HOLOCENE FOSSIL BEETLES FROM A TREELINE PEATLAND IN SUB-ARCTIC QUEBEC

We analyzed the fossil insect fauna of a palsa peatland located 10 km south and east of the treeline in subarctic Quebec (57 degrees 45'N, 7 6 degrees 15'W) to detect any changes in the species composition durin g the Holocene epoch and to infer past environmental conditions in the study area. A minimum of 802 beetle individuals were recovered from a 2-m pear section, representing 51 taxa (18 identified to the species level) and 8 families. Trechus crassiscapus, Eucnecosum brunnescens, a nd Olophrum rotundicolle were the most common species found in the pea t. The insect assemblage was quite stable through the study interval ( 5850-1950 BP). The formation of the palsa (where the peat section was excavated) occurred probably after 1950 BP, raising the soil surface a bove water level and preventing additional peat accumulation. The prop ortion of boreal forest species in the faunal assemblage is high (88%) . The only arctic (tundra) species found were Amara alpina and Pterost ichus arcticola. Many species were out of their modern distribution ra nge, but since collection localities are scarce in subarctic Quebec, t he modern range of these species may extend to the study site. A mutua l climatic range analysis, employing beetles identified to the species level, showed that the mean July temperature of the study area betwee n 5850 and 1950 BP was possibly 2.8-5.5 degrees C higher than during t he 20th century. This assertion is supported by other paleoecological data (pollen and charcoal remains) suggesting a cooling trend in the s tudy area after 2000 BP. However, since the last 2000 years are missin g from the sampled peat section, it was not possible to quantify the i mpact of the cooling trend on the beetle fauna.