Key message

Mineral soil, litter and root from 4 tree species at 4 sites were compared in this study. Excluding site interference increased the discriminability of interspecific difference. Mineral SOC (soil organic carbon) and soil N (nitrogen) were 20−40% higher in Elm. Soil P (phosphorous) was 40% lower in poplar, and pine litter was more recalcitrant.

Abstract

Effects of tree species on mineral soil, litter and root properties are found to be inconsistent, and understanding general cross-site pattern and possible mechanism is important for enhancing the forest ecological service through proper tree species selection. In this study, four tree species including larch (Larix gmelinii), pine (Pinus sylvestris var. mongolica), poplar (Populus spp.), and elm (Ulmus pumila) at four sites were selected; and 34 parameters comprised of mineral soil C, N, and P, litter and root chemical compositions, and stand structure were measured to compare the interspecies differences across different sites. Different statistical methods were used to compare their discriminability of interspecies differences, and site-effect exclusion could increase the discriminability, especially Two-way MANOVA (multivariate analysis of variance). Cross-site pooled data statistics showed that mineral SOC and soil N concentrations in elm were 40% and 20% higher and mineral soil P in poplar was 40% lower as compared with those in other tree species across sites. No interspecies difference was found in soil C/N, C/P, and N/P ratios. Pine had the peak litter C, C/N, C/P, cellulose, and holocellulose, while no interspecies difference was found in root chemical compositions across sites. Variation partitioning found that interspecies differences were strongly interacted with site-geoclimatic conditions. Interspecies variation on mineral soils could be explained more by the geoclimatic conditions (> 95%), while much less was for litter (50%) and roots (20%). Our results indicated that elm could capture more mineral SOC and soil nutrients, poplar induced mineral soil P depletion, and pine litter was of more recalcitrance for decomposition; However, general differences among four taxonomic species were not always observed across sites. Future afforestation practices in this region should fully consider matching tree species with site conditions, such as in the Three North Shelterbelt Projects.