Tundra carbon balance under varying temperature and moisture regimes
Tundra carbon balance under varying temperature and moisture regimes
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DOI：
10.1029/2009jg001237
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发表时间：
2010-07-22
影响因子：
3.7
通讯作者：
Oechel, W. C.
中科院分区：
文献类型：
--
作者：
Huemmrich, K. F.;Kinoshita, G.;Oechel, W. C.
为了了解环境变化对冻土带碳平衡的影响，在美国阿拉斯加州巴罗附近的湿莎草冻土带进行了一项操纵实验。对照、加热、升高或降低地下水位、随升高或降低地下水位同时加热6种环境处理进行3个重复。在2001年的生长季节，使用便携式室测量了6天的碳通量。还收集了光谱反射率和气象测量数据。基于通量测量建立了生态系统日总生产（GEP）和生态系统呼吸（Re）的经验模型。植物吸收的光合有效辐射量与GEP密切相关。这种关系不受生长季节处理或时间的影响。Re与土壤温度相关，但不同水位处理的关系不同。低水位处理的Re对温度变化的响应较强，而高水位处理的Re对温度变化的响应较小。这些模型计算了生长季节所有处理的每日净生态系统交换。变暖增加了季节性碳的增加和碳的损失。到夏末，降低地下水位的处理，无论是加热的还是不加热的，都是净碳源，而所有其他处理都是汇。升温和/或提高地下水位增加了净汇的强度。在这个实验的时间尺度上，地下水位主要决定了生态系统是源还是汇，温度改变了源或汇的强度。
To understand the effects of environmental change on tundra carbon balance, a manipulation experiment was performed in wet sedge tundra near Barrow, Alaska. Three replicates of six environmental treatments were made: control, heating, raising or lowering water table, and heating along with raising or lowering water table. Carbon fluxes were measured using a portable chamber for six days during the 2001 growing season. Spectral reflectance and meteorological measurements were also collected. Empirical models derived from flux measurements were developed for daily gross ecosystem production (GEP) and ecosystem respiration (Re). The amount of photosynthetically active radiation absorbed by the plants was strongly correlated with GEP. This relationship was not affected by treatment or time during the growing season. Re was related to soil temperature with a different relationship for each water level treatment. Re in the lowered water table treatment had a strong response to temperature changes, while the raised water table treatment showed little temperature response. These models calculated daily net ecosystem exchange for all of the treatments over the growing season. Warming increased both the seasonal carbon gain and carbon loss. By the end of summer the lowered water table treatments, both heated and unheated, were net carbon sources while all other treatments were sinks. Warming and/or raising the water table increased the strength of the net sink. Over the timescale of this experiment, water table primarily determined whether the ecosystem was a source or sink, with temperature modifying the strength of the source or sink.