灌丛对流动沙地土壤特性和草本植物的影响

Multiple Effects of Shrub on Soil Properties and Understory Vegetation in Horqin Sand Land,Inner Mongolia

通过对流动沙地灌丛内外土壤特性、土壤养分含量、土壤种子库和草本植物群落特征的差异性调查,分析了灌丛对沙地土壤特性和林下草本植被的影响。结果表明,在流动沙地0—20 cm土壤中细沙、极细沙、粘粉粒、有机质、总氮和总磷、有效磷和土壤水分含量,小叶锦鸡儿灌丛下分别较灌丛外高17.3%、4.4%、49.5%、43.8%、40.0%、23.1%、16.3%和10.8%,黄柳灌丛下较灌丛外分别高3.5%、21.3%、0.0%、20.0%、16.7%、8.3%、10.6%和28.1%。小叶锦鸡儿、差不嘎蒿和黄柳灌丛下凋落物蓄积量要比灌丛外分别高18.3倍、365.2倍和15.5倍。差不嘎蒿灌丛下土壤种子库密度较灌丛外高10.9倍。原为半固定、半流动沙地优势种的多年生草本植物白草,不仅能在流动沙地灌丛下存活,而且具有较高的密度、高度、盖度和地上生物量。结果还表明,从灌丛中心到灌丛边缘,凋落物产量、土壤种子库密度、草本植物密度、盖度、生物量均存在明显的递减梯度,在灌丛外不远处消失。这些结果说明,在流动沙地,灌丛具有明显的“肥岛”效应和“保种”作用。

To understand status and roles of shrub in vegetation degradation and recovery processes in semiarid areas, China, we investigated effects of shrub canopy on soil properties, organic litter, seed bank and understory herbage community properties in Horqin sand land, Mongolia. The results showed that in shifting sand dunes, very find sand, silt, clay, organic matter, total N and P, available P and soil moisture in 0--20 cm depth were 17.3 %, 4.4 %, 49.5 %, 43.8 %, 40. 0 %, 23.1%, 16.3 % and 10.8 % higher for Caragana microphylla,and 3.5%, 21.3%, 0.0%, 20.0%, 16.7%, 8.3%, 10.6% and 28. 1% higher for Salix gordejevii, respectively under canopy of remnant shrub species than those in open space; average organic litter output was 18.3 times for C. microphylla, 365.2 times for Artemisia halodendron and 15.5 times for S. gordejevii, respectively, under shrub canopy compared to open space; soil seed density was 10.9 times higher under A. hatodendron canopy than that in open space; perennial herbage Pennisetum centrasiaticum be- longed originally to fixed sand dune not only could survived under shrub canopy in shift sand dunes, but also had higher plant densities, height, coverage and above ground biomass. There were a significant gradient of organic litter mass, soil seed bank density and plant density under shrub canopy, decreasing gradually from the centre of shrub canopy to the edge of the canopy, and disappeared entirely in open space of one to two meter distant from the shrub canopy. These results suggested that shrub had significant ＂fertile island＂ effects and important ＂keep species＂ roles in shifting sand dunes.