Seasonal cambial activity of relict Chinese pine at the northern limit of its natural distribution in North China - exploratory results

The seasonal dynamics of cambial activity of Chinese pine (Pinus tabulaeformis Carr.) was studied at the northern limit of its natural distribution in a semi-arid grassland ecosystem in North China. We collected micro-cores from five even-aged trees at weekly intervals from April 15 to September 16, 2006. Cell division in the cambial zone of these trees started within the third week of May. In June and July the rate of xylem cell production was highest and around mid-August cell division ended. However, cell-wall formation was not yet completed around mid-September. The cell-division period appears to coincide with the time of highest monsoon precipitation and of above 0 °C daily minimum temperature. Moreover, the cambium activity period seems to be in agreement with the time of the highest number of sunshine hours/day. These preliminary results are important for dendroclimatic studies with Chinese pine in North China and can furthermore be used as a benchmark for future monitoring activities in ecologically similar areas.