Document: LAU-3-69-49

Effects of plant removals on soil surface erosion in a Chihuahuan Desert shrubland.

HUENNEKE, L.F.* ¹, M.BUONOPANE ¹, L.BOTHERN ¹ and J.E.HERRICK ²

New Mexico State University, Las Cruces, NM 88003, USA ¹
USDA-ARS Jornada Experimental Range, Las Cruces, NM, USA ²

Abstract:
Humans are dramatically altering the patterns of biological diversity in semi-arid ecosystems worldwide, in particular by altering the relative abundance of different growth forms (shrubs vs. perennial grasses) and by reducing the numbers of species within growth forms. We are exploring the impact of reduced plant diversity in experimental plots of creosotebush (Larrea tridentata) shrubland at the Jornada Basin LTER site near Las Cruces, NM, USA. In 1995, eight treatments of varying severity of plant community alteration were imposed on 25 m by 25 m plots (6 replicates of each treatment); treatments range from no removals to extreme simplification of the perennial community (one shrub species, one grass species, one succulent, etc.). These treatments have been maintained since 1995. We have monitored soil erosion and sediment movement within these plots since spring 1996, by collecting sediment in pans at the downslope edge of each plot. Fine materials (particle diameter <2 mm) dominate total soil movement (by weight), although larger particles are transported in this system especially during the summer-fall season of intense episodic rainfall. Fine particle movement is higher in shrub-removal and grass-removal treatments than in controls during some seasons, especially in the summer. No statistically significant differences were detected during other seasons. Location on the slope with respect to local channels or arroyos contributes significantly to variation in the amount of material moving within a plot, as does the nature of vegetative cover and soil surface characteristics in the immediate vicinity of a collecting pan. Our results suggest that the relationship between plant community structure and soil erosion rates is best examined at the scale of local patches.

Keywords: plant cover, plant diversity, soil erosion, Larrea tridentata, Chihuahuan Desert, Jornada LTER

This abstract is being presented at: 10:30 AM in session:
Poster Session #12: Disturbance Ecology.