Aims Large hurricanes have profound impacts on temperate forests,but owing to their infrequent nature these effects have rarely been examined in detail.In 1996,Hurricane Fran significantly damaged many long-term tree ...Aims Large hurricanes have profound impacts on temperate forests,but owing to their infrequent nature these effects have rarely been examined in detail.In 1996,Hurricane Fran significantly damaged many long-term tree census plots in the Duke Forest on the North Carolina Piedmont,thereby providing an exceptional opportunity to examine pre-and post-hurricane forest compositional trajectories.Our goal was to examine immediate,short-term(0–4 years)and longer term(;5 year)hurricane-induced structural,spatial and compositional changes in the tree population(stem d.b.h>1 cm)in the context of our detailed,long-term knowledge of the dynamics of these forests.Methods We surveyed stem damage and tree mortality in 34 long-term permanent plots(ca.70-year record;404–1012 m^(2))and 7 large mapped tree stands(ca.20-year record;5250–65000 m^(2))representing both transition-phase,even-aged pine stands and uneven-aged upland hardwood forests.We employed three types of damage measures to quantify stand-level damage severity:percentage of stems damaged,percentage of basal area lost and a‘stand-level damage index’.Second-order spatial analysis(Ripley’s K-function)was used to investigate patterns in tree mortality.Important findings Our study found hurricane effects on the structural attributes of Piedmont forests to be variable and patchy.Changes in tree species composition,however,were modest.Uprooting was the major damage type for the overstory trees[diameter at breast height(d.b.h.)>10 cm]apparently due to the exposure of the crowns to high wind combined with heavy rainfall prior to and during the storm.Saplings,juvenile trees and small trees(1–10 cm d.b.h.)of the understory and midstory were mainly damaged by being pinned or bent by their damaged large neighbors.Hurricane-induced tree mortality varied weakly among species,was positively correlated with pre-hurricane tree size and remained up to 2-fold higher than pre-hurricane background mortality 5 years after the hurricane.Spatial point pattern analysis revealed a 展开更多
Tree mortality significantly influences forest structure and function,yet our understanding of its dynamic patterns among a range of tree sizes and among different plant functional types(PFTs)remains incomplete.This s...Tree mortality significantly influences forest structure and function,yet our understanding of its dynamic patterns among a range of tree sizes and among different plant functional types(PFTs)remains incomplete.This study analysed size-dependent tree mortality in a temperate forest,encompassing 46 tree species and 32,565 individuals across different PFTs(i.e.,evergreen conifer vs.deciduous broadleaf species,shade-tolerant vs.shade-intolerant species).By employing all-subset regression procedures and logistic generalized linear mixed-effects models,we identified distinct mortality patterns influenced by biotic and abiotic factors.Our results showed a stable mortality patte rn in eve rgreen conifer species,contrasted by a declining pattern in deciduous broadleaf and shadetolerant,as well as shade-intolerant species,across size classes.The contribution to tree mortality of evergreen conifer species shifted from abiotic to biotic factors with increasing size,while the mortality of deciduous broadleaf species was mainly influenced by biotic factors,such as initial diameter at breast height(DBH)and conspecific negative density.For shade-tolerant species,the mortality of small individuals was mainly determined by initial DBH and conspecific negative density dependence,whereas the mortality of large individuals was subjected to the combined effect of biotic(competition from neighbours)and abiotic factors(i.e.,convexity and pH).As for shade-intolerant species,competition from neighbours was found to be the main driver of tree mortality throughout their growth stages.Thus,these insights enhance our understanding of forest dynamics by revealing the size-dependent and PFT-specific tree mortality patterns,which may inform strategies for maintaining forest diversity and resilience in temperate forest ecosystems.展开更多
We used 11 years of census data from 450 seedling quadrats established in a 20-ha forest dynamics plot to study seedling dynamics in tree species of a tropical seasonal rainforest in Xishuangbanna,southwestern China.W...We used 11 years of census data from 450 seedling quadrats established in a 20-ha forest dynamics plot to study seedling dynamics in tree species of a tropical seasonal rainforest in Xishuangbanna,southwestern China.We found that overall seedling recruitment rate and relative growth rate were higher in the rainy season than in the dry season.Both the recruitment rate of seedlings from canopy tree species(two species)and the relative growth rate of seedlings from understory species(nine species)were higher in the rainy season than in the dry season.However,in the rainy season,the recruitment rate of seedlings was higher for canopy tree species than for understory tree species.In addition,relative growth rate of seedlings was higher in the canopy species than in understory seedlings in the dry season.We also observed that,in both rainy and dry seasons,mortality rate of seedlings was higher for canopy species than for understory species.Overall,canopy tree species appear to have evolved a flexible strategy to adapt to the seasonal changes of a monsoon climate.In contrast,understory tree species seem to have adopted a conservative strategy.Specifically,these species mainly release seedlings in the rainy season and maintain relatively stable populations with a lower mortality rate and recruitment rate in both dry and rainy seasons.Our study suggests that canopy and understory seedling populations growing in forest understory may respond to future climate change scenarios with distinct regeneration strategies.展开更多
基金supported by W.C.Coker and A.H.Beers fellowships and a Dissertation Completion Fellowship from the University of North Carolina at Chapel Hill to W.X.and a grant from the National Science Foundation(DEB-97-07551)to R.K.P.and D.L.U.
