Inconsistent relationships between tree ring width and normalized difference vegetation index in montane evergreen coniferous forests in arid regions

KEY MESSAGE: There was an inconsistent positive correlation between tree ring width and NDVI in the Tianshan Mountains, and this correlation gradually weakened from west to east and decreased with increasing elevation. Tree ring width and the normalized difference vegetation index (NDVI) are two effective indicators used to monitor changes in forest dynamics. Most studies focus on the relationship between tree ring width and regional NDVI in the mountainous areas of arid regions, failing to reflect the relationship between forest radial growth and forest canopy activities. In this paper, four study areas were selected ranging from west to east on the northern slope of the Tianshan Mountains in China. Tree cores of Picea schrenkiana were collected at three elevations in each study area, and NDVI values were extracted for the forest cover at each location. Emphasis was placed on the relationship between the tree ring width and NDVI values of montane evergreen coniferous forests in an arid region in the period 2000–2012. There was an inconsistent positive correlation between tree ring width and NDVI in the Tianshan Mountains, and the relationship became increasingly weak from west to east and decreased with increasing elevation. The varied forest growth and its response to climatic factors as a result of the different environmental conditions present in arid mountain regions may be the underlying reason for the inconsistency between the tree ring width and NDVI of forests. Drought stress may be the major driving factor of the positive correlation between the tree ring width and NDVI of montane evergreen coniferous forests in arid regions. This result may be useful for integrating tree ring width and NDVI to study the ecology of montane evergreen coniferous forests in arid regions.