Jiang Yuan;Zhang Yiping;Guo Yuanyuan;Kang Muyi;Wang Mingchang;Wang Biao;

[Jiang, Yuan; Zhang, Yiping; Guo, Yuanyuan; Kang, Muyi; Wang, Mingchang; Wang, Biao] Beijing Normal Univ, State Key Lab Earth Surface Proc & Resource Ecol, Beijing 100875, Peoples R China.

[Jiang, Yuan; Zhang, Yiping; Guo, Yuanyuan; Kang, Muyi; Wang, Mingchang; Wang, Biao] Beijing Normal Univ, Coll Resources Sci & Technol, Beijing 100875, Peoples R China.

[Zhang, Yiping] Henan Univ Sci & Technol, Coll Forestry, Luoyang 471003, Peoples R China.

ABSTRACT:  Altitude-related climatic factors, especially temperature, are important factors that affect tree growth in mountain forest ecosystems. The aims of this study were to estimate the intra-annual radial growth differences of Larix principis-rupprechtii ( L. principis- rupprechtii) between its upper and lower distribution limits, at 2740 and 2040 m a. s. l, respectively. Dynamics of xylem growth were observed by collecting microcore samples weekly during the 2011 growth season. The result indicated that different strategies were adopted at the two selected sites. Trees at the upper distribution limit adopted an "intensive strategy" with higher maximum growth rates ( 0.69 cell . day- 1) within a shorter duration of 95 days, producing 21 new tracheids. By contrast, trees at the lower distribution limit exhibited an "extensive strategy" with lower maximum growth rates ( 0.53 cell .day- 1) over a longer duration of 135 days, producing 50 tracheids. The soil temperature was probably the main factor limiting the onset of cambial activity for L. principis- rupprechtii, its daily mean thresholds for onset were 0 degrees C and 1.4 degrees C at the upper and lower distribution limits, respectively. These results indicate that L. principis- rupprechtii is able to adjust its xylem growth according to environmental conditions.

Published in FORESTS.2015,6(11):3809-3827, DOI: 10.3390/f6113809