施氮对高寒草地土壤团聚体生物胶结物质及稳定性的影响OA北大核心CSTPCD

In recent years,human activities and climate change have led to the deterioration of soil structure in alpine grasslands.Soil aggregates,as the fundamental structural units of soil,are mainly stabilized by the presence of biogenic substances.However,there is limited research on the relationship between soil aggregate characteristics and biogenic substances in grassland soils.In order to clarify the differences in soil aggregate biogenic substances and stability under different nitrogen application levels,the alpine grasslands of Hongyuan were studied.A randomized block design with seven nitrogen rates was employed,namely 0(CK),10,20,30,40,50,and 60 g·m-2 urea(46.7%N).The differences in soil aggregate composition and stability in relation to the content of biogenic substances were measured and analyzed.The results showed that:1)Soil aggregates in alpine grasslands were mainly in the 2-4 mm size class,which accounted for 34.22%of the total.Different nitrogen rates significantly influenced soil nutrient content,aggregate composition,and stability(P<0.05).2)The content of biogenic substances[soil spore density,hyphal density,easily extractable glomalin(EEG),difficult-to-extract glomalin(DEG),and total glomalin(TG)]varied significantly under different nitrogen rates(P<0.05).Specifically,the highest spore density value of 72.33 ind·g-1 occurred in N10,the lowest hyphal density value of 0.48 m·g-1 occurred in N60,and the highest TG value of 6.84 mg·g-1 occurred in N60.3)Correlation analysis revealed a significant positive correlation between hyphal density and the percentage weight of 2-4 mm soil aggregates,and a highly significant negative correlation with the percentage weight of 0.25-1.00 mm soil aggregates.The percentage weight of 0.25-1.00 mm soil aggregates was significantly positively correlated with glomalin.Stepwise regression analysis identified EEG as an important factor influencing changes in the percentage weight of soil aggregates<0.25 mm(R2=0.26).Path analysis demonstrated that hyphal density had the largest direct positive effects on mean weight diameter(MWD)and geometric mean diameter(GMD),with values of 0.79 and 0.78 respectively.The study results indicate that nitrogen application reduces the stability of soil aggregates in alpine grasslands,with hyphal density and EEG having the most significant effects on soil aggregate composition and stability(P<0.05).