RESUMO
The residual chronology of tree-ring width was constructed using Pseudotsuga forrestii collected from the low-altitude valley in the Chayu County, southeastern Tibetan Plateau of China. Pearson correlation analysis was carried out between the residual chronology of tree-ring width and climatic factors. The changes of Palmer drought severity index (PDSI) from April to May between 1812 and 2016 in the southeastern Tibetan Plateau were reconstructed by linear regression method (the variance interpretation was 47%). There was a significantly positive correlation between the PDSI index and tree-ring width index (r=0.69, P<0.01). The PDSI reconstructed sequence had four wet periods (1831-1844, 1853-1863, 1938-1948 and 1988-2002) and three dry periods (1864-1876, 1908-1926 and 2003-2016). Compared with other reconstructed sequences and historical records, our reconstructed sequence could better express dry and wet changes in the study area. The spatial analysis showed that the reconstructed sequence was consistent with the variation trend of PDSI index in southeastern Tibetan Plateau, with a strong spatial representation. Multiple tapers spectral analysis demonstrated that the PDSI reconstructed sequence had remarkable 19-20, 3.9, 3.2, 2.4 and 2.1 years quasi-periodic changes for the past 205 years, probably related to Asian summer monsoon and ENSO activities.