Dry Season
High evapotranspiration rates are in part due and lead to dry fast draining soils during this part of the year. This season is distinct and occurs for at least three consecutive months throughout the year, but can occur for up to ten months in some areas. Fires are more likely to occur during the dry season, occurring less often in areas with less dense leaf litter. As underbrush grows, so does the risk of fire and because of it trees in certain regions prone to fire have adapted by developing thicker bark and post-fire sprouting mechanisms, allowing them to persist through the fires randomly experienced by dry forest during this period. Although certain areas have become resistant to stochastic fires, areas which have been protected from fire in the past through environmental barriers, now because of grassland burning and forest fragmentation are at a higher risk of damage from fire.
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Wet Season
This season is distinct and can last anywhere from five to eight months throughout the year. Average precipitation for this biome is 250 mm to no more than 2000mm of rainfall, with high variability between years. With such extreme variability of precipitation, organisms are at higher risk of local extinction, but because of this have developed adaptations to deal with the constantly changing environment. Tree's evolved deciduous mechanisms, dropping their leaves at the end of the wet season in order to lock in all the moisture they absorbed during the rainy season. Because of the high amounts of rain experienced during the wet season, plants fruiting is increased during this period, and such dispersal by animals, such as birds and large mammals is at its highest rate during this period.
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Temperature
Tropical dry forest experience a high mean annual temperature that is usually around 25 degrees Celsius. High annual temperatures are due in part to tropical dry forests location adjacent to the equator, usually within 10* to 20* Latitudes North and South. Mean annual temperatures have high levels of variance between areas with different elevations, with all else held constant. Although there are differences in temperature among areas due to these elevation differences, The temperature is one of the few variables which does hold relatively steady throughout the year. This fact has lead scientists to speculate that global climate shift may have a pronounced effect on all trophic levels of this ecosystem.
Sources:
- Figure 1 : http://w3.marietta.edu/~biol/biomes/images/tropseas/180dimg_1951.jpg
- Figure 2 : http://w3.marietta.edu/~biol/costa_rica/santa_rosa/images/santa_rosa_7602.jpg
- Figure 3 : http://d2ouvy59p0dg6k.cloudfront.net/img/forest_mexico_35116_357295.jpg
- (J. Alan Pounds, Michael P. L. Fogden & John H. Campbell (1999) 'Biological response to climate change on a tropical mountain', Nature, 398, pp. 611-615 (15 April 1999) doi:10.1038/19297
- (GRIZ, L.M.S. and MACHADO, I.C.S. (2001) ‘Fruiting phenology and seed dispersal syndromes in caatinga, a tropical dry forest in the northeast of Brazil’, Journal of Tropical Ecology, 17(2), pp. 303–321. doi: 10.1017/S0266467401001201.)
- (Pinard, M.A. and Huffman, J. (1997) ‘Fire resistance and bark properties of trees in a seasonally dry forest in eastern Bolivia’, Journal of Tropical Ecology, 13(5), pp. 727–740. doi: 10.1017/S0266467400010890.)
- (Otterstrom, S. M., Schwartz, M. W. and Velázquez-Rocha, I. (2006), Responses to Fire in Selected Tropical Dry Forest Trees1. Biotropica, 38: 592–598. doi:10.1111/j.1744-7429.2006.00188.x)