|Herrick, Jeffrey - Jeff|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/5/2003
Publication Date: 12/5/2003
Citation: Yao, J., Peters, D.C., Gibbens, R.P., Havstad, K.M., Herrick, J.E. 2004. Spatial and temporal variation in desertification due to stressors at multiple scales [abstract]. LAND Open Science Conference, December 2-5, 2004, Morelia, Mexico. p. 32.
Technical Abstract: Desertification, in particular, shrub invasion into former grasslands, is a worldwide and well-known phenomenon in arid and semiarid areas; however, detailed quantification of spatial and temporal variation in desertification is rare. A number of interacting factors have been implicated for desertification, including livestock grazing, drought, herbivory by small animals, reduction in fire frequency, and global climate change; but, the exact role of these factors remains unclear. Using the long-term datasets collected at the Jornada Experimental Range, New Mexico, USA, we examined spatial and temporal variation in shrub invasion and grass persistence and identified the factors resulting in the variations. The dependent variables, basal area and annual growth of perennial grasses, were measured in 105 1 x 1 m permanent chart quadrats set up between 1915-32 and monitored annually until 1979, and periodically since that time. The explanatory variables included factors at both the local and landscape scales. The local factors considered were soil texture, depth to the top of caliche layer, precipitation, and micro-topography; the landscape factors were elevation, pasture stocking rate, and distance to historic shrublands. Our results showed that not all grasslands disappeared after the severe drought of 1950s: upland grass species (black grama, mesa dropseed, and threeawns) survived in a few quadrats and playa grass species (tobosa and burrograss) recovered to near pre-drought level in many quadrats. Spatial and temporal variations in grass persistence were results of interactions between climatic and landscape factors: both local and landscape factors affected grass persistence, but factors related to grass persistence varied with species and time period during 1915-2001. Our results increase our understanding of desertification in the face of global change and provide important information for the prediction of land cover change in arid and semiarid areas in the future.