Soil attributes as indicators of the stabilization process of erosion in gullies at different formation stages in the southeast region of Brazil

Abstract Water erosion is one of the main forms of soil degradation, causing economic, environmental, and social damage. This study evaluated the effects of different formation stages of gullies (initial - IG; juvenile- JG; mature - MG; and senile - SG) on the chemical, organic carbon and microbiological attributes of soil, using a secondary forest (SF) and two areas of pasture as references in the “Mar de Morros” environment of the Brazilian Atlantic Forest biome. Soil samples (depth 0-0.05 m) were collected at the end of the rainy and dry seasons. Gullies in different stages of formation promote a decrease in soil fertility and modification of microbiological attributes, particularly when compared with secondary forest areas. Reductions of over 60% in total organic carbon (TOC), oxidizable organic carbon (POXC), FDA activity, β-glycosidase, acid phosphatase, C and N from microbial biomass, basal soil respiration (BSR) and glomalin-related soil protein (GRSP) were observed in gullies in early (IG) and intermediate (JG and MG) stages when compared to SF. It was found that the effect of erosion on soil chemical and microbiological attributes is more intense in gullies in the initial and intermediate stages compared with those in the senile stage (SG). Using multivariate PCA, the microbiological and chemical attributes of the soil are discriminated between gullies with distinct formation stages. Chemical attributes, TOC, POXC, FDA activity, β-glycosidase, acid phosphatase, MBC and MBN, BSR, and GRSP are good indicators for evaluating the process of erosion stabilization in gullies.

摘要 水蚀是土壤退化的主要形式之一，可造成经济、环境与社会层面的多重损害。本研究以巴西大西洋森林生物群区“Mar de Morros”区域内的次生林（SF）与两处牧场作为参照样地，探究不同形成阶段冲沟（初始期IG、幼年期JG、成熟期MG及衰老期SG）对土壤化学性质、有机碳组分及微生物学属性的影响。分别于雨季末期与旱季末期采集0~0.05米深度的土壤样品。
相较于次生林样地，不同形成阶段的冲沟均会导致土壤肥力下降与微生物学属性改变，其中初始及中期阶段冲沟的影响尤为显著。与次生林相比，初始期（IG）及中前期（JG、MG）冲沟的总有机碳（Total Organic Carbon, TOC）、可氧化有机碳（Permanganate Oxidizable Carbon, POXC）、FDA活性、β-葡萄糖苷酶、酸性磷酸酶、微生物量碳（Microbial Biomass Carbon, MBC）、微生物量氮（Microbial Biomass Nitrogen, MBN）、基础土壤呼吸（Basal Soil Respiration, BSR）及球囊霉素相关土壤蛋白（Glomalin-related Soil Protein, GRSP）均降低了60%以上。
研究发现，相较于衰老期冲沟（SG），侵蚀对土壤化学及微生物学属性的影响在初始与中期阶段冲沟中更为强烈。通过多变量主成分分析（Principal Component Analysis, PCA），可实现不同形成阶段冲沟的土壤微生物学与化学属性的有效区分。其中，土壤化学性质、TOC、POXC、FDA活性、β-葡萄糖苷酶、酸性磷酸酶、MBC、MBN、BSR及GRSP均可作为评估冲沟侵蚀稳定化过程的优良指标。