Seasonal cambial activity and tree-ring formation of Pinus merkusii and Pinus kesiya in Northern Thailand in dependence on climate

Abstract

This study is aimed at characterizing the cambial dynamics and its dependence on climate of two pine species native to Thailand, Pinus merkusii and Pinus kesiya and at describing their climatic response over 148 years. The samples for cambial activity analysis were taken monthly from March 2000 to February 2001, and the cambial activity was determined by counting the number of undifferentiated cell layers between mature xylem and phloem in transverse sections. Statistical analysis was done using Pearson's correlation. For the dendroclimatological analysis, samples were collected from the same sites in March 2004, and dendroclimatological standard techniques were applied. The results indicated that soil moisture influenced the cambial activity of P. merkusii and P. kesiya, however that rainfall and temperature had no significant effect on the cambial activity of both species. The response function described the relationship between tree-ring widths indices and monthly rainfall and temperature and revealed that the growth of P. merkusii at Hung Boung depended positively from rainfall in May. P. merkusii at Bao Kaew, however, had a positive correlation with rainfall from previous November to current July, whereas temperature in the preceding autumn and winter should be above-average and in the current spring and summer should be below-average. P. kesiya at Nong Kra Ting showed a slightly positive correlation with rainfall from February to June, but a strong dependence on rainfall in September. It can be concluded that the study of cambial activity could support our understanding of intra-annual variations and duration of tree-ring development, whereas the response function could help explain the average response of tree-growth to climate. © 2006 Elsevier B.V. All rights reserved.