Landscape Transformation of Degraded Shrublands to Pine Forestations Increases Biological Soil Crust Cover and Creates Small‐Scale Soil Heterogeneity

Abstract

Efforts to reverse dryland degradation and desertification promote the transformation of rangelands to forestations. Biologicalsoil crusts (biocrusts), a structural and functional component of drylands, have been primarily studied in rangelands, and seldomin other land-usetypes. The fate of biocrusts following tree afforestation remains unclear, limiting the understanding of the impactsof plantations on soil biota and functioning. In a grazed steppe with pine forestations, both land-usetypes were comparedevaluating the influence of vegetation features and a regional precipitation gradient on biocrust community structure. The contributionof biocrusts to small-scaleheterogeneity in soil properties (moisture, nutrients, carbon, and pH) within the forestationswas also quantified. Biocrusts covered 16.5% of the forestation ground surface, a value one order of magnitude higher than in thenatural vegetation (2.1%). Differences in species relative abundance suggested that biocrusts under pines represented an earliersuccession stage compared to those in the natural vegetation. The precipitation gradient significantly modulated biocrust developmentin both land-usetypes. Within the forestations, biocrust cover was favored in partially opened canopy patches, with arelatively thin litter layer. Biocrusts had no significant effect on soil properties, which were mostly enhanced in deep needle-litterlayer patches, and were modulated by the regional precipitation gradient. Our results provide novel evidence suggesting that pineforestations act as reservoirs and effective restoration agents for biocrusts in long-termgrazed landscapes. Management practicesof land-usemosaics should aim to enhance biocrusts in the forestations, as these actions could contribute to preserving drylandbiodiversity and integrity.