Soil Microbial Community and Litter Quality Controls on Decomposition Across a Tropical Forest Disturbance Gradient

Abstract

Industrial logging and agricultural expansion are driving rapid transformations of tropical ecosystems, modifying patterns in above-ground plant and below-ground microbial communities. However, the extent to which these changes in biodiversity drive modifications of ecosystem process rates such as leaf litter decomposition is poorly understood. To determine the relative effects of changes to the chemical quality of litter and shifts in microbial decomposers on leaf litter decomposition rates, we performed a controlled, reciprocal transplant, litter decomposition experiment across a tropical land-use disturbance gradient. Litter mixtures and soils were collected from old growth forest, moderately logged forest, heavily logged forest, and oil palm plantation in Sabah, Malaysia, and combined in a fully crossed, factorial microcosm experiment maintained under controlled environmental conditions. We found that whilst litter quality was the most important predictor of litter mass loss, soil origin was also significant, explaining between 5.17 and 15.43% of total variation. Microbial decomposer communities from old growth forest had greater functional breadth relative to those from logged forests and oil palm plantation as all litter types decomposed faster when combined with old growth soil. The most chemically recalcitrant litter (lowest N, highest lignin, lignin:N, and C:N ratio) from moderate logged forest decomposed faster when combined with its "home" soil (Home-Field Advantage) whilst the most labile litter from oil palm decomposed slowest when combined with its "home" soil. This was correlated with lower total soil microbial biomass. Taken together, these findings demonstrate that whilst litter quality regulated rates of litter decomposition across the disturbance gradient, soil microbial decomposer communities were functionally dissimilar between land uses and explained a significant proportion of variation. The impact of disturbance on soil, including microbial community structure, should be considered alongside changes to plant communities when assessing effects on crucial ecosystem processes such as decomposition.

Comparison of leaf litter decomposition and microbial decomposer communities in fringe and riverine mangroves in French Guiana

“…This HFA could concern litter from different plant species (Ayres et al 2009) but also litter from the same plant species growing in different locations as intraspecific variation in litter quality and decomposition rate can be similar to that reported for interspecific variation (Lecerf and Chauvet 2008). HFA hypothesis is still scarcely studied (Ayres et al 2009;Veen et al 2015), particularly in tropical ecosystems (Wang et al 2013;Wu et al 2019;Elias et al 2020). To our knowledge, only one previous work tested the HFA hypothesis in mangroves, where seedlings growth exposed to leaf litter of different species were assessed (Chapman and Feller 2011).…”

“…In the second phase of decomposition described by Valiela et al (1985) in salt marsh ecosystems (approximately a year), 40 to 70% of litter initial mass is lost through microbial degradation, suggesting that the effect of lower microbial abundance in fringe stands may actually affect decomposition dynamics on a broader timescale (i.e., above 45 days in the case of our study) as shown by Elias et al (2020). After 45 days, catabolic enzyme activities reached the same levels for all tested transplants while after 30 days, FF transfers were lower than RR.…”

Major and persistent shifts in below‐ground carbon dynamics and soil respiration following logging in tropical forests

“…New litter that had fallen onto the collars was removed and discarded prior to each respiration measurement. The litter mass loss during the first month of decomposition in this site is approximately 10% (Elias et al, 2020).…”

Effects of soil conditioning, root and shoot litter addition interact to determine the intensity of plant–soil feedback

“…While very few studies have so far examined the interactive effects of soil conditioning and litter addition (Zhang et al 2019), we would expect an interaction to occur as the effects of each are known to be context‐dependent (Saar et al 2016, Huangfu et al 2019). For example, decomposition of litter does not depend only on the properties of the litter, such as its chemical composition and decomposability (Hoorens et al 2003), but also on the composition and activity of the decomposer communities (Elias et al 2020). These are likely affected by soil conditioning as plants form species‐specific legacies (Dijkstra and Cheng 2007, Phillips et al 2012), supporting specialized decomposers and accelerating decomposition rates (Ayres et al 2009, Veen et al 2015).…”