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Disturbance-associated assembly and response rules in blackland prairies.
Weiher, Evan1,2, Schauwecker, Tim2,3, 1 2 3
ABSTRACT- The Mississippi-Alabama blackbelt supports numerous small relict prairies that are in need of restoration due to fire suppression and/or lack of sufficient grazing. In order to address management and restoration of these prairies we conducted a meso-scale experiment in a 30 ha relict prairie-woodland complex. We crossed two types of disturbance (fire, mowing, control) with inoculation with prairie hay (for a total of 6 treatment plots replicated 5 times each) in three vegetation types: upland prairies (dominated by Schizachyrium scoparium with numerous forbs and legumes typical of dry-mesic prairie), eroded areas (eroded and redeposited chalk supporting a low biomass community dominated by Sporobolus vaginiflorus), and cedar removal areas (areas dominated by Juniperus virginiana, with a few core prairie species in the gaps). In the first year after treatment, we investigated patterns of community assembly and response in terms of guild proportionality (sensu Wilson) using a null model. Fifteen significant cases were found after Bonferroni correction. Guild proportionality was skewed toward the more productive uplands and cedar removed areas, but was evenly divided among the disturbance treatments. From this we have defined 4 assembly rules for extant prairie, and 11 disturbance-associated response rules. Assembly rules are usually packaged as the result of competition with overtones of equilibrium, but here short-term transient responses to disturbance result in patterns indistinguishable from those produced by other mechanisms.
KEY WORDS: fire, assembly rules, response rules, null models