The resource coupling role of animal foraging pits in semi‐arid woodlands

Abstract

Water is a strong driver of ecosystem function and diversity in resource-limited drylands. Structures that alter the redistribution of water have the potential to affect vegetation pattern and productivity and the maintenance of spatial heterogeneity. We examined the role of surface foraging pits and mounds constructed by the short-beaked echidna (Tachyglossus aculeatus) on runoff generation, sediment detention and seed capture. We speculated that pits dug into biologically crusted interspace soils would reduce overland flow and act as sinks for seed, while mounds of ejected soil would increase sediment availability. Runoff and sediment yield were examined under simulated rainfall with five levels of disturbance representing the pits and mounds of echidnas. Increasing the level of disturbance up to 47% cover of mounds and pits had no effect on time to ponding, steady-state runoff or the coefficient of runoff. However, time to initiation of runoff, sediment removal rates and sediment concentration in runoff water increased with increasing disturbance. Pit-to-pit and surface-to-pit movements of Dodonaea viscosa seed tended to increase, while pit-to-surface movements tended to remain unchanged with increasing disturbance. Surface-resident seed generally moved shorter distances with increasing disturbance. The results highlight the importance of mounds and pits of soil foraging animals for generating and trapping eroded sediment. Runoff and erosion processes may therefore provide a mechanism for coupling critical resources such as seed, water and sediment in resource-rich patches that will contribute to the development of small-scale heterogeneity in woodlands.

Does litter decomposition vary between the foraging pits of two soil‐disturbing mammal species?

“…Our results suggest that soil texture affects the rates of substrate burial and initial decomposition. Soil texture also has a significant effect on foraging pit longevity (Eldridge et al , ), with lower half‐lives of pits formed on coarse‐textured than fine‐textured soils (Eldridge, ). We used landform as a surrogate for soil texture, comparing decomposition rates from sandy dune crests with loamy inter‐dunal swales.…”

Animal foraging as a mechanism for sediment movement and soil nutrient development: Evidence from the semi-arid Australian woodlands and the Chihuahuan Desert

“…Thus one of the functions of foraging disturbances is to bring together nutrients and Table 2 Mean (± SE) density (foraging pits ha − 1 ), volume (cm 3 per disturbance) and mass of soil (t ha − 1 ) for echidnas and goannas across the three treatments in eastern Australia. Different subscripts with a row indicate a significant difference at P b 0.05. water with pit-resident seed, maximizing the chances of an ecological response (Eldridge, 2011). The tendency of pits to develop into resource-rich patches depends on the texture and aggregation of the substrate and the extent to which entrained material remains in situ or is winnowed out.…”

Is ecohydrology missing much of the zoo?

“…Further, the literature is rich with reports of how ecosystem engineers, animals that directly regulate resource availability (Jones et al, 1994), influence hydrological processes. For example, alligators (Mazzotti et al, 2009), beavers (Westbrook et al, 2013), short-beaked echidna (Eldridge, 2011), earthworms (Farenhorst et al, 2000), and aquatic invertebrates such as crayfish and river crab (Stone, 1993;Onda and Itakura, 1997) influence ecosystem hydrology through their damming, burrowing, digging, slope loading, and trampling/wallowing activities (Figure 2; Hall and Lamont, 2003;Butler, 2006).…”