祁连山北坡天然草地不同尺度地上生物量空间格局对地形的响应

Responses of spatial pattern of aboveground biomass of natural grassland to terrain at different scales in northern slope of Qilian Mountains

草地群落地上生物量的空间格局反映了地形差异导致的群落资源配置空间异质性。采用草地群落调查与广义相加模型(GAM)相结合的方法,分析了祁连山北坡典型草原山体尺度和坡面尺度上群落地上生物量格局的响应特征。结果表明:山体尺度上,群落地上生物量受地形因子影响的顺序为海拔>坡向变率≈坡度变率≈坡度;利用坡向作为划分条件将山体尺度缩小为坡面尺度后,东、西两个坡面群落地上生物量受坡向变率的影响最大,南、北坡则分别受海拔和坡度变率的影响最大,其中草地群落地上生物量在东坡随坡向变率的增大先减少后增加,西坡随坡向变率的增大先增加后减少,南坡随海拔的上升而增加,北坡随坡度变率的增大先不变后减少;草地群落地上生物量空间格局在山体尺度和坡面尺度上具有明显的尺度依赖特征。

Spatial pattern of aboveground biomass of grassland community reflects spatial heterogeneity of resource allocation caused by terrain difference. Community survey method and generalized additive model （GAM） were used to study the response characteristics of community’s aboveground biomass spatial pattern at hill and hillslope scales in natural grassland of the northern slope of Qilian Mountains. The results showed that at the hill scale, terrain factors had definite effects on the aboveground biomass of community, with the sequence of elevation 〉 slope of aspect （SOA） ≈ slope of slope （SOS） ≈ slope. When reducing hill scale to hillslope scale by aspect, the aboveground biomass of grassland community would be most affected by SOA in east and west aspects, and by elevation and SOS in south and north aspects. On east slope, community’s aboveground biomass firstly decreased then increased in SOA gradient, and vice versa in west slope. On south slope, it increased with elevation. On north slope, it firstly kept stable then decreased in SOS gradient. Our study suggested that the spatial pattern of aboveground biomass of grassland community was obviously scaledependent at hill and hillslope scales.