A Comparative Study on Soil Properties and Enzyme Activities between Picea schrenkiana Forestlands and Grasslands at Different Altitudes

This study focuses on Picea schrenkianaforests and surrounding grasslands in the middle reaches of the Toutun River Basin in Changji City, Xinjiang. It analyzes the distribution patterns and correlations of soil physicochemical properties and enzyme activities along an altitudinal gradient (1,800 m, 2,200 m, and 2,600 m), aiming to provide fundamental data and a scientific basis for understanding soil and water conservation and water source functions of Picea schrenkianaforests. Field sampling and laboratory analysis were employed to measure soil bulk density, water content, porosity, total nitrogen, total phosphorus, total potassium, organic matter, and the activities of urease, acid phosphatase, sucrase, and catalase. The results indicate that forest soils generally exhibited higher porosity, total nitrogen, organic matter content, and acid phosphatase, sucrase, and catalase activities compared to grassland soils. In contrast, grassland soils showed higher bulk density, water content, total phosphorus, total potassium content, and urease activity. Correlation analysis revealed that soil enzyme activities were positively correlated with soil organic matter, water content, and porosity, but negatively correlated with total potassium and bulk density. Redundancy analysis indicated that grassland soil enzyme activities were primarily driven by soil nutrients, whereas forest soil enzyme activities were co-regulated by physical structure and organic matter. This study demonstrates that vegetation type is a key factor mediating the response of soil enzyme activities to altitudinal gradients. These differential response mechanisms are significant for understanding ecological processes in mountain forest-grassland ecotones and for developing targeted management strategies.