Abstract: The stem radius growth (SRG) of six samples of Picea meyeri and fi ve samples of Larix principis-rupprechtii nearby the tree-line of Luya Mou ntain in North China was measured by the dendrometer in the summer phase from Ju ly 15 to August 7 and the autumn phase from September 5 to October 9, 2007, with the environmental factors measured simultaneously. In the summer phase, there w as no significant difference in the sensitivity of SRG to the environmental fact ors fluctuation between the two species; but in the relatively cold and dry autu mn phase, the SRG of P. meyeri was more sensitive to the fluctuation of envi ronmental factors. The accumulated SRG of the two species increased linearly in summer phase, but decreased first and kept stable then in autumn phase, with the growth increment of P. meyeri fluctuated more than that of L. principis- rupprechtii. The SRG of the two species correlated positively with hydrologica l factors and negatively with thermal factors, and the SRG of P. meyeri was strongly affected by air humidity and temperature, while that of L. principis -rupprechtii was mainly affected by soil moisture.

Key words: Lonicera japonica, cadmium, hormesis, hyperaccumulation.