Simulated Pulses of Senescent Plant Matter Structure Brown Food Web Pathways in an Arid Ecosystem

Abstract The functioning of arid ecosystems is typically understood through the lens of green food webs, driven by episodic “green pulses” of primary productivity that follow rainfall. However, often overlooked brown food webs rely on energy contained within senescent plant material that develops in the aftermath of plant-growth pulses. These “brown-pulses” are likely to be key channels for energy transfer during the dry periods that usually prevail. By consuming living vegetation before it senesces, grazing by herbivores could deprive energy from brown food webs. To investigate the effects of resource pulses and mammalian herbivores on brown food webs in an arid ecosystem, we simulated a resource pulse by adding litter (haybales) and excluding herbivores from the litter. We then monitored responses of termites, key macro-detritivores, and the abundance and diet of insectivorous small mammals ( Sminthopsis spp.). Addition of litter increased the likelihood of finding termites but did not affect the abundance of Sminthopsis . The frequency of termite consumption by Sminthopsis spp. tended to increase as termites were more likely to be found. Herbivores reduced litter biomass but did not affect termite populations. Our results illustrate the importance of “brown-pulses” of senescent plant biomass for energy transfer through direct interactions within brown food webs in arid ecosystems.