Termites promote resistance of decomposition to spatiotemporal variability in rainfall

Abstract

The ecological impact of rapid environmental change will depend on the resistance of key ecosystems processes, which may be promoted by species that exert strong control over local environmental conditions. Recent theoretical work suggests that macrodetritivores increase the resistance of African savanna ecosystems to changing climatic conditions, but experimental evidence is lacking. We examined the effect of large fungus-growing termites and other non-fungus-growing macrodetritivores on decomposition rates empirically with strong spatiotemporal variability in rainfall and temperature. Non-fungus-growing larger macrodetritivores (earthworms, woodlice, millipedes) promoted decomposition rates relative to microbes and small soil fauna (+34%) but both groups reduced their activities with decreasing rainfall. However, fungus-growing termites increased decomposition rates strongest (+123%) under the most water-limited conditions, making overall decomposition rates mostly independent from rainfall. We conclude that fungus-growing termites are of special importance in decoupling decomposition rates from spatiotemporal variability in rainfall due to the buffered environment they create within their extended phenotype (mounds), that allows decomposition to continue when abiotic conditions outside are less favorable. This points at a wider class of possibly important ecological processes, where soil-plant-animal interactions decouple ecosystem processes from large-scale climatic gradients. This may strongly alter predictions from current climate change models.

Wood decomposition is more rapid on than off termite mounds in an African savanna

“…It seems the decomposition rates associated with active Macrotermes mounds are not dependent on moisture, consistent with Veldhuis et al. (). On a larger scale, Leitner et al.…”

“…A recent study from South Africa found that fungus‐growing termites ( Macrotermes ) maintained high levels of decomposition even when moisture was scarce thus decoupling decomposition rates from rainfall (Veldhuis et al. ). Mound‐building termites occur throughout the ~10 million square kilometer African savanna (Riggio et al.…”

Observed trends of soil fauna in the Antarctic Dry Valleys: early signs of shifts predicted under climate change

“…For example, increased summer temperatures in the region will initiate more frequent freeze-thaw cycles in dry soils, increasing mortality of the dominant invertebrate (Knox et al 2016(Knox et al , 2017. Snow cover in the McMurdo Dry Valleys is patchy and ephemeral, and soils completely lack plant cover and ecosystem engineering macrofauna, thereby they are devoid of abiotic and biotic buffers that, in other ecosystems, can mitigate the impact of harsh atmospheric conditions (Pauli et al 2013, Andriuzzi et al 2015, Veldhuis et al 2017).…”

Comparative responses of termite functional and taxonomic diversity to land‐use change

“…As ecosystem engineers, termites are responsible for large-scale bioturbation, soil aeration, and organic matter decomposition, altering physical, chemical, and biological properties of soils, which in turn affect plant growth and diversity (Garba et al, 2011;Van der Plas et al, 2013;Jouquet et al, 2015). The decomposition of complex organic matter into nutrients available for plants is one of the most important ecosystem services termites provide to tropical forests, which leads to ecosystem stabilisation under global change (Obi & Ogunkunle, 2009;Bonachela et al, 2015;Veldhuis et al, 2017). Termites also increase net productivity of the system, and termite removal in crop fields leads to decreased quality and quantity of the harvest (Evans et al, 2011).…”