Estimating the volume growth of forest ecosystems accurately is important for understanding carbon sequestration and achieving carbon neutrality goals.However,the key environmental factors affecting volume growth diff...Estimating the volume growth of forest ecosystems accurately is important for understanding carbon sequestration and achieving carbon neutrality goals.However,the key environmental factors affecting volume growth differ across various scales and plant functional types.This study was,therefore,conducted to estimate the volume growth of Larix and Quercus forests based on national-scale forestry inventory data in China and its influencing factors using random forest algorithms.The results showed that the model performances of volume growth in natural forests(R^(2)=0.65 for Larix and 0.66 for Quercus,respectively)were better than those in planted forests(R^(2)=0.44 for Larix and 0.40 for Quercus,respectively).In both natural and planted forests,the stand age showed a strong relative importance for volume growth(8.6%–66.2%),while the edaphic and climatic variables had a limited relative importance(<6.0%).The relationship between stand age and volume growth was unimodal in natural forests and linear increase in planted Quercus forests.And the specific locations(i.e.,altitude and aspect)of sampling plots exhibited high relative importance for volume growth in planted forests(4.1%–18.2%).Altitude positively affected volume growth in planted Larix forests but controlled volume growth negatively in planted Quercus forests.Similarly,the effects of other environmental factors on volume growth also differed in both stand origins(planted versus natural)and plant functional types(Larix versus Quercus).These results highlighted that the stand age was the most important predictor for volume growth and there were diverse effects of environmental factors on volume growth among stand origins and plant functional types.Our findings will provide a good framework for site-specific recommendations regarding the management practices necessary to maintain the volume growth in China's forest ecosystems.展开更多
In the context of traumatic stress, the dominant discourse has mainly focused on distress, thus undermining the role that eustress has in traumatic experiences. One of the few exceptions to this has been the research ...In the context of traumatic stress, the dominant discourse has mainly focused on distress, thus undermining the role that eustress has in traumatic experiences. One of the few exceptions to this has been the research on posttraumatic growth, which has generated much interest since its beginning. There is an increasing interest in posttraumatic growth in various cultures and hence an expansion of the measure, the Post Traumatic Growth Inventory (PTGI), into various languages. This article is the first to perform a rigorous investigation of the psychometric properties of the PTGI, including the scale and subscale reliability, inter-item and subscale correlations, and using a CFA approach. The properties are established with a French translation using two populations of caregivers: those bereaved by HIV/AIDS and parents who are caring for a child with a life-limiting illness. These properties were determined for both the original 21 item scale as well as the shortened version.展开更多
The economic growth in Sub-Sahara African （SSA） IDB member countries has been encouraging over the last decade; however, it is still not high enough to enable these countries to overcome the persistent poverty. Ther...The economic growth in Sub-Sahara African （SSA） IDB member countries has been encouraging over the last decade; however, it is still not high enough to enable these countries to overcome the persistent poverty. There is thus a need to raise substantially real GDP growth rates on a sustained basis, both through the productivity channel and factor accumulation such as labor and capital. This study focuses on ＂the source of economic growth in SSA IDB member countries＂ with the objective of identifying the main driving factors of economic growth in the region using the growth accounting framework and extending the existing analysis both by country and time coverage. The paper is expected to be useful for the policymakers in the region to have a clear picture on the main sources of growth, and thus help them in identifying strategic reform areas of intervention in line with the most binding factors of growth. The data used in this study cover 20 Sub-Sahara African countries covering the period 1990-2012. The data set includes real GDP, labor force, and capital stock. The source of data is the various version of the World Economic Outlook, IMF. Capital stock is estimated using perpetual inventory method and the base year is 1970. In estimating growth accounting model, a translog production function is applied using panel data and random effects model. Empirical results show that the capital accumulation