Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO_2 levels. The conversion of tropical forests to ru...Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO_2 levels. The conversion of tropical forests to rubber plantations in SE Asia is increasingly common, and there is a need to understand the impacts of this land-use change on soil respiration in order to revise CO_2 budget calculations. This study focused on the spatial variability of soil respiration along a slope in a natural tropical rainforest and a terraced rubber plantation in Xishuangbanna, Southwest(SW) China. In each land-use type, we inserted 105 collars for soil respiration measurements.Research was conducted over one year in Xishuangbanna during May, June, July and October 2015(wet season) and January and March 2016(dry season). The mean annual soil respiration rate was 30% higher in natural forest than in rubber plantation and mean fluxes in the wet and dry season were 15.1 and 9.5 Mg C ha^(-1) yr^(-1) in natural forest and 11.7 and 5.7 Mg C ha^(-1) yr^(-1) in rubber plantation. Using a linear mixedeffects model to assess the effect of changes in soil temperature and moisture on soil respiration, we found that soil temperature was the main driver of variation in soil respiration, explaining 48% of its seasonal variation in rubber plantation and 30% in natural forest. After including soil moisture, the model explained 70% of the variation in soil respiration in natural forest and 76% in rubber plantation. In the natural forest slope position had a significant effect on soil respiration, and soil temperature and soil moisture gradients only partly explained this correlation. In contrast, soil respiration in rubber plantation was not affected by slope position, which may be due to the terrace structure that resulted in more homogeneous environmental conditions along the slope. Further research is needed to determine whether or not these findings hold true at a landscape level.展开更多
The analysis of the consequences of land use （in particular forest use） may be considered as a partial step towards an integrated modeling of a land system. In the paper a forest territory is considered, where a gap...The analysis of the consequences of land use （in particular forest use） may be considered as a partial step towards an integrated modeling of a land system. In the paper a forest territory is considered, where a gapcut is made, and after a given time period the eventual change in the spatial distribution of undergrowth plants and tree seedlingsis to be detected. Floristic data are collected along a line transect. A method for the detection of the change in the plant distributions along the transect is proposed to see whether this occurs at the geometric frontier of the human intervention. Since in the considered case the distribution of the changepoint estimate is not known, as a substitute of its confidence interval, the socalled changeinterval is calcu lated, using an adaptation of the bootstrap method. As an illustration, for a concrete plant species, the maximum likelihood estimation of the changepoint and the calcu lation of the above mentioned changeinterval is presented. Finally, the validation of the proposed method against some typical ecological situations is also presented, which provides a justification of the used algorithms.展开更多
基金the BMZ/GIZ “Green Rubber” (Project No. Project No. 13.1432.7-001.00)the CGIAR (Consultative Group for International Agricultural Research) Research Program 6: Forests, Trees and Agroforestry+2 种基金financially supported by the Federal Ministry for Economic Cooperation and Development, Germanyfunded by the National Natural Science Foundation of China (Grant No. 31450110067) the Chinese Academy of Science funded the Chinese Academy of Science funded the post-doc fellowship for Stefanie Goldberg (Grant No. 2013Y2SB0007)
文摘Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO_2 levels. The conversion of tropical forests to rubber plantations in SE Asia is increasingly common, and there is a need to understand the impacts of this land-use change on soil respiration in order to revise CO_2 budget calculations. This study focused on the spatial variability of soil respiration along a slope in a natural tropical rainforest and a terraced rubber plantation in Xishuangbanna, Southwest(SW) China. In each land-use type, we inserted 105 collars for soil respiration measurements.Research was conducted over one year in Xishuangbanna during May, June, July and October 2015(wet season) and January and March 2016(dry season). The mean annual soil respiration rate was 30% higher in natural forest than in rubber plantation and mean fluxes in the wet and dry season were 15.1 and 9.5 Mg C ha^(-1) yr^(-1) in natural forest and 11.7 and 5.7 Mg C ha^(-1) yr^(-1) in rubber plantation. Using a linear mixedeffects model to assess the effect of changes in soil temperature and moisture on soil respiration, we found that soil temperature was the main driver of variation in soil respiration, explaining 48% of its seasonal variation in rubber plantation and 30% in natural forest. After including soil moisture, the model explained 70% of the variation in soil respiration in natural forest and 76% in rubber plantation. In the natural forest slope position had a significant effect on soil respiration, and soil temperature and soil moisture gradients only partly explained this correlation. In contrast, soil respiration in rubber plantation was not affected by slope position, which may be due to the terrace structure that resulted in more homogeneous environmental conditions along the slope. Further research is needed to determine whether or not these findings hold true at a landscape level.
文摘The analysis of the consequences of land use （in particular forest use） may be considered as a partial step towards an integrated modeling of a land system. In the paper a forest territory is considered, where a gapcut is made, and after a given time period the eventual change in the spatial distribution of undergrowth plants and tree seedlingsis to be detected. Floristic data are collected along a line transect. A method for the detection of the change in the plant distributions along the transect is proposed to see whether this occurs at the geometric frontier of the human intervention. Since in the considered case the distribution of the changepoint estimate is not known, as a substitute of its confidence interval, the socalled changeinterval is calcu lated, using an adaptation of the bootstrap method. As an illustration, for a concrete plant species, the maximum likelihood estimation of the changepoint and the calcu lation of the above mentioned changeinterval is presented. Finally, the validation of the proposed method against some typical ecological situations is also presented, which provides a justification of the used algorithms.
