Climate-growth Relationships Of Three Hardwood Species In The Northeast, China

Global warming shows quite high potential menace to Human life and ecosystem. There is a close relationship between forest ecosystem and climatic change. Broad-leaved korean pine forest is an important forest type and has highly sensitive to global climate change in boreal forest ecosystems. Three hardwood species (Fraxinus mandshurica, Juglans mandshurica and Phellodendron amurense) and Pinus koraiensis are main tree species of natural forests in this region. These species are critical to explore responses of boreal forests to climate change in northeast China. Dendrochronological methods were used to establish four standard chronologies, including424cores of three hardwood species were collected from Heilongjiang, and37cores of Pinus koraiensis were collected from Dunhua region. Then, correlation analyses were made between these four chronologies and local climatic factors. The results indicated that, temperature was the significant factor to determine radial growth of Fraxinus mandshurica in Heilongjiang. Fraxinus mandshurica in Liangshui natural reserve has extremely sensitive to temperature variation, that same year, a significant positive correlation was observer between Fraxinus mandshurica and low temperature in February-April, June, August, October and December, Fraxinus mandshurica in Mudanjiang region takes second place, Fraxinus mandshurica in the non-protective area has weak correlation with temperature. Radial growth of Phellodendron amurense was affected by the comprehensive influence of temperature and precipitation. The samples in Mudanjiang region have the lowest correlation relationship with climate, and have a significant positive correlation with the low temperature in full year except for June and July. In Wuying region, there was a significant correlation between Phellodendron amurense and temperature and precipitation in February of current year, among which precipitation presents significant negative correlation, and Phellodendron amurense in Liangshui natural reserve has weak correlation with temperature sensitivity. Juglans mandshurica have the lowest correlation relationship with climate. In Mudanjiang region, there was marked significant positive correlation between Juglans mandshurica and the low temperature in autumn, however, it is showed negative correlation with high temperature on April and precipitation on August. Juglans mandshurica and low temperature on August has negative correlation significantly, but a significantly positively related was expressed with high temperature on September.in the non-protective area. Making a comparison of the chronology curve of three hardwood species in the protective and non-protective, we know that, radial growth of Fraxinus mandshurica and Phellodendron amurense were weaken in the global warming area in recent30years. According to the positive effect of Fraxinus mandshurica and coniferous mixed forest, growth was promoted distinctly. In Mudanjiang region, high temperature was beneficial to fine root activities and photosynthesis of Fraxinus mandshurica near the end of the growing season. Phellodendron amurense had the strong ability of phototaxis, and reflected the obviously response difference of the different latitude. Juglans mandshurica was provided with the weakest sensitivity to climatic factor, and the climatic factor difference in correlation besides different latitudes, also not exclude the probability that provenance difference. Three hardwood species and P. korainsis in Dunhua have similar responses to climatic factors, that is, significantly positive correlated with temperature. However, they are weakly correlated with precipitation. Monthly minimum temperature in whole year was positively correlated with P. korainsis chronology. F. mandshurica is most significant to be limited by monthly minimum temperature in three hardwoods. It positively correlated with January to October minimum temperatures. The next is P. amurense which is significantly positive correlation with February to September temperature. J. mandshurica has weak correlation with minimum temperature and just significantly correlated with May, June and September temperatures. In summary, temperature is the main limited factors of radial growth for broadleaved P. korainsis forests in this region, especially for minimum temperature in growing season (April to September). Therefore, minimum temperature in growing season since1854in Dunhua was reconstructed by using mean chronology of three hardwoods and P. korainsis. The reconstruction equation (Y=4.281nX+8.774) explained62.4%of the variance in minimum temperature. Segmented test proved that this reconstruction equation is stable. Variations of cool and warm periods are identical by comparing with previous studies. Reconstructed temperature of the last158years in this region showed three warmer (1860-1873,1938-1947and1991-2010) and cooler periods (1888-1933,1965-1971and1977-1980) and significant warming in recent30years. Minimum temperature in Dunhua showed8.4,6.9-6.3,3.7,2.5and2.2years of significant change cycles.