Fennoscandia 300 Year Inferred Maximum Stomatal Conductance Data Gagen, M.; Finsinger, W.; Wagner-Cremer, F.; McCarroll, D.; Loader, N.J.; Robertson, I.; Jalkanen, R.; Young, G.H.F.; Kirchhefer, A.J. Gagen, M. Finsinger, W. Wagner-Cremer, F. McCarroll, D. Loader, N.J. Robertson, I. Jalkanen, R. Young, G.H.F. Kirchhefer, A.J. carbon cycle earth science/paleoclimate/paleolimnology (Kiruna Mire>LATITUDE 67.85>LONGITUDE 20.2167) Investigating the many internal feedbacks within the climate system is a vital component of the effort to quantify the full effects of future anthropogenic climate change. The stomatal apertures of plants tend to close and decrease in number under elevated CO2 concentrations, increasing water-use efficiency (WUE) and reducing canopy evapotranspiration. Experimental and modelling studies reveal huge variations in these changes such that the warming associated with reduced evapotranspiration (known as physiological forcing) is neither well understood or constrained. Palaeo-observations of changes in stomatal response and plant WUE under rising CO2 might be used to better understand the processes underlying the physiological forcing feedback and to link measured changes in plant WUE to a specific physiological change in stomata. Here we use time series of tree ring (Pinus sylvestris L.) d13C and subfossil leaf (Betula nana L.) measurements of stomatal density and geometry to derive records of changes in intrinsic water-use efficiency (iWUE) and maximum stomatal conductance in the Boreal zone of northern Finland and Sweden. We investigate the rate of change in both proxies, over the recent past. The independent lines of evidence from these two different Boreal species indicate increased iWUE and reduced maximum stomatal conductance of similar magnitude from preindustrial times (ca. AD 1850) to around AD 1970. After this maximum stomatal conductance continues to decrease to AD 2000 in B. nana but iWUE in P. sylvestris reaches a plateau. We suggest that northern boreal P. sylvestris might have reached a threshold in its ability to increase WUE as CO2 rises. STUDY NOTES: Reconstruction of maximum stomatal conductance to water vapor (gwmax) over the past ~300 years, based on measurements of stomatal density and pore length. Data are presented as (i) yearly averages from multiple leaf fragments extracted from two peat sections in the Kiruna mire (northern Fennoscandia (Kiruna and Kir 8)) and from herbarium collections, and (ii) smoothed estimates of gwmax. In addition, smoothed estimates of stomatal size are also given. Datasets were smoothed with a robust loess function (locally weighted regression) (Cleveland & Devlin, 1988) with a constant window width and fixed target points in time. The smoothed curve was constructed by determining fitted values at 10-year intervals with a 100-year window width (here referred to the full span of the window). In this method the smoothing window does not change as a function of data density around the fitted values, it rather uses all datapoints within the 100-year window width NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Gagen, M. Investigator : Finsinger, W. Investigator : Wagner-Cremer, F. Investigator : McCarroll, D. Investigator : Loader, N.J. Investigator : Robertson, I. Investigator : Jalkanen, R. Investigator : Young, G.H.F. Investigator : Kirchhefer, A.J. 2012-10-24 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/13478 https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/europe/fennoscandia2011gwmax.txt https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/europe/fennoscandia2011stomata.txt https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/europe/fennoscandia2011gwmax.txt https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/europe/fennoscandia2011stomata.txt English https://www.ncdc.noaa.gov/paleo/study/13478 https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/europe/fennoscandia2011gwmax.txt https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/europe/fennoscandia2011stomata.txt Gagen, M., W. Finsinger, F. Wagner-Cremer, D. McCarroll, N. Loader, I. Robertson, R. Jalkanen, G. Young, and A. Kirchhefer. 2011. Evidence of changing intrinsic water-use efficiency under rising atmospheric CO2 concentrations in Boreal Fennoscandia from subfossil leaves and tree ring d13C ratios. Global Change Biology, Vol. 17, Issue 2, pp. 1064-1072. DOI: 10.1111/j.1365-2486.2010.02273.x START YEAR: 1718 AD * END YEAR: 2008 AD 20.2167 67.85 20.2167 67.85