Divergent responses of soil fungal communities to soil erosion and deposition as evidenced in topsoil and subsoil

Abstract

Despite the pivotal functional roles dominating the pace of nutrient cycles in terrestrial ecosystems, soil fungal communities at erosional and depositional sites have not been comparatively investigated when assessing the ecosystem stability of eroding landscapes. In this study, soil fungal communities in topsoil (0-5 cm) and subsoil (5-10 cm) on simulated eroding slopes of three slope gradients, i.e., 5°, 10°, and 20°, and in the corresponding depositional zones were examined from 2015 to 2017 in the region of the Chinese Loess Plateau. The results showed that, compared with that in the 5° reference slopes, soil fungal richness in the topsoil and subsoil of the 10° and 20° eroding slopes was 11.8-24.9% lower. However, the richness increased by 2.3-22.7% in the subsoil of the depositional zones, yet not in the topsoil. Soil fungal community compositions in both topsoil and subsoil differed between depositional zones and reference slopes but not between eroding slopes and reference slopes. The differentiation of fungal richness and community compositions between eroding slopes and depositional zones increased with slope gradients, regardless of the topsoil and the subsoil. Saprotrophic fungi levels were 22.5-48.0% lower and pathogenic fungi were 45.2-193.3% higher in the subsoil of the depositional zones with 10° and 20° slopes than in the subsoil of the 5° reference slopes. Soil fungal network on the eroding slope was more complex than that in the depositional zone, suggesting more extensive interactions of fungal taxa and higher community stability potential on eroding slopes. The decreasing soil moisture, organic matter, and other properties on the eroding slopes, in contrast with these properties increasing in the depositional zones, were responsible for the variations in fungal richness and community composition. The divergent responses of soil fungal communities to soil erosion and deposition emphasized the complexity and variability of fungal communities during the soil erosion-deposition processes.

Keywords: Chinese loess plateau; Depositional zone; Eroding slope.