植物篱枝叶有机碳分解研究

研究植物篱枝叶的分解和养分矿化过程对该模式下养分的有效利用具有重要意义。在金沙江干热河谷坡耕地上利用分解袋法对新银合欢、山蚂蝗等 6个植物篱树种枝叶的分解进行了研究 ,结果显示山蚂蝗和新银合欢分解最快 ,前 2个星期有机碳分解了48 6 %和 5 0 0 % ;山毛豆和云南合欢次之 ,前 4星期有机碳累积分解量为 5 1 5 %和 45 6 % ;圣诞树和黑荆树分解最慢 ;将枝叶埋入土壤中比覆盖地表分解快。有机碳的分解规律可以用单指数模型Ct=C0 (1 e kt)和双指数模型Ct=C0 1 (1 e k1t) C0 2 (1 e k2 t)拟合 (式中 ,Ct 为有机碳累积分解量占全碳百分数 ,C0 、C0 1 和C0 2 分别为易分解有机碳和难分解有机碳百分数 ,k和k1分别为易分解有机碳分解常数 ,k2 为难分解有机碳分解常数 ) ,双指数模型更具合理性。研究表明有机碳的累积分解量与枝叶初始C/N比呈负相关 ,枝叶分解速度可用有机碳 (或易分解有机碳 )半减期来衡量。

ORGANIC CARBON DECOMPOSITION PATTERNS OF HEDGEROW PRUNINGS UNDER CONTOUR HEDGEROW SYSTEM

Contour hedgerow system has been promoted for soil conservation and soil fertility improvement through the use of prunings for the system as mulch green manure However, decomposition process of organic C in the prunings is a key factor affecting nutrient release of prunings Organic C decomposition of prunings from six species of hedgerows was studied by the litterbag method The results indicated that most of the decomposable organic C decomposed within the first 2 weeks in the prunings from Desmodium rensonii and Leucaena leucocephala, within 4 weeks from Tephrosia candida and Aldizia yunnanensis, and more than 8 weeks from Acacia dealbata and A cacia mearnsii, Organic C of prunings incorporated into soil decomposed faster than that used as mulch Cumulative percentage of decomposed organic C could be fitted well by exponent models C_t=C₀(1-e^-kt) or C_t=C₀₁(1-e^-k₁t)+₀₂(1-e^-k₂t) (where C_t represents organic C by time t, C₀ and C₀₁ represent the decomposable fractions of organic C, C₀₂ is the resistant fraction of organic C in the prunings, and k, k₁ and k₂ are the rate constants of C₀, C₀₁ and C₀₂, respectively), and the latter model seems to be more reasonable. The results also indicated that initial C/N ratio was negatively correlated with percentage of C decomposed during the first 12 weeks. Itwas recommended that half life of prunings organic C could be used as a criterion for their nutrient availability to crops in short period under contour hedgerow intercropping.