Woodland Biomes Research Articles

Physio-climatic classification of South Africa's woodland biome

In an effort to develop more holistic ecosystem approaches to resource assessment and management, landscapes need to be stratified into homogeneous geographic regions. These regions can then be used in a monitoring framework to develop reliable estimates of ecosystem productivity. A regional characterization of the woodland biome has been developed for South Africa, delineated by satellite imagery and using environmental data and a rigorous statistical methodology. Distribution maps of key environmental variables are analyzed by factor analysis, an iterative clustering technique and maximum likelihood classification to quantify and identify homogeneous physio-climatic units. A spatial clustering technique was used to identify regions, which are statistically different with regard to five physiographic, climatic and edaphic variables deemed important within southern African savanna woodlands. The woodland biome of South Africa at 1km resolution was successively divided. Thirty year mean monthly temperature, total plant-available water balance of soil, elevation, landscape topographic position, and landscape soil fertility were used as input classification variables. The map data were submitted to a factor analysis and varimax axis rotation. The factor analysis removes correlations from the input variables, reduces the dimensionality, and normalizes the axis measurements. A cluster analysis was performed on the three principal factor scores using a modified iterative optimization clustering procedure to determine the finest level of classes statistically permitable. Twenty-seven identified unimodal cluster signatures were then submitted to a maximum likelihood classification where the statistical probability of the GIS cell assignment is carried out to determine class membership. The final map of custom physio-climatic regions is described, and these custom regions are compared with a vegetation potential map of the woodland types identified in the South African summer rainfall zone.

Extending the Namibian protected area network to safeguard hotspots of endemism and diversity

Namibia's state protected area network (PAN) covers 13.8% of the country's land area, but is seriously inadequate as a basis for effective biodiversity conservation. The early parks system was not designed with biological diversity in mind, and reflects instead a history of ideological, economic and veterinary considerations. Currently, parks in the Namib Desert biome make up 69% of the PAN, while savanna and woodland biomes are somewhat underrepresented (7.5 and 8.4% of their respective land areas), and the Karoo biome is badly underrepresented (1.6%). Four of 14 desert vegetation types are comprehensively protected, with 67 to 94% representation in the PAN, yet six savanna types have 0 to 2% representation by area. Mountain Savanna, a vegetation type unique to Namibia, is wholly unprotected. The status of two marine reserves, which in theory protect only 0.01% of Namibia's marine environment, needs clarification and augmentation with new reserves. Nearly 85% of Namibia's land is zoned for agriculture, so effective biodiversity protection means working outside the PAN to improve the sustainability and diversity of farming practices. Wildlife conservancies on commercial and communal farmlands show excellent potential to mitigate the ecological skew in the state PAN, with the ecological management of large areas being decentralized to rural communities in habitats otherwise neglected for conservation. Two important endemism zones, the Kaoko escarpment and coastal plain and the Sperrgebiet succulent steppe, plus the species-rich Caprivi area, offer three valuable opportunities for regional consolidation of protected areas into transboundary 'peace parks' or biosphere reserves.

Why burn the bush? Social approaches to bush-fire management in West African national parks

Fire is a major threat to many national parks worldwide. Social research in the savanna woodland biome of northern Benin shows that in addition to the commonly cited reasons for setting bush-fires—tradition, clearing fields, hunting, and improving dry season grazing—villagers burn to deter wild animals, to increase the supply of certain forest products, and to take revenge on the national parks. Villagers' perceptions of the effects of fire often correspond to our scientific understanding. With an appreciation of the villagers' logic we can predict that the establishment and protection of national parks will increase the incidence of human-caused bush-fires. To counter this, parks need to promote changes in long-standing traditions, encourage more intensive land-use practises, assist in protecting crops and livestock against wild animals, and improve relationships with the surrounding villagers.

Processes controlling acid attenuation in the unsaturated zone of a Triassic sandstone aquifer (U.K.), in the absence of carbonate minerals

Continuous core samples were taken through the unsaturated zone at three sites on the outcrop of Permo-Triassic sandstone in the British West Midlands. Sample sites were chosen for lack of recent, direct anthropogenic disturbance, and for differing vegetation: heathland, birch woodland and conifer forest. Interstitial water was extracted and analyzed for 32 major and trace elements. Solid phases were analyzed for exchangeable cations and mineralogy. The rate of recharge calculated using a Cl mass balance method was three times greater below heathland than below afforested sites owing to higher evapotranspiration rates in the woodlands. Carbonate minerals were absent from the unsaturated zone at each site. Soil solutions were acidic and soils at the woodland sites were more acidic (pH 4.0) than those at the heathland site (pH 4.5). Acidic interstitial water solutions were found to up to 5.0 m depth in the unsaturated zone and are partially neutralized by two aluminosilicate mineral reactions in the unsaturated zone: cation exchange and K-feldspar dissolution. The rate at which these acid neutralizing reactions act to neutralize acidity is revealed by the rate of depletion of base cations from the unsaturated zone in recharge solutions; K + (dissolution), Ca +2 + Mg +2 (cation exchange). The total base cation depletion rate was greatest below heathland; this can be attributed mainly to the greater rate of SO 4 assimilation by the woodland biome.

Progress with vegetation studies in South Africa

Vegetation studies at various levels of detail and using various methods are briefly reviewed. The approach and procedures of the Zurich-Montpellier school of phytosociology as a standard methodology for regional studies has become increasingly recognized. Progress has been made in regional studies in the fynbos and woodland biomes. but grassland, forest and karoo vegetation have been much neglected. There have also been marked increases in activity over a wide range of additional vegetation studies including new fields of research, particularly ecosystem studies. However, there are still vast gaps in our knowledge of the basic vegetationa! resources of the country. A systematic regional-study programme is being launched to remedy these deficiencies in fundamental knowledge.