HR: 08:55h
AN: B51A-04    [PDF]
TI: Spatio-temporal Variation in Soil Water in a Semiarid Woodland: Implications for Woody Plant Encroachment
AU: * Bresehars, D D
EM: daveb@lanl.gov
AF: Los Alamos National Laboratory, Earth and Environmental Sciences Division Mail Stop J495, Los Alamos, NM 87545 United States
AU: Myers, O B
EM: OMYERS@UNM.EDU
AF: University of New Mexico, Center for Population Health 2701 Frontier Place, NE Surge Bldg., Rm 140, Albuquerque, NM 87131-5267 United States
AU: Barnes, F J
EM: fyb@lanl.gov
AF: Los Alamos National Laboratory, Earth and Environmental Sciences Division Mail Stop J495, Los Alamos, NM 87545 United States
AB: Woody plant encroachment in dryland ecosystems is an issue of global concern, yet mechanisms related to encroachment are poorly understood. Mechanisms associated with woody plant encroachment likely relate to soil water dynamics, yet few long-term data sets exist to evaluate soil water heterogeneity. Here we highlight how soil water varies both temporally (wet vs. dry years and snow vs. rain dominated months) and spatially (vertically with depth and horizontally beneath vs. between the canopies of woody plants). We measured soil water content using neutron probe over a 15-year period in a pinyon-juniper woodland at the Mesita del Buey Research Site in northern New Mexico. Our objectives included assessing (1) the temporal variability of soil water, both as a function of depth and as a function of cover (canopy patches beneath trees, intercanopy patches between trees, and edges between the two patch types); and (2) implications for the vertical and horizontal distributions of plant-available water. Our results highlight (1) large temporal variations in soil water availability, driven largely by differences in winter precipitation, and (2) the potential importance of considering horizontal as well as vertical heterogeneity in soil moisture. The spatio-temporal variation in soil water that we quantify highlights the potential complexity of changes in the water budget that could be associated with woody plant encroachment and emphasizes the importance of considering horizontal as well as vertical heterogeneity in soil water in improving our understanding of mechanisms associated with woody plant encroachment.
DE: 0400 Biogeosciences
DE: 1655 Water cycles (1836)
DE: 1800 HYDROLOGY
DE: 1851 Plant ecology
DE: 1866 Soil moisture
SC: Biogeosciences [B]
MN: 2003 Fall Meeting