Vegetation tends to reduce aeolian transport of surface sediments. However, not all vegetation types act in the same way to do so. In general, the more land cover the less erosion will occur; thus grasslands should experience less aeolian erosion than shrublands, which are characterized by patchy cover with open intershrub spaces. Five major ecosystem types are described at the Jornada Basin Long- Term Ecological Research site (Jornada LTER) in south-central New Mexico, USA: mesquite dunes, black grama grasslands, creosote bush shrublands, tarbush alluvial flats, and grass-dominated playas. Here we investigate the dry particle size distribution of material collected by BSNE aeolian particle samplers in 2006 in these five different vegetation types, allowing us to estimate dust production at sites with different land cover. As mesquite and creosote bush continue replacing historical grasslands at Jornada, understanding the characteristics of wind erosion will be important for future management plans. The mesquite sites had the greatest horizontal mass flux, although with substantial variation. M-NORT, a site with large sand dunes, had much greater mass flux than other mesquite sites. For most sites, the dry particle size distributions at 5, 10 and 20 cm heights above the land surface were very similar, dominated by sand, while the distributions for 50 and 100cm heights shifted towards a greater percentage of silt and clay (dust) particles. The playa site and one of three tarbush sites stand out as having the greatest percentages of dust particles, between 33- 52 % of total mass at all heights. After taking into account the differences in mass flux, the mesquite site with the larger dunes and the playa site had the greatest flux of dust-sized particles. These two sites demonstrate different mechanisms of producing dust at the Jornada LTER. The playa is a relatively major dust producer due to its high proportion of fine particles, whereas the mesquite site is a major dust producer because of its far greater overall mass flux. Considering the differential mass flux of aeolian particles produced by each vegetation type, the greatest total mass of dust per unit area at the Jornada LTER occurs at the playa site, followed by the mesquite site with large dunes and tarbush, while creosote bush, grassland, and the other two mesquite sites produce the least dust. Since mesquite dunes cover about 34% of the Jornada Basin, we conclude that mesquite dunes have the potential to produce the most dust from the area overall, with playas and tarbush-dominated alluvial flats (which cover about 7% each) having the potential to emit large amounts of dust if the conditions are correct. These results suggest that the continuing replacement of grasslands with shrubs will likely increase dust emissions from the Jornada Basin.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 0305 Aerosols and particles (0345;
- 1631 Land/atmosphere interactions (1218;
- 3322 Land/atmosphere interactions (1218;