This study aims to verify the concept of niches at multiple spatial scales in plant communities.To this end,we analyzed the niche characteristic of Rhododendron dauricum plant communities in Northeast China at three s...This study aims to verify the concept of niches at multiple spatial scales in plant communities.To this end,we analyzed the niche characteristic of Rhododendron dauricum plant communities in Northeast China at three spatial scales.At the local scale,we calculated the Importance Value(IV)of species in five communities in the north of the Da Hinggan Mountains.At the intermediate scale,we examined five communities in their entirety,calculated the niche breadth of the species,and integrated niche overlap and interspecific association to analyze interspecific relationships.Further,the generalized additive model(GAM)was used to analyze the impact of topography and soil factors on niche characteristics.At the regional scale,we analyzed the geographical distribution of dominant species of R.dauricum plant communities in Northeast China and used principal component analysis(PCA)to analyze the impact of geographical and climate factors on species distribution.The results show that at the local scale,the IV of the species in each community varies widely.At the intermediate scale,species with a wide niche breadth tend to have a high value for IV.Larix gmelinii,Betula platyphylla,R.dauricum,Ledum palustre,and Vaccinium vitis-idaea had a relatively wide niche breadth and a high niche overlap,and the interspecific associations were almost all positive.Elevation and soil nutrients were the most dominant environmental factors.At the regional scale,species with a wide niche breadth tend to have a wide range of distribution,and temperature and precipitation were the most dominant environmental factors.This study suggests that the niche characteristics at three scales are both related and different.Niche characteristics at the local scale were various and labile,and niche characteristics at the intermediate and regional scales were relatively regular.These results show some degree of consistency with previous studies from an evolutionary perspective.The action mechanisms of these communities are related to differences in the dominant environmental factors.In addition,the integration of niche overlap and interspecific association determine interspecific relationships more accurately.展开更多
The influences of trait diversity(i.e.,the niche complementarity effect)and functional composition(i.e.,the mass ratio effect)on aboveground biomass(AGB)is a highly debated topic in forest ecology.Therefore,further st...The influences of trait diversity(i.e.,the niche complementarity effect)and functional composition(i.e.,the mass ratio effect)on aboveground biomass(AGB)is a highly debated topic in forest ecology.Therefore,further studies are needed to explore these mechanisms in unstudied forest ecosystems to enhance our understanding,and to provide guidelines for specific forest management.Here,we hypothesized that functional composition would drive AGB better than trait diversity and stem size inequality in the(sub-)tropical forests of Nepal.Using data from 101 forest plots,we tested 25 structural equation models(SEMs)to link elevation,stem DBH inequality,trait diversity(i.e.,trait richness,evenness,dispersion and divergence),functional composition[i.e.,community-weighted of maximum height mean(CWM of Hmax),specific leaf area(CWM of SLA),leaf dry matter content(CWM of LDMC),and wood density(CWM of WD)]and AGB.The best-fitted SEMs indicated that CWM of Hmax promoted AGB while overruling the impacts of trait diversity indices on AGB.However,low trait diversity indices were linked with higher AGB while overruling the effects of CWM of SLA,LDMC and WD on AGB.In addition,AGB decreased with increasing elevation,whereas stem size inequality did not influence AGB.Our results suggest that divergent species’functional strategies could shape AGB along an altitudinal gradient in tropical forests.We argue that forest management practices should include plant functional traits in the management plan for the co-benefits of biodiversity conservation and carbon sequestration that underpins human wellbeing.展开更多
Understanding the influence of environmental covariates on plant distribution is critical,especially for aquatic plant species.Climate change is likely to alter the distribution of aquatic species.However,knowledge of...Understanding the influence of environmental covariates on plant distribution is critical,especially for aquatic plant species.Climate change is likely to alter the distribution of aquatic species.However,knowledge of this change on the burden of aquatic macroorganisms is often fraught with difficulty.Ottelia,a model genus for studying the evolution of the aquatic family Hydrocharitaceae,is mainly distributed in slow-flowing creeks,rivers,or lakes throughout pantropical regions in the world.Due to recent rapid climate changes,natural Ottelia populations have declined significantly.By modeling the effects of climate change on the distribution of Ottelia species and assessing the degree of niche similarity,we sought to identify high suitability regions and help formulate conservation strategies.The models use known background points to determine how environmental covariates vary spatially and produce continental maps of the distribution of the Ottelia species in Africa.Additionally,we estimated the possible influences of the optimistic and extreme pessimistic representative concentration pathways scenarios RCP 4.5 and RCP 8.5 for the 2050s.Our results show that the distinct distribution patterns of studied Ottelia species were influenced by topography(elevation)and climate(e.g.,mean temperature of driest quarter,annual precipitation,and precipitation of the driest month).While there is a lack of accord in defining the limiting factors for the distribution of Ottelia species,it is clear that water-temperature conditions have promising effects when kept within optimal ranges.We also note that climate change will impact Ottelia by accelerating fragmentation and habitat loss.The assessment of niche overlap revealed that Ottelia cylindrica and O.verdickii had slightly more similar niches than the other Ottelia species.The present findings identify the need to enhance conservation efforts to safeguard natural Ottelia populations and provide a theoretical basis for the distribution of various Ottelia species in Africa.展开更多
