Effects of grazing on cold desert shrubs: a simulation model based on relative growth rate
1981
Fetcher, N. (Colorado State Univ., Fort Collins (USA). Range Science Dept.)
A generalized mathematical model for plant growth was developed to simulate primary productivity and response to grazing of cold desert shrubs. The model simulates root, shoot, and carbohydrate reserve biomass for periods of 5-20 y using a weekly time step and equations based on the principles of growth analysis. The effect of soil water on plant growth is simulated by an empirical relationship between average soil water content and annual production. A separate evaporation model simulates weekly soil water content using precipitation data. The plant model requires weekly average and maximum air temperatures. Other data requirements have been reduced so that the model can be adapted to different species and different sites. The effect of shoot removal on productivity of Atriplex confertifolia, Artemisia tridentata and Ceratoides lanata growing in the Curlew Valley in northern Utah was simulated. When productivity was simulated for 20 y with 25% removal in the spring or 50% removal in the winter, the shrubs were able to maintain themselves. But they were not able to maintain themselves when simulated removal in the spring was 50%. The response to simulated grazing appeared to be consistent with field observations of the effects of defoliation on survival
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