CO2 efflux, CO2 concentration and photosynthetic refixation in stems of Eucalyptus globulus (Labill.)
CO2 efflux, CO2 concentration and photosynthetic refixation in stems of Eucalyptus globulus (Labill.)
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DOI：
10.1093/jxb/ern272
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发表时间：
2009-01-01
影响因子：
6.9
通讯作者：
Teskey, R. O.
中科院分区：
文献类型：
--
作者：
Cerasoli, S.;McGuire, M. A.;Teskey, R. O.
尽管呼吸在森林碳预算中很重要，但生理因素控制茎呼吸的机制尚不清楚。在葡萄牙中部的一个蓝桉种植园进行了一项实验，该种植园采用 5 年树龄和 10 年树龄的单一栽培林。测量了遮荫和无遮荫条件下茎的 CO2 流出量，以及溶解在树液中的 CO2 浓度 [CO2*]、茎温度和树液流量，目的是加深我们对控制 E. globulus 茎 CO2 释放的因素的理解。与10年生茎相比，5年生茎的CO2流出量始终较高，平均分别为3.4和1.3μmol m(-2) s(-1)。温度和 [CO2*] 都对 CO2 从茎中流出的速率具有重要且相似的影响，但都无法解释不同年龄和大小的树木之间 CO2 流出量的差异。流出量和树液流之间没有发现任何关系，并且流出量与树木体积无关，这表明在该物种中，二氧化碳从木质部扩散到大气中存在重大障碍。两个年龄的树木的皮层光合作用速率相同，仅减少了 7% 的二氧化碳流出量，这可能是由于树冠下方茎表面的辐照度较低。年轻的树比老树的生长速度要快得多。年轻茎和老茎的二氧化碳流出量之间的差异似乎是由于生长呼吸的差异而不是木质部运输的二氧化碳扩散速率的差异造成的。
In spite of the importance of respiration in forest carbon budgets, the mechanisms by which physiological factors control stem respiration are unclear. An experiment was set up in a Eucalyptus globulus plantation in central Portugal with monoculture stands of 5-year-old and 10-year-old trees. CO2 efflux from stems under shaded and unshaded conditions, as well as the concentration of CO2 dissolved in sap [CO2*], stem temperature, and sap flow were measured with the objective of improving our understanding of the factors controlling CO2 release from stems of E. globulus. CO2 efflux was consistently higher in 5-year-old, compared with 10-year-old, stems, averaging 3.4 versus 1.3 mu mol m(-2) s(-1), respectively. Temperature and [CO2*] both had important, and similar, influences on the rate of CO2 efflux from the stems, but neither explained the difference in the magnitude of CO2 efflux between trees of different age and size. No relationship was found between efflux and sap flow, and efflux was independent of tree volume, suggesting the presence of substantial barriers to the diffusion of CO2 from the xylem to the atmosphere in this species. The rate of corticular photosynthesis was the same in trees of both ages and only reduced CO2 efflux by 7%, probably due to the low irradiance at the stem surface below the canopy. The younger trees were growing at a much faster rate than the older trees. The difference between CO2 efflux from the younger and older stems appears to have resulted from a difference in growth respiration rather than a difference in the rate of diffusion of xylem-transported CO2.