Relationship between the radial growth of Picea meyeri and climate along elevations of the Luyashan Mountain in North-Central China

Picea meyeri is an indigenous evergreen conifer tree species that dominates most of the cold evergreen coniferous forest belt vertically ranging from 1850 to 2700 m a.s.l. in North-Central China. This species is an important agent for soil and water resource conservation in mountainous regions. Based on a tree-ring analysis of 146 increment cores sampled from 73 trees at different elevations, this study aimed to reveal the relationships between the radial growth of P. meyeri and climate along an elevation gradient and to identify the optimum sites for the planting and growth of P. meyeri. The results indicated the following: (1) The low Gleichläufigkeit (GLK) value (GLK = 34.5%) between the chronology of site 1 (at an elevation of 1970 m a.s.l.) and that of site 4 (at an elevation of 2650 m a.s.l.) showed that the radial growth pattern of P. meyeri at the lower elevation, near the species’ lower distribution limit, was not accordant with that at higher elevation. This differentiation in radial growth resulted from the varying climatic factors in the growing season, namely, an insufficient water supply in the summer months at lower elevations and cloudy or rainy days that may result in a shortened growing season and decreased solar radiation at higher elevations. (2) Compared to other spruce species in China in which radial growth has been studied along an altitudinal gradient, P. meyeri showed the most diversified relationships between radial growth and monthly mean temperature. Radial growth in this species showed a significant negative correlation with monthly mean temperature in May and June in the lower part of its vertical distribution belt, but this correlation disappeared at middle elevation and became significantly positive at higher elevations. In contrast, the relationship between the radial growth and the total monthly precipitation in the same period within a year displayed the opposite trend. (3) Radial growth of P. meyeri was also found to be more sensitive to climate factors at lower elevations than at higher elevations. This radial growth responded mainly to the temperature and precipitation conditions from May to July rather than from those over the whole year. (4) The large middle part (ranging from 2100 to 2500 m in elevation) of the vertical distribution belt of P. meyeri might provide this species with the best climate conditions and most favorable habitats for growth and, thus, the most appropriate sites for afforestation of this valuable species.