TITLE:
Influence of Substrate Quality and Moisture Availability on Microbial Communities and Litter Decomposition
AUTHORS:
David J. Berrier, Morgan S. Rawls, Shannon Leigh McCallister, Rima B. Franklin
KEYWORDS:
Fungi, Bacteria, Decomposition, Wetland, Marsh, Soil Moisture
JOURNAL NAME:
Open Journal of Ecology,
Vol.4 No.8,
May
30,
2014
ABSTRACT: The main source of
carbon (C) to soil stocks is plant litter, the decomposition of which is controlled
by a mixture of physical, chemical, and biological processes. Bacteria and
fungi are the dominant biota responsible for decomposition, yet we know very
little about their respective contributions or how community dynamics may be
affected by litter quality. This study sought to gain a better understanding of
the variable relationships between organic matter decomposition, litter
quality, and microbial community composition, with a specific focus on
distinguishing bacterial and fungal dynamics. Experiments were conducted under
contrasting hydrological conditions, comparing a wetland with an upland forest
environment. Decomposition of native vegetation was monitored in addition to
breakdown of a common substrate (Acer
rubrum (red maple) leaves) placed in both environments. In situ incubations lasted 16 months,
and were sampled at ~3-month intervals. Regardless of site, maple litter
decomposition proceeded at a similar rate, though we did observe differences in
litter quality over time (C:N, %N, solubility of organic C). For the upland
site, native litter decomposed more slowly than the maple did. At the wetland
site, both litter types decomposed at a similar rate which, surprisingly, was faster
than either litter type at the upland site. This finding could be attributed to
water-limitation at the upland site and/or stimulation of decomposition at the
wetland site due to allochthonous nutrient inputs or organic matter priming.
Substrate induced respiration (SIR) was measured for native litter incubated at
each sampling site, and the relative contributions of bacteria and fungi were
compared. No consistent major differences were detected across these microbial
groups, though we did observe much higher rates of SIR at the wetland site
compared to the upland site. Community structure of each microbial group was
examined via terminal restriction fragment length polymorphism (TRFLP), which
revealed dramatic temporal shifts for both groups at both sites. In general,
these results indicate a long-term effect of both litter type and environmental
conditions (site) on the bacterial community, but show only environmental
effects on the fungal communities. This suggests that different environmental
conditions allow microbial communities to uniquely approach decomposition of
leaf litter components.