Management dependent soil properties of cultivated versus non-cultivated southeastern Coastal Plain ecosystems

Abstract

Management dependent properties describe dynamic soil quality. Comparisons of disturbed to reference sites are not extensive in the southeastern (SE) U.S. due to scarcity of undisturbed land. Objectives of this study were to evaluate land use effects on dynamic soil properties of SE soils, and investigate carbon stocks and soil quality of mature longleaf pine (Pinus palustris Miller) – wiregrass (Aristida stricta Michx.) habitat relative to more intensively cultivated Coastal Plain ecosystems. Sites in Thomas County, GA, representing well-drained, upland soils, were selected in each of three management systems for comparison of near surface soil properties. Land management included mature, multi-aged longleaf pine (LL) forest, slash pine (Pinus elliottii Engelm.) plantation (PP), and conventional row crop (RC) systems. Concentrations of microbial biomass C (0–5 cm) in LL were 69 %> RC, while TOC was 138 % higher in LL relative to RC. Anthropogenic inputs were evident in RC (0–30 cm) based on higher TON (31 % > PP), exchangeable Ca (102 %> LL) and K (433 %> LL), extractable P (1700 %> LL), and base saturation (142 %> LL). Cultivation increased bulk density (?b) (P=0.029) compared to LL. Soil strength (SS) (0–50 cm) in PP was 106 % > LL (P= 0.061). The highest soil infiltration rate (IR) was in LL (42.5 cm hr -1) (P= 0.038), which was 1015 % higher than PP. Saturated hydraulic conductivity (Ksat) was lowest in PP (5.7 cm hr -1). Multivariate analysis indicated 79% of data variability was largely explained by exchangeable bases, C pools, and hydraulic properties, indicating the utility of these properties for a minimum data set of soil quality in similar agroecosystems of the SE U.S. Euclidean clustering of raw data indicated near-surface soil properties were more similar owing to soil management than soil map unit. Soil properties most sensitive to management included particulate organic matter fractions of C and N, potentially mineralizeable N, extractable P and Al, pH, exchangeable bases, IR, ?b, and plant available water. Measurement of these near-surface properties is suggested for evaluating soil change in similar upland soils of the SE U.S. Longleaf ecosystems had better soil quality as indicated by lower ?b and SS, and higher C stocks, IR, Ksat, and plant available water. Longleaf sequestered 13 and 64 % more total organic C than planted pine and row crop sites respectively, indicating the potential of longleaf ecosystems for storing C. In the SE U.S., more intensive cultivation increased soil nutrients and compaction, and reduced water infiltration, C stocks, and inherent variability of soil properties relative to uncultivated longleaf – wiregrass ecosystems.