黄土高原农牧交错带退耕坡地苜蓿－铁杆蒿群落养分分布特征

摘要

植物群落养分的空间分布反映了生态系统物质循环特征，可以为揭示生态系统资源的有效性及生态系统中植物群落的演替过程提供依据。本研究以黄土高原农牧交错带退耕坡地苜蓿－铁杆蒿群落为对象，分析其生物量和养分含量的空间分布特征。结果表明：退耕地苜蓿－铁杆蒿群落坡上部以苜蓿为主导物种，坡下部以铁杆蒿为主导物种，坡中部由二者共同主导。同一植物的生物量和N含量具有相似的空间结构，并且与植物种类有关；苜蓿和铁杆蒿P含量均以球状模型最佳，K含量的空间分布均以高斯模型最佳。苜蓿－铁杆蒿群落生物量和养分含量具有较强的空间依赖性，其空间变异主要由结构性因素决定。苜蓿和铁杆蒿生物量和养分含量的自相关性随距离变化表现出相似的趋势，但随生物量和养分种类的不同而异，且铁杆蒿生物量和养分含量的自相关性大于苜蓿。随着人工草地向天然草地的演替，群落生物量和养分含量的空间自相关性和空间依赖性逐渐增强。%The distribution of nutrients in plant community could reflect the cycling of nutrients in ecosystems ,and thus provide evidence for the availability of soil resources for the ecosystems as well as for the understanding of the evolu-tion of plant community in the ecosystems .In this study ,we analyzed the spatial distribution of biomass and nutrients in Medicago sativa-Artemisia sacrorum Ledeb community along an abandoned slope in the cropping-pastoral ecotone of the Loess Plateau .The objectives were to understand how nutrients were distributed along abandoned grass slope and to es-tablish the relationships between nutrients distribution and community succession .The results showed that the grass com-munities were dominated by Medicago sativa in the upper slope ,by Artemisia sacrorum Ledeb in the lower slope ,and by both of them in the middle slope .Plant biomass and N content had similar spatial distribution patterns ,which varied a-mong plant species .The best fit models of the spatial distribution for both Medicago sativa and Artemisia sacrorum Ledeb were spherical model for P content ,and Gaussian model for K content ,respectively .The biomass and nutrients contents in the Medicago sativa - Artemisia sacrorum Ledeb community has a relatively strong spatial dependence .The spatial variability of them was mainly due to the constructional factors .The spatial auto correlations of each variable showed sim-ilar trend with distance but varied with variables .Additionally ,the spatial auto-correlation of Artemisia sacrorum Ledeb was greater than that of Medicago sativa .The results from this study suggested that the spatial auto correlation and de-pendence of grass biomass and nutrients contents became increased with the succession of artificial grass community to natural community .