A dendroclimatic study at Store Mosse, South Sweden : climatic and hydrologic impacts on recent Scots Pine (Pinus sylvestris) growth dynamics

Scots Pines [i]Pinus sylvestris[/i] from the Store Mosse peat bog complex, South-Central Sweden were sampled from twelve stands at the western edge of the bog, generating three transects, and three stands from the eastern edge. The aims of the project were to correlate tree-ring widths from different locations along the bog edges of Store Mosse in order to investigate to what extent climatological parameters govern the bog-tree growth, and to determine what impact the depth of the water table has on tree-growth at the different sites along the bog edges. Four different stand types were sampled; the solid ground, the marginal fen, the marginal hummock and the bog plain margin. The samples were measured under a microscope and a measuring table with the TSAPwin software. The samples were then cross-dated and the estimated year of germination was calculated for each sample. Chronologies were created for each stand type in the Cofecha and Arstan software, where the chronologies were detrended to better represent climatological changes over time. The chronologies were correlated with precipitation, temperature and river discharge data from nearby meteorological stations. The results show a relation between the estimated year of germination and distance from the marginal fen stream suggesting a lateral spread of trees during the 20th century, probably in response to drier site conditions. Peat depth, bog surface topography, nutrient availability and the water table height seem to govern the homogeneity and height of the stands. Drainage and peat mining do not seem to have had any effects on the sampled trees on Store Mosse. Events of depressed growth show a correlation with colder than normal winters, including the most wide-spread event at 1927-1929. Temperature and precipitation measurements show inconsistent correlations with the chronologies. River discharge measurements that better reflect the hydrologic status in the bog show coherent results for two to four years of added river discharge, suggesting that water table fluctuations is the governing factor controlling bog-tree growth at Store Mosse. The results indicate a response lag of two to four years between substrate moisture conditions and tree-ring width.