this,these journals focus on concepts and novelty.However,science,in particular the science of ecology,does not simply advance by accumulating concepts and novelty.In the long run,it is the sound results obtained in well-designed studies with sufficient replication and careful measurement and analysis which increase the base of knowledge on which interpretation,understanding and eventually the advancement of science depend.A key criterion by which sound scientific results can be judged is repeatability(a contrast to novelty!).One of the greatest threats to scientific advancement is nonpublication and exclusion of results from subsequent synthesis.By publishing sound scientific results,JPE aims to contribute to the advancement of plant ecology beyond concepts and novelty.