Background:Small coastal wetlands are vital sites for wintering waterbirds.Identifying important habitats is critical for managing waterbirds effectively.The Vourkari inlet is a small coastal wetland located near the ...Background:Small coastal wetlands are vital sites for wintering waterbirds.Identifying important habitats is critical for managing waterbirds effectively.The Vourkari inlet is a small coastal wetland located near the capital Athens,within the most urbanized and industrialized area of Greece.We aimed at identifying the most important habitats for waterbirds at the Vourkari inlet during winter.Methods:Data about habitat use and availability were collected for 14 waterbird species and for seven habitat classes.Habitat selection(Manly’s selection ratio),overlap indices(Pianka’s niche overlap index)and null models were calculated.Results:All the studied waterbird species selected available habitats nonrandomly.Shallow waters(0–2 m),were used by 13 waterbirds and selected by five waterbirds.Pools and channels were used and selected by 10 species.Mud was used by nine species and selected by six species.Mud with rocky substrate was used by nine species and selected by eight species.Medium(2–4 m)and deep(4–6 m)open water habitats were used by seven species and selected by four species.Halophytic vegetation was used by six species and selected by two species.Several habitats were selected by nationally important populations:mudflat habitats(i.e.,mud,mud with rocky substrate and pools and channels)by Common Redshanks(Tringa totanus),halophytic vegetation by Little Egrets(Egretta garzetta),shallow waters by Common Shelducks(Tadorna tadorna)and medium and deep waters by Sandwich Terns(Thalasseus sandvicencis),whilst shallow waters and mudflat habitats were preferred by a possibly internationally important population of Mediterranean Gulls(Ichthyaetus melanocephalus).Although overlap in habitat use between species was generally low,null models indicated habitat sharing and a lack of competition.Conclusions:Waterbirds coexisted in the absence of competition for habitats at Vourkari,where they mostly used and preferred shallow water and mudflats.Small coastal wetlands are numerous,both in Greece and worldwide,therefore our findings would be useful as a basis for comparisons,both temporal at the inlet and spatial with other sites,that would help assess the importance of habitats and improve management strategies to benefit waterbirds,especially in areas with similar Mediterranean-type habitats and climate.展开更多
Resource depletion exerts opposing pressures on co-occurring consumers to expand diets while limiting overlap with competitors.Using foraging theory as a framework,we tested the effects of prey availability on diet sp...Resource depletion exerts opposing pressures on co-occurring consumers to expand diets while limiting overlap with competitors.Using foraging theory as a framework,we tested the effects of prey availability on diet spe-cialization and overlap among competing Asian predators:dhole,leopard,and tiger.We used scat analysis from a prey-poor site,combined with a quantitative synthesis of 40 other diet studies,to determine biomass of different prey types consumed by each predator.We then assessed diet composition in relation to prey density,and compared diet breadth and overlap between prey-poor and prey-rich sites.In prey rich areas,all three predators specialized on energetically profitable medium and large ungulates(>30 kg),resulting in narrow,overlapping niches.Each predator shifted toward less profitable small-bodied prey(≤30 kg)as preferred ungulates declined,whereas con-sumption of preferred ungulates was unrelated to small prey abundance,as predicted by foraging theory.Diet breadths doubled under prey depletion(except leopard),but overlap declined as diets diverged via species-specific traits that facilitated capture of different types of alternative prey.Asia’s apex predators adapt similarly to depletion of mutually preferred ungulates by switching to more numerous but less profitable small prey.Yet they can also partition a depleted prey base through intrinsic niche differences,thereby avoiding competitive exclusion.Our find-ings illuminate the stabilizing properties of adaptive foraging and niche differences in ecological communities,and provide insights into the behavior and resilience of Asia’s endangered apex predators in response to prey depletion in the heavily poached forests of this region.展开更多
基金Under the auspices of National Key Research and Development Program of China(No.2016YFC0500306)。
