Spatial heterogeneity in Chihuahuan Desert vegetation: implications for sampling methods in semi-arid ecosystems

Patchiness of above-ground vegetation, such as that in semi-arid grasslands and shrublands, can pose problems in sampling plant cover, biomass and pro ductivity. We present a method of measuring above-ground plant biomass and production that can be applied consistently among vegetation types and that generates seasonal, spatially-explicit results. Results from 15 sites with in the Jornada Basin (Chihuahuan Desert, New Mexico, U.S.A.) confirm consid erable patchiness and non-normal distributions of plant biomass, even in gr asslands. However, tests of adequacy of sample size and of sample error ass ociated with the regression-based estimates of biomass confirmed that the e stimates of above-ground net primary productivity are sufficiently precise to be useful in comparisons of both shrub-dominated and grassland sites. (C ) 2001 Academic Press.