PJB-2017-173
EFFECTS OF SIMULATED GRAZING (CLIPPING) ON PLANT POPULATION RESPONSES AND RESOURCE ALLOCATION PATTERNS IN A SEMI-ARID ENVIRONMENT
Said Damhoureyeh
Abstract
Surra rangeland reserve is a Steppe rangeland, located in the northwest part of Jordan. The vegetation composition of Surra semi-arid rangeland slopes (North and South facing slopes) were studied. In addition, the study focuses some population aspects of Salsola vermiculata at the reserve under natural conditions. Moreover, the effect of clipping (simulation of grazing) on the regrowth of S. vermiculata plants were studied in order to promote the conservation and sustainable use of this important forage plant. Randomly transects on each site to sample vegetation at 10 m intervals along each transect were delineated. For each sampling point, quadrates of 1 m2 were placed and coverage, species composition, plant density and life form were assessed. The vegetation inside each quadrat was clipped and separated into forage and non-forage components. Fresh and dry weights for each component and relative density and dry biomass for S. vermiculata were determined. The overall shrub species recorded at the site showed a higher species richness at the south facing slopes of 15 shrub species. Density of shrubs (plant/ quadrates) were almost similar except for S. vermiculata where it was more frequent at the north facing slopes (7.5 P/Q ) with high relative density (1.2 P/ Q). Moreover, a detailed vegetation analysis (herbs and shrubs) for north facing and south facing slopes showed higher values of plant densities at the south facing slopes and mostly attributed to herbaceous vegetation. Shrubs were more abundant at the north facing slopes. In general, forage plants constituted more than 90% of the vegetation present in the reserve. Plant cover and vegetation dry biomass was higher at the south facing slopes and mostly was forage vegetation. Herbaceous forage (grass and non-grass) vegetation had the highest densities in the north facing slopes, while only forage grass had the maximum density overall in the south facing slopes. The average S. vermiculata plant size was 0.026 m3 with average biomass of 34 gm. Relative growth rate (RGR) were positive for the unclipped and 30% clipped plants and showed no difference indicating that 30 % clipping could be tolerated by these plants and could be classified as moderate grazing. However, the 60% treatment showed a negative RGR indicating a severe grazing effect of this clipping treatment, emphasizing that native shrubs constituted important forage for the livestock since they tolerate moderate grazing, in addition to soil conservation and reduction of non-forage plant species.
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