Recovery rate of depleted range sites under protection from grazing

Published source details McLean A. & Tisdale E.W. (1972) Recovery rate of depleted range sites under protection from grazing. Journal of Range Management, 25, 178-184.
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Summary

In the North American Pacific Northwest, information on the number of years rest necessary for recovery of ‘depleted’ rangelands due to livestock grazing was lacking. This study attempted to evaluate effects of livestock exclusion on depleted (overgrazed) ranges by assessing vegetation changes in four exclosures in the ponderosa pine Pinus ponderosa zone and three on rough fescue Festuca scabrella grasslands in southern British Columbia, Canada.

The seven livestock exclosures were constructed mostly in the 1930’s. Periodic vegetation observations were made until more concerted monitoring was undertaken in 1959-60, and repeated in 1968-69. Inside and adjacent to exclosures, canopy cover and frequency of occurrence of each herb and small shrub species was recorded in 50 frames (20 x 50 cm) along a 25 m transect. Herbage yields were determined by clipping samples at ground level in five 9.6 ft² (0.89 m²) plots per site, drying and weighing. Range condition was classified (poor, fair or good).

Within exclosures considered of poor condition at time of exclosure, little change in plant composition occurred from 1959-1969. It took longer for these sites to progress to fair condition, than for those in fair condition at the outset to recover to good condition. The main plants to increase through livestock exclusion were two grasses, bluebunch wheatgrass Agropyron spicutum (Pseudoroegneria spicata) and rough fescue. The main species to decrease were Sandberg bluegrass Poa secunda, low pussytoes Antennaria dimorpha and grey rabbitbrush Chrysothamnus nauseosus.

Only approximate lengths of time for recovery in range condition could be assigned to each exclosure due to slowness of change, infrequency of data recording and individual site characteristics. However, the authors estimate that it will take 20 to 40 years of livestock exclusion for overgrazed ranges in these rough fescue and ponderosa pine zones to recover to excellent range condition.

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https://www.uair.arizona.edu/holdings/journal/issue?r=http://jrm.library.arizona.edu/Volume25/Number3/