Abstract: Background, aim, and scope The Loess Plateau is one of the areas of the world with the severe soil erosion and the extremely vulnerable ecological environment. Its forest area has decreased dramatically, and only natural secondary forest can be found on the Plateau since the intensive destruction by human beings. Currently, it is difficult to find old coniferous trees to carry out dendroclimatology studies. Given this situation, it is necessary to assess alternative deciduous trees that are suitable for climate reconstruction. Materials and methods Sixty-four cores were collected from 34 Quercus acutissima trees by increment corers in the Qiaoshan region. The cores were fixed, dried, and polished following the standard method of dendrochronology. Tree-ring width was measured by LINTAB at a resolution of 0.01 mm. The COFECHA program was used to ensure the accuracy of cross-dating, and the ARSTAN program was used to build the final tree-ring chronologies. The arithmetic average of the climate data (e.g., temperature, precipitation and relative humidity) from Yan’an, Xifeng and Yaoxian meteorological stations were used to analyse growth/climate relationships. Pearson correlation analyses were used to identify the relationship between chronology and climate factors. We also conducted spatial correlations to assess the spatial representativeness of the Qiaoshan RES chronology. Results The statistical results showed a high expressed population signal (EPS) and signal noise ratio (SNR), which demonstrated the high quality of the Q. acutissima chronology that contained relatively more climate signals. The Mann-Kendall method revealed that the climate in the study area has had a significant warming and drying trend since the 1960s. The Pearson correlation calculation showed that the STD and RES chronology was negatively correlated with the temperature and positively correlated with precipitation and relative humidity during the growth seasons. The RES chronology of Q. acutissima showed the highest correlation with precipitation in March—July of the current year (r = 0.58, p<0.001) and could be regarded as the precipitation series for the past 136 years. Discussion Tree-ring chronologies from semiarid regions are usually sensitive to precipitation. The low values of the Q. acutissima RES chronology from the Qiaoshan region corresponded well with the drought events recorded by historical documents and with the observed climate data. The Q. acutissima RES chronology was also significantly correlated with the dry and wet index (DWI), which was derived from historical documents, in central and northern Shaanxi and with the regional precipitation reconstruction for the western Loess Plateau by an ensemble of ten tree-ring width chronologies. The good association among these chronologies confirms the potential of the Q. acutissima chronology for future climate reconstruction. Spatial analysis indicated that the RES chronology had a strong spatial representativeness for the March—July precipitation variability. ConclusionsQ. acutissima is a moisture-sensitive species on the central Loess Plateau and shows great potential for climate reconstruction in the future. Recommendations and perspectives This study established the first oak Q. acutissima tree-ring chronology, which demonstrated a strong precipitation signal, on the central Loess Plateau. This study will contribute to ecological studies and climate reconstructions in the future.
Keywords: central Loess Plateau; Quercus acutissima; tree-ring climate response