Multispecies Allometric Models Predict Grass Biomass in Semidesert Rangeland |
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| Authors: | Aleta M Nafus Mitchel P McClaran Steven R Archer Heather L Throop |
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| Institution: | 1. Rangeland Technician, US Department of Agriculture-Agricultural Research Service, Eastern Oregon Agricultural Research Center, 67826-A Highway 205, Burns, OR 97720, USA;2. Professors, School of Natural Resources, University of Arizona, 325 Biological Sciences East, Tucson, AZ 85721, USA;3. Assistant Professor, Department of Biology, New Mexico State University, Las Cruces, NM 88003, USA.;1. Center for Global Change and Earth Observations, Michigan State University, East Lansing, MI 48823, USA;3. Earth Systems Research Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824, USA;4. Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China;1. University of Arizona, School of Natural Resources & Environment, Tucson, AZ 85721, USA;2. University of Arizona, BIO5 Institute, Tucson, AZ 85721, USA;3. USDA Agricultural Research Service, Southwest Watershed Research Center, Tucson, AZ 85719, USA |
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| Abstract: | Multispecies allometric models to predict grass biomass may increase field study efficiency by eliminating the need for species-specific data. We used field measurements during two growing seasons to develop single-species and multispecies regression models predicting the current year’s aboveground biomass for eight common cespitose grass species. Simple and stepwise regression analyses were based on natural log expressions of biomass, basal diameter, and height, and a dummy variable expression of grazing history. Basal diameter had the strongest relationship with biomass among single-species (adjusted R2 = 0.80 to 0.91) and multispecies (adjusted R2 = 0.85) models. Regression slopes (b) for diameter among single-species (b = 1.01 to 1.49) and the multispecies (b = 1.25) models suggests that biomass will double when diameter increases ~ 75%. Height and grazing history added little predictive value when diameter was already in the model. When applied to actual populations, biomass estimates from multispecies models were within 3-29% of estimates from the single-species models. Although the multispecies biomass-size relationship was robust across the cespitose life-form, users should be cautious about applying our equations to different locations, plant sizes, and population size-structures. |
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