Coexistence of Tree Species Promotes the Similarity of the Elementome in Soil Profiles

All living beings are composed of various atoms of chemical elements, and the use of biogeochemical approaches to ecology enables an understanding of the ecological processes connecting organisms with environments. Based on the biogeochemical niche (BN) hypothesis, this study aimed to unravel the responses of the elementomes of the soil to different species of trees. The field experiment was conducted in Chongli, Zhangjiakou City, Hebei Province, China, and soil bioelements were analyzed at three soil layers (A, B, and C horizon) in four forests (Picea asperata (PA), Larix principis-rupprechtii (LP), Betula platyphylla (BP), and Betula platyphylla - Larix principis-rupprechtii (L-B) mixed forest). Based on soil C:N:P stoichiometry, soil elementomes of 11 bioelements (C, N, P, O, S, K, Ca, Na, Mg, Mn, and Cr) were analyzed by principal component analysis (PCA), and elementoms distance (ED) were calculated to investigate differences between horizons and forests. We found that soil elementomes differed in different soil layers and that ED between B and C horizons were larger than that between A and B. Moreover, differences in soil elementomes were smaller for tree species that often coexist compared to those that rarely live together. Our results suggest that tree species coexistence promotes the similarity of soil elementomes and may create soil condition that sustains their coexistence. In conclusion, these findings provide new knowledge on biogeochemical processes driving ecological interactions between organisms and their environments, contributing to a better understanding of terrestrial trophic ecology.