Soil texture modulates the intensity of fertile islands through affecting the distribution of shrub fine roots

摘要

Fertile islands play an important role in ecosystem structure and function. However, studies on the effects of fine roots of desert shrubson fertile islands in contrasting textured soils are scarce. We investigated soil water and nutrient contents, microbial biomass, fine root densities of Haloxylon ammodendron (C.A.Mey.), and their enrichment indices along a soil profile (100 cm deep and 200 cm wide) in two soils: Torripsamment (coarse-textured) and Haplocalcid (fine-textured). In both soils, water and nutrient contents, microbial biomass, and fine root densities decreased with increasing distance from the taproot. Their enrichment indices exceeded 1.0, except at the 190 cm distance from the taproot. Compared with the Haplocalcid, the Torripsamment had higher enrichment levels for all parameters, which mainly occurred at 0-20 and 20-60 cm depths. The enrichment indices of fine root densities were positively related to those of soil variables at similar depths, and the relationships were more intense in the Torripsamment than in the Haplocalcid at 0-20 and 20-60 cm depths. These results suggest that fine root distribution along the soil profile promotes fertile islands extending from the surface to deep soils. Soil texture affects fine root distribution and consequently modulates the intensity of fertile islands.