On conifer plantations, competitive understory vegetation often retards growth and establishment of tree seedlings. In this study, soil water dynamics and orchardgrass (Dactylis glomerata) root growth were measured by Karl and Doescher, in grazed and ungrazed plots on a Douglas-fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa) plantation. Orchardgrass, the major competitive understory species, produced less above and below-ground growth in grazed plots, suggesting that the competitive and resource capturing abilities of this species were reduced by grazing. In the second season of prescribed grazing more soil water was available throughout the day in grazed plots, therefore conifer seedling moisture stress was reduced and these plants were able to grow faster and later in the growing season than seedlings in ungrazed plots. Karl and Doescher conclude that repeated cattle grazing of orchardgrass reduced transipirational surface area and root growth sufficiently to increase soil water availability to seedlings. Thus, prescribed cattle grazing on conifer plantations can enhance seedling status by acting as a regulator of above-and belowground competition.
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