Background
Empty pupae on a burnt birch at one of the restoration sites. Photo: Ruaridh Hägglund
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During the last one and a half centuries intense forest industry has dramatically changed the structure and composition of the Swedish boreal forests. The forests of today lack much of the structural and compositional heterogeneity compared to that of the forests before the era of industrial forestry. This simplification has occurred as well on a stand level as on the landscape level. Within stands, there would often have been a mix of tree species although one or two species would dominate in numbers. In most areas pines or spruces were the dominating tree species, but in stands where disturbances such as forest fire, wind throw, insect outbreaks or other biotic or abiotic disturbances had occurred recently, deciduous trees would often dominate for some period of time. Even though pines and/or spruces in most cases out compete deciduous trees there would frequently remain an element of deciduous trees in the stand. On the landscape level these elements of forest dynamics with disturbances and subsequent patterns of succession shaped a continuously changing landscape with a variety of stand types “moving” through the landscape.
Besides from mixed tree species composition induced by disturbances, one of the major effects of disturbance was the creation of dead wood such as snags and logs of different sizes and tree species. Dead wood of different types are amongst the most important elements for biodiversity in boreal forests. Logs and snags constitute the living space for thousands of species of beetles, fungi and bryophytes, so called saproxylics. In pre-industrial forests the amounts of dead wood could reach as high as 120 m3/ha. In comparison, the modern day forests seldom contain more than 2-3 m3/ha of dead wood. This completion of dead wood in the landscape has had dramatic effect on the communities of saproxylic species; more than 2000 of the species on the Swedish red list are considered to be saproxylic. In order to maintain many o these species in the landscape there is therefore a need to act, and that is what my project is all about. |
Project description
The aim of my project is to evaluate different management efforts restoring ecological legacys in the forest. The aim with such management is to improve possibilities for the survivial of many threatened species in the forests of boreal Sweden. We have conducted an experiment with three types of different treatments. Two of these treatments are supposed to mimic different types of natural disturbances, namely, forest fire and small gap creation. Prior to the active and very succesfull fire management during the last century, forest fires were frequent i large parts of boreal Sweden. Small gaps on the other hand were created as single trees or small groups of trees died due to old age, strong winds, insects attacs, fungal infection or other biotic and/or abiotic factors. The third treatment is used as a control. In these controls we let the forest gouvern it self and develope on its own.
To be able to test for differences between treatment we use a replicated design of our study. In total the experiment consists of 30 stands spread through out a large part of the central boreal region of Sweden. Ten of the stands are to be burned. Six of these stands were burnt in 2011, unfortunately the summer of 2011 was unusually wet, so four of the sites could not be burned that year. The following year was even wetter, resulting in no burnes at all in 2012. We are hoping for a nice and dry summer in 2013, so that the remaining four stands will be burnt this year. Ten stands have been subjected to small gap cuttings, we have created gaps with a diameter of 20 meters, in total the gaps cover 18% of each stands area. Within these gaps we have created dead wood thrugh a variety of methods. Some trees have been cut at gruond level, others higher up creating high stumps, yet others have been topped over reasembling windallen trees, and yet others have been girdled. Within half of the gaps created all trees killed or damaged have been left in the gap adding substancial amouts of dead wood to the stands. |
Restoration sites in the project. Red dots represent burned stands; green controls and white stands with artificial gaps.
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My part of the projekt
My part of the project is to evaluate what effect the three different treatments have on beetles. By collecting beetles in three different ways I will be able to study what happens to different beetle communities when the stands have been subjected to our treatments. To get a good picture of what happens with ground beetle communities we set out ten pitfall traps in each stand. Beetles hatching from dead wood are sampled by using emergence traps. These traps are made by wrapping a part of the tree with a black terpaulin with a collecting jar attached to it. Since the only source of light comes from the entrance to the collecting bar the beetles crawl into it and get cught there. The third type of trap is a flight intercept trap wich consists of a plastic sheet with a collecting jar attached to the bottom of it. The trap is suspended in mid air between two trees interscepting beetles flying around in the stand.
Flight intercept trap of the IBL-model. Notice the collecting jar at the bottom of the trap. The picture comes from another project than the restoration project. Photo: Ruaridh Hägglund
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Emergence trap of the eclector type that we use. The picture is taken at one of the sites with created gaps. Unfortunately there is no collecting bottle attached since it taken in winter when no collection is carried out. Photo: Ruaridh Hägglund
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