Lenoir J., Gégout J.C., Pierrat J.C., Bontemps J.D., Dhôte J.F. (April 2008)

1. Climate change and tree species elevation shift in French mountain forests: a contribution from early developmental stages Lenoir J., Gégout J.C., Pierrat J.C., Bontemps J.D., Dhôte J.F. (April 2008)

2. Context & Hypotheses Context & Hypotheses Materials & Methods Materials & Methods Results & Discussions Results & Discussions Environmental background : global warming The environment is evolving across several drivers of change (Sala et al., 2001) : - land use, climate, N deposition, biotic exchange, atmospheric CO2 - land use, climate, N deposition, biotic exchange, atmospheric CO2 Temperatures have been increasing at a striking pace over the last decades... Mean annual temperature trend in the world from 1861 to 2000 Source : IPCC 2001 1 For trees, fingerprints of climate change are obvious upon growth rates, breeding dates and even distribution margins The Earth’s climate has warmed by +0.6°C in annual average temperatures over the last century (Jones P.D. et al., 1999)

3. Context & Hypotheses Materials & Methods Results & Discussions Spatial pattern of tree species distribution in temperate forest ecosystems : - patchy and environmentally determined, emphasizes environmental determinism (Hutchinson, 1957) Species 1 Species 2 Probability of presence Species 3 Temperature (°C) 2 In this context of environmentaly determined distribution, how does tree species manage the changing conditions? Species distribution context : niche theory

4. Context & Hypotheses Materials & Methods Results & Discussions - remaining in the same distributions : adaptation, acclimatation, and plasticity Niche Evolution - remaining in the same distributions : adaptation, acclimatation, and plasticity Niche Evolution - changing distributions : migration, colonization, and extinction Niche Conservation Aim : assessing upward shifts of temperate tree species distribution in mountain forests 12°C 13°C 14°C 15°C 16°C 11°C 11°C 12°C 12°C 13°C 13°C 14°C 14°C 15°C 15°C Species evolve to adapt to new conditions Species remain at the same place Species remain in the same conditions Species change their distribution 11°C 12°C 13°C 14°C 15°C 16°C 3 Assuming conservatism of ecological niches in evolutionary time, we supposedpoleward and upward migration Hypotheses : the adaptation/migration tradeoff Two hypotheses concerning species distribution and climate change :

5. Context & Hypotheses Materials & Methods Results & Discussions highlands lowlands highlands lowlands 1 generation turnover (about 50-100 years) Stable conditions 1 generation turnover (about 50-100 years) 5°C 6°C 7°C 8°C 9°C 5°C 6°C 7°C 8°C 9°C Changing conditions t2 t1 Distribution comparison to assess changes : 6°C 7°C 8°C 9°C 10°C 5°C 6°C 7°C 8°C 9°C - analysing distribution of juvenile life stages between t1 and t2 Lack of old field observations including tree developmental stages information - analysing distribution between juvenile and adult life stages during t2 Seedlings reflect t2 whereas adults reflect t1 conditions at same locations (x,y) 4 We supposed upper distribution in elevation for juvenile life stages in comparison to adult life stages Tree species : large body size and slow generation turnover Large species with low generation turnover are at high risk of extinction :

6. Context & Hypotheses Materials & Methods Results & Discussions Sophy Vosges EcoPlant Jura Alpes Acer campestre Abies alba Prunus avium Adult life stage > 8 m high Quercus petraea Massif Central Acer pseudoplatanus Quercus robur Pyrénées Acer platanoides Acer opalus Corse Quercus pubescens Quercus ilex Betula pendula seedling life stage < 1 m high Fraxinus excelsior Carpinus betulus Sorbus aucuparia Castanea sativa Fagus sylvatica Sorbus aria - 3081 forest relevés from two floristicdatabases including life stage information - 17 temperate tree species with at least50 occurences for each life stages 5 We remained inside mature stands to compare seedlings and adults occurrences (0/1) at same location (x,y) Data collection : time period and sampling plots - 1986-2006 as a warmer period in french mountain ranges

7. Context & Hypotheses Materials & Methods Results & Discussions 1st decile + 25 m [2 ; 48] P < 0.05 Wilcoxon signed-rank test 5th decile + 24 m [-7 ; 55] P = 0.16 Wilcoxon signed-rank test 1st decile 5thdecile 9th decile 9th decile + 23 m [-12 ; 57] P = 0.24 Wilcoxon signed-rank test - Globally, seedlings displayed upper distribution in comparison to the adult life stage 6 No case studies have shown such a general pattern ofdifferences between seedlings and adults in lowland Differences between seedling and adult distributions Elevation (m)

