民勤绿洲边缘沙丘生物土壤结皮发育对浅层土壤质地、养分含量及微生物数量的影响

摘要

为探明干旱沙区沙丘生物土壤结皮形成及发育对浅层土壤质地、养分含量及微生物数量的影响,以民勤绿洲边缘结皮前期阶段(NCS)、物理-藻类结皮阶段(PACS)、藻类-地衣结皮阶段(ALCS)以及地衣-藓类结皮阶段(LMCS)的0-1 cm层土壤为研究对象,研究了土壤颗粒组成、土壤有机质、全氮、速效磷、速效钾含量以及土壤微生物数量动态变化.结果表明:1)生物土壤结皮在NCS向ALCS的发育过程中,其有效地提高了0-1 cm层土壤细沙粒(0-200 μm)含量,同时降低了粗砂粒(200-2000 μm)含量;在ALCS向LMCS演替过程中,土壤粒度组成无明显变化.2)土壤结皮形成与发育对0-1 cm层土壤有机质、全氮、速效磷以及速效钾含量均有显著影响(P＜0.05),4种养分含量均随生物结皮演替逐渐增大.3)在土壤结皮形成与演替过程中,0-1 cm层土壤细菌、放线菌以及真菌数量均呈现出先增大后减小趋势(峰值均出现在PACS),土壤总藻生物量一直处于持续增大趋势;在5-12月期间,土壤微生物数量或生物量变化均呈现出先增大后减小趋势.4)土壤结皮在NCS向PACS演替过程中,土壤颗粒组成的改变是土壤微生物量及养分变化的主要驱动因子;PACS向LMCS演替过程,土壤藻类、地衣、藓类是提高土壤养分含量的主要因子.表明民勤绿洲边缘沙丘生物土壤结皮形成与发育能有效地改善浅层土壤质量,提高土壤肥力,同时对土壤生态系统改善及生态环境保护具有重要作用.%The Minqin Oasis is located in the northwest Hexi Corridor,and the northern,western,and eastern edges are surrounded by the Tengger and Badain Jaran Deserts.To manage sand and prevent sandstorms,large tracts of Haloxylon ammodendron plantations have previously been planted on fixed and semi-fixed sand dunes of the Minqin Oasis fringe.At present,many biological soil crusts have formed and are developing in the fixed woodland.To ascertain whether the formation and development of dune biological soil crust affects soil texture,nutrient contents,and microorganism populations,the woodland of H.ammodendron plantations were divided into a no crust stage (NCS),physical-algal crust stage (PACS),algal-lichen crust stage (ALCS),and lichen-moss crust stage (LMCS) according to crust coverage,crust thickness,and underlying and ground covers.Here,the contents of soil clay,silt,fine sand,and coarse sand particles,organic matter,total nitrogen,available phosphorus and potassium,and the populations or biomass of bacteria,fungi,and actinomycetes in the 0-1 cm soil layer were measured and studied.The results showed that 1) the formation and development of biological soil crusts from NCS to ALCS not only considerably increased the content of fine soil particles (0-200 μm) but also decreased soil coarse particle (200-2000 μm) contents.However,there was no significant change in soil particle composition during the succession from ALCS to LMCS;2) the succession of biological soil crusts obviously influenced the contents of soil organic matter,total nitrogen,available phosphorus and potassium,and their contents gradually increased with succession;3) during biological soil crust succession,all quantities of soil bacteria,fungi,and actinomycetes showed a trend of initially increasing and then decreasing,peaking in PACS.Simultaneously,the soil total algal biomass continuously increased.Furthermore,microbial quantities or biomass also presented a trend of initially increasing and then decreasing from May to December;and 4) in succession from NCS to PACS,the change of soil particle composition was one of the main factors causing variations in soil organic matter,total nitrogen,available phosphorus and potassium,bacteria,fungi,and actinomycetes.During succession from PACS to LMCS,soil algae,lichen,and mosses were the main factors improving soil organic matter,total nitrogen,and available phosphorus and potassium contents.It was suggested that the formation and development of the biological soil crust distributed in the surface layer soil of Minqin Oasis fringe dunes not only ameliorated shallow soil quality effectively,but also played a considerable role in improving soil ecosystems and protecting the ecological environment.