Regional NDVI reconstruction based on tree-ring width of Pinus massoniana Lamb. in the north-south transition zone of China

Abstract

Short-term observational records of the normalized difference vegetation index (NDVI) limit the understanding of climate-driven changes in vegetation productivity and impacts in the context of global warming. The Tongbai Mountains are located in the north-south transitional zone of China and represent the northern boundary of Pinus massoniana Lamb. In this study, we employed the earlywood width (EWW), latewood width (LWW) and total ring width (TRW) chronologies of the existing P. massoniana to investigate the relationships of these chronologies with climate factors and NDVI, and found that tree growth showed significant positive correlations with temperature in March and April and with NDVI in April, May and June. The most significant positive correlations between TRW/EWW/LWW and NDVI in current June (0.79, 0.8, 0.76; p < 0.001) were used for reconstruction since 1929 or 1930. Based on the EWW chronology, one linear regression function accounted for 63.7 % of the variance during 1982–2018 and tracked the observed data well. There were 13 dense and 13 sparse vegetation coverage years (both accounting for 14.13 %), and two dense and two sparse vegetation periods after 11-year smoothing of the reconstructed series. Comparing the reconstructed series with the warm season temperatures, we found that the vegetation coverage in early summer is mainly controlled by the temperature. Spectral analysis revealed that the vegetation cover variations mainly exist 2–3a (p < 0.01) cycle, which may potentially reflect the connection between regional NDVI change and the Quasi-Biennial Oscillation (QBO). Our results are of great significance to long-term prediction and management of dynamic vegetation cover change in the north-south transitional zone of China.