HR: 1330h
AN: H32C-0580    [PDF]
TI: Rooting Dynamics and Soil Water Variation of Native Shrubs
AU: * Kizito, A
EM: fred.kizito@oregonstate.edu
AF: Oregon State University, 3017 ALS Department of Crop and Soil Science, Corvallis, OR 97331 United States
AU: Dragila, M I
EM: Maria.Dragila@orst.edu
AF: Oregon State University, 3017 ALS Department of Crop and Soil Science, Corvallis, OR 97331 United States
AU: Sene, M
EM: modousen@refer.sn
AF: CERAAS/ISRA, BP 33250 Thies-Escale, Thies, 00000 Senegal
AU: Dick, R
EM: Richard.Dick@orst.edu
AF: Oregon State University, 3017 ALS Department of Crop and Soil Science, Corvallis, OR 97331 United States
AB: Understanding the relationships that exist in the soil-plant-atmosphere continuum in semi-arid areas presents particular challenges, requiring accurate quantification of soil water with depth, a highly variable and limiting parameter in these vulnerable ecosystems. Two sites in the Peanut Basin of Senegal were selected to study rooting patterns of native shrubs and the corresponding variation of water distribution within the soil profile in both the dry and wet season. During dry periods or dry spells in the wet season, soil moisture content ($\theta$$_{v}$) surrounding the shrub's shallow roots is substantially moister than the adjacent soil matrix. It is therefore hypothesized, that nearing a condition of water stress, shrubs may participate in redistribution of soil water, effectively changing their own environment and enhancing their survival as well as that of neighboring annual crops. A possible region of water redistribution is interpreted to be between 15-75 cm depth, with the upper 0-15 cm remaining typically dry ($\theta$$_{v}$ $<$ 1 m$^{3}$m$^{-3}$) and forming a self mulching mechanism protecting lower horizons from the intense evaporation, and the lower 75 to 105 cm depth acting as a "moist reservoir" ($\theta$$_{v}$ $\sim$ 6 m$^{3}$m$^{-3}$). We investigated shrub root depths, distribution, size, density and gravimetric soil water variation at 15 cm depth increments to 110 cm, and at 10 cm lateral spread increments to 200 cm from each shrub trunk. Shrubs exhibited a complex heterogeneous rooting system with approximately 50% of the root biomass occurring in the upper 30 cm and 95% in the upper 110 cm. Root study and soil moisture results are used to select optimal sensor placement in relation to shrub root depth and lateral spread extent. Monitoring is continuing for soil water and tension variation with sensors concentrated between 15 and 75 cm. Accurate quantitative data on the vertical and horizontal distribution of roots permits us to estimate how shrubs may alter water use by annual crops and modify water dynamics in this ecosystem.
DE: 1809 Desertification
DE: 1818 Evapotranspiration
DE: 1851 Plant ecology
DE: 1866 Soil moisture
DE: 1878 Water/energy interactions
SC: Hydrology [H]
MN: 2003 Fall Meeting