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

Responses of Larix principis-rupprechtii Radial Growth to Climatic Factors at Different Elevations on Guancen Mountain, North-Central China

Larix principis-rupprechtii is an important afforestation tree species in the North China alpine coniferous forest belt. Studying the correlations and response relationships between Larix principis-rupprechtii radial growth and climatic factors at different elevations is helpful for understanding the growth trends of L. principis-rupprechtiind its long-term sensitivity and adaptability to climate change. Pearson correlation, redundancy (RDA), and sliding analysis were performed to study the correlations and dynamic relationships between radial growth and climatic factors. The main conclusions are as follows: (1) The three-elevation standard chronologies all exhibited high characteristic values, contained rich climate information and were suitable for tree-ring climatological analyses. (2) Both temperature and precipitation restricted low-elevation L. principis-rupprechtii radial growth, while monthly maximum temperatures mainly affected mid-high-elevation L. principis-rupprechtii radial growth. (3) Mid-elevation L. principis-rupprechtii radial growth responded to climate factors with a “lag effect” and was not restricted by spring and early summer drought. (4) Long-term sliding analysis showed that spring temperatures and winter precipitation were the main climatic factors restricting L. principis-rupprechtii growth under warming and drying climate trends at different elevations. The tree-ring width index and Palmer drought severity index (PDSI) were positively correlated, indicating that L. principis-rupprechtii growth is somewhat restricted by drought. These results provide a reference and guidance for L. principis-rupprechtii management and sustainable development in different regions under warming and drying background climate trends.

Effects of the Pacific Decadal Oscillation on Thailand monsoon rainfall derived from a 194-year tree ring width chronology of teak trees from northwestern Thailand

Thailand is a predominantly agricultural country. An understanding of the dominant driver of decadal-scale changes in Thailand monsoon (TM) rainfall trends is particularly important in terms of agro-meteorological information and monsoon predictions. In this study, a 194-year tree ring chronology of teak trees in northwestern Thailand was developed. Correlations between the tree ring width index (i.e., the Susa index) and climate variables confirmed that this index can be used as a proxy for rainfall in the early monsoon season from May to July. Similar variations with other regional tree ring chronologies confirmed the reliability of the climate signals embedded in the tree ring widths. The possible relationship between the Susa index-based TM rainfall and the Pacific Decadal Oscillation (PDO) was examined. Spectral analysis showed statistically significant PDO periodicities of between 22 and 24 years. The spatial correlations detected across the key regions of the PDO revealed associations with the north Pacific sea surface temperature during recent decades. The long-term relationships between the Susa index and the PDO were nonstationary at the decadal timescale. Positive correlations were found for AD 1824-1875 and AD 1900-1955, whereas negative relationships prevailed for AD 1876-1899 and 1956-2017. The El Niño Southern Oscillation-related anomalous TM was indeed stronger during both the warm and cold phases of the PDO. The PDO is therefore identified as a driving factor of decadal climate variability. This study leads the way to understanding the changes in the TM-PDO relationship over time and demonstrates the utility of teak tree ring width as a potential proxy for PDO teleconnection.

Joint influence of genetic origin and climate on the growth of Masson pine (Pinus massoniana Lamb.) in China

Adaptive of trees and its correlation with the climatic are causing changes in tree species performance and distribution, which will change breeding programs and influence forest productivity. To further evaluate the joint influence of climatic factors and provenance on the ring width (RW) and ring density (RD) of Masson pine. We selected 18 provenances at Chun’an (CA) and Taizi Mountain (TZS) test site, which representing four different breeding regions, including the south, west, north and east-central regions. The results showed that the provenance effects were significantly for the RW and RD. The provenances from high temperature and low latitude regions had greater mean RW compared to species from local and cold sources. The geographical genetic variation in wood traits is generally weak. The correlation between RW of Masson pine and precipitation was stronger in the relatively arid TZS site compared with that in relatively wet CA site, as well as the effect of temperature and precipitation on RD was earlier than that in CA test site. The response relationship between establishing the width of tree rings and the environmental variables of provenance indicated that during the transition from the northern and western breeding regions to the eastern and southern breeding regions, the response of RW to climate factors changed from being temperature-based to being precipitation-based. In addition, the response of provenance to the climate of seed sources origin showed their own variation characteristics in each breeding area. Therefore, genetic improvement of big diameter wood and wood density can be gain through selection of provenance and analysis of adaptability.