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The effect of soil porosity and plant root biomass on the hydrologic characteristics of rangeland plant communities

Carol Dawn Franks, University of Nebraska - Lincoln


Accurate soil erosion and hydrology predictions are needed to determine the impact of farm or ranch management practices on soil loss. The objective of this study was to determine if near surface data (0 to 2.5 cm depth) improved erosion and hydrologic predictions over 0 to 10 cm depth data for specific sites. Eleven benchmark sites were selected from throughout the western U.S. Each site had a different soil series and historical plant community. Two or three different non-climax plant communities were located on each soil and within the historical plant community (subsites). A rotating boom rainfall simulator was used to determine the hydrologic variables; peak runoff rate, total sediment yield, sediment/runoff rate ratio, sediment rate per hr, and equilibrium infiltration rate for each subsite. Annual plant production, root biomass (topsoil), root/shoot ratio, plant species counts, and lists of the 10 most common species were determined for each subsite. Soil laboratory measurements included moisture content at 0.2 MPa; bulk density; aggregate stability; Atterberg limits; cation exchange capacity (CEC); 1.5 MPa moisture content/clay % ratio; and clay, sand, and organic carbon content. Site characteristics measured were slope, bare soil; canopy, grass, forb, and shrub cover. ^ The 0 to 2.5 cm depth dataset predicted peak runoff rate, total sediment yield, and infiltration well (r2 was 0.83, 0.71, and 0.71, respectively). It also predicted sediment yield per hour well when the Vertisols were excluded (r2 was 0.68 and 0.62). The 0 to 10 cm depth dataset was a better predictor of the sediment/runoff ratio (r2 was 0.62). The 0 to 2.5 cm dataset more closely reflected the soil surface conditions (such as crusting) affecting intake rates for the soils. ^ The moisture content at 0.2 MPa and total porosity (from bulk density), EGME specific surface area, and CEC improved predictions (0 to 2.5 cm data level of significance 0.95, 0.69, 0.90, and 0.96, respectively). The EGME specific surface area and CEC were nearly equal (significance 0.95 and 0.96). Atterberg limits improved predictions when the Vertisols (which form cracks) were included (significance 0.95 and 0.76). The site and plant community variables canopy cover, bare soil, annual production, root biomass, and root/shoot ratio influenced the erosion and hydrology. Bare soil and root biomass were the most important (significance –0.83 and 0.76). ^

Subject Area

Agriculture, Agronomy|Agriculture, Soil Science|Agriculture, Range Management

Recommended Citation

Franks, Carol Dawn, "The effect of soil porosity and plant root biomass on the hydrologic characteristics of rangeland plant communities" (2000). ETD collection for University of Nebraska - Lincoln. AAI9976988.