Rainfall Interception by Singleleaf Pinon and Utah Juniper: Implications for Stand-Level Effective Precipitation

The expansion of pinon and juniper trees into sagebrush steppe and the infilling of histone woodlands has caused a reduction in the covet and density of the under story vegetation Water is the limiting factor in these systems, therefore, quantifying redistribution of water resour ces by tree species is a itical to understanding the dynamics of these formerly sagebrush-dominated rangelands Tree canopy interception may have a significant role in reducing the amount of rainfall that reaches the ground beneath the ti ee, thereby i educing the amount of available soil moisture. We measured canopy interception of rainfall by singleleaf pinon (Pinus monophylla Ton. & Frem ) and Utah juniper (Juniperus osteosperma [Torr.] Little) across a gradient of storm sizes Simulated rainfall was used to quantify interception and effective precipitation during 130 rainfall events ranging in size from 2.2 to 25.9 mm hr(-1) on 19 trees of each species. Effective precipitation was defined as the sum of throughfall and stemflow beneath tree canopies. Canopy interception averaged 44.6% (+/- 27.0%) with no significant difference between the two species. Tree allometries including height, diameter at breast height, stump diameter, canopy area, live crown height, and width were measured and used as predictor variables The best fit predictive model of effective precipitation under canopy was described by stump diameter and gross precipitation (R-2 = 0.744, P < 0.0001). An alternative management model based on canopy area and gross precipitation predicted effective precipitation with similar accuracy (R-2 = 0.741, P< 0.0001) Canopy area can be del ived from various remote sensing techniques, allowing these results to be extrapolated to larger spatial scales to quantify the effect of increasing tree canopy cover on rainfall interception loss and potential implications for the water budget. (C) 2017 The Society for Range Management. Published by Elsevier Inc. All rights reserved.