The structure of plant communities at local scales depends on both the spatial heterogeneity of abiotic environmental factors and the biotic interactions within the community.However,although environmental filtering d...The structure of plant communities at local scales depends on both the spatial heterogeneity of abiotic environmental factors and the biotic interactions within the community.However,although environmental filtering due to microtopographic heterogeneity and resource competition among plants caused by spatial variation in tree density and size are considered to be very important in explaining the mechanisms of community assembly,their effects on the processes of individual mortality and recruitment in natural forest regeneration,as well as their relative contributions,are still poorly understood.To address this,we established a 12-ha permanent plot in a subtropical evergreen broad-leaved forest area and measured microtopographic variables such as elevation,slope,aspect,and terrain position index(TPI)using a total station.We monitored the individual mortality and recruitment in forest natural regeneration through repeated surveys at 5-year intervals.We fitted spatial covariance models to jointly use multiple factors from three groups of variables(microtopographic effect,neighborhood density effects,neighborhood size effects)as explanatory variables to analyze their roles in driving the mortality and recruitment of all individual and 12 dominant species in forest natural regeneration at the neighborhood scale.Our results show that:(1)In the crucial early stages of secondary forest restoration,natural regeneration is influenced by a synergy of environmental filtering,due to microtopographic heterogeneity,and resource competition among plants.(2)For distinct species responses,evergreen dominant species'mortality is largely explained by neighborhood effects,while deciduous species are more affected by topographic factors.Furthermore,the adverse effects of larger conspecific trees on younger trees indicate a pattern of competitive pressure leading to mortality among regenerating trees,such pattern emphasis the influence of parent trees on natural regeneration.(3)As trees grow,their interaction with these stressors evolves,suggesting a shift in their resource acquisition strategies and response to neighborhood effects and environmental factors.Despite these changes,the relative importance of topographic factors in determining survival and recruitment success remains constant.This research highlights the importance of considering both environmental and neighborhood effects in forest management,particularly in early secondary forest restoration.展开更多
Background: The Red-crowned Crane(Grus japonensis) is an endangered bird species and while the wild population continues to decrease in China, the captive population has dramatically increased over the last two decade...Background: The Red-crowned Crane(Grus japonensis) is an endangered bird species and while the wild population continues to decrease in China, the captive population has dramatically increased over the last two decades. We hypothesized that some of the captive Red-crowned Cranes originated from the wild and that a growing captive population is eroding the wild population in China.Methods: We surveyed the size of the population and determined the average annual growth rate, reproductive success rate and mortality rate of captive Red-crowned Cranes in 2013 in China. We assessed this erosion effect through mathematical models, in which the size of the captive Red-crowned Crane population was determined from the annual growth rate, the reproductive success rate and the rate of mortality.Results: We found there were a total of 1520 captive Red-crowned Cranes in 2013 in China, with an average annual gro-wth rate of 7.46%, a reproductive success rate of 9.17% and a mortality rate of 3.6%. We found that approximately 1027 supplementary Red-crowned Cranes per year and a total of 244, over the 14 year period from 1999 to 2013, were needed to account for the growing captive population in China.Conclusion: We conclude that the 244 birds probably came from the wild by taking eggs and capturing juveniles or adults and hence accepted the hypothesis. Perhaps more surprisingly, our annual estimate of the number of supplementary Red-crowned Cranes in captive populations is very conservative, with the erosion effect substantially underestimated, because the total number of captive Red-crowned Cranes in 2013 was underestimated, with the annual reproductive success rate in zoos overestimated. The existence of an erosion effect provides a new perspective for the interpretation of why the Red-crowned Crane population in the wild continues to decrease. In our opinion, it is important to understand the consequences of this erosion effect on the management and conservation of this endangered bird species in China.展开更多
