zahra nikbakht; Mohammad Farzam; Mohammad Khajeh Hosseini; Hamid Ejtehadi
Abstract
The study of soil seed bank provides useful information on management and restoration of natural ecosystems. In the arid environments, some perennial plants may cause accumulation of seed bank under their canopy, thereby protecting them against the livestock herbivory and the other environmental factors. ...
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The study of soil seed bank provides useful information on management and restoration of natural ecosystems. In the arid environments, some perennial plants may cause accumulation of seed bank under their canopy, thereby protecting them against the livestock herbivory and the other environmental factors. This study was conducted with objective to investigate effect of perennial plants on density of soil seeds bank, under different utilization levels in an arid steppe rangeland. Three adjacent rangeland sites were selected, i.e. intense grazing, moderate grazing and no grazing (enclosure), and three line transects were randomly located within each site. Along each transect, soil samples were taken from the depth of 0–5 cm under the canopy of perennial plants or the nearby open space. The seed bank density was determined by the technique for separating seeds from the soil. The density of soil seed bank in the moderate and intensive grazing sites was higher than in the enclosure. In addition, seed bank density under the canopy of perennial plants was significantly higher than in open space, in each of three sites. The highest and lowest seed bank density were observed under the canopy of Rosa persica and Astragalus heratensis, respectively. Generally, the results of this research indicate the key role of perennial range plants in protecting soil seed bank of other plants, under the circumstances of high livestock grazing in the arid steppe rangelands.
Tahereh Sadeghi Shahrakht; Mohammad Jankju; Mansour Mesdaghi
Abstract
Rangeland shrubs may provide mechanical facilitation on their understory plants, by protecting themagainst the livestock grazing. However, such a facilitation effect may vary depending on the rangelandutilization rate. In a field research, mechanical facilitation of rangeland shrubs was compared in ahighly ...
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Rangeland shrubs may provide mechanical facilitation on their understory plants, by protecting themagainst the livestock grazing. However, such a facilitation effect may vary depending on the rangelandutilization rate. In a field research, mechanical facilitation of rangeland shrubs was compared in ahighly grazed, a moderately grazed and an enclosure site; in an arid rangeland, Kakhak, Gonabad,Iran, during spring to summer 2011. Twenty line transects were established in various directions andslope aspects. Forage production was measured by clipping method within the paired plots, i.e. underthe canopy of nursing shrubs and their nearby open areas. In the enclosure site, forage production wassimilar under the canopy of shrubs and in open areas, whereas in the highly and moderately grazedsites there were more forage under the canopies. These results indicate increases in mechanicalfacilitation of rangeland shrubs by increasing the grazing intensity. The mechanical facilitation wasalso varied depending on the life forms of understory species. In the enclosure, the greatest facilitationwas on annual forbs, whereas in the highly grazed site it was on perennial grasses. Results of thisstudy show important role of rangeland shrubs on preserving understory forage plant against theintense livestock grazing.
