The Influence of Bedrock Type on Forest Growth and Carbon Dynamics in the central Pennsylvanian Appalachian Ridge and Valley: From Tree Rings to Forest Inventories
Open Access
- Author:
- Reed, Warren Paul
- Graduate Program:
- Ecology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- January 22, 2021
- Committee Members:
- Margot Wilkinson Kaye, Dissertation Advisor/Co-Advisor
Margot Wilkinson Kaye, Committee Chair/Co-Chair
Laura P Leites, Committee Member
Jason Philip Kaye, Committee Member
Roman Di Biase, Outside Member
Jason Philip Kaye, Program Head/Chair - Keywords:
- forest ecology
carbon dynamics
oak forest
bedrock
dendrochronology - Abstract:
- Forests function as a major terrestrial carbon sink and provide countless other ecosystem services. Forests of the eastern United States are responsible for a large portion of the carbon storage and accumulation of North America’s forest carbon sink. In the Ridge and Valley Province of the Appalachian mountains much of the upland forested terrain is underlain by shale and sandstone bedrock types. This dissertation investigates the role of shale and sandstone on forest structure and function in the Appalachian Ridge and Valley of Pennsylvania. Chapter 1 of this dissertation provides a general overview of forests in the region, introduces the connection between forests and bedrock and then outlines the content presented here. In Chapter 2, forest carbon storage and accumulation are examined across forested public lands in Pennsylvania’s Ridge and Valley and paired with Geographic Information Systems (GIS) derived landscape metrics to investigate the impact of shale and sandstone bedrock type. Using forest inventory plots, we found that forests on shale are storing and accumulating more carbon in live aboveground forest biomass than those on sandstone. By pairing forest biometric data with spatially specific landscape metrics, including various measures of climate, topography, and soil physical properties, we identified abiotic drivers of live aboveground forest carbon dynamics in relation to lithology. Furthermore, patterns of forest community composition and community dynamics were examined in forests of the most common age classes. Forests on both shale and sandstone are dominated by oaks; however, some common species store and accumulate more carbon on a specific bedrock type. Regionally, these results highlight the potential for underlying bedrock to exert differential influences on forest ecosystem structure and function. Forests are examined at smaller spatial but longer temporal scales in Chapter 3. I use tree cores from chestnut oak and northern red oak to disentangle the impact of bedrock type, species and climate on the growth of dominant and codominant individuals at similar north facing midslope position on shale and sandstone bedrock. Results from this chapter suggest that northern red oak grows at a faster rate than chestnut oak regardless of the underlying substrate. Correlations between seasonal precipitation and oak growth for both species on sandstone bedrock type suggest that these oak species are at least partially limited by the amount of moisture availability on sandstone but not shale. In Chapter 4, forest carbon dynamics are reconstructed from forest plots on north facing midslopes on the two bedrock types. In this chapter I compare forest growth rates from 1975-2015 as well as metrics of resistance and resilience to three moderate–to–severe growing season droughts (1991, 1999 and 2001) that occurred over the period of 1975-2015. Average forest carbon accumulation rates were similar for forests growing on both bedrock types and were resistant and resilient to the droughts experienced over the time period. Results from decades of growth from tree-ring reconstructions are considered in context to more traditional forest inventories on varying slope positions to highlight the large amounts of variability across topographic positions on shale and sandstone bedrock in the region’s complex terrain. Chapter 5 offers reflection on the results presented in this dissertation, highlighting that bedrock type is most important to forest dynamics at the scale of the physiographic province.