Seedling stage has long been recognized as the bottleneck of forest regeneration,and the biotic and abiotic processes that dominate at seedling stage largely affect the dynamics of forest.Seedlings might be particular...Seedling stage has long been recognized as the bottleneck of forest regeneration,and the biotic and abiotic processes that dominate at seedling stage largely affect the dynamics of forest.Seedlings might be particularly vulnerable to climate stress,so elucidating the role of interannual climate variation in fostering community dynamics is crucial to understanding the response of forest to climate change.Using seedling survival data of 69 woody species collected for five consecutive years from a 25-ha permanent plot in a temperate deciduous forest,we identified the effects of biotic interactions and habitat factors on seedling survival,and examined how those effects changed over time.We found that interannual climate variations,followed by biotic interactions and habitat conditions,were the most significant predictors of seedling survival.Understory light showed a positive impact on seedling mortality,and seedling survival responded differently to soil and air temperature.Effects of conspecific neighbor density were significantly strengthened with the increase of maximum air temperature and vapor pressure deficits in the growing season,but were weakened by increased maximum soil temperature and precipitation in the non-growing season.Surprisingly,seedling survival was strongly correlated with interannual climate variability at all life stages,and the strength of the correlation increased with seedling age.In addition,the importance of biotic and abiotic factors on seedling survival differed significantly among species-trait groups.Thus,the neighborhood-mediated effects on mortality might be significantly contributing or even inverting the direct effects of varying abiotic conditions on seedling survival,and density-dependent effects could not be the only important factor influencing seedling survival at an early stage.展开更多
Biodiversity conservation has long been a subject of extreme interest to community ecologists,with a particular focus on exploring the underlying causes of species diversity based on niche and neutral theories.This st...Biodiversity conservation has long been a subject of extreme interest to community ecologists,with a particular focus on exploring the underlying causes of species diversity based on niche and neutral theories.This study aims to identify the potential determinants of species diversity in a deciduous broad-leaved forest in the transitional region from subtropical to temperate climate in China.We collected woody plant data and environmental variables in a fully mapped 25-ha permanent forest plot,partitioned the beta-diversity into local contributions(LCBD)and species contributions(SCBD),and then applied multivariate linear regression analysis to test the effects of biotic and abiotic factors on alpha-diversity,LCBD,and SCBD.We used variation partitioning in combination with environmental variables and spatial distance to determine the contribution of environment-related variations versus spatial variations.Our results showed that the indices of alpha-diversity(i.e.,species abundance and richness)were positively correlated with soil available phosphorus(P)and negatively with slope.For the betadiversity,environment and space together explained nearly half of the variations in community composition.Approximately 60%of the variation of LCBD in the understory layer,40%in the substory layer,and 29%in the canopy layer were jointly explained by topographic,soil and biological variables,with biotic factors playing a dominant role in determining the beta-diversity.Species abundance accounted for a large proportion of the variations in SCBD in each vertical stratum,and niche position(NP)was the ecological trait that significantly affected the variations in SCBD in the substory and canopy layers.Our findings help to gain better understanding on how species diversity in forest ecosystem responds to environmental conditions and how it is influenced by biotic factors and ecological traits of species.展开更多
Aims Age structure and regeneration dynamics have been used to infer population response to environmental events and reconstruct forest development history.The aim of this study was to characterize and examine the dif...Aims Age structure and regeneration dynamics have been used to infer population response to environmental events and reconstruct forest development history.The aim of this study was to characterize and examine the differences of the age structure and regeneration dynamics of subalpine fir(Abies fargesii)forest across the altitudinal range in the north and south aspects in the Shennongjia Mountains,central China.Methods Ten plots(20×20 m)at each altitudinal zone(i.e.the low elevation,the middle elevation and the high elevation)were established in both the north and south aspects of the Shennongjia Mountains,central China.Dendroecological techniques were applied to obtain information about ages of the trees in the plots.The population age structure was analyzed to investigate the regeneration dynamics across the altitudinal range.Important findings Fir regeneration dynamics and age structure were similar in both aspects,and a unimodal population age structure was found at different altitudinal sites of both aspects,indicating that environmental factors might play an important role in shaping the regeneration dynamics and age structure of A.fargesii across its altitudinal range.There was a sustained recruitment during the 19th century,but the regeneration was rarer in the last century at low and midelevations.A significant greater number of fir seedlings and saplings recruited at high elevations in the last century,and fir tree density at high elevations was significantly higher than that at low elevations.Thus,the fir population at the high elevations showed a significant increase in recruitment and stem density in the last century,and we propose that the gradual infilling of fir seedlings might result in changes in regeneration dynamics and stand structure of the subalpine fir forest at high elevations in the Shennongjia Mountains,central China.展开更多
