Thursday, August 6, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Douglas I. Moore1, Esteban H Muldavin2, Scott L. Collins1 and Karen R Wetherill2, (1)Department of Biology, University of New Mexico, Albuquerque, NM, (2)Biology, University of New Mexico, Albuquerque, NM
Background/Question/Methods The ongoing response to fire on aboveground net primary productivity (ANPP) in a southwestern desert grassland is being studied. In June, 2003, a prescribed burn was applied to a large area (5,000 ha) of desert grassland and shrubland on the east side of the Sevilleta National Wildlife Refuge in central New Mexico. The area was dominated by black grama (Bouteloua eriopoda), blue grama (Bouteloua gracilis), and creosotebush (Larrea tridentata) in pure and mixed stands.The summer growing season following the fire was one of the driest on record so that little or no growth occurred on either burned or unburned sites. In the spring of 2004, paired, side-by-side ANPP plots were established in burned and adjacent unburned sites representing the major community types: 1) black grama dominated, 2) a mixture of black and blue grama, and 3) a creosotebush stand with an understory of black grama. Each plot contained of 40 permenant 1-m2 quadrats These quadrats have been measured 2 times each year during the subsequent 5 years. Dimensions of all species in each were measured with seasonal harvests of those species nearby to develop weight-to-volume regressions.
Results/Conclusions While the fire generally removed creosote bush canopies, the large majority of plants re-sprouted from root crowns. Among grasses, black grama mortality was high on burned plots at all sites. Other grasses were not significantly impacted by the fire and recovered quickly. Initially, increased forb production on the Black Grama site and increased blue grama production on the mixed Blue Grama-Black Grama site compensated for the reduced production in black grama in these sites. There was no similar compensatory effect on the Creostebush/Black Grama site. Now five years after the fire the ANPP is still lower on the burned plots than on the control plots. This seems to be primarily due to the slow black grama recovery which is still only at about half of the production of that on the control plots. Annual and seasonal variability in precipitation has had variable effect on response of the 3 mixed plant communities on both burned and control plots
