Enhanced Carbon, Nitrogen and Associated Bacterial Community Compositional Complexity, Stability, Evenness, and Differences Within the Tree-Soils of Inga Punctata along an Age Gradient of Planted Trees in Reforestation Plots

This study was designed to determine if planting the leguminous tree Inga punctata in previously 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. Soils were collected near the base of 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 N-fixer and Lignin Degrader community genera. The N-fixer MPS decreased, and Lignin Degraders increased, while evenness and stability of both increased in soils along the tree age gradient. The Lignin Degrader MPS were positively correlated with TN, NO3−, TOC, and Biomass C, and negatively correlated with N-fixer MPS and 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 dissimilarity increased for both groups in soils along the tree age gradient. This is the first evidence that I. punctata facilitates changes in tree-soil N-fixer and Lignin Degrader communities over time by increasing the dissimilarity, 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.