干旱区生态环境知识资源中心

We evaluated relationships between soil depth and vegetation standing crop components over a 3-year period on 3 adjoining pastures with similar size, vegetation, and soils on the Chihuahuan Desert Rangeland Research Center in south central New Mexico. Soils on our study pastures are primarily light sandy loams varying from a few centimeters to 1 m or more in depth underlain by a calcium carbonate layer. Study pastures were ungrazed in 1995 and 1996 and conservatively grazed in 1997. Linear regression equations using perennial grass standing crop (kg ha(-1)) and honey mesquite (Prosopis glandulosa Torr.) cover (%) as dependent variables and soil depth as the independent variable were significant (P <0.05) and similar for all 3 pastures. Deep soils had low perennial grass standing crop and high mesquite cover, while the opposite occurred for shallow soils. Within shallow soils, honey mesquite and perennial grass standing crop were not correlated (P = 0.78, n = 18), but a significant (P = 0.01) negative correlation occurred on deep soils (r = -0.67, n = 15). Perennial grass standing crop differed greatly among years when data were pooled across pastures, ranging from 64 kg ha-1 in 1995 to 248 kg ha(-1) in 1997. Our study shows that soil depth has a major influence on Chihuahuan Desert vegetation. Perennial grasses are favored by shallow sandy soils while deep sandy soils favor honey mesquite.