The tropical and subtropical dry broadleaf forest biome, also known as tropical dry forest, vine thicket, and vine scrub is located at tropical and subtropical latitudes. Though these forests occur in climates that are warm year-round, and may receive several hundred centimeters of rain per year, they have long dry seasons which last several months and vary with geographic location. These seasonal droughts have great impact on all living things in the forest.
Deciduous trees are predominate in most of these forests, and during the drought a leafless period occurs, which varies with species type. Because trees lose moisture through their leaves, the shedding of leaves allows trees such as teak and mountain ebony to conserve water during dry periods. The newly bare trees open up the canopy layer, enabling sunlight to reach ground level and facilitate the growth of thick underbrush. Trees on moister sites and those with access to ground water tend to be evergreen. Infertile sites also tend to support evergreen trees. Three tropical dry broadleaf forest ecoregions, the East Deccan dry evergreen forests, the Sri Lanka dry-zone dry evergreen forests, and the Southeastern Indochina dry evergreen forests, are characterized by evergreen trees.
Though they have less biologic diversity than rainforests, tropical dry forests are home to a wide variety of wildlife including monkeys, deer, large cats, parrots, various rodents, and ground dwelling birds. Mammalian biomass tends to be higher in dry forests than in rain forests, especially in Asian and African dry forests. Many of these species display extraordinary adaptations to the difficult climate.
This biome is alternately known as the tropical bane forest biome or the tropical and subtropical deciduous forest biome. Locally some of these forests are also called monsoon forests, and they tend to merge into savannas.
Geographical variation
As with seasonal tropical forests, dry forests tend to exist in the drier areas north and south of the tropical rainforest belt, south or north of the subtropical deserts, generally in two bands: one between 10° and 20°N latitude and the other between 10° and 20°S latitude. The most diverse dry forests in the world occur in southern Mexico and in the Bolivian lowlands. The dry forests of the Pacific Coast of northwestern South America support a wealth of unique species due to their dry climate. The Maputaland-Pondoland bushland and thickets along the east coast of South Africa are diverse and support many endemic species. The dry forests of central India and Indochina are notable for their diverse large vertebrate faunas. Madagascar dry deciduous forests and New Caledonia dry forests are also highly distinctive (pronounced endemism and a large number of relictual taxa) for a wide range of taxa and at higher taxonomic levels. Trees use underground water during the dry seasons.
Afrotropic
- Madagascar dry deciduous forests
- AT0202 Madagascar dry deciduous forests
Australasia
- Nusa Tenggara Dry Forests (Indonesia)
- AA0201 Lesser Sundas deciduous forests
- AA0203 Sumba deciduous forests
- AA0204 Timor and Wetar deciduous forests
- New Caledonia dry forests
- AA0202 New Caledonia dry forests
Indomalaya
- Indochina dry forests
- IM0202 Central Indochina dry forests
- Chhota - Nagpur dry forests
- IM0203 Chota Nagpur dry deciduous forests
Neartic
- Northwestern Mexico
- NA0201 Sonoran-Sinaloan ecoregion
Neotropic
- Mexican dry forests
- NT0201 Apure-Villavicencio dry forests
- NT0204 Bajio dry forests
- NT0205 Balsas dry forests
- NT0227 Sierra de la Laguna dry forests
- Tumbesian - Andean valleys dry forests (Colombia, Ecuador, Peru)
- NT0214 Ecuadorian dry forests
- NT0221 Magdalena Valley dry forests
- NT0223 Marañón dry forests
- NT0232 Tumbes-Piura dry forests
- Chiquitano dry forests
- NT0212 Chiquitano dry forests
- Atlantic dry forests
- NT0202 Atlantic dry forests
Oceania
- Hawaii dry forests
- OC0202 Hawaiian tropical dry forests
Biodiversity patterns and requirements
Species tend to have wider ranges than moist forest species, although in some regions many species do display highly restricted ranges; most dry forest species are restricted to tropical dry forests, particularly in plants; beta diversity and alpha diversity high but typically lower than adjacent moist forests.
Effective conservation of dry broadleaf forests requires the preservation of large and continuous areas of forest. Large natural areas are required to maintain larger predators and other vertebrates, and to buffer sensitive species from hunting pressure. The persistence of riparian forests and water sources is critical for many dry forest species. Large swathes of intact forest are required to allow species to recover from occasional large events, like forest fires.
Dry forests are highly sensitive to excessive burning and deforestation; overgrazing and exotic species can also quickly alter natural communities; restoration is possible but challenging, particularly if degradation has been intense and persistent.
See also
- Holdridge life zones in Guatemala
- Seasonal tropical forest
- Tropical vegetation
References
- "WWF - Tropical and Subtropical Dry Broadleaf Forest Ecoregions". Wwf.panda.org. Retrieved 2012-09-25.Â
- 2006-01-13, Sciencedaily: Deep-rooted Plants Have Much Greater Impact On Climate Than Experts Thought Citat: "...The tap roots transfer rainwater from the surface to reservoirs deep underground and redistribute water...increases photosynthesis and the evaporation of water...by 40 percent in the dry season...During the wet season, these plants can store as much as 10 percent of the annual precipitation as deep as 13 meters (43Â feet) underground, to be tapped during the dry months...tree roots acting like pipes to allow water to shift around much faster than it could otherwise percolate through the soil..."
Much material in this article has been reworked from Tropical and Subtropical Dry Broadleaf Forests, by WWF with their permission.
External links
- The Tropical Dry Forest of Costa Rica