Aim.The functional trait composition of plant communities is thought to be largely determined by climate, but relationships between contemporary trait distributions and climate are often weak. Spatial mismatches between trait and climatic conditions are commonly thought to arise from disequilibrium responses to past environmental changes. We here investigated whether current trait-climate disequilibrium were likely to emerge during plant functional responses to Holocene climate warming. Location.North America Time period.14-0Kya Major taxa studied. Terrestrial plants Methods. We joined global trait data with paleoecological time-series and climate simulations on 425 sites. We estimated plant community functional composition for three leaf traits involved in resource use. We then quantified disequilibrium in plant trait temporal responses to climate change during two contrasted periods : a period of high climate variability (14-7 Kya), and a period low climate variability (7-0 Kya). Results. Functional trait composition showed consistent deviation from climatic equilibrium during both periods. The temporal dynamics of trait composition tends to be positively correlated to climate equilibrium expectations during Holocene climate warming (14-7 Kya), but not during a following period of low climate variability (7-0 Kya). Main conclusions.Long-term functional responses of plants to climate change showed mixed evidence for both equilibrium and disequilibrium responses. Temporal trait dynamics were closer to spatial dynamics expectations under high climate variability, indicating that relevance of space-for-time substitution might be partially dependent on climate variability. Our results further suggest that current mismatches between trait and climatic conditions may arise due to a divergence of factors influencing trait dynamics during low climate variability periods. These findings provide a counterpoint to the common assumption that contemporary trait-climate mismatches result from lagged responses to past climate warming. Our study also demonstrates the need for a deeper investigation of the potential influence of non-climatic factors on functional plant community dynamics.

A .Rdata file containing all the paleo community, climate informations at each site/trait/time/period used in the study. Along with the community response diagram statistics for each site/period. Please contact Pierre Gauzere if more informations are needed.

"site" : site code
"time" : time slot (500 year)
"trait_name" : functional trait (SLA, LDMC LA)
"average_trait_value" : mean community trait value based on species average                 
"sd_trait_value" : community trait standard deviation based on species average 
"average_trait_value_distrib" : mean community/time trait value based on all TRY-TTT values         
"sd_trait_value_distrib" : community/time trait standard deviation based on all TRY-TTT values
"SiteName" : site name full
"Altitude" : site altitude
"Longitude" : site Longitude (WGS84)                            
"Latitude" : site Latitude (WGS84)
"ClimTmax.ave" : average site/time maximum annual temperature within 50km buffer 
"ClimPrec.ave" : average site/time annual precipitation within 50km buffer
"ClimTmax.sd" : standard deviation site/time maximum annual temperature within 50km buffer                    
"ClimPrec.sd" : standard deviation site/time annual precipitation within 50km buffer                       
"average_trait_value_distrib_loess" : smoothed mean community/time trait value  based on all TRY-TTT values 
"average_trait_value_distrib_loess_SE" : standard error of smoothed mean community trait value based on all TRY-TTT values  
"ClimTmax.ave_loess" : smoothed average site/time maximum annual temperature within 50km buffer             
"ClimTmax.ave_loess_se" : standard error smoothed average site/time maximum annual temperature                 
"ClimPrec.ave_loess"  : smoothed average site/time maximum annual precipitation 
"ClimPrec.ave_loess_se" : standard error smoothed average site/time annual precipitation                
"t0" : time from 0 BP                                 
"period" : period based on t0 
"period2" : period based on the 14Ka separation (the one used in the study)                             
"time2" : inverse time
"crossings.mean" : mean state number (CRD statistic)
"crossings.max"  : maximum state number (CRD statistic max state number)                      
"trait.change" : absolute trait change during the timeseries (CRD statistic)                       
"env.change"   : absolute maximum temperature change during the timeseries  (CRD statistic)                        
"deviation.base" : climate deviation based on baseline value (CRD statistic)                      
"mean.absolute.deviation" : mean value of aboslute deviations (CRD statistic absolute deviation)             
"absolute.mean.deviation" : absolute value of mean deviation (CRD statistic)            
"deviation.change" : total deviation change during the timeseries (CRD statistic)
"deviation.change.1Ky" : deviation change per 1Ky (CRD statistic)                
"num.points" : number of points (lenght of the time series)
"num.points.not.na" : : number of points not NA (lenght of the time series)                    
"lm.intercept" : intercept of the TTER ~ STER linear model (CRD statistic)
"lm.slope" : slope of the TTER ~ STER linear model (CRD statistic)
"lm.se" : standard deviation of the slope of the TTER ~ STER linear model (CRD statistic)
"lm.pval" : p-value of the slope of the TTER ~ STER linear model (CRD statistic)        
"lm.r2" : r-squared of the TTER ~ STER linear model (CRD statistic)            
"lm.rho": rho of the TTER ~ STER linear model (CRD statistic response fit) 
"time.lag" : cross-correlation function fo asses time lag between TTER adn STER