Grazing effects on sustainable semiarid rangeiands in Patagonia: The state and dynamics of the soil seed bank |
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Authors: | Mónica B Bertiller |
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Institution: | (1) Centro Nacional Patagónico, CENPAT-CONICET, Boulevard Brown s/n, 9120 Puerto Madryn, Chubut Argentina, AR |
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Abstract: | The composition of the germinable seed bank was studied in four vegetation states of the Festuca pallescens grasslands in semiarid Patagonia during four years. The aim of this study was to test whether above-ground vegetation states
resulting from grazing exclusion or different combinations of grazing and topography are reflected in different states of
the germinable seed bank. The size of the total and dicot germinable seed bank was positively related to the total cover in
each state. Dicots dominated all germinable seed bank states. Carex patagonica increased its cover as well as its germinable seed bank under grazing disturbance. Grazing did not reduce the germinable seed
bank of perennial grasses in uplands where the grazing pressure is lower as compared with slopes. In slopes the germinable
seed bank of perennial grasses was significantly reduced by grazing. A reduction of the length of the grazing period in late
spring increases the germinable seed bank of perennial grasses both in upland and slope. These results are interpreted in
the frame of a model of management techniques where grazing exclusion during late spring and late summer increases the seed
bank of the perennial grasses and promotes their establishment in uplands. The artificial addition of seeds of perennial grasses
and the manipulation of the soil surface in order to increase "safe sites" appear as management alternatives that deserve
further evaluation to improve plant reestablishment in slopes. |
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Keywords: | : Germinable seed bank states Seed bank strategies Seed bank dynamics Perennial grasses Festuca pallescens Carex patagonica Plant restoration |
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