Regional Scale Temperature Rather than Precipitation Determines Vessel Features in Earlywood of Manchurian Ash in Temperate Forests

Abstract

AbstractThe earlywood vessels (EWVs) of ring‐porous species are formed in the outermost tree ring to guarantee efficient water transport before bud break. At present, it is unclear which climatic factors influence the formation of EWV traits of trees in temperate forests, which limits the accuracy of predicting forest response to climate change. We investigated the EWV traits of Manchurian ash (Fraxinus mandshurica Rupr.) in a network of 19 sites in northeast China. Ring width (RW) was significantly negatively correlated with vessel density (VD) and positively correlated with other EWV traits, including mean vessel area (MVA), hydraulic diameter (Dh), vessel number (VN), and total vessel area (TVA). The climate signals recorded by RW and EWV traits were consistent in almost all sites. Temperature was the most important climate factor limiting xylem formation that influences RW and EWV of Manchurian ash. The minimum temperature, especially in the previous growing season, was positively correlated with RW and EWV traits but negatively correlated with VD at almost all sites. In the drier northern sites, temperature and moisture in nongrowing season also had a positive effect on RW and EWV traits. The rapid warming around 1980 significantly promotes hydraulic efficiency (Dh, VN, MVA, and TVA) and carbon assimilation (RW), which provided a potential physiological mechanisms of climate warming leading to growth increase of ring‐porous broadleaf species. It is worth noting that continuous climate warming has brought great benefits to tree growth, but it also increases the risk of hydraulic failure, especially in the south.