Detection of alpine tree line change with high spatial resolution remotely sensed data

Abstract

This study examined vegetation distribution and tree line change in the Sangong River watershed in the Tianshan Mountains, Xinjiang, China, using aerial photographs from 1962 and 1981 and a QuickBird image from 2006. An object-oriented classification method was used to map vegetation distribution, and the postclassification comparison approach was used to detect vegetation change. The results were linked to digital elevation model data for exploring the relationships between vegetation distribution/expansion and topographic factors. It shows that Schrenkiana is mainly distributed in the region with elevations less than 2,600 m, but its tree line can reach 2,880 m. Sabina is mainly distributed in the region with elevations within 2,600 to 2,900 m, and its highest elevation can be 3,270 m. Approximately 73% of Schrenkiana areas are distributed in aspects of 0 to 45 deg and 270 to 360 deg and 52% of Sabina areas are in aspects of 45 to 90 deg and 225 to 270 deg. The Schrenkiana expansion is mainly distributed in slopes of 20 to 40 deg (accounting for 82%) and aspects of 0 to 90 deg and 270 to 315 deg (accounting for 77%). The elevation of Schrenkiana tree lines increased by 2 to 3 m from 1962 to 2006 and of Sabina increased by 7 to 12 m from 1981 to 2006. Both Schrenkiana and Sabina expansion is mainly located in vegetation frontiers.©The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.