Relative roles of termites and saprotrophic microbes as drivers of wood decay: A wood block test

Abstract

Deadwood in tropical ecosystems represents an important but poorly studied carbon (C) pool. Biologically mediated decay of this pool occurs by both saprotrophic microbes and macro-invertebrates, such as termites. The activity of these decay agents is influenced by abiotic conditions, especially water availability in tropical systems. While saprotrophic microbial activity is directly controlled by moisture, termites employ various morphological and behavioural modifications that should allow for continued activity in dry conditions. We therefore hypothesized that the relative role of termites would be enhanced in the dry season and a dry compared to a wet site. We deployed a novel wood bait (Pinus radiata) at two sites (rainforest and savanna), with or without access holes cut into termite-excluding mesh. Mass loss from wood baits was measured after a dry season and after a full dry/wet annual cycle. Mass loss was higher at the rainforest site, demonstrating the overall role of moisture in driving wood decay. Counter to expectations, we found no evidence that the relative role of termites was higher at the dry site, nor during the dry season. However, the prevalence of termites was higher in the savanna compared to the rainforest. While termites clearly impact wood decay, these findings indicate that the relative importance of termites in the fate of deadwood may not reflect their mere presence within and across ecosystems. If moisture availability shifts under climate change, our results suggest similar functional responses between termites and saprotrophic microbes in driving C loss from deadwood.

Dispersal and nutrient limitations of decomposition above the forest floor: Evidence from experimental manipulations of epiphytes and macronutrients

“…We used cellulose because it is common to all plant necromass and a non‐native, novel substrate for the wood sticks ( Betula sp.) to avoid potentially biased effects of coevolved specialists (Cheesman, Cernusak, & Zanne, ). To enable calculations of mass loss, cellulose and wood sticks were dried at 60°C to a constant mass and weighed before placement in the field.…”

Assessing the Australian Termite Diversity Anomaly: How Habitat and Rainfall Affect Termite Assemblages

“…Due to the lack of particular termite feeding groups, there is reason to believe that precipitation plays a different role in shaping termite assemblages in Australia as compared with other tropical regions. Preliminary evidence suggests that although termite activity is impacted by rainfall, it may be in a manner counter to other tropical regions (Cheesman et al, 2017). While we have qualitative descriptions of this anomaly, to date we lack quantitative assessments of how termites change with shifts in rainfall.…”

“…Three of the sites (Sav2, Scl1, and Rft1) change habitat type within 5 km of each other. All sites experience a distinct wet and dry season, with 77% of rainfall occurring between November and April (Cheesman et al, 2017). Because of this seasonality, we conducted termite sampling in both July 2019 (dry season), and December of either 2018 or 2019 (wet season).…”

A Research Agenda for Microclimate Ecology in Human-Modified Tropical Forests

“…Microclimate can be manipulated either actively (e.g., rainfall exclusion, heating, shading; Cavaleri et al, 2015) or passively (e.g., through transplant experiments across microclimate gradients associated with canopy cover or microtopography; Jucker et al, 2018). Taking wood decomposition and soil faunal activity as an example, experiments such as these can be used to identify the primary microclimatic controls of wood decay (Crockatt and Bebber, 2015), compare these effects to those of other local-scale drivers (Bradford et al, 2014) and understand how they are mediated by changes in the decomposer community and by wood traits (Weedon et al, 2009;Riutta et al, 2016;Cheesman et al, 2018). The challenge with these experimental approaches is balancing realism and scale with costs.…”