文摘Aims Large hurricanes have profound impacts on temperate forests,but owing to their infrequent nature these effects have rarely been examined in detail.In 1996,Hurricane Fran significantly damaged many long-term tree census plots in the Duke Forest on the North Carolina Piedmont,thereby providing an exceptional opportunity to examine pre-and post-hurricane forest compositional trajectories.Our goal was to examine immediate,short-term(0–4 years)and longer term(;5 year)hurricane-induced structural,spatial and compositional changes in the tree population(stem d.b.h>1 cm)in the context of our detailed,long-term knowledge of the dynamics of these forests.Methods We surveyed stem damage and tree mortality in 34 long-term permanent plots(ca.70-year record;404–1012 m^(2))and 7 large mapped tree stands(ca.20-year record;5250–65000 m^(2))representing both transition-phase,even-aged pine stands and uneven-aged upland hardwood forests.We employed three types of damage measures to quantify stand-level damage severity:percentage of stems damaged,percentage of basal area lost and a‘stand-level damage index’.Second-order spatial analysis(Ripley’s K-function)was used to investigate patterns in tree mortality.Important findings Our study found hurricane effects on the structural attributes of Piedmont forests to be variable and patchy.Changes in tree species composition,however,were modest.Uprooting was the major damage type for the overstory trees[diameter at breast height(d.b.h.)>10 cm]apparently due to the exposure of the crowns to high wind combined with heavy rainfall prior to and during the storm.Saplings,juvenile trees and small trees(1–10 cm d.b.h.)of the understory and midstory were mainly damaged by being pinned or bent by their damaged large neighbors.Hurricane-induced tree mortality varied weakly among species,was positively correlated with pre-hurricane tree size and remained up to 2-fold higher than pre-hurricane background mortality 5 years after the hurricane.Spatial point pattern analysis revealed a
基金supported by the China Postdoctoral Science Foundation (No.2023M733712)the National Natural Science Foundation of China (No.31971491)。
文摘Tree mortality significantly influences forest structure and function,yet our understanding of its dynamic patterns among a range of tree sizes and among different plant functional types(PFTs)remains incomplete.This study analysed size-dependent tree mortality in a temperate forest,encompassing 46 tree species and 32,565 individuals across different PFTs(i.e.,evergreen conifer vs.deciduous broadleaf species,shade-tolerant vs.shade-intolerant species).By employing all-subset regression procedures and logistic generalized linear mixed-effects models,we identified distinct mortality patterns influenced by biotic and abiotic factors.Our results showed a stable mortality patte rn in eve rgreen conifer species,contrasted by a declining pattern in deciduous broadleaf and shadetolerant,as well as shade-intolerant species,across size classes.The contribution to tree mortality of evergreen conifer species shifted from abiotic to biotic factors with increasing size,while the mortality of deciduous broadleaf species was mainly influenced by biotic factors,such as initial diameter at breast height(DBH)and conspecific negative density.For shade-tolerant species,the mortality of small individuals was mainly determined by initial DBH and conspecific negative density dependence,whereas the mortality of large individuals was subjected to the combined effect of biotic(competition from neighbours)and abiotic factors(i.e.,convexity and pH).As for shade-intolerant species,competition from neighbours was found to be the main driver of tree mortality throughout their growth stages.Thus,these insights enhance our understanding of forest dynamics by revealing the size-dependent and PFT-specific tree mortality patterns,which may inform strategies for maintaining forest diversity and resilience in temperate forest ecosystems.
基金supported by the NSFC China-US Dimensions of Biodiversity Grant (DEB: 32061123003)National Natural Science Foundation of China (31870410, 32171507)+3 种基金the Chinese Academy of Sciences Youth Innovation Promotion Association (Y202080)the Distinguished Youth Scholar of Yunnan (202001AV070016)the West Light Foundation of the Chinese Academy of Sciencesthe Ten Thousand Talent Plans for Young Top-notch Talents of Yunnan (YNWR-QNBJ-2018-309)
文摘We used 11 years of census data from 450 seedling quadrats established in a 20-ha forest dynamics plot to study seedling dynamics in tree species of a tropical seasonal rainforest in Xishuangbanna,southwestern China.We found that overall seedling recruitment rate and relative growth rate were higher in the rainy season than in the dry season.Both the recruitment rate of seedlings from canopy tree species(two species)and the relative growth rate of seedlings from understory species(nine species)were higher in the rainy season than in the dry season.However,in the rainy season,the recruitment rate of seedlings was higher for canopy tree species than for understory tree species.In addition,relative growth rate of seedlings was higher in the canopy species than in understory seedlings in the dry season.We also observed that,in both rainy and dry seasons,mortality rate of seedlings was higher for canopy species than for understory species.Overall,canopy tree species appear to have evolved a flexible strategy to adapt to the seasonal changes of a monsoon climate.In contrast,understory tree species seem to have adopted a conservative strategy.Specifically,these species mainly release seedlings in the rainy season and maintain relatively stable populations with a lower mortality rate and recruitment rate in both dry and rainy seasons.Our study suggests that canopy and understory seedling populations growing in forest understory may respond to future climate change scenarios with distinct regeneration strategies.
