Tree reduction and debris from mastication of Utah juniper alter the soil climate in sagebrush steppe

Juniper (Juniperus spp.) trees are masticated to reduce canopy fuel loads and the potential for crown fire. We determined the effects of tree reduction and soil cover in the forms of tree mounds and masticated debris on hourly soil water potential and soil temperature at 1-30 cm soil depth. Measurements were made in masticated and untreated areas at three sites in the western Utah portion of the Great Basin. Cumulative seasonal-response variables included wet days (>−1.5 MPa), degree days (>0 °C), and wet degree days (>−1.5 MPa and >0 °C). Masticated areas had 27 more wet days (P < 0.001), 32 more degree days (P = 0.007), and 311 more wet degree days (P < 0.001) than untreated areas across soil depths and seasons. Soil cover had less influence on these soil climate variables than tree reduction. Most importantly, tree reduction increased wet days (P < 0.001) by an average of 44.5 days during the spring and summer growing seasons at depths of 13-30 cm. Managers are advised to masticate trees while desired understory cover remains high in order to minimize water available to weeds.