Effects of extended growing season and soil warming on carbon dioxide and methane exchange of tussock tundra in Alaska
Effects of extended growing season and soil warming on carbon dioxide and methane exchange of tussock tundra in Alaska
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DOI：
10.1029/98jd00522
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发表时间：
1998-11
影响因子：
--
通讯作者：
S. Oberbauer;G. Starr;Eric W. Pop
中科院分区：
文献类型：
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作者：
S. Oberbauer;G. Starr;Eric W. Pop
在1995年和1996年两个生长季中，通过早期除雪和后期防止积雪的方法延长了苔原的活跃期，以检验生长季延长对冻原碳交换的影响。建立了延长季节、延长季节+土壤增温和对照3种处理。土壤升温是通过在处理开始前一年安装的冷框架、电阻加热丝来完成的。采用封闭室红外气体分析技术，每周测量CO2交换的日变化过程。甲烷通量每一季测量两到三次，也采用封闭方法。1995年融雪发生异常早，除雪处理仅使季节延长了9-10天。1996年，早期季节增加了大约24天。正如预期的那样，延长季节和延长季节+土壤加热样地的解冻深度、土壤温度和植物生长都更早。两个季节的甲烷通量都较低，但在延长季节和土壤加热样地有较高的趋势。在季节早期，各处理间的净生态系统CO2通量相似，除雪和警戒样地的净生态系统CO2通量（系统损失）趋向于正通量（系统损失），可能是由于较高的地下呼吸作用。在季节中期，不同处理之间的通量相似。在季节后期，延长季节和升温样地的通量往往比对照低（碳损失少），特别是在1995年。然而，在整个季节中，三种处理的通量在统计上没有差异，代表了大气的损失。1996年对暗呼吸的测量表明，延长季节样地的呼吸和吸收量都有所增加，导致净通量与对照相似。
The active season of tussock tundra was extended during two growing seasons (1995 and 1996) by snow removal in early season and prevention of snow accumulation in late season to test the effects of a longer growing season on tundra carbon exchange. Three treatments were established: extended season, extended season + soil warming, and controls. Soil warming was accomplished using cold-frame, resistance heating wire installed the year prior to the initiation of treatments. Diurnal courses of CO2 exchange were measured weekly using infrared gas analysis with enclosed chamber techniques. Methane fluxes were measured two to three times a season also using enclosure methods. In 1995, snowmelt occurred unusually early, and snow removal treatments increased the season only 9–10 days. In 1996 the early season was increased approximately 24 days. As expected, thaw depth, soil temperature, and plant growth were greater earlier in the extended season and extended season + soil heating plots. Methane fluxes in both seasons were low but tended to be higher in the extended season and soil heated plots. Net ecosystem CO2 fluxes were similar among treatments early in the season, with a tendency toward more positive fluxes (system loss) for the snow removal and wanned plots, possibly due to higher belowground respiration. During midseason, fluxes were similar among the treatments. Later in the season, fluxes of extended season and warmed plots tended to be lower (less carbon loss) than controls, especially in 1995. Totaled over the season, however, the fluxes of the three treatments did not statistically differ and represented losses to the atmosphere. Measurements of dark respiration in 1996 indicate that both respiration and uptake were increased on the extended season plots, resulting in similar net fluxes to controls.