Spatio-temporal Variations Of Climate-growth Relationships For Three Hardwood In Northeast China

Tree rings at different spatial and temporal scales can reflect the impacts of environmental change on tree growth, and can be critical for understanding the influence of climate change on forest ecosystems. Here, we investigated the spatio-temporal variation of climate-growth relationships of three broadleaved tree species (Fraxinus mandshurica, Phellodendron amurense, and Juglans mandshurica) in a broadleaved Korean pine mixed forest in the north China. Tree-ring chronologies from six sample sites were established, transformed into principal component analysis (PCA), and analyzed through correlation analysis. With these analyses, climate factors limiting the radial growth were identified, as well as the detailed spatial radial growth-climate associations. The responses of the tree species at similar sites to climate factors differed significantly. Radial growth of J. mandshurica was limited by monthly total precipitation and minimum temperature, whereas P. amurense and F. mandshurica were mainly affected by monthly mean minimum temperature. This suggests that climate-growth relationships are affected by species-specific characteristics. With changes in temperature and precipitation patterns, the three hardwoods differed in their spatial growth response to climate factors. The radial growth of J. mandshurica in Fangzheng and Xidaquan was positively correlated with minimum June to August temperatures (P< 0.05). In contrast, it was positively correlated in Fenghuangshan with minimum temperature and precipitation in May and June (P < 0.05). The radial growth of P. amurense and F. mandshurica decreased from west to east with precipitation changes, since the correlation coefficients between tree-ring index and precipitation decreased from west to east. Results confirmed the general conclusion that the climate-growth relationship varies with latitudinal gradient. More specifically, the correlation coefficients of J. mandshurica between tree-ring index and temperature increased with latitudinal gradient. In contrast, it was positively correlated turn into a negative correlation with precipitation. It is not obvious in P. amurense spatial growth response to climate factors, three sites tree-ing index was a positive correlation with temperature, specifically, it was significant positively correlated with temperature and in Februay、june and September (P< 0.05). F. mandshurica were mainly affected by monthly mean temperature. With the increase of latitude its correlation with temperature appeared the phenomenon of "two head higher and middle lower".Temperatures have increased since 1980 in the northeast China, and the radial growth of the three hardwoods was consistent before 1980. However, climate factors affect growth differently, these boreal tree species showed inconsistent spatio-temporal variation to the recent warming between in Xiao Xing’an Mountains. And Changbai Mountains. Radial growth of three hardwoods increased with rapid warming since 1980 in Changbai Mountains. It is obvious between growth rate and response of three hardwoods before and after 1980 in Xiao Xing’an Mountains. The boreal tree species showed inconsistent spatio-temporal variation to the recent warming, with J. mandshurica being probably the most sensitive species. Radial growth of P. amurense and F. mandshurica increased with rapid warming since 1980, whereas tree growth of J. mandshurica decreased after 1980. Trees radial growth showed time-dependent relationships to interannual climate variation, A shift in climate facilitated comparison of growth-climate relationships during two distinct periods in Xiao Xing’an Mountains. Tree growth showed an internally consistent negative response to temperature after 1980, in contrast, it was negative correlated turn into a positively correlation with precipitation. Therefore, the radial growth of three hardwoods may be subjected to drought stress and a subsequent decline in radial growth in Xiao Xing’an Mountains, if global warming continues or exacerbates. In contrast, the radial growth of three hardwoods may benefit from increased temperatures through enhanced radial growth. For future research, the spatio-temporal variation of growth-climate relationship of the three hardwoods could be explored further by investigating the tree ring anatomical and physiological responses.