| Dead wood is an important feature in Swedish Forests and is recognized as an important element for biological conservation, especially of dead wood dwelling arthropods. Arthropods are the most diverse taxon on earth and support a large number of ecological processes. Although, a biodiversity concern in their own right, arthropod abundance and diversity is a vital part of the food chain as food for vertebrate predators like birds and small mammals. For the latter group, dead wood on the forest floor will also give them shelter and might increase their movement and predation activity in forest stands. A study published in 2017 shows that the presence of piles of dead wood on the forest will benefit predation rates of cocoons of a pest insect, the European Pine sawfly (Neodiprion sertifer, Geoff). For this pest insect, predation of cocoons is long thought the driver of outbreak dynamics. Bellone et al 2017 is to my knowledge one of the first papers where a conservation measure has been positively connected to pest control. This finding led to the questions 1) how do these piles of dead wood contribute to arthropod biodiversity in monoculture stands and 2) Is this biodiversity related to increased predation rates of larvae of the same pest insect.
The aim of the project is to quantify the value of dead wood for the presence of arthropod biodiversity in monoculture pine stands and the consequences for predation of larvae of the folivorous insects.
Studies have shown that dead wood of different types is important for the conservation of wood dwelling beetles. Research indicates that arthropod herbivore biodiversity increases the diversity at the level of the predators. The proposed project connects the potential benefits of piles of dead wood in young forest stands to the predation of a pest insect. The stands, used in the study published in 2017, will be used because the piles of wood are still present. Pitfall traps will be used to assess the biodiversity of ground dwelling arthropods. I will use sticky traps on the tree trunk to quantify the number of arthropods using trees. If possible, I will use sentinel sawfly larvae in addition to plasticine model larvae to assess predation rates. For each tree associated with a wood pile, there will be a tree selected without a wood pile. All trees will be submitted to the same measurements. All piles of wood are present in monoculture pine stands. The analyses will focus on the effect of wood piles on the diversity of arthropods in the pitfall traps and on the sticky traps. Predation rates for both sentinel and plasticine larvae will be related the wood piles and associated diversity.
A positive association will give additional motivation for forest owners to leave dead wood in forest stands. The push for a bio-based economy has led to increased use of forest products and more forest owners remove logging residue (tree tops, branches and tree stumps) for the production of bio-fuels. This removal is found the affect biodiversity and ecosystem services provision negatively. The project proposed here will also provide an indication whether the removal of logging residue could affect the risk of insect outbreaks as a consequence of a cascading effect that dead wood removal on the arthropod food chain. |