Estimation of whole-stem respiration, incorporating vertical and seasonal variations in stem CO2 efflux rate, of Chamaecyparis obtusa trees
Estimation of whole-stem respiration, incorporating vertical and seasonal variations in stem CO2 efflux rate, of Chamaecyparis obtusa trees
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DOI：
10.1007/s10310-009-0163-3
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发表时间：
2010-04-01
影响因子：
1.5
通讯作者：
Chiba, Yukihiro
中科院分区：
文献类型：
--
作者：
Araki, Masatake G.;Utsugi, Hajime;Chiba, Yukihiro
研究了50年生日本柏树人工林树干呼吸速率的垂直变化和季节变化。Et Zucc.)Endl.，并讨论了一种实用而精确的方法，将点测量的树干二氧化碳流出速率扩展到整个树干呼吸。对于选定的五棵树，在连续两年中，每1或2个月测量一次胸高(1.3米)和胸高以上5或6个点(间隔约2米)的树干二氧化碳流出率。树冠内的日总树干呼吸速率(表面积)大于树冠下，尤其是在生长季节。通过结合呼吸速率的垂直剖面，估计了每棵样本树的年全干呼吸(R(Y))。然后，我们将这一估计值(R(Y))与另一种使用传统方法获得的全年全茎呼吸量(R‘(Y))进行了比较；假设胸高处的面积呼吸速率在整个茎干中是恒定的。这两个估计值的比值(R‘(Y)/R(Y))通常小于1，表明用于计算R’(Y)的假设低估了年全茎呼吸。研究发现，R‘(Y)/R(Y)与冠长与树高之比(冠比)呈负相关。这些结果表明，冠内呼吸活性较高的树干的相对比例对该人工林的年全干呼吸有很大的影响。在方法上，我们的结果表明，将冠幅比纳入常规方法将提高全年全茎呼吸估计的准确性。
We examined vertical and seasonal variations in stem respiration rates in a 50-year-old plantation of Japanese cypress, Chamaecyparis obtusa (Sieb. et Zucc.) Endl., in central Japan, and discuss a practical and precise method to scale a point-measured stem CO2 efflux rate up to whole-stem respiration. For five selected trees, stem CO2 efflux rates were measured at breast height (1.3 m) and at five or six points above breast height (at approximately 2 m intervals) every 1 or 2 months over two consecutive years. Daily total stem respiration rate (surface area basis) was greater inside the crown than below the crown, especially during the growing season. By incorporating the vertical profile of the respiration rate, annual whole-stem respiration was estimated for each sample tree (R (y)). We then compared this estimate (R (y)) with another estimate of annual whole-stem respiration (R'(y)) obtained using a conventional method; it is assumed that the area-based respiration rate at breast height is constant throughout the stem. The ratio of these two estimates (R'(y)/R (y)) was usually less than 1, indicating that the assumptions used to calculate R'(y) underestimate annual whole-stem respiration. We found that R'(y)/R (y) was negatively correlated with the ratio of crown length to tree height (crown ratio). These results suggest that annual whole-stem respiration in this C. obtusa plantation is substantially affected by the relative proportion of within-crown stem with higher respiratory activity. Methodologically, our results imply that incorporating the crown ratio into the conventional method would improve the accuracy of annual whole-stem respiration estimates.