| Coniferous forests in northern Scandinavia are attacked by several species of bark beetles. The most serious is the European spruce bark beetle, Ips typographus (spruce beetle henceforth), which occurs in outbreaks that can defoliate large areas of forest. An infestation of spruce beetle occurred the summer of 2019 in a tightly monitored study area in middle Sweden. The area has numerous spruce stands in open, half-open and dense forests. It is covered by a dense network of 150 loggers at 10 cm and 1 m above ground that have been monitoring hourly temperature and humidity since July 2017. The earliest signs of beetle attack occurred in June 2019 and I have exact data on when trees were attacked during the beetle flying season. With the current application I seek funding to exploit an unforeseen, unique and ephemeral opportunity to investigate how forest microclimate is linked to attack by spruce beetle and how, reciprocally, attack by spruce beetle affects forest microclimate. I seek funding to perform two projects:
(1) Investigate how forest microclimate affects both attack risk and life-history biology of the spruce beetle.
(2) Investigate how attack by the spruce beetle, and subsequent death of trees, affects forest microclimate around the tree at different spatial and temporal scales.
Together, these projects can provide fundamental information on how microclimate affects infestation risk and life-cycle biology of an important forest pest and, reciprocally, how spruce beetle attack affects forest microclimate, through tree health decline and mortality. By linking these data to other ongoing projects in the same area we will be able to estimate the indirect effects of spruce beetle outbreaks on life-cycle dynamics of other insects (including biocontrol agents and important pollinators) living in forests and forest edges.
The information provided by the current project is directly linked to both landscape and plant protection efforts. A key tool in managing spruce beetle outbreaks are mechanistic population growth models. These generally use laboratory studies of degree-day demands during the life cycle to estimate population growth, and are fed large-scale meteorological ambient temperature datasets to predict growth in certain areas. However, these large-scale temperature datasets often poorly reflect temperature in different forest microclimates, and further, the reciprocal interaction between spruce beetle attack and forest microclimate has never been studied, even though the effect of tree death on microclimate is known to be substantial.
Therefore, the current project aims to (i) build forest microclimate priority maps that could help logging companies and management officials better predict particular tree stands that are subject to high infestation risk and (ii) improve upon models of spruce beetle population growth in infested and healthy forests for better management. A third important goal (iii) is to develop an online decision-support tool for stake-holders (including private forest owners) to, using cheap equipment, generate high-resolution vegetation health maps that can be used for local forest management, for instance for pre-emptive logging (e.g. at an early stage of infestation), or for a range of other purposes. |