Showing papers by "Valerie T. Eviner published in 2012"

Integrating microbial ecology into ecosystem models: challenges and priorities

Abstract: Microbial communities can potentially mediate feedbacks between global change and ecosystem function, owing to their sensitivity to environmental change and their control over critical biogeochemical processes. Numerous ecosystem models have been developed to predict global change effects, but most do not consider microbial mechanisms in detail. In this idea paper, we examine the extent to which incorporation of microbial ecology into ecosystem models improves predictions of carbon (C) dynamics under warming, changes in precipitation regime, and anthropogenic nitrogen (N) enrichment. We focus on three cases in which this approach might be especially valuable: temporal dynamics in microbial responses to environmental change, variation in ecological function within microbial communities, and N effects on microbial activity. Four microbially-based models have addressed these scenarios. In each case, predictions of the microbial-based models differ—sometimes substantially—from comparable conventional models. However, validation and parameterization of model performance is challenging. We recommend that the development of microbial-based models must occur in conjunction with the development of theoretical frameworks that predict the temporal responses of microbial communities, the phylogenetic distribution of microbial functions, and the response of microbes to N enrichment.

Measuring the Effects of Invasive Plants on Ecosystem Services: Challenges and Prospects

Abstract: Plant invasions can have large effects on ecosystem services. Some plant invaders were introduced specifically to restore key services to ecosystems, and other invaders are having unintended, detrimental effects on services, such as the quantity and quality of water delivered, flood control, erosion control, and food production. Many ecosystem services are difficult to measure directly, and although there are extensive studies on plant invaders and ecosystem processes, a number of challenges prevent us from confidently extrapolating those processes as proxies for services. To extrapolate local, short-term measures of processes to ecosystem services, we must: (1) determine which processes are the key contributors to a service, (2) assess how multiple processes interact to provide a given service, (3) determine how vegetation types and species affect those processes, and (4) explicitly assess how ecosystem services and their controls vary over space and time, including reliance of ecosystem service...

The effects of plant-soil feedbacks on invasive plants: mechanisms and potential management options.

Abstract: Th ere are countless examples of management projects that have attempted to decrease or eradicate invasive species at a site, only to have them rapidly recolonize within a few years. While this is often attributed to reinvasion through propagules remaining at the site, or high propagule pressure from the surrounding landscape (Leung et al., 2004; Lockwood et al., 2005), this also may be due to invasive species changing site conditions to favor conspecifi cs over native species. Many studies have documented that invasive plants can impact numerous soil properties and processes (Leffl er and Ryel, Chapter 4, this volume; Ehrenfeld, 2010), and that invader impacts on soil can infl uence competitive dynamics between plant species, often favoring the invaders (Callaway and Aschehoug, 2000; Reinhardt and Callaway, 2006; Batten et al., 2008; Kulmatiski et al., 2008; reviewed in Eviner et al., 2010). Some of the eff ects of invasive species on soils can persist after the invader has been removed, making the system more susceptible to reinvasion (reviewed in Eviner and Hawkes, 2008; Kulmatiski and Beard, 2011). In these cases, restoration eff orts must be focused not only on removing invasive species, but also counteracting their eff ects on soil characteristics and processes (Heneghan et al., 2008; Harris, 2009; Eviner et al., 2010). In this chapter, we explore the mechanisms driving plant–soil feedbacks in invaded systems, and potential management tools to alter these feedbacks to be more benefi cial to natives over invasive species.