文摘This study aims to verify the concept of niches at multiple spatial scales in plant communities.To this end,we analyzed the niche characteristic of Rhododendron dauricum plant communities in Northeast China at three spatial scales.At the local scale,we calculated the Importance Value(IV)of species in five communities in the north of the Da Hinggan Mountains.At the intermediate scale,we examined five communities in their entirety,calculated the niche breadth of the species,and integrated niche overlap and interspecific association to analyze interspecific relationships.Further,the generalized additive model(GAM)was used to analyze the impact of topography and soil factors on niche characteristics.At the regional scale,we analyzed the geographical distribution of dominant species of R.dauricum plant communities in Northeast China and used principal component analysis(PCA)to analyze the impact of geographical and climate factors on species distribution.The results show that at the local scale,the IV of the species in each community varies widely.At the intermediate scale,species with a wide niche breadth tend to have a high value for IV.Larix gmelinii,Betula platyphylla,R.dauricum,Ledum palustre,and Vaccinium vitis-idaea had a relatively wide niche breadth and a high niche overlap,and the interspecific associations were almost all positive.Elevation and soil nutrients were the most dominant environmental factors.At the regional scale,species with a wide niche breadth tend to have a wide range of distribution,and temperature and precipitation were the most dominant environmental factors.This study suggests that the niche characteristics at three scales are both related and different.Niche characteristics at the local scale were various and labile,and niche characteristics at the intermediate and regional scales were relatively regular.These results show some degree of consistency with previous studies from an evolutionary perspective.The action mechanisms of these communities are related to differences in the dominant environmental factors.In addition,the integration of niche overlap and interspecific association determine interspecific relationships more accurately.
基金supported by the Jiangsu Science and Technology Special Project(Grant No.BX2019084)Research Startup Funding at Nanjing Forestry University(Grant No.163010230)the Faculty Startup Funding(to Arshad Ali)for establishing Forest Ecology Research Group at Hebei University(Special Project No.521100221033)。
文摘The influences of trait diversity(i.e.,the niche complementarity effect)and functional composition(i.e.,the mass ratio effect)on aboveground biomass(AGB)is a highly debated topic in forest ecology.Therefore,further studies are needed to explore these mechanisms in unstudied forest ecosystems to enhance our understanding,and to provide guidelines for specific forest management.Here,we hypothesized that functional composition would drive AGB better than trait diversity and stem size inequality in the(sub-)tropical forests of Nepal.Using data from 101 forest plots,we tested 25 structural equation models(SEMs)to link elevation,stem DBH inequality,trait diversity(i.e.,trait richness,evenness,dispersion and divergence),functional composition[i.e.,community-weighted of maximum height mean(CWM of Hmax),specific leaf area(CWM of SLA),leaf dry matter content(CWM of LDMC),and wood density(CWM of WD)]and AGB.The best-fitted SEMs indicated that CWM of Hmax promoted AGB while overruling the impacts of trait diversity indices on AGB.However,low trait diversity indices were linked with higher AGB while overruling the effects of CWM of SLA,LDMC and WD on AGB.In addition,AGB decreased with increasing elevation,whereas stem size inequality did not influence AGB.Our results suggest that divergent species’functional strategies could shape AGB along an altitudinal gradient in tropical forests.We argue that forest management practices should include plant functional traits in the management plan for the co-benefits of biodiversity conservation and carbon sequestration that underpins human wellbeing.
基金funded by the Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDB 31000000)the National Natural Science Foundation of China (Nos.32070253 and 32100186)the Sino-Africa Joint Research Center (No. SAJC201322)
文摘Understanding the influence of environmental covariates on plant distribution is critical,especially for aquatic plant species.Climate change is likely to alter the distribution of aquatic species.However,knowledge of this change on the burden of aquatic macroorganisms is often fraught with difficulty.Ottelia,a model genus for studying the evolution of the aquatic family Hydrocharitaceae,is mainly distributed in slow-flowing creeks,rivers,or lakes throughout pantropical regions in the world.Due to recent rapid climate changes,natural Ottelia populations have declined significantly.By modeling the effects of climate change on the distribution of Ottelia species and assessing the degree of niche similarity,we sought to identify high suitability regions and help formulate conservation strategies.The models use known background points to determine how environmental covariates vary spatially and produce continental maps of the distribution of the Ottelia species in Africa.Additionally,we estimated the possible influences of the optimistic and extreme pessimistic representative concentration pathways scenarios RCP 4.5 and RCP 8.5 for the 2050s.Our results show that the distinct distribution patterns of studied Ottelia species were influenced by topography(elevation)and climate(e.g.,mean temperature of driest quarter,annual precipitation,and precipitation of the driest month).While there is a lack of accord in defining the limiting factors for the distribution of Ottelia species,it is clear that water-temperature conditions have promising effects when kept within optimal ranges.We also note that climate change will impact Ottelia by accelerating fragmentation and habitat loss.The assessment of niche overlap revealed that Ottelia cylindrica and O.verdickii had slightly more similar niches than the other Ottelia species.The present findings identify the need to enhance conservation efforts to safeguard natural Ottelia populations and provide a theoretical basis for the distribution of various Ottelia species in Africa.