Aims Terrestrial net primary production(NPP),the balance of gross primary production(GPP)and autotrophic respiration(AR),is a critical measure of carbon sequestration capacity for the Earth’s land surface.The aim of ...Aims Terrestrial net primary production(NPP),the balance of gross primary production(GPP)and autotrophic respiration(AR),is a critical measure of carbon sequestration capacity for the Earth’s land surface.The aim of this study was to understand the spatio-temporal variability of NPP associated with GPP and AR in the Yangtze River Basin(YRB),China,from 2000 to 2009 during which the basin warmed significantly.Methods We first derived AR and carbon-use efficiency(CUE)from the improved Moderate Resolution Imaging Spectroradiometer GPP/NPP products(MOD17)and then conducted spatial analysis to quantify how NPP relates to GPP,AR and their relationship with key observed climate variables(temperature,precipitation and sunshine percentage)in the YRB during 2000–2009.Important Findings The spatial pattern of NPP in the YRB was predominantly determined by GPP and further modified by AR.Higher GPP and relatively low AR made the southern Jinshajiang sub-basin the most productive area in NPP in the YRB.A large portion of the YRB experienced a warmer and drier climate trend in the growing season during 2000–2009.In the upper reaches of the basin,possessing a relatively low temperature base,increases in temperature led to greater increases in GPP than those in AR,resulting in greater increased NPP.However,in the middle and lower reaches of the basin where the base temperature is relatively high,increases in temperature led to greater increases in AR than those in GPP,leading to decreases in NPP.Overall,86.7%of the vegetated area showed a consistent GPP and NPP trend through time with 71.3%of the vegetated area having a positive trend both in GPP and NPP,and the remaining 13.3%of vegetated areas showed an opposite trend in GPP and NPP,with positive GPP and negative NPP trajectories dominating(10.1%of vegetated area)the trend.Although climate warming generally had positive effects on vegetation growth in most areas of the basin,areas with increased NPP(74.5%)were less extensive than those with increased GPP(81.4%)due to the wider increase in AR(82.2%).During the study period,increases in AR offset 62%of the total increased GPP,leading to a substantial decline of CUE,particularly in the warmer lower altitude regions in the southeast.Our work reveals the diverse responses of NPP associated with GPP and AR as the climate warms and generally suggests that NPP in the middle and lower sub-basins in the YRB is more sensitive to future climate warming.These findings enhance our understanding of terrestrial ecosystem carbon dynamics in response to global warming and provide a scientific basis for managing ecosystem productivity in the YRB,China.展开更多
基金The National Natural Science Foundation of China provided funding for this project(Nos.31971491,32201371).
文摘Seedling stage has long been recognized as the bottleneck of forest regeneration,and the biotic and abiotic processes that dominate at seedling stage largely affect the dynamics of forest.Seedlings might be particularly vulnerable to climate stress,so elucidating the role of interannual climate variation in fostering community dynamics is crucial to understanding the response of forest to climate change.Using seedling survival data of 69 woody species collected for five consecutive years from a 25-ha permanent plot in a temperate deciduous forest,we identified the effects of biotic interactions and habitat factors on seedling survival,and examined how those effects changed over time.We found that interannual climate variations,followed by biotic interactions and habitat conditions,were the most significant predictors of seedling survival.Understory light showed a positive impact on seedling mortality,and seedling survival responded differently to soil and air temperature.Effects of conspecific neighbor density were significantly strengthened with the increase of maximum air temperature and vapor pressure deficits in the growing season,but were weakened by increased maximum soil temperature and precipitation in the non-growing season.Surprisingly,seedling survival was strongly correlated with interannual climate variability at all life stages,and the strength of the correlation increased with seedling age.In addition,the importance of biotic and abiotic factors on seedling survival differed significantly among species-trait groups.Thus,the neighborhood-mediated effects on mortality might be significantly contributing or even inverting the direct effects of varying abiotic conditions on seedling survival,and density-dependent effects could not be the only important factor influencing seedling survival at an early stage.
基金supported by the National Natural Science Foundation of China(Nos.31971491,31770517)the Meituan Qingshan Special Commonweal Fund of China Environmental Protection Foundation(CEPFQS202169-20)。
文摘Biodiversity conservation has long been a subject of extreme interest to community ecologists,with a particular focus on exploring the underlying causes of species diversity based on niche and neutral theories.This study aims to identify the potential determinants of species diversity in a deciduous broad-leaved forest in the transitional region from subtropical to temperate climate in China.We collected woody plant data and environmental variables in a fully mapped 25-ha permanent forest plot,partitioned the beta-diversity into local contributions(LCBD)and species contributions(SCBD),and then applied multivariate linear regression analysis to test the effects of biotic and abiotic factors on alpha-diversity,LCBD,and SCBD.We used variation partitioning in combination with environmental variables and spatial distance to determine the contribution of environment-related variations versus spatial variations.Our results showed that the indices of alpha-diversity(i.e.,species abundance and richness)were positively correlated with soil available phosphorus(P)and negatively with slope.For the betadiversity,environment and space together explained nearly half of the variations in community composition.Approximately 60%of the variation of LCBD in the understory layer,40%in the substory layer,and 29%in the canopy layer were jointly explained by topographic,soil and biological variables,with biotic factors playing a dominant role in determining the beta-diversity.Species abundance accounted for a large proportion of the variations in SCBD in each vertical stratum,and niche position(NP)was the ecological trait that significantly affected the variations in SCBD in the substory and canopy layers.Our findings help to gain better understanding on how species diversity in forest ecosystem responds to environmental conditions and how it is influenced by biotic factors and ecological traits of species.
