Forests are dynamic in both structure and species composition, and these dynamics are strongly influenced by climate. However, the net effects of future tree species composition on net primary production （NPP） are n...Forests are dynamic in both structure and species composition, and these dynamics are strongly influenced by climate. However, the net effects of future tree species composition on net primary production （NPP） are not well understood. The objective of this work was to model the potential range shifts of tree species （DISTRIB Model） and predict their impacts on NPP （PnET-Ⅱ Model） that will be associated with alterations in species composition. We selected four 200 × 200 km areas in Wisconsin, Maine, Arkansas, and the Ohio-West Virginia area, representing focal areas of potential species range shifts. PnET-Ⅱ model simulations were carried out assuming that all forests achieved steady state, of which the species compositions were predicted by DISTRIB model with no migration limitation. The total NPP under the current climate ranged from 552 to 908 g C/m^2 per year. The effects of potential species redistributions on NPP were moderate （-12% to ＋8%） compared with the influence of future climatic changes （-60% to ＋25%）. The direction and magnitude of climate change effects on NPP were largely dependent on the degree of warming and water balance. Thus, the magnitude of future climate change can affect the feedback system between the atmosphere and biosphere.展开更多
Patterns of body size variation along geographical gradients have long been searched for and generalized into eco-geographical rules.However,no rodent species has yet been analyzed in relation to the 3 dimensions of l...Patterns of body size variation along geographical gradients have long been searched for and generalized into eco-geographical rules.However,no rodent species has yet been analyzed in relation to the 3 dimensions of latitude,longitude and altitude.We analyzed geographical clines and dimorphism of body and skull size in the herb field mouse(Apodemus uralensis)across the species range,based on field data and on data from the literature.Sexual dimorphism in adult A.uralensis was not expressed at a large scale,while local patterns were inconsistent.Age-dependent size changes were most expressed in adult individuals:most characters of adults exceeded in size those of subadults,while subadult-juvenile size differences were only significant in body weight and length,zygomatic skull width,length of cranial diastema and breadth of braincase.Despite central morphological niches along the clines being separated,A.uralensis populations showed a high degree of size overlap in morphological space.We found the species to be characterized by high size variability,with the largest individuals inhabiting the eastern and southern edges of the distribution range.Tail,hind foot and ear lengths were largest in the southern part of the range,in agreement with Allen’s rule.The main measurements that we analyzed,namely body mass,zygomatic skull width and condylobasal skull length,show the presence of 3 clines in the size of adult A.uralensis:(i)a decreasing south-north cline,opposing Bergmann’s rule;(ii)an increasing west-east cline,in accordance with Murphy’s rule;and(iii)an increasing altitudinal cline.展开更多
基金Supported by the DISTRIB/SHIFT grant from the USDA Forest Service Northern Research Station.
文摘Forests are dynamic in both structure and species composition, and these dynamics are strongly influenced by climate. However, the net effects of future tree species composition on net primary production （NPP） are not well understood. The objective of this work was to model the potential range shifts of tree species （DISTRIB Model） and predict their impacts on NPP （PnET-Ⅱ Model） that will be associated with alterations in species composition. We selected four 200 × 200 km areas in Wisconsin, Maine, Arkansas, and the Ohio-West Virginia area, representing focal areas of potential species range shifts. PnET-Ⅱ model simulations were carried out assuming that all forests achieved steady state, of which the species compositions were predicted by DISTRIB model with no migration limitation. The total NPP under the current climate ranged from 552 to 908 g C/m^2 per year. The effects of potential species redistributions on NPP were moderate （-12% to ＋8%） compared with the influence of future climatic changes （-60% to ＋25%）. The direction and magnitude of climate change effects on NPP were largely dependent on the degree of warming and water balance. Thus, the magnitude of future climate change can affect the feedback system between the atmosphere and biosphere.
文摘Patterns of body size variation along geographical gradients have long been searched for and generalized into eco-geographical rules.However,no rodent species has yet been analyzed in relation to the 3 dimensions of latitude,longitude and altitude.We analyzed geographical clines and dimorphism of body and skull size in the herb field mouse(Apodemus uralensis)across the species range,based on field data and on data from the literature.Sexual dimorphism in adult A.uralensis was not expressed at a large scale,while local patterns were inconsistent.Age-dependent size changes were most expressed in adult individuals:most characters of adults exceeded in size those of subadults,while subadult-juvenile size differences were only significant in body weight and length,zygomatic skull width,length of cranial diastema and breadth of braincase.Despite central morphological niches along the clines being separated,A.uralensis populations showed a high degree of size overlap in morphological space.We found the species to be characterized by high size variability,with the largest individuals inhabiting the eastern and southern edges of the distribution range.Tail,hind foot and ear lengths were largest in the southern part of the range,in agreement with Allen’s rule.The main measurements that we analyzed,namely body mass,zygomatic skull width and condylobasal skull length,show the presence of 3 clines in the size of adult A.uralensis:(i)a decreasing south-north cline,opposing Bergmann’s rule;(ii)an increasing west-east cline,in accordance with Murphy’s rule;and(iii)an increasing altitudinal cline.
