Applying Soil Ecological Knowledge to Restore Ecosystem Services

Ecosystem degradation resulting from resource extraction, land-use change, and invasion by exotic species alters numerous functions and services provided by intact and unexploited ecosystems. Ecological restoration is the human-facilitated improvement of a degraded ecosystem and represents an important means to repair or reinstate many natural services in degraded ecosystems ( Table 5.6.1 ). Restoration can be initiated from any point along a continuum of degradation and restoration goals can vary from focused improvements (e.g. amelioration of unsuitable pH, soil stabilization, and re-establishing rare species) to holistic recovery of biological diversity, effi cient nutrient cycling, and complex energy fl ow pathways ( Hobbs & Harris 2001 ). Restorations that aim to re-establish ecosystem structure and function “prior to degradation” may fi nd that historical and extant targets can be diffi cult to defi ne considering the variability of natural systems in space and time ( White & Walker 1997 ) or unrealistic to attain if multiple abiotic and/or biotic factors have been highly modifi ed through human activity ( Hilderbrand et al . 2005 ). Furthermore, restorations are now conducted under novel conditions including invasive species pressure, greater inputs of nutrients through atmospheric deposition, and higher atmospheric CO 2 levels that may restrict the ability to restore systems to some state in the past ( Hobbs & Harris 2001 ; Hobbs et al. 2009 ). Degradation of terrestrial ecosystems is often strongly refl ected as damage to the soil system. It can take tens to thousands of years for some soil properties to develop through the interaction of parent material, climate, topography, and organisms ( Jenny 1941 ). Soil degradation can result in the loss of or alteration to many soil properties and functions. We defi ne soil legacy , as the physical, chemical, and biological attributes and interactions that remain following a signifi cant change to an ecosystem. This defi nition of legacy is aligned with ecological legacy ( White & Jentsch 2004 ), but differs from that which has been used to indicate the residual effects of an abiotic or biotic disturbance on ecosystem properties (e.g. Reinhart & Callaway 2006 ). Thus, soil legacy is the degree to which soil properties (e.g. horizonation, porosity, texture, nutrient storage, organic matter content, aggregation, etc.) and functions (e.g. nutrient supply, infi ltration, etc.) at the onset of restoration refl ect characteristics before the degrading infl uence. The range of variation in ecosystem degradation produces varying soil legacy at the onset of restoration. Heneghan et al. ( 2008 ) proposed that more soil ecological knowledge (defi ned as the integrated understanding of soil physical, chemical, and biological factors and processes in the context of plantsoil feedback) may be required to restore complex interactions following disturbance ( Fig. 5.6.1 ). This chapter presents the utility of soil ecological knowledge to the practice of ecological restoration along a continuum of ecosystem degradation that results in varying legacy of the plant and/or soil system. Mineral resource extraction can result in severe ecosystem degradation that leaves little to no soil legacy, initially. Restoration of these highly degraded lands