[Reconstructing mean temperature of April-July in 1809-2018 based on tree-ring of Pinus taiwanensis in the Tianmu Mountain, East China]. / åŸºäºŽé»„å±±æ¾æ ‘è½®é‡å»ºåŽä¸œå¤©ç›®å±±åœ°åŒº1809­2018å¹´4­7月平均气温.

We established 340-year chronologies of total ring width, early wood width, and late wood width with tree-ring samples of Pinus taiwanensis at high altitude collected from the western Tianmu Mountain in northern Zhejiang Province. According to the criterion that subsample signal strength (SSS) should be larger than 0.8, the reliable period was from 1810 to 2019. Through the correlation analysis between chronologies and climatic factors, we examined the responses of tree ring growth to climate. The results showed that radial growth of P. taiwanensis was more sensitive to temperature than to precipitation. Comprehensively considering the correlation analysis results for the raw and first-order difference series, early wood width was significantly correlated with the early growing season mean and maximum temperatures of the prior year, while late wood width with prior May and current September mean and maximum temperatures. The correlation pattern of total ring width was similar to that of early wood width, although at a low level. The optimal correlation was between early wood width and prior April-July mean temperature. Based on this relationship, April-July mean temperature of the Tianmu Mountain, East China was reconstructed for the period of 1809-2018 with an explained variance of 61.5%. Both the raw and first-order difference series passed the split sample calibration-verification test. The warm periods were 1809-1833 and 1965-2018, with a cold period in 1834-1964. Temperature had risen rapidly since the 1960s. From the standpoint of low frequency, it reached an unprecedented level since the 1980s over the past 210 years. Spatial correlation analysis showed that the reconstructed temperature series could represent temperature variations of East China, which had a good agreement with a reconstructed regional temperature series from East China. Our results showed that P. taiwanensis had a great potential for paleoclimate reconstruction in East China.

[Growth response of Abies fargesii to climate in Shennongjia Mount of Hubei Province, Southeastern China].

A well-replicated Abies fargesii tree-ring width chronology in the Shennongjia Mount was developed to investigate its radial growth response to climate variables (e.g., monthly mean tempe- rature and total precipitation) and other growing season indicators (e.g., cumulative temperature, continuous days, initial and final dates). Correlation analyses showed that the tree-ring width was positively correlated to the mean temperatures of February, April and September, and negatively correlated to the total precipitation of September, prior September and prior December. The analyses between the chronology and other growing season parameters showed that tree growth responded positively to the cumulative temperature and continuous days of the growing season. The correlation was the highest when the growing season was defined as the days above the temperature threshold of 9.0 °C. Defined this way, the growing season typically started in late-May and ended in mid-September, lasting about 120 days. Correlation analyses were also conducted between the tree-ring growth and the initial and final dates of the growing season. Results showed that correlation was the highest for initial dates defined at 9.0 °C (with the coefficient of -0.25 and p-value close to 0.05), and for final dates defined at 9.3 °C (with the coefficient of 0.33 and p-value less than 0.05). All these results indicated that the sensitive temperature threshold for photosynthesis of A. fargesii was around 9.0 °C. The year 1978 marked an abrupt shift of climate in southeast China. We compared A. fargesii growth between pre-1978 and post-1978 periods. Results showed that as temperature rose, the growing season was lengthened with both earlier initial dates and later final dates. Longer growing season increased the A. fargesii growth in the Shennongjia Mount, southeastern China.

[High altitude Pinus taiwanensis Hayata growth response to climate in Jiulongshan and Guniujian, Southeastern China].

Two robust Pinus taiwanensis Hayata tree-ring width chronologies were developed at high elevation sites in Jiulongshan Natural Conservation Area (JLS01), southeastern Zhejiang Province and Guniujiang (GNJ01), southern Anhui Province, China. The reliable period was 1884-2010 for JLS01 and 1837-2008 for GNJ01, based on subsample signal strength (SSS) threshold value of 0.8. Meteorological data were monthly mean temperature, monthly total precipitation and monthly mean relative humidity, monthly total cloud cover, as well as monthly sunshine duration. The data from the meteorological stations around the sampling sites were averaged to represent regional climate, which were used in the correlation analyses with the tree-ring chronologies. The correlation analyses indicated that summer (prior June-July and current June) hydrothermal condition was the main limiting factor on radial tree growth at the two high elevation sites. For JLS01 chronology, significant positive correlations were found with prior June-July temperature and sunshine duration, significant negative correlations with prior June-July and current June precipitation and relative hu- midity, and total cloud cover of prior July. GNJ01 chronology was significantly positively correlated with prior July temperature as well as prior July and current June sunshine duration, negatively correlated with prior July and current June precipitation and relative humidity, as well as total cloud cover of prior June. These results showed that relatively high temperature could promote radial growth, whereas high precipitation, together with high relative humidity, high cloud cover and low sunshine duration, could limit the photosynthesis and thus restrain the radial tree growth.