Subalpine Wetlands : characterization, environmental drivers, and response to human perturbation and restoration

Abstract

The subalpine region throughout the western US is increasingly pressured by land use changes. Consequences of these changes often involve major alteration to the original function of the landscape, particularly concerning wetland and riparian areas. In southwest Montana, large developments have recently been created or expanded in the subalpine environment. Wetlands in these regions bear a particularly unique structure, and often are influenced by the effects of development. The alteration to structure can result in disturbance to the original hydrological, ecological, and biogeochemical functions of wetlands. Restoration efforts attempt to mitigate for development influences, but the monitoring and success criteria do not wholly address the functional attributes of these features. At the same time, little is known about the structure of undisturbed subalpine wetlands and how environmental drivers influence the undisturbed structure and hydrological, ecological, and biogeochemical functions. Knowledge of these natural processes is necessary to ensure appropriate management decisions and future restoration success. This study examines small subalpine wetlands in an elevation range of 2256-2316 m located in southwest Montana. Study sites include two wetland types, in undisturbed and restored conditions. This research examines physical, chemical, biological, and hydrological attributes of wetlands in varying conditions, to define and compare wetland characteristics, determine primary environmental drivers of wetland ecological and biogeochemical functions, and compare response to human perturbation. Comparisons of our data indicate significant differences in all categories of parameters, and include metrics of biodiversity, primary productivity, hydrologic regime, and physical and chemical properties of the soil. Several environmental drivers are identified, with the primary driver of vegetation and redox response variables being depth to water and persistence of saturated conditions. The depressional wetland type is characterized by a distinct hydrologic regime, with these conditions being significantly related to a greater number of ecological and biogeochemical functions than the linear wetland type. Restoration data indicate that the restoration methods employed are sufficient in establishing the primary wetland characteristics used in wetland definition. However, the trajectory of restored wetlands indicates that long term recovery may result in wetlands exhibiting different structural and functional attributes than intended.