Changes in Plant Community Composition Lag Behind Climate Warming in Lowland Forests

Bertrand et al. 2011

Introduction

Supplementary figure 1. Spatial distribution of lowland (<500m) and highland (500-2,600m) forests across France.

•Lag between climate warming and biotic response previously reported.Latitudinal and altitudinal shifts

•Velocity of climate change greater in lowlands than in highlands.Does the lag correspond?

•France a good model due to recent warming and topography.France (+1.05°C)Worldwide (+0.35°C)

The Study System•French forests from 1965-2008“Climatic warming period” 1986

onward

•76,634 floristic surveys

•3 French databases (EcoPlant, Sophy, and French National Forest Inventory)

•Climate data obtained from 237 meteorological stations.

Supplementary Figure 3. Location of floristic surveys across France

1965-1986 (~10,000 surveys) 1986-2008 (~65,000 surveys)

The Study System•Floristic surveys consisted of 760 species.short life spans and high population

turnover rates

•Cosmopolitan species (385)Widespread, generalist, potential

invasive

•Thermophilous/Mediteranean species (78)warmth loving

•Sub-mountainous/Lowland species (52)

•Mountainous/Alpine species (144)

Climate and Floristic Models•Climatically reconstructed temperatures calculated from meteorological data applied to climate models.Monthly mean temperatures at a

1-km2 resolution

•Shows high confidence in floristic models

Supplementary Figure 7. Mean annual temperatures (°C) predicted from the floristic model vs. mean annualclimatically reconstructed temperatures.

Climate Flora Equilibrium

Figure 1. Theoretical response of plant communities to climate warming.

Results

Figure 2. Comparison of floristically (green) and climatically (red) reconstructed temperature trends between 1965 and 2008. Dashed line indicates start of contemporary climate warming period.

Lowland Highland

ResultsTable 1. Comparison of floristically and climatically reconstructed temperatures.

• Lowland plants responded to 0.02°C of 1.11°C increase in temperature.• Highland plants responded to 0.54°C of 1.07°C increase in temperature.**

Explanations for Lowland Lag: Persistent species

Lowland – 75.2% cosmopolitan, 15.3% Thermophilous

Highland – 67.2% cosmopolitan, 8.8% Thermophilous

•No significant changes in lowland plant community composition

•Mountainous/Alpine species decreased -4.6% in highland areas.

•Cosmopolitan species increased +5.1% in highland areas.

Figure 3. Compositional changes in the plant communities of lowland and highland forests according to four different biogeographic groups.

= statistically significant

Explanations for Lowland Lag: Few Short-Distance Escapes•Limited dispersal abilities

•Latitudinal (northward) vs. Altitudinal (upward) migration

•Isotherms shifted 35.6km in lowlands and 1.1km in highlands.

Supplementary figure 9. Mean annual temperatures across France

1965-1986 1987-2008

Explanations for Lowland Lag: Habitat Fragmentation

Supplementary figure 10. Spatial analysis of forest territory across France.

Area of forest patches Proximity index• Forest patches

>5km2 cover 67.3% of highlands.

• Forest patches >5km2 cover 29.1% of lowlands.

Conclusion• Velocity of climate change in lowlands greater than in highlands.

• Lowlands responded to 0.02°C while highlands responded to 0.54°C * of climate warming.

• Explanations: Persistent species, dispersal abilities, short-distance escapes, and habitat fragmentation all play a role.

• Slow response of lowlands may lead to biotic attrition.

• Conservation efforts focused on highlands, though lowlands need attention as well.

Discussion Questions•Does this paper give enough evidence for refocusing conservation efforts on lowland areas, due to the suggested biotic attrition that could result from the lag?

•The authors suggest that adaptation is more prevalent in lowlands while migration is more prevalent in highlands, do you think this claim has any real substance?

•Do you think the inclusion of figure 1. (the theoretical one) in the paper was helpful in your understanding or could it have been omitted?

•Could more extensive floristic surveys in recent times (~65,000) as opposed to earlier (~10,000) affect the significance of the data? The floristic model was calibrated using data from before the warming period.

•How would the results change if both landscapes were continuous (less fragmentation in lowland areas)?

•The species chosen for the floristic models had short life spans and high population turnover rates. Do you think Floristically reconstructed Temperatures of longer lived species would show a similar trend?

•What effect do land use changes have on the ability for plants to migrate in response to climate change (think habitat fragmentation)?

•What is the most important way this paper contributes to our understanding of biotic response to climate change?