Spatial Behavior of Phosphorus and Nitrogen in a Subtropical Wetland

Complex spatial patterns of biogeochemical properties such as soils are generated in wetlands as a result of internal cycling of nutrients, natural forcing functions (e.g., hydrologic flow paths), and anthropogenic impacts (e.g., nutrient inputs). To preserve ecosystem health and the functions of a wetland ecosystem, it is critical to maintain a soil nutrient status that resembles natural reference conditions and to preserve biogeochemical variability. We investigated the spatial behavior of total P (TP) and total N (TN) in a subtropical wetland in Florida that historically has been impacted by nutrient influx. Our specific objectives were to: (i) assess the spatial autocorrelation structure and spatial variability of TP and TN across a subtropical wetland given a dense observation set (n = 266); and (ii) assess the information loss associated with underlying spatial autocorrelations and spatial variability in TP and TN under various scenarios of reduced sampling densities (n = 175-50). Both properties showed contrasting spatial metrics with long spatial autocorrelations for TP (7240 m) and much shorter ones for TN (1007 m). The contrasting spatial metrics of TP and TN along trajectories of sparser observation sets translated into different responses in spatial patterns that disintegrated dramatically for TN and less so for TP when compared with the reference set (n = 266). In this subtropical wetland, a sampling set of n > 75 (0.036 samples ha-1) for TP and n > 125 (0.0260 samples ha-1) for TN yielded satisfactory results to resemble spatial patterns of the reference set. This study provided insight into the spatial behavior and patterns of two important soil nutrients in wetlands.