silviculture and management of ash: best practice advice for woodland managers

LAP Ash Dieback Workshop

Silviculture and management of ash:

best practice advice for woodland managers

Edward Wilson Silviculturist

Chalara Ash Dieback Workshop Tamar Valley AONB Helping Hands for Heritage Event The Oak Room, Tiverton, Devon 13 August 2015

First presented: 18 06 2014 This version: v2.0, 13 08 2015

RESEARCH

I N T E R N A T I O N A L

Outline

• Threat to forests in Britain

• Modern Silviculture: adaptation and resilience

• Principles underlying guidance for ash

• Management options: – Uninfected stands

– Infected stands

– Older stands

– Coppice

– Urban/parkland/hedgerow trees

• Further information

• Questions and Discussion

Guiding Principle

‘All our resolves and decisions are made in a mood or frame of mind which is

certain to change.’

Proust

Review: Threats to UK Forests

Source: Forestry Commission England 2012

• Climate change

– Summer droughts increasingly likely, especially in South and East

– Extreme rain and flooding events are more likely

– Ecosystem change – especially ground plants

• Pests and diseases

– Native and exotic

• Low Resilience of Existing Forest Resources

– Low number of productive species

– Monoculture stands are most common

United Kingdom Forestry Standard Major Policy Documents in British Forestry

See www.forestry.gov.uk for archive of literature – technical, scientific and policy

http://www.forestry.gov.uk/

Ecological Resilience

• Resilience is the capacity of an ecosystem to respond to a disturbance by resisting damage and recovering quickly

• Not a new concept, but perhaps newly relevant to forestry – Holling, C. S. 1973. Resilience and stability of ecological systems .

Annual Review of Ecology and Systematics 4: 1-23 – now >5800 citations (to July 2014)

• Types of disturbance – Stochastic: fires, flooding, windstorms, insect population explosions – Human activities: deforestation, introduced exotic plants/animals

• Disturbances and regime change – sufficient magnitude or duration of disturbance → profound affect on

ecosystem → threshold (“tipping point”) → different regime of processes and structures predominate

Rumsfeldian “Ecology”

• There are known knowns; there are things we know we know.

• We also know there are known unknowns; that is to say, we know there are some things we do not know.

• But there are also unknown unknowns – the ones we don’t know we don’t know.

Donald Rumsfeld US Secretary of Defense,

12 February 2002

The threat of climate change

Source: UK Meteorological Office

BUT!!!! Remember that our concern is not just with temperature. The predictions all point to more instability in terms of windiness, rainfall, storm events, etc. All are aspects of global climate change that foresters need to consider in their long-term planning.

What Ecological Site Classification (ESC) suggests in terms of the dominant productive species

Effects of climate change on the identity of the most productive conifer species as predicted by Ecological Site Classification for the UKCIP02 2050s High and Low emission scenarios.

ESC is based on temperature, moisture and soil physical properties It does not consider Dothistroma, or any other pests or diseases.

Source: Forestry Commission

Risk to woodlands on the Public Forest Estate

By the 2080s, there is a risk of 65% of the PFE being classed as ‘unsuitable’ in the absence of adaptation – a potential 35% decline in productivity

Source: Forestry Commission 2012

The evolution of silviculture Summary of the major dimensions and trends

Primary Focus

Unit of Production

Tree

Ecosystem

Ecological Factors

Stand Structure

Pure, regular

Mixed, irregular

Stand Dynamics

Simple

Complex

Management Factors

Objectives/Issues

Single, discreet

Multiple, integrated

Decision-making

Professionals

Informed public

Source: Wilson 2000

Climate Change Action Plan for the Public Forest Estate

We will adopt the principle of anticipatory adaptation. This offers the highest potential gains for forest resilience, and the benefits they provide.

We will take an approach that is ‘not risk averse’.

Global emissions are currently tracking close to some of the more extreme emissions scenarios that have been published, so it is prudent to consider the 2050 high scenario when planning for the future.

Diversification is the theme!

