氮、磷添加对不同种植密度樟树幼苗碳储量及其分配的影响

【目的】对氮(N)、磷(P)添加条件下4种种植密度的樟树Cinnamomum camphora幼苗各器官碳(C)含量、储量和分配比例进行研究,以期为氮沉降和磷添加背景下森林碳储量分配格局的变化提供参考。【方法】以1年生樟树幼苗为试验材料,选择氯化铵(NH4Cl)作为氮肥模拟氮沉降,以二水合磷酸二氢钠(NaH_2PO_4·2H_2O)作为磷添加,设置4个水平:不加N和P(对照,CK),加N,加P,加N和P(N+P)。N、P及N+P每年的添加量分别为NH4Cl40 g·m-2、NaH_2PO_4·2H2O 20 g·m~(-2)和NH4Cl 40 g·m~(-2)+NaH_2PO_4·2H_2O 20 g·m~(-2);种植密度设置4个水平,即10、20、40和80株·m-2。【结果】各氮、磷添加和密度处理下幼苗的根、茎和枝的C含量基本上差异不显著,而添加N和N+P能够促使樟树幼苗叶的C含量上升。随着种植密度的增大,樟树幼苗叶片C含量表现出下降的趋势;N、P添加处理基本上能够促进幼苗单株C储量和单位面积C储量的增加;随着种植密度的增大,单株幼苗C储量呈现下降的趋势。【结论】樟树幼苗叶的单株C储量和单位面积C储量分配比例随着种植密度的增大逐渐减小。高密度种植有利于茎的分配比例增加。N+P添加处理对幼苗C储量的促进效果大于单一N或P添加处理。

Effects of nitrogen and phosphorus additions on carbon storage and allocation of Cinnamomum camphora seedlings under different planting densities

Objective To study carbon (C) content, storage and allocation in seedling organs of Cinnamomum camphora cultivated in four different densities under nitrogen (N) and phosphorus (P) additions, and provide information for forest C storage and allocation under the background of N deposition and P addition.Method The 1-year-old C. camphora seedlings were used as test materials. NH₄Cl and NaH₂PO₄·2H₂O were selected to simulate atmospheric N deposition and P addition, respectively. N and P additions were performed with four different levels (control, N, P, and N+P). The N and P addition amounts per year in N, P, and N+P treatments were 40 g·m^-2 NH₄Cl, 20 g·m^-2 NaH₂PO₄·2H₂O and 40 g·m^-2 NH₄Cl + 20 g·m^-2 NaH₂PO₄·2H₂O, respectively. Seedlings were planted in four different densities (10, 20, 40 and 80 seedlings·m^-2).Result C contents in roots, stems and branches of seedlings in all treatments had no significant difference. N and N+P treatments increased C content of leaves. With the increase of planting density, C content of leaves tended to decrease. The N and P additions increased C storage per seedling and C storage in unit area. C storage per seedling decreased with the increase of planting density.Conclusion C storage of leaves per seedling and C storage in unit area decreases with the increase of planting density. C storage percentage of stems increases in high cultivation density treatment. The effect of N+P treatment on C storage per seedling and C storage in unit area is greater than that of single N or P addition.