A comparative analysis of physicochemical and biological properties of Kastanozems and Solonetzes, the two most common soil types in the Caspian region of the post-Soviet territory was carried out. The carbonate, salt, Corg, mineral N (NH₄⁺ and NO₃⁻) contents, microbial biomass (measured by ds-DNA and phospholipids), and activity of 17 hydrolases involved in the C, N, P, and S cycles were measured along the grazing attenuation gradient near a typical sheep farm with year-round grazing. Heavy grazing increases the number of Solonetz areas, they occupy up to 70% of the soil cover. Further away from the farm the areas decrease, and Kastanozems dominate there instead. Both in Kastanozems and Solonetzes, heavy grazing leads to soil salinisation, accumulation of carbonates and nitrates, decrease in ammonia and Corg content, microbial biomass, and enzymatic activity. At moderate grazing, a significant increase in microbial biomass and enzymatic activity throughout the soil profile, particularly in the 0–10 cm layer was found; at light grazing, it was observed mainly in deeper soil layers, not in the upper 0–10 cm. The microbial biomass and enzymatic activity of soils did not directly follow grazing load and was maximal at moderate grazing, where negative effect of reducing phytomass is compensated by large inputs of animal excreta, stimulating development of soil microbial community. Compared to Kastanozems, Solonetzes were more resistant to pasture load, and under heavy grazing, their properties changed to a lesser extent.

中文翻译：

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放牧对俄罗斯南部平原干燥草原土壤结构和生物活性的影响

对后苏联领土里海地区两种最常见的土壤类型 Kastanozems 和 Solonetzes 的理化和生物学特性进行了比较分析。碳酸盐、盐、Corg、矿物 N（NH ₄ ⁺和 NO ₃ ^-) 含量、微生物生物量（通过 ds-DNA 和磷脂测量）以及参与 C、N、P 和 S 循环的 17 种水解酶的活性沿着一个全年放牧的典型羊场附近的放牧衰减梯度进行测量。重度放牧增加了 Solonetz 地区的数量，它们占据了土壤覆盖的 70%。离农场越远，面积越小，而是 Kastanozems 在那里占主导地位。在 Kastanozems 和 Solonetzes，重度放牧导致土壤盐碱化、碳酸盐和硝酸盐的积累、氨和 Corg 含量、微生物生物量和酶活性的降低。在适度放牧时，发现整个土壤剖面的微生物生物量和酶活性显着增加，特别是在 0-10 厘米层；在轻度放牧时，主要在较深的土壤层中观察到，不在上部 0-10 厘米。土壤的微生物生物量和酶活性不直接跟随放牧负荷，在适度放牧时最大，减少植物量的负面影响被动物排泄物的大量输入所补偿，刺激了土壤微生物群落的发展。与 Kastanozems 相比，Solonetzes 更能抵抗牧草负荷，并且在重度放牧下，它们的特性变化程度较小。