Presentation on theme: "Patterns and processes of recovery in and around an Indiana limestone quarry Vanessa L. Artman, Dana A. Dudle Bryan Helm, David Pope, and Aaron Randolph."— Presentation transcript:
Patterns and processes of recovery in and around an Indiana limestone quarry Vanessa L. Artman, Dana A. Dudle Bryan Helm, David Pope, and Aaron Randolph Department of Biology, DePauw University, Greencastle IN 46135 Study Sites We chose three forested sites to collect baseline data on bird and plant communities: the Arboretum (ARB), Quarry South (QS), and Quarry Hillside (QH) (Figure 1). Forest habitat at the sites has been relatively undisturbed in recent history. However, habitat quality is limited by extensive forest fragmentation, with the surrounding landscape comprised of a mix of rural and suburban development. Adjacent land is used for athletic fields, four-wheel-drive roads, powerline rights-of-way, open meadows, and an abandoned limestone quarry. Methods We measured vegetation and habitat characteristics at ten randomly located plots in each site following BBIRD protocol. Within a 5-m- radius subplot, we estimated leaf litter depth, estimated percent cover of understory vegetation ( 8.0 cm dbh) by species and size class. We censused bird populations using the territory-mapping method. Each site was surveyed four times between mid-May and the end of June, between the hours of 5 and 10 a.m. During each survey, we recorded locations of singing and calling birds. Clusters of observations over multiple visits were used to identify territories, and then to estimate population sizes. We searched for and monitored nests at the sites following BBIRD protocol. Nests were monitored every 3 to 5 days to determine their fate. We estimated daily nest survival rates using the Mayfield method. Results The three forest habitats differ significantly in forest structure, vegetation composition, and breeding bird communities. These differences are surprising given the relative proximity of the sites. Furthermore, the forest composition of several of the sites is unusual for eastern deciduous forests. The history of human activity at the sites may provide a partial explanation for these differences. Introduction In October 2003, DePauw University acquired a 192-ha “nature park”, intended for the various purposes of habitat conservation, education, and recreation. The land comprises several habitats, including deciduous forest, old fields, wetlands, a river, and several freshwater ponds, but the central feature of the land is a large limestone quarry that was abandoned 30 years ago. Each of these habitats has been significantly affected by human activity, through logging, mining, construction and some areas are highly disturbed. Some central questions of restoration ecology – Is the ecosystem recovering on its own? Or is human intervention appropriate and/or necessary to promote recovery? If intervention is necessary, what kind? – form the core of our discussions about how DePauw should use and manage this resource. Here, we present our baseline data describing the present state of breeding bird and forest tree communities at several sites in the park, and our preliminary plans for further research and management at the site. Figure 1. Study areas at DePauw University Arboretum Quarry Hillside Quarry South Figure 2. Forest tree composition at the three study sites. Forest composition at the ARB is typical of eastern deciduous forests. At QH and QS, forests have unusually high proportions of elm and cherry, and lack oaks and hickory, signature species of this region. Figure 3. Forest understory composition at the three study sites. Native shrubs dominate the understory at the ARB but the regeneration layer lacks oaks and hickories. An invasive shrub forms the bulk of the understory at the quarry sites, but the dense shrub cover provides nesting habitat for songbirds such as Indigo Buntings and Northern Cardinals. Figure 3. Size distribution of trees and cover of leaf litter at three sites. Different letters above the bars indicate significant differences between sites (1-way ANOVA with Tukey tests, p<0.05). Forest habitat is older at the ARB than at the quarry sites, and has more extensive litter; however, leaf litter at all three sites is less extensive than in typical eastern deciduous forests. Leaf litter decomposition rates may vary at the sites, which would impact communities of soil invertebrates, and thus, birds. Table 1. Number of bird territories at each site, 2004. All three sites support a variety of songbird species, but some differences in breeding populations across sites, despite their proximity, suggest intriguing avenues for future work on a subset of these species. Table 2. Nesting success for two species of forest birds at the sites Discussion Cerulean warblers occurred only at the QS site and not the other sites (Table 1). Widespread population declines of Cerulean Warblers have been occurred throughout the region, and this species is being considered for federal protection. Cerulean Warblers are patchily distributed within suitable habitat throughout the region, and their presence at QS attests to the importance of maintaining this habitat within its existing condition. Indigo Buntings were also common at the QS site, nesting in the dense shrub cover. This species usually occurs in early-successional habitats such as open meadows or edge habitats, but its presence in closed- canopy presents interesting questions about fitness consequences of habitat selection in different environments. Acadian Flycatchers occur only in forest-interior habitat. They were common at all three sites (Table 1) with fairly high levels of breeding productivity (Table 2). Their nests tend to be in predictable and accessible locations, usually situated at the ends of long branches extending over stream drainages. Wood Thrushes were common only at QH and were almost absent from the other sites (Table 1). The differences in forest structure and composition between the sites don’t necessarily explain these results because Wood Thrushes are usually common and uniformly distributed throughout suitable habitat, but their unusual spatial distribution at the sites merits closer attention. Cerulean Warbler Acadian Flycatcher Wood ThrushIndigo Bunting Implications The forest at QS, QH, and ARB provides valuable habitat for a variety of songbirds, several of which are of significant conservation concern. We recommend that forest management practices proceed with caution throughout the natural areas to maintain the existing integrity of the communities. The sites provide an array of opportunities for research and coursework in ecology. We are excited about the opportunity for multiple long-term experiments at common sites, using an interdisciplinary approach to address questions such as: What abiotic and biotic factors contribute to the unusual forest composition at the sites? How does food availability differ, given variation in distribution of masting trees (oaks, hickories, walnuts) between the sites? How do we minimize spread of invasive plant species without reducing available songbird habitat? What is the recent history of the sites and how has human land use affected the biological communities? Acknowledgments We thank DePauw University for funding this research. This research would not have been possible without the foresight of Hansen Aggregates and the many hours of dedicated fieldwork by our student co-authors.