Fig 1.
Map of the sampling site.
Fig 2.
Tree-ring STD chronology, running EPS, running Rbar and sample size.
Fig 3.
Monthly mean temperature and total precipitation values at Jingtai (1957–2013) and Jingyuan (1951–2013) meteorological stations.
Fig 4.
Correlations between the tree-ring STD chronology and monthly mean temperature, and monthly total precipitation (1957–2012 AD).
Horizontal dashed lines represent the 95% C.L.
Fig 5.
Correlations between the STD chronology and monthly SPEI data at time scales from 1 to 24 months (AD 1951–2011).
Circles represent significant at the 95% C.L.
Table 1.
Statistics for calibration and verification test results.
Fig 6.
Comparison between observed and reconstructed SPEIAJ.
(a) The reconstructed (black line) and observed (gray line) SPEIAJ during 1951–2011. (b)The reconstructed SPEIAJ after an 11-year moving average for the Taihe Mountains from 1730 to 2012.
Fig 7.
Comparison between the SPEIAJ reconstruction and dryness/wetness indices of Lanzhou.
Fig 8.
Tree-ring-based reconstruction comparisons among three sites.
(a) The reconstructed precipitation in Liancheng. (b) The SPEIAJ reconstruction in the Taihe Mountains. (c) The reconstructed precipitation in the Changling-Shoulu region.
Fig 9.
Patterns of field correlation in our study.
(a) Correlations between the gridded (37.25°N, 104.75°E) SPEIAJ series with the 0.5×0.5 gridded mean April-June SPEI at the 10-month scale. (b) Correlations between reconstructed SPEIAJ with the 0.5×0.5 gridded mean April-June SPEI at the 10-month scale (1951–2011 AD).
Fig 10.
MTM spectral density of the reconstruction.
The 50% line indicates the null hypothesis, and the 95% and 99% lines indicate the relevant confident levels. Some periodicities passing 95% are labeled in the plot