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

Abstract

<p><strong>Abstract.</strong> Latitudinal and altitudinal gradients can be utilized to forecast the impacts of climate changes on forests. To improve the understanding of forest dynamics on these gradients, we tested two hypotheses: (1) the change in 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. We used tree-ring data from a latitudinal gradient in Finland and two altitudinal gradients on the Tibetan Plateau. We analysed the latitudinal and altitudinal growth patterns in tree-rings and investigated the growth-climate relationships of trees by correlating ring-width index chronologies with climate variables calculated with flexible time-windows, using daily-resolution climate data. The high latitude and altitude plots showed higher correlations between the tree-ring chronologies and growing season temperature. However, the effects of winter temperature showed differing patterns for the gradients. The timing of highest correlation with summer temperatures in southern sites was approximately one month ahead of the northern sites in the latitudinal gradient. In one out of the two altitudinal gradients the timing of strongest negative correlation with summer temperatures at low altitude sites was ahead of the treeline sites, possibly due to differences in moisture limitation. Mean values and the standard deviation of tree-ring width was found to increase with increasing mean summer temperatures on both types of gradients. Our results showed similarities of tree growth responses to growing season temperature between latitudinal and altitudinal gradients. However, differences in climate-growth relationships were also found between the gradients, due to differences in other factors, such as moisture conditions. Changes in the timing of the most critical climate variables demonstrated the need to use daily resolution climate data in studies on environmental gradients.</p>

Radial Growth Response of <em>Abies georgei</em> 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 (Liang et al, 2009;Lyu et al, 2017), Mount Norikura in central Japan (Takahashi et al, 2005), Mount Alps in Switzerland (Meyer and Braker, 2001), and Mount Rockies in Canada (Luckman et al, 2005).…”

Assessment of Plant Communities and Identification of Indicator Species of an Ecotonal Forest Zone at Durand Line, District Kurram, Pakistan

“…Therefore, understanding plant and environmental variables correlations, highlighting leading threats and conservation managements are the fascinating research field for ecologists and environmentalists (Tavili and Jafari, 2009; Khan et al, 2016). Vegetation structure and composition are persuaded by numerous natural and anthropogenic activities (Shaheen et al, 2012;Lyu et al, 2017). Thus, ecosystem services quantification and evaluating vegetation distribution and mapping are important for conservation (Biondi, 2011).…”

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 – 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).…”