Elevation-dependent growth trends of forests as affected by climate warming in the southeastern Tibetan Plateau

Abstract

Stress from water scarcity as a result of rising temperatures associated with climate change has a profound impact on forest ecosystems around the world. However, few studies have assessed the influence of climate change on the dynamics of growth of alpine coniferous forests of different tree species and at different elevations on a regional scale in southeastern Tibetan Plateau (TP). The present paper examines that the impact using dendrochronological techniques with trees of the following genera: Abies, Picea, Larix, Tsuga, Pinus, Cupressus, and Juniperus. Radial growth was measured based on 46 chronologies from the cores of 2027 trees on the Hengduan Mountains (one of the Global Biodiversity Hotpots), which are part of the TP. In most cases, ring widths were strongly and significantly correlated to temperature both before and during the growing season, suggesting that climate warming plays a prominent role in the growth of alpine conifers in recent decades. Greater sensitivity to temperature and the rising temperatures have together led to faster growth of forest trees at high elevations than at low elevations. Climate warming may benefit most coniferous species by boosting their radial growth, especially in the upper treeline ecotone, but may also decrease radial growth significantly in P. yunnanensis at lower elevations because the species, unlike the other species studied, is adversely affected by high temperatures. If elevation-dependent warming in the Hengduan Mountains continues in the future, conifers at high and middle elevations (3000 m or higher) will benefit, whereas those at lower elevations (below 3000 m) will be affected adversely because of the warming-induced water deficit.