Print Report
F003 Tropical Dry Forest & Woodland Formation
Type Concept Sentence: Tropical Dry Forest & Woodland is dominated by broad-leaved drought-deciduous, semi-deciduous, and small-leaved or sclerophyllous evergreen trees where rainfall is lower, often associated with more strongly seasonal, tropical climates, rainshadows, or drying winds. At continental scales, the largest areas occur between 10° and 23°N and S latitude.
Common (Translated Scientific) Name: Tropical Dry Forest & Woodland Formation
Colloquial Name: Tropical Dry Forest & Woodland
Hierarchy Level: Formation
Type Concept: Tropical Dry Forest & Woodland, including most monsoon forests, occurs in extensive areas near the equator around the globe between about 10° and 23°N and S latitude, though it is also found near windward coasts and on the leeward sides of mountains or islands. These forests are dominated by broad-leaved drought-deciduous trees or small-leaved (micro- to mesophyll) evergreen trees or broad-leaved (meso- to macrophyll) sclerophyllous-leaved trees. Evergreen needle-leaved trees may occur in association with these other growth forms. It is a medium to high forest varying on average from 15 to 25 m tall, typically with several structural levels as complex upper canopy, several subcanopy levels of treelets and shrubs, woody vines, and an irregular low herbaceous plant stratum. Canopy heights decrease and canopy coverage tends to decrease as the climate dries until the forests are reduced to open, short-statured (5-15 m) woodlands (more rarely shorter). Included are semi-evergreen, partially sclerophyllous, semi-deciduous and deciduous, mostly dense to semi-dense forests adapted for a distinct period of seasonal winter drought, resulting in 4 to 7 months of drought (rainfall 60 mm or less), during which some or all of the trees lose their leaves. Annual rainfall ranges from 100 to 200 cm. The considerable diversity of dry tropical forest and woodland types are related to the topographic, hydric and edaphic variations as well as with the floristic composition and different biogeography.
Diagnostic Characteristics: Tropical Dry Forest & Woodland is dominated by broad-leaved drought-deciduous trees or, more rarely, small-leaved (micro- to mesophyll) evergreen trees or broad-leaved (meso- to macrophyll) sclerophyllous-leaved trees. Thorn forest scrub, and scrubby cerrado are excluded. Evergreen needle-leaved trees may occur in association with these other growth forms. Climates are consistently warm (seasonal daily temperatures with minimal variation), and annual rainfall is strongly seasonal, but average annual rainfall is typically >100 cm.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: Mooney et al. (1995) suggest that Tropical Dry Forest & Woodland may be defined as forest occurring in tropical regions characterized by pronounced seasonality in rainfall distribution, resulting in several months of drought. The forests that develop under such climatic conditions share a broadly similar structure and physiognomy; they mainly occur on oligotrophic, reddish soils (Oxisols, Ultisols), but may also occur on mesotrophic soils. Beyond that, they note that these shared characteristics are difficult to define with precision. They may either be deciduous or evergreen, though typically small-leaved, and either open- or closed-canopy. There are sclerophyllous evergreen broad-leaved (mesophyllous- to macrophyllous-leaved) Tropical Dry Forest & Woodland in the Brazilian-Bolivian Cerrado. But we include here only the most closed form of cerrado (i.e., the cerradão) and the more typical cerrado is placed in 2.A. ~Tropical Grassland, Savanna & Shrubland Subclass (S01)$$.
Many authors include thorn woodlands as part of a broadly defined "tropical dry forest" or "seasonally dry tropical forest" (SDTF). For example, Pennington et al. (2006) use a wide interpretation of SDTF in the Neotropics, including formations as diverse as tall forest on moister sites to cactus scrub on the driest, but they exclude the Chaco of Argentina, Paraguay and Bolivia because it receives frost. See also Oliveira-Filho et al. (2006) who include caatingas and carrascos within their broad definition of SDTF, but exclude cerrados and chaco. Here we treat 3.A.1 ~Tropical Thorn Woodland Formation (F039)$$ as a separate xeromorphic growth form-based formation that includes, in the Neotropics, caatingas, carrascos, and chaco.
Tropical monsoon forests are sometimes grouped with 1.A.2 ~Tropical Lowland Humid Forest Formation (F020)$$ as "tropical moist forest," but being deciduous with pronounced drought periods, they are better included here with 1.A.1 ~Tropical Dry Forest & Woodland Formation (F003)$$ (Whitmore 1998). Further review of the range of variation in tropical monsoon forests is needed, to clarify the transition to Tropical Lowland Humid Forest.
