Climate Change Impacts on Shrub-Forest Ecotones in the Western US

Principle Investigator: Michael E. Loik, University of California, Santa Cruz
Co-PI: Daniel F. Doak, University of California, Santa Cruz (after Aug. 2007: University of Wyoming)
Unfunded collaborator: Ronald P. Neilson, Pacific Northwest Forest Service Research Laboratory

Abstract:: This research is motivated by (i) the importance of snow as a dominant form of precipitation for a large portion of arid and semi-arid regions of the western United States, (ii) uncertainty in how changes in snow climate will affect ecotones between terrestrial ecosystems of the West, and (iii) the need to better understand how climate change impacts recruitment of dominant organisms of range and forest lands of the West, in order to better predict climate change effects on distributions of terrestrial ecosystems.

Objectives: Our objective is to experimentally test hypotheses on linkages between snow climate (depth, melt timing), recruitment, and species composition driven by annual, interannual, and long-term snow climate forcing. Another objective is to use data to parameterize a set of climate and species-interaction driven demographic models to quantitatively predict the direct and indirect effects of snow depth on population performance and then to develop a recruitment niche for the Dynamic Global Vegetation Model, BIOMAP.

Location: Experiments will be conducted at the ecotone between Great Basin Desert sagebrush steppe and Sierra Nevada conifer forest, near Mammoth Lakes, Mono County, California.

Hypotheses: The experiments will address a series of questions, including: How do snow depth and melt timing affect water relations, growth, and recruitment for dominant shrubs and trees of a widespread ecotone type? How do soil nutrients and microclimate complicate recruitment patterns? And, what recruitment stages/processes are most sensitive to snow climate? Finally, what linkages between demographic analyses and dynamic global vegetation models with experimental results will best improve our ability to predict future distributions of these terrestrial ecosystems?

Methods:Experiments will use large-scale (> km), long-term (>50 yr) snow fences in eastern CA. We will use a combination of in situ instrumentation, experimental plantings, removal of adults, annual ring growth patterns, and stagestructured demographic and dynamic vegetation modeling to test hypotheses linking variation in snow depth with soil water and nutrients, recruitment niches, community patterns, and ecotone migrations over time.

Deliverables: Experiments and models will result in at least three peer-reviewed publications, and will train one graduate student and one postdoctoral researcher. We aim to develop coherent, unified experimental-modeling synthetic products that will be available to all investigators, that will be useful in guiding future research, and that will improve predictive capacity on the effects of climate change on future geographic distributions of terrestrial US ecosystems.

last updated: 15 April 2007 PLH