祁连山东段高原鼢鼠(Eospalax baileyi)土丘空间分布格局及其与环境因子的空间关联性

高原鼢鼠推土造丘行为对高寒草地生态系统的生产和生态功能有重要影响,研究高原鼢鼠土丘空间分布格局及其与环境因子的关系,可以揭示高原鼢鼠栖息地利用和选择规律,为合理控制鼠害及保护草地生物多样性提供科学依据。于2014年8月在祁连山东段选取面积为140m×100m的高原鼢鼠栖息地,消除景观尺度取样带来的气候、地形和土壤的异质性,利用地统计学方法,分析高原鼢鼠土丘的空间分布格局、并揭示其与环境因子中土壤容重、土壤水分、植物地上、地下生物量、根系营养物质含量(可溶性糖、粗蛋白、粗脂肪)以及各功能群丰富度(禾本科、莎草科、杂类草)的空间关系。半方差函数及普通克里格插值表明,高原鼢鼠土丘存在中等程度的空间变异且呈现聚集分布,各环境因子均存在不同程度的空间异质性。交方差函数分析表明,高原鼢鼠分布虽与各环境因子在多种尺度下表现出复杂的空间关联性(正的或负的),但mantel检验发现土壤容重、莎草科丰富度与高原鼢鼠土丘分布呈现显著的负空间关联性,杂类草丰富度和根系粗脂肪含量与高原鼢鼠土丘分布存在显著正空间关联性。综上所述,高原鼢鼠主要栖息利用在土壤疏松、莎草科丰富度较低、杂类草较多和根系粗脂肪含量较高的地方。

Relationship between the spatial distribution of the mounds of plateau zokor (Eospalax baileyi) and environmental factors in eastern Qilian Mountain

Plateau zokor (Eospalax baileyi) is a subterranean rodent endemic to the Tibetan Plateau, and it plays an important role in the alpine rangeland system because of the ecosystem function in terms of substance circulation and energy exchanges. However, at high population density, zokors are regarded as pests aggravating the degradation of rangelands. As zokors live underground, they dig tunnels in the soil for foraging or mating. In digging tunnels, the soil is pushed out on the ground as mounds, which reduce the grazing area and cover the forages. However, the mounds made by zokors create environmental heterogeneity, which increases the species diversity and nutrient recycling in soil. Therefore, the mounds have an important impact on the alpine rangeland ecosystem. Studying the spatial distribution of plateau zokor mounds and its correlation with environmental factors can reveal its role in habitat use and selection, which is the basis for controlling zokor damage and protecting biodiversity in the place. The variables of traditional statistics must be random variables, and the traditional statistics can not clarify the relationship between the variables and geographic location. As a result, the traditional statistics can not explain the reasons that influence the spatial distribution patterns in population studies. Currently, the geostatistical analysis methods are often used to study population spatial distribution patterns. In our study, we selected the small habitat of plateau zokor (140m×100m) in eastern Qilian Mountain because a small habitat can eliminate the heterogeneity of climate and geography. We used the semivariogram and ordinary kriging of geostatistical analysis methods to analyze the spatial heterogeneity of zokor mounds and the environmental factors that influence the distribution of mounds. The purpose of this study was to determine the relation between the distribution of zokor mounds and environmental factors, including soil bulk density, soil moisture, aboveground biomass, underground biomass, root''s water-soluble sugar, crude protein, crude fat, richness of grass, and richness of forbs and sedges. The results of semivariogram and ordinary kriging indicated that the mounds of plateau zokor presented clumped distribution with medium variation level, and all environmental factors had spatial heterogeneity in the studying site. The results of a crossvariogram analysis showed that the distribution of zokor mounds had a positive spatial correlation with soil moisture and aboveground as well as underground biomass at the same studying scale (10.74-71.85m). The distribution of zokor mounds had a positive spatial correlation with forage nutrients, such as root''s crude protein and water-soluble sugar at the studying scale (10.74-30.82m), as well as root''s crude fat at the studying scale (10.74-44.01m). Besides, the distribution of zokor mounds had a positive spatial correlation with forbs at all studying scales. The mantel test indicated that the distribution of zokor mounds had a significant negative spatial correlation with soil bulk density and richness of sedge and a significant positive spatial correlation with richness of forbs and the contents of root''s fat. In conclusion, the plateau zokors prefer to select the alpine meadows with softer soil, more forbs as well as plants with higher root''s fat in this studying site.