Spatial variability of thorughfall under three sage brush (Artemesia tridentata)

Abstract:

Rainfall interception loss (I) has been poorly studied in semi-arid systems. Past work suggests that I can range from less than 3 % to 27% of gross precipitation in semi-arid systems. For many years the hydrologic flow paths in vegetation canopies has been treated as a black box. For example, when researching canopy interception loss, researchers typically monitored total rainfall above and below the vegetation canopy. More recently, the spatial pattern of throughfall (TF) and stemflow (SF) have been of interest. Past research on the spatial patterning of TF under forest canopies has documented that persistent patterns of TF can occur. These patterns create “hot spots” of throughfall. Like trees, persistent spatial patterns of TF may exist under shrubs. To test the changes in the throughfall depth and distribution with changing local meteorological conditions, we monitored throughfall and stemflow under three sagebrush shrubs (n=64 throughfall gauges for each shrub). Rainfall interception loss under the shrubs ranged from 31 to 100% for storm events ranging from 0.4 to 52 mm in size. Stemflow only occurred during larger storm events (>10 mm). Stemflow is likely limited because the tortuous nature of the canopy architecture that readily sheds water from the canopy. The canopy architecture also resulted in temporally and spatially persistent drip points. For storms sufficient to saturate the canopy, temporally and spatially persistent drip points generated water inputs that were 1.5 time greater than gross precipitation.