Tree-ring based PDSI reconstruction since 1853 AD in the source of the Fenhe river basin, Shanxi province, China

A robust tree-ring-width chronology was developed from two Pinus tabulaeformis sampling sites in the source of the Fenhe River, Shanxi Province, China. Based on the tree-ring-width indices, a 157-year long Palmer Drought Severity Index (PDSI) was reconstructed, which explains 53.7% of the variance of the modeled PDSI over the common period 1957-2008. The drought periods in the study area include 1914-1931 and 1970 to the present, whereas the wet periods were 1866-1892 and 1932-1969. The drought of 1914-1931 was a severe long-lasting drought with a low inter-annual variability, and the drought of 1970-2009 was an overall long-term drought with a high inter-annual variability. The period of 1866-1892 is a continuously wet period with a low inter-annual variability and the period of 1932-1969 is an overall long-term wet period with a high inter-annual variability. The reconstructed PDSI series in the source of the Fenhe River shows synchronous variations with the regional drought/wetness indices. Spatial correlation analyses indicate that the higher correlations lie exclusively in the Fenhe River Basin. This indicates that the reconstructed PDSI has regional representativeness and can represent the drought history of the entire Fenhe River Basin to some extent. Furthermore, the reconstructed PDSI matches with the variability of the per unit yield of summer grain crops in Shanxi Province very well and they have significant correlation. From a long-term perspective the reconstructed PDSI series could supply scientific and valuable information to the water resources management and then help the sustainable development in agricultural production, economic development, and ecosystem balance.</p

Tree-ring based runoff reconstruction of the upper Fenhe River basin, NorthChina, since 1799 AD

To acquire long-term perspectives on the history of droughts, we have presented the first runoff reconstruction from March to July in the upper Fenhe River basin, based on Pinus tabulaeformis tree-ring width indices from the Guancen Mountains, headstream of the Fenhe River, North China. The reconstruction explains 54.8% of the instrumental runoff variance over the period from 1952 to 2008. An analysis of interannual runoff variability indicated that AD 2001 was not only the driest year for the instrumental period, but also the driest year since AD 1799 in the upper Fenhe River. More extreme single-year droughts existed in the 20th century than in the 19th century in the region. Multiyear and decadal scale dry regime analyses demonstrated that the instrumental runoff underestimated the potential severe and prolonged droughts in the Fenhe River basin in future, such as droughts similar to the multiyear pre-instrumental droughts from 1831 to 1842 and 1919 to 1929. Comparisons between the Fenhe River runoff reconstruction and other nearby precipitation reconstructions showed that drought occurrence has been synchronous in parts of north and northwestern China to some extent for the last 211 years. Spatial correlation analyses between runoff data and the gridded Palmer Drought Severity Index dataset indicated that the average runoff reconstruction from March to July in the upper Fenhe River represents the regional moisture variations in North China, especially in the entire Fenhe River basin. As for the highest frequency and severity of spring drought in Shanxi province, the runoff reconstruction can provide base data for historical drought analysis and water resource planning and management in the Fenhe River basin or even to entire Shanxi province.</p

Annual precipitation variability inferred from tree-ring width chronologies in the Changling-Shoulu region, China, during AD 1853-2007

On the basis of a significant correlation between the tree-ring width series from Changling-Shoulu (CLSL) in north-central China and observed instrumental data, the annual total precipitation of the previous July to the current June was reconstructed since 1853 for the studied region, with the predictor variables accounting for 41.2% of the variance in the precipitation data. Distinct wet periods with precipitation levels greater than the mean (315 mm) occurred in 1864-1876 and 1934-1960. Notable dry periods with precipitation less than the mean occurred in 1877-1888 and 1923-1933. The precipitation fluctuated dramatically during 1940-1970, and became relatively stable around the mean value from 1960. The CLSL precipitation series showed significant correlations with precipitation reconstructions from Mt. Xinglong, Mt. Helan, Ningwu and eastern China, suggesting that these five rainfall curves represent the general precipitation variations in the western-central environmentally sensitive zone of northern China. The calculations of the CRU grid points also indicate the existence of significant spatial correlation among these sites. Periodicity analysis showed clear 23.33-, 8.24-, 2.64- and 2.59-year cycles at a 99% confidence level for the reconstructed series during the past 155 years.</p

Tree-ring-based precipitation reconstruction for Mt. Xinglong, China, since AD 1679

On the basis of a significant correlation between the ring width of Qinghai spruce (Picea crassifolia Kom.) trees at Mt. Xinglong in north-central China and observed instrumental data, a transfer function was designed and the annual precipitation (from the previous July to the current June) was reconstructed for a period spanning 1679-2008 AD with an explained variance of 53.1% (1955-2008 AD). Intervals with precipitation more than the 330-year average occurred in 1686-1715, 1727-1741, 1774-1810 and 1871-1923. The intervals 1716-1726, 1740-1773, 1811-1870, 1924-1937 and 1980-2003 had precipitation lower than the 330-year average. Most drought events recorded in historical documents were captured by the reconstruction. Moreover, the reconstruction agreed well with tree-ring-based precipitation at Mt. Helan 400 km northeast of Mt. Xinglong. The results showed that the variability of the East Asian summer monsoon-related precipitation was synchronously at a large spatial and temporal scale within the environmentally sensitive region in northern China. The reconstruction was tested for periodicities by power spectrum analysis. The results showed remarkable 160-, 106.67-, 80-, 22.86-, 6.27- and 2- to 3-year cycles at a 99% confidence level for the past 330 years.</p

A wetness index derived from tree-rings in the Mt. Yishan area of China since 1755 AD and its agricultural implications

Dendroclimatological techniques were employed to investigate the relationship between Chinese Pinus (Pinus tabulaeformis Carr.) growth and climatic variability in the Mt. Yishan region of Shandong Province, China, over the past 253 years. Using regression analysis, the wetness index (WI) was reconstructed for the Mt. Yishan area for the period 1755-2007 AD based on tree-ring widths; predictor variables accounted for 40 % of the variance. The reconstructed time-series displayed an increasing trend after the late 1960s. Both the estimated and the observed WI for May-August were better correlated with precipitation than temperature during the period 1958-2007 AD, indicating that the contribution of precipitation to the WI was larger than temperature in the study area. The reconstructed WI was compared with the dryness/wetness index of China and land areas that were affected by droughts and floods using the agricultural statistics for Shandong Province. In addition, the WI time-series corresponded well with the peanut yield in Shandong Province at high frequency, which may be reasonable in the context of agriculture in Shandong. The 3-, 5- to 6- and 9- to 10-year periodicities detected in the time-series suggested that the reconstructed WI in the Mt. Yishan area may be related to large-scale climate variations.</p