How to grow a 300 year-old tree

Duncan StoneScottish Natural Heritage

Introduction

ObjectiveCentral woodland

conservation objective – to grow native trees that

thrive for their long natural life

ResponsePlant or regenerate

locally native trees, and wait for 300 years

Conservation, landscape and cultural values and functions associated with big, old trees

• ‘Large-diameter trees dominate the structure, dynamics, and function of many temperate and tropical forest ecosystems and are of considerable scientific and social interest… [and] contribute disproportionately to forest structure and function after they die.’1

• ‘…forest stands that include...large trees have been found more attractive.’2

• ‘A sure cure for seasickness is to sit under a tree’3

31. LUTZ, J.A., et.al., 2012. Ecological Importance of Large-Diameter Trees in a Temperate Mixed-Conifer Forest. PLoS ONE, 7(5), pp. 1-15.2. RIBE, R.G., 1989. The aesthetics of forestry: What has empirical preference research taught us? Environmental Management, 13(1), pp. 55 y

Letters, 11(6), pp. 588-597..3. Spike Milligan

Implications of a multi-century timescale to grow the future’s big old trees

1. Very substantial environmental changes expected (climate change, novel pests and pathogens) – and consequences on tree health

Patterns of tree health problems

• Up to 1920s: most invasive pathogens in Europe were long-established species that simply extended their range

• After the 1920s, the most invasive pathogens were alien species arriving mainly from North America,

• In the last 30 yrs, the rate of forest pathogen invasions into Europe has escalated exponentially, with a great increase in the number of pathogens from Asia and the appearance of new hybrid species1 1. Santini, A. et. al, 2013. Biogeographical patterns and determinants of invasion by forest pathogens in Europe. New Phytol. 197, 238–250.

Cumulative serious tree pathogens in UKFraxinea chalara. Ash

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Newly lethal natives: Mountain pine Beetle, Dendroctonus ponderosae

Dothistroma Needle Blight

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UKCIP09 predictions - average temperature Scotland

• Anomaly above 1961-1990 baseline (50% estimate, high emissions track)– 2020 = 1-2C– 2050 = 2-3C– 2080 = 3-4C

– Observed average temperature change 1961-2004 = 1C

Potential impacts - Climate change• The most important effects of climate change on temperate

forests will probably be mediated through changes in disturbance regimes such as storms, insects and pathogens (2)

• Most pathogens will be able to migrate…at a faster rate than tree species… their ability to adapt to new climatic conditions will be greater than that of their long-lived hosts. (1)

• …accelerated development and lowered mortality rates for various species of insect herbivores…incidence of mass outbreaks of pest species will rise…especially bark beetles, allowing additional generations and multiplying population densities. Range expansions and range shifts are to be expected…(2)

1. Sturrock, R. et.al (2011), Climate change and forest diseases. Plant Pathology, 60: 133–1492. Lindner M. et.al. (2010) Climate change impacts, adaptive capacity, and vulnerability of European forest ecosystems. Forest Ecology and Management 259(4) 698–709

Implications of a multi-century timescale to grow the future’s big old trees

1. Very substantial environmental changes expected (climate change, novel pests and pathogens– and consequences on tree health

2. Resilience measures need to cover several centuries…current ‘no-regrets’ approaches can’t be tested or targeted, and seem unlikely to be sufficient

Ash diebackChalara fraxinea

Novel pathogens:

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Connectivity and range shifts

• models predict migration rates of 1000m per year or higher to be necessary to track habitat under CO2 climate forcing

• Actual post-glacial migration rates - less than 100m per year.

• models predict for very low probabilities of dispersal beyond 10–20 km from current species boundaries by 2100 – about 100–200m per year (for 5 tree species in the eastern United States)1

141. Aitken, S.N., et. al., 2008. Adaptation, migration or extirpation: climate change outcomes for tree populations. Evol. Appl. 1, 95–111.

Implications of a multi-century timescale to grow the future’s big old trees

1. Very substantial environmental changes expected (climate change, novel pests and pathogens – and consequences on tree health

2. Resilience measures need to cover several centuries…current ‘no-regrets’ approaches can’t be tested or targeted, and seem unlikely to be sufficient

3. We can’t wait until the uncertainty diminishes – we have to make smart, resilient choices now

Inherent uncertainties are unavoidable

• Waiting for improved evidence and information cannot be the solution. Decision makers in forest management have to realise that they must take long-lasting management decisions while uncertainty about climate change impacts are still large.1

1.Lindner, M., et.al., 2014. Climate change and European forests: What do we know, what are the uncertainties, and what are the implications for forest management? J. Environ. Manage. 146, 69–83.

So what do we do?

Don’t put all your eggs in one basket…

Alladale pinewood

Rassal ashwood

What would greater diversity look like? 1. Don’t limit ourselves to single approaches

• No more of ‘The right tree in the right place’• UK Forestry Standard• Best Practice Guidance• Common Standards • SCM generic targets• ‘Planting…should use indigenous origin

planting stock from well-matched sites in the locality.’ (FCS Seed Sources for Planting Native Trees and Shrubs in Scotland)

What would greater diversity look like?2. a greater tree species diversity

• Non-local genotypes – e.g. oak from Southern England

• Replacement species – e.g. sycamore for elm and ash

• Pre-emptive diversification – e.g. small proportions of analogue species like Norway spruce for Scots pine

Degelia cyanoloma, ‘a characteristic species of the Celtic Rainforest.’On Sycamore (Acer pseudoplatanus), Isle of Muck, June 2012

Non-native contributions• Felled Norway spruce

logs in Abernethy Natura Caledonian pinewood now the most important Scottish habitat for Buxbaumia viridis (Green Shield moss) – also a Natura feature Taylor, S. 2010 Buxbaumia viridis in Abernethy Forest and other sites in

northern Scotland. Field Bryology 100 (also photo)

What would greater diversity look like?3. making no changes in some places

• The range of our uncertainty includes scenarios where – We rapidly reduce the rate and scale of climate

change– We introduce really effective biosecurity controls

• Thus reference sites are also essential.

What happens next?

• A lot of talking…FCS, SNH, NGOs…you!• Probably no final answer…• Risk-based approaches rather than

assumptions of certainty• Thinking about the potential vulnerability of

other ecosystems, e.g.:– Monocultures of heather?– Sphagnum losing competitive edge to flowering

plants with increasing temperature?

Finally - redefining ‘native’?

• Should native-ness be an unchanging definition?

• Varies across location – why not across time?– ‘native to pre 21st Century Scotland’ – ‘native to 21st-23rd Century Scotland

Thank you

Natural selection and genetic adaptation

• The evolutionary processes of Scots pine and Silver birch have been modelled1 as only adapting ing expected climate change at about 25% of the rate required

• ‘Overwhelming’ factor is the persistence of maladapted old trees preventing the establishment of seedlings better adapted to a changed environment

• Removal of old trees could speed up natural selection…

1. Kuparinen, A., Savolainen, O., Schurr, F.M., 2010. Increased mortality can promote evolutionary adaptation of forest trees to climate change. For. Ecol. Manag. 259, 1003–1008.