conunon. It occurs in a climate where water stress is absent with no regular annual dry season and an average of monthly rain tall of I 00 mm or more, or where water stress is intermittent with short dry season of monthly rainfall of 60 mm or more or with particular soil conditions. This factor is coupled with high temperature (mean temperature 18°C or more in the coldest month of the year) and a strong evapotranspiration. The high net primary productivity of successional torcsts supports a large animal population, but not the same species as a mature forest. Dominant species groups include Lcguminosac, Moraccac, Mcliaccac, Palmac, and Lauraccac. Diagnostic species groups arc Bromcliaccac and tree terns. In the Caribbean, moist forests occur mainly in lowland areas influenced by north-easterly or north-westerly winds, and windward mountain slopes, e.g., northern part of eastern Cuba, northern Jamaica, eastern Hispafiola, northern Puerto Rico, and small patches in the Lesser Antilles, Trinidad and Tobago. Tropical I Subtropical Dry Broadleaf Forests arc found in areas with high temperatures throughout the year, an annual precipitation of less than I,600 nm1 with one or two long and pronounced dry seasons. The duration and intensity of drought govern the distribution of dry to rests. Dry to rests during the rainy season arc often similar physiognomically to tropical humid forests but arc generally smaller in stature and biomass, lower in biodiversity, and more seasonally pulsed in tree gmwth, reproductive cycles, and organic matter turnover than forests with higher and less seasonal rainfalL The structure and composition of dry forest vary greatly relative to climate, soil, and other environmental tactors. Factors that arc largely governed by latitudinal position such as timing, frequency, and duration of dry periods, arc also important determinants of dry forest characteristics. Dry to rests usually have a high level of endemism. Most woody plants and succulents arc diccious or hermaphrodites but self incompatible. Their reproduction relics on pollinators, particularly bees. Dominant species groups include Capparidaccac, Cactaccac, Erythroxylaccae, Zygophyllaccac, Anacardiaceae, Astcraccae, Malvaccae, Lamiaccac, and Lcgurninosac. Common genera include Acacia, Caesalpinia, Cassia, J\;fimosa, Tabebuia, Capparis, Byrsonima, Lysi!oma, Ceiba, Aspidosperma, EIJ'Ihroxylon, Brya, Pictetia, Plwneria, and Bursera. Diagnostic species arc Jv!elocactus spp., Cepha/ocereus royenii, Leptocerreus quadricostatus, and Tllrinax morrisii. In the Caribbean dry forests arc found in The Bahamas, Caymcn Islands, Cuba, Hispaniola, Jamaica, Leeward Islands, Puerto Rico, Trinidad and Tobago, and Windward Islands. The dry torcst lite zone tends to be favored for human habitation, largely because of relatively productive soils and reasonably comf011able climate. For this reason, few dry forests remain undisturbed. Tropical I Subtropical Couiferous Forests belong to a tire-maintained, single-species dominant system. They occur on nutrient-poor acidic soils, either on qum1z sands, slates and sandstones as subclimax communities, or as paraclimax conmmnities on territic soils. In addition to fires, hurricanes and landslides arc the major natural disturbance affecting the distribution, composition and structure ofthc pine forests. In the Caribbean pine forests arc found in The Bahamas, Turks, Caicos, Cuba, and Hispaniola. In Cuba, coniferous forests occur in the eastern and western ends of the island. The lowland pine forests on the territic soils or slately sandstone arc dominated by Pinus caribaea var. caribaea; while pine forests on deep, acidic fcrritic soils arc dominated by P. cubensis. They arc rich in endemics. Low-altitude pine to rests of Isla de La Juvcntud m·c dominated by P. lropica/is. Montane pine forests on acidic soils derived fi'om sandstone and andcsitic tuffs in south eastern Cuba arc dominated by P. maestrensis. On the island of Hispaniola, montane pine forests arc found in the Cordillera Central with P. occidenta/is. Pine barrens or open pine woodlands on limestone with monospccitic canopy of P.caribaea var. bahamensis occur in The Bahamas. The major threats to pine forests include irrational timber extraction and frequent man-made fires which change the age structure and density of the pine torcsts, and exotic species which displace native species in the understory modifying the fire regime, water and nutrient availability. Shrublwuls and Xeric Scrub occur in areas of rain shadows created by mountains in areas of extreme temperatures. Xeric areas generally have low and highly seasonal precipitation, with great interannual variation. Xeric shrublands arc open vegetation with small trees and shrubs, cacti arc dominant or codominant in both shrub and canopy layers. Vegetation cover by annual plants varies due to large 6 -9-