Wang Kai-Yun, Kellomäki Seppo, Zha Tianshan, Peltola Heli
Chengdu Institute of Biology, the Chinese Academy of Sciences, PO Box 406, Chengdu 610041, PR China.
J Exp Bot. 2005 Jan;56(409):155-65. doi: 10.1093/jxb/eri013. Epub 2004 Nov 8.
Measurements of sap flow, crown structure, and microclimate were used to estimate the transpiration of individual 30-year-old Pinus sylvestris L. trees grown in elevated temperature and CO2. The trees were enclosed in closed-top chambers and exposed either to current ambient conditions (CON), or elevated CO2 (+350 micromol mol(-1); EC), or elevated temperature (+2 to +6 degrees C; ET) or a combination of EC and ET (ECT) since 1996, and the measurements were made from 1999 to 2001. EC significantly increased annual sap flow per tree (Ft.m) by 14% in 1999, but reduced it by 13% in 2000 and 16% in 2001. The CO2-induced increase in Ft.m in 1999 was due to a large increase in foliage area of trees, which more than compensated for a small decrease in crown conductance (Gc). The CO2-induced decreases in Ft.m in 2000 and 2001 resulted from a pronounced decline in Gc, which was much greater than the increase in foliage area. The CO2-induced increase in sensitivity of Gc at high vapour pressure deficit (VPD) did not alter the general response of sap flow to CO2 enrichment, but it did affect the diurnal courses of sap flow on some days during the main growing season (days 150-240). ET increased Ft.m by 53%, 45%, and 57% in 1999, 2000, and 2001, respectively, attributable to the combined effects of greater foliage area and maximum crown conductance, lower stomatal sensitivity to high VPD, and higher transpiration demand relative to the control treatments. There was no significant interaction between CO2 and temperature on sap flow, because ECT entailed approximately similar patterns of sap flow to ET, suggesting that the temperature played a dominate role in the case of ECT under boreal climate conditions.
通过测量液流、树冠结构和微气候来估算生长在温度和二氧化碳浓度升高环境下的30年生欧洲赤松个体的蒸腾作用。自1996年起，将这些树木置于封闭顶式气室中，使其暴露于当前的环境条件（CON）、二氧化碳浓度升高（+350微摩尔/摩尔；EC）、温度升高（+2至+6摄氏度；ET）或EC与ET的组合（ECT）环境中，并于1999年至2001年进行测量。1999年，EC使每棵树的年液流量（Ft.m）显著增加了14%，但在2000年降低了13%，在2001年降低了16%。1999年二氧化碳诱导的Ft.m增加是由于树木叶面积大幅增加，这弥补了树冠导度（Gc）的小幅下降。2000年和2001年二氧化碳诱导的Ft.m下降是由于Gc显著下降，其下降幅度远大于叶面积的增加。在高水汽压差（VPD）下，二氧化碳诱导的Gc敏感性增加并未改变液流对二氧化碳富集的总体响应，但确实影响了主要生长季节某些日子（第150 - 240天）的液流日变化过程。1999年、2000年和2001年，ET分别使Ft.m增加了53%、45%和57%，这归因于叶面积和最大树冠导度增加、气孔对高VPD的敏感性降低以及相对于对照处理更高的蒸腾需求的综合作用。二氧化碳和温度对液流没有显著的交互作用，因为ECT的液流模式与ET大致相似，这表明在北方气候条件下，对于ECT而言，温度起主导作用。
