Herbivory in West Arnecliff Wood

Sam Witham – Conservation Research Student

During my placement year with the National Park I’m required to complete a research project.

It was important to me to ensure the research will be useful for the National Park. So I am looking at the effects of deer herbivory* on the regeneration of broadleaf woodland on areas of selectively-felled conifers.

* Herbivory is the eating/grazing/browsing carried out by herbivore species e.g. animals that have a diet composed entirely of plants.

I am conducting research at West Arnecliff Wood near Glaisdale. The woodland is designated as a SSSI (Site of Special Scientific Interest) and as a SAC (Special Area of Conservation). It is also classed as ancient woodland i.e. woodland has been present since at least 1600.

Six former conifer areas within the wood were chosen for the study – where conifers had been planted under established native broadleaf trees. The conifers had been felled in 2011 to help restore semi-natural woodland conditions. The felled conifers were all c. 40 years old and were mainly Western Hemlock (Tsuga heterophylla), but also included Douglas fir (Pseudotsuga menziesii), Grand fir (Abies grandis), Scots Pine (Pinus sylvestris) and various Larch species (Larix sp.). The removal of the conifers was part of the North York Moors National Park Authority’s long term efforts to encourage and support PAWS (plantations on ancient woodland sites) restoration.

In the six former conifer areas in West Arnecliff Wood, twelve fenced areas have been erected to exclude deer. The number of deer exclosures erected in a selectively felled area was proportional to the size of that area, although this was not always possible exactly due to extensive brash cover. The deer exclosures needed to be erected on areas as free of brash as possible. Six of the fenced areas include rabbit wire to exclude rabbits, while the other six allow rabbits to enter. As much as possible the fenced areas were kept to 6 x 6 metres, although the size and shape do vary because of obstacles on the ground.

A 4 x 4 metre quadrat has been created inside each fenced area to standardise the survey area. A 4 x 4 metre unfenced quadrat has been created next to each deer exclosure on similar vegetation to act as a control.

I completed the first vegetation surveys in March, and I will be carry out another series of surveys in the summer to compare plant growth within the fenced areas and without, in the unfenced areas next to them. I recorded lots of data during my surveys this spring, including the percentage cover and mean height of each species of plant in the quadrats, and the number of deer bites per species. I also recorded background data such as the number and species of mature trees within 20 metres of the quadrats so that the surrounding tree seed source is known. Geological data such as soil depth and the percentage cover of rocks/brash was also recorded.

The results of my research will inform the National Park Authority’s methods of PAWS restoration so as to ensure that once conifers are removed the long term regeneration of broadleaved ancient woodland species is given the best chance of success.