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Aspen Decline in Idaho and Nevada

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Title: Projecting climate change effects on aspen distribution and productivity in the central and northern Rockies by coupling hydrological and landscape-disturbance models

Abstract: Quaking aspen populations are thought to be declining in much of the west due to altered fire regimes, competition with conifers, herbivory, drought, disease, and insect outbreaks. Aspen stands typically support higher avian biodiversity and abundance than surrounding habitat types, and maintaining current distribution and abundance of several avian species in the northern Great Basin is likely tied to the persistence of aspen in the landscape. Aspen can also depend on accumulated snow drifts, which can retain soil moisture well into the spring and summer.

In the Northern Rockies of Idaho, we are examining long term dynamics of aspen regeneration, competition, and persistence. In order to investigate these trends, our study focuses on a highly instrumented partially forested watershed in the southwest of Idaho, the Reynolds Creek Experimental Watershed. Aspen groves within this watershed are highly dependent upon snow drifts that accumulate in the winter/spring for soil moisture throughout the growing season. Consequently, many stands have suffered during recent drought periods (late 1990's-early 2000s). Because of aspen's unique clonal nature, drought impacts must be understand not only from an individual tree perspective, but also from the perspective of the entire clone, which can take large areas and be comprised of many individuals trees. The implications of both drought and conifer encroachment on aspen regeneration is key to gaining insight on the long term viability of aspen, and understanding the role of both the individual and the clone is crucial. Our simulations will investigate the effects of these competing climatic and ecological pressures to gain insight into the potential fate of this keystone species over the coming century.

Our research addresses the following questions:
1) What is the current successional, structural, and spatial distribution of aspen on the landscape?
2) How have aspen stand condition and distribution been shaped by disturbance, e.g., fire?
3) How is global climate change likely to affect aspen condition and distribution?
4) How are today’s management strategies, or adaptive adjustments to those strategies, likely to affect long-term risks and persistence of aspen and associated avian communities?
5) How does the shifting patterns of water balance under climate change influence future aspen distribution and productivity?
6) What are the long term consequences of current patterns of conifer encroachment on extant aspen groves?


Funding:  PNW Climate Science Center (current), USGS (prior)

People:  Robert Scheller, Alec Kretchun

Collaborators:  
Doug Shinneman (USGS)Susan Earnst (PI: USGS), Tim Link (U-Idaho)
Past Collaborators: Peter Weisberg (UNR), Jian Yang (UNR)

Status:  Ongoing

Publications, etc.

Yang, J., P.J. Weisberg, D. Shinneman, T. Dilts, S.L. Earnst, R.M. Scheller.  Fire modulates simulated climate change response of aspen across topoclimatic gradients in a montane landscape of western North America.  Global Change Biology.  In review.