作 者 ：李紫燕,李世清*,李生秀
期 刊 ：生态学报 2008年 28卷 10期 页码：4940~4950
Keywords:the Loess Plateau, soil N mineralization, non-exchangeable ammonium,
摘 要 ：以黄土高原从北向南不同地区典型土壤类为对象，采用Bremner淹水培养法，研究黄土高原典型土壤有机氮的矿化过程。结果表明，淹水培养期间矿化出的部分NH+4-N会被粘土矿物固定，固定量因土壤不同而异，因此在测定有机氮矿化量时，只有考虑这一部分氮素，才可获得可靠结果。不同土壤有机氮量矿化明显不同，表现为土垫旱耕人为土＞黄土正常新成土＞简育干润均腐土＞干润砂质新成土，从南到北氮素矿化量呈减小趋势。添加C/N低（C/N比为21.7）的紫花苜蓿（Medicago stativa）茎叶有利于促进土壤有机氮矿化，而添加C/N高（C/N比为43.3）的长芒草（Stipa bungeana）会促进矿质氮的生物固定；不同类型植被土壤间在培养20、40d和60d时的矿化量差异显著（p值分别为0.0177、0.0109和0.0073），均表现为均为林地土壤＞裸地土壤＞草地土壤＞农田土壤；从平均看，加(NH4)2SO4后有机氮矿化量有一定减少。在不同培养阶段，不同土类间氮素矿化率不同，在20d和40d时存在显著差异（p分别为0.0092和0.0381），60d时差异不显著，不同土类氮素矿化率的大小顺序为干润砂质新成土＞黄土正常新成土＞土垫旱耕人为土＞简育干润均腐土，这一结果说明在淹水条件下，黄土高原土壤从南到北易矿化氮所占全氮比例呈增加趋势。
Abstract:The objective of this experiment was to improve our understanding of soil organic N mineralization in the Loess Plateau. Typical soils were sampled from north to south in the Loess Plateau and soil organic N mineralization was measured in the soils using the Bremner incubation method. The soils were incubated for 60 d. The results showed that part of NH+4-N released during mineralization was fixed by clay minerals in these soils, so in order to get reliable results, we must consider this when determining total organic N mineralization. The amount of organic N mineralization was significantly different among the soil types. Specifically, the amount of mineralization decreased in the order Eum-Orthic Anthrosols > Los-Orthic Entisols > Hap-Ustic Isohumisols > Ust-Sandiic Entisols. The amount of organic N mineralization decreased from south to north across the Loess Plateau. The addition of Medicago sativa residue, which has a low C∶N ratio (C/N=21.7), increased the amount of organic N mineralization. In contrast, the addition of Stipa bungeana residue, which has a high C∶N ratio (C/N=43.3), increased microbial immobilization of soil mineral N. There were significant differences in the amount of organic N mineralization at 20d (p=0.0117), 40d (p=0.0109), and 60d (p=0.0073) depending on the type of vegetation growing on the soil at the time the samples were collected. The amount of organic N mineralization tended to decrease in the order: forest soil > bare land soil > grassland soil > farmland soil. The addition of (NH4)2SO4 to the soil resulted in a decrease in the N mineralization rate at 20d (p=0.0037), 40d (p=0.0033), and 60d (p=0.0027) compared to soils which did not receive (NH4)2SO4. There was a significant difference in the N mineralization rate among the different soil types when incubated for 20d (p=0.0092) and 40d (p=0.0381), however, there was no significant difference in mineralization rates among the soils(when incubated for 60d. Organic N mineralization rates tended to decrease in the order: Ust-Sandiic Entisols > Los-Orthic Entisols > Eum-Orthic Anthrosols > Hap-Ustic Isohumisols. The results showed that total organic N mineralization rates increased from south to north in the Loess Plateau.
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