Net nitrogen mineralization and net nitrification along a tropical forest-to-pasture chronosequence
Net nitrogen mineralization and net nitrification along a tropical forest-to-pasture chronosequence
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DOI：
10.1007/bf01416090
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发表时间：
1994-05
期刊：
影响因子：
4.9
通讯作者：
M. Piccolo;C. Neill;C. Cerri
中科院分区：
文献类型：
--
作者：
M. Piccolo;C. Neill;C. Cerri
土壤无机氮库，净矿化和净硝化速率进行了比较，在旱季沿着的一个时间序列的高地（陆地firme）森林，3-，9-和20岁的牧场在巴西亚马逊盆地西部的朗州的森林转化为牧场对土壤氮循环的影响。森林土壤表层（0 ~ 10 cm）的可提取无机氮库大于草地土壤。在森林中，NO3−库等于或超过NH 4+库，而牧场无机N库几乎完全由NH 4+组成。在实验室培养的7天中，净氮矿化率和净硝化率在7天的森林中比在牧场中高。净氮矿化速率在不同年龄的草地之间没有显著差异，但净硝化速率在20岁的草地显着较低。较高的净氮矿化和净硝化速率测定在实验室和原位培养的筛分土壤，原位培养的完整的土芯相比。在7天孵育中计算的比率高于通过更长孵育确定的比率。与完整岩心相比，筛分可增加氮矿化和/或减少氮固定。我们的结论是，7天的实验室培养筛选土壤是最有用的指标，比较N的可用性在整个时序的森林和牧场网站。森林土壤的高净硝化率表明NO3−可能通过淋溶或气体排放而流失。
Soil inorganic nitrogen pools, net mineralization and net nitrification rates were compared during the dry season along a chronosequence of upland (terra firme) forest, 3-, 9- and 20-year-old pastures in the western Brazilian Amazon Basin state of Rondônia to investigate the influence of forest conversion to pasture on soil nitrogen cycles. Surface soil (0 to 10 cm) from forest had larger extractable inorganic nitrogen pools than pasture soils. In the forest, NO3−pools equaled or exceeded NH4+pools, while pasture inorganic N pools consisted almost exclusively of NH4+. Rates of net N mineralization and net nitrification in seven -day laboratory incubations were higher in the seven - day forest than in the pastures. Net N mineralization rates did not differ significantly among different-aged pastures, but net nitrification rates were significantly lower in the 20-year-old pasture. Higher net N mineralization and net nitrification rates were measured in laboratory and in situ incubations of sieved soil, compared with in situ incubations of intact soil cores. Rates calculated in seven-day incubations were higher than determined by longer incubations. Sieving may increase N mineralization and/or decrease N immobilization compared with intact cores. We concluded that 7-day laboratory incubation of sieved soil was the most useful index for comparing N availability across the chronosequence of forest and pasture sites. High net nitrification rates in forest soils suggest a potential for NO3−losses either through leaching or gaseous emissions.