Geographically and hydrologically isolated, ephemeral playa wetlands are ubiquitous features of the High Plains. Although playas are important landscape elements, few systematic inventories have been conducted, particularly on the Northern and Central High Plains. A comprehensive Geographic Information Systems database was created using versatile inventory techniques applicable for a variety of regions and wetland mapping projects. Utilizing several geospatial data sources, including highresolution aerial imagery, digital raster graphics, and SSURGO soils data, 22,045 playas were identified in Kansas-more than doubling previous estimates. Playa surface area ranges from 0.03 ha to 188 ha, with a mean area of 1.65 ha. More than 80% are smaller than 2 ha and only about 400 playas (1.8%) are larger than 10 ha. Results indicate that previous playa inventories failed to identify most small playas, particularly those less than 2 ha because data sources were not of sufficient resolution. Additionally, playa identification criteria have not been consistent for previous playa inventories conducted throughout the High Plains. It is essential that criteria to identify playas are consistently applied in all playa studies to facilitate comparison and to establish trends for various playa attributes across the entire High Plains.
Playas are small, ephemeral wetlands found throughout semiarid and arid regions around the world. Lunettes are dunes that form downwind of some large playas. Two playa-lunette systems on the High Plains were investigated to reconstruct paleoenvironments during playa-lunette system evolution. Both playa-lunette systems are composed of sediment spanning >40 k.y., with earliest deposits accumulating during at least marine isotope stage (MIS) 3, and possibly starting as early as MIS 5. The Gilman Canyon Formation pedocomplex, dating between 42 and 28 ka, dominates this period and is ubiquitous throughout the playa-lunette systems. Climate during MIS 3 was similar to modern, with warm temperatures, low effective moisture, and playa fl oors exposed long enough to allow pedogenesis. During MIS 2, climate was relatively cool with higher effective precipitation, and playas were inundated for longer periods. The regionally expressed Brady Soil of the Pleistocene-Holocene transition caps these deposits and dates between 11.8 and 9.4 ka. During the PleistoceneHolocene transition, climate warmed, yet moisture availability remained relatively high. Several distinct shifts in δ 13 C identify rapid climate changes associated with the Bølling-Allerød-Younger Dryas chronosequence. Warming continued into the Holocene, though moisture availability was highly variable. Holocene soils are common and date between 8.3 and 3.6 ka. Playa-lunette system stratigraphy represents a continuum of the upland loess sequence, though deposits are altered by playa hydrology. Geomorphic processes alternated between dissolutionand fl uvial-eolian-driven processes as climate changed and playas developed. Due to the aggradational environment and sensitivity of these systems, high-resolution records of environmental change throughout their evolution are preserved.
Holocene environmental change is poorly characterized throughout much of the High Plains. Playa wetlands are sites with appreciable potential for reconstructing environmental change because of their environmental sensitivity. Radiocarbon, litho- and magneto-stratigraphic, and stable carbon isotope (δ13C) data for four playas on the Kansas High Plains indicate significant change occurred throughout the Holocene, which had profound impacts on playa ecosystem functions (e.g. groundwater recharge, surface water storage, and habitat). Minimum δ13C values and buried soils observed during the Pleistocene–Holocene transition suggest sufficient moisture to support vegetative cover and promote pedogenesis. Low magnetic susceptibility, rapid increase in δ13C, and weak pedogenic alteration in overlying deposits suggest early Holocene aridity with increased landscape instability and sediment deposition. Early to middle Holocene stratigraphy transitioned from loess with little pedogenic modification into overlying buried soils; δ13C values indicate playa vegetation was composed of as much as 90% C4 plants. Maximum magnetic susceptibility and buried soils in late Holocene deposits indicate sufficient moisture to support vegetative cover and promote pedogenesis. The Pleistocene–Holocene transition was a cool, moist period in which sediment accumulation rates in playas were low and ecosystem functions were optimal. Throughout much of the early to early–middle Holocene, playas were subaerially exposed, sediment accumulation outpaced soil formation, and ecosystem functions were inhibited by lack of moisture. From the middle to late Holocene, the climate returned to more mesic conditions, sediment accumulation and soil formation were in near equilibrium, and the ability of playas to perform ecosystem functions increased.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.