Influences of climate and life on hillslope sediment transport.

Hillslopes constitute the majority of Earth's land surface area and dominate the supply of sediment to rivers. Hillslope sediment transport is commonly modeled with a rate law that depends on slope and a rate coefficient, D, that is understood to represent the intensity of transport mechanisms. Although many transport mechanisms are related to water and biota, it is unclear whether D varies predictably with climate and life. We compiled previous estimates of D from around the world and also made new estimates for additional sites. The compilation reveals an overall trend in which D increases strongly with increasing moisture among relatively dry sites and less strongly with increasing moisture among relatively wet sites. Vegetation type has a secondary effect on D among drier sites, with D increasing from deserts to grasslands to forests, but not among wetter sites. These trends suggest that the establishment of life in a landscape substantially accelerates soil creep, whereas differences in biological communities among sites with abundant moisture have a relatively small effect on creep. [ABSTRACT FROM AUTHOR]