Little change in the fir tree-line position on the southeastern Tibetan Plateau after 200years of warming

Abstract

As one of the world's highest natural tree lines, the Smith fir (Abies georgei var. smithii) tree line on the southeastern Tibetan Plateau is expected to vary as a function of climate warming. However, the spatial patterns and dynamics of the Smith fir tree line are not yet well understood. Three rectangular plots (30m×150m) were established in the natural alpine tree-line ecotone on two north-facing (Plot N1, 4390m asl; Plot N2, 4380m asl) and one east-facing (Plot E1, 4360m asl) slope. Dendroecological methods were used to monitor the tree-line patterns and dynamics over a 50-yr interval. The three study plots showed a similar pattern of regeneration dynamics, characterized by increased recruitment after the 1950s and an abrupt increase in the 1970s. Smith fir recruitment was significantly positively correlated with both summer and winter temperatures. However, Smith fir tree lines do not show a significant upward movement, despite warming on the Tibetan Plateau. The warming in the past 200yr is already having a significant impact on the population density of the trees, but not on the position of the Smith fir tree line. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.