Sediment accumulation and sedimentation rates in playas on the High Plains of western Kansas, USA

Grassland ecosystems are some of the most modified ecosystems in the world, largely due to conversion to cropland, and the High Plains of the central United States is no exception. Playa wetlands are ubiquitous features of the High Plains and have experienced increased sediment accumulation, which is the primary cause of reduced playa ecosystem function. Seven playas on the High Plains of western Kansas, five with cropland-dominated watersheds and two with grassland-dominated watersheds, were examined to quantify the amount of recent (past similar to 100-175 yr) sediment accumulated within playas and to establish chronologies of playa filling. Thiduiesses of recent sediment were determined in the field, and soil cores were extracted from study playas. Four playa cores were analyzed for Pb-210 to establish the chronology of recent sediment accumulation and sedimentation rates. Chronologies of pre-agricultural sediments and sedimentation rates were calculated by C-14 dating of buried soils preserved within playa cores. Radiocarbon ages indicate playa stratigraphic records span the Holocene and that these playas have persisted on the landscape since at least the Late Pleistocene. Long-term, natural sedimentation rates were highest during the Pleistocene-Holocene transition and early Holocene, at similar to 2-4 cm/century. During the middle and late Holocene, sedimentation rates averaged similar to 1 cm/century. Cropland playas accumulated similar to 10-15 cm of recent sediment at average rates of similar to 6.5-10 cm/century, while grassland playas accumulated only similar to 2 cm of recent sediment Conversion of watersheds to cropland has greatly accelerated sediment accumulation within playas, which is generally resulting in a decline in critical playa ecosystem functions. (C) 2019 Elsevier B.V. All rights reserved.