is the most important individual factor in GDP growth （52%） followed by workforce accumulation （39%） while total factor productivity （TFP） accounts for meagre 8%. This suggests that, on average, real GDP growth in Sub-Sahara African countries was driven primarily by factor accumulation with a low level of TFP. In addition, the elasticity of labor was lower than that of capital indicating that the labor played very little role in GDP growth most likely due to unskilled labor force or mismatch of labor skills with the production process. Furthermore, this also adversely affects both the TFP growth and the share of capital growth to the GDP growth. The results indicate that the critical constraint to the economic growth appears to be poor labor skills that lead to both low labor productivity and under-utilization of capital stock.展开更多
The inflection point is an important feature of sigmoidal height-diameter(H-D)models.It is often cited as one of the properties favoring sigmoidal model forms.However,there are very few studies analyzing the inflectio...The inflection point is an important feature of sigmoidal height-diameter(H-D)models.It is often cited as one of the properties favoring sigmoidal model forms.However,there are very few studies analyzing the inflection points of H-D models.The goals of this study were to theoretically and empirically examine the behaviors of inflection points of six common H-D models with a regional dataset.The six models were the Wykoff(WYK),Schumacher(SCH),Curtis(CUR),HossfeldⅣ(HOS),von Bertalanffy-Richards(VBR),and Gompertz(GPZ)models.The models were first fitted in their base forms with tree species as random effects and were then expanded to include functional traits and spatial distribution.The distributions of the estimated inflection points were similar between the two-parameter models WYK,SCH,and CUR,but were different between the threeparameter models HOS,VBR,and GPZ.GPZ produced some of the largest inflection points.HOS and VBR produced concave H-D curves without inflection points for 12.7%and 39.7%of the tree species.Evergreen species or decreasing shade tolerance resulted in larger inflection points.The trends in the estimated inflection points of HOS and VBR were entirely opposite across the landscape.Furthermore,HOS could produce concave H-D curves for portions of the landscape.Based on the studied behaviors,the choice between two-parameter models may not matter.We recommend comparing seve ral three-parameter model forms for consistency in estimated inflection points before deciding on one.Believing sigmoidal models to have inflection points does not necessarily mean that they will produce fitted curves with one.Our study highlights the need to integrate analysis of inflection points into modeling H-D relationships.展开更多
基金supported by the Major Program of the National Natural Science Foundation of China(No.32192434)the Fundamental Research Funds of Chinese Academy of Forestry(No.CAFYBB2019ZD001)the National Key Research and Development Program of China(2016YFD060020602).
文摘Estimating the volume growth of forest ecosystems accurately is important for understanding carbon sequestration and achieving carbon neutrality goals.However,the key environmental factors affecting volume growth differ across various scales and plant functional types.This study was,therefore,conducted to estimate the volume growth of Larix and Quercus forests based on national-scale forestry inventory data in China and its influencing factors using random forest algorithms.The results showed that the model performances of volume growth in natural forests(R^(2)=0.65 for Larix and 0.66 for Quercus,respectively)were better than those in planted forests(R^(2)=0.44 for Larix and 0.40 for Quercus,respectively).In both natural and planted forests,the stand age showed a strong relative importance for volume growth(8.6%–66.2%),while the edaphic and climatic variables had a limited relative importance(<6.0%).The relationship between stand age and volume growth was unimodal in natural forests and linear increase in planted Quercus forests.And the specific locations(i.e.,altitude and aspect)of sampling plots exhibited high relative importance for volume growth in planted forests(4.1%–18.2%).Altitude positively affected volume growth in planted Larix forests but controlled volume growth negatively in planted Quercus forests.Similarly,the effects of other environmental factors on volume growth also differed in both stand origins(planted versus natural)and plant functional types(Larix versus Quercus).These results highlighted that the stand age was the most important predictor for volume growth and there were diverse effects of environmental factors on volume growth among stand origins and plant functional types.Our findings will provide a good framework for site-specific recommendations regarding the management practices necessary to maintain the volume growth in China's forest ecosystems.
