Enzyme activities to monitor restoration practices in different soils under caatinga desertification
Stoichiometry; Land restoration; Agroforestry; Conservation practices
Soil degradation has emerged as a significantly urgent environmental concern, contributing to the decline of soil properties in semi-arid regions. However, there is still a gap regarding the effects of desertification and the validation of restoration methods on sensitive soil quality indicators such as enzymatic stoichiometry in the Brazilian semi-arid region. Therefore, this study aimed to evaluate chemical, biological indicators, and enzymatic stoichiometry in soil samples from the Caatinga, a semi-arid region in Brazil. We compared three different conditions: (a) native vegetation of the Caatinga; (b) restored lands, resulting from two decades of agroforestry implementation; and (c) degraded lands, from the desertification core of Cabrobó-PE. Soil samples were collected at depths of 0-10 cm during the dry season to evaluate chemical and biological properties and the levels of C-, N-, P-, and S-acquiring enzymes and their respective stoichiometries. Our findings revealed that the edaphic patterns of degraded (Degraded) and preserved forest (Native) environments are distinct, with a clear predominance of enzymatic activities in "Native" soils. Preserved environments better maintain potassium (K+) stocks, total organic carbon, and microbial biomass, in addition to improving water infiltration and soil moisture retention. In contrast, degraded environments are associated with increased sodium (Na+), indicating worsening soil salinization. Urease activity was the variable that most contributed to environmental variability, according to multivariate analysis. A proposed structural model showed that changes in the natural landscape significantly (r2 = 0.51, p < 0.05) impacted the overall enzymatic activity in soils. Our structural model provides substantial evidence that higher enzymatic activities indicate better environmental preservation and that among the soil chemical variables, K+, Na+, organic carbon, and microbial biomass had relevant contributions to the model. The information obtained here underscores the importance and validation of agroforestry as a method to mitigate the adverse effects of desertification.