Academic journal article The American Midland Naturalist

Assessing Plant Community Changes over Sixteen Years of Restoration in a Remnant Michigan Tallgrass Prairie

Academic journal article The American Midland Naturalist

Assessing Plant Community Changes over Sixteen Years of Restoration in a Remnant Michigan Tallgrass Prairie

Article excerpt

ABSTRACT.-

Evaluating the progress of ecological restoration projects is critical to improving our understanding of degraded ecosystems and their rehabilitation. In a remnant tallgrass prairie in southeast Michigan that is being managed by periodic dormant-season burns to reduce exotic species and increase native diversity, we tracked plant community changes in seven management units over a period of 16 y to evaluate ecological trajectory in the context of restoration goals. Factors that influenced compositional change from year to year were also assessed. We found that fire frequency, growing season temperature and growing season precipitation were correlated with the magnitude of year-to-year compositional change. Over the 16 y period, most management units decreased sharply in exotic species richness and abundance but did not increase appreciably in native species richness. Also, species evenness and native species abundance increased while total species richness decreased in most units. Over both spatial and temporal scales, the native C^sub 4^ grass Andropogon gerardii (big bluestem) was negatively correlated with species richness, likely because of competitive pressure from A. gerardii. Moreover, the direction of ecological trajectory, which diverged among management unite over time, was related to differences in the abundance of A. gerardii across the prairie. Ultimately, we concluded that although frequent fire was effective at maintaining prairie species and reducing exotic species, using fire as the only restoration tool was not effective at achieving a species-diverse prairie community.

INTRODUCTION

Once one of the most extensive ecosystem types in North America, the tallgrass prairie now remains in about 0.1% of its original range (Samson and Knopf, 1994). Most prairies, because of their rich soils and absence of trees, have been lost to agriculture (Howe, 1994) . Others face serious problems such as overgrazing, fire suppression, woody and exotic species invasion and landscape fragmentation, which have led to a sharp decline of prairie-dependent biodiversity (Risser, 1990; Howe, 1994; Cully et al., 2003; Lett and Knapp, 2003) . Small prairies were once a common feature of the southern Michigan landscape, as part of an extensive matrix of prairies, oak savannas and open oak forests (Chapman and Brewer, 2008). This was the easternmost extension of the Prairie Peninsula, a finger of the Great Plains prairie biome that extended into Southern Michigan, Northwestern Ohio and Southwestern Ontario (Transeau, 1935; Anderson, 1982). As elsewhere in North America, the few prairie remnants left in this region have undergone years of fire suppression and invasion by woody and exotic species (Leach and Givnish, 1996; Chapman and Brewer, 2008) .

Change in plant communities is driven primarily by disturbance, either natural or humaninduced, which alters abiotic conditions and the competitive abilities of species in the community (Tilman, 1982; Pickett et al, 1987) . In tallgrass prairies and other fire-dependent ecosystems, short-term changes in community composition are often influenced by a combination of time since fire and/ or year-to-year variations in climate (Briggs et a?, 1994; Briggs and Knapp, 1995) . Over longer time periods, ecological trajectory can be determined by fire regime, abiotic site conditions, herbivory and/or competitive pressure from dominant species (Anderson, 1982; Abrams et al, 1986; Gibson and Hulbert, 1987; Collins, 2000; Baer«ía¿, 2005).

Modifying the ecological trajectory of an ecosystem is an integral component of ecological restoration projects in nearly all contexts, including prairies (SER, 2004; Clewell and Aronson, 2007) . The outcome of many restoration projects depends on the ecologist's or practitioner's understanding of past changes in the ecosystem as well as their ability to predict how the community may change in the future. Assessing ecological changes over time can be an effective way to evaluate restoration progress and inform adaptive management decisions (Parker et al, 1997; Pastorok et al. …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.