Desert wildfire impacts on plant community function
2015
Horn, Kevin J. | Wilkinson, Joseph | White, Steven | St. Clair, Samuel B.
Dramatic increases are occurring in the size and frequency of wildfires in arid ecosystems. The objective of this study was to characterize the composition of plant communities after desert wildfires and evaluate plant functional responses to post-fire environments. Plant community characteristics and functional traits were assessed from 2009 to 2011 along paired burned–unburned transects of multiple independent fires that occurred in the Mojave Desert in 2005. We measured plant community composition and diversity; xylem water potential; and foliar nitrogen, phosphorus, and non-structural carbohydrates of Yucca brevifolia and Larrea tridentata. Fire effects on the plant community remained evident on burned landscapes 6 years post-fire with 81, 86, and 42 % less shrub abundance, cover, and diversity. Plant functional traits had neutral to positive responses to burned landscapes that varied by species and season. Plants on burned and unburned landscapes had similar xylem water potentials following wetter periods but were significantly better in burned landscapes during dry periods and were more pronounced for L. tridentata than Y. brevifolia. Both species tended to maintain higher foliar nitrogen and phosphorus concentrations in burned areas across seasons. Post-fire conditions increased non-structural carbohydrates in L. tridentata leaves in summer and fall periods. L. tridentata had 50 % greater canopy leaf area index in burned landscapes compared to unburned areas. Improvements in water and nutrient relations of surviving desert shrubs in burned landscapes may be associated with competitive release from neighboring plants or altered root-shoot ratios and may enhance reproductive capacity that could facilitate the post-fire recovery of woody shrubs.
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