Irruption of herbivore populations due to the extirpation of predators has led to dramatic changes in ecosystem functioning worldwide. Herbivores compete with other species for their primary source of nutrition, plant biomass. Such competition is typically considered to occur between species in closely related clades and functional groups but could also occur with detritivores that consume senescent plant biomass. Here, we test predictions that herbivores’ indirect impacts on dead vegetation increase with primary productivity and extend to termites which feed on senescent vegetation. We compared dead vegetation cover and termite activity in herbivore exclosures and associated grazed plots at 3 locations situated along a rainfall gradient in arid Australia where kangaroo populations have irrupted. Dead vegetation cover and termite activity increased with rainfall in ungrazed plots but showed a negligible response to rainfall in grazed plots. Our results suggest that grazing can disrupt the flow of energy to detritivores and decouple the relationship between termite activity and primary productivity. Such disruption could have far-reaching impacts on arid ecosystems because many organisms sit within “brown food webs” that are sustained by energy derived from decomposition of senescent plant-tissues. 

We compared dead vegetation cover and termite activity in herbivore exclosures and associated grazed plots at 3 locations situated along a rainfall gradient in arid Australia where kangaroo populations have irrupted. We used R software to run linear regression models and linear anlayses to compare differences in vegetation biomass, termite activity, and termite community composition across the exclosures and the controls. 

R software