Age effect of xylem anatomical characteristics of young and old Korean pine and its response to climate change
Tree age is one of the most important factors affecting tree growth.In the context of climate warming,it is crucial to accurately evaluate the response and adaptation strategies of tree growth to climate change,and predict forest dynamics under climate change by utilizing the anatomical characteristics of tree trunk xylem and analyzing the growth-climate relationship of different tree ages.Wood anatomical methods were used to compare the anatomical characteristics of the xylem of younger and older Korean pine(Pinus koraiensis)and their responses to climate change in the mixed coniferous and broad-leaved forests in the Xishui of Xiaoxing'an Mountains,the northeastern China.The results showed that the main characteristics of tracheids in older P.koraiensis showed an overall upward trend with age,but the trend of changes in younger P.koraiensis was not significant.Both younger and older P.koraiensis showed significant fluctuations between 1840-1890 and 1980-2010.The relationship between the characteristics of some tracheids in younger and older P.koraiensis and climatic factors was consistent.The number of tracheids and theoretical hydraulic conductivity were negatively and positively correlated with the monthly maximum temperature,respectively.The relationship between total tracheid area(negative correlation),theoretical hydraulic conductivity(positive correlation),average hydraulic diameter(positive correlation)and monthly minimum temperature was consistent.The theoretical hydraulic conductivity was positively correlated with monthly total precipitation.The proportion of tracheids,average tracheid area,theoretical hydraulic conductivity,and average hydraulic diameter were positively correlated with averagely relative humidity,and the correlation was stronger in older P.koraiensis.The inconsistency of the relationship between the tracheid characteristics in younger and older P.koraiensis and climate factors was reflected in the positive correlation between the proportion of tracheids,average tracheid area,total tracheid area and average hydraulic diameter with monthly maximum temperature in older P.koraiensis,while the negative correlation was observed in younger P.koraiensis.The number of tracheids in older P.koraiensis was positively correlated with the minimum temperature from July to September,while younger P.koraiensis showed a significantly negative correlation.Except for the theoretical hydraulic conductivity,the relationship between other tracheid characteristics and precipitation was basically opposite for older and younger P.koraiensis,with a stronger correlation between the number of tracheids.Older P.koraiensis was significantly positively correlated with total precipitation in July,September,and whole year,while younger P.koraiensis was significantly negatively correlated with total precipitation in June and whole year.The correlation between the characteristics of tracheids in older P.koraiensis and monthly average relative humidity was either positive or not significant,while younger P.koraiensis was negative.Temperature was the main climatic factor limiting the growth characteristics of tracheid of younger and older P.koraiensis.The influence of precipitation was relatively weak,and the impact of average relative humidity on the growth of younger and older P.koraiensis was not significant.With climate warming,the trend of climate warming and drying in Xiaoxing'an Mountains region was increasing,and there were differences in the impact on the growth of older and younger P.koraiensis.If the climate continues to warm or intensify,younger P.koraiensis will experience growth decline.
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