Lithology influences forest carbon storage and productivity over complex terrain. The role of bedrock geology on these processes has been previously overlooked in forests of the eastern United States, despite its potential influence on this large and important carbon sink. This research explores the impact 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. In this study, we couple forest inventory data from Pennsylvania state agencies with a suite of GIS derived landscape metrics including measures of climate and soil physical properties to understand biotic and abiotic drivers of live forest carbon dynamics in relation to lithology.
Results/Conclusions
Data from 570 forest plots spanning 20 – 200 years in age demonstrate that forests growing above shale bedrock are storing more live aboveground carbon compared to forests above sandstone when controlling for stand age. Live aboveground carbon in stands that represent the majority of the forest landscape (65% of stands are 80-120 years old) store ~26% more carbon on shale compared to sandstone. Plots from the most common age classes with repeated inventories accumulated carbon at a rate of 1.32 and 0.85 Mg/ha/yr on shale and sandstone, respectively, illuminating an annual rate 55% higher on average per year on shale lithology. Overall forest communities on both lithologies of interest are dominated by oaks (Quercus spp.), however northern red oak (Quercus rubra) is more dominant at shale sites compared to chestnut oak (Quercus prinus) on sandstone. Tree species richness was higher in sites associated with shale bedrock, but biodiversity productivity relationships within lithologic classifications failed to account for differences in forest productivity. Linear and machine learning models of live aboveground carbon storage are considered to understand the relative influence of soil and topographic variables across the landscape. These results highlight that lithification processes over hundreds of millions of years can contribute to modern day forests and their ability to uptake and store atmospheric carbon.