不同土壤深度落叶松细根分解及N动态变化

Fine root decomposition and N dynamics of Larix gmelinii at different soil depths

细根分解受根序和土壤深度的潜在影响。使用根序法分根,将落叶松Larix gmelini根系分为两类:一级根、二级根为一类(1-2级根),即低级根;三级根和四级跟为另一类(3-4级根),即高级根。采用埋袋法对落叶松低级根和高级根在不同土壤深度(0-10、10-20 cm和20-30 cm)进行了为期862 d的分解实验,探讨不同根序细根分解规律,养分释放及其影响。结果表明:1-2级根的分解速率比3-4级分解速率慢,这种规律同时存在于不同深度的土壤中。在空间上,低级根和高级根的分解速率均随土壤深度的增加而降低,高级根的降低趋势更明显。随着分解时间的进行,各个土层之间的分解率在低级根之间差异更大。细根分解过程中,落叶松不同根序养分的释放特征不同。N释放速率总体上随细根根序增加而增大,随土壤深度的增加而降低。

Fine root decomposition can be affected by root order and soil depth.Using a branch-order classification,we separated the fine root systems of Larix gmelinii into two classes:first-and second-order roots were combined into one lower order(1-2 order);third-and fourth-order roots were combined into another higher order(3-4 order).Using the litterbag method,we conducted an 862-day decomposition experiment of lower-order and higher-order roots at different depths(0-10,10-20,and 20-30 cm)to study decomposition and the nutrient dynamics of fine roots among different root branching orders.Our results showed that the decomposition rate of the 1-2 order was slower than that of the 3-4 order,and this pattern also held true at different soil depths.Spatially,the decomposition rate of both lower and higher roots decreased with increasing soil depth,and the decreasing trend in the higher roots was more obvious.With the process of decomposition,there were larger differences in the decomposition rates of each soil layer among the lower-order roots.The patterns of root nutrient release also varied depending on different stages of decomposition.In conclusion,the N release rate generally increased with root order,and decreased with increasing soil depth.