Bioturbation by bandicoots facilitates seedling growth by altering soil properties

Abstract

Animals that forage for food via bioturbation can alter their habitat, influencing soil turnover, nutrient cycling and seedling recruitment, effectively acting as ecosystem engineers. Many digging mammals forage for food by digging small pits and creating spoil heaps with the discarded soil. We examined how small‐scale bioturbation, created by the foraging actions of an ecosystem engineer, can alter soil nutrients and subsequently improve growth of plants. We investigated the microbial and chemical properties of soil disturbed by the foraging of an Australian marsupial bandicoot, quenda (Isoodon fusciventer). Soil was collected from the base of 20 recent foraging pits (pit), the associated spoil heaps (spoil) and adjacent undisturbed soil (control) and analysed for nutrients (phosphorus, potassium, sulphur, organic carbon and conductivity) and microbial activity. Soil cores were collected from the same locations and seeds of the dominant canopy species, tuart (Eucalyptus gomphocephala), added to the soil under glasshouse conditions. The growth of seedlings was measured (height, maximum growth, basal stem width, shoot and root biomass) over a 4‐month period and arbuscular mycorrhizae (AM) fungi colonisation rates of seedling roots investigated. Soil from the spoil heaps had the greatest levels of conductivity and potassium. Both the spoil and undisturbed soil had greater amounts of microbial activity and organic carbon. In contrast, the pits had less nutrients and microbial activity. Seedlings grown in spoil soil were taller, heavier, with thicker stems and grew at a faster rate than seedlings in the pit or control soil. Colonisation with AM fungi was greatest for seedlings grown in pit soil. The best predictors of seedling growth were greater amounts of potassium, electrical conductivity and microbial activity. The best predictor of higher colonisation rates of AM fungi was less phosphorus. Bioturbation by ecosystem engineers, like quenda, can alter soil nutrients and microbial activity, facilitating seedling growth. We propose this may be caused by enhanced litter decomposition beneath the discarded spoil heaps. As the majority of Australian digging mammals are threatened, with many suffering substantial population and range contractions, the loss of these species will have long‐term impacts on ecosystem processes. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13179/suppinfo is available for this article.

Ecosystem engineering by digging mammals: effects on soil fertility and condition in Tasmanian temperate woodland

“…These effects consist, first, of direct physical displacement and loosening of soil. Digging of foraging pits also mixes soil from surface and sub-surface layers, and it incorporates litter into soil because some litter is buried under spoil heaps [35,36]. Loosening of soil by bettongs and other mammals allows higher water infiltration [10,37]; also, the foraging pits themselves capture water that would otherwise flow across the undisturbed soil surface and be partially lost from the local habitat.…”

Thinking systemically about ecological interventions: what do system archetypes teach us?

“…Pollock 2019). Similarly, there is accumulating evidence that elevating the populations of medium‐sized native mammal species can improve soil conditions through digging activities, increasing plant regeneration, and also possibly regulating fire behavior (Fleming et al 2014; Johnson et al 2018; Valentine et al 2018). Hence, through cascading effects, maintaining or replacing dingoes may have counterbalancing benefits for livestock production.…”

Bioturbation by a reintroduced digging mammal reduces fuel loads in an urban reserve

“…Animals that regularly dig for food or create burrows and whose soil turnover activities affect the availability of resources for other organisms are often considered ecosystem engineers (Jones et al 1994). Through soil displacement, digging animals can enhance many ecosystem functions (Davidson et al 2012, including increased water infiltration, altered soil nutrients, altered microbial properties and enhanced seedling recruitment (James et al 2010, Eldridge et al 2016, Valentine et al 2018) all of which are likely to influence vegetation and landscape structure (Whitford and Kay 1999). Furthermore, animals that disrupt the surface litter layer through their behaviors have recently been implicated in altering fuel loads (Nugent et al 2014, Hayward et al 2016, Smith et al 2016.…”