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Carbon dioxide flux measurements from a coastal Douglas-fir forest floor.

机译：来自沿海道格拉斯冷杉森林地面的二氧化碳通量测量值。

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摘要

Soils can store large quantities of carbon in the form of decaying organic matter originally derived from vegetation. In order to gain a better understanding of the importance of soils in the carbon cycle, it is necessary to examine processes that directly affect the exchange of carbon between the soil and the atmosphere. During the year 2000, measurements of forest floor CO 2 flux and below-ground CO2 storage were obtained beneath the canopy of a 33-m tall coastal temperate Douglas-fir forest. The study took place at a micrometeorological tower flux site in operation since late 1997 obtaining year-round eddy covariance (EC) measurements of above-canopy CO2 and energy fluxes. An automated soil chamber system was designed and constructed which could obtain half hourly measurements of CO2 flux from six locations with each chamber covering 0.2 m2. These soil chambers were installed in late April and operated until mid-December, spanning a large portion of the growing season. EC measurements of CO 2 flux 2.6 m above the forest floor over a two month period in the late summer and early autumn were obtained to compare the two measurement techniques. Below-ground CO2 mixing ratios of soil air were measured periodically at six depths between 0.02 to 1 m using gas diffusion probes and a simple syringe sampling technique.; Maximum CO2 fluxes measured by the soil chambers varied by a factor of three, with two of the chambers measuring up to 16 μmol m −2 s−1 during the warmest times of the year, indicating high spatial variability in soil CO2 flux. Forest floor CO2 fluxes measured by each of the chambers showed different sensitivities to soil temperature and there was clear evidence of hysteresis in the flux-temperature relationship over the year. Due to the very low windspeeds below the forest canopy, reliable below-canopy EC measurements of forest floor CO2 flux were very difficult to obtain. Measurements of below-ground CO2 mixing ratio revealed that the amount of CO2 present in the soil increased rapidly with depth near the surface and increased less rapidly deeper in the soil. Using estimated values of the CO2 diffusivity and measured fluxes as inputs into a simple model, it appears that about 50% of the CO2 produced below-ground comes from between the soil surface and the 0.15 m depth. Results from this study suggests that CO2 fluxes from this forest floor are large compared to other, less productive ecosystems.
机译：土壤会以最初源自植被的腐烂有机物的形式储存大量碳。为了更好地了解土壤在碳循环中的重要性，有必要研究直接影响土壤与大气之间碳交换的过程。在2000年期间，在33米高的沿海温带花旗松杉木林冠层下获得了林底CO 2 通量和地下CO 2 储量的测量值。 。该研究自1997年底开始在微气象塔通量站点进行，获得了全年冠层以上CO 2 和能量通量的涡度协方差（EC）测量。设计并构建了一个自动土壤室系统，该系统可以从六个位置获得每小时半小时的CO 2 通量测量值，每个室覆盖0.2 m 2 。这些土室于4月下旬安装，并运行至12月中旬，跨越了整个生长季节的大部分时间。在夏末和初秋的两个月内，对林层以上2.6 m的CO 2 通量进行EC测量，从而比较了这两种测量技术。使用气体扩散探头和简单的注射器采样技术，在0.02至1 m的六个深度处定期测量地下空气的地下CO 2 混合比。土壤室测得的最大CO 2 通量变化三倍，其中两个室测得的最大16μmolm -2 s -1 < / super>在一年中最暖的时候，表明土壤CO 2 通量的空间变异性很大。每个室测得的林地CO 2 通量对土壤温度的敏感性不同，并且有明显的证据表明通量-温度关系在一年中存在滞后现象。由于林冠下的风速非常低，因此很难获得可靠的林下CO 2 通量的林下EC测量值。对地下CO 2 混合比的测量表明，土壤中存在的CO 2 的数量随地表深度的增加而迅速增加，而在土壤深处的增加则较慢。使用CO 2 扩散率的估计值和测得的通量作为简单模型的输入，看来地下产生的CO 2 约有50％来自于地下土壤表面和0.15 m的深度。这项研究的结果表明，与其他生产力较低的生态系统相比，该林地的CO 2 通量较大。

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  • 作者

    Drewitt, Gordon Bruce.;

  • 作者单位

    The University of British Columbia (Canada).;

  • 授予单位 The University of British Columbia (Canada).;
  • 学科 Agriculture Forestry and Wildlife.; Biogeochemistry.
  • 学位 Ph.D.
  • 年度 2002
  • 页码 167 p.
  • 总页数 167
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 森林生物学;生物地球化学、气体地球化学;
  • 关键词

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