English

Abstract

All Ecosystems are dependant on some form of disturbance to perpetuate or reset succession. Aggressive fire suppression since the early 1900’s has drastically reduced this one form of natural disturbance nationwide. Many ecosystems, especially fire dependant ecosystems, are becoming dense, often overgrown, senescent communities with diminishing species diversity. Eventually when these communities do burn, excessive fuel loads due to prolonged fire suppression, create a stand replacing fire. This severe disturbance often exceeds former thresholds and sets the stage for a much different plant community. To prevent this phenomenon land management agencies have been conducting controlled burns under strict prescription to reduce unnatural or hazardous fuel loads. In spring of 2002, a prescribed fire was run through a Montana Ponderosa pine savanna which contained a series of riparian ecosystem floodplains. The prescription was to remove 70% of the smaller trees without removing more than 20% of the larger trees. A post burn survey revealed that approximately 90% of the smaller trees and 30% of the larger were actually removed by the fire. Continual groundwater monitoring in the riparian areas continues to show an average yearly decrease in depth to groundwater. Native species composition, based on percent cover increased from 26% pre burn to 43% post burn, introduced/invasive species cover decreased from 6.1% to 2.3% post burn, and facultative wetland and obligate species were detected in 16% more of the post burn riparian transects. Decreased depth to groundwater doubled the total number of forb species. In the riparian sites that had the strongest response in groundwater, 20% more biomass was produced as compared to their unburned counterpart. Monitoring will continue in this area until fall of 2007. To test these trends a duplicate site is currently being monitored in Whitehall, Montana. Additional