黄土高原生物土壤结皮分布时空分异特征

Characteristics of spatial and temporal variability in the distribution of biological soil crusts on the Loess Plateau,China

生物土壤结皮(生物结皮)是黄土高原广泛分布的生物地被物,在调节生态系统稳定性和多功能性方面具有重要作用。目前黄土高原生物结皮区域分布特征鲜有报道,限制了该区生物结皮生态功能的评估。本研究基于课题组2009—2020年间5次黄土高原不同降水量带388个样点的生物结皮分布特征调研资料,分析了该区不同退耕年限、降水量、地形(坡向和坡位)和退耕方式(还乔、还灌和还草)下生物结皮的盖度、组成及其影响因素。在此基础上,借助机器学习和空间建模方法,绘制了黄土高原250 m×250 m分辨率生物结皮及组成分布图,分析了黄土高原生物结皮区域空间分布特征。结果表明:黄土高原地区林草地的生物结皮平均盖度为47.3%,其中,藻结皮占25.5%,藓结皮占19.7%,地衣结皮占2.1%,具有明显的时空变化特征。在时间上,对特定区域,生物结皮盖度随封禁年限的延长呈波动式下降,其中,藻结皮和藓结皮盖度呈明显的反向波动。在年内,生物结皮盖度在湿润季节略高于干旱季节。在空间上,风沙区生物结皮盖度较高,且以藻结皮为主,土石山区生物结皮盖度较低。降水量和退耕方式显著影响生物结皮盖度和组成的空间分布,坡向和坡位的影响相对较小。生物结皮的空间分布与土壤有机碳、pH和质地有关。本研究描述了黄土高原区域生物结皮分布的时空分异特征,可为该区生物结皮研究提供数据支持。

Biological soil crust(biocrust)is widely distributed on the Loess Plateau and plays multiple roles in regulating ecosystem stability and multifunctionality.Few reports are available on the distribution characteristics of biocrust in this region,which limits the assessment of its ecological functions.Based on 388 sampling points in different precipitation zones on the Loess Plateau from 2009 to 2020,we analyzed the coverage,composition,and influencing factors of biocrust across different durations since land abandonment,precipitation levels,topography(slope aspect and position),and utilization of abandoned slopelands(shrubland,forest,and grassland).On this base,with the assistance of machine learning and spatial modeling methods,we generated a distribution map of bio-crust and its composition at a resolution of 250 m×250 m,and analyzed the spatial distribution of biocrust on the Loess Plateau.The results showed that the average biocrust coverage in the woodlands and grasslands was 47.3%,of which cyanobacterial crust accounted for 25.5%,moss crust 19.7%,and lichen crust 2.1%.There were significant temporal and spatial variations.Temporally,the coverage of biocrust in specific regions fluctuated with the extension of the abandoned durations and coverage of cyanobacterial crust,while moss crust showed a reverse pattern.In addition,the coverage of biocrust in the wet season was slightly higher than that in the dry season within a year.Spatially,the coverage of biocrusts on the sandy lands area on the Loess Plateau was higher and dominated by cyanobacterial crusts,while the coverage was lower in the hilly and gully area.Precipitation and utilization of abandoned land were the major factors driving biocrust coverage and composition,while slope direction and position did not show obvious effect.In addition,soil organic carbon content,pH,and texture were related to the distribution of biocrust.This study uncovered the spatial and temporal variability of biocrust distribution,which might provide important data support for the research and management of biocrust in the Loess Plateau region.