Influence of Spanish goats on vegetation and soils in Arizona chaparral
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Authors: K. E. Severson, and L. F. Debano
Date: 1991
Journal: Journal of Range Management
Volume: 44
Number: 2
Pages: 111-117
Summary of Methods: Severson and Debano conducted a study designed to determine whether goats in a short duration grazing system can be used to reduce chaparral in Arizona, and to evaluate the impact of goat browsing on the vegetation and soil resource. Crushing brush increased the effectiveness of the goats; mean total shrub cover was lower on paddocks where brush was crushed vs not crushed. While there were no differences in shrub live oak (Quercus turbinella) prior to any treatment, by the last sampling date the moderately and heavily stocked, crushed paddocks contained less oak cover than any of the uncrushed paddocks except the heavily stocked ones. Shrubs least preferred by goats were not affected, while preferred browse was impacted at all stocking levels. Goat stocking and brush treatments did not affect perennial herbs, while annuals were generally increased by soil disturbance. Less litter accumulated under shrubs subjected to heavy stocking levels compared to unbrowsed paddocks. Concentration of N and P in the soil were also affected under desert ceanothus (Ceanothus greggii) where the soil bulk density was also increased. The results of this study suggest that goats, with or without initial shrub crushing, can be used to reduce shrub cover in Arizona's chaparral region. However, the authors caution that goat browsing may increase erosion, reduce browse available for wildlife, and negatively affect nitrogen cycling in this area if intensive goat management is not practiced.
Article Summary / Main Points: None
Vegetation Types:
MLRA Ecoregions:
Agrovoc Control Words: Riparian zones Rangelands Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: shrub live oak, quercus turbinella, litter, soil nitrogen, soil phosphorus, organic carbon, wildlife habitat
Annotation: Treatments were imposed on a 17-paddock allotment constructed in a "wagon wheel" design. 5 of these paddocks were not included in the experimental design but an additional 4 units were fenced separately to serves as unbrowsed control areas, for 16 experimental paddocks on 228 ha. Treatments were 4 stocking levels (0, 1.4, 2.4, and 4.2 goats/ha based on actual days of use in a 1-year period) and 2 land treatments (brush crushed and not crushed), with each combination replicated 2 times. Stocking levels for moderate (2.4 goats/ha) were based on a previous study in Arizona. Light and heavy levels were fixed at approximately 1/2 and 2 times the moderate rate. Goat were placed on paddocks February 28, 1984. The general program was to graze each paddock 3 days when plants were growing and 5 days during dormant seasons. Shrub data were collected in November 1982, May and October beginning in 1985 through 1987, and in May 1988. Herbaceous data were collected in May and October, 1986 and 1987, and May 1988. Soil and litter data were collected in July 1988.
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