Seasonal grazing impact on cryptogamic crusts in a cold desert ecosystem

Abstract

Since settlement, cattle grazing has been a major cause of soil disturbance in cold desert ecosystems. The objective of this study was to determine the impact of cattle grazing in different seasons on cryptogamic soil crusts. This study was conducted adjacent to the Brigham Young University Skaggs Research Ranch, near Malta, Ida. Five areas of a crested wheatgrass pasture each interplanted with shrubs were evaluated. Each of the 5 areas was subdivided into 4 paddocks; a control paddock remained ungrazed, while the other 3 paddocks were grazed in either spring, summer, or winter. Each of the 1.2-ha grazed paddocks was grazed annually in the same season for 2 consecutive years by 10 cows for 4 consecutive days. Percent of the soil surface covered by litter, vascular plant bases, and cryptogams was measured using a 10-pin, point sampling frame. Mosses were the main component of the cryptogamic soil crusts under all grazing treatments. Winter grazing had no effect on the moss component of the crusts while spring and summer grazing reduced mosses. While winter grazing had significantly less impact on the lichen component of crusts relative to spring and summer grazing, there was a 50% reduction relative to the control plots. Total cryptogamic cover in the control paddocks averaged 27.6%; winter grazed paddocks 27.4%; summer grazed paddocks 14.4%; and spring grazed paddocks 10.6%. Controlled winter grazing has minimal impact on the total cryptogamic plant cover that protect soil surfaces on cold desert range ecosystems.