It is important to understand the response of stem diameter variations in dominant tree species to water conditions in Northeast China. The results will provide basic information for scientific predictions of the future development trend of temperate forests in the eastern mountainous area of northeast China. We employed a high-precision dendrometer to continuously monitor the stem radial changes of six dominant tree species in temperate forests in northeast China from 15 April to 24 October in 2021. Precipitation significantly promoted the tree stem diameter increment. The increment of stem diameter in Juglans mandshurica Maxim., Quercus mongolica Fisch. and Betula platyphylla Suk. had a significantly positive correlation with cumulative precipitation. Correlation analysis revealed that the stem radial change (SRC) of six tree species was positively correlated with precipitation (Pre) and relative humidity (RH), and negatively correlated with water vapor pressure deficit (VPD), indicating that the diameter growth of the six tree species was mainly restricted by water conditions. Under drought stress, the stem radial growth rate of the six tree species slowed down, the growth duration decreased and the tree water deficit (TWD) value increased, while there were obvious interspecific differences. Therefore, water conditions limited the stem radial growth of the six tree species, while each tree species had a different response to drought stress.

Nonstructural carbohydrates (NSCs) are key storage molecules that can be used for tree growth and metabolism. The trade-off between NSC storage and biomass production has been long reported on. However, the carbon source limitation (indicated by NSC storage) to biomass production remains poorly quantitively assessed. The seasonal whole-tree NSC pool dynamics of 12 temperate tree species were quantitatively evaluated across seven seasonal sampling points. The ratio of seasonal variation in whole-tree NSC pool to annual biomass increment (the ΔNSC/ABI ratio) and the linear relationship of annual biomass increment to NSC storage were used to assess the coupling of NSC storage to annual biomass production. Whole-tree NSC pools were consumed in early summer when structural growth peaked and recovered in the nongrowing season, indicating a short-term trade-off between storage and growth. The ΔNSC/ABI ratio was on average 0.59, with a large interspecific variation. Notably, there was a significant positive correlation between the storage of NSC and the 10 yr mean annual biomass increment, indicating a storage–growth coupling and the source limitation of growth in the long term. However, the storage cost of biomass production decreased along the slow-growth-to-fast-growth species continuum, mirroring the spectrum from conservative to acquisitive NSC use strategies. These findings highlight the critical role of time scale in understanding the relationship between storage and growth, which should be considered in the framework of simulation and conceptual models.

The phenomenon of divergent responses in tree ring radial growth to climate change has been observed in the mid- and high-latitude regions of the Northern Hemisphere amidst global warming. However, the stability of the responses of the primary conifer species to climate factors in the mountainous regions of northeastern China remains unclear. Additionally, it is uncertain whether the radial growth in this area consistently responds to different competition indices. In our study, we developed tree ring width chronologies for Dahurian larch (Larix gmelinii) and analysed the radial growth responses to the regional climate from 1980 to 2012. This analysis was conducted by correlating meteorological data from different physiological stages of trees. We also evaluated the reliability of competition indices in predicting tree growth by constructing multiple linear regression models. Furthermore, we explored the relationship between the Basal Area Increment (BAI) of each tree and the competition indices in the sample plot over the previous five years. Our results showed that the temperature during the Non-Structural Carbohydrate (NSC) accumulation period and the NSC consumption period was significantly negatively correlated with the Ring Width Index (RWI) of Dahurian larch. Conversely, the RWI was significantly positively correlated with precipitation during these periods. The Standardised Precipitation Evapotranspiration Index (SPEI) at any period had a significantly positive correlation with the RWI. These findings suggest that future radial growth is likely to continue to be constrained by rising temperatures and water scarcity. Our findings also demonstrated that radial growth was less negatively impacted by competition from nearby trees and more influenced by the initial size of the tree. Compared to models that included other indices, models that included the BAL index as a single explanatory variable demonstrated superior statistical effectiveness. Our research suggests that before evaluating the competitive effects of the neighbourhood on radial growth, it is necessary to consider the stand diversity of tree species and the parameters related to spatial structure when selecting an appropriate competition index.