Deep Autotrophic Soil Respiration in Shrubland and Woodland Ecosystems in Central New Mexico
Deep Autotrophic Soil Respiration in Shrubland and Woodland Ecosystems in Central New Mexico
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DOI：
10.1007/s10021-011-9495-x
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发表时间：
2012-01-01
期刊：
影响因子：
3.7
通讯作者：
Litvak, M. E.
中科院分区：
文献类型：
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作者：
Breecker, D. O.;McFadden, L. D.;Litvak, M. E.
量化土壤呼吸的控制对于理解生态系统生理和预测土壤碳库对气候变化的响应具有重要意义。大多数土壤呼吸通常被认为发生在土壤顶部20-30厘米处。在沙漠土壤中，有机物浓度往往很低，植物扎根很深，可能会有更深的呼吸作用。然而，对旱地土壤呼吸的深度分布知之甚少。在这里，我们表明，脉冲降水事件之间的土壤呼吸的平均深度几乎总是大于20厘米，并经常大于50厘米，在两个中央新墨西哥州沙漠灌丛。松-杜松林地土壤呼吸平均深度较浅，在5 ~ 40 cm之间。在灌丛，8千分之一的季节变化，土壤呼吸的CO2（三角洲C-13（r-土壤））的碳同位素组成与蒸汽压赤字支持根/根际呼吸的土壤CO2的主要来源。这种深层的自养呼吸作用表明，当靠近地表的条件不利时，灌木优先将光合产物分配给深层根系。因此，在这些土壤中的呼吸速率不一定与根生物量。δ（13）Cr-土壤值没有提供土壤无机碳演化出CO2的证据。我们的研究结果还表明，有机碳循环是快速和有效的，在这些土壤和三角洲C-13值的CO2从土壤中呼吸在美国西南部的大部分地区，也许在其他半干旱地区，季节性变化至少千分之四。
Quantifying the controls on soil respiration is important for understanding ecosystem physiology and for predicting the response of soil carbon reservoirs to climate change. The majority of soil respiration is typically considered to occur in the top 20-30 cm of soils. In desert soils, where organic matter concentrations tend to be low and plants are deeply rooted, deeper respiration might be expected. However, little is known about the depth distribution of respiration in dryland soils. Here we show that the average depth of soil respiration between pulse precipitation events is almost always greater than 20 cm and is frequently greater than 50 cm in two central New Mexico desert shrublands. The average depth of soil respiration in a pinon-juniper woodland was shallower, between 5 and 40 cm. In the shrublands, 8 parts per thousand seasonal variations in the carbon isotope composition of soil-respired CO2 (delta C-13(r-soil)) that correlate with vapor pressure deficit support root/rhizosphere respiration as the dominant source of soil CO2. Such deep autotrophic respiration indicates that shrubs preferentially allocate photosynthate to deep roots when conditions near the surface are unfavorable. Therefore, respiration rates in these soils are not necessarily correlated with root biomass. The delta(13) Cr-soil values provide no evidence for CO2 evolved from soil inorganic carbon. Our results also suggest that organic carbon cycling is rapid and efficient in these soils and that the delta C-13 value of CO2 respired from soils in much of the southwestern US, and perhaps in other semiarid regions, varies seasonally by at least 4 parts per thousand.