Succession stages in a natural forest

initial stage intermediate stage

open ground

final stage

Strategies for Enhancing Resilience

Modify thinning regimes Extend “rotations”

Diversify Structure - CCF

Species choice - genetics/provenance

Mixed species

Assisted migration of native species

New species introduced

Wider use of “minor” species

Diagram: Jens Haufe

Alternative Species Chinese mahogany (Toona sinensis) After 2 growing seasons Westonbirt Arboretum Photo: E. R. Wilson

Prolific ash natural regeneration in a small canopy clearing – lots of competition and selection

Photo: Sharon Rodhouse

New native oak plantation. Note close spacing to promote form, competition and natural selection. Photo: E. R. Wilson

Continuous Cover Forestry

• “...the use of silvicultural systems whereby the forest canopy is maintained at one or more levels without clear felling.”

Mason et al. 1999

It has 4 main guiding principles:

1. Managing the forest ecosystem

2. Using natural processes

3. Working within site limitations

4. Diversifying stand structure

Prime movers: ProSilva Europe (1989) and CCFG (1991)

final harvest and

regeneration

young growth stage

H<1.3m

pole stage

DBH>10cm DBH<20cm

small timber stage

DBH>20cm DBH<35cm

medium timber stage

DBH>35cm DBH<50cm

DBH>50cm

large timber stage thinning

thicket stage

H>1.3m DBH<10cm

respacing

fallow stage restocking

final harvest Beat up, tending

In order to transform a planted forest we have to:

• develop adequate tree stability (Frame Trees).

• promote the best trees as likely source for Natural Regeneration (NR)

• get the species composition right

• create optimal conditions for NR (ground vegetation, seedbed, browsing)

Stand development and transformation

Source: Jens Haufe

Modified first thinning in Douglas fir Wythop Wood, Cumbria

Photo: G. Browning

Frame tree and natural regeneration Douglas fir stand, Wythop Wood, Cumbria

Photo: G. Browning

Light demand of conifer seedlings

Species Overstorey BA for

seedling stablishment [m2/ha]

Overstorey BA for seedling growth

[m2/ha]

Shade tolerance of seedlings

JL/EL 20-25 15-20 Intolerant SP/LP/CP 25-30 20-25 SS 30-35 25-30 Intermediate DF 35-40 30-35 NS

40-45 35-40 Tolerant

WH

leader/lateral shoot ratio > 1

Management of Seedling Establishment and Growth

Note: Light demand for seedling establishment may be considerably lower than for seedling growth.

management of light level is important

(Source: Forestry Commission Operational Guidance OGB 7)

Single and group tree selection in Douglas fir Mixed-species regeneration

Photo: E. R. Wilson

Lowland broadleaved shelterwood

Sharon Rodhouse 2007

Management Guidance and Advice for Ash

Ash Silviculture and Management Principles

• Maintain the values and benefits associated with ash woodlands and iconic trees;

• Secure an economic return where timber production is an important objective;

• Reduce the presence and rate of spread of Chalara dieback;

• Maintain as much genetic diversity in ash trees as possible with the aim of ensuring the presence of ash in the long term; and

• Minimise impacts on associated species and wider biodiversity

Source: Forestry Commission 2013, Royal Forestry Society 2014

Reporting suspected cases of Chalara ash dieback (1)

• Check ash plantations and woodlands regularly during the growing season for signs of Chalara ash dieback disease

• Look for:

– leaf wilting and premature browning in the growing season

– Shoot dieback and epicormic sprouting

– Characteristic diamond-shaped lesions on stems at branch unions

• Check current guidance for disease signs and symptoms – see www.forestry.gov.uk/chalara

Photo: E. R. Wilson 2014

Photo: E. R. Wilson 2014 Photo: Forest Research

http://www.forestry.gov.uk/chalara


• Three ways to report suspected cases of ash dieback:

1. Forestry Commission’s Tree Alert app – see www.forestry.gov.uk/treealert, Google Play or App Store

2. Forestry Commission on-line reporting form - www.forestry.gov.uk/treealert

3. Defra hotline on 08459 33 55 77

• Respondents are asked to enter the code '6/20' in the 'Additional notes' field of the app or online reporting form or to mention this when reporting through the hotline.

