High rates of nitrification and nitrate turnover in undisturbed coniferous forests
High rates of nitrification and nitrate turnover in undisturbed coniferous forests
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DOI：
10.1038/385061a0
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发表时间：
1997
期刊：
影响因子：
64.8
通讯作者：
J. Stark;S. Hart
中科院分区：
文献类型：
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作者：
J. Stark;S. Hart
硝酸盐（NO-3）在未受干扰的针叶林生态系统的内部氮循环的重要性还没有得到广泛认可1，2。这些森林土壤中的硝酸盐浓度往往很低，测定净硝化作用的试验通常显示出非常慢的速率3，4。然而，在这些土壤中，微生物对NO-3的同化作用可能很大，净硝化速率大大低估了总速率5。在这里，我们使用15 N同位素稀释技术，在完整的土壤芯，以测量总速率的硝化和微生物同化的NO-3在新墨西哥州和俄勒冈州的11个未受干扰的森林生态系统。我们发现，总硝化率是令人惊讶的高，在所有的森林检查。净硝化速率对总硝化速率的预测效果较差，因为土壤微生物群落具有吸收几乎所有产生的NO-3的能力。据我们所知，这是第一个报告的总硝化和NO-3同化率在完整的土壤样品从大量的对比森林生态系统。我们的研究结果反驳了以前的假设，硝化率低，在成熟的针叶林，并建议目前的模型大大低估了微生物群落在防止NO-3损失的作用。
THE importance of nitrate (NO–3) in the internal nitrogen cycle of undisturbed coniferous ecosystems has not been widely recognized1,2. Nitrate concentrations in soils from these forests tend to be low, and assays measuring net nitrification usually show exceedingly slow rates3,4. It may be, however, that microbial assimilation of NO–3is substantial in these soils, and that net nitrification rates greatly underestimate gross rates5. Here we use a15N isotope-dilution technique in intact soil cores to measure gross rates of nitrification and microbial assimilation of NO–3in eleven undisturbed forest ecosystems of New Mexico and Oregon. We found that gross nitrification rates were surprisingly high in all of the forests examined. Net nitrification rates poorly predicted gross rates because the soil microbial communities had the capacity to assimilate almost all of the NO–3produced. To our knowledge, this is the first report of gross nitrification and NO–3assimilation rates in intact soil samples from a large number of contrasting forest ecosystems. Our results contradict previous assumptions that nitrification rates are low in mature coniferous forests and suggest that current models greatly underestimate the role of the microbial community in preventing NO–3loss.