Forests mosaic

Land use changes in the tropics have resulted in a landscape characterized as a mosaic of logged forests, cleared fields, and successional forests. This results in the transformation from extremely fire resistant rainforest ecosystems to anthropogenic landscapes in which fire is a common event (16, 17), Fires occur in disturbed tropical forests because deforestation has a dramatic effect on microclimate. Deforestation results in lower relative humidities, increased wind speeds, and increased air temperatures. In addition, deforestation results in increased quantities of biomass that are susceptible to fire. This biomass may be in the form of forest slash, leaf litter, grasses, lianas or herbaceous species (16, 18). 

The term ponderosa-Jeffrey type is a general term that includes a mosaic of five subtypes described by McBride on the basis of species dominance. These subtypes are ponderosa pine forest, ponderosa pine-white fir forest, ponderosa pine-Jefh y pine forest, Jeffry pine forest, and Jeffrey pine-white fir forest. The injury by oxidant air pollutants is most intense in the types dominated by ponderosa pine and less intense in the Jeffry pine types. In the field plots of these various types, the average area covered by shrubs is only 3.8% in the ponderosa types, but 26% in the Jeffrey pine types. ... 

Liew, S.C., 1998. A study of the 1997 forest fires in Southeast Asia using SPOT Quicklook Mosaics. International Geoscience and Remote Sensing Symposium, Seattle, July 1998. 

Fossil pollen in a series of small forest hollows about 10 m in diameter provides a record of hemlock invasion of individual forest stands along a 10-km transect in northern Michigan. The distribution of species within the present-day forest, which has never been clearcut, is patchy—a mosaic of stands dominated by hemlock interspersed with mixed stands and large patches dominated by sugar maple (Acer saccharum). Pollen diagrams from four... 

The natural vegetation of a large majority of the Venezuelan Llanos region consists of a complex mosaic of herbaceous ecosystems, especially savannas. The next most important biome of these wide plains is that of the forests, ranging from small areas of evergreen (ombrophilous) lowland forests to entirely deciduous (tropophilous) low forests, and to riverine forests of the gallery type. 

The uniqueness of the eastern seasonally dry tropical forests has made floristic comparisons with the other seasonally dry tropical forests in Peru and adjacent countries difficult, revealing little relationship (Bridgewater et al., 2003 Linares-Palomino et al., 2003). Only 20 and 24 species are shared with the Equatorial and inter-Andean seasonally dry tropical forests, respectively. This condition is accentuated by a mosaic of vegetation formations in the area, which has resulted in characteristic wet forest species intergrading with seasonally dry tropical forest species to form a distinctive seasonally dry tropical forest formation. Additionally, this region has been under human disturbance for several decades, and natural or original vegetation is hard to find. 

FIGURE 20.1 The seasonally dry vegetation of tropical Africa. The map shows dry forests, savannas (mainly woodlands) and hushland and thicket. Dry forests are shown only approximately most areas are too small to map at this scale. Grasslands are also not sufficiently extensive to map at this scale most occur as part of a mosaic or catena within woodlands. Data from White (1983). 

Nevertheless, it must be emphasized here The additional parameters such as soil, climate, water availability etc. caimot fully clarify the complex mosaic of damage occurence in order to justify an accepted cause effect theory of the new forest damages. These possible explainations don t even suffice to reduce the many damaged forest areas into a few large catagories. In summary A discourse over the development and present situation of forest decline in Central Europe such as the one presented here, can only offer a coarse synopsis of the quantitative aspects of the phenomenon. 

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