Canadian Forest Service Publications

A novel stochastic method for reconstructing daily precipitation times-series using tree-ring data from the western Canadian Boreal Forest. 2017. Chun, K.P.; Mamet, S.D.; Mestsaranta, J.; Barr, A.; Johnstone, J.; Wheater, H. Dendrochronologia 44(2017):9-18.

Year: 2017

Available from: Northern Forestry Centre

Catalog ID: 38891

Language: English

CFS Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1016/j.dendro.2017.01.003

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Abstract

Tree ring data provide proxy records of historical hydroclimatic conditions that are widely used for reconstructing precipitation time series. Most previous applications are limited to annual time scales, though information about daily precipitation would enable a range of additional analyses of environmental processes to be investigated and modelled. We used statistical downscaling to simulate stochastic daily precipitation ensembles using dendrochronological data from the western Canadian boreal forest. The simulated precipitation series were generally consistent with observed precipitation data, though reconstructions were poorly constrained during short periods of forest pest outbreaks. The proposed multiple temporal scale precipitation reconstruction can generate annual daily maxima and persistent monthly wet and dry episodes, so that the observed and simulated ensembles have similar precipitation characteristics (i.e. magnitude, peak, and duration)—an improvement on previous modelling studies. We discuss how ecological disturbances may limit reconstructions by inducing non-linear responses in tree growth,and conclude with suggestions of possible applications and further development of downscaling methods for dendrochronological data.

Plain Language Summary

Computer models that simulate how forests might grow many years or decades into the future need to know how much it might rain every day in order to make better predictions. But most of the time our rain forecasts only go a couple of weeks into the future, and climate forecasts far into the future usually provide only the total amount of rain in an entire year. To solve this problem, this study compared daily rainfall records with annual growth rings in trees, which are often related: more rain means better growth and wider rings. At three places in Saskatchewan, scientists have put sophisticated instruments on tall towers above the forest to measure many factors that might affect the forest, including daily rainfall. Cores were collected from trees growing under these towers, and the annual growth rings were measured. These two pieces of information were used together to estimate the future probability of rainfall. Occasionally, things having nothing to do with the amount of rain, like all the leaves or needles being eaten by insects, cause trees to have narrow rings. While it would be useful to have these probability estimates for different types of forests in different parts of Canada, they will have to be used carefully to make predictions about daily rainfall, especially when outbreaks of insects are happening at the same time.

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