Abstract
Changes in minimum winter temperature (MWT) and their potential effects on plant growth and development have been gaining increased scientific attention. To better understand these changes across long temporal scales, the present study used dendroclimatological techniques to assess variations in MWT in Southwestern China. Using data from Rhododendron species distributed in areas above the tree-line, a regional composite chronology was generated for a 341-year period. Based on the significant negative correlation between MWT values and ring-width, the most reliable parts of this chronological data were then used to reconstruct MWT values for the past 211 years. This reconstructed MWT series showed decadal to multi-decadal fluctuations. Three distinct cold periods prevailed during 1823–1858, 1882–1891 and 1922–1965, while four warm intervals occurred in 1800–1822, 1858–1881, 1892–1921 and 1966–2011. Our reconstructed MWT reveals a warming trend over the most recent eight decades, which is in agreement with instrumental observations. However, the MWT values and rate of warming over the past seven decades did not exceed those found in the reconstructed temperature data for the past 211 years. Spatial correlations reveal that the MWT in Southwest China is strongly associated with regional temperatures in the Eastern and Central Himalaya, Northern China, and the Indian Peninsula. Larger scale climate oscillations of the Western Pacific and Northern Indian Ocean as well as the North Atlantic Oscillation probably influenced the region’s temperature in the past.
Highlights
Winter temperatures have only recently been recognized as being more variable than annual and summer temperatures (Kreyling 2010)
The mean sensitivity (MS) was 0.16, indicating that our chronology showed a low level of annual variation, which is similar to results from other studies (Liang and Eckstein 2009; Lu et al 2015)
The most recent eight decades (1930–2011) experienced a continuous increase of minimum winter temperature (MWT) when the value changed from −13.04 °C in 1930 to −8.14 °C in 2011, which is in accordance with instrumental observation
Summary
Winter temperatures have only recently been recognized as being more variable than annual and summer temperatures (Kreyling 2010). This has stimulated a growing interest in the critical effects of winter climatic conditions on terrestrial organisms (Caroline et al 2015). MWT shapes the distribution and range of many species (Box et al 1993; Matsui et al 2004), acting as a major determinant of their performance and regulating community composition and ecosystem dynamics (Crumpacker et al 2001; Schmitz 2004). Understanding past variations in MWT and their effects on the earth’s ecosystems will be necessary for the accurate prediction of future changes and for the development of suitable responses and strategies for conservation in the context of climate change
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