Effects of digging by a native and introduced ecosystem engineer on soil physical and chemical properties in temperate grassy woodland.

Philip S Barton,John Gillen,Maldwyn J Evans,Catherine E Ross,Sue Mcintyre,Saul A Cunningham,Nicola T Munro,Adrian D Manning,Ben C.T Macdonald

doi:10.7717/peerj.7506

Abstract

Temperate grasslands and woodlands are the focus of extensive restoration efforts worldwide. Reintroduction of locally extinct soil-foraging and burrowing animals has been suggested as a means to restore soil function in these ecosystems. Yet little is known about the physical and chemical effects of digging on soil over time and how these effects differ between species of digging animal, vegetation types or ecosystems. We compared foraging pits of a native reintroduced marsupial, the eastern bettong (Bettongia gaimardi) and that of the exotic European rabbit (Oryctolagus cuniculus). We simulated pits of these animals and measured pit dimensions and soil chemical properties over a period of 2 years. We showed that bettong and rabbit pits differed in their morphology and longevity, and that pits had a strong moderating effect on soil surface temperatures. Over 75% of the simulated pits were still visible after 2 years, and bettong pits infilled faster than rabbit pits. Bettong pits reduced diurnal temperature range by up to 25 °C compared to the soil surface. We did not find any effects of digging on soil chemistry that were consistent across vegetation types, between bettong and rabbit pits, and with time since digging, which is contrary to studies conducted in arid biomes. Our findings show that animal foraging pits in temperate ecosystems cause physical alteration of the soil surface and microclimatic conditions rather than nutrient changes often observed in arid areas.

Highlights

Temperate grasslands and woodlands are among the most threatened biomes worldwide due to widespread clearing and degradation from land use changes and inappropriate management (Hoekstra et al, 2004)
There was a significant interaction between pit age and species (p < 0.001) for both depth/radius and volume, indicating that the difference between the bettong and rabbit pits changed over time
We demonstrated that while bettong and rabbit pits differed in their physical effects, such as the micro-topography of the soil surface and the temperatures in the pit, they did not have a clear effect on soil chemistry

Summary

Introduction

Temperate grasslands and woodlands are among the most threatened biomes worldwide due to widespread clearing and degradation from land use changes and inappropriate management (Hoekstra et al, 2004). Loss of species has both accompanied and contributed to this degradation, including soil-foraging and burrowing animals that play a role in soil turnover. Some of these animals are considered to be ‘ecosystem engineers’. Most knowledge of the role of digging animals in ecosystems has been developed from arid environments (Coggan, Hayward & Gibb, 2018). This leaves little understanding of their role in many other ecosystems, and their potential use for ecosystem restoration (Byers et al, 2006; Manning, Eldridge & Jones, 2015)

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Conclusion