Daily stem radial variation ofPinus koraiensisand its response to meteorological parameters in Xiaoxing'an mountain

Abstract

In the Xiaoxing忆 an mountain of northeastern China, the primary temperate forest is dominated by Korean pine ( Pinus koraiensis Sieb. Et Zucc) mixed with some deciduous species. Furthermore, Korean pine is a major source of timber production in this area. In spite of the importance of this tree species, no published data are available on the daily stem radial variation of Pinus koraiensis and its response to meteorological parameters in northeastern China. In this study, we measured the growth patterns of stem diameter of Pinus koraiensis between April and November 2012, in Liangshui National Nature Reserve. Automatic point dendrometers were used for the continuous monitoring of tree growth. To perform the statistical analyses, the data were split into 15鄄day intervals during the growing season. The relationships between stem radial increment rate and meteorological parameters were assessed using the Pearson correlation coefficient. The meteorological parameters measured were mean, maximum and minimum air temperatures, soil temperature, air relative humidity, vapor pressure deficit, and precipitation. By dividing the dendrometer day鄄night data, our results demonstrated that the diurnal growth pattern was resolved into the three distinct phases: ( 1) radius contraction phase, ( 2) radius expansion phase, and ( 3) radius increment phase. During the period of measurement, the diameter of the stem usually exhibited daytime shrinkage and night鄄time expansion. An entire circadian cycle was constituted of a phase of contraction