Carbon flux in soil and plant-root compartments in the matter recycling system of secondary forests

采用碱液法测定了柳杉幼林矿质土层二氧化碳的释放量。CO_2释放量随土壤温度的波动呈季节变化，在2.2 Q_<10>附近。不同测点CO_2释放量差异较大，各测点矿质土层根系生物量和根系组成及其直径对co2释放量影响较大。利用线性多元回归模型R=a_0+a_1w_1+a_2w_2+a_3w_3，可以很好地将CO_2总释放量划分为矿质土和根系释放量。式中w_1到w_3表示不同直径类的根权值。估计根系呼吸量占总co2释放量的60%以上。以密松（Pinus densiflora）、leptolepis （Lalix leptolepis）和柳杉（Cryptomeria japonica） 3种针叶植物为研究对象，研究了根系呼吸与地上器官生长和呼吸的关系。各树种在不同生长阶段的地上呼吸和地下呼吸均呈线性关系。反映地上呼吸与地下呼吸比值的回归线梯度表明，粳稻的地上呼吸比显著增高，密草木的地上呼吸比显著降低。这些差异被认为是由于根组织内部发育的特定特性造成的。虽然还需要进一步的工作来澄清在个体生长的较发达阶段观察到的简单关系，但这里得到的结果对研究林分水平下地下呼吸的更好的估计方法非常有启发意义。

The carbon dioxide release from mineral soil layr was measured by using alkali solution in young Cryptomeria japonica stands. The CO_2 release changed seasonally in accordance with the fluctuation in soil temperature, being around 2.2 the Q_<10> values. The amount of CO_2 release largely differed with measurement places, where root biomass and root composition with its diameter in mineral soil layr at each place had a great influence. The linear multiple regression model, R=a_0+a_1w_1+a_2w_2+a_3w_3, was quite useful to divide the total CO_2 release (R) into those from mineral soil and root systems. Here w_1 to w_3 in the equation stand for root weights for different diameter classes. The respiratory amount by root system was estimated to occupy more than 60% of the total CO_2 release.The respiration by root system was investigated in relation to growth and respiration of the above-ground organs in seedings of three coniferous species, Pinus densiflora, Lalix leptolepis, and Cryptomeria japonica. The linear relationship was recognized in each species between above-ground and under-ground respirations through various growth stages. Gradient of the regression line, implying ratio of above-ground respiration against under-ground one, was significantly higher in C.japonica and lower inP.densiflora. These differences were considered to result from specific properties with respect to internal development of root tissues. Although additional works are needed to clarify that simple relationships are observed in more developed stages in individual growth, the results obtained here are very suggestive in examining much better estimation methods of the under-ground respiration in forest stand level.