An Earlier Start of Growing Season Can Affect Tree Radial Growth Through Regulating Cumulative Growth Rate

Climate change is profoundly affecting phenology, especially in the Northern Hemisphere. Nevertheless, how tree radial growth responds to phenological shifts remains to be explored. It is necessary to analyze the specific response process of tree growth to phenology. In this study, 61 tree-ring chronologies from Central Asia were used to analyze the effects of phenological shifts on tree radial growth. Based on previous studies and hydro-thermal characteristics, we divided the study area into two parts, with 49 degrees north latitude as the boundary. The results of the model-based simulation indicated an obvious advance to the start of growing season (SoGS) in the period from 1959 to 2010/2016. Correlation analyses showed that there were significant negative correlations between the SoGS and radial growth in the north of the study area but not in the south. Path analyses indicated that radial growth between north and south did not respond consistently to the earlier SoGS. In the north, radial growth mainly benefited from the alleviation of low temperature limitations, thereby elevating the cumulative growth rate. But in the dry south, aridity stress in the early growing season counteracted the positive effect of temperature on tree radial growth through decreasing the cumulative growth rate. In general, we determined that an earlier SoGS influences tree radial growth by regulating the cumulative growth rate. This study provides a theoretical basis for promoting the accurate assessment of carbon sink potential on a larger scale and for predicting forest dynamics.