Reducing erosion, ameliorating stress, resisting invasion: Roles for soil organisms in ecological restoration

Background/Question/Methods

Historically, ecological restoration has been focused on applied vascular plant succession. In dryland ecosystems such as those of the Colorado Plateau, the influence of plants upon the larger ecosystem is spatially discontinuous and represents only a portion of the system requiring ameliorative efforts. We assert that, in drylands where plant cover is limited, soil communities and processes are the foundation of terrestrial ecosystems and thus should be a focal point in ecological restoration activities. In this synthesis of our observational and experimental work in semi-arid regions of the USA, we pose the questions: (1) which roles might soil biota play in ecological restoration? (2) which groups of soil biota will play them? and (3) how might these different biota be manipulated in an ecological restoration context?

Results/Conclusions

We highlight three pathways by which soil organisms might promote ecosystem function and resilience and show promise as restoration materials or tools. 1. To be resilient in the face of climate change, an ecosystem must be able to retain resources such as soil fertility and moisture. Erodibility and hydrology are very strongly influenced by the characteristics of biological soil crusts (biocrusts) on the Colorado Plateau. These communities can and have been restored; improvement of culture, production and delivery techniques for biocrust cyanobacteria and mosses are key to their adaptation as future restoration tools. 2. Arbuscular mycorrhizal fungi (AMF) are plant root symbionts, enhancing nutrient and water status of most Colorado Plateau plants. Co-adaptation of plants and AMF communities may also be a mechanism by which plants adapt to their local soil and climatic environment. As climate change introduces novel environments, assisted migration of both plant ecotypes and their co-adapted fungi may become important. Management practices that enhance native AMF communities have the potential to promote soil stability, enhance native plant establishment and resist invasion of certain non-native plant species. 3. Invasion by nitrophilic exotic annual grasses such as Bromus tectorum is a common syndrome that can result in altered fire cycles and reduced native plant performance. Addition of carbon substrates stimulates soil bacterial and fungal communities, immobilizing nitrogen and removing a competitive advantage from B. tectorum. These three examples illustrate ways in which a plant and soil focused approach to ecological restoration may ultimately improve on-the-ground success and assist restoration practitioners in responding to future uncertainties associated with climate change.