Many authors include thorn woodlands as part of a broadly defined "tropical dry forest" or "seasonally dry tropical forest" (SDTF). For example, Pennington et al. (2006) use a wide interpretation of SDTF in the Neotropics, including formations as diverse as tall forest on moister sites to cactus scrub on the driest, but they exclude the Chaco of Argentina, Paraguay and Bolivia because it receives frost. See also Oliveira-Filho et al. (2006) who include caatingas and carrascos within their broad definition of SDTF, but exclude cerrados and chaco. Here we treat 3.A.1 ~Tropical Thorn Woodland Formation (F039)$$ as a separate xeromorphic growth form-based formation that includes, in the Neotropics, caatingas, carrascos, and chaco.
Tropical monsoon forests are sometimes grouped with 1.A.2 ~Tropical Lowland Humid Forest Formation (F020)$$ as "tropical moist forest," but being deciduous with pronounced drought periods, they are better included here with 1.A.1 ~Tropical Dry Forest & Woodland Formation (F003)$$ (Whitmore 1998). Further review of the range of variation in tropical monsoon forests is needed, to clarify the transition to Tropical Lowland Humid Forest.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Tropical Dry Forest & Woodland is dominated by broad-leaved drought-deciduous trees or, more rarely, small-leaved (micro- to mesophyll) evergreen trees or broad-leaved (meso- to macrophyll) sclerophyllous-leaved trees (Lugo et al. 2006). Evergreen needle-leaved trees may occur in association with these other growth forms. It is a medium to high forest varying on average from 15 to 25 m tall, typically with several structural levels as complex upper canopy, several subcanopy levels of treelets and shrubs, woody vines, and an irregular low herbaceous plant stratum. Canopy heights decrease and canopy coverage tends to decrease as the climate dries until the forests are reduced to open, short-statured (5-15 m) woodlands (more rarely shorter). Included are semi-evergreen, partially sclerophyllous, semi-deciduous and deciduous, mostly dense to semi-dense forest (Whittaker 1975).
In the Neotropics the lower forest level is often dominated by colonies of clumping terrestrial bromeliads. Overall, there is a predominance in the canopy of medium-sized leaves (mesophyllous) that fall partially or almost completely in the dry season. Tall arborescent cacti can be frequent in dry semi-deciduous forest of the Neotropics and physiognomically similar arborescent succulent euphorbias in the Paleotropics. In western Brazil, eastern Bolivia, and Paraguay, this formation includes large stands of medium-low and partially sclerophyllous semi-evergreen forests or "cerradão," with characteristic adaptations to drought and fire, such as very corky bark on twisted trunks and xylopodiums (but we exclude the more typical cerrado, which is placed with 2.A. ~Tropical Grassland, Savanna & Shrubland Subclass (S01)$$).
In the Neotropics the lower forest level is often dominated by colonies of clumping terrestrial bromeliads. Overall, there is a predominance in the canopy of medium-sized leaves (mesophyllous) that fall partially or almost completely in the dry season. Tall arborescent cacti can be frequent in dry semi-deciduous forest of the Neotropics and physiognomically similar arborescent succulent euphorbias in the Paleotropics. In western Brazil, eastern Bolivia, and Paraguay, this formation includes large stands of medium-low and partially sclerophyllous semi-evergreen forests or "cerradão," with characteristic adaptations to drought and fire, such as very corky bark on twisted trunks and xylopodiums (but we exclude the more typical cerrado, which is placed with 2.A. ~Tropical Grassland, Savanna & Shrubland Subclass (S01)$$).
Floristics: No Data Available
Dynamics: No Data Available
Environmental Description: Climate: Tropical Dry Forest & Woodland occurs in areas where the air subsides near the tropics of Cancer and Capricorn and the Intertropical Convergence Zone (ITCZ) migrates north and south seasonally, producing the alternating pattern of rainfall and dryness. The average drought season varies in length from 3 to 6 months and is generally coincident with the annual lowest temperatures. Annual rainfall ranges from 100 to 200 cm (Whitmore 1998), or where the annual rainfall is <160 cm, with a period of at least 5 to 6 months receiving <10 cm, during which some or all of the trees lose their leaves (Pennington et al. 2006). The climate is warm tropical pluviseasonal, subhumid to humid.
Soil/substrate/hydrology: The substrate often includes large areas of highly weathered reddish soils with high iron and aluminum content and low mineral nutrients content, as well as frequent development of laterization. The main soil orders in the U.S. system associated with Tropical Dry Forest & Woodland are Oxisols, Ultisols and Alfisols (Soil Survey Staff 1999) [see Brady and Weil (2002) for comparison of U.S. soil orders with Canadian and FAO systems]. More rarely, they occur on mesotrophic soils. This type also occurs on limestone substrates in the Caribbean and Mesoamerica (Lugo et al. 2006).