基金National Natural Science Foundation of China(31270011,31130010)the Chinese Academy of Sciences(KSCX2-EW-Q-16,XDA05090305)National Key Technology Research and Development Program(2011BAD31B02).
文摘Aims Age structure and regeneration dynamics have been used to infer population response to environmental events and reconstruct forest development history.The aim of this study was to characterize and examine the differences of the age structure and regeneration dynamics of subalpine fir(Abies fargesii)forest across the altitudinal range in the north and south aspects in the Shennongjia Mountains,central China.Methods Ten plots(20×20 m)at each altitudinal zone(i.e.the low elevation,the middle elevation and the high elevation)were established in both the north and south aspects of the Shennongjia Mountains,central China.Dendroecological techniques were applied to obtain information about ages of the trees in the plots.The population age structure was analyzed to investigate the regeneration dynamics across the altitudinal range.Important findings Fir regeneration dynamics and age structure were similar in both aspects,and a unimodal population age structure was found at different altitudinal sites of both aspects,indicating that environmental factors might play an important role in shaping the regeneration dynamics and age structure of A.fargesii across its altitudinal range.There was a sustained recruitment during the 19th century,but the regeneration was rarer in the last century at low and midelevations.A significant greater number of fir seedlings and saplings recruited at high elevations in the last century,and fir tree density at high elevations was significantly higher than that at low elevations.Thus,the fir population at the high elevations showed a significant increase in recruitment and stem density in the last century,and we propose that the gradual infilling of fir seedlings might result in changes in regeneration dynamics and stand structure of the subalpine fir forest at high elevations in the Shennongjia Mountains,central China.
基金The National Natural Science Foundation of China(31130010)The Chinese Academy of Sciences(XDA05060500).
文摘Aims Terrestrial net primary production(NPP),the balance of gross primary production(GPP)and autotrophic respiration(AR),is a critical measure of carbon sequestration capacity for the Earth’s land surface.The aim of this study was to understand the spatio-temporal variability of NPP associated with GPP and AR in the Yangtze River Basin(YRB),China,from 2000 to 2009 during which the basin warmed significantly.Methods We first derived AR and carbon-use efficiency(CUE)from the improved Moderate Resolution Imaging Spectroradiometer GPP/NPP products(MOD17)and then conducted spatial analysis to quantify how NPP relates to GPP,AR and their relationship with key observed climate variables(temperature,precipitation and sunshine percentage)in the YRB during 2000–2009.Important Findings The spatial pattern of NPP in the YRB was predominantly determined by GPP and further modified by AR.Higher GPP and relatively low AR made the southern Jinshajiang sub-basin the most productive area in NPP in the YRB.A large portion of the YRB experienced a warmer and drier climate trend in the growing season during 2000–2009.In the upper reaches of the basin,possessing a relatively low temperature base,increases in temperature led to greater increases in GPP than those in AR,resulting in greater increased NPP.However,in the middle and lower reaches of the basin where the base temperature is relatively high,increases in temperature led to greater increases in AR than those in GPP,leading to decreases in NPP.Overall,86.7%of the vegetated area showed a consistent GPP and NPP trend through time with 71.3%of the vegetated area having a positive trend both in GPP and NPP,and the remaining 13.3%of vegetated areas showed an opposite trend in GPP and NPP,with positive GPP and negative NPP trajectories dominating(10.1%of vegetated area)the trend.Although climate warming generally had positive effects on vegetation growth in most areas of the basin,areas with increased NPP(74.5%)were less extensive than those with increased GPP(81.4%)due to the wider increase in AR(82.2%).During the study period,increases in AR offset 62%of the total increased GPP,leading to a substantial decline of CUE,particularly in the warmer lower altitude regions in the southeast.Our work reveals the diverse responses of NPP associated with GPP and AR as the climate warms and generally suggests that NPP in the middle and lower sub-basins in the YRB is more sensitive to future climate warming.These findings enhance our understanding of terrestrial ecosystem carbon dynamics in response to global warming and provide a scientific basis for managing ecosystem productivity in the YRB,China.