Many foresters fear the outbreak of bark beetles, as they can have disastrous economic impact. The bark beetles live, as the name already indicates, in the bark of different tree species. Many beetle species kill the tree they live off. Other beetles live in deadwood or already dying trees. Why don’t we get rid of bark beetles when they only cause damage, you might wonder? That is because these beetles play in important role in the forest ecology, for example by recycling deadwood into nutrients for new plants.
Please also read: Forest Wilderness and the role of deadwood
Monitoring outbreak potential
An infestation of bark beetles can damage many timber trees, therefore affecting the logging industry. In areas with commercial forests, people use pheromone traps to capture the bark beetles and assess their population growth. Austrian scientists from the Central Institution for Meteorology and Geodynamics and University of Natural Resources and Life Sciences in Vienna found another way to monitor the beetles’ population dynamics.
Counting days and temperature
From long term monitoring, it appears that the bark beetles follow a specific behaviour, which depends on temperature. Simply put, below 8 degrees Celsius, it is too cold for the bark beetles. At those times, there is no activity. Above 8 degrees, the bark beetles become active, often damaging their host tree. What the researcher tried to figure out is when the beetles fly to the next tree. It appeared that we can now predict rather precise when this happens. Taking the total sum of the average daytime temperatures, bark beetles start to fly out when the sum reaches 550 degrees. That means, if we have 4 weeks with an average daytime temperature of 25 degrees, the beetles will start dispersing after 22 days (22 x 25 degrees = 550 degrees).
Predicting dispersal timing
The researchers in Austria have created a digital map to monitor the temperature sums in different regions. The online tool is currently further developed and tested. This can help commercial foresters to prepare for outbreak events in the future.
Let them fly?
Not everybody worries about the bark beetle. Although deadwood provides a home for bark beetles, there are many other insects living off deadwood. One of the best known examples of non-intervention management at an bark beetle outbreak is Sumava National Park and the bordering Bavarian Forest in Czech Republic and Germany. The management decided to let nature take it’s own path, when hundreds of trees died. The bark beetle impacted the landscape view dramatically, but after several years nature started to regrow again. It is all part of the ecological cycle of nature, in which growing and dying of trees is a vital part.
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