黄土高原典型维管植物冠层下生物结皮的分布与预测

Distribution and prediction of biocrusts under the canopy of typical vascular plants on the Loess Plateau,Northwest China

维管植物可影响生物结皮的生存环境,进而影响其分布,目前鲜有研究关注维管植物的冠层特征与生物结皮空间分布特征的关系。本研究以黄土高原水蚀风蚀交错区为研究区,调查了维管植物冠层下方生物结皮的分布特征,采用相关性分析和随机森林重要性排序的方法,分析了维管植物冠层特征与生物结皮空间分布的关系,基于随机森林模型构建了维管植物冠层下生物结皮面积的预测模型。结果表明:1)研究区生物结皮类型以藻结皮为主,藓结皮次之。2)维管植物冠层影响生物结皮空间分布,生物结皮主要分布在270°~315°和315°~360°两个方位,在90°~135°和135°~180°两个方位分布较少。3)径向上,生物结皮盖度由维管植物根部向冠层边缘表现出逐渐升高的趋势。4)冠层下生物结皮面积与维管植物冠层面积、长冠幅、短冠幅呈极显著正相关。5)冠层面积、长冠幅、短冠幅对冠层下生物结皮的重要性分别为13.7%、12.1%和11.9%,株高和物种类型的重要性较低,分别为6.7%和4.4%。6)随机森林模型在基于维管植物特征对生物结皮的预测中表现良好,预测精度为0.59(R^(2)),均方根差为1.2 m^(2),能够应用于维管植物冠层下生物结皮面积的预测和估算。本研究为进一步理解半干旱气候区维管植物与生物结皮之间的关系及生物结皮空间分布预测提供了理论依据。

Vascular plants exert significant effects on micro-environment,thereby affecting the distribution of bio-logical soil crusts(biocrusts).The relationship between vascular plants and the spatial distribution characteristics of biocrusts is largely unknown.We investigated the distribution characteristics of biocrusts under the canopy of vascu-lar plants in the water-wind erosion crisscross area of the Loess Plateau,where larger areas of biocrusts had been formed since the implantation of“Grain for Green”project.We analyzed the relationship between the canopy char-acteristics of different vascular plants and the spatial distribution of biocrusts using correlation analysis and random forest importance ranking methods,and further constructed a predictive model for the area of biocrusts under the canopy of vascular plants.The results showed that:1)Cyanobacteria crust was the predominant biocrusts,followed by moss crust.2)The canopy of vascular plants affected the spatial distribution of biocrusts,with notable differ-ences in distribution pattern across different directions under the canopy of vascular plants.Biocrusts were primarily distributed in the 270°-315°and 315°-360°directions,while was less frequent in the 90°-135°and 135°-180°directions.3)Radially,the coverage of biocrusts gradually increased from the root-base to the edge of the canopy of vascular plants.4)The coverage of biocrusts under canopy was significantly related to the characteristics of vascular plants,including canopy area,long crown width,short crown width,litter area and plant height.5)The relative importance of canopy area,long crown width,and short crown width to the biocrusts under the canopy was 13.7%,12.1%,and 11.9%,respectively,while the relative importance of plant height and species type was relatively low,being 6.7%and 4.4%,respectively.6)Results of the random forest model demonstrated strong predictive perform-ance for biocrusts distribution based on canopy characteristics of vascular plants,with a prediction accuracy of 0.59(R^(2))and a root mean square error of 1.2 m^(2).This model could be applied to predict and estimate the area of bio-crusts under the canopy of vascular plants.This study provided a theoretical basis for in-depth understanding of the relationship between vascular plants and biocrusts in semi-arid climate regions,as well as for predicting the spatial distribution of biocrusts.