Appendix S1 Background on the use of stable carbon isotopes in wood as indicators of drought conditions.

Figure S1 Map of growing season length in Alaska derived from Moderate Resolution Imaging Spectroradiometer (MODIS) data.

Figure S2 Theoretical example of gross productivity (Prs) calculation from yearly NDVI time series.

Figure S3 Absolute difference in trends in radial growth and remotely sensed gross productivity (|τRG − τPrs|) as a function of tree‐ring sample size and area burned.

Figure S4 Time series of mean tree‐ring widths and growing season NDVI for individual stands.

Figure S5 Daily tropospheric ozone measurements at Denali National Park since 1998.

Figure S6 Correlation between mean tree‐ring width and monthly temperature.

Figure S7 Summer temperature and vapour pressure deficit from 1988 to 2008 at the Bonanza Creek Long Term Ecological Research site.

Figure S8 (a) Comparison of linear trends in Prs over the periods 1982–1991 and 1994–2008, and (b) the linear trend in Prs over the period 2000–2008.

Table S1 Overview of tree‐ring sampling sites and observed trends in Prs.

As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer‐reviewed and may be re‐organized for online delivery, but are not copy‐edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors.

Filename Description ELE_1598_sm_appendixS1.doc32 KB Supporting info item ELE_1598_sm_fS1.doc322.5 KB Supporting info item ELE_1598_sm_fS2.doc47 KB Supporting info item ELE_1598_sm_fS3.doc103.5 KB Supporting info item ELE_1598_sm_fS4.doc1.6 MB Supporting info item ELE_1598_sm_fS5.doc38.5 KB Supporting info item ELE_1598_sm_fS6.doc92.5 KB Supporting info item ELE_1598_sm_fS7.doc116 KB Supporting info item ELE_1598_sm_fS8.doc1.1 MB Supporting info item ELE_1598_sm_tS1.doc123 KB Supporting info item

Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.