[Response of intra-annual stem radial growth to drought events: A case study of Pinus tabuliformis in the Helan Mountains, China].

The stem radius growth of Pinus tabuliformis was monitored by dendrometer during the growing season in 2017 and 2018 at two altitudes (2010 and 2330 m) in the Helan Mountains. We investigated the responses of tree radial growth to drought events. The results showed that drought event in June 2018 reduced stem growth rate of P. tabuliformis. The precipitation in July and August reactivated the stem radius growth. The main growing season of P. tabuliformis stem was June-August in 2018, which was a month longer than that in 2017. The response patterns between stem radial growth of P. tabuliformis and climatic factors were consistent across forest stands in different altitudes. Drought in the early growing season suppressed the radial growth of trees, while precipitation in the mid- and late growing seasons played an important role in promoting the radial growth of trees. The effects of climatic factors in August on tree-ring width should be considered during climate reconstruction in this region.