Application of a soil-water balance model to evaluate the influence of Holocene climate change on calcic soils, Mojave Desert, California, U.S.A.

摘要

We used a process-based soil-water balance model to simulate the downward flux of soil-water under varied conditions of climate, vegetation, and soil texture to determine the potential impact of episodic periods of wetter (pluvial) climate during theHolocene on calcic soils in the Mojave Desert that have a bimodal distribution of carbonate. Daily weather data associated with a relatively "wet" climate (years with extreme increases in annual rainfall, approx 33 cm/yr) and "dry" climate (historic average annual rainfall, approx 15 cm/yr) was used to simulate the affects of Pleistocene and Holocene climate change on soil-water balance. Linkages among atmospheric circulation patterns, regional increases in precipitation, and historic flooding in the Mojave Desert, California, suggest that historic wet years provide an analog for wetter climates that occurred during the last glacial period (latest Pleistocene) and episodically during Holocene periods of pluvial activity. Modeling results indicate thatsoil-water balance for dry and wet years strongly corresponds with the upper and lower zones of carbonate accumulation respectively. Soil-water only reached the lower zone of carbonate during a wet year when extreme increases in winter/spring storm activity resulted in a significant increase in precipitation and the downward flux of soil water. The linkage between increases in frontal storm activity and pluvial events suggests that the shallow zone of the bimodal distribution of carbonate is a result ofperiods of significant decreases in winter and spring rainfall and not primarily due to increases in Holocene temperature or the development of clay-rich horizons. Calculation of carbonate solubility and accumulation rates suggests that the bimodal distribution of carbonates in soils may have also been impacted by episodic periods of extreme increases in precipitation associated with perennial lakes during the Holocene,, Results suggests that much of the carbonate in the upper 75 cm of Pleistocene soils may have accumulated during the late Holocene rather than throughout the entire Holocene.