Soil respiration declines with increasing nitrogen fertilization and is not related to productivity in long-term grassland experiments
Soil respiration declines with increasing nitrogen fertilization and is not related to productivity in long-term grassland experiments
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DOI：
10.1016/j.soilbio.2017.08.035
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发表时间：
2017-12
影响因子：
9.7
通讯作者：
D. Ward;K. Kirkman;N. Hagenah;Z. Tsvuura
中科院分区：
文献类型：
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作者：
D. Ward;K. Kirkman;N. Hagenah;Z. Tsvuura
土壤呼吸通常被用作肥力的指标，因为大多数营养物质通过微生物生物量循环。在南非彼得马里茨堡附近的三个长期草地试验中，我们评估了土壤呼吸作为衡量资源生产力的一个指标的作用。所有这些实验都显示了草种组成和生产力的显着变化。自1951年以来，一直在进行一项控制氮肥、磷肥和石灰水平的草原（=田间）肥料试验。燃烧和割草实验（BME）自1950年以来一直在运行。第三个实验是营养网络（NutNet）的一部分，NutNet是一个全球肥料实验，自2009年以来一直在操作氮，磷，钾和微量营养素。我们发现，长期的实验更有可能表现出显着的影响土壤呼吸。我们发现几个显着的影响，但在VFE的土壤呼吸施肥处理之间的短期实验（NutNet）没有显着差异。在VFE中，我们发现由于氮肥水平、氮肥形式（石灰石硝酸铵和硫酸铵）、磷和石灰，土壤呼吸存在显着差异。我们发现，地上净初级生产力和土壤呼吸之间没有显着的关系，尽管经常检测到这样的模式，由于土壤呼吸，土壤肥力和生产力之间的联系。我