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

用碱溶法测定了柳杉幼林矿物土层的二氧化碳释放量。CO_2释放量随土壤温度的变化呈季节性变化，约为Q_(10)值的2.2。不同测点的CO_2释放量差异较大，不同测点矿质土层的根系生物量和根系组成及其直径对CO_2释放量影响较大。线性多元回归模型R=a_0+a_1w_1+a_2w_2+a_3w_3，可以很好地将土壤和根系的CO_2释放总量(R)进行划分。式中的w_1至w_3代表不同径级的根重。研究了三种针叶树种赤松、落叶松和柳杉幼苗根系呼吸与地上器官生长和呼吸的关系。各物种在不同生长阶段的地上和地下呼吸之间存在线性关系。回归线的斜率，即地上呼吸与地下呼吸的比率，在日本是显著较高的，而在密花中国则较低。这些差异被认为是由于根组织内部发育的特殊性质造成的。虽然还需要更多的工作来澄清在个体生长较发达的阶段观察到的简单关系，但这里的结果对研究更好的林分水平地下呼吸估计方法是非常有启发的。

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.