| Popis: |
Cloud cover, solar radiant flux density, temperature and relative humidity regimes were studied along the altitudinal gradient of Serrania de Macuira (865 m), Guajira, Colombia. The regional climate at Macuira is characterized by the presence of small cumulus clouds, persistent trade winds from the northeast, and low and highly seasonal rainfall. During the day time, the clouds remain above the highest peaks of the Serrania, decreasing radiation, air temperature, relative humidity and evaporation in relation to the lowlands. At night the clouds come into contact with the forest, supplying water by means of mist and fog interception. Owing to this pattern, the cloud forest trees on top of the mountain experience low air saturation deficits only during the night, early morning and late afternoon. This shows that the low stature of trees in this forest is not the result of an uninterrupted low saturation deficit that would inhibit mineral pumping by means of transpiration. The soil temperature gradient in Macuira was steeper than that reported for higher and more massive mountains of the tropics. This steeper gradient is the result of high temperatures in the dry lowlands around the mountain. Strong winds seem to be the cause of the reduction in tree stature in the more exposed slopes and ridges, but are not the general explanation for small trees in this forest. Wind speed is much lower in gullies than on ridges and slopes, nevertheless, trees are also small. We think that the climatic factor that has a more pronounced effect on the physiognomy of this forest is cloud water. The effects of high water content of the soil on soil chemistry, would be worth investigating as a general explanation for the small stature of these trees. |
