Forest and water relations in miombo woodlands

Miombo is a significant biome covering about 10% of the African landmass. Climate semi-aridity is the main edaphic determinant. Range of annual rainfall and dry season length is high, but the unimodal rainfall distribution is common for all miombo. Water is increasingly an issue of trade-off between different land uses and increasing demand on biomass production. This review gives a basic description of major components in the relations between tree cover and water in semi-arid landscapes. From this, in lack of relevant research within miombo landscapes, a scientifically based discussion is given on how future uses and management of these complex woodlands could serve in better management of scarce water resources and in what ways more research in these aspects could enlighten this discussion. It is concluded that, like for other semi-arid landscapes, there is need for understanding and developing more complex stand management to optimize biomass production and water use efficiency. At the same time climate change adaptation will add to this need of deepened biophysical process understandin

Referat av föredrag av prof. Bengt Gustafsson

No abstract availabl

Alternativa metoder till djurförsök

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Egg buoyancy of flounder, Platichthys flesus , in the Baltic Sea—adaptation to salinity and implications for egg survival

Highlights: • Egg specific gravity vary between areas/subpopulations as an adaptation to salinity. • Egg diameter differ between areas/subpopulations whereas egg dry weight does not. • Habitat suitability for egg survival vary depending on salinity and oxygen conditions. • Egg survival probabilities increased following a major saline water inflow event. Abstract: Vertical distribution of eggs as determined by the egg buoyancy, i.e. the difference in specific gravity between the egg and the ambient water, have profound implications for the reproductive success and hence recruitment in fish. Here variability in egg specific gravity of flounder, Platichthys flesus, was studied along a salinity gradient and by comparing two reproductive strategies, spawning pelagic or demersal eggs. Egg characteristics of 209 egg batches (covering ICES subdivisions (SD) 22–29 in the brackish water Baltic Sea) was used to reveal the significance of egg diameter and egg dry weight for egg specific gravity (ESG), subpopulations, and egg survival probabilities of pelagic eggs following a major saline water inflow event. As an adaptation to salinity, ESG (at 7 °C) differed (p < 0.001) between areas; three subpopulations of flounder with pelagic eggs: 1.0152 ± 0.0021 (mean ± sd) g cm−3 in SD 22, 1.0116 ± 0.0013 g cm−3 in SD 24 and 25, and 1.0096 ± 0.0007 g cm−3 in SD 26 and 28, contrasting to flounder with demersal eggs, 1.0161 ± 0.0008 g cm−3. Egg diameter differed (p < 0.001) between subpopulations; from 1.08 ± 0.06 mm (SD 22) to 1.26 ± 0.06 mm (SD 26 and 28) for pelagic eggs and 1.02 ± 0.04 mm for demersal eggs, whereas egg dry weight was similar; 37.9 ± 5.0 μg (SD 22) and 37.2 ± 3.9 μg (SD 28) for pelagic, and 36.5 ± 6.5 μg for demersal eggs. Both egg diameter and egg dry weight were identified as explanatory variables, explaining 87% of the variation in ESG. ESG changed during ontogeny; a slight decrease initially but an increase prior to hatching. Egg survival probabilities judged by combining ESG and hydrographic data suggested higher egg survival in SD 25 (26 vs 100%) and SD 26 (32 vs 99%) but not in SD 28 (0 and 3%) after the inflow event, i.e. highly fluctuating habitat suitability. The results confirm the significance of ESG for egg survival and show that variability in ESG as and adaptation to salinity is determined mainly by water content manifested as differences in egg diameter; increase in diameter with decreasing salinity for pelagic eggs, and decreased diameter resulting in demersal eggs

Synpunkter pi utrustning för bäddmaterialshantering

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Enclosures in West Pokot, Kenya: Transforming land, livestock and livelihoods in drylands

Dryland livestock production systems are changing in many parts of the world, as a result of growing human populations and associated pressure on water and land. Based on a combination of social and natural science methods, we studied a 30-year transformation process from pastoralism to a livestock-based agro-pastoral system in northwestern Kenya, with the overall aim to increase the understanding of the ongoing transition towards intensified agro-pastoralist production systems in dryland East Africa. Key to this transformation was the use of enclosures for land rehabilitation, fodder production, and land and livestock management. Enclosures have more soil carbon and a higher vegetation cover than adjacent areas with open grazing. The level of adoption of enclosures as a management tool has been very high, and their use has enabled agricultural diversification, e.g. increased crop agriculture, poultry production and the inclusion of improved livestock. Following the use of enclosures, livelihoods have become less dependent on livestock migration, are increasingly directed towards agribusinesses and present new opportunities and constraints for women. These livelihood changes are closely associated with, and depend on, an ongoing privatization of land under different tenure regimes. The results indicate that the observed transformation provides opportunities for a pathway towards a sustainable livestock-based agro-pastoral system that could be valid in many dryland areas in East Africa. However, we also show that emergent risks of conflicts and inequalities in relation to land, triggered by the weakening of collective property rights, pose a threat to the sustainability of this pathway