大小龄红松木质部解剖特征的年龄效应及其对气候变化的响应差异

Age effect of xylem anatomical characteristics of young and old Korean pine and its response to climate change

树龄是影响树木生长的最重要因素之一。在气候变暖背景下,利用树干木质部解剖特征,分析不同树龄生长-气候关系,对准确评估树木对气候变化的响应和适应策略、预测气候变化下的森林动态至关重要。利用木材解剖学方法,比较了小兴安岭溪水地区针阔混交林内大、小龄红松(Pinus koraiensis)木质部解剖特征及其对气候变化的响应异同。结果表明:大龄红松主要管胞特征值随年龄增加而呈上升趋势,但小龄红松的变化趋势并不明显,两者均在1840—1890年和1980—2010年间出现剧烈的波动。大、小年龄红松部分管胞特征与气候因子的关系具有一致性,管胞数量和理论导水率分别与月最高温度负相关和正相关;总管胞面积(负相关)、理论导水率(正相关)、平均水力直径(正相关)与月最低温度的关系一致;理论导水率与月总降水正相关;管胞占比、平均管胞面积、理论导水率、平均水力直径均与平均相对湿度正相关,且大龄红松相关性更强。大、小年龄红松管胞特征与气候因子的关系的不一致表现在,大龄红松管胞占比、平均管胞面积、总管胞面积和平均水力直径与月最高温度正相关,而这些关系在小龄红松则表现为负相关。大龄红松管胞数量与7—9月最低温度正相关,而在小龄红松表现为显著负相关;大、小龄红松除理论导水率外其他管胞特征与降水关系基本相反,其中管胞数量的相关性更强;大龄红松与7月、9月、年总降水量显著正相关,而小龄红松与6月和年总降水显著负相关;与月平均相对湿度的相关关系大龄红松表现为正相关或不显著,而小龄红松呈负相关关系。温度是限制大、小龄红松管胞特征生长的主要气候因子,降水的影响相对较弱,平均相对湿度对大小龄红松的影响差异不大。近几十年,小兴安岭地区气候暖干化趋势逐渐增强,这种暖干化会造成大、小龄红松生长的响应差异。若气候持续变暖或加剧,小龄红松会出现严重生长衰退。

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.