Abstract:

Dendroclimatology is one of the most important methods for monitoring and reconstructing global climate change. Variations of tree-ring growth in conifers reflect temperature fluctuations, especially in high latitude regions. Larix gmelinii and Pinus sylvestris var. mongolica are two major conifer species in boreal forests in the northernmost region of China. Densitometry was used to analyze tree-ring width and density in these two species in Mohe, Heilongjiang Province, China. Seven tree-ring variables (maximum density, minimum density, mean earlywood density, mean latewood density, earlywood width, latewood width and annual ring width) were investigated using Dendro2003 and compared with meteorological data from a weather station near the sampling site. The maximum density, mean latewood density, earlywood width, latewood width and annual ring-width in Larix gmelinii were higher than those in Pinus sylvestris var. mongolica. However, the variance among all the densitometric variables in Pinus sylvestris var. mongolica was significantly higher than that in the Larix gmelinii, but the variance of total ring width was different. Both residual chronologies of tree-ring density were significantly correlated but no significant correlations were found between the tree-ring width chronologies of the two species. The maximum temperature controlled the latewood density of both species in July and August. In addition, the latewood density of Pinus sylvestris var. mongolica was closely related to the length of the growing season. Correlation analysis also demonstrated that the annual ring widths of Larix gmelinii were sensitive to the temperature at the beginning of the growing season, but the ring widths of Pinus sylvestris var. mongolica did not have any significant climatic response. In summary, although Larix gmelinii and Pinus sylvestris var. mongolica had different tree-ring growth patterns, the tree-ring maximum density of these two species was highly responsive to temperature in the late growing season. The dendroclimatic growth characteristics of these two species have potential for reconstructing climate in this region.

Key words: Larix gmelinii, Pinus sylvestris var. mongolica, Tree-ring density, Tree-ring width, Climate change