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Soil quality (SQ) pertains to the intricate and ongoing capacity of soil to function as a thriving ecosystem that supports the growth of plants and animals. However, there is a limited understanding of SQ assessment in mixed forest plantations. Therefore, we formulated and tested the hypothesis that the inclusion of a nitrogen-fixing tree species (such as Acacia mangium) improves SQ indicators in mixed treatments involving Eucalyptus trees. To evaluate the changes in SQ, we conducted a field experiment that employed the Soil Management Assessment Framework (SMAF) tool to analyze pure and mixed plantations of Eucalyptus grandis and A. mangium. Soil samples were collected at a depth of 0–20 cm from different treatments, including pure E. grandis without nitrogen fertilization (E), pure A. mangium (A), pure E. grandis with nitrogen fertilization (E + N), and mixed E. grandis and A. mangium (E + A). Sampling took place at 27 and 39 months after planting. We selected seven indicators of SQ: two biological indicators (soil microbial biomass carbon and β-glucosidase enzyme activity), four chemical indicators (soil organic carbon, pH, available phosphorus, and potassium), and one physical indicator (bulk density). By applying the SMAF tool, we determined the SQ scores for each indicator. The results revealed that E + A stands exhibited higher SMAF scores than pure stands, particularly in terms of pH (0.49 and 0.52 at 27 and 39 months, respectively) and phosphorus levels (0.84 and 0.82, at 27 and 39 months), respectively. Forest management practices and the sampling period had the most pronounced impact on biological and chemical indicators. Notably, significant positive correlations were observed between SMAF scores and pH, available phosphorus content, enzymes, soil organic carbon, and microbial biomass in both sampling periods. This study effectively provided novel information that introducing a nitrogen-fixing tree species in combination with eucalyptus trees enhances SQ, as indicated by the SMAF tool, which could reduce the need for external inputs (e.g., mineral fertilizers) by the farmers. Future studies should analyze the effects of A. mangium not only with other E. grandis varieties but also with other forestry essences. [ABSTRACT FROM AUTHOR]

A growing demand for resources has led to the expansion of agricultural areas worldwide. However, land conversion associated with poor soil management might lead to soil physical degradation. We investigated the effects of land conversion on soil physical properties in the Brazilian Cerrado region, under native Cerrado vegetation (NV)—pasture (PA) and NV—cropland (CL) conversion scenarios. Soil physical properties related to compaction, pore size distribution, and structure stability were assessed up to a 30 cm depth. Additionally, carbon levels of soil organic matter fractions (particulate and mineral-associated organic matter) were determined. Our results indicate that the compaction process equivalently reduced the soil porosity in PA and CL. However, soil penetration resistance was higher in PA (~2.5 MPa) than in CL (~1.5 MPa), as well as the stable mean weight diameter of soil aggregates. The highest total and labile organic carbon levels were observed in CL, while the lowest levels of total and labile organic carbon occurred in PA (smaller than in CL). These results suggest that the higher structural stability found in PA was mediated by the predominance of stabilized carbon (a decrease in the proportion of soil labile carbon), causing the gaining of soil strength under negligible soil volume variation (in comparison with CL). Our results suggest that the reduction in the soil porosity by compaction due to PA and CL uses can equivalently reduce macropore space and soil hydraulic functioning, and that soil carbon quality alterations (i.e., labile vs. stabilized fractions) are responsible for the gain in soil strength in long-term degraded PA areas. Future research should focus on understanding the magnitude in which soil organic matter controls soil physical attributes, such as soil strength in these expansion areas, and whether this gain in soil strength limits plant development and compromises productivity in the long term. [ABSTRACT FROM AUTHOR]

Silvopastoral systems (SPS) have been widely implemented in the Colombian Amazon region to improve pastures involving a greater diversity of species, soil tillage, fertilization, and higher stocking rate, which can induce changes in soil properties and functions. This study aimed to evaluate soil chemical properties and carbon sequestration changes due to the transition from traditional pastures to silvopastoral systems. The study was conducted in the Colombian Amazon region, specifically in La Montañita and El Doncello Counties, in Caquetá, the second most important hotspot of deforestation in the entire Amazon basin. In each study site, we established a chronosequence consisting of three areas following the typical land‐use change at the region: (i) native vegetation, (ii) traditional pasture, and (iii) silvopastoral system. We found that agricultural practices involving liming and tillage, performed under the silvopastoral management, contributed to reducing soil active acidity and exchangeable acidity with soil pH increasing from 3.8 to 4.3 and H++Al3+ decreasing from 5.8 to 2.3 cmolc kg−1. These alterations favored increases in Ca2+ and Mg2+ contents mainly, increasing the base saturation from 17% in traditional pastures to 55% under silvopastoral systems. The synergic effect of the mix of grasses and trees under silvopastoral management improved soil micronutrient contents and modified soil C stocks in 20–30 cm layer. A rate of soil C accretion of 0.26 Mg ha−1 yr−1 for the 0–30 cm detected in silvopastoral systems suggests that its implementation could be a promising tool for C sequestration in tropical regions, capable of restoring soil functioning of degraded areas. [ABSTRACT FROM AUTHOR]