Impact of soil macrofauna on soil water flow

Last modified by Vanessa Glenn on 2017/01/31 14:50

Executive Summary

Recolonisation of soil by macrofauna (especially ants, termites and earthworms) in rehabilitated open-cut mine sites is inevitable and, in terms of habitat restoration and function, typically of great value. In these highly disturbed landscapes, soil invertebrates play a major role in soil development (macropore configuration, nutrient cycling, bioturbation, etc.) and can influence hydrological processes such as infiltration, seepage, runoff generation and soil erosion. Understanding and quantifying these ecosystem processes is important in rehabilitation design, establishment and subsequent management to ensure progress to the desired end goal, especially in waste cover systems designed to prevent water reaching and transporting underlying hazardous waste materials. However, the soil macrofauna is typically overlooked during hydrological modelling, possibly due to uncertainties on the extent of their influence, which can lead to failure of waste cover systems or rehabilitation activities. We propose that scientific experiments under controlled conditions and field trials on post-mining lands are required to quantify (i) macrofauna–soil structure interactions, (ii) functional dynamics of macrofauna taxa, and (iii) their effects on macrofauna and soil development over time. Such knowledge would provide crucial information for soil water models, which would increase confidence in mine waste cover design recommendations and eventually lead to higher likelihood of rehabilitation success of open-cut mining land.

Background

While the recent review article of Bottinelli et al. (2015) advocates collaboration between soil ecologists and physicists in order to increase understanding of soil–plant water relations, their review is limited to natural and agricultural ecosystems subjected to low or moderate levels of disturbance. As an extension of their work, we propose that interactions between soil fauna and soil structure dynamics are even more critical for severely disturbed ecosystems such as in open-cut mining lands. Therefore, in this short communication article, we (i) consider the impact of macrofauna on the rehabilitation of open-cut mine lands, specifically the effects of ants/termites and mine waste facilities, and (ii) indicate how further research on feedbacks between macrofauna and soil structure may help to reduce uncertainties in the prediction of soil water movement in rehabilitated mine environments, especially toxic waste covers.

Results

Results1.jpg 

Results2.jpg

Outcomes

We suggest two alternative approaches to collect empirical data that can be used to initially quantify these interactions and eventually to reduce uncertainty in modelled hydrological variables such as deep drainage, infiltration, or plant available water. For example, manipulative experiments under controlled conditions are effective means to assess the impact of early colonisers on the soil water dynamics. A soil chamber or column can be used as a formicarium, where an ant nest is transplanted (including queen and workers) and food, water and nesting resources provided. Predefined water regimes could then be administered to simulate rainfall events, while the temporal dynamics of soil water potential and content are monitored across the soil profile. Similarly, these small-scale experiments are suitable for assessing the colonisation rates and environmental conditions (e.g. pH, temperature, humidity, soil water content) required to colonise soils by ants. At a larger investigative scale, field trials in combination with untreated control or reference sites are effective means to assess the impact of macrofauna on soil structure and inter-specific fauna interactions (feedbacks) in relation to soil biodiversity and soil development. In this regard, open cut mining lands may provide ideal environments, because the physical properties of reconstructed soils are fundamentally different (and less complex) from those of degraded but physically intact soils.

References

Arnold, S., and E.R. Williams (2016). Quantification of the inevitable: the influence of soil macrofauna on soil water movement in rehabilitated open-cut mine land., Soil 2, 41-48, doi: 10.5194/soild-2-853-2015

Bottinelli, N., Jouquet, P., Capowiez, Y., Podwojewski, P., Grimaldi, M., and Peng, X. (2015). Why is the influence of soil macrofauna on soil structure only considered by soil ecologists?, Soil Till. Res., 146, 118–124, doi:10.1016/j.still.2014.01.007.

Submitted by: Sven Arnold

    
Contact MRC-wiki
This wiki is licensed under a Creative Commons 4.0 license (CC BY-NC-ND)
XWiki Enterprise 7.4.5 - Documentation