基金the Innovative Team Project of Nanjing Institute of Environmental Sciences MEE(ZX2023QT022)Sino-German Environmental Partnership PhaseⅢ:Strengthening Chinese environmental and nature conservation policy through dialogue+2 种基金The Central Public Welfare Scientific Institution Basal Research Fund,MEE(GYZX210302)Biodiversity Survey,Observation and Assessment Program of Ministry of Ecology and Environment of ChinaThe National Environmental Protection Public Welfare Industry Targeted Research Fund:Research and demonstration of key technologies for dynamic supervision of nature reserves(201509042)。
文摘The structure of plant communities at local scales depends on both the spatial heterogeneity of abiotic environmental factors and the biotic interactions within the community.However,although environmental filtering due to microtopographic heterogeneity and resource competition among plants caused by spatial variation in tree density and size are considered to be very important in explaining the mechanisms of community assembly,their effects on the processes of individual mortality and recruitment in natural forest regeneration,as well as their relative contributions,are still poorly understood.To address this,we established a 12-ha permanent plot in a subtropical evergreen broad-leaved forest area and measured microtopographic variables such as elevation,slope,aspect,and terrain position index(TPI)using a total station.We monitored the individual mortality and recruitment in forest natural regeneration through repeated surveys at 5-year intervals.We fitted spatial covariance models to jointly use multiple factors from three groups of variables(microtopographic effect,neighborhood density effects,neighborhood size effects)as explanatory variables to analyze their roles in driving the mortality and recruitment of all individual and 12 dominant species in forest natural regeneration at the neighborhood scale.Our results show that:(1)In the crucial early stages of secondary forest restoration,natural regeneration is influenced by a synergy of environmental filtering,due to microtopographic heterogeneity,and resource competition among plants.(2)For distinct species responses,evergreen dominant species'mortality is largely explained by neighborhood effects,while deciduous species are more affected by topographic factors.Furthermore,the adverse effects of larger conspecific trees on younger trees indicate a pattern of competitive pressure leading to mortality among regenerating trees,such pattern emphasis the influence of parent trees on natural regeneration.(3)As trees grow,their interaction with these stressors evolves,suggesting a shift in their resource acquisition strategies and response to neighborhood effects and environmental factors.Despite these changes,the relative importance of topographic factors in determining survival and recruitment success remains constant.This research highlights the importance of considering both environmental and neighborhood effects in forest management,particularly in early secondary forest restoration.
基金supported by the Special Fund for Basic Scientific Research of the Central Public Welfare Research Institutes (2013)the National Natural Science Foundation of China (No.31300350)+2 种基金the Jiangsu Provincial Natural Science Foundation of China (No.2011079)the Baseline Surveys and Assessments of Nature Reserves in China (No.HBSY0915)the State Environmental Protection Public Welfare Scientific Research Project (No.201209028)
文摘Background: The Red-crowned Crane(Grus japonensis) is an endangered bird species and while the wild population continues to decrease in China, the captive population has dramatically increased over the last two decades. We hypothesized that some of the captive Red-crowned Cranes originated from the wild and that a growing captive population is eroding the wild population in China.Methods: We surveyed the size of the population and determined the average annual growth rate, reproductive success rate and mortality rate of captive Red-crowned Cranes in 2013 in China. We assessed this erosion effect through mathematical models, in which the size of the captive Red-crowned Crane population was determined from the annual growth rate, the reproductive success rate and the rate of mortality.Results: We found there were a total of 1520 captive Red-crowned Cranes in 2013 in China, with an average annual gro-wth rate of 7.46%, a reproductive success rate of 9.17% and a mortality rate of 3.6%. We found that approximately 1027 supplementary Red-crowned Cranes per year and a total of 244, over the 14 year period from 1999 to 2013, were needed to account for the growing captive population in China.Conclusion: We conclude that the 244 birds probably came from the wild by taking eggs and capturing juveniles or adults and hence accepted the hypothesis. Perhaps more surprisingly, our annual estimate of the number of supplementary Red-crowned Cranes in captive populations is very conservative, with the erosion effect substantially underestimated, because the total number of captive Red-crowned Cranes in 2013 was underestimated, with the annual reproductive success rate in zoos overestimated. The existence of an erosion effect provides a new perspective for the interpretation of why the Red-crowned Crane population in the wild continues to decrease. In our opinion, it is important to understand the consequences of this erosion effect on the management and conservation of this endangered bird species in China.
