PARENT SESSION
Symposium #24: Adaptive Management Experimentation in Ponderosa Pine Forest Restoration.
Organized by: PZ Fule and PG Friederici
Wednesday, August 7. 1:00 PM to 4:30 PM. Maricopa Meeting Room, TCC.
Temporal and spatial variability of disturbance as reference conditions in a ponderosa pine ecosystem.
Falk, Donald*,1, Swetnam, Thomas1, 1 Laboratory of Tree-Ring Research, Tucson, AZ
ABSTRACT- Reference conditions are a central principle in restoration ecology, and play an essential anchoring role for intended post-restoration conditions. Few ecosystems, however, are homogenous in space or stable over time. Thus, the very notion of a "reference" must allow for variation within an envelope of relevant natural variability. We explore the importance of the natural range of variability for restoration by examining spatial and temporal variability in the disturbance regime of forests in the Jemez Mountains, New Mexico (USA). Historically, low intensity surface fires in such ecosystems were keystone ecological processes that regulated species composition, recruitment episodes, demographic transition probabilities, nutrient cycling, hydrology, and species interactions; restoration of southwestern pine forests is incomplete without restoration of an active fire regime. Our investigations show that surface fires were variable in both space and time. Temporal variation is evident in right-skewed probability distributions for intervals between fire years. Higher moments of the probability distribution reveal the occurrence and importance of irregular intervals between fires at varying spatial scales. Short-term (1-5 yr) variability appears to be driven by interactions of annual climate and fuel dynamics. Over longer (decadal-to-centennial) scales, fire regimes were non-stationary, reflecting entrainment by synoptic climate patterns affecting the entire bioregion. These observations demonstrate that the reference condition for ecological restoration is an n-dimensional space in many variables with considerable variation about means, not a point value. We discuss how ecosystem managers and restoration practitioners can apply variability into their prescriptions and management strategies.
KEY WORDS: fire intervals, restoration ecology, temporal variation, reference conditions