Postglacial changes in chironomid communities and inferred climate near treeline at Mount Stoyoma, Cascade Mountains, southwestern British Columbia, Canada

摘要: Analysis of the distributions chironomid (midge) and other dipteran subfossils from two high elevation lake sediment cores in Cascade Mountains reveals changes midge communities inferred climate since late-glacial. Cabin Lake 3M Pond are located near treeline subalpine Engelmann Spruce/Subalpine Fir biogeoclimatic zone British Columbia. In Lake, head capsule assemblages depict a typical late-glacial community, three distinct Holocene communities. community is composed cold-stenothermous taxa dominated by Stictochironomus, Mesocricotopus, Heterotrissocladius, Parakiefferiella nigra, Protanypus Paracladius, whereas warm water midges absent or rare, indicating cold conditions. A was not found Pond. both lakes early diverse warm-adapted assemblage, corresponding to climatic conditions xerothermic period. Lake's mid-Holocene records decrease relative abundance types accompanied an increase cold-stenotherms. At this period shows dramatic loss diversity taxa, as temperate genus Dicrotendipes dominates. This corresponds Hebda's (1995) mesothermic Further cooling late (to modern conditions) continued reduction persistence (at Lake) appearance Pond) cold-stenothermal community. similar timing Neoglacial advances Coast, Cascade, Rocky southern Similarities vegetation at these sites, along with more rapid response time Chironomidae, support sensitivity postglacial change sites.