Linkages between intra-annual radial growth and photosynthetic production of four main species in a temperate forest in northeast China

The comprehension of the linkage between radial stem growth and photosynthesis is fundamental to gaining insight into the growth and developmental mechanisms of trees, as well as their adaptive capacity to future climate change. However, such crucial information is rarely available, particularly on short-term temporal scales. In this study, we continuously monitored the intra-annual radial stem growth of a non-porous species (Pinus koraiensis) and three ring-porous species (Quercus mongolica, Fraxinus mandshurica, Ulmus japonica) with monthly measurements in 2019 and weekly measurements from 2020 to 2022(second part in 2022) in a temperate forest of Northeast China based on microcore techniques. Concurrently, we estimated the daily photosynthetic production at the individual tree level using a photosynthetic production model developed by our research team. Subsequently, a generalized linear model was conducted to determine the temporal lag of intra-annual radial stem increment and photosynthetic production. Our results indicate significant differences in the initiation of radial growth among the observed years, while the cessation of growth remained consistent. Specifically, ring-porous species exhibited an earlier onset of radial growth compared to non-porous species, but no consistent pattern was observed for the cessation of growth across different wood types. Additionally, we found a strong coupling between radial growth increment and photosynthetic production without any day lag, particularly in different classes. Furthermore, a notable linear association was observed between relative intra-annual radial growth and photosynthetic production, further indicating a positive correlation between photosynthesis and radial growth. We concluded that the carbohydrates required for radial growth are at least partially derived from photosynthetic production produced on the same day when the leaves were available for photosynthesis. These findings enhance our understanding of the seasonal dynamics of radial growth at the cellular level and provide new insights into the relationship between radial growth and photosynthetic production on short-term temporal scales.