Theme 2-3: Forage Production and Utilization--Poster Sessions

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Soil seed banks play a major role in the vegetation dynamics of drylands, where annual rainfall is unpredictable and plants depend on a persistent stage (seeds) to survive over the dry season. The purpose of the study is to understand the behaviour of the rangeland system in terms of soil seed bank dynamics before, during and after crossing the “so called” DTP and to determine whether different management systems plays a role in accelerating the desertification process. Through the use of the Space for Time Substitution Approach the study analysed spatial grazing gradients (gradients radiating from water points) to predict how soil seed banks would respond to long term grazing scenarios. Soil seed bank samples were collected along grazing gradients under two management systems (commercial and communal), processed through seedling emergence method and analysed with SPSS statistical package. Though our results indicated larger soil seed bank under the commercial management system, the seed bank size did not differ significantly along both commercial and communal grazing gradients. Commercially managed sites had a larger seed bank of perennial grasses compared to communal sites. Some of which increased gradually with increasing grazing intensity (Eragrostis trichophora), while other decreased with the increase in grazing intensity (Eragrostis rigidior and Eragrostis pallens). Further testing of other seed processes is still ongoing and will be completed in the 1st quota of 2022. Based on the first results soil seed bank size might not be a good indicator of DTP but rather seed bank life form composition as well as species composition of perennial grasses might serve as good indicators of DTP.

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The Importance of Soil Seed Bank Dynamics as Potential Indicators of Desertification Tipping Point

Soil seed banks play a major role in the vegetation dynamics of drylands, where annual rainfall is unpredictable and plants depend on a persistent stage (seeds) to survive over the dry season. The purpose of the study is to understand the behaviour of the rangeland system in terms of soil seed bank dynamics before, during and after crossing the “so called” DTP and to determine whether different management systems plays a role in accelerating the desertification process. Through the use of the Space for Time Substitution Approach the study analysed spatial grazing gradients (gradients radiating from water points) to predict how soil seed banks would respond to long term grazing scenarios. Soil seed bank samples were collected along grazing gradients under two management systems (commercial and communal), processed through seedling emergence method and analysed with SPSS statistical package. Though our results indicated larger soil seed bank under the commercial management system, the seed bank size did not differ significantly along both commercial and communal grazing gradients. Commercially managed sites had a larger seed bank of perennial grasses compared to communal sites. Some of which increased gradually with increasing grazing intensity (Eragrostis trichophora), while other decreased with the increase in grazing intensity (Eragrostis rigidior and Eragrostis pallens). Further testing of other seed processes is still ongoing and will be completed in the 1st quota of 2022. Based on the first results soil seed bank size might not be a good indicator of DTP but rather seed bank life form composition as well as species composition of perennial grasses might serve as good indicators of DTP.