The figure on the left shows the average growth of Pinus sylvestris trees over time for one of my study sites in Scotland. Each line represents the average growth at a different stem height. These data will allow us to explore the impact of drought along the entire tree stem below the canopy, and allow us to investigate whether resilience assessments using measurements only taken at breast height are representative of whole tree stem response.


Of particular interest in this figure is the growth period between 1983 and 1986 which is characterised by a severe growth depression across all stem heights. The climate records for this site shows us that 1983 was a particularly dry year but 1984 was an extreme drought event. The legacy of this drought event apparently persists in the tree ring record into 1986, despite 1986 being a perfectly normal in terms of climate. This drought episode will be the focus of a large proportion of our subsequent analysis as we begin to quantify the impact of historic droughts.

The shifting bar graph animation on the left shows the evolution of the 1984 drought episode in the basal discs of Pinus sylvestris trees between 1981 and 1989. Each bars shows what percentage of trees show what percentage growth reduction (relative to their own pre-drought growth average) every year. This initial exploration of the data suggests that the response of trees in this stand is not uniform, with different trees suffering more than others in particular years. Subsequent work will tease apart what characteristics seem to make certain trees suffer more than others, whether there are trade-offs between resistance and recovery and whether the higher susceptibility of some trees is capitalised on by neighbouring trees.

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