Non-symbiotic N-2-fixation in acidic and pH-neutral forest soils: Aerobic and anaerobic differentials

被引:64
作者
Limmer, C [1 ]
Drake, HL [1 ]
机构
[1] UNIV BAYREUTH,BITOK,LEHRSTUHL OKOL MIKROBIOL,D-95440 BAYREUTH,GERMANY
关键词
D O I
10.1016/0038-0717(95)00118-2
中图分类号
S15 [土壤学];
学科分类号
0903 ; 090301 ;
摘要
The effects of aerobic and anaerobic conditions on nitrogenase activities in forest soils (in particular that of a beech forest) obtained from northeast Bavaria (Germany) were assessed by both C2H2-reduction and N-15(2)-fixation methods. Nitrogenase activity occurred without detectable delay under both aerobic and anaerobic conditions; in both cases, initial rates approximated 0.2 nmol C2H2 reduced g(-1) d.w. soil d(-1). Prolonged anaerobic conditions yielded rates approximating 6 nmol C2H2 reduced g(-1) d.w. soil d(-1); in contrast, rates remained relatively constant under aerobic conditions independent of the incubation period. When soils were amended with glucose, significantly higher C2H2-reduction rates (1-4 mu mol C2H2 reduced g(-1) d.w. soil d(-1)) occurred only under anaerobic conditions. Assays with N-15(2) confirmed this N-2-fixation activity; based on initial reaction rates with moistened, but otherwise unamended soils, estimated N-2-fixation activity approximated 0.2 kg N-fixed ha(-1) y(-1). Compared to activities obtained under static conditions, shifts from aerobic to anaerobic conditions greatly enhanced N-2-fixation activities. High anaerobic-to-aerobic activity ratios were obtained with both pH neutral and weakly acidic (pH 4.5-5.9) hardwood and coniferous forest soils. These consistently high anaerobic N-2-fixation activities indicate that this process is likely limited to O-2-deficient microsites in forest soils. No nitrogenase activity was detected with extremely acidic coniferous forest soils (pH 2.7-3.3) under either anaerobic or aerobic conditions.
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页码:177 / 183
页数:7
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