Tree growth and its climate signal along latitudinal and altitudinal gradients: comparison of tree rings between Finland and the Tibetan Plateau

Abstract

Abstract. Latitudinal and altitudinal gradients can be utilized to forecast the impact of climate change on forests. To improve the understanding of how these gradients impact forest dynamics, we tested two hypotheses: (1) the change of the tree growth-climate relationship is similar along both latitudinal and altitudinal gradients, and (2) the time periods during which climate affects growth the most occur later towards higher latitudes and altitudes. To address this, we utilized tree-ring data from a latitudinal gradient in Finland and from two altitudinal gradients on the Tibetan Plateau. We analysed the latitudinal and altitudinal growth patterns in tree rings and investigated the growth-climate relationship of trees by correlating ring-width index chronologies with climate variables, calculating with flexible time windows, and using daily-resolution climate data. High latitude and altitude plots showed higher correlations between tree-ring chronologies and growing season temperature. However, the effects of winter temperature showed contrasting patterns for the gradients. The timing of the highest correlation with temperatures during the growing season at southern sites was approximately 1 month ahead of that at northern sites in the latitudinal gradient. In one out of two altitudinal gradients, the timing for the strongest negative correlation with temperature at low-altitude sites was ahead of treeline sites during the growing season, possibly due to differences in moisture limitation. Mean values and the standard deviation of treering width increased with increasing mean July temperatures on both types of gradients. Our results showed similarities of tree growth responses to increasing seasonal temperature between latitudinal and altitudinal gradients. However, differences in climate-growth relationships were also found between gradients due to differences in other factors such as moisture conditions. Changes in the timing of the most critical climate variables demonstrated the necessity for the use of daily-resolution climate data in environmental gradient studies.

Quantifying Radial Growth Response of Pinus Yunnanensis to Climate Change and Drought Event at Different Altitudes and Ages in the Jinsha River Basin

“…Summer temperature was found to be the most important factor determining the radial growth of trees present at the highest altitude (2520 m), the explanatory rate of summer temperature on radial growth was up to 26.6%. The results support the hypothesis that tree radial growth bene ts from elevated growing season temperature, and consistent with the ndings of previous studies conducted on other high mountains (Lyu et al, 2017;Panthi et al, 2018). Elevated summer temperatures may induce higher rates of cambial growth and xylem cell production (Rossi et al, 2014).…”

Radial Growth Response of Abies georgei to Climate at the Upper Timberlines in Central Hengduan Mountains, Southwestern China

“…Our results supported the traditional opinion that the summer temperature was the main factor influencing tree growth at the timberlines due to the cold environment. The positive effects of July temperature on tree growth was found by previous studies carried out in the Southern Tibetan Plateau [24,47], Mount Norikura in central Japan [48], Mount Alps in Switzerland [49], and Mount Rockies in Canada [50].…”

Assessing site signal preservation in reference chronologies for dendro-provenancing

“…On the other hand, certain signal differences may turn out to be more robust and may persist even when new data are added. For example, pronounced elevation specific growth signals have been reported by several studies [55][56][57][58][59][60]. In the simulation presented here, high-elevation and medium-to low-elevation pseudo site signals proved robust and were separated even when using single series (phs approach at t �5) or mixed signal object chronologies (poc approach at t �10 and osr-0.67).…”