LD2-3: Increases in summer temperature explain spatial and temporal patterns of change in insect outbreaks

Surveys of forest insects and their associates have been conducted annually in Bonanza Creek Experimental Forest (BNZ) for the past 30 years. Some of these species of insects such as Ips engraver beetles, spruce budworm, larch sawfly, larch budmoth, large aspen tortrix, and spear-marked black moth have periodically reached outbreak levels. The existing 30-year data set was incorporated into the BNZ data files in 2003. BNZ insect population data will also be compared with the 30-year annual aerial survey of pest outbreaks conducted by Forest Health Management of the USDA Forest Service. Since the insect population monitoring emphasizes species that have greatest impact on trees in mid- and late succession, their populations have been monitored in these stages.

Insect population levels and diversity will be measured on permanent monitoring sites within BCEF. The sites will be visited in late May, early July, and late August to measure insect density by species and host plants. Sampling methods will include branch sampling, various insect traps (tree bole screen traps, pheromone-baited funnel traps, pit-fall traps, and window flight traps). Trapping of ground beetles (Carabidae) will be initiated to determine if these species can be used as indicators of climate change. Monitoring of ground beetles will be done on the Kenai Wildlife Refuge, Chugach National Forest, and BNZ. We will also continue measurement of bark beetle and wood borer population densities and diversity in plots established in 1980 on replicated sites with different disturbance regimes. These insect populations have previously been compared for 1, 5, 10, and 20 years (2003) after burning and timber harvest on floodplain and upland white spruce sites. All new data will be incorporated into the existing data set and comparisons made with past population levels in relation to climate change and landscape disturbances.