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 ...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.展开更多
Aim European and North american studies have suggested that nitrogen(N)depositions reduce plant diversity and increase primary pro-ductivity due to changes in plant traits.To predict the vegetation response to future ...Aim European and North american studies have suggested that nitrogen(N)depositions reduce plant diversity and increase primary pro-ductivity due to changes in plant traits.To predict the vegetation response to future global change,experimental validations from other regions are widely needed.We assessed the effects of N treat-ment by urea fertilization on the diversity and biomass of the her-baceous plant traits(HPTs)in a dry tropical environment of India.Methods Diversity and biomass of different HPTs were determined on the basis of data collected in year 2010,from 135,1 m×1 m plots dis-tributed over 15 locations.The plots were treated with urea fertilizer in different doses(Control,60 kgNha−1 yr−1 and 120 kg N ha−1yr−1)since 1st January 2007.The plots were ordinated and data were subjected to appropriate statistical analyses.Important Findings Correspondence analysis(Ca)suggested uniqueness of species composition due to N amendment.species number and biomass of the trait categories varied due to N fertilization and traits.all studied trait categories(except N-fixers)yielded maximum mean species number at moderate level of N fertilization.Different levels of N fer-tilization exhibited different species diversity-primary productivity(D-P)relationships.Further,study showed reduction in plant diver-sity due to increase in biomass at high rates of N addition.Conclusions Tall,erect,non N-fixers,annuals,grasses HPTs were favoured by N enrichment.N dose above 60 kg enhanced the biomass of fast grow-ing,erect,annuals,non N-fixers,nitrophilic HPTs.The changes in traits with N addition,especially the increase in annuals and grasses and decrease in typically N-rich N-fixers,have implications for sus-tainable cattle production.展开更多
Background Hyptis suaveolens(L.)Poit.,native to the American tropics,is a pantropical annual plant and a major invasive species throughout India.It was anticipated that the availability of sunlight,coupled with its su...Background Hyptis suaveolens(L.)Poit.,native to the American tropics,is a pantropical annual plant and a major invasive species throughout India.It was anticipated that the availability of sunlight,coupled with its superior reproductive potential,persistent propagule bank,and dispersal ability,could lead to an increase in the growth and spread of this invader,thus potentially impeding herbaceous growth and diversity in non-native areas.Clarifying its ecological fitness and competitive performance will be useful to manage the spread of H.suaveolens in natural ecosystems that are facing a wide range of anthropogenic pressures.Methods The present study is a three-tier experiment.In the first tier,a field study was conducted to assess the patterns of H.suaveolens abundance and herbaceous species diversity in response to light availability(sun,842-1072μmol m^(-2)s^(-1)and shade 253-341μmol m^(-2)s^(-1))in the tropical dry deciduous ecosystems in the Vindhyan highlands,India.Furthermore,the impact of H.suaveolens abundance on the resident native and non-native species abundance and diversity was also studied.In the second tier,a randomized common garden experiment was conducted to understand the trait fitness of H.suaveolens in sun(940μmol m^(-2)s^(-1))and shade(300μmol m^(-2)s^(-1))conditions.In the third tier,a plant growth chamber experiment with high-light(940μmol m^(-2)s^(-1))and low-light(300μmol m^(-2)s^(-1))treatments was done to learn how H.suaveolens partitions its biomass between aboveground and belowground plant parts.Results The field study indicated that the sunlit areas had a higher abundance of H.suaveolens and a lower diversity of resident herbaceous species than the shaded areas.The common garden experiment showed that sun-dwelling H.suaveolens individuals performed better in germinative,vegetative,eco-physiological,and reproductive traits than the shade-dwelling individuals.The growth chamber experiment exhibited that plants grown in high-light environment had greater seed germination,seedling recruitment,and aboveground biomass than those grown in low-light environment,whereas plants grown in low-light environment exhibited a higher root mass ratio than the high-light individuals.These results suggest that H.suaveolens individuals mask the understory vegetation owing to higher seedling recruitment,relative growth rate,photosynthetic performance,resource acquisition-allocation,and reproductive output in response to high-light conditions.Conclusions The study concludes that light significantly controls the invasive population dynamics of H.suaveolens in dry deciduous forests.In high-light areas,H.suaveolens populations dominate the forest understory with suboptimal shade tolerance.In shade environment,H.suaveolens maintains a persistent soil seed bank along with‘Oskarindividuals'that become active in response to high-light availability.The modus operandi is a'sit and wait'strategy.The current study provides insights on prioritizing areas for H.suaveolens management that will potentially reduce the risk of biological invasions on the native species diversity of tropical regions.展开更多
基金This study was supported by TWAS Fellowships for Research and Advanced Training,Italy to R.S.(FR number 3240281997)the National Natural Science Foundation of China(31430015,31270564).
