Manyu DONG ^1,3, Yuan JIANG ¹, Wentao ZHANG ¹, Yangang YANG ², Haochun YANG ¹

¹State Key Laboratory of Earth Surface Process and Resource Ecology, College of Resource Science and Technology, Beijing Normal University, Beijing 100875, China

² Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China

³ College of Life Science, Beijing Normal University, Beijing 100875 China

 

Abstract: Alpine treeline is an important ecological boundary, marked by a change in site conditions and plant communities when crossing the forest limit, and tree growth at treeline is strongly constrained by the harsh environment. Finer resolution studies of tree radial variation on short temporal scales can be useful to explore the main physical variables that trigger the radial growth. From 19th Oct. 2008 to 25th Oct. 2009, we continuously monitored the stem radial variation of Picea meyeri Rebd. Et Wils trees using point dendrometers, at the treeline of Luya Mountains (altitude 2700 m a.s.l.), North China. Our results showed that there were two reverse daily variation patterns in the warm and cold seasons, which were related to the daily transpiration course and daily stem freeze-thaw cycles, respectively. Annual stem radial growth of Picea meyeri was divided into the four distinct periods: 1) spring stem rehydration, 2) summer stem rapid growth, 3) autumn stem dehydration contraction and 4) winter stem stagnation. The stem radial variation of Picea meyeri at the alpine treeline was closely dependent on climate conditions. Soil temperature was the most important factor affecting radial growth, which determined the initiation of radial growth and the cambial activity during the growing season.

 

Keywords: Picea meyeri, dendrometer, treeline, stem radial growth, growth-climate relationship