PARENT SESSION
Poster Session #42: Restoration of Public Lands.
Wednesday, August 7. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC
112
Variability among plant communities in neighboring pine forests has implications for determining reference conditions.
Gildar, Cara*,1, Fulé, Peter1, Covington, W. Wallace1, 1 Northern Arizona University, Flagstaff, AZ
ABSTRACT- We contrast ponderosa pine plant communities in Grand Canyon National Park: one with 120 years of artificial fire exclusion and two adjacent frequently burned sites. These forests are excellent places to gather reference information for ecological restoration due to limited livestock grazing and no commercial logging. Tree density was significantly higher at the fire-excluded site (1424.4 trees ha-1) and had the highest rotten coarse woody debris (23.2 Mg ha-1) and duff accumulation (4.32 cm). Although observed species richness (48-89 species) was not significantly different among sites, sampling year had a significant effect. The years differed greatly in precipitation. Dominant species, as one measure of species composition, differed among sites. Herbaceous cover and biomass on the fire-excluded site were lower than burned sites, but significance varied between years and sites. Arbuscular mycorrhizal inoculum potential had a negative relationship with tree basal area and Carex spp. and a positive relationship with species richness. Responses were variable at scales smaller than stand level, and burned sites showed varied responses. Climatic variability affected responses. Implications for restoration include: 1) mycorrhizal infectivity, which has been shown to greatly influence plant community dynamics, showed feedback responses to overstory and understory structure, and 2) different choices for potential restoration treatments may have resulted if we sampled only one burned site or one year. We suggest a multi-scale, multi-year, multi-site approach to measuring reference conditions in ponderosa pine.
KEY WORDS: reference conditions, ponderosa pine, understory plant community