Forest structure, composition and bird counts in windblown and control sites in Kielder Forest, Northumberland, UK, May-July 2022

We investigated the impact of storm Arwen (November-2021) on the forest structure and biodiversity of Kielder (Northumberland, UK) via 100-m transects, 10x10 m plots, 2x2 m quadrats, and bird point counts at twelve paired windblown and control sites (24 sites in total). All our survey site locations were obtained from a handheld GPS device.

We counted and measured all fallen trees found along a 100 m transect within each site. We measured the perimeter of each fallen tree three times to allow for volume estimation. Along each transect, we deployed three 10x10-m plots where we counted and measured the diameter at breast height of trees. These plots were placed at 0-10, 50-60, and 90-100 metres along the transect. We visually estimated the cover of grasses, ferns, mosses, fungi, and lichens using the Braun-Blanquet scale inside 2x2 m quadrats at 0-2, 50-52, and 90-92 along our 100 m transects. We also inventoried plant species found within these 2x2 m quadrats. Plants, including trees, were identified using field guides and keys and supported occasionally with photographic-aided identification using the iNaturalist application (https://www.inaturalist.org/observations).

For estimating bird richness and abundance, we conducted 2-4 bird point counts within each site between 6 and 10:30 am. During each count, an observer stayed in one spot for 5 minutes and recorded all birds they saw or heard, assigning them to one of five distance categories (0-10 metres; 10-20 metres; 20-30 metres; 30-40 metres; and 40-50 metres). All birds beyond 50 metres were not counted. This was done by either estimating the distance or using a Bushnell Golf Rangefinder. Only those detections that could be identified at the species level were included. All bird point counts were repeated twice to ensure the detection of all species using the survey sites.