文摘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.
文摘Aim European and North american studies have suggested that nitrogen(N)depositions reduce plant diversity and increase primary pro-ductivity due to changes in plant traits.To predict the vegetation response to future global change,experimental validations from other regions are widely needed.We assessed the effects of N treat-ment by urea fertilization on the diversity and biomass of the her-baceous plant traits(HPTs)in a dry tropical environment of India.Methods Diversity and biomass of different HPTs were determined on the basis of data collected in year 2010,from 135,1 m×1 m plots dis-tributed over 15 locations.The plots were treated with urea fertilizer in different doses(Control,60 kgNha−1 yr−1 and 120 kg N ha−1yr−1)since 1st January 2007.The plots were ordinated and data were subjected to appropriate statistical analyses.Important Findings Correspondence analysis(Ca)suggested uniqueness of species composition due to N amendment.species number and biomass of the trait categories varied due to N fertilization and traits.all studied trait categories(except N-fixers)yielded maximum mean species number at moderate level of N fertilization.Different levels of N fer-tilization exhibited different species diversity-primary productivity(D-P)relationships.Further,study showed reduction in plant diver-sity due to increase in biomass at high rates of N addition.Conclusions Tall,erect,non N-fixers,annuals,grasses HPTs were favoured by N enrichment.N dose above 60 kg enhanced the biomass of fast grow-ing,erect,annuals,non N-fixers,nitrophilic HPTs.The changes in traits with N addition,especially the increase in annuals and grasses and decrease in typically N-rich N-fixers,have implications for sus-tainable cattle production.
基金the Science and Engineering Research Board,Department of Science and Technology,India(File No.SERB-EEQ/2021/000356)IOE,Institute of Science,Banaras Hindu University
文摘Background Hyptis suaveolens(L.)Poit.,native to the American tropics,is a pantropical annual plant and a major invasive species throughout India.It was anticipated that the availability of sunlight,coupled with its superior reproductive potential,persistent propagule bank,and dispersal ability,could lead to an increase in the growth and spread of this invader,thus potentially impeding herbaceous growth and diversity in non-native areas.Clarifying its ecological fitness and competitive performance will be useful to manage the spread of H.suaveolens in natural ecosystems that are facing a wide range of anthropogenic pressures.Methods The present study is a three-tier experiment.In the first tier,a field study was conducted to assess the patterns of H.suaveolens abundance and herbaceous species diversity in response to light availability(sun,842-1072μmol m^(-2)s^(-1)and shade 253-341μmol m^(-2)s^(-1))in the tropical dry deciduous ecosystems in the Vindhyan highlands,India.Furthermore,the impact of H.suaveolens abundance on the resident native and non-native species abundance and diversity was also studied.In the second tier,a randomized common garden experiment was conducted to understand the trait fitness of H.suaveolens in sun(940μmol m^(-2)s^(-1))and shade(300μmol m^(-2)s^(-1))conditions.In the third tier,a plant growth chamber experiment with high-light(940μmol m^(-2)s^(-1))and low-light(300μmol m^(-2)s^(-1))treatments was done to learn how H.suaveolens partitions its biomass between aboveground and belowground plant parts.Results The field study indicated that the sunlit areas had a higher abundance of H.suaveolens and a lower diversity of resident herbaceous species than the shaded areas.The common garden experiment showed that sun-dwelling H.suaveolens individuals performed better in germinative,vegetative,eco-physiological,and reproductive traits than the shade-dwelling individuals.The growth chamber experiment exhibited that plants grown in high-light environment had greater seed germination,seedling recruitment,and aboveground biomass than those grown in low-light environment,whereas plants grown in low-light environment exhibited a higher root mass ratio than the high-light individuals.These results suggest that H.suaveolens individuals mask the understory vegetation owing to higher seedling recruitment,relative growth rate,photosynthetic performance,resource acquisition-allocation,and reproductive output in response to high-light conditions.Conclusions The study concludes that light significantly controls the invasive population dynamics of H.suaveolens in dry deciduous forests.In high-light areas,H.suaveolens populations dominate the forest understory with suboptimal shade tolerance.In shade environment,H.suaveolens maintains a persistent soil seed bank along with‘Oskarindividuals'that become active in response to high-light availability.The modus operandi is a'sit and wait'strategy.The current study provides insights on prioritizing areas for H.suaveolens management that will potentially reduce the risk of biological invasions on the native species diversity of tropical regions.
