Biodiversity and focal species response-diversity to different management prescriptions following severe windblow caused by Storm Arwen.

Storm Arwen was one of the most powerful and damaging winter storms of the last decade. Forest plantations on the eastern side of the UK have experienced significant damage from Storm Arwen, This offers a short-lived urgent research opportunity to lay the foundations for innovative work on both forest management for biodiversity and climate resilience and fundamental ecosystem processes.
Windthrow is a natural process creating gaps at various scales in natural and production forests by snapping or uprooting, trees in localised pockets or laying over entire stands. The process of decomposition of dead wood a large flush of available nutrients, are immediate and short lived. Tree decomposition then spans decades and can lead to arboreal cavity creation or treefall dens used as nesting sites or shelter by many vertebrates. Sunlight and nutrient inputs to the soil changes and accelerates ground vegetation that may then cascade through entire ecosystems.
Storm Arwen occurred at a time when Forestry England was already investigating new mechanisms to accelerate biodiversity restoration. In particular, developing resilience to expected increases in the frequency of extreme events, new pests and pathogens, and the acute need to increase carbon sequestration. Storm Arwen and the partnership underpinning this Urgency proposal, have catalysed Forestry England to commit to a potentially transformative landscape scale experiment involving the fate of windblown timber and dead wood.

The objectives of this Urgency grant are:
A. To co-design and implement, with Forestry England an experiment conducted at a landscape scale making use of the availability of vast areas with windblown timber to evaluate the long term biodiversity benefits of the following management prescriptions:
- Windblown areas will be harvested, fallen timber recovered, followed by replanting of diversified crop and deciduous tree species (including birch, aspen, spruces, firs, pines).
- Windblown areas will not be harvested, fallen timber left, with replanting (species as above).
- Windblown areas will not be harvested, fallen timber left, without replanting, allowing natural regeneration (non-intervention).
- Non-windblown control areas dominated by Sitka's spruce and Scot's pine.

Because the process of decay will start in spring, we will urgently design and implement a program of field sample collection to provide a crucial baseline. Sampling will be focused on documenting the rates, magnitudes and spatial extents of processes that arise from retaining fallen timber. They include the eventual release of nutrients currently locked in trees, following sequestration by fungi and invertebrates feeding on dissolved organic matter, then uptake by grasses and small bushes leading, over time, to changes in the vertebrate guilds responding to vegetation and structural changes in the forest (the plantations are presently devoid of significant understory higher plants).

Thus, the focus is on quantifying the magnitude and timing of the responses which remain largely unknown for coniferous trees in man-made forest plantations in an Atlantic climate.
Field sampling and analytical methods are largely standard and in use at the University of Aberdeen or long-standing collaborators institutions. They will include measuring precisely the amount of dead and standing wood, the baseline nutrients in wood and in soils, the rate of wood colonisation by fungi and the speed and rates of colonisation of beetles, grasses, shrubs and trees passerine birds and woodpeckers, small mammals (mice, voles, squirrels) and focal vertebrate predators (marten and owls) to dead wood and treatments will all be assayed at the plot-level.