Monday, August 3, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Background/Question/Methods
Mycorrhizae are an important component of ecosystems. Functioning in plant nutrition, nutrient cycling, food webs, and the development of soil structure, nearly all herbaceous plants are associated with arbuscular mycorrhizae (AM) fungi and most trees and shrubs are associated with ectomycorrhizae (EM) fungi. As with most forest ecosystem components, high severity fire can disrupt these mutualistic associations. Previous studies have demonstrated that mycorrhizal fungi infection rates decrease immediately after fire, but little is known about their rates of recovery. We examined AM and EM inoculation potentials in a sequence of southwestern ponderosa pine stands that experienced stand-replacing wildfires at different time periods in the past. Intact soil cores were collected from four sites along this 36-year fire chronosequence and we determined their AM and EM inoculation rates using organic corn (Zea mays) and ponderosa pine (Pinus ponderosa), respectively, as bait plants. Additionally, we determined if EM infection altered nitrogen (N) and phosphorus (P) uptake by pine seedlings, and examined the relationship between AM inoculation potential and the aboveground plant community.
Mycorrhizae are an important component of ecosystems. Functioning in plant nutrition, nutrient cycling, food webs, and the development of soil structure, nearly all herbaceous plants are associated with arbuscular mycorrhizae (AM) fungi and most trees and shrubs are associated with ectomycorrhizae (EM) fungi. As with most forest ecosystem components, high severity fire can disrupt these mutualistic associations. Previous studies have demonstrated that mycorrhizal fungi infection rates decrease immediately after fire, but little is known about their rates of recovery. We examined AM and EM inoculation potentials in a sequence of southwestern ponderosa pine stands that experienced stand-replacing wildfires at different time periods in the past. Intact soil cores were collected from four sites along this 36-year fire chronosequence and we determined their AM and EM inoculation rates using organic corn (Zea mays) and ponderosa pine (Pinus ponderosa), respectively, as bait plants. Additionally, we determined if EM infection altered nitrogen (N) and phosphorus (P) uptake by pine seedlings, and examined the relationship between AM inoculation potential and the aboveground plant community.
Results/Conclusions
We found higher AM inoculation overall at the burned sites relative to their adjacent unburned controls. This increase in inoculation was more pronounced at the older burn sites. The plant species richness was consistently higher at the burned sites. The two older burned sites appear to have distinct plant community compositions from the younger burned sites, as well as higher AM infection potential. Weak correlations were found between percent corn AM infection and aboveground plant biomass. EM infection was also affected by fire and recovery time. Our results suggest that wildfires have legacy effects on mycorrhizal inoculation potential, which could greatly influence post-fire plant succession.
