Seasonal Dynamics of Soil Microbial Community Structure Within the Proximal Area of Tree Boles: Possible Influence of Stemflow

Soil microbial community (SMC) structure affects several ecosystem services (soil-carbon mineralization and stabilization), yet responds to edaphic conditions. Stemflow, water that drains over the exterior surface of trees, concentrates precipitation to soils near the trunk, thereby altering edaphic conditions. While recognizing that a suite of factors can affect soils, our research investigates the potential linkages between soil moisture, chemistry, and SMC structure within near-trunk soils from two species of contrasting stemflow production (Fagus grandifolia Ehrh. [American beech, AB] and Liriodendron tulipifera L. [yellow poplar, YP]) across seasons. Variations in SMC structure were determined by Nonmetric MultiDimensional Scaling (NMDS) analysis of Denaturing Gradient Gel Electrophoresis (DGGE) banding patterns. Sequencing/BLAST analysis of dominant DGGE-bands were conducted for shared and unique bands occurring in both AB and YP stemflow-influenced soils. Findings suggest species-specific differences in stemflow potentially alter moisture dynamics, pH, mineral nutrients, and soil-C near-trunk soils. SMC structure also increases in variability under low stemflow flux (i.e., for YP). However, SMC structural variability decreases for near-stem soils across individual trees and seasons when stemflow flux is consistently high (i.e., for AB). Differences in canopy structure that govern stemflow production may be a plant trait capable of altering SMC structure. Variation in SMC structure may be related to tree species stemflow input fluctuation response to seasonal change. Future investigations should consider intricate interrelationships among stemflow and species composition of the SMC in near-trunk soils in order to better contextualize the effect of stemflow on SMC vis-à-vis other factors, such as litter quality