Dendrochronology-Based Normalized Difference Vegetation Index Reconstruction in the Qinling Mountains, North-Central China

Larix chinensis Beissn., as a native, dominant and climate-sensitive coniferous species at Mount Taibai timberline, Qinling mountains, is rarely disturbed by anthropogenic activities; thus, it is an ideal proxy for the investigation of climate change or vegetation evolution. In this study, we applied dendrochronological methods to the L. chinensis tree-ring series from Mt. Taibai and investigated the relationships between tree-ring widths and NDVI/climate factors using Pearson correlation analysis. On the basis of the remarkable positive correlations (r = 0.726, p < 0.01, n = 23) between local July normalized difference vegetation indices (NDVI) and tree-ring width indices, the regional 146-year annual maximum vegetation density was reconstructed using a regression model. The reconstructed NDVI series tracked the observed data well, as the trans-function accounted for 52.8% of observed NDVI variance during AD 1991-2013. After applying an 11-year moving average, five dense vegetation coverage periods and six sparse vegetation coverage periods were clearly presented. At a decadal scale, this reconstruction was reasonably and negatively correlated with a nearby historical-record-based dryness/wetness index (DWI), precisely verifying that local vegetation cover was principally controlled by hydrothermal variations. Spectral analysis unveiled the existence of 2-3-year, 2-4-year, 5-7-year and 7-11-year cycles, which may potentially reflect the connection between local NDVI evolution and larger-scale circulations, such as the El Nino-Southern Oscillation (ENSO) and solar activity. This study is of great significance for providing a long-term perspective on the dynamics of vegetation cover in the Qinling mountains, and could help to guide expectations of future forest variations.

Automated summary

In this study, the authors used dendrochronological methods to investigate the relationship between tree-ring widths and climate factors in Larix chinensis at Mount Taibai. They reconstructed the 146-year annual maximum vegetation density and found that it was mainly controlled by hydrothermal variations. They also identified several cycles that may reflect the connection between local vegetation evolution and larger-scale circulations such as the El Nino-Southern Oscillation and solar activity.