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A method was developed, based on Bayesian model averaging (BMA), to reconstruct regional mean temperature. Different from the arithmetic mean, which gives equal weight to each chronology, BMA weights the chronologies according to their contributions to the actual temperature variances. Thus, BMA holds advantages in integrating chronologies to reconstruct the regional mean temperature. The regional mean temperature for the Yunnan-Guizhou Plateau was reconstructed for the past four centuries (1628-2005) using BMA, which performed better than the simple arithmetic mean. The reconstruction explained 41.33% of total observed temperature variances during the period of 1961-2005. The warmest decade was found to be 1840-50 and the coldest 1810-20 prior to the instrumental period. The reconstructed temperature showed a high correlation ( r > 0.7, p < 0.001) with gridded observed temperatures in most grid cells of the Yunnan-Guizhou Plateau, suggesting that the regional temperature changes were captured well by the reconstruction. [ABSTRACT FROM AUTHOR]

[Display omitted] • A temperature of 5.5 °C is critical for earlywood onset growth in spring. • A temperature of 2.5 °C may be critical for pine end growth in autumn. • Warming advanced and lengthened the xylem growing season. • An earlier and longer growing season resulted in a greater radial increment. Temperature plays a key role in phenology and growth of dominant tree species and hence in the structure and function of coniferous forests in cold temperate zones. We used a dendrochronological method to determine the critical temperatures of Pinus sylvestris var. mongolica (Mongolian pine) radial growth and the xylem growing season. Results showed that Mongolian pine radial growth is sensitive to daily mean temperatures of 4.0–5.5 °C in early spring, 14.0 °C in summer and 2.0–2.5 °C in autumn. A temperature of 4 °C might be the initial temperature required for sap flow, photosynthesis and tree germination in this area in early spring, and 5.5 °C is the most critical temperature for earlywood onset growth. The advance and extension of temperature 14.0 °C in summer can exacerbate water stress for trees and inhibit earlywood growth under the condition of insufficient precipitation. In autumn, 2.0–2.5 °C may be the minimum temperature for the xylem growth. These critical temperatures are important in predicting the changes in the phenology of cambial activity and the growth of conifers in cold temperate regions under a scenario of a warming climate. We defined the mean xylem growing season of pines in this region as 151 days from early May to early October. With the increase in temperatures during 1972–2015, the start date of the xylem growing season advanced by 0.24 days/year, the duration of the xylem growing season increased by 0.27 days/year and the basal area increment of Mongolian pine increased significantly (P < 0.01). The influence of the earlier and longer xylem growing season compensated the negative effect of high initial temperature (14.0–15.0 °C) in some months, resulting in an increase in tree radial increment in this area. The warmer climate will lead to a longer xylem growing season, resulting in greater wood production with an adequate supply of water available. [ABSTRACT FROM AUTHOR]