Tree-ring stable carbon isotope-based June-September maximum temperature reconstruction since AD 1788, north-west Thailand

The first study of tree-ring stable carbon isotopes in Thailand has demonstrated that stable carbon isotope in northwestern Thailand represents a promising proxy for the temperature reconstruction of core-monsoon periods. A tree-ring delta C-13 chronology was constructed based on four cores covering the period of 1788-2013. After removing the long-term decreasing trend reflecting atmospheric CO2 concentrations, the Delta C-13 chronology was able to capture both temperature and hydro-climate signals Delta C-13 chronology showed particularly strong and significant negative correlation (r = -0.62, p < 0.0001) with June-September maximum temperature (CRU TS 3.24). The maximum temperature was reconstructed, which explained 37.8% of the variance in the instrumental maximum temperatures over the period of 1901-2013. The maximum temperature reconstruction revealed that four cooler and three warmer periods, as well as a slightly increasing temperature trend, occurred during the late seventeenth to mid-eighteenth centuries, which were followed by severe temperature fluctuations during the twentieth century century. While the sea surface temperature anomaly in the Indian Ocean might not affect the maximum temperature, its unstable relationship with the El Nino-Southern Oscillation (ENSO) was detected. In addition, a close relationship was observed between the maximum temperature and ENSO during the negative phase of the Pacific Decadal Oscillation (PDO), but this relationship was lost during the positive phase of the PDO

Tree-ring-based precipitation reconstruction in the source region of Weihe River, northwest China since AD 1810

A tree-ring width chronology of Picea purpurea Mast from Mt. Shouyang in the source region of Weihe River (SWR), northwest China, was developed in this study. Correlation analysis showed that the precipitation from previous August to current July was the limiting climate factor of tree growth. Using a reliable and stable linear regression model, which explained 42.6% of the variance of the actual precipitation during the calibration period from 1958 to 2014, a 205-year long precipitation series was reconstructed for the SWR. The dry years in the reconstruction were well supported by historical documents, and famous historical droughts were also recorded in the dry periods of a low-frequency scale of the reconstructed precipitation. As demonstrated by the spatial correlation patterns, the reconstructed series compared well with other hydroclimate records for northwest China, indicating that it could represent large-scale hydroclimate changes. The 2-8-year interannual cycles and the interdecadal quasiperiods of 15.9 years and 18.6 years revealed that the precipitation in this region was probably affected by the El Nino-Southern Oscillation and North Atlantic Oscillation. The dry/wet years corresponded well with the El Nino/La Nina events and the SWR commonly experienced droughts during the low periods of North Atlantic Oscillation

Variation in Climate Signals in Teak Tree-Ring Chronologies in Two Different Growth Areas

We developed two tree-ring chronologies of teak (Tectona grandis L.f.) from Mae Tuen (462-year, 1555⁻2016) and Umphang (165-year, 1852⁻2016) in Tak province, northwestern Thailand. The chronologies were based on 67 and 71 living teak trees, respectively. We used crossdating methods to check and verify the tree-ring width data and tree-ring chronology construction using the ARSTAN program. In this study, the two teak tree-ring chronologies from two different growth areas could not be crossdated. The relationship among these chronologies is, thus, relatively low (r = 0.33, n = 165, p < 0.01). This result shows that the growth of tree-ring structure from two sites can be affected by a variety of non-climatic patterns due to site variation, such as topography, nutrient, light, and internal factors. However, these chronologies have a significant positive correlation with rainfall, during the pre-monsoon season (April to May). As demonstrated by the spatial correlation patterns, these chronologies represent April to May rainfall, which was a limiting factor of teak growth from northwestern Thailand. While the difference in surface temperatures of the Indian Ocean Dipole (IOD) might not be affected by rainfall, its unstable relationship with the El Niño-Southern Oscillation (ENSO) was noted to have occurred

Tree-ring width-based precipitation reconstruction in Zhaogaoguan, China since 1805 AD

In order to further understand the past climate variation especially the history of drought and flood events in the East Asian summer monsoon (EASM) marginal area, precipitation from previous August to current July for the period of 1805-2014 AD was reconstructed from a ring-width chronology of Pinus tabulaeformis in Zhaogaoguan (ZGG), a site located in the EASM marginal area in northern China. The transfer function can explain 46.4% (adjusted to 45.4% for the loss of degrees of freedom) of the variance of the observed precipitation during the calibration period (1958-2014 AD). The reconstructed precipitation series revealed that the inter-annual variability was very prominent; 1843 and 1844 AD were the two wettest years, while 1931 and 1999 AD were the two driest years. We noticed that the droughts in 1900, 1906, 1931, 1955 and 1999 AD in the reconstruction series corresponded to the severe floods in the Yangtze River watershed in southern China during those same years. This phenomenon confirmed the typical climate pattern of northern droughts and southern floods in China. Moreover, the reconstructed precipitation series in ZGG showed synchronous variation patterns with the other tree-ring-based hydrological reconstructions in the marginal area of EASM on both inter-annual and inter-decadal scales, indicating the common precipitation variation characteristics of the EASM marginal area

甘肃竺尼山油松树轮宽度气候响应

甘肃省中部是东亚夏季风活动边缘带,也是我国北方环境敏感带,降水是制约当地农业社会发展的重要因素,因此对该区域过去降水变化开展研究有重要意义。本文在甘肃中部渭源县竺尼山采集油松树轮样本,建立了STD和RES年表。计算表明,RES年表与上年8月到当年7月的年降水总量相关最高(r = 0.59),二者存在比较一致的变化趋势,因此竺尼山RES年表可以代表当地过去降水的变化信息,它与同处于东亚季风边缘带的兴隆山和吐鲁沟的树轮年表(也被用来重建了当地的年降水变化)显著相关。三个地点树轮宽度变化一致,树木径向生长均受控于降水

Teak Tree-Ring Cellulose δ13C, δ18O, and Tree-Ring Width from Northwestern Thailand Capture Different Aspects of Asian Monsoon Variability

The inter-annual variability in tree-ring cellulose δ13C (δ13CTR, δ18OTR), and tree-ring chronology in teak (TRW) (Tectona grandis L.f.) trees from Northwestern Thailand during 1901–2009 AD was performed. The δ13CTR and δ18OTR have a positive correlation, significant at r =0.400, p <0.0001, and both of the stable isotopes were not significantly related to the TRW. The TRW is related to rainfall in the first half of the rainy season and has a strong relationship with the relative humidity. The δ18OTR captured moisture well throughout the rainy season, and the δ13CTR had a strong correlation with rainfall in the second half of the rainy season and had a high correlation with cloud fraction and vapor pressure. The δ13CTR and δ18OTR were associated with the stomata conductance response, but had no effect on photosynthesis. The three indices of the teak annual ring respond well to the variability in the Asian monsoon, and give us a better understanding of both the hydrological cycle and the factors that contribute to the growing of tropical broadleaf trees under changing climates