Carbon and water exchange over a temperate semi-arid shrubland during three years of contrasting precipitation and soil moisture patterns
Carbon and water exchange over a temperate semi-arid shrubland during three years of contrasting precipitation and soil moisture patterns
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DOI：
10.1016/j.agrformet.2016.07.007
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发表时间：
2016-11-15
影响因子：
6.2
通讯作者：
Peltola, Hell
中科院分区：
文献类型：
--
作者：
Jia, Xin;Zha, Tianshan;Peltola, Hell
水被认为是影响干旱地区生态系统碳交换的关键因素。然而，干旱和半干旱地区降水年际变化与生态系统生产力之间的关系仍有待澄清。基于涡度相关测量，研究了中国北方灌丛生态系统生产力在3年（2012-2014年）降水和土壤水分模式下的变化。2012-2014年，生态系统净生产量分别为77 +/- 10（+/-标准差）、-4 +/- 10和-22 +/- 5克/立方米（-2），表明从年度汇迅速转变为碳源。生态系统总生产量（GEP）、总生态系统呼吸量（TER）和蒸散量（ET）在三年中也有所下降。在春季土壤湿度较低的年份，年碳通量和水通量似乎受到抑制，从2012年到2014年急剧下降。GEP的下降幅度大于TER和ET，导致固碳能力和水利用效率降低（WUE = GEP/ET）。无论是年度还是生长季降水量都不能解释碳通量的逐年变化，而在我们的网站ET是一个更好的代理水可用于生态系统的碳交换每年的基础上。秋季土壤水分水平在冬季进行到第二年的春天，因此，可能会影响叶的速度，植物生长和碳吸收在早期到中期的生长季节。我们的结论是从仅仅三年的测量中得出的，因此是初步的。需要更长的时间序列，包括更广泛的降水和土壤水分条件，以确认或完善这些结论。我们的研究结果强调了降水时间和土壤水分携带在控制生态系统生产力的重要性。冬季变暖和秋季和冬季降水减少可能导致春季干旱，从而损害半干旱和干旱欧亚大陆灌木林和草原生态系统的碳固存潜力。(C)2016爱思唯尔B. V.保留所有权利。
Water is considered a key factor affecting ecosystem carbon exchange in dryland regions. However, the relationship between inter-annual variations in precipitation and ecosystem productivity remains to be clarified for arid and semi-arid areas. Based on eddy-covariance measurements, we examined how ecosystem production in a shrubland of northern China varied over three years (2012-2014) with contrasting precipitation and soil moisture patterns. Net ecosystem production (NEP) was 77 +/- 10 (+/- standard deviation), -4 +/- 10 and -22 +/- 5 g C m(-2) in 2012-2014, respectively, indicating a rapid shift from an annual sink to a source of carbon. Gross ecosystem production (GEP), total ecosystem respiration (TER) and evapotranspiration (ET) also declined over the three years. Annual carbon and water fluxes appeared to be suppressed in years with low spring soil moisture, which declined dramatically from 2012 to 2014. GEP declined more than TER and ET, leading to reduced carbon sequestration capacity and water use efficiency (WUE = GEP/ET). Neither annual nor growing-season precipitation could explain the year-to-year variations in carbon fluxes, whereas at our site ET was a better proxy for water available to ecosystem carbon exchange on an annual basis. Autumn soil moisture levels were carried over winter to the following spring, and, thus, may affect the rates of leafout, plant growth and carbon uptake in the early to mid-growing season. Our conclusions were drawn from only three years of measurements and are therefore preliminary. Longer timeseries encompassing a wider range of precipitation and soil moisture conditions are needed to confirm or refine these conclusions. Our findings highlight the importance of precipitation timing and soil moisture carry-over in controlling ecosystem productivity. Winter warming and decreases in autumn and winter precipitation may induce spring drought and thus impair the carbon sequestration potential of shrubland and steppe ecosystems in semi-arid and arid Eurasia. (C) 2016 Elsevier B.V. All rights reserved.