Climatic drivers and tree growth in a key production species: The case of Cryptomeria japonica (Thunb. ex L.f.) D.Don in the Azores archipelago

Abstract

Forest management plays a crucial role in preserving and enhancing the delivery of ecosystem services, whereas dendrochronological methods can play a significant role in this regard. In the Azores archipelago, with a temperate oceanic climate, with low thermal amplitude, and mild and relatively wet Summers, Cryptomeria japonica (Thunb. ex L.f.) D.Don is the main timber production species. It has been extensively planted for timber production and erosion control, being the mainstay of the regional forestry chain, with a rotation period of 30 years. Although dendrochronological studies have targeted this species elsewhere, this dendrochronological study in the Azores aimed to better understand its climate-growth relationships in the archipelago. For this purpose, we sampled 140 trees, in a total of 361 wood cores samples. Following standard dendrochronological methods, we obtained four site chronologies from different volcanic complexes in São Miguel island. We used a stepwise modelling approach, with Random Forest, Principal Component Analysis and Generalized Linear Models. Our results suggest that despite year-round precipitation in the Azores, C. japonica is adversely affected by warm Winter and Summers, while on site SC it benefits from these conditions. As previously observed, precipitation may be overshadowed by temperature-driven mechanisms in C. japonica. Our spatial analysis resulted into climate-growth associations with similar directions for all site chronologies. In the future, higher Winters and Summer temperatures could lead to increased water stress and reduced growth rates. This should be considered when projecting the future distribution and productivity of C. japonica forests under different climate change scenarios. To ensure the long-term survival of this economically important tree species, adaptation responses should include genetic and conservation measures. Our findings provide baseline information for defining management approaches for this strategic species.