The 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.

No abstract

No abstract

Abstract. The unstable sensitivity of growth-climate relationships greatly restricts tree-ring-based paleoclimate reconstructions, especially in areas with frequent divergence problems, such as the temperate zone in northeast China. Here, we propose an original tree-species mixing method to overcome this obstacle and improve the stability and reliability of reconstruction models. We take the tree-ring based growing-season minimum temperature reconstruction for the northern Changbai Mountains in northeast China as an example to illustrate the method. Compared with previous temperature reconstruction models, our reconstruction model is more stable and reliable and explains up to 68 % of the variance. It is also highly consistent with historical records and tree-ring-based temperature reconstructions from the nearby Xiaoxing'an Mountains and from across the Northern Hemisphere. Our reconstruction uses two different tree species and is more accurate than temperature reconstructions developed from a single species. Over the past 259 years (AD 1757–2015), five significant cold periods and five warm periods were identified. The reconstruction indicates rapid warming since the 1980s, which is consistent with other instrumental and reconstructed records. We also found the Atlantic Multidecadal Oscillation plays a crucial role in driving the growing-season minimum temperature in the northern Changbai Mountains.

No abstract