Resilience Trial Planting at Candacraig Estate

Above: Candacriag Estate where wind blow compartments  are being restocked trialling a number of different conifer and broadleaved species

The Candacraig Estate spans approximately 1,700 hectares of primarily coniferous woodland. RTS Forestry successfully applied for a Grant for Resilient Woodlands for 20,350 trees to restock the windblow compartments. Veronica Llorente from RTS Forestry tells the story:

These windblow compartments have presented a unique opportunity for the estate to embark on experimental restocking and restructuring plans. These plans aim to assess quality timber growth potential, explore natural regeneration, and transition to continuous cover management. The species chosen will ensure a woodland resilient to climate change and future pests and diseases.

The overarching goal of the project is to enhance the estate’s resilience. The predominant estate species currently are Sitka Spruce and Scots pine. This reliance on just two species has led to concerns about the resilience of the woodland. Potential risks come from future pathogens, diseases, and climatic changes which are likely to increase severe weather events. Alternative  tree species that could thrive while contributing a valuable timber resource are therefore being considered.

Site Description

The climate at Candacraig is predominantly cold with chilly winters and mild summers. The region receives an average annual rainfall of around 1,000mm. Average temperatures typically range between 3 and 10 degrees Celsius. The microclimate in this area is characterized by higher rainfall and lower temperatures compared to the broader Aberdeenshire region. It features gently sloping terrain some of which is of elevated altitude and surrounded by mature woodlands. This area is part of the resilience trial.

The total area for the project is approximately 10hectares (ha)  with 70% being planted and 30% put forward for natural regeneration.

The local soils primarily consist of brown earth with occasional pockets of mineral podzols which are generally regarded as relatively nutrient-poor.

All coupes range in size from 0.5 to 2 ha and are situated along a 5km stretch of the same glen, sharing similar topography.

Species Selection

The species chosen are either new to the woodland or are already present and successful on the estate. Different methods of protection against deer damage are tested and monitored for their effectiveness in preventing browsing. These include deer control and the application of a deer scent deterrent, Trico.

Species chosen were:

Conifers

• Douglas fir – Pseudotsuga menziesii
• European larch – Larix decidua
• Macedonian pine – Pinus peuce
• Scots pine – Pinus sylvestris
• Serbian spruce – Picea omorika
• Sitka spruce – Picea sitchensis
• Western hemlock – Tsuga heterophylla
• Western red cedar – Thuja plicata

Broadleaves

• Aspen – Populus tremula
• Grey willow – Salix cinerea
•  Aspen – Populus tremula
• Rowan – Sorbus aucuparia

All selected tree species are categorised as suitable or very suitable according to the Environmental Site Classification (ESC V4). The only exception is Serbian spruce; however, this species is believed to thrive in the site’s consistently moist conditions, deep soils, and has been successful within the estate’s ground.

The size of trees (20-40cm) selected is correct for conditions, exposure and expected weed competition. Native broadleaf species are sourced from local Aberdeenshire provenances.

Operations

There has been a range of ground preparation techniques utilised. Most compartments have been scarified, as this has previously been successful for establishing trees at Candacraig in the past. Some areas had a high amount of brash which was not accessible by a scarifier. Those areas were targeted to mounding operations and the remaining areas were flat-planted.

The timing of planting was influenced by local weather due to the estate being susceptible to snow and frost. The Estate’s policy is to plant everything by the end of April.

Data Collection

The small restocking areas – compared to the estate’s size – have minimal impact on tree species diversity. However, the data collected from these restocking efforts will inform future planting decisions and will enhance biodiversity by creating more varied woodlands and habitats.

Data collected will include assessing tree health, measuring resistance to weevils, recording height variations, and tracking mortality rates. Each of these metrics plays a crucial role in understanding the overall well-being and resilience of the trees, aiding in effective management for the future.

All planting has been done at commercial densities of 2,700 stems per hectare to reduce to 2,500 after natural mortality. One compartment, a mix of pine species, Scots pine and Macedonia pine, has been planted at 3,000 to trial increased density planting. With deer fence unfeasible on a small scale and potential weevil damage not being controlled with Gazelle from July 2024, other measures will be examined.

The trials extend into areas designated for natural regeneration, serving as a dynamic testbed for the implementation of low-impact silvicultural systems (LISS) management. This approach is firmly rooted in sustainability and emphasizes the preservation of a stable forest canopy that supports natural processes vital for biodiversity.

Deer Management

Above: sprayed with Trico deer repellent

The project involves various tree protection methods, encompassing traditional stalking, deer control, and innovative alternatives like Trico-scent deer repellent. Trico is derived from sheep fat and is proven effective in safeguarding trees from deer browsing.

Trees specified to be treated with Trico will be sprayed post-planting with undiluted Trico (application amount is based on tree size varying between 8 to 10 ml.) The different trial areas will be consistently monitored with findings informing future management strategies. All native broadleaves (aspen, rowan and willow) onsite are protected with standard tree shelters and wooden stakes- those in the suitable location on the identified wettest site.

Conclusion

A significant goal of the project is to produce quality timber and experiment with different species that might be more adaptive to climate change in northeast Scotland. As the climate gets wetter and warmer the suitability of Sitka and other species currently relied on may become less ideal.

The management objectives of the restructuring plan following significant wind damage, encompasses a multi-faceted approach aimed at enhancing resilience and adaptability in Candacraig’s woodlands.

More Information

If you are interested in learning more about this project, please email us at rfshq@rfs.org.uk

Grants for Resilient Woodlands

Our Grants for Resilient Woodlands are funded by Train Hugger and Green The UK. They are open for applications from Royal Forestry Society (RFS) and Royal Scottish Forestry Society (RSFS) members all year round.

These grants are to help people plant trees that will survive and thrive into the future. Creating better, more resilient treescapes for our environment, for people and for the economy.