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White spruce ( (Moench) Voss) cone crops were measured from 1986 to 2011 in the Kluane region of southwestern Yukon to test the hypothesis that the size of cone crops could be predicted from spring and summer temperature and rainfall of years t, t - 1, and t - 2 . We counted cones in the top 3 m of an average of 700 white spruce trees each year spread over 3-14 sites along 210 km of the Alaska Highway and the Haines Highway. We tested the conventional explanation for white spruce cone crops that implicates summer temperatures and rainfall in years t and t - 1 and rejected it, since it explained very little of the variation in our 26 years of data. We used exploratory data analysis with robust multiple regressions coupled with Akaike's information criterion corrected (AICc) analysis to determine the best statistical model to predict the size of cone crops. We could statistically explain 54% of the variation in cone crops from July and August temperatures of years t - 1 and t - 2 and May precipitation of year t - 2. There was no indication of a periodicity in cone crops, and years of large cone crops were synchronous over the Kluane region with few exceptions. This is the first quantitative model developed for the prediction of white spruce cone crops in the Canadian boreal forest and has the surprising result that weather conditions 2 years prior to the cone crop are the most significant predictors. [ABSTRACT FROM AUTHOR]

White spruce ( Picea glauca (Moench) Voss) cone crops were measured at five regional centers in southern and central Yukon for 30 years at one site from 1986 to 2015 and at four other sites during 9 to 11 years to select the best climatic model that uses cues from growing season temperature and rainfall to predict the size of cone crops. We evaluated six climatic models that use summer temperature and rainfall of years t - 1 and t - 2 to predict cone crops in year t. July temperatures provided the best predictors of white spruce cone crops, and no rainfall variable was related to the size of cone crops. We explored three variants of July temperatures: mean temperature, degree-days > 5 °C, and maximum temperatures. For each of these, we used the Δ T model that uses the difference in the July temperature measures of years t - 1 and t - 2. We compared the resulting six models with corrected Akaike's information criterion (AICc) to determine their relative predictive performance. The best model combined Δ T measures of degree-days > 5 °C and the four highest daily maximum July temperatures with R2 = 0.65. By comparison, the Δ T model involving only mean July temperatures was less successful ( R2 = 0.49). There was good regional synchrony ( rp = 0.7 to 0.8) in high cone crops over southern and central Yukon during 1986 to 2015. [ABSTRACT FROM AUTHOR]

Examines the spatial structure of Dicrostonyx groenlandicus lemming populations fluctuating in density. Use of mitochondrial DNA control region sequences; Variability of the microsatellite loci; Observation on the genetic variability on small islands and low level differentiation of the islands.