Growth dynamics of tree-line and lake-shore Scots pine (Pinus sylvestris L.) in the central Scandinavian Mountains during the Medieval Climate Anomaly and the early Little Ice Age

Abstract

Trees growing at their altitudinal or latitudinal distribution in Fennoscandia have been widely used to reconstruct warm season temperatures, and the region hosts some of the world's longest tree-ring chronologies. These multi-millennial long chronologies have mainly been built from tree remains found in lakes (subfossil wood from lake-shore trees). We used a unique dataset of Scots pine tree-ring data collected from wood remains found on a mountain slope in the central Scandinavian Mountains, yielding a chronology spanning over much of the last 1200 years. This data was compared with a local subfossil wood chronology with the aim to (1) describe growth variability in two environments during the Medieval Climate Anomaly (MCA) and the early Little Ice Age (LIA), and (2) investigate differences in growth characteristics during these contrasting periods. It was shown that the local tree-line during both the MCA and early LIA was almost 150 m higher that at present. Based on living pines from the two environments, tree-line pine growth was strongly associated with mid-summer temperatures, while the lake-shore trees showed an additional response to summer precipitation. During the MCA, regarded to be a period of favorable climate in the region, the tree-ring data from both environments showed strong coherency and moderate growth variability. In the early LIA, the two chronologies were less coherent, with the tree-line chronology showing more variability, suggesting different growth responses in the two environments during this period of less favorable growing conditions. Our results indicate that tree-ring width chronologies mainly based on lake-shore trees may need to be re-evaluated.

Warming‐induced upward migration of the alpine treeline in the Changbai Mountains, northeast China

“…The relationship between summer mean temperature (SMT) and STD had the strongest correlations; that is, SMT largely corresponded to the annual growth of B. ermanii . This finding consists with the prevailing view that high altitude and latitude treelines are controlled by summer temperatures (Gehrig‐Fasel, Guisan, & Zimmermann, ; Kirdyanov et al., ; Linderholm et al., ; MacDonald, Kremenetski, & Beilman, ; Seim et al., ). We therefore used the STD chronology series to reconstruct the SMT of our transects for the last 160 years (Appendix S4).…”

Ranking of tree-ring based temperature reconstructions of the past millennium

“…The successful combination of living trees with historical/remnant/sub-fossil material improves when the provenance of all samples is ecologically consistent. If not, older sections of a millennial-length chronology can have different growth rates and climate signals than those sections dominated by samples from living trees (Boswijk et al, 2014;Linderholm et al, 2014;Tegel et al, 2010). For example, remnant samples from a sub-alpine site in the Alps are ideally combined with samples from living trees growing on the same slope, at the same elevation and aspect (Neuwirth et al, 2004); sub-fossil trees from a shallow lake in Fennoscandia are ideally combined with trees growing around the lake, as opposed to drier inland locations (Düthorn et al, 2013(Düthorn et al, , 2015.…”

Can tree-ring density data reflect summer temperature extremes and associated circulation patterns over Fennoscandia?

“…1 The map of the study area and the locations of 34 tree-ring MXD chronologies covering the period of . Blue colors mark the locations of three millennium-long chronologies https://www.ncdc.noaa.gov/data-access/paleoclimatologydata/datasets/tree-ring; Grissino-Mayer and Fritts 1997), while some of the data from central Sweden were collected between 2011 and 2013 by ourselves (Linderholm et al 2014. More information about the tree-ring data used in this study can be found in Table S1 in the supplementary section.…”