文摘Background:Small coastal wetlands are vital sites for wintering waterbirds.Identifying important habitats is critical for managing waterbirds effectively.The Vourkari inlet is a small coastal wetland located near the capital Athens,within the most urbanized and industrialized area of Greece.We aimed at identifying the most important habitats for waterbirds at the Vourkari inlet during winter.Methods:Data about habitat use and availability were collected for 14 waterbird species and for seven habitat classes.Habitat selection(Manly’s selection ratio),overlap indices(Pianka’s niche overlap index)and null models were calculated.Results:All the studied waterbird species selected available habitats nonrandomly.Shallow waters(0–2 m),were used by 13 waterbirds and selected by five waterbirds.Pools and channels were used and selected by 10 species.Mud was used by nine species and selected by six species.Mud with rocky substrate was used by nine species and selected by eight species.Medium(2–4 m)and deep(4–6 m)open water habitats were used by seven species and selected by four species.Halophytic vegetation was used by six species and selected by two species.Several habitats were selected by nationally important populations:mudflat habitats(i.e.,mud,mud with rocky substrate and pools and channels)by Common Redshanks(Tringa totanus),halophytic vegetation by Little Egrets(Egretta garzetta),shallow waters by Common Shelducks(Tadorna tadorna)and medium and deep waters by Sandwich Terns(Thalasseus sandvicencis),whilst shallow waters and mudflat habitats were preferred by a possibly internationally important population of Mediterranean Gulls(Ichthyaetus melanocephalus).Although overlap in habitat use between species was generally low,null models indicated habitat sharing and a lack of competition.Conclusions:Waterbirds coexisted in the absence of competition for habitats at Vourkari,where they mostly used and preferred shallow water and mudflats.Small coastal wetlands are numerous,both in Greece and worldwide,therefore our findings would be useful as a basis for comparisons,both temporal at the inlet and spatial with other sites,that would help assess the importance of habitats and improve management strategies to benefit waterbirds,especially in areas with similar Mediterranean-type habitats and climate.
基金funded by Fran-cois and Sheila Brutsch,WWF Germany,WWF France,WWF US,WWF Sweden,WWF Denmark,WWF Aus-tria,The Rhino and Tiger Conservation Fund(U.S.Fish and Wildlife Service),and Keidanren Nature Conserva-tion Fund.
文摘Resource depletion exerts opposing pressures on co-occurring consumers to expand diets while limiting overlap with competitors.Using foraging theory as a framework,we tested the effects of prey availability on diet spe-cialization and overlap among competing Asian predators:dhole,leopard,and tiger.We used scat analysis from a prey-poor site,combined with a quantitative synthesis of 40 other diet studies,to determine biomass of different prey types consumed by each predator.We then assessed diet composition in relation to prey density,and compared diet breadth and overlap between prey-poor and prey-rich sites.In prey rich areas,all three predators specialized on energetically profitable medium and large ungulates(>30 kg),resulting in narrow,overlapping niches.Each predator shifted toward less profitable small-bodied prey(≤30 kg)as preferred ungulates declined,whereas con-sumption of preferred ungulates was unrelated to small prey abundance,as predicted by foraging theory.Diet breadths doubled under prey depletion(except leopard),but overlap declined as diets diverged via species-specific traits that facilitated capture of different types of alternative prey.Asia’s apex predators adapt similarly to depletion of mutually preferred ungulates by switching to more numerous but less profitable small prey.Yet they can also partition a depleted prey base through intrinsic niche differences,thereby avoiding competitive exclusion.Our find-ings illuminate the stabilizing properties of adaptive foraging and niche differences in ecological communities,and provide insights into the behavior and resilience of Asia’s endangered apex predators in response to prey depletion in the heavily poached forests of this region.
