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- Backéus, Ingvar, 1945-, et al.
(författare)
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Diameter growth of trees in miombo and acacia woodland in an eroded landscape in NE Tanzania
- 2022
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Ingår i: African Journal of Ecology. - : John Wiley & Sons. - 0141-6707 .- 1365-2028. ; 60:3, s. 714-722
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Tidskriftsartikel (refereegranskat)abstract
- Diameter increment of trees typical of miombo and acacia woodland was studied dur- ing a period of 20 years in Kondoa district, Tanzania. The study was performed in permanent plots in a severely degraded area subjected to considerable restoration efforts. A total of 15 species were selected from a database collected within a pro- ject for monitoring the landscape recovery. Growth performance of African woodland species was searched for in the literature for comparison, and a comprehensive list of citations was compiled. We found growth to fall within the range reported in earlier studies, although growth varied both between and within species. There are reports that the radial increments of trees are unimodal over their lifespan, but we found no clear support. In several species, the annual growth increased with stem diameter. Growth during the rainy ENSO year 1997/98 was pairwise compared with the preced- ing two years and was found to be significantly higher during the wet year, pointing to soil water as a limiting factor. We conclude that free development is an alternative to tree planting on marginal land.
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- Cassing, Gunilla, 1972-
(författare)
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Deciduous tree occurrence and large herbivore browsing in multiscale perspectives
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aspen ( Populus tremula), rowan (Sorbus auquparia) and sallow (Salix caprea) are deciduous tree species of low economic value for forestry and contribute to biodiversity of boreal forests. The species are rare in managed forest landscapes, and severely browsed by moose. Their recruitment needs to increase to meet requirements of sustainable forestry to factors that affect occurrence need to be indentified. Paper I is an exploratory study on distribution of these species in relation to natural and cultural factors. In paper II moose browsing on saplings, in young forests and the influence of the landscape at three spatial scales: stand (8.6 ± 0.8 SE ha), winter home range of moose (10 km2) and annual home range of moose (25 km2). Presence of these rare species was depending on a multitude of factors acting at different spatial scales. The most important variables were soil quality, successional stage, and ownership at the stand scale and area of deciduous forest at the landscape scale. Moreover, saplings occurred at low densities in young forests (paper II) and most interestingly, saplings occurred most in middle-aged forests (20-80 years) and less than expected in younger forests (<20y) (Paper I). Browsing intensity on the different species corresponded with moose food preference and annual home range scale was most relevant for understanding browsing. Browsing on rowan was highest where the volume of deciduous food and overall young forest area were low. Browsing on birch increased when pine volume and mean patch size of young forest increased, whereas browsing on aspen was negatively related to the same variables. Thus, my results strengthen the idea that food selection is a scale-dependent process and that trade-offs between food and cover may exist for moose. Moreover, I conclude that the presence of deciduous species was a result mainly of soil quality, forest management intensity, landscape context and that the distribution of food for moose at landscape scales similar to or larger than their home range may be useful for predicting browsing on the stand scale. I propose that deciduous forests may be valuable predictors of regeneration potential in the forested landscape, and that understory deciduous sapling in middle-aged forests may be important to promote restoration and conservation actions.
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| 10. |
- Wallgren, Märtha, et al.
(författare)
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Mammal community structure in relation to disturbance and resource gradients in southern Africa
- 2009
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Ingår i: African Journal of Ecology. - : Wiley. - 0141-6707 .- 1365-2028. ; 47:1, s. 20-31
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Tidskriftsartikel (refereegranskat)abstract
- The arrangements of mammals differ along environmental gradients, such as of disturbance and resources. We examined how mammal community composition in the Kalahari, Botswana, varied in relation to disturbance and resource gradients. We predicted that livestock-keeping villages are disturbances and pans are resources for wildlife, that the responses of mammals to disturbance and resources depend on their functional types and that increased disturbance over time has reduced the numbers and distributions of wildlife. The methods involved road-side counts of mammals > 0.2 kg and trapping of small mammals, < 0.2 kg. The disturbance gradient was more important than the resource gradient for explaining the distribution of mammals > 0.2 kg. Communities in low disturbance-high resource areas were most diverse regarding species and functional types. Small mammal species richness and abundances were unaffected by villages, but increased with distance from pans. Villages were particularly deterring to large wild herbivores, functionally similar to livestock. Most large wild herbivores had decreased since 1975-1983. We conclude that large and medium-sized mammals are highly affected by large-scale disturbance gradients, while small mammals are most dependent on small-scale variation in resources, probably shelter and food. Increased disturbance over time leads to decreasing ranges and numbers of the large wild herbivores.
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