Gonsamo, Alemu等：Changes in vegetation phenology are not reflected in atmospheric CO2 and C-13/C-12 seasonality

Changes in vegetation phenology are not reflected in atmospheric CO2 and C-13/C-12 seasonality

作者:Gonsamo, A (Gonsamo, Alemu)[ 1,2 ] ; D'Odorico, P (D'Odorico, Petra)[ 3 ] ; Chen, JM (Chen, Jing M.)[ 2 ] ; Wu, CY (Wu, Chaoyang)[ 1 ] ; Buchmann, N (Buchmann, Nina)[ 3 ]

GLOBAL CHANGE BIOLOGY

卷: 23  期: 10  页: 4029-4044

DOI: 10.1111/gcb.13646

出版年: OCT 2017

摘要

Northern terrestrial ecosystems have shown global warming-induced advances in start, delays in end, and thus increased lengths of growing season and gross photosynthesis in recent decades. The tradeoffs between seasonal dynamics of two opposing fluxes, CO2 uptake through photosynthesis and release through respiration, determine the influence of the terrestrial ecosystem on the atmospheric CO2 and C-13/C-12 seasonality. Here, we use four CO2 observation stations in the Northern Hemisphere, namely Alert, La Jolla, Point Barrow, and Mauna Loa Observatory, to determine how changes in vegetation productivity and phenology, respiration, and air temperature affect both the atmospheric CO2 and C-13/C-12 seasonality. Since the 1960s, the only significant long-term trend of CO2 and C-13/C-12 seasonality was observed at the northern most station, Alert, where the spring CO2 drawdown dates advanced by 0.65 +/- 0.55 days yr(-1), contributing to a nonsignificant increase in length of the CO2 uptake period (0.74 +/- 0.67 days yr(-1)). For Point Barrow station, vegetation phenology changes in well-watered ecosystems such as the Canadian and western Siberian wetlands contributed the most to C-13/C-12 seasonality while the CO2 seasonality was primarily linked to nontree vegetation. Our results indicate significant increase in the Northern Hemisphere soil respiration. This means, increased respiration of C-13 depleted plant materials cancels out the C-12 gain from enhanced vegetation activities during the start and end of growing season. These findings suggest therefore that parallel warming-induced increases both in photosynthesis and respiration contribute to the long-term stability of CO2 and C-13/C-12 seasonality under changing climate and vegetation activity. The summer photosynthesis and the soil respiration in the dormant seasons have become more vigorous which lead to increased peak-to-through CO2 amplitude. As the relative magnitude of the increased photosynthesis in summer months is more than the increased respiration in dormant months, we have the increased overall carbon uptake rates in the northern ecosystems.

通讯作者地址: Gonsamo, A (通讯作者)

Chinese Acad Sci, Inst Remote Sensing & Digital Earth, State Key Lab Remote Sensing Sci, Beijing 100101, Peoples R China.

通讯作者地址: Gonsamo, A (通讯作者)

Univ Toronto, Dept Geog & Planning, Toronto, ON M5S 3G3, Canada.

地址:

[ 1 ] Chinese Acad Sci, Inst Remote Sensing & Digital Earth, State Key Lab Remote Sensing Sci, Beijing 100101, Peoples R China

[ 2 ] Univ Toronto, Dept Geog & Planning, Toronto, ON M5S 3G3, Canada

[ 3 ] Swiss Fed Inst Technol Zurich, Inst Agr Sci, CH-8092 Zurich, Switzerland