Red spruce ecological sites, ecological states, and restoration pathways quantified through soil organic carbon

Abstract

Tools used by agencies and organizations like the Forest Service (FS), the Natural Resource Conservation Service (NRCS), the Nature Conservancy (TNC), and the Central Appalachian Spruce Restoration Initiative (CASRI) to help guide red spruce (Picea rubens) ecosystem restoration within Central Appalachia could better address outcomes from management practices implemented in terms of soil organic carbon (SOC) stock changes. These high-elevation landscapes have a natural capacity to produce diverse ecosystem services that affect humans, animals, and plants alike. Ecological site descriptions (ESD) are an important tool used to restore impacted landscapes and provide detailed management prescriptions specific to red spruce ecological sites (ES) and ecological states occurring in the Monongahela National Forest (MNF). Previous studies have evaluated ESD utility for identifying ecologic communities and restoration pathways primarily in western rangelands, but none have focused on Central Appalachian landscapes. Research associated with SOC stocks and forest ESD is minimal. Studies have analyzed how SOC can benefit ecosystem services, yet none seek to compare SOC stocks across multiple ecological states to address both restoration pathways and management outcomes that could potentially increase SOC sequestration capacity while restoring impaired ecosystem services. 120 individual plots within the dual extent of the Spodic Shale Upland Conifer Forest (SSUCF) and Spodic Intergrade Shale Upland Hardwood and Conifer Forest (SISUHCF) ES were analyzed using soil profiles and ecosystem descriptions sampled between 2009 and 2021. Soil samples were analyzed using dry combustion to determine SOC percent weight and further used to calculate the SOC stock to 100 cm in depth where applicable. Here, mean SOC stock, SOC stock variance, and the relationship between percent conifer canopy cover and SOC stocks of ecological states of both ES were compared and discussed. Analyses showed differences between ES total SOC (TSOC) stock (p < 0.0001), O horizon SOC (OSOC) stock (p < 0.0001), and spodic horizon SOC (SPSOC) stocks (p = 0.001), while mineral SOC (MSOC) showed no difference (p = .628) (Table 4.1). At the ecological state level, there were only two significant differences when examining TSOC (p = 0.038) and OSOC (p = 0.001) stocks (Table 4.2). The SSUCF demonstrated higher variance than the SISUHCF in TSOC stock (p-value < 0.0001) and OSOC stock (Table 4.3, p-value < 0.0001). Conversely, there was no significant difference between ES when comparing MSOC stock variance (p-value = 0.971) and SPSOC stock variance (p-value = 0.126). Regression analysis used a fixed model and showed