Variation in sugar maple root respiration with root diameter and soil depth.
Variation in sugar maple root respiration with root diameter and soil depth.
复制标题
DOI：
10.1093/treephys/18.10.665
复制
发表时间：
1998-10
期刊：
影响因子：
4
通讯作者：
K. Pregitzer;M. Laskowski;A. Burton;Veronica C. Lessard;D. Zak
中科院分区：
文献类型：
--
作者：
K. Pregitzer;M. Laskowski;A. Burton;Veronica C. Lessard;D. Zak
根系呼吸可占土壤总呼吸的60%之多。因此，调节根部和相关微生物代谢活动的因素是陆地碳预算的重要组成部分。根系通常按直径和深度类别进行采样，以便研究人员能够系统、及时地处理样本。我们最近发现，根系远端的小侧根比较大的根具有更高的组织氮浓度，这导致了这样的假设：最小的根比较大的根具有显着更高的呼吸速率。本研究旨在确定根呼吸是否与根直径或根在土壤剖面中的位置有关。我们研究了密歇根州两片糖枫（Acer saccharum Marsh.）森林中三个土壤深度的四个直径等级的根呼吸速率和氮浓度之间的关系。根呼吸随着根直径的增加而下降，并且在更深的土壤深度处比在土壤表面处更低。表层根（0-10 厘米深）的呼吸速率比深层根高 40%，直径 < 0.5 毫米的根的呼吸速率比直径较大的根高 2.4 至 3.4 倍。根氮浓度解释了观察到的不同地点、大小和深度类别的呼吸变化的 70%。根直径类别和土壤深度之间的呼吸差异似乎与根功能变化对代谢活动的假设影响一致。在根系中，营养丰富的地区的细根具有最高的呼吸速率。大根和来自低养分利用率深度的根具有低呼吸速率，这与结构和运输功能一致，而不是与主动的养分吸收和同化一致。这些结果表明，广泛定义的根类别（例如，细根相当于所有直径 < 2.0 mm 的根）并不能准确反映通常与细根相关的功能类别。组织氮浓度或氮含量（质量 x 浓度 N）可能是比根直径更好的根功能指标。
Root respiration may account for as much as 60% of total soil respiration. Therefore, factors that regulate the metabolic activity of roots and associated microbes are an important component of terrestrial carbon budgets. Root systems are often sampled by diameter and depth classes to enable researchers to process samples in a systematic and timely fashion. We recently discovered that small, lateral roots at the distal end of the root system have much greater tissue N concentrations than larger roots, and this led to the hypothesis that the smallest roots have significantly higher rates of respiration than larger roots. This study was designed to determine if root respiration is related to root diameter or the location of roots in the soil profile. We examined relationships among root respiration rates and N concentration in four diameter classes from three soil depths in two sugar maple (Acer saccharum Marsh.) forests in Michigan. Root respiration declined as root diameter increased and was lower at deeper soil depths than at the soil surface. Surface roots (0-10 cm depth) respired at rates up to 40% greater than deeper roots, and respiration rates for roots < 0.5 mm in diameter were 2.4 to 3.4 times higher than those for roots in larger diameter classes. Root N concentration explained 70% of the observed variation in respiration across sites and size and depth classes. Differences in respiration among root diameter classes and soil depths appeared to be consistent with hypothesized effects of variation in root function on metabolic activity. Among roots, very fine roots in zones of high nutrient availability had the highest respiration rates. Large roots and roots from depths of low nutrient availability had low respiration rates consistent with structural and transport functions rather than with active nutrient uptake and assimilation. These results suggest that broadly defined root classes, e.g., fine roots are equivalent to all roots < 2.0 mm in diameter, do not accurately reflect the functional categories typically associated with fine roots. Tissue N concentration or N content (mass x concentration N) may be a better indicator of root function than root diameter.