Defoliation by spruce budworm (Choristoneura fumiferana Clem.) on balsam fir (Abies balsamea (L.) Mill.) is more severe in fir than in mixed fir-hardwood stands. Previous studies assumed that defoliation in fir-hardwood stands was reduced in proportion to percent hardwood regardless of outbreak severity. We tested the influence of stand composition on defoliation during the first 5 years of a spruce budworm outbreak near Amqui, Quebec, by sampling 27 fir-hardwood plots selected to represent three percent hardwood basal area classes (0%–25%, 40%–65%, and 75%–95%). Balsam fir defoliation was significantly lower (p < 0.001) as hardwood content increased, but the relationship varied with overall defoliation severity each year. Annual plot defoliation in fir-hardwood plots, estimated using: (1) defoliation in pure fir plots and the assumption that defoliation in fir-hardwood plots was reduced in proportion to percent hardwood; (2) a generalized linear mixed-effects model with defoliation in pure fir plots, percent hardwood, and interaction as fixed-effects; and (3) Random Forests prediction incorporating 11 predictor variables, resulted in r = 0.77, 0.87, and 0.92 versus measured defoliation, respectively. Average defoliation severity in softwood plots and percent hardwood content were the most important variables in Random Forests analysis. Data on average defoliation level in softwood stands, as an indicator of overall outbreak severity, improves prediction of balsam fir defoliation in mixed stands.

Floods are one of the most destructive natural disasters in the world, especially in densely populated and economic areas. Tongzhou is an important satellite city of Beijing, which undertakes the important mission of alleviating Beijing’s non-capital functions. Therefore, it is of great significance to study and analyze the flood process in Tongzhou. In this study, the distributed hydrological model WEP-L was used to construct a storm flood model in Tongzhou, and the flood process under different storm scenarios was studied and analyzed. The results show that under the once in 20 years rainstorm scenario, the precipitation in the study area increased by 92%, and the peak flow of Beiguan station increased by 171%; under the once in 20 years rainstorm scenario, the precipitation in the study area increased by 246%, and the peak flow at the Beiguan station increased by 430%; under the once-in-a-century rainstorm scenario, the precipitation in the study area increased by 297%, and the peak flow at the Beiguan station increased by 606%. This study can provide reference for the urban flood control planning of Tongzhou.