Resistance and resilience are strong determinants of the stability of ecosystem processes (Lehman and Tilman, 2000) and, consequently, of the sustainable delivery of provisioning and regulatory ecosystem services, for example primary production, water filtering, carbon storage, and pest control (MEA, 2005). For soils, it is well known that the stability depends on the structure of the soil food web (De Ruiter et al., 1995; Neutel et al., 2007), as well as on soil physical and chemical conditions (Griffiths et al., 2008). Resistance and stability of soils are clearly related to their biodiversity (Wardle, 2002), but it is not necessarily biodiversity per se that does the job. For example, some ecosystem services such as pest control and plant biomass production depend on the presence of low-abundance components of soil biodiversity (Hol et al., 2010), whereas nutrient cycling depends more on the dominant components of soil biodiversity (Wertz et al., 2006). What is currently lacking are clear sets of indicators that enable cost-efficient monitoring in a standardised way at continental scale covering a wide variety of environmental conditions that typify Europe. Moreover, there is a strong need to relate the outcome of monitoring to the economic consequences of data obtained from monitoring programmes. There are many sorts of indices and indicators that relate soil biodiversity to specific ecosystem services or properties, such as the catabolic diversity of soil microbes (Degens et al., 2001), soil microbial biomass (Orwin and Wardle, 2004), and nematode community structure (Bongers, 1990). However, these indicators have not yet been compared systematically for a range of environmental conditions and a variety of ecosystem services and they have not yet been considered from the perspective of soil biota being organised as soil food webs. Moreover, their cost effectiveness has received little attention and monitoring programs within the European Union are not well connected. Finally, none of the current monitoring programs and indicator systems is linking the monitoring output data to the economic value of (soil) biodiversity. In order to develop, validate and value soil monitoring, a variety of environments need to be considered, including ecosystems that are kept in a high state of disturbance, such as agricultural soils that are constantly tilled and fertilised, and grassland soils that are far less disturbed and contain more organic matter and have highly developed soil food webs. These soils are present on the project LTOs. In addition, it is essential to determine the extent to which soil biodiversity can be restored, the cost of restoration and the value of such soil biodiversity restoration programs for resilience and stability of provisioning and regulatory ecosystem services.
Griffiths, B.S, Philippot, L. FEMS Microbiology Reviews. DOI: 10.1111/j.1574-6976.2012.00343. Read the article
Abstract
Soil is increasingly under environmental pressures that alter its capacity to fulfil essential ecosystem services. To maintain these crucial soil functions, it is important to know how soil microorganisms respond to disturbance or environmental change. Here, we summarize the recent progress in understanding the resistance and resilience (stability) of soil microbial communities and discuss the underlying mechanisms of soil biological stability together with the factors affecting it. Biological stability is not solely owing to the structure or diversity of the microbial community but is linked to a range of other vegetation and soil properties including aggregation and substrate quality. We suggest that resistance and resilience are governed by soil physico-chemical structure through its effect on microbial community composition and physiology, but that there is no general response to disturbance because stability is particular to the disturbance and soil history. Soil stability results from a combination of biotic and abiotic soil characteristics and so could provide a quantitative measure of soil health that can be translated into practice.
Tardy, V, Mathieu, O., Leveque, J., Terrat, S., Chabbi, A., Lemanceau, P., Ranjard, L., Maron, P.-A. 2014. Env. Microbiol. Peports. Published online. DOI: 10.1111/1758-2229.12126. Read the article
Summary
Despite the central role of microbes in soil processes, empirical evidence concerning the effect of their diversity on soil stability remains controversial. Here, we addressed the ecological insurance hypothesis by examining the stability of microbial communities along a gradient of soil microbial diversity in response to mercury pollution and heat stress. Diversity was manipulated by dilution extinction approach. Structural and functional stabilities of microbial communities were assessed from patterns of genetic structure and soil respiration after the stress. Dilution led to the establishment of a consistent diversity gradient, as revealed by 454 sequencing of ribosomal genes. Diversity stability was enhanced in species-rich communities whatever the stress whereas functional stability was improved with increasing diversity after heat stress, but not after mercury pollution. This discrepancy implies that the relevance of ecological insurance for soil microbial communities might depend on the type of stress. Our results also suggest that the significance of microbial diversity for soil functional stability might increase with available soil resources. This could have strong repercussions in the current ‘global changes’ context because it suggests that the combined increased frequencies of extreme climatic events, nutrient loading and biotic exploitation may amplify the functional consequences of diversity decrease.