Altitudinal patterns of dominant invertebrates in forest soil and litter are scale-different

Abstract

Soil invertebrates directly and indirectly contribute to soil formation and development, nutrient cycling, and other ecological processes and are important biological components of terrestrial ecosystems. However, regardless of the large differences in the physicochemical properties between soil and litter, the conditions in which soil- and litter-dwelling invertebrates exhibit similar spatial patterns along the same altitudinal gradient are not clear. In this study, we investigated invertebrates in forest soil and litter layers along an altitudinal gradient (1020–1770m a.s.l.). We used multivariate wavelet analysis to compare the altitudinal patterns of 14 dominant soil and litter-dwelling invertebrates and identified the most relevant factors of these patterns using a Random Forest. The spatial patterns of soil- and litter-dwelling invertebrates differed significantly at 76 m and 206 m scales. The dominant taxa exhibited similar altitudinal patterns at the 76 m and 206 m scales in the litter layer, although they differed at approximately 6 m scale. Moreover, resource diversity (herb richness for litter and tree richness for soil layer) was the main factor affecting the differences in spatial patterns between soil- and litter-dwelling invertebrates at 76 m scale, whereas soil heterogeneity (sand percentage for litter layer and temperature for soil) at the 206 m scale. Our results suggest that the responses of soil- and litter-dwelling invertebrates in forests are not always similar across the same altitudinal gradient and whether they need to be separated depends on their analytical scales. Meanwhile, the factors most related to the pattern differences between the two layers varied with scale. This study emphasises the need to conduct separate investigations and modelling simulations for the litter and soil layers to comprehensively assess soil invertebrate diversity across scales, which will provide valuable insights into the intricate mechanisms underlying the spatial-temporal dynamics of soil invertebrate communities.