Stability of wooded patches in a South African nutrient-poor grassland: do nutrients, fire or herbivores limit their expansion?
| Autor: | Esther van Tellingen, Frank van Langevelde, Ian Gaigher, Anja A. Mourik, Ignas M. A. Heitkönig |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
media_common.quotation_subject
complex mixtures subtropical savanna Grassland Competition (biology) Nutrient dry savannas vegetation Ecosystem Water content Ecology Evolution Behavior and Systematics media_common fertility geography Herbivore geography.geographical_feature_category biology Ecology food and beverages dynamics trees Vegetation PE&RC biology.organism_classification humid savanna Seedling Wildlife Ecology and Conservation Environmental science ecosystems competition encroachment |
| Zdroj: | Journal of Tropical Ecology, 23(5), 529-537 Journal of Tropical Ecology 23 (2007) 5 |
| ISSN: | 1469-7831 0266-4674 |
| DOI: | 10.1017/s0266467407004282 |
| Popis: | Patches of wooded vegetation in nutrient-poor grassland characteristically contain high soil moisture and nutrient availability compared with surrounding grassland. These ‘islands of fertility’ appear stable in size, suggesting that tree recruitment at the patch boundary is limited. We hypothesize that tree establishment in adjacent grassland is limited by (1) competition for resources, (2) fire or (3) herbivory. In a South African grassland, we measured moisture availability and conducted a bioassay experiment to analyse whether soil nutrient limits tree recruitment at the patch boundary. We thus measured nutrient concentrations of maize plants grown in patch, boundary and grassland soil. To investigate whether browsing or fire affected tree seedlings at the patch boundary, we burned plots including patches, and used fences to exclude browsers. Neither soil moisture nor nutrient availability at the boundary differed from inside the patches, suggesting that tree recruitment at the boundary is not resource limited. Both fire and browsing combined caused a significantly lower tree seedling growth at the patch boundary, suggesting that these two factors can impede tree recruitment. The balance between positive feedback mechanisms facilitating tree recruitment, and the negative impact of fire and browsing can explain the apparent stability of these islands of fertility. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|