Biological Soil Crusts and Hydrology in North American Deserts
Precipitation that reaches the Earth’s surface either remains on the surface or infiltrates into the soil profile. Water remaining on the surface evaporates or runs off into bodies of water. Water that enters the soil may be stored as groundwater, may mov
- PDF / 86,698 Bytes
- 11 Pages / 439.37 x 666.14 pts Page_size
- 9 Downloads / 180 Views
24.1 Introduction Precipitation that reaches the Earth’s surface either remains on the surface or infiltrates into the soil profile. Water remaining on the surface evaporates or runs off into bodies of water. Water that enters the soil may be stored as groundwater, may move laterally through the soil to channels, bodies of water, or springs, or may be returned to the atmosphere through evaporation and/or transpiration. Numerous physical, biological, and chemical characteristics of the soil affect the partitioning of water between infiltration and runoff. Soil properties also govern the ultimate fate of infiltrated water and determine the erodibility of the soil when subjected to surface runoff. This chapter examines the effects of biological soil crusts on infiltration, runoff, soil moisture, and soil erosion by water in North America.
24.2 Infiltration and Runoff Infiltration and runoff are closely related and inversely proportional, i.e., as more water infiltrates into the soil, less runs off. On loamy soils of the sagebrush steppe in the northern Great Basin Desert, infiltration rate is significantly related to soil surface morphology, with more rapid infiltration on the rougher surfaces of shrub coppices and slower infiltration on the flatter surfaces in the interspaces between the shrubs (Blackburn 1975; Pierson et al. 1994). Moss-dominated biological soil crusts are considerably more abundant on shrub coppices than in the interspaces (Eckert et al. 1978; Pierson et al. 1994), leading to the possible conclusion that the crusts govern the infiltration process in this area. While compelling, this conclusion may not be entirely justified based on these data alone. Although cover of biological soil crusts is positively correlated with infiltration rate in the sagebrush steppe (Spaeth et al. 1994), soil characteristics other than biological crusts also vary between Ecological Studies, Vol. 150 J. Belnap and O.L. Lange (eds.) Biological Soil Crusts: Structure, Function, and Management © Springer-Verlag Berlin Heidelberg 2001
328
S.D. Warren
the shrub coppices and the interspaces, including greater litter cover under the shrubs (Eckert et al. 1978) and the presence of vesicular soil horizons in the interspaces (Blackburn 1975; Pierson et al. 1994), which are well known for impeding infiltration (Dobrowolski 1994). In the pinyon-juniper woodlands of the Colorado Plateau, the infiltration rate of ponded water on intact moss-encrusted sandy soil was significantly faster than on adjacent areas where the crusts had been destroyed (Rushforth and Brotherson 1982; Brotherson and Rushforth 1983). Lichen and algal crusts slowed the infiltration rate of ponded water compared to disturbed biological crusts. However, when the infiltration characteristics were measured with simulated rainfall designed to approximate brief summer cloudbursts, the downslope spread of water on both types of biological crusts was significantly less, and the depth of water penetration was significantly greater than on the disturbed crust, implying
Data Loading...