In most areas, Tropical Dry Forest & Woodland supports seasonal regimes of fire, both natural and characteristically human induced, which can cause frequent pyrogenic secondary savannized or woodland physiognomies. Fires, in conjunction with climate, are likely to partially explain the distribution of Tropical Dry Forest & Woodland (Bond et al. 2005).
Tropical Dry Forest & Woodland tends to occur at lower elevations. However, in South America, large more-or-less isolated pockets occur in several valleys of the eastern slopes of the Andes, particularly in southern Peru and Bolivia, where they can reach altitudes up to approximately 1200 m.
Soil/substrate/hydrology: The substrate often includes large areas of highly weathered reddish soils with high iron and aluminum content and low mineral nutrients content, as well as frequent development of laterization. The main soil orders in the U.S. system associated with Tropical Dry Forest & Woodland are Oxisols, Ultisols and Alfisols (Soil Survey Staff 1999) [see Brady and Weil (2002) for comparison of U.S. soil orders with Canadian and FAO systems]. More rarely, they occur on mesotrophic soils. This type also occurs on limestone substrates in the Caribbean and Mesoamerica (Lugo et al. 2006).
In most areas, Tropical Dry Forest & Woodland supports seasonal regimes of fire, both natural and characteristically human induced, which can cause frequent pyrogenic secondary savannized or woodland physiognomies. Fires, in conjunction with climate, are likely to partially explain the distribution of Tropical Dry Forest & Woodland (Bond et al. 2005).
Tropical Dry Forest & Woodland tends to occur at lower elevations. However, in South America, large more-or-less isolated pockets occur in several valleys of the eastern slopes of the Andes, particularly in southern Peru and Bolivia, where they can reach altitudes up to approximately 1200 m.
Geographic Range: Tropical Dry Forest & Woodland is concentrated near the equator, primarily between 10° and 23°N and S latitude. It is found in three major regions: South and Central America and the Caribbean Islands; Africa (west, central and interior) and Madagascar; and the Indo-Asian Pacific (India, Southeast Asia, Indonesia, New Guinea, Pacific Islands, and northeastern Australia).
In the Neotropics, this formation occupies large areas in central South America, mainly in eastern Bolivia, central and western Brazil and eastern Paraguay. Also, in the Neotropics, these forests extend across northern South America (Venezuela) and in western Mesoamerica (Mexico to Panama), with minor extensions in western Ecuador and Peru.
In the Paleotropics, Tropical Dry Forest & Woodland potentially occupies large areas in Africa (Sudano-Zambezian and Madagascan regions), India and Southeast Asia (Indochinese region), northeastern Australia, and the Pacific Islands, but generally has been extensively degraded by human activity to semi-open woodlands and tree savannas.
In the Neotropics, this formation occupies large areas in central South America, mainly in eastern Bolivia, central and western Brazil and eastern Paraguay. Also, in the Neotropics, these forests extend across northern South America (Venezuela) and in western Mesoamerica (Mexico to Panama), with minor extensions in western Ecuador and Peru.
In the Paleotropics, Tropical Dry Forest & Woodland potentially occupies large areas in Africa (Sudano-Zambezian and Madagascan regions), India and Southeast Asia (Indochinese region), northeastern Australia, and the Pacific Islands, but generally has been extensively degraded by human activity to semi-open woodlands and tree savannas.
Nations: AS,AU,FM,GU,MP,MX,PR,PW,US,WS
States/Provinces: No Data Available
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.860270
Confidence Level: High
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
| Type | Name | Database Code | Classification Code |
|---|---|---|---|
| Class | 1 Forest & Woodland Class | C01 | 1 |
| Subclass | 1.A Tropical Forest & Woodland Subclass | S17 | 1.A |
| Formation | 1.A.1 Tropical Dry Forest & Woodland Formation | F003 | 1.A.1 |
| Division | 1.A.1.Ea Caribbean-Mesoamerican Dry Forest & Woodland Division | D099 | 1.A.1.Ea |
| Division | 1.A.1.Oc Polynesian Dry Forest & Woodland Division | D072 | 1.A.1.Oc |
Concept Lineage: No Data Available
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: = Seasonally Dry Tropical Forests (Mooney et al. 1995)
= Tropical Dry Forest (Miles et al. 2006)
= Tropical Seasonal Forest (Holzman 2008)
= Tropical broadleaf woodland: biome-type 8 (Whittaker 1975) [nearly equivalent]
= Tropical seasonal forest: biome-type 2 (Whittaker 1975)
= Tropical Dry Forest (Miles et al. 2006)
= Tropical Seasonal Forest (Holzman 2008)
= Tropical broadleaf woodland: biome-type 8 (Whittaker 1975) [nearly equivalent]
= Tropical seasonal forest: biome-type 2 (Whittaker 1975)
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