A Water Budget Approach to Study the Hydrologic Response of Mountain Meadow Restoration Following Conifer Removal

Abstract:

Mountain meadows are important ecological habitats that have degraded in quality and distribution due to fire suppression and poor land use practices in the Sierra Nevada Mountains. Conifer encroachment in mountain meadows has accelerated and is one of the reasons for the decline of meadow habitat. To date there are few studies which quantify the hydrologic response of meadow restoration due to vegetation or conifer removal. This study is using a before after control intervention (BACI) study design to determine the hydrologic response of restoration to a historic meadow encroached by conifers (study meadow). A water budget approach has been developed to quantify the hydrology of the control and study meadow before and after restoration. Measurements of groundwater depth and soil moisture are currently being taken on the control and study meadows. A total of 14 Odyssey water level capacitance instruments were installed to a 1.5 meter depth and 14 soil moisture instruments were installed to a 30 cm depth using a spatially balanced random sampling approach. Electrical resistivity imaging (ERI) was used to determine soil moisture and depth to groundwater across forest-meadow ecotones present on the meadows. Additionally, ERI was used to extrapolate point measurements of groundwater depth and soil moisture across the study and control areas. The weekly water budget indicates differences between the control meadow and study meadow in the first year prior to conifer removal. The ERI indicated differences in sub surface geology, soil moisture, and groundwater depth both between the control and study meadows and along the forest-meadow ecotones. ERI was demonstrated to improve the spatial extrapolation of soil moisture and groundwater point measurements.