Research Topics Ecosystem Processes
About this Research:
Sierra Nevada Ecosystems
1000 Years of Forest History in the Glass Creek Watershed, Eastern Sierra Nevada
Interpreting the influence of fire, climatic change, and environmental change on subalpine forest structure and composition
Research Project Summary
Much progress has been made in the past two decades in elucidating the key role that recurring wildfire plays in determining forest structure and composition. While other forces such as climate change and landscape evolution obviously influence vegetation over longer terms, their relative importance as co-architects at the management-timescale of decades to centuries remains little investigated. We are studying forest history in a mid-elevation watershed in the eastern Sierra Nevada, the Glass Creek watershed. The forest extends from lodgepole pine at low elevations, old-growth eastside mixed conifer with red fir at middle elevations, to whitebark pine at treeline. A large wet meadow with high species diversity dominates the valley floor. Aside from domestic sheep grazing in the meadow, the watershed has been minimally disturbed by recent human activities; even fire suppression does not seem to have influenced fire regimes. The watershed has been significantly influenced, however, by repeat eruptions of the nearby Inyo Craters, whose most recent activities covered the watershed with many meters of tephra ~750 years ago. In related studies, we have been documenting the influence of climate on vegetation at nearby treeline elevations and the influence of climate on conifer invasion of the meadow. In this study, we investigate the main forest zones of this watershed as a case study in dissecting the role of climate, fire, and volcanism in shaping stand structure and composition.
Using dendrochronological, ecological plot, and fire-scar analyses in the forest zones, we are reconstructing forest structure, climate relations, and fire history over the last 1000 years. We find evidence for influence of each of the forces (fire, climate, and eruption) on forest dynamics, with relative importance changing over time. In some cases, the influences are confounding, in that they have similar effects ecologically, and are thus difficult to separate.
Important conclusions emerging from these studies include 1) the role of each force is significant and vegetation diversity cannot be adequately understood with reference to single one, 2) extreme events and variability in events determine significant ecological pathways that become set for hundreds of years, and 3) third order change is evident, that is - vegetation changes are evident in response to physical systems that are themselves changing.
Evaluate the relative roles of fire, climate change, and volcanic eruptions as architects of forest structure and composition over the past 1000 years.
Application of Research Results
This study is part of a complex of studies we are conducting in the Glass Creek watershed designed to provide information for resource managers about the relative influence of climate, fire, and volcanism on forest dynamics. Under conditions of changing climates, and altered fire regimes, decision-makers need accurate information about how forests respond to these forces. The Glass Creek Watershed is part of a larger landscape analysis by the Inyo National Forest, and management decisions will benefit from information provided in the suite of studies we are undertaking there.
Eastern Sierra Nevada: Glass Creek watershed, headwaters of the Owens River.
1) Millar, C.I 1) Delany, D.D. 1) Westfall, R.D. 2) King, J.C. 3) Stephens, S.A.
1) USDA Forest Service, PSW Research Station
Sierra Nevada Research Center
800 Buchanan St., Albany, CA 94706 USA
2) Lone Pine Research, Bozeman, MT 59715
3) University of California, Berkeley, Department of Environmental Science, Policy, and Management, Berkeley, CA 94720
Publications and Reports
- Poster: Millar, CI; Westfall, RD; Delany, DL; King, JC; and Alden, HA. 2004. High-Elevation Response of Conifers to Climate Change in the Sierra Nevada and Western Great Basin, USA: Treeline Elevation is Not the Primary Effect.
- Poster: Millar, CI; Westfall, RD; Delany, DL; King, JC; and Alden, HA. 2004. Climate as an Ecosystem Architect; Responses of High-Elevation Conifers to Past Climate Variability.