Title

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

Document Type

Presentation

Publication Date

12-2014

Abstract

Diversity and structure of the soil microbial community (SMC) significantly affects soil ecosystem services including, nutrient cycling, C-mineralization, and stabilization/formation of soil structure. SMC also responds to changes in soil moisture and chemistry. Stemflow, the concentration of precipitation to soils at the trunk base, is well known to alter these edaphic conditions near the stem. Thus, the aim of this study is to investigate the potential link between stemflow and SMC structure. Soil samples collected near stems of two tree species of contrasting stemflow character (Fagus grandifolia [AB] and Liriodendron tulipifera [YP]) were evaluated for changes in chemical properties and SMC structure via PCR-DGGE (denaturant gradient gel electrophoresis) in summer, winter, and spring. Variations within the SMC DGGE banding profiles were determined by GelCompare II software and Nonmetric Multidimensional Scaling (NMDS) analysis. Sequencing and phylogenetic analyses of dominant and unique DGGE bands was conducted to identify shifts in significant SMC organisms. Our results demonstrate that stemflow can alter edaphic conditions near individual tree trunks, and that temporal soil moisture trends, soil pH, PO43-, SO42-, and Ca2 can further vary in response to species-specific stemflow supply characteristics. This, in turn, may explain SMC structural and diversity differences in the proximal area (< 0.5 m) of different SMC species’ near tree trunks. Specifically, SMC diversity (particularly bacterial) increases where stemflow resources are unevenly input for YP but decrease for AB which has more consistent stemflow inputs. Soil chemistry and microbial community differences between species’ proximal areas also indicate the potential for stemflow processes to influence soil pH, and therefore nutrient status, including SOM. Seasonal patterns in DGGE banding patterns and intensity further show that as stemflow characteristics change with canopy phenology and meteorological conditions, so do specific clades or species (e.g., ectomycchorizal and saprophytic fungi, or proteo- and actinobacteria).

Sponsorship/Conference/Institution

American Geophysical Union Fall Meeting (AGU)

Location

San Francisco, CA