Sustainability and Biodiversity of Tropical Ecosystems

Climate
Topography
Hydrology
Soils

Climate (Sanford et al. 1994)

• Defined by the intertropical convergence zone (equatorial trough or the doldrums); trade winds converge
• Major atmospheric patterns: equatorial low pressure trough, easterly waves from trades winds, and polar trough
• Hurricanes are infrequent (Dunn and Miller 1964)
• Similar to the Amazon and Ornico basins in South America, Central American isthmus, Congo, Niger, and Zambezi basins of central and western Africa, and Indo-Malay-Borneo-New Guinea archipelago
• Mean annual daily temp. 18 to 24 C;  monthly mean temp = 25.8 C; Range (36.6 to 16)
• Greater diurnal than seasonal variation: . Diurnal range is 6-12 C; monthly change <3 C
• Precipitation >2,000 mm/year, no month receives < 100 mm/month. Strong orographic effects (Figure 1).
• Precipitation at La Selva since 1963: mean = 3,962 mm/yr (Range: 2,605 to 5,659). Bimodal distribution: peaks in June/July and November/December, March is typically the driest month
• Long term average of 12 days between precipitation events has been recorded.  The maximum time between significant rainfall is 30days.
•  Nearly 50% of the precipitation is returned to the air via evapotranspiration.
• Air moisture content 19x10^-6 gm cm^-3
• Solar radiation: 17.5 MJ/day in October to 26.6 MJ/day in April. Related to rain/cloud cover

 



Figure 1  Average weekly precipitation from the Bridge Station at La Selva, 1982-1991 (Sanford et al. 1994)

Topography

• Mainly below 100 m with 11% slope in upper parts and 1-3% slope in lower parts (Figure 2)


Figure 2  Contour map of La Selva.  Shaded areas are 10 m countour intervals.  The lightest shad represents 20-29 m and the darkest is 120-129 m elevation.  (Sanford et al. 1994).

Hydrology

•  The aquatic systems within this region are diverse with respect to their flood stage behavior, water source chemistry, and amount of change between water quality at the headwaters compared to that at the mouth.
• Many of the streams flow through unbroken forest as well as areas that have been disturbed to varying degrees.
• Overall nutrient concentrations are high in nitrogen as well as phosphorous.
• Major rivers are the San Juan (border with Nicaragua), San Carlos, and Sarapaqui

Figure 3 Sarapiqui canton and districts (Butterfield 1994)

Soils (Sollins et al. 1994)

• Soils range from red, infertile, and harden irreversibly upon drying to young, very fertile, alluvial soils
• Soil types based upon USDA Soil Taxonomy (1990)
• At La Selva: Entisols (young mineral soils), Inceptisols (youthful soils), and Ultisols (well weathered soils)(Figure 5)
• List of physical and chemical soil properties at La Selva in Sollins et al. 1994
• Low pH, high aluminum, low cation exchange capacity, and low extractable P (Berstsch 1986)
• Nitrogen used in agriculture (Montagini 1994)

 



Figure 4  Geological features of La Selva (Sanford et al. 1994).
 
 



Figure 5 Soil classisification of La Selva (OTS)


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References

Berstsch, F.H. 1986. Manual para interpretar la fertilidad de los suelos en Costa Rica. Report, Escuela de Fitotecnia, Universidad de Costa Rica, San Jose.

Butterfield, R.P. 1994. The Regional Context: Land Colonization and Conservatiion in Sarapiqui. In L.A. McCade, K.S. Bawa, H.A. Hespenheide, and G.S. Hartshorn. La Selva: Ecology and Natural History of a Neotropical Rainforest. The University of Chicago Press, Chicago.

Dunn, G.E. and B.I. Miller. 1964. Atlantic Hurricanes. Louisiana State University Press, Baton Rouge.

Montagini, F. 1994. Agricultural Systems in the La Selva Region. In L.A. McCade, K.S. Bawa, H.A. Hespenheide, and G.S. Hartshorn. La Selva: Ecology and Natural History of a Neotropical Rainforest. The University of Chicago Press, Chicago.

Organization for Tropical Studies. La Selva Geographic Information System.

Sanford, R.L., P. Paaby, J.C. Luvall, an dE. Phillips. 1994. Climate, Geomorphology, and Aquatic Systems. In L.A. McCade, K.S. Bawa, H.A. Hespenheide, and G.S. Hartshorn. La Selva: Ecology and Natural History of a Neotropical Rainforest. The University of Chicago Press, Chicago.

Sollins, P., F. Sancho, R. Mata, and R.L. Sanford. 1994. Soils and Soil Process Research. In L.A. McCade, K.S. Bawa, H.A. Hespenheide, and G.S. Hartshorn. La Selva: Ecology and Natural History of a Neotropical Rainforest. The University of Chicago Press, Chicago.

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