[May-July NDVI variation for the middle Qinling Mountains over the past 194 years indicated by tree rings of ].

Due to the short-term observation record of the normalized difference vegetation index (NDVI), the research on long-term NDVI changes is scarce, which limits our understanding of the impacts of NDVI changes in the context of global warming. In this study, a regional tree-ring chronology was developed based on the tree-ring samples of in the middle Qinling Mountains. The results showed that tree-ring width of was significantly positively correlated with May-July NDVI (=0.624, <0.01, =34). The Sig-Free tree-ring width chronology was used to reconstruct May-July NDVI during the period 1825-2018, which explained 38.9% of the total NDVI variance. Results of spatial analysis showed that the reconstructed series could better represent the NDVI changes in the study area. There were six high NDVI periods and five low NDVI periods in the past 194 years. The vegetation grew best in 2006-2018, indicating vegetation cove-rage in the middle of Qinling Mountains had been improved during the warming hiatus. Low NDVI periods in the reconstruction series were consistent with drought over much of study area. Results of wavelet analysis indicated the existence of 2-4 years and 12-16 years cycles in the reconstruction series. SEA analysis showed that the reconstruction series decreased significantly in the El Nino year, while increased significantly in the first to third years after the La Nina event. The growth of was predicted to increase slightly under the SSP2-4.5, SSP3-7.0 and SSP5-8.5 scenarios.