黄土高原不同演替阶段草地植被细根垂直分布特征与土壤环境的关系

研究了黄土区不同演替阶段草地植被细根垂直分布特征与土壤环境的关系,结果表明不同演替阶段草地植被细根生物量、根长密度、表面积、直径和比根长均具有明显的垂直分布特征。细根生物量、根长密度和细根表面积一般随土层加深而逐渐减少,且集中分布于0~40cm土层;随着演替的进行,除20a弃耕地外,0~80 cm土层细根生物量、根长密度和细根表面积逐渐增加;除25a弃耕地外,细根直径随演替进行逐渐减小。0~100 cm土层土壤含水量随演替进行而增加,不同演替阶段深层土壤水分较表层稳定。土壤容重的变化趋势为9<4<15<20<25a弃耕地,根系对表层土壤水分和容重的影响较大,而对深层土壤水分与容重影响较少。不同演替阶段细根各参数和土壤水分、容重差异均达到显著水平。各弃耕地细根参数之间,细根参数和土壤环境因子之间存在不同程度的相关关系,土壤含水量在草本植被的不同演替阶段均是影响其细根垂直分布的关键因素。土壤容重在演替早期对草本植被根系的影响较小,随着演替进行其影响作用进一步增强。

A ground hydrologic model with inclusion of a layer of vegetation canopy that can interact with general-circulation model

In this paper, a ground hydrologic model(GHM) is presented in which the vapor, heat and momentum exchanges between ground surface covers (including vegetation canopy) and atmosphere is described more realistically. The model is used to simulate three sets of field data and results from the numerical simulation agree with the field data well. GHM has been tested using input data generated by general circulation model (GCM) runs for both the North American regions and the Chinese regions, The results from GHM are quite different from those of GHMs in GCMs. It shows that a more active concerted effort on the land surface process study to provide a physically realistic GHM for predicting the exchange between land and atmosphere is important and necessary.