文摘In the context of traumatic stress, the dominant discourse has mainly focused on distress, thus undermining the role that eustress has in traumatic experiences. One of the few exceptions to this has been the research on posttraumatic growth, which has generated much interest since its beginning. There is an increasing interest in posttraumatic growth in various cultures and hence an expansion of the measure, the Post Traumatic Growth Inventory (PTGI), into various languages. This article is the first to perform a rigorous investigation of the psychometric properties of the PTGI, including the scale and subscale reliability, inter-item and subscale correlations, and using a CFA approach. The properties are established with a French translation using two populations of caregivers: those bereaved by HIV/AIDS and parents who are caring for a child with a life-limiting illness. These properties were determined for both the original 21 item scale as well as the shortened version.
文摘The economic growth in Sub-Sahara African （SSA） IDB member countries has been encouraging over the last decade; however, it is still not high enough to enable these countries to overcome the persistent poverty. There is thus a need to raise substantially real GDP growth rates on a sustained basis, both through the productivity channel and factor accumulation such as labor and capital. This study focuses on ＂the source of economic growth in SSA IDB member countries＂ with the objective of identifying the main driving factors of economic growth in the region using the growth accounting framework and extending the existing analysis both by country and time coverage. The paper is expected to be useful for the policymakers in the region to have a clear picture on the main sources of growth, and thus help them in identifying strategic reform areas of intervention in line with the most binding factors of growth. The data used in this study cover 20 Sub-Sahara African countries covering the period 1990-2012. The data set includes real GDP, labor force, and capital stock. The source of data is the various version of the World Economic Outlook, IMF. Capital stock is estimated using perpetual inventory method and the base year is 1970. In estimating growth accounting model, a translog production function is applied using panel data and random effects model. Empirical results show that the capital accumulation is the most important individual factor in GDP growth （52%） followed by workforce accumulation （39%） while total factor productivity （TFP） accounts for meagre 8%. This suggests that, on average, real GDP growth in Sub-Sahara African countries was driven primarily by factor accumulation with a low level of TFP. In addition, the elasticity of labor was lower than that of capital indicating that the labor played very little role in GDP growth most likely due to unskilled labor force or mismatch of labor skills with the production process. Furthermore, this also adversely affects both the TFP growth and the share of capital growth to the GDP growth. The results indicate that the critical constraint to the economic growth appears to be poor labor skills that lead to both low labor productivity and under-utilization of capital stock.
文摘The inflection point is an important feature of sigmoidal height-diameter(H-D)models.It is often cited as one of the properties favoring sigmoidal model forms.However,there are very few studies analyzing the inflection points of H-D models.The goals of this study were to theoretically and empirically examine the behaviors of inflection points of six common H-D models with a regional dataset.The six models were the Wykoff(WYK),Schumacher(SCH),Curtis(CUR),HossfeldⅣ(HOS),von Bertalanffy-Richards(VBR),and Gompertz(GPZ)models.The models were first fitted in their base forms with tree species as random effects and were then expanded to include functional traits and spatial distribution.The distributions of the estimated inflection points were similar between the two-parameter models WYK,SCH,and CUR,but were different between the threeparameter models HOS,VBR,and GPZ.GPZ produced some of the largest inflection points.HOS and VBR produced concave H-D curves without inflection points for 12.7%and 39.7%of the tree species.Evergreen species or decreasing shade tolerance resulted in larger inflection points.The trends in the estimated inflection points of HOS and VBR were entirely opposite across the landscape.Furthermore,HOS could produce concave H-D curves for portions of the landscape.Based on the studied behaviors,the choice between two-parameter models may not matter.We recommend comparing seve ral three-parameter model forms for consistency in estimated inflection points before deciding on one.Believing sigmoidal models to have inflection points does not necessarily mean that they will produce fitted curves with one.Our study highlights the need to integrate analysis of inflection points into modeling H-D relationships.
