Soil microbial biomass is an active fraction of soil organic matter. It shows quicker response than soil organic matter to any change in the soil environment. Being an index of soil fertility, it plays a key role in t...Soil microbial biomass is an active fraction of soil organic matter. It shows quicker response than soil organic matter to any change in the soil environment. Being an index of soil fertility, it plays a key role in the decomposition of litters and fast release of available nutrients. Leaf litters of leguminous and non-leguminous species in alone and mixed form were applied as treatments in the soil to observe the changes in the magnitude of soil microbial biomass. Soil microbial biomass C and N were determined by chloroform fumigation extraction method. Increment in the concentration of microbial biomass C and N was higher in the treatments with leguminous leaf litter (497 - 571 μgCg?1, 48 - 55 μgNg?1) than the non-leguminous one (256 - 414 μgCg?1;22 - 36 μgNg?1). However, when non-leguminous litters were mixed with leguminous litters then the values increased distinctly (350 - 465 μgCg?1, 28 - 48 μgNg?1). On the basis of increment in soil microbial biomass, leaf litters of the species considered potential to improve soil nutrients are—Cassia siamea and Dalbergia sissoo from leguminous trees, Anthocephalus + Cassia and Shorea + Dalbergia from mixed form of non-leguminous and leguminous one and Eichhornia crassipes, an alien aquatic macrophyte. The leaf litters of these species can be used as source of organic matter to improve the crop yield.展开更多
Background： Forest biomass is helpful to assess its productivity and carbon （C） sequestration capacity. Several disturbance activities in tropical forests have reduced the biomass and net primary production （NPP）...Background： Forest biomass is helpful to assess its productivity and carbon （C） sequestration capacity. Several disturbance activities in tropical forests have reduced the biomass and net primary production （NPP） leading to climate change. Therefore, an accurateestimation of forest biomass and C cycling in context of disturbances is required for implementing REDD （Reducing Emissions from Deforestation and Forest Degradation） policy. Methods： Biomass and NPP of trees and shrubs were estimated by using allometric equations while herbaceous biomass was estimated by harvest method. Fine root biomass was determined from soil monolith. The C stock in vegetation was calculated by multiplying C concentration to dry weight. Results： Total stand biomass （Mg.ha-1） in undisturbed forest stand （US） was 960.4 while in disturbed forest stand （DS） it was 449.1. The biomass （Mg.ha-1） of trees, shrubs and herbs in US was 948.0, 4.4 and 1.4, respectively, while in DS they were 438.4, 6.1 and 1.2, respectively. Total NPP （Mg.ha-l.yr-1） was 26.58 （equivalent to 12.26 Mg C.ha-1.yr-1） in US and 14.91 （6.88 Mg C.ha-1.yr-1） in DS. Total C input into soil through litter plus root turnover was 6.78 and 3.35 Mg.ha-1.yr-1 in US and DS, respectively. Conclusions： Several disturbance activities resulted in the significant loss in stand biomass （53 %）, NPP （44 %）, and C sequestration capacity of tropical forest vegetation is far greater than that returned to the soil n eastern Nepal. The net uptake of carbon by the by the turnover of fine root and litter. Therefore, both stands of present forest act as carbon accumulating systems. Moreover, disturbance reflects higher C emissions which can be reduced by better management.展开更多
文摘Soil microbial biomass is an active fraction of soil organic matter. It shows quicker response than soil organic matter to any change in the soil environment. Being an index of soil fertility, it plays a key role in the decomposition of litters and fast release of available nutrients. Leaf litters of leguminous and non-leguminous species in alone and mixed form were applied as treatments in the soil to observe the changes in the magnitude of soil microbial biomass. Soil microbial biomass C and N were determined by chloroform fumigation extraction method. Increment in the concentration of microbial biomass C and N was higher in the treatments with leguminous leaf litter (497 - 571 μgCg?1, 48 - 55 μgNg?1) than the non-leguminous one (256 - 414 μgCg?1;22 - 36 μgNg?1). However, when non-leguminous litters were mixed with leguminous litters then the values increased distinctly (350 - 465 μgCg?1, 28 - 48 μgNg?1). On the basis of increment in soil microbial biomass, leaf litters of the species considered potential to improve soil nutrients are—Cassia siamea and Dalbergia sissoo from leguminous trees, Anthocephalus + Cassia and Shorea + Dalbergia from mixed form of non-leguminous and leguminous one and Eichhornia crassipes, an alien aquatic macrophyte. The leaf litters of these species can be used as source of organic matter to improve the crop yield.
文摘Background： Forest biomass is helpful to assess its productivity and carbon （C） sequestration capacity. Several disturbance activities in tropical forests have reduced the biomass and net primary production （NPP） leading to climate change. Therefore, an accurateestimation of forest biomass and C cycling in context of disturbances is required for implementing REDD （Reducing Emissions from Deforestation and Forest Degradation） policy. Methods： Biomass and NPP of trees and shrubs were estimated by using allometric equations while herbaceous biomass was estimated by harvest method. Fine root biomass was determined from soil monolith. The C stock in vegetation was calculated by multiplying C concentration to dry weight. Results： Total stand biomass （Mg.ha-1） in undisturbed forest stand （US） was 960.4 while in disturbed forest stand （DS） it was 449.1. The biomass （Mg.ha-1） of trees, shrubs and herbs in US was 948.0, 4.4 and 1.4, respectively, while in DS they were 438.4, 6.1 and 1.2, respectively. Total NPP （Mg.ha-l.yr-1） was 26.58 （equivalent to 12.26 Mg C.ha-1.yr-1） in US and 14.91 （6.88 Mg C.ha-1.yr-1） in DS. Total C input into soil through litter plus root turnover was 6.78 and 3.35 Mg.ha-1.yr-1 in US and DS, respectively. Conclusions： Several disturbance activities resulted in the significant loss in stand biomass （53 %）, NPP （44 %）, and C sequestration capacity of tropical forest vegetation is far greater than that returned to the soil n eastern Nepal. The net uptake of carbon by the by the turnover of fine root and litter. Therefore, both stands of present forest act as carbon accumulating systems. Moreover, disturbance reflects higher C emissions which can be reduced by better management.
