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1.
Sanna Saarnio Sanna Järviö Timo Saarinen Harri Vasander Jouko Silvola 《Ecosystems》2003,6(1):0046-0060
Increasing concentrations of carbon dioxide (CO2) in the atmosphere or continuous nitrogen (N) deposition might alter the carbon (C) cycle in boreal mires and thus have significant
impacts on the development of climate change. The atmospheric impact of the C cycle in mires is twofold: C accumulation attenuates
and CH4 release strengthens the natural greenhouse effect. We studied the effects of an increased supply of CO2 or NH4NO3 on the vegetation and annual CO2 exchange in lawns of a boreal oligotrophic mire in eastern Finland over a 2-year period. Ten study plots were enclosed with
mini-FACE (Free Air Carbon Dioxide Enrichment) rings. Five plots were vented with CO2-enriched air (target 560 ppmv), while their controls were vented with ambient air; five plots were sprayed with NH4NO3, corresponding to a cumulative addition of 3 g N m−2 a−1, while their controls were sprayed with distilled water only. A raised NH4NO3 supply seemed to affect the composition of the moss layer. Raised CO2 did not affect the vegetation, but gross photosynthesis increased significantly. The change in net CO2 exchange depended on the annual weather conditions. Our results suggest that C accumulation may increase in wet years and
compensate for the warming effect caused by the increase in CH4 release from this mire. In contrast, a relatively dry and warm growing period favors decomposition and can even make the
CO2 balance negative. Along with the increased CH4 release under raised CO2, the decreased C accumulation then increases the radiative forcing of boreal mires.
Received 22 October 2001; accepted 13 May 2002. 相似文献
2.
This study examined the effects of season-long exposure of Chinese pine (Pinus tabulaeformis) to elevated carbon dioxide (CO2) and/or ozone (O3) on indole-3-acetic acid (IAA) content, activities of IAA oxidase (IAAO) and peroxidase (POD) in needles. Trees grown in
open-top chambers (OTC) were exposed to control (ambient O3, 55 nmol mol−1 + ambient CO2, 350 μmol mol−1, CK), elevated CO2 (ambient O3 + high CO2, 700 μmol mol−1, EC) and elevated O3 (high O3, 80 ± 8 nmol mol−1 + ambient CO2, EO) OTCs from 1 June to 30 September. Plants grown in elevated CO2 OTC had a growth increase of axial shoot and needle length, compared to control, by 20% and 10% respectively, while the growth
in elevated O3 OTC was 43% and 7% less respectively, than control. An increase in IAA content and POD activity and decrease in IAAO activity
were observed in trees exposed to elevated CO2 concentration compared with control. Elevated O3 decreased IAA content and had no significant effect on IAAO activity, but significantly increased POD activity. When trees
pre-exposed to elevated CO2 were transferred to elevated O3 (EC–EO) or trees pre-exposed to elevated O3 were transferred to elevated CO2 (EO–EC), IAA content was lower while IAAO activity was higher than that transferred to CK (EC–CK or EO–CK), the change in
IAA content was also related to IAAO activity. The results indicated that IAAO and POD activities in Chinese pine needles
may be affected by the changes in the atmospheric environment, resulting in the change of IAA metabolism which in turn may
cause changes in Chinese pine’s growth.
An erratum to this article can be found at 相似文献