Quantification and Simulation of Grazing Impacts on Soil Water in Boreal Grasslands

Abstract

AbstractWe conducted a 2‐year study in central Alberta to quantify and simulate the soil water status of boreal grasslands under three grazing systems using wapiti (Cervus elaphus Canadensis), viz. (1) ungrazed control (UNG), (2) high intensity [4.16 animal unit month per ha (AUM) ha−1 ] short‐duration grazing (SDG) and (3) moderate intensity (2.08 AUM ha−1) continuous grazing (CG). Soil water was measured from May 1997 to September 1998 to a depth of 15 cm. Total annual precipitation in 1997 and 1998 was 494 and 429 mm respectively. In both years grazing treatments reduced soil water. Soil water content under SDG was significantly (P < 0.05) lower than CG. Simulation of soil water on each grazing system was conducted using PASTURE, a simple compartmental system dynamics model. Evaluation of the model was conducted using statistical criteria that included calculation of average error, root mean square, coefficient of residual mass and modelling efficiency and comparing these statistics against optimal values. Although the model under‐predicted soil water, simulations of soil water for grazing treatments in both years were closest to measured values with modelling efficiency (how well observed values are close to simulated values) up to 68 %.