Runoff and erosion in a pinon-juniper woodland: Influence of vegetation patches

In many semiarid regions, runoff and erosion differ according to vegetation patch type. These differences, although hypothesized to fundamentally affe ct ecological processes, have been poorly quantified. In a semiarid pinon-j uniper woodland [Pinus edulis Engelm, and Juniperus monosperma (Engelm.) Sa rg.] in northern New Mexico, He measured runoff and erosion from the three patch types that compose these woodlands: Canopy patches (those beneath woo dy plants), vegetated patches in intercanopy areas, and bare patches in int ercanopy areas. The bare intercanopy patches exhibited the highest rates, f ollowed by vegetated intercanopy patches and then by canopy patches. Large convective summer storms, though relatively infrequent, generated much of t he runoff and most of the sediment; prolonged frontal storms were capable o f generating considerable runoff but little sediment. A portion of the runo ff and most of the sediment generated from bare intercanopy patches was red istributed down-slope, probably to adjacent vegetated intercanopy patches, demonstrating connectivity between these two patch types. Our results indic ate that there are significant and important differences in runoff and sedi ment production from the three patch types; that bare intercanopy patches a ct as sources of both water and sediment for the vegetated intercanopy patc hes; and that the transfer of water and sediment at small scales is both fr equent enough and substantial enough to be considered ecologically signific ant.