沙区生物土壤结皮演替对表层土壤养分和微生物群落组成的影响

Effects of biological soil crust succession on soil nutrients,microbial community composition in desert regions

生物土壤结皮是旱地生态系统的重要组成部分,在土壤表面生物和非生物因子的相互作用中发挥着重要作用。研究了腾格里沙漠南缘不同类型生物土壤结皮及其下0~2 cm和2~5 cm层土壤理化性质、微生物群落组成和酶活性,分析了土壤微生物群落组成和酶活性随结皮演替的变化特征及其与土壤理化性质的关系。结果表明:(1)随着结皮向着以藓类为优势的群落演替,结皮层及下层土壤有机碳、全氮、全磷、电导率(EC)及黏粉粒含量均呈显著增大趋势,但随着土层深度的增加而显著减小;pH、容重及砂粒含量则呈相反趋势。(2)结皮层总PLFAs、细菌和真菌PLFAs均表现为藓结皮>地衣结皮>藻结皮,藓结皮与藻结皮相比分别增加了24%、15%和39%;与藻结皮相比,藓结皮真菌和细菌PLFAs的比值(F:B)增加了20%。结皮下0~2 cm和2~5 cm土层微生物群落组成表现出相似的规律,但各参数均随土层深度的增加而显著减小。(3)结皮层及其下0~2 cm和2~5 cm层土壤蔗糖酶、过氧化氢酶、纤维素酶、淀粉酶、多酚氧化酶、过氧化物酶、脲酶和碱性磷酸酶活性均随结皮演替而显著升高,但其活性均随土层深度的增加而显著减小。(4)土壤微生物群落组成和酶活性与土壤有机碳、全氮、全磷、EC和黏粉粒含量呈显著正相关,而与pH、容重及砂粒含量呈显著负相关。结构方程模型分析表明结皮演替引发的土壤化学属性的变化是微生物群落和酶活性的关键驱动因子。

Biological soil crusts(BSCs),a critical component of dryland ecosystems,mediate interactions between biotic and abiotic factors on the soil surface.This study examines the soil physicochemical properties,microbial community composition,and enzyme activities of different types of BSCs—algae-dominated(AC),lichen-dominated(LC),and moss-dominated(MC)—along with the underlying soil layers(0-2 cm and 2-5 cm)at the southern edge of the Tengger Desert,Inner Mongolia,China.We analyzed variations in microbial community composition and enzyme activities during BSCs succession and explored the relationship between these dynamics and soil physicochemical properties.Results revealed that the contents of soil organic carbon(SOC),nitrogen(N),phosphorus(P),silt,clay,and electrical conductivity(EC)in both crust and underlying soils increased significantly as BSCs progressed toward moss dominance,while these variables decreased with greater soil depth.Conversely,pH,bulk density,and sand content exhibited opposing trends.The total phospholipid fatty acids(PLFAs),as well as bacterial and fungal PLFAs,were highest in MC and lowest in AC,with MC exhibiting 24%,15%,and 39%higher values than AC,respectively.Compared to AC,the fungal-to-bacterial PLFAs ratio(F:B)in MC increased by 20%.The microbial community composition in the 0-2 cm and 2-5 cm soil layers followed similar patterns,though all parameters significantly declined with depth.Enzyme activities—sucrase,catalase,cellulase,amylase,polyphenol oxidase,peroxidase,urease,and alkaline phosphatase—showed an upward trend with BSCs succession,but decreased with soil depth.Further analysis revealed that microbial community composition and enzyme activities were significantly positively correlated with SOC,N,P,EC,and clay content,but negatively correlated with pH,bulk density,and sand content.Structural equation modeling suggested that changes in soil chemical properties driven by BSCs succession were the key determinants of microbial community structure and enzyme activities.