Seasonal patterns of carbon dioxide and water fluxes in three representative tundra ecosystems in northern Alaska
Seasonal patterns of carbon dioxide and water fluxes in three representative tundra ecosystems in northern Alaska
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DOI：
10.1890/es11-00202.1
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发表时间：
2012-01-01
期刊：
影响因子：
2.7
通讯作者：
Shaver, G. R.
中科院分区：
文献类型：
--
作者：
Euskirchen, E. S.;Bret-Harte, M. S.;Shaver, G. R.
了解北极的二氧化碳和水通量对于准确评估和预测这些生态系统对气候变化的反应至关重要。在北极，由于在寒冷偏远地区进行这些测量的困难，使用微气象方法对净CO2，水和能量交换的研究相对较少。当进行这些测量时，它们通常只在短暂的夏季生长季节收集。我们建立了涡度协方差通量塔在三个代表阿拉斯加苔原生态系统（石南苔原，草丛苔原，湿莎草苔原），并收集了CO2，水，和能量通量数据连续三年（2007年9月至2011年5月）。在所有生态系统中，CO2吸收的峰值出现在7月，6月至8月期间的累积量为51-95 g C/m（2）。从CO2源汇在春季的开关的时间似乎是由本赛季初的生长度日数，表明温暖的春天可能会促进增加净CO2吸收。然而，如果呼吸没有受到大量降水或较低温度的阻碍，那么春季增加的吸收可能会因生长季节后期促进呼吸的气温升高而消失。在生长季节的净CO2积累通常是通过呼吸在9月至5月的积雪覆盖的几个月，把生态系统的净CO2源在测量期间。从6月到8月在三个生态系统的水平衡是可变的，与观察到的石楠苔原的变化最大，在草丛苔原最少。这些发现强调了在整个年度周期和多种类型的苔原生态系统中收集数据的重要性，以便更全面地了解北极的二氧化碳和水通量。
Understanding the carbon dioxide and water fluxes in the Arctic is essential for accurate assessment and prediction of the responses of these ecosystems to climate change. In the Arctic, there have been relatively few studies of net CO2, water, and energy exchange using micrometeorological methods due to the difficulty of performing these measurements in cold, remote regions. When these measurements are performed, they are usually collected only during the short summer growing season. We established eddy covariance flux towers in three representative Alaska tundra ecosystems (heath tundra, tussock tundra, and wet sedge tundra), and have collected CO2, water, and energy flux data continuously for over three years (September 2007-May 2011). In all ecosystems, peak CO2 uptake occurred during July, with accumulations of similar to 51-95 g C/m(2) during June-August. The timing of the switch from CO2 source to sink in the spring appears to be regulated by the number of growing degree days early in the season, indicating that warmer springs may promote increased net CO2 uptake. However, this increased uptake in the spring may be lost through warmer temperatures in the late growing season that promote respiration, if this respiration is not impeded by large amounts of precipitation or cooler temperatures. Net CO2 accumulation during the growing season was generally lost through respiration during the snow covered months of September-May, turning the ecosystems into net sources of CO2 over measurement period. The water balance from June to August at the three ecosystems was variable, with the most variability observed in the heath tundra, and the least in the tussock tundra. These findings underline the importance of collecting data over the full annual cycle and across multiple types of tundra ecosystems in order to come to a more complete understanding of CO2 and water fluxes in the Arctic.