Tree Soil Carbon, Nitrogen and Associated Bacterial Community Compositions, Stability, Evenness and Diversity Are Enhanced along an Age Gradient of Planted Inga Punctata Trees.

Abstract Aims This study was designed to determine if planting the leguminous tree Inga punctata in formerly cleared former tropical premontane wet forests changed the Nitrogen (N)-fixer and Lignin Degrader community compositions resulting in increased accumulation of soil carbon (C) and N components. Methods Soils were collected from old growth (> 50 years old), 4, 8 and 11-year-old I. punctata trees, and assessed for differences in various soil C and N metrics, and the mean proportion of sequences (MPS, as “relative abundance” via 16S rRNA V3, V4 sequencing), composition, stability and evenness of the community of N-fixer and Lignin Degrader genera. Results The N-fixer MPS decreased, and Lignin Degraders increased, while evenness and stability of both increased along the tree soil age gradient. The Lignin Degrader MPS were positively correlated with TN, NO3−, TOC, and Biomass C, and negatively correlated with N-fixer MPS and soil NH4+. The N-fixer MPS were negatively correlated with TN, NO3−, TOC, Biomass C and Lignin Degrader MPS, and positively correlated with NH4+. Evenness, stability, and diversity increased for both groups along the tree soil age gradient. Conclusions This is the first evidence that I. punctata facilitates changes the tree soil N-fixer and Lignin Degrader communities over time by increasing the diversity, evenness and stability of both groups, and increases the accumulation of tree soil C and N. This suggests I. punctata facilitates soil recovery such that it can serve as C and N sinks, and support its future use in reforestation management strategy.