Lithological Controls on Soil Properties of Temperate Forest Ecosystems in Central Pennsylvania
Open Access
- Author:
- Hill, Lillian Z
- Graduate Program:
- Ecology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- November 11, 2016
- Committee Members:
- Jason Philip Kaye, Thesis Advisor/Co-Advisor
Roman Alexander Dibiase, Committee Member
David Eissenstat, Committee Member
Patrick Joseph Drohan, Committee Member - Keywords:
- Lithology
Nutrient Cycles
Critical Zone
Soil Gas
Soil Properties
Temperate Forest - Abstract:
- Shale and sandstone are the most common lithologies of the forested ridges throughout the Appalachian Mountains. The overall goal of this thesis was to determine whether these two rock types impart distinct biogeochemical properties to soils and plants. The effects of rock type (lithology) on soil gas concentration, nutrient concentration and nutrient limitation were studied in the Ridge and Valley province of central Pennsylvania. To increase understanding of lithological controls on soil gases (Chapter 1), we monitored the depth distribution of soil CO2 and O2 concentrations in central Pennsylvania in two watersheds on different lithologies. We deployed gas monitoring instrumentation on two catena transects that included four topographical positions, one located on sandstone and the other on shale. As expected, with increasing soil depth O2 concentrations decreased while pCO2 increased. CO2 and O2 concentrations varied more with topographical position than with lithology, as the valley floor positions in both catenas had the highest pCO2 for a given depth. Both manual sampling from gas access tubes throughout the soil profile and continuous sampling by buried sensors documented these patterns. Adjacent forests underlain by shale and sandstone lithologies are prevalent throughout the Appalachian Mountains and may have differences in nutrient concentrations and limitation due to the lithologies and subsequent weathering. Nutrient limitation in temperate forest ecosystems often regulates plant productivity, and contemporary conceptual models emphasize nitrogen (N) as the main limiting nutrient. However, with increased global fossil fuel emissions and subsequent deposition of nitrogen, this assumption may not hold. In ecosystems that are receiving high N inputs, the availability of phosphorus (P) and cations, such as calcium (Ca) and magnesium (Mg), may become a key determinant of plant growth. In many conceptual models, plant-soil interactions are depicted; however, lithology is often not incorporated. We use five sites located on shale lithology and five of sandstone lithology to investigate nutrient pools in the mineral soil and the foliage of two tree species (Chapter 2). Our results show that shale and sandstone weather to form different nutrient availability signatures, with higher availability of most rock-derived nutrients on shale. However, extractable P and inorganic N concentrations were higher in the sandstone-derived soils. Furthermore, trees grown on the sandstone sites had higher foliar P concentrations and lower P resorption at senescence. These results suggest that relative to shale, soils developing on sandstone ridges have more P available in soil and less P limitation to plants, despite lower P concentrations in the underlying rock. We hypothesize that higher P availability on sandstone ridges is not from in situ weathering of sandstone, but rather, a possible result of periglacial loess deposits. In conclusion, our studies showed that 1) lower landscape positions have more soil CO2 and could have higher carbonic acid weathering than other landscape positions and 2) sandstone-derived soils have greater concentrations of extractable N and P, which may be the result of higher deposition inputs (in the case of N) or historical loess (in the case of P), than the cation rich shale.