XVI International Botanical Congess

In order to derive models that can accurately estimate rainfall variables from fossil leaves in tropical Africa, leaf form and rainfall variables were collected from modern sites across the equatorial region where annual amount and seasonality of rainfall are the main factors determining vegetation structure and physiognomy. Multiple regression models, mainly dependent on the positive correlation between leaf area and rainfall, were derived. The African regression models are similar to those derived from another low to mid-latutude dataset sampling leaf area and annual rainfall, and indicate the leaf size-rainfall relationship is robust. The African models were used to estimate Miocene rainfall at 3 sites in the Tugen Hills, Kenya, from fossil leaves. At 12.6 Ma, a moist forest had 1000-1500mm mean annual rainfall and 0-3.8 dry months, at ~9 Ma, a dry woodland had 845-1244 mm mean annual rainfall and 3.3-6.9 dry months, and at 6.8 Ma, a dry forest had 870-1281 mm mean annual rainfall and 0-3.7 dry months.