A meta-analysis of physicochemical changes in the rhizosphere and bulk soil under woodlands

Monoculture for timber production has been replacing natural environments as the demand for renewable energy sources increases. The lack of nutrient compensation may increase the risk of soil depletion, thus changing soil properties. To summarize the impact of forestry activities in edaphic environments, we present a meta-analysis on the rhizosphere effects of coniferous and broadleaved trees established as monoculture and natural regeneration on soil physicochemical properties. Records of soil attributes published in peer-reviewed journals from eight countries were collected. Clay content changed only in monoculture sites, decreasing 55.51% in the rhizosphere, while silt and sand presented significant variations in both monoculture and naturally regenerated areas. Conifers affected the soil more than broadleaved trees, evidenced by higher pH reduction (-2.96% vs. -1.98%) and higher increase of Al3+ (197.43% vs. 50.68%), K+ (80.40% vs. 69.90%), CEC (24.61% vs. 17.35%), and total organic carbon (82.21% vs. 69.89%). Also, the rhizosphere affected regeneration soils more than monoculture, indicated by higher Al3+ (50.68% vs. ns) and available P (32.31% vs. ns), K+ (203.44% vs. ns), CEC (34.90% vs. 20.93), and total organic carbon (91.55% vs. 63.23%). These results indicate higher nutrient availability in naturally regenerated than monoculture sites, as higher species diversity and better plant litter quality are expected. This meta-analysis shows that coniferous and naturally regenerated trees had a higher influence on the rhizosphere and soil properties than broadleaved and monocultures. Management practices must be revisited to ensure the long-term sustainability of forestry activity, and studies in tropical zones must be intensified.