World peat occurrence and the seasonality of climate and vegetation

Abstract

The climatic controls on present-day peat formation are examined in order to develop a uniformitarian tool for refining paleoclimate studies, and to create a retrodictive model for the coals of the geologic record. A peat database has been compiled for the world and the resulting patterns are compared with aspects of precipitation and temperature drawn from a gridded data set. Precipitation continuity through the annual cycle is important for biologic productivity in the terrestrial realm. It is expressed in terms of the number of months with average precipitation above 40 mm. Temperature is limiting at higher latitudes where the potential growing season may be defined by the number of months with mean temperature exceeding 10°C. A map predicting the growing season has been constructed from these rainfall and temperature statistics which compares very well with actual vegetation persistence through the year as measured directly from satellite instruments. However, biologic production will not result in peat accumulation unless groundwater levels are maintained through the growing season. Our peat prediction map therefore shows the percentage of time that precipitation occurs during the potential growing season. Present-day peat accumulations are well predicted by this map.