Research Of Dynamic Changes And Responses Of Korean Pine Growth Under Climate Change In Northeastern China

Northeastern China is an area significantly impacted by global climate change.In recent decades,the temperature has increased significantly,while precipitation has not changed significantly.The broad-leaved Korean pine(Pinus koraiensis Sieb.et Zucc.)forest is the zonal climax community of northeastern forests.Korean pine is the dominant species of broad-leaved Korean pine forests,and it is a rare and valuable tree species in China.The dynamic changes of broad-leaved Korean pine forests are directly related to the stability of forest vegetation in the region.Changes in the growth of Korean pine directly affect the dynamics of broad-leaved Korean pine forests.To explore the dynamic changes and responses of Korean pine growth under alternative climate change scenarios,we used dendrochronological methods to examine four latitudinal gradient plots and three altitudinal gradient plots within the distribution area of the original broad-leaved Korean pine forests in northeastern China.We examined the effects of latitudinal gradient,altitudinal gradient,intraspecific variation,and diameter classes on the growth responses of Korean pine in response to climate.In addition,dynamic changes of Korean pine growth under alternative climate change scenarios were predicted.This study provides a deeper understanding of the impact and consequences of climate change on broad-leaved Korean pine forest ecosystems in northeastern China,and it forecasts spatial and temporal changes to the distribution pattern of broad-leaved Korean pine forest ecosystems.The results also provide a scientific basis to improve management of broad-leaved Korean pine forest ecosystems.The main findings were as follows:(1)The relationship between the radial growth of the Korean pine and the climatic factors was different in the latitude gradient.We observed different responses of Korean pine radial growth to local climatic factors in four different latitude plots.In the most southern sample plot,the radial growth of Korean pine was significantly positively correlated to the average relative humidity,but it had a significantly negative correlation to the average maximum growing season temperature.The two samples in the central region were sensitive to the moisture factor and high temperature of the growth season,showing significant positive correlation and negative correlation respectively.In the northernmost sample plot,growth was positively correlated to the temperature variables of most months.However,there were some similarities between the responses in different latitudes.The climatic variables in June of the measurement year were the main factors limiting the radial growth of Korean pine at all latitudes,and the average maximum temperature in June of the measurement year was highly negatively correlated with radial growth for Korean pine at all sites.(2)The relationship between the radial growth of the Korean pine and the climatic factors was different in the altitudinal gradient.In the three altitudinal gradient plots of the original broad-leaved Korean pine forests in the Changbai mountain nature reserve,the radial growth rate of Korean pine decreased gradually and the average annual ring width decreased with increasing elevation.At high altitudes(1290-1300 m.a.s.l.),Korean pine radial growth was more sensitive to temperature variables,particularly the mean minimum temperature.At middle altitudes(1030-1040 m.a.s.l.),it was mainly affected by water variables from the previous year.However,at lower altitudes(740-750 m.a.s.l.),radial growth was more sensitive to water variables of the measurement year.(3)The results showed that there was no significant difference in the response to the climatic factors of Korean pine with fine bark(Pinus koraiensis forma leptodermis)(the original variant)and Korea pine with coarse bark(Pinus koraiensis forma pachidermis)(the variant).From 1902 to 2009,climate factors during the growing season,particularly June,were the primary factors affecting the radial growth of both types of Korean pine in the study area.The temperature showed a significant negative correlation to radial growth,and precipitation showed a significant positive correlation.With the rapid rise of temperature and drought conditions after 1970,radial growth of both pines was more sensitive to the climate factors than previously,especially growing season temperature and PDSI.(4)The diameter classes had some influence on the climate-growth relationship of Korean pine.Large diameter Korean pine chronologies contained more weather information,and were more suitable for climate-growth response analyses.There were many similarities in the response of large diameter and small diameter Korean pine to local climate factors within the same study area.However,the small diameter Korean pine was more sensitive to the climatic factors of the previous year,but the large diameter Korean pine was more sensitive to the climatic factors of current year,especially the climatic factors of the growing season.(5)There was great similarity between the variation of volume and the variation of basal area increment of Korean pine within the same study area,and their relationships with climatic factors displayed a similar response;however,the latitudinal gradient and altitudinal gradient had a strong influence on both variables.For a period of 50 years,volume and basal area increment of Korean pine in the Baishilazi nature reserve initially increased and decreased afterwards;trees in the Liangshui nature reserve and lower altitude of Changbai mountain nature reserve had a fluctuating pattern,and in Shengshan nature reserve both measures significantly increased.Temperature has a greater influence on the two growth indices of Korean pine in the southernmost and northernmost,and the two plots in the center of the distribution area were affected by both temperature and precipitation.Across the altitudinal gradient,the highest values of volume and basal area increment of Korean pine were all in lower elevation plots,followed by mid-elevation plots and high altitude plots,respectively.For a period of almost 50 years,the values of volume and basal area increment of Korean pine in lower elevation and middle elevation plots fluctuated,but in higher altitudes the values significantly increased.The two growth indices of Korean pine in lower elevation plots were mainly affected by the high temperatures and precipitation within the growing season and the average minimum temperature of the measurement season.They were mainly affected by the precipitation factors of the growing season,especially precipitation and PDSI.The average minimum temperature was the main limiting factor in high elevation plots.(6)The inter-annual variability of volume,basal area increment,and ring width index of Korean pine was similar,but there were some differences in their responses to climate factors.Volume was more sensitive to climate factors than the other two indices.In the nearly 40 years when temperature increased significantly,the variation trends of three growth indices of Korean pine were different across latitudinal and altitudinal gradients.Across the latitudinal gradient,the three growth indices of Korean pine in the southernmost Baishilazi nature reserve showed a significant decrease,and they displayed a significant increase in the northernmost Shengshan nature reserve;changes from the Liangshui nature reserve and lower altitude of Changbai mountain nature reserve were not significant.(7)The Korean pine growth-climatic factors models were obtained by stepwise regression method.Based on the prediction data of meteorological data in the two authoritative reports,the three growth indexes of Korean pine were estimated.The results showed that,Under alternative climate change scenarios,the three growth indexes of Korean pine in high latitude and high altitude areas displayed significant upward trends.The tree ring width index of Korean pine in the low latitude area showed a downward trend over time.In the mid-latitude areas,there was no obvious pattern or unpredictable due to the fact that the growth was not significantly related to annual average temperature and annual total precipitation.We can predict that under the climate change scenarios,the southern boundary of broad-leaved Korean pine forests may move northward or towards higher altitudes;the temporary change in the central latitude area is not significant,the upper limit of the high altitude distribution will move up.In the case of significant increases in temperature and precipitation,the northern boundary may migrate to some palces with fertile soil in the eastern slope of the Daxing’an Mountains.The pattern of forest ecosystems in Northeast China will change.