The Potential for Pollen Records to Detect Mountain Pine Beetle Disturbance in a Pine-Dominated Forest, Idaho, USA

Abstract

Mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins) outbreaks are an important component in forest succession for Pinus (pine) forests in the western United States. The research presented here is the first attempt to use pollen data from lake sediment cores to identify MPB disturbance over the past 1600 years within a pine-dominated forest. With evidence of both current and presettlement MPB outbreaks in the surrounding forest, Fishstick Lake, a small subalpine lake in the Sawtooth Mountains of Idaho, is located in a Pinus contorta (lodgepole pine)–dominated forest. Previous work by Morris et al. (2010) and Morris and Brunelle (2012) used pollen data from lake sediment cores to identify Dendroctonus rufipennis (spruce beetle) outbreaks in a Picea engelmannii (Engelmann spruce) forest by identifying the tradeoff between host (P. engelmannii) and nonhost (Abies lasiocarpa [subalpine fir]) conifers following an outbreak. This research tested the hypothesis that pollen data can be used to identify disturbance events that affect Pinus within a Pinus-dominated forest. Because the abundance of non-pine taxa is low in pine-dominated systems, it was uncertain whether the response of non-pine, nonhost taxa would be detectable. This study used a normalized difference pollen index (NDPI) to test this hypothesis. The results indicate that proxy data (pollen) can be used to identify MPB disturbance in a pine-dominated forest.