8. Context & Hypotheses Materials & Methods Results & Discussions Abies alba + 99 m Acer campestre + 97 m Acer opalus + 190 m Acer platanoides - 13 m Acer pseudoplatanus - 164 m Carpinus betulus + 112 m Castanea sativa + 39 m Abies alba Fagus sylvatica - 14 m Fraxinus excelsior + 165 m Adult Prunus avium + 111 m Seedling Quercus petraea + 346 m Quercus pubescens + 42 m + 99 m Sorbus aria + 30 m Seedling upward shift Sorbus aucuparia - 120 m 7 upward shift of the seedling life stage 2 downward shift of the seedling life stage Mean shift : + 66 m [-8 ; 140] P = 0.08 7 Similar shifts have been provided at the upper margin for beech forest invading heather by 70 m(Penuelas & Boada, 2003) Differences in species optimum elevation between life stages

9. Context & Hypotheses Materials & Methods Results & Discussions Environmental conditions are different Human induced modifications Seedlings and adults autecology are different Biologically induced modifications Land-use change Land-use change Ontogenetic niche shift (Parrish & Bazzaz, 1985; Collins & Carson, 2004; Miriti, 2006) Mature forest stands below tree line Climate change Change in climatic requirements during species life span Nitrogen deposition Nitrogen deposition Non-directional regarding species response Change in biotic interaction during species life span CO2 increases CO2 increases Non-directional regarding species response Alien species Alien species No exotic species in our analysis 8 Climate change is not the only driver of changes but this is the most reliable and concordant (+ 0.4°C, 0.6°C/100m) Distribution differences : abiotic or biotic driver of change Mature forest stands below tree line Shift equivalent to + 0.4°C (0.6°C/100m) Non-directional regarding species response Non-directional regarding species response This general pattern of differences could also be explained by change in species autecology during life stage successions No exotic species in our analysis

10. Conclusion - Seedlings and adults displayed different distribution along the altitudinal gradient - There is a general pattern of differences between tree life stages distributions - Here we observed for the first time significantdifferences between tree life stages at low elevation Present distribution of seedlings in comparison to adults suggests a wide acting driver of difference : 1) Human-induced climate change 2) Change in species-environment relationships during life span …whatsoever, in both case, temperate tree species will benefit from climate warming through seedling survival at high elevations...

11. Thank you for your attention...

12. French Alps Narrow range of T°C variation with latitude ~ 1°C per 200 km Altitudinal vegetation staging(Humboldt, 1805) North Alps 7.5°C + 3°C Wide range of T°C variation with elevation ~ 1°C per 200 m South Alps 10.5°C North Alps Silver Fir Silver Fir distribution along T°C and elevation S N South Alps Silver Fir Silver Fir optimum elevation is higher in South Alps Silver Fir optimum T°C remains the same Assessing distribution changes : poleward or upward shifts? We confirmed conservatism of the ecological niche for T°C and supposed upwardshifts in warmer conditions

13. Abies alba Acer campestre Upward Upward + 97 m + 99 m Castanea sativa Fagus sylvatica Quercus petraea Sorbus aucuparia Carpinus betulus Quercus pubescens Fraxinus excelsior Sorbus aria Prunus avium Acer pseudoplatanus Acer platanoides Acer opalus Downward No change Downward No change No change Upward Upward No change Upward No change Upward Upward + 42 m + 39 m - 120 m + 30 m + 190 m - 13 m + 112 m - 14 m - 164 m + 111 m + 346 m + 165 m Quercus petraea Acer opalus Fagus sylvatica Acer platanoides Prunus avium Acer campestre Fraxinus excelsior Sorbus aria Sorbus aucuparia Abies alba Carpinus betulus Acer pseudoplatanus Castanea sativa Quercus pubescens Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Seedling Seedling Seedling Seedling Seedling Seedling Seedling Seedling Seedling Seedling Seedling Seedling Seedling Seedling - 164 m - 14 m - 120 m + 39 m + 112 m + 346 m + 190 m - 13 m + 165 m + 42 m + 97 m + 111 m + 30 m + 99 m No change in optimum Seedling upward shift No change in optimum Seedling upward shift No change in optimum Seedling downward shift Seedling upward shift No change in optimum Seedling upward shift No change in optimum Seedling downward shift Seedling upward shift Seedling upward shift Seedling upward shift 7 upward shift of the seedling life stage 2 downward shift of the seedling life stage Mean shift : + 66 m [-8 ; 140] P = 0.08 Differences in species optimum elevation between life stages

14. Acer opulus Adult recorded presence Seedling recorded presence Adult response curve Seedling response curve - Lower resolution at high elevation than in lowlands Adult normalised curve Seedling normalised curve - Logistic model to take unevenness into account (Ter Braak, 1986) Area curve differences Uneven distribution of plots with elevation and logistic regression - Wider variation in differences between life stages at the 9th decile 14 species displayed significant unimodal response curve at both life stages

15. Adult skewed distribution and seedling occurrences at high elevations Distribution differences for Quercus petraea Quercus petraea

16. Logistic models Adult Seedling Adult Seedling HOF models Skewed distribution and logistic regression limits