Spruce Beetle Outbreaks on the Kenai Peninsula, Alaska, and Kluane National Park and Reserve, Yukon Territory: Relationship to Summer Temperatures and Regional Differences in Disturbance Regimes. Berg, E. E., Henry, D. J., Fastie, C. L., Devolder, A. D., Steven M., & Matsuoka, S. M., (2006). Spruce beetle outbreaks on the Kenai Peninsula, Alaska, and Kluane National Park and Reserve, Yukon Territory: Relationship to summer temperatures and regional differences in disturbance regimes. Forest Ecology and Management v. 227, p. 219–

Objectives Investigate: The degree of spruce beetle’s (Dendroctonus Rufipennis Kirby) attacks in the past and present. Frequency of outbreaks. The effects of our changing climate on these outbreaks.

Methods Separated the study area within 3 areas. Kluane National Park. Kenai Peninsula North, containing diverse forest, Kenai Peninsula South, containing almost exclusively spruce. Measured growth rings in trees and scar tissue that suggests beetle infection to discover outbreaks of the past. Collected data taken by previous studies of past infections. Arial surveys were done to measure more recent outbreaks. Collected annual mean temperature records from the area’s local airport.

Tree Ring Width Fig. 2. A growth release was defined as a doubling (2) of the ratio of the forward 10-year mean to the past 10- year mean of annual ring-widths (growth ratio) in a spruce tree. In this example, a growth release was detected in 1871.

Figure 2A This graph shows tree ring width over a period of 60 years. This graph shows as an example of how a “growth release” is detected. Growth releases are abnormally wide rings. Suggesting the tree had a lot of growth that year. Growth releases are a proxy (indicator) for a spruce beetle outbreak. Evidence Shown Critique Only shows a very small time frame. Serves as a great example to explain growth release and clearly show what some of the other figures are showing.

Percentage of Growth Releases Fig. 4. Average percentage of trees in a stand showing a growth release during a 5-year period; southern Kenai (10 stands), northern Kenai (13 stands), and Kluane (4 stands).

Figure 4. Shows the average percent of trees that experienced a tree ring growth. Set at 5 year intervals over a period of 240 years. Separated the different study areas by Kenai Peninsula and Kluane National forest. Further separated between the two subdivided study areas in the Kenai Peninsula. In a way this provides further resolution. It is important to note that if Southern Kenai had more growth release in the same year. It would cover the results of Northern Kenai entirely. Shows a good overall picture of the last 240 years with several years that appear to be outbreaks. Evidence Shown Critique

Predicted Outbreaks in Relation to Temperatures. Fig. 8. Predicted probabilities of the occurrence of spruce beetle outbreaks (>15,000 ha forest area infested) in relation to mean summer temperatures (May–August) on the northern (*) and southern () Kenai Peninsula, Alaska, 1971–1996. Predicted probabilities were based on an autoregressive logistic regression model (Table 2).

Shows outbreaks in relation to summer temperatures, model predicted outbreak probability, and actual observed outbreak. Shows a clear correlation to warmer mean summer temperatures and observed outbreak. Evidence Shown Critique Lots of information in the graph. Hard to tell what the observed outbreaks are. The information is tightly packed together.

Conclusion Showed spruce beetle outbreaks in relation to warming climate by graphs and explaining there methods of data collection/prediction. Showed historical outbreaks along with severity. Explained why the data was collected the way that it was.

Commentary. I felt this paper did well explaining the data and starting with the basics. Fig 3 brought the reader up to speed on what the data means and how we come to the conclusion that past outbreaks existed. They tackled the subject with 3 variables: time, severity, and temperature in a way that suggests spruce beetle attacks will increase as our global temperatures increase. 2.