High temperatures constrain latewood formation in Larix gmelinii xylem in boreal forests

Abstract

In trees, both radial growth and earlywood or latewood differentiation of xylem can reflect responses not only to internal stimuli but also to changes in the external environment. Here, we examined the effect of age and environment on the proportion of latewood to earlywood (PLE) in Larix gmelinii (Dahurian larch) from boreal forests in Eurasia to gain a better understanding of the influence of climate change on genetically controlled characteristics of tree growth. Distinctive differentiation and interannual changes in growth divergences were dependent on age, whereas the influence of environmental factors was also limited. The low-frequency change in the PLE has a juvenile effect, and the variation is unstable. The proportions of latewood to earlywood changed significantly with age during the first 100 years of life (p < 0.05), and environmental factors had a limited impact on the PLE during this stage. However, environmental effects on the PLE became statistically significant when trees were over 100 years old. The average temperature in June–August had a significantly negative correlation with the PLE with temporal changes. The PLE increased significantly with decreased annual mean temperature (p < 0.05) with geospatial variations. After 100 years of tree age, temperature played a crucial role in PLE changes. This suggests that the abnormal radial growth of Larix gmelinii, as indicated by the PLE, will occur in response to rising temperatures. Therefore, PLE-related supporting structures and intrinsic physiological processes in trees can be expected to undergo complex changes, the nature of which is uncertain, as temperatures rise globally. The variation in the PLE could lead to significant changes in the growth of the dominant tree species and hence in the structure and function of boreal forests in cold temperate zones.