自然生长树木气孔导度对CO_(2)浓度升高的响应

Responses of Stomatal Conductance of a Natural Tree for the Past 240 Years to Changes of Atmospheric CO_(2) Concentration

研究了近 2 4 0 a自然生长树木气孔导度对 CO2 浓度变化的长期响应 .在测定树轮稳定碳同位素组成的基础上 ,计算了大气 CO2 浓度和叶片内部 CO2 浓度差 (ca - ci )和树木年轮面积与 ca- ci 的比例 (以 G表示 ) .ca- ci和 G均随 CO2 浓度的升高而有所增加 .在 1990年之前 ,ca- ci 的升高主要与植物同化能力的提高有关 ,190 0年之后 ,气孔对大气 CO2 的导通能力起主要作用 ;而 G的升高可能与 CO2 浓度升高改变了光合碳分配比例模式相联系 .进一步的分析表明 ,与模拟试验的结果一样 ,自然大气 CO2 浓度对气孔导度的影响并不是一成不变 ,这可能与植物本身的生物学特性和外界环境因素有关 .上述结果表明 ,实验室短期模拟的结果基本上适用于植物长期对环境变化的响应 ,但使用古化石植物气孔指数来重建过去大气 CO2

Responses of stomatal conductance of a natural tree for the past 240 years to changes of atmospheric CO 2 concentration were studied using tree ring stable carbon isotope series. Increases in the difference between the CO 2 concentration in the atmosphere and leaf intercellular( c a -c i ) and the ratios of ring area to c a -c i (G) were found. related to increasing atmospheric CO 2 concentration. Before 1900, increasing c a -c i was mainly associated with enhanced mesophyll capacity, after 1900 decrease in stomatal conductance led primarily to increase in c a -c i ; while increase in G possible meaned the change of the fixed carbon partitioning under increasingly elevated CO 2 concentration. The further analysis showed that response of stomatal conductance to CO 2 was highly variable, possibly by plant biological characteristics and other environmental factors, such as light and plant hormone. Based on the above results, it was proposed that determining palaeoatmospheric CO 2 concentration using fossil leaf material must be cautious.