• Removal of infected trees. See latest Forestry Commission guidance - http://www.forestry.gov.uk/forestry/INFD-979BZJ


http://www.forestry.gov.uk/treealert

http://www.forestry.gov.uk/treealert

http://www.forestry.gov.uk/forestry/INFD-979BZJ




• Grant Aid. Death of ash trees on sites currently within an active grant or farm woodland scheme should also be reported to the office administering the scheme www.forestry.gov.uk/england-areas

• Re-planting. Financial support available for removal of diseased trees and re-planting with alternative species on sites planted under the English Woodland Grant Scheme and now subject to Chalara dieback (in counties designated as high and medium risk only). Work can only commence following approval of grants.


http://www.forestry.gov.uk/england-areas



Silviculture and management options for ash 1. Uninfected stands

1. Planning Before taking any action, owners/managers need to review their management objectives and local circumstances.

2. Silviculture Carry on with planned work and thin to promote fast, healthy growth in selected trees.

3. Biosecurity Adhere to guidance on biosecurity, ensure tools are disinfected, boots and clothes cleaned and ash leaves are not moved from the wood

4. Monitoring Regularly monitor trees for signs of Chalara and, if found, report to the Forestry Commission (see earlier guidance).


Silviculture and management options for ash 2. Infected stands (<25 years)

1. Where there are low levels of disease

– Young Plantations Remove recently planted trees and natural regeneration if small numbers are infected and burn or bury them on site.

– Pole-Stage Stands Thin woodland as usual. Select diseased trees for thinning which show symptoms of Chalara, preferably when in full leaf to ensure the right tree is felled, and where possible burn the brash.

– Coppice Do not bring forward coppicing of ash as this will make stools and new growth more vulnerable to Chalara.



2. Where there are high levels of disease (>50% stand infected)

– Support Research Do not rush to remove recently planted or mature trees, or ash coppice. This will prevent identification of resistant trees.

– Realise Timber Value Consider felling ash to realise the value before timber condition deteriorates or thin to favour alternative species.

– Biodiversity Consider leaving some trees close to dying for deadwood and biodiversity. Restock with alternative species suitable for local site conditions and to emulate the ecological value of ash (see Natural England guidance). Validate the provenance of any new stock with your nursery prior to purchase.


Natural England Guidance for management of woodlands of conservation importance

• Assessing and addressing the impacts of ash dieback on UK woodlands and trees of conservation importance

• Published on 30 April 2014

• http://publications.naturalengland.org.uk/publication/5273931279761408

http://publications.naturalengland.org.uk/publication/5273931279761408




3. Where timber production is not a consideration

– Habitat Conservation The aim here is to retain ash in the wood for as long as possible to provide habitat for species dependent on ash and to allow time to identify trees that may be resistant.

– Commitment to Management Continuing to manage the wood will ensure less spore production and more light on the woodland floor to encourage regeneration and structural diversity.


Silviculture and management options for ash 3. Infected older stands

• Adopt an individual tree approach

– There should be a presumption against the felling of ancient, veteran or mature ash trees, whether or not they are infected with Chalara.

– Where less than 50% of the crown is infected the tree should be regularly monitored and symptoms of honey fungus (Armillaria) – often it is this secondary infection that kills the tree.

– Where more than 50% of the crown is infected consider felling.

– Health and Safety around Dead and Declining Trees Take special care and appropriate measures where trees are in areas close to public access.


Ash and oak planted mixture, Suffolk Photo: Gary Battell

Ash being managed for firewood, Suffolk Photo: Gary Battell

Silviculture and management options for ash 4. Coppice Woods

• Coppice

– Where there are low numbers of infected coppice stools in the wood consider killing them.

– Attempting to regenerate a wood from coppice stools is not recommended as coppice re-growth is likely to be infected.

– Avoid carrying out traditional coppice operations where ash forms >30% of the canopy.


