May-July mean minimum temperature variability in the mid-Qinling Mountains, central China, since 1814 CE

A tree-ring width (TRW) chronology was developed from Larix chinensis Beissn at the divide sampling site in the mid-Qinling Mountains, central China. The relationships between tree radial growth and climate factors on several timescales (Daily, Pentad, Dekad and Month) were studied. Compared to precipitation, temperature shown stronger impacts on Larix chinensis Beissn on each timescales. Particularly, pentad was a more suitable scale for tree growth-climate response analysis. Significantly positive correlation was found between tree-ring index and the mean minimum temperature from May to July, i.e. 28 to 42 pentads (r = 0.625, p < 0.001). Based on this relationship, the May to July mean minimum temperature was reconstructed in the last 194 years, with an explained variance of 39.1% for the calibration period from 1957 to 2007. The results of leave-one-out tests showed that the reconstruction mode was stable and reliable. This minimum temperature reconstruction revealed that cold spans mainly occurred in 1816-1831, 1840-1852, 1879-1888 and 1976-1984, while warm spans prevailed in 1863-1878, 1889-1897, 1916-1932 and 2000-2007. Comparisons with other surrounding temperature series from tree rings, our reconstruction could provide a good regional representation of temperature change in the mid-Qinling Mountains. The reconstructed minimum temperature series was further verified by dryness-wetness index (DWI) sequence based on Chinese historical literature. Significant quasi-periodic signals at 32.2a, 20.5a, 8.9-13.1a and 2-8a suggested that temperature variability in the study area may associate with the El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO).