黄土丘陵区生物结皮对土壤物理属性的影响

生物结皮在干旱、半干旱地区广泛发育。迄今,有关生物结皮发育过程中土壤物理属性的响应仍不明确。论文采用野外调查与室内分析相结合的方法,定量研究不同生物量生物结皮对土壤物理属性的影响。结果表明:①生物结皮的发育能够细化土壤,当生物结皮由初期藻结皮演替至60%~80%苔藓结皮时(5等级),生物结皮层粗砂粒含量降低了86%;②随着生物结皮生物量的增加,生物结皮层土壤容重和硬度较初期分别降低了15%和68%,田间持水量和孔隙度分别增加了36%和14%;生物结皮层粘结力是下层土壤的6~7倍;③生物结皮的发育对土壤物理属性的影响与生物量有关,当苔藓生物量达2.91±0.12 g/dm²时,其土壤物理属性基本稳定。研究结果为揭示生物结皮抗侵蚀机理提供了科学参考。

Impact of Biological Soil Crust on Soil Physical Properties in the Hilly Loess Plateau Region,China

Biological soil crusts(biocrusts) are ubiquitous living surface covers in many arid and semi-arid regions.It has been demonstrated that the coverage of biocrusts was over 70% in the hilly Loess Plateau region of China and it played many important roles,such as exerting observably impact on soil properties and improving soil antierodibility.But the response of soil physical properties to the development of biocrusts has been unclear so far.The objective of the study was to determine the impact of development of biocrusts(i.e.with variable biomass) on soil physical properties in hilly Loess Plateau region.In this study,soil samples were collected after biocrusts and vegetation coverage survey,and the soil physical properties including soil bulk density,soil porosity,field water holding capacity,cohesion and hardness of biocrusts in different developmental stages were determined.The results showed: 1) Fine particles content increased due to the development of biocrusts.The content of coarse sand decreased by 86% while fine sand increased by 45% with biocrusts developing from cyanobacteria dominated to moss dominated(biomass of moss was 4.31±0.12 g/dm2).2) With the development of biocrusts,soil bulk density and hardness were reduced while field water holding capacity,soil porosity and cohesion were increased significantly.Along with the development of biocrusts,soil bulk density was dropped by 15%.Soil hardness of biocrusts in later development stage was reduced by 68% compared with the early stage.Field water holding capacity was increased to 57%,adding about 36% compared with the early stage,while soil porosity gone up to 58%,increasing by about 14%.Cohesion of biocrusts was 6 or 7 times as much as that of subsurface soil(0-2 cm).3) Impact of biocrusts on soil physical properties was closely related to biocrusts’biomass.When biomass of moss in biocrusts was to 2.91±0.12 g/dm2,soil physical properties changed no longer significantly.4) Soil physical properties not only in the layer of biocrusts,but also in the subsurface soil under the biocrusts were affected by the development of biocrusts.In conclusion,the results of our study suggested that soil physical properties were influenced by the development of biocrusts significantly.The study would likely provide scientific basis for the mechanism of soil antierodibility improvement by biocrusts.