Spatial variability of soil and nutrient characteristics of semi-arid grasslands and shrublands, Jornada Basin, New Mexico

Heterogeneity of vegetation and soil properties is characteristic of semi-arid and and environments. The potential underlying cause, of the dynamics that create this spatial variability. with consequent impacts on landscape connectivity and thus ecological and ecohydrological processes. are not clearly understood. An investigation was carried out into the spatial variability of ponded infiltration rate. soil moisture. Soil-aggregate stability. vegetation cover, random roughness and nutrient content in the soil (ammonium, nitrate and phosphorus) at grassland and shrubland sites for two spatial scales in the Jornada Basin, in the northern part of the Chihuahua desert. At the plant-interplant scale. statistically significant differences exist between vegetated rind non-vegetated sites for soil moisture and infiltration rate within both shrublands and grasslands. The spatial distributions of all other parameters follow a more complex scheme at this scale. At the landscape scale, distinct differences exist for most parameters between the grasslands and the shrubland sites. Geostatistical analysis revealed that the autocorrelation lengths are not simply a function of average Shrub sizes. but may be caused by a snore complex pattern probably related to the spatial Layout of rill and inter-rill areas and other localized transfers of soil resources through the redistribution of water and wind. These results demonstrate the importance of understanding spatial linkages of processes within the landscape in understanding dryland ecosystem dynamics. Copyright (C) 2007 John Wiley & Sons, Ltd.