Ash coppice, Suffolk Photo: Gary Battell

Silviculture and management options for ash 5. Urban/parkland/hedgerow trees

• Litter Removal There is evidence that removal of leaf litter combined with the lower humidity in urban and parkland environments can significantly reduce and slow the impact of Chalara.

• Wider Benefits There should not be a presumption to fell infected trees in these environments as these trees can continue to provide benefits even when dead.

• Health and Safety Carry out a full risk assessment before taking action. Public safety is of paramount importance in this assessment.


New Woodland Considerations: - Management objectives - Site-based silviculture - Diversify species choice - Consider ecological alternatives (Natural England Guidance) - Consider mixtures

Mixed native woodland Golden Wood (Green Light Trust)

Lawshall, Suffolk Photo: E. R. Wilson 2014

Principles of ESC are well-established

ESC is a knowledge-based model; productivity

distribution data are used to inform decisions

ESC was developed to support commercial

species selection Also analysis of National Vegetation

Classification community types

Detailed species information, including some provenance guidance

ESC does not consider rising CO2 levels or plant

health issues

Ecological Site Classification (ESC) A Cornerstone of site-based silviculture

Wider Environment: A mature ash tree with Signs of Chalara ash dieback disease

Photo: Sharon Rodhouse 2012

Be vigilant! Early identification of infected trees will give more

options for management and conservation of woodlands

Early signs of Chalara ash dieback on current year leaves Frithy Wood (Green Light trust) Lawshall, Suffolk. 17 June 2014 Photo: E. R. Wilson 2014

Supporting Forestry Research is Vital Become an Applied Scientist

Ash Genetics Trial Photo: Jo Clark, Earth Trust

The Forest Research Site at Pound Farm, Woodland Trust, Suffolk. Photo: E. R. Wilson 11 August 2015

Conclusions

• Resilience - theoretical framework within which we can ensure sustainable management of natural resources

• Working with Uncertainty – in all future decisions and actions

• Implications for forestry in the UK

– Diversification of genotypes, species and structures

– Site-based decision making

• Global issues require local, site-specific solutions

"A gentleman takes as much trouble to discover what is right as lesser men will take to discover what will pay." K'ung Fu-tzu (Confucius), quoted by M.L. Anderson 1951

Decision making

Reference: Anderson, M.L. 1951. The Selection of tree species: an ecological basis of site classifications for conditions found in Great Britain and Ireland. Oliver and Boyd, Edinburgh. 151 pp.

References, Further Information and Guidance

• Forestry Commission

– www.forestry.gov.uk/chalara

– 08459 33 55 77 (Defra hotline - open 8am - 6pm every day)

– [email protected]

• Natural England

– Assessing and addressing the impacts of ash dieback on UK woodlands and trees of conservation importance: http://publications.naturalengland.org.uk/publication/5273931279761408

• Royal Forestry Society – Managing Chalara fraxinea (Ash Dieback): Guidance for woodland owners and managers (May 2014)

– http://www.rfs.org.uk/files/Managing-chalara-ash-dieback_May2014.pdf

• Kent Downs AONB – Guidance on Ash Management

– www.kentdowns.org.uk

• Future Trees Trust

– www.futuretrees.org

http://www.forestry.gov.uk/chalara

mailto:[email protected]


http://www.rfs.org.uk/files/Managing-chalara-ash-dieback_May2014.pdf







http://www.kentdowns.org.uk/

http://www.futuretrees.org/

livingashproject.org.uk Project partners:

LAP Ash Dieback Workshop

Acknowledgements

My thanks to the following colleagues and organisations: Jo Clark, Earth Trust; Tom Brown, Green Light Trust; Sharon Rodhouse, Sylvatic Ltd; Gary Battell, Suffolk County Council; Jens Haufe, Forestry Commission; Gareth Browning, John Weir and Barnaby Wylder, Forestry Commission England; Forest Research; Royal Forestry Society

Contact Information

Edward Wilson

Email: [email protected]

Web: www.silviculture.org.uk

First presented: 18 06 2014 This version: v2.0, 13 08 2015

RESEARCH

I N T E R N A T I O N A L