Rocks Matter to the Roots
How Bedrock Influences Forest Carbon Storage and What It Means for Conservation in Tennessee
A 2020 study published in Forest Ecology and Management highlights a surprising factor in the battle against climate change: the type of bedrock beneath forests plays a crucial role in how much carbon they store and how quickly they absorb it. The findings from the article, “Bedrock Type Drives Forest Carbon Storage and Uptake across the Mid-Atlantic Appalachian Ridge and Valley, U.S.A.,” could influence conservation priorities and how we approach forest management in Tennessee and beyond.
Key Findings from the Study
The research, conducted across the mid-Atlantic Appalachian Ridge and Valley region, shows that forests growing on different types of bedrock store and absorb carbon at different rates:
- Forests on shale bedrock store 25% more carbon than those on sandstone.
- Forests on shale absorb carbon 55% faster than those on sandstone.
This means that not all forests are equal when it comes to carbon sequestration—the process by which trees absorb carbon dioxide from the atmosphere and store it, helping to reduce greenhouse gases.
What This Means for Tennessee’s Forests
While the study focuses on an area to the north, much of the Appalachian Ridge and Valley ecoregion shares similar characteristics, such as soil composition and annual rainfall. Warren Reed, a co-author of the study, explained in a Penn State press release that these findings should apply across much of the Appalachian Mountains, stretching from southern New York to northern Georgia.
This suggests that forests in Tennessee with shale bedrock may also store and absorb more carbon than those on sandstone, making them critical areas for conservation if we aim to maximize the climate benefits of our forests.
Bedrock and Resilience in a Changing Climate
As the climate warms and precipitation patterns shift, the type of bedrock beneath forests may also play a role in their resilience. Margot Kaye, another co-author of the study, noted that forests growing on shale often support a greater diversity of tree species, which can make them more resilient to environmental changes. These forests may grow faster and respond better to changes in climate, making them priority areas for conservation efforts focused on carbon sequestration.
On the other hand, forests on sandstone, which may store less carbon, could be better suited for other purposes, such as wildlife habitat or outdoor recreation.
How The Land Trust for Tennessee Can Apply These Insights
At The Land Trust for Tennessee, we’re committed to protecting forests for their ecological, recreational, and climate benefits. The insights from this study could help us prioritize areas where forests on shale bedrock offer a significant opportunity for carbon storage, enhancing our efforts to conserve land in a changing climate.
As we continue our efforts across the state, this scientific research in geology and carbon storage reminds us that Tennessee’s landscapes are unique and powerful. By considering the bedrock beneath the forests we conserve, we can better protect our environment for future generations.
Learn more about our efforts to conserve Tennessee’s forests and how you can support this important work.
See full citations and study abstract below.
Primary study source:
Warren P. Reed, Margot W. Kaye, Bedrock type drives forest carbon storage and uptake across the mid-Atlantic Appalachian Ridge and Valley, U.S.A., Forest Ecology and Management, Volume 460, 2020, 117881, ISSN 0378-1127, https://doi.org/10.1016/j.foreco.2020.117881.
(https://www.sciencedirect.com/science/article/pii/S0378112719319693)
Abstract: Lithology influences forest carbon storage and productivity yet is often overlooked for forests of the eastern United States, a large and important carbon sink. This research explores the influence of two common lithologies of the Ridge and Valley physiographic province in the Appalachian Mountains, shales and sandstones, on live aboveground carbon storage, carbon uptake, forest community composition and their interrelationships. We couple forest inventory data from 565 plots from Pennsylvania state agencies with a suite of GIS derived landscape metrics including measures of climate, topography and soil physical properties to identify biotic and abiotic drivers of live forest carbon dynamics in relation to lithology. Forests growing on shale bedrock store more live aboveground carbon compared to forests on sandstone when controlling for stand age, which ranged from 20 to 200 years. Furthermore, forests in the dominant ages (81–120 years) store more live aboveground carbon (108.1 Mg/ha vs. 86.5 Mg/ha) and uptake live aboveground carbon at a faster rate (1.32 Mg/ha/yr vs 0.85 Mg/ha/yr) on shale compared to sandstone respectively. Overall forest communities on both lithologies are dominated by oaks (Quercus spp.), however northern red oak (Q. rubra) is more dominant at shale sites compared to chestnut oak (Q. prinus), which dominates on sandstone. Most species in the forest tend to be more productive on shale, which may account for differences in carbon pools and fluxes across the landscape. Tree species richness is higher in sites on shale bedrock, but biodiversity-productivity relationships within lithologic classifications fail to account for differences in forest productivity. Modeled live aboveground carbon storage points to topography (elevation and aspect) and soil physical properties (% clay and available water capacity) as important influences on forest productivity that related back to lithology. Incorporating lithology into forest management strategies that are focused on a variety of ecosystem services can aid future site selection, and we demonstrate that forests on shale bedrock grow faster, store more carbon and have higher species diversity. The results presented here highlight the potential for underlying bedrock to exert differential influences on forest ecosystem structure and function across a region.
Primary spatial data sources:
LANDFIRE, 2022, Existing Vegetation Type Layer, LANDFIRE 2.0.0, U.S. Department of the Interior, Geological Survey, and U.S. Department of Agriculture. Accessed 12 February 2024 at https://www.landfire.gov/data-downloads/US_230/LF2022_EVT_230_CONUS.zip.
Horton, J.D., 2017, The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States (ver. 1.1, August 2017): U.S. Geological Survey data release, https://doi.org/10.5066/F7WH2N65.
Additional map data:
USGS PAD-US v4.0, TDEC, LTTN, US Census Bureau TIGER, Esri Living Atlas: Hydrology (USGS National Hydrography Dataset Plus High Resolution), Topography (Terrain: Hillshade), Reference Layers (OpenStreetMap)