The effects of aboveground diversity, litter chemistry, and successional stage on decomposition in subtropical dry forests, St. Croix, US Virgin Islands
Abstract
Litter decomposition is important for soil organic matter formation and nutrient cycling in terrestrial ecosystems, but our understanding of decomposition in subtropical forests is limited. These ecosystems are highly fragmented due to human activity and are very susceptible to changes in rainfall. Here, we examine how site conditions and litter chemistry influence decomposition dynamics in successional forests in St. Croix, US Virgin Islands. To examine differences in microbial processing of aboveground inputs, we conducted a 22-month in-situ and reciprocal field decomposition experiment using aboveground litter from two forests differing in composition and successional stage. The 10-yr forests in this study are dominated by an early successional N-fixing tree and the 40-yr forests are highly diverse, mixed-species forests. Litter mass loss rates show that 10-yr forest litter decays faster than 40-yr forest litter, regardless of the decomposition environment (p < 0.001), likely due to 10-yr forests litter having a lower C:N ratio than 40-yr forests (≈20 vs 37). PLFA microbial community analysis indicates that the primary decomposers in the 10-yr and 40-yr forests are fungi and bacteria, respectively, both of which have greater forest floor biomass during the dry season. To follow alterations in chemical composition of the decaying litter we analyzed its chemistry using FTIR and solid state 13C NMR spectroscopy. Litter chemistry showed interesting changes in C functional groups during the experiment that highlight the importance of litter quality and decomposition environment. FTIR peak intensities for bands representing aliphatic functional groups decrease gradually over the course of the experiment for 40-yr forest litter and rapidly for 10-yr litter, but only the 40-yr litter signal intensity differs between decomposition environments (p < 0.001). NMR spectra show greater Alkyl/O-alkyl ratios at the end of the experiment for 40-yr forest in-situ decomposition vs the reciprocal transplant in the 10-yr forest, but both have higher ratios than both decomposition environments for the 10-yr forest litter. Our results highlight the importance of forest diversity and litter chemistry on forest floor stability and litter decomposition at different forest successional stages in subtropical dry forests.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB116.0024K
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 3337 Global climate models;
- ATMOSPHERIC PROCESSES;
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES