Ecological Archives E094-157-A6

Alan J. Tepley, Frederick J. Swanson, Thomas A. Spies. 2013. Fire-mediated pathways of stand development in Douglas-fir/western hemlock forests of the Pacific Northwest, USA. Ecology 94:1729–1743.

Appendix F. Spatial variation in the representation of age-structure types between the two study areas and along broader climatic gradients.


Fig. F1. Comparison of the observed number of transects in each of the six age-structure types in the Blue River and Fall Creek study areas in the central western Cascades of Oregon to that expected if the proportion of stands in each type did not differ between the two study areas. The age-structure types lacking influences of non-stand-replacing (NSR) fire (types 1 and 5) are slightly more abundant than expected in the Blue River study area, and those influenced by non-stand-replacing fire (types 2, 3, 4, and 6) are slightly more abundant than expected at Fall Creek. However, based on a chi-square test on a two-by-six contingency table, we do not reject the null hypothesis that the proportion of transects in each of the six age-structure types differs between the two study areas ( = 9.47, df = 5, p = 0.092). Nevertheless, the greater than expected abundance of stands influenced by NSR fire at Fall Creek and the greater than expected abundance of stands lacking influences of NSR fire at Blue River is consistent with broader variation in the fire regime along climatic gradients as suggested by comparison to the findings of other studies in below.



Fig. F2. Comparison of the proportion of stands with two or more cohorts of Douglas-fir trees among five watershed-scale, fire-history studies along a gradient of annual precipitation in the western Cascades of Oregon. Annual precipitation is from the PRISM data set for 1971–2000 (Daly et al. 2008). Codes for the physiographic provinces (upper right) are: CR = Coast Range, EC = Eastern Cascades, KM = Klamath Mountains, WC = Western Cascades, and WV = Willamette Valley.

Literature cited

Agee, J. K., and F. Krusemark. 2001. Forest fire regime of the Bull Run watershed, Oregon. Northwest Science 75:292–306.

Daly, C., M. Halbeib, J. I. Smith, W. P. Gibson, M. K. Doggett, G. H. Taylor, J. Curtis, and P. P. Pasteris. 2008. Physiographically sensitive mapping of climatological temperature and precipitation across the conterminous United States. International Journal of Climatology 28:2031–2064.

Garza, E. S. 1995. Fire history and fire regimes of East Humbug and Scorpion Creeks and their relation to the range of Pinus lambertiana Dougl. M.S. Thesis. Oregon State University. Corvallis, Oregon, USA.

Van Norman, K. 1998. Historical fire regime in the Little River watershed, southwestern Oregon. M.S. Thesis, Oregon State University, Corvallis, Oregon, USA.

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