Tuittila Eeva-Stiina, Komulainen Veli-Matti, Vasander Harri, Laine Jukka
Department of Forest Ecology, P.O. Box 24, FIN-00014, University of Helsinki, Finland e-mail:
Oecologia. 1999 Sep;120(4):563-574. doi: 10.1007/s004420050891.
In a field study, we examined the relationship between vegetation, abiotic factors and the CO exchange dynamics of a cut-away peatland 20 years after production had ended. The main objective was to determine the effect of rewetting on the CO exchange dynamics, measured separately in Eriophorum vaginatum tussocks and intertussocks (almost non-vegetated surfaces) using closed-chamber techniques, one growing season before and three growing seasons after the rewetting treatment. Rewetting lowered total respiration (R ) and increased gross photosynthesis (P ), which resulted in a higher incorporation of CO into the system. The seasonal CO balance for the almost continuously submerged section of the rewetted site became positive 2 years after rewetting (9.1 g CO-C m), and it was still higher in the 3rd year (64.5 g CO-C m), i.e. the system accumulated carbon. In the driest section of the rewetted site the seasonal balance increased strongly, but the balance was still negative during the 3 years following rewetting with losses from the system of 44.1, 26.1, 38.3 g CO-C m in 1995, 1996 and 1997 respectively. At the control site seasonal balance during 1995-1997 varied between ecosystem C losses of 41.8 and 95.3 in an area with high Eriophorum cover and between 52.1 and 109.9 g CO-C m with lower cover. Simulation of a cut-away peatland with dense Eriophorum vegetation (Eriophorum cover 70%) showed that if the water level (WT) is low, the seasonal CO balance of the ecosystem can reach the compensation point of no net C change (P = R ) only if weather conditions are favourable, but with a high WT the seasonal CO balance would be positive even under varying weather conditions. It can be concluded that with dense Eriophorum vegetation a restored cut-away peatland acts as a functional mire and becomes a sink for atmospheric CO.
在一项实地研究中，我们考察了生产结束20年后，植被、非生物因素与一块被开垦泥炭地的CO交换动态之间的关系。主要目的是确定重新湿润对CO交换动态的影响，在重新湿润处理前的一个生长季和处理后的三个生长季，使用封闭箱技术分别在羊胡子草草丛和草丛间（几乎无植被覆盖的表面）测量CO交换动态。重新湿润降低了总呼吸作用（R），增加了总光合作用（P），这导致更多的CO被纳入该系统。重新湿润地块几乎持续被淹没的部分，其季节性CO平衡在重新湿润2年后变为正值（9.1 g CO₂-C m⁻²），在第3年仍然较高（64.5 g CO₂-C m⁻²），即该系统积累了碳。在重新湿润地块最干燥的部分，季节性平衡大幅增加，但在重新湿润后的3年里，平衡仍为负值，1995年、1996年和1997年该系统的损失分别为44.1、26.1、38.3 g CO₂-C m⁻²。在对照地块，1995 - 1997年期间，在羊胡子草覆盖率高的区域，生态系统碳损失在41.8至95.3之间变化，在覆盖率较低的区域则在52.1至109.9 g CO₂-C m⁻²之间变化。对羊胡子草植被密集（羊胡子草覆盖率70%）的被开垦泥炭地进行模拟显示，如果水位（WT）较低，只有在天气条件有利时，生态系统的季节性CO平衡才能达到无净碳变化的补偿点（P = R），但如果水位较高，即使在不同天气条件下，季节性CO平衡也将为正值。可以得出结论，对于植被密集的羊胡子草来说，恢复后的被开垦泥炭地起到了功能性泥炭沼泽的作用，并成为大气CO₂的汇。
