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ARS Home » Plains Area » Las Cruces, New Mexico » Range Management Research » Research » Publications at this Location » Publication #185289
Title: MULTI-SCALE FACTORS AND LONG-TERM RESPONSES OF CHIHUAHUAN DESERT GRASSES TO DROUGHT

Author
item YAO, JIN - NEW MEXICO STATE UNIV
item Peters, Debra
item Havstad, Kris
item GIBBENS, ROBERT - RETIRED USDA-ARS
item Herrick, Jeffrey - Jeff

Submitted to: Landscape Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2006
Publication Date: 9/15/2006
Citation: Yao, J., Peters, D.C., Havstad, K.M., Gibbens, R.P., Herrick, J.E. 2006. Multi-scale factors and long-term responses of Chihuahuan Desert grasses to drought. Landscape Ecology. 21:1217-1231.

Interpretive Summary: We used long term data (1915-2001) of perennial grass cover from 1 m2 quadrats combined with more recently collected field data and spatial databases from the Jornada Experimental Range to assess temporal trends in cover and the relative importance of three factors to explaining spatial variation in perennial grass cover: (1) broad scale factors at the landscape unit scale (rainfall, livestock grazing, elevation, soil type), (2) fine scale factors at the plant scale (soil texture, soil depth), and (3) indicators of spatial processes at patch scales (micro-topography, distance to historic shrub populations or watering points for livestock, topography) of five important grass species from two topographic positions before, during, and after the extreme and widespread drought of the 1950s. Different factors were related to cover of each species in each time period. Rainfall and stocking rate were only related to grass cover in the pre-drought period whereas only the fine scale factor of soil texture was related to cover of two upland species during the drought. Water redistribution was important in the pre- and post-drought period. Another spatial process, seed dispersal based on distance from historic shrub populations, was important to cover of the dominant grass in uplands prior to the drought (black grama) and to persistence of this species through time. Our results demonstrate the importance of local processes during the drought, and spatial processes before and after the drought with different relationships for different species. This information can be used to manage these systems differently during a drought as compared with non-drought periods.

Technical Abstract: Factors with variation at broad (e.g., climate) and fine scales (e.g., soil texture) that influence local processes at the plant scale have often been used to infer controls on spatial patterns and temporal trends in vegetation. However, these factors can be insufficient to explain spatial and temporal variation in grass cover for arid and semiarid grasslands during an extreme event, such as drought, that promotes woody plant encroachment. We used long term cover data (1915-2001) combined with more recently collected field data and spatial databases from a site in the northern Chihuahuan Desert to assess temporal trends in cover and the relative importance of three factors to explaining spatial variation in perennial grass cover: (1) broad scale factors at the landscape unit scale (rainfall, livestock grazing, elevation, soil type), (2) fine scale factors at the plant scale (soil texture, soil depth), and (3) indicators of spatial processes at patch scales (micro-topography, distance to historic shrub populations or watering points for livestock, topography) of five important grass species from two topographic positions before, during, and after the extreme and widespread drought of the 1950s. Different factors were related to cover of each species in each time period. Broad scale factors (rainfall, stocking rate) were only related to grass cover in the pre-drought period whereas only the fine scale factor of soil texture was significantly related to cover of two upland species during the drought. Spatial processes associated with the redistribution of water (microtopography) were important for different species in the pre- and post-drought period. Another spatial process, seed dispersal based on distance from historic shrub populations, was important to cover of the dominant grass in uplands prior to the drought (B. eriopoda) and to persistence of this species through time. Our results demonstrate the importance of local processes during the drought, and spatial processes before and after the drought with different relationships for different species.