Savanna Vegetation Types Research Articles

Satellite monitoring of fire in the EXPRESSO study area during the 1996 dry season experiment: Active fires, burnt area, and atmospheric emissions

Fire activity in central Africa was monitored with NOAA advanced very high resolution radiometer (AVHRR) satellite imagery, acquired in situ during the 1996 dry season campaign of the Experiment for Regional Sources and Sinks of Oxidants (EXPRESSO). The extent of the area affected by fire was estimated with a contextual active fire detection algorithm, and with a burnt area mapping approach, based on multiple fuzzy thresholds. The latter was considered to produce more accurate results. In a study area of 2×106 km2, and during a 5‐week period, the areas affected were estimated at 112,578 and 525,820 km2 by the active fires and burnt area algorithms, respectively. Biomass densities, combustion factors, and emissions factors for Sudanian savanna, Guinean savanna, and dense tropical forest vegetation types were obtained from the literature, and used to estimate biomass burnt (228–371 Tg), and pyrogenic emissions of aerosols (1.8–2.6 Tg) and of the trace gases CO2 (374–609 Tg), CO (29.2–39.0 Tg), CH4 (2.05–2.73 Tg), and NOx (1.1–1.4 Tg). Because of its high biomass density, the tropical forest was a major source of atmospheric emissions, in spite of the relatively small extent of area burnt in this ecosystem. This highlights the need for particularly accurate estimates of area burnt, biomass density, combustion factor, and emissions factor for the dense tropical forest, as well as the potential for a significant increase in regional pyrogenic emissions as a consequence of deforestation.

Distributional patterns and conservation status of mammals of Swaziland, southern Africa

Distributional patterns (mapped at the quarter-degree square scale) of species richness of 121 species of mammals recorded from Swaziland were examined in relation to the distribution of protected areas (reserves), privately-owned ranches and six vegetation types. The richness of mammal species was highest in the NE and NW, and lowest in the SW areas of Swaziland. Total mammal species richness was positively and highly significantly correlated with the presence of reserves. Similar patterns were shown by artiodactyls, rodents and carnivores. Total mammal species richness, as well as for most mammalian orders, was positively correlated with moist grassveld and moist savanna vegetation types but negatively correlated with dry grassveld. Mammal species richness, especially for the larger species, was very low on Swazi Nation Land, which covers about 60 of the country. The mammalian fauna of the high-lying areas (Highveld) was distinct from that of the low-lying areas (Lowveld). The Middleveld region supported elements of both Highveld and Lowveld species. A large proportion (87.6 ) of Swaziland's mammal species have been recorded from reserves. Two species {Alcelaphus lichtensteini and Lycaon pictus) no longer occur in Swaziland. For effective conservation of Swaziland's mammals, the issue of how to maintain viable populations on Swazi Nation Land will have to be addressed.

Changes in Distribution and Abundance of the Loggerhead Shrike

The Loggerhead Shrike (Lanius ludovicianus) was once widely distributed and common over most of North America, occupying an exclusive breeding range with no other shrikes. Although it occurs in a wide variety of plant associations, this shrike is generally found in landscapes characterized by widely spaced shrubs and low trees interspersed with short grasses, forbs, and bare ground, habitats which include deserts, scrub lands, savannas, and some agricultural settings. The Loggerhead Shrike seems to have been always most abundant in the southern and western portions of its range, with high breeding densities from Florida across the gulf states to Texas and throughout the arid regions of the West. A northeastward expansion in range occurred in the late 1800s in association with deforestation and agriculture. A similar north central expansion occurred in the 1900s with agricultural development of the northern Great Plains and aspen parklands. Contraction and decrease in numbers have been noted in parts of its range since the 1940s, concurrent with the regrowth of forests, loss of pasturelands, and intensive row‐crop agriculture. More recently, Christmas Bird Count data and Breeding Bird Survey data have revealed an overall downward trend across the continent at least since 1966, although numbers are stable or increasing in some locations. Field studies generally implicate alterations in habitat structure and loss of habitat as factors responsible for changes in breeding distribution and overall abundance. Nevertheless, considering its entire distribution in North America and its historical expansions and contractions of range associated with habitat changes, the Loggerhead Shrike does not appear threatened with extinction as a species. We favor a hands‐on approach to management of the critically endangered subspecies, L. l. mearnsi and L. l. migrans, however, and recommend extensive preservation of the natural scrub desert, shrub‐steppe, western oak savanna, and southern savanna vegetation types, which appear to be optimal, core habitats for this species, as well as fostering land‐use practices that favor shrikes in agricultural and suburban landscapes.

Observations on Savanna vegetation-types in the Guianas

The vegetation was studied of a number of savannas in northern and southern Surinam, and in French Guiana. The results are compared in particular with the vegetation classification proposed earlier for northern Surinam, and with some records from the northern Rupununi Savanna, Guyana (Van Donselaar 1965).