人工与自然恢复方式对流动沙地土壤与植被特征的影响

目的]分析不同固沙措施对土壤—植被系统恢复的生态效应,为该地区沙化草地选取合理的固沙措施、草场管理与利用以及沙漠化治理提供依据。方法]以宁夏地区盐池沙地围封自然恢复草地和灌丛人工固沙林地为研究对象,以周围流动沙地为对照,对不同处理措施样地土壤性质和地表植被特征进行调查。结果](1)两种恢复措施均能够显著增加土壤黏粉粒含量、土壤有机碳和全氮含量(p0.001),降低土壤温度、容重和含水量(p0.05),并显著提高草本植物丰富度、个体数和平均高度(p0.05)。(2)自然围封草地土壤黏粉粒含量、草本植物个体数和丰度分别是人工灌丛林地的2.1,2.8,1.4倍;而其土壤含水量下降幅度是人工灌丛固沙林地的1.7倍。人工灌丛固沙林地土壤有机碳、全氮含量以及草本植物平均高度分别是自然恢复草地的2.1,2.0,2.2倍;而其土壤容重下降幅度是自然恢复草地的2.5倍。(3)随着流动沙地固定和草本植被恢复,植物群落以一年生草本植物为特征逐渐演替到以一年生草本植物为主且伴生有多年生植物的草地生态系统。但一年生和多年生植物个体数和物种数自然恢复草地均明显高于人工灌丛固沙林地。结论]围封自然恢复对于宁夏地区盐池沙地土壤质地与植被系统稳定性的恢复质量优于灌丛人工恢复措施,人工灌丛固沙因其能够有效改良土壤营养条件亦可作为重要辅助恢复手段。

Effects of Artificial Revegetation and Natural Restoration on Soil and Vegetation Properties in Desert Land

Objective] Ecological effects of different measures of revegetation and sand fixation on soil-vegetation system were evaluated to provide some theoretical bases for sand fixation and desertification control, grassland management and utilization.Methods] In desert land of Yanchi County in Ningxia Hui Autonomous Region, a naturally restored grassland and a manually afforested shrub land were selected as sampling sites, the adjacent shifting sand land was taken as control for comparison. Soil properties and vegetation characteristics were sampled and measured.Results] (1) In addition to herbaceous plant richness, density and height(p<0.05), soil clay plus silt content, soil organic carbon and total nitrogen content(p<0.001) were markedly increased by the both measures. Whereas soil temperature, bulk density and soil moisture decreased(p<0.05).(2) Soil clay plus silt content, herbaceous richness and density in naturally restored grassland were 2.1, 2.8, 1.4 times greater than those of manually afforested shrub land, respectively. The decreasing rate of soil moisture in naturally restored grassland was 1.7 times more than that of manually afforested shrub land. Soil organic carbon and total nitrogen content, and herbaceous height in manually afforested shrub land were 2.1, 2.0 and 2.2 times greater than those in naturally restored grassland, respectively. The decreasing magnitude of soil bulk density in manually afforested shrub land was 2.5 times more than that in naturally restored grassland.(3) Along with the succession and stabilization of shifting sand land, some annual herbaceous plants were gradually replaced by perennial plants. Herbaceous individual numbers and species richness of both annual and perennial plants were remarkably high in naturally restored grassland in comparison with the corresponding values of manually afforested shrub land.Conclusion] Naturally restored management overmatched manually afforested management on the stability recovery of vegetation-soil system. The manually afforested management could be considered as an important supplementary way with efficient fertility improvement in desert ecosystems of Yanchi County in Ningxia Hui Autonomous Region.