| Description |
Environmental temperature differences within tropical soils are a function of the total solar radiation received at the surface, and also depend on woody vegetation cover. Environmental soil temperature is recorded by carbon isotope substitutions during the formation of calcite, which is preserved in paleosols. Therefore, analysis of preserved carbonates can be used as a proxy indicator of paleotemperatures. Preliminary data from hominid sites in the Turkana Basin show that soil temperatures have been in excess of 30°C for much of the past 4-6 million years in that region. In this study two years of continual subsurface soil monitoring were conducted at 28 sites within and around Kenyan National Parks and we present annual and seasonal averages of soil temperatures at a depth of 25 cm within different microclimates, which should approximate the absolute formation temperature of soil carbonates in present day tropical soils. In addition, we use an iterative method to solve the heat diffusion equation to estimate the soil surface temperature. In the tropics, where the solar angle is high throughout the year, observed environmental temperature differences over small spatial distances are as high as 30°C in the most extreme contrasts between grassland and forested microclimates. Average soil temperatures at 25 cm depth are highest in the Turkana basin where annual and seasonal averages are in excess of 30°C. These results are consistent with the paleotemperature measurements, indicating that temperatures are as hot today as they have been over the past several million years. |
