Relationship between Forest-landscape Structure, Spruce Bark Beetle Outbreak and Subsequent Likelihood of Burning

Relationship between Forest-landscape Structure, Spruce Bark Beetle Outbreak and Subsequent Likelihood of Burning

The research aimed to establish the relationship between the outbreak of bark beetles and the subsequent likelihood of wildfire outbreak in the Alaskan boreal forest. The researcher presented a sufficient background for the study question. There are several incidences of fire outbreak and cases where the fire has been suppressed coupled with a claim that bark beetle breakout increases the chances and extent of wildfire. The researcher, therefore, wanted to evaluate how variation in the forest landscape structure shapes natural disturbance patterns and mediation of interactions between multiple disturbances.

A massive outbreak of spruce bark beetle (Dendroctonus refipennis) occurred in the 1990s in the Boreal spruce forest on the Kenai Penisula. The landscape of forest affects the disturbance patterns and interactions between disturbances. The outbreak of spruce bark beetle has become more prevalent in recent decades. Understanding the role of forest landscape structure is essential as it will enable planners to change disturbance regimes as well as the nature and magnitude of their interactions. This will help in reducing the risk of bark beetle outbreak and subsequent patterns of burning.

Hypothesis

One of the hypotheses the researcher wanted to prove was that the outbreak of SSB was not as spatial extensive and of shorter duration in the north where there were both white and black spruce intermingled. The alternative hypothesis was that the outbreak was more widespread in the south region dominated by white spruce. Another possible hypothesis than could be proved by this study is that there a correlation between the infestation of spruce bark beetle and the frequency of fire outbreak

Methodologies

Geo-spatial datasets of fire perimeters between 2001 and 2014 were analyzed to determine how forest landscape structure mediated the outbreak and duration of SBBs. Collected data was also used to evaluate the effects of SBBs outbreak on the likelihood of subsequent fire outbreak. The 200 National Land-cover Database was used to map the type of vegetation and percentage of land covered by the forest canopy. Regression analysis was used to predict the likelihood of burning between 2001 and 2014.

The result of this study was not represented. They would have used more of line graphs instead of the bar graph used in this presentation. Regression analysis should have been expressed more clearly. There was no sufficient data to account for suppression activities that happened in the study regions.

Conclusion

Climate is one of the critical factors determining the likelihood of forest fire. However, there this study revealed that there is no relationship between aridity and the probability of a fire outbreak. There was an increased likelihood of wildfire outbreak in the Northern region probably because of drying surface fuels following longer bark beetle outbreak durations. The outbreak of SBBs did not influence the possibility of subsequent fire outbreak in the southern region. The research reveals that SBBs prefer white spruce to black ones (Hansen, Winslow, et al., 2016).

The most important result in this study is the result showing the relationship between bark beetle infestation and fire outbreak. There was a smaller extent of fire outbreak for a shorter duration.

Strength of the Study

The researcher was able to compare a wide range of data for a long duration of time. This is important in ensuring that the correct conclusions were arrived at after examining the trends for thirteen years.

The next research should focus on identifying how the outbreak of the bark beetle affects hydrological and radiative fluxes because there is a relationship between environmental conditions and the incidences of fire outbreaks.

Work Cited

Hansen, Winslow D., et al. “Forest-landscape structure mediates effects of a spruce bark beetle (Dendroctonus rufipennis) outbreak on the subsequent likelihood of burning in the Alaskan boreal forest.” Forest Ecology and Management 369 (2016): 38-46.