Impact of climate and drought events on the Growth of Scots pine (Pinus sylvestris L.) provenances

We explored the growth response of Scots pine to temperature, precipitation, and drought focusing on eleven provenances from the IUFRO 1982 international provenance trial. At two macroclimatically different sites in Germany we measured chronologies of tree-ring widths and annual height increment. We estimated general climate/growth relationships and examined the growth response, based on tolerance indices of resistance, recovery, resilience and relative resilience, to the most severe drought event per site. Using multivariate benchmarking of provenance archetypes, we established a ranking of the individual provenances in terms of general performance. In addition to considerable differences in overall growth between provenances, growth metrics differed between sites which were mostly attributable to climate. Basal area increment depended mainly on water availability from May to July, whereas annual height growth was influenced by moisture deficit during May of the current year. The reaction to drought events was shown to depend on the timing and duration of the drought event. Differences between provenances in resistance were modest, but more pronounced for recovery and especially for resilience and relative resilience. The results indicate a better adaptation to drought of the provenance from Bosnia Herzegovina and of local German provenances compared to other provenances. We summarized the findings by aligning the eleven provenances between two multivariately defined archetypes, one of which represented best general performance defined by good overall growth, low climate sensitivity and high resilience to drought. This approach confirmed the superior performance of the local German populations. Provenances from France and Poland were ranked above average whereas northern provenances and that from Bosnia Herzegovina were found to be least suitable at the sites under investigation. Our results clearly demonstrate the importance of considering provenance in the discussion about future adaptedness and adaptability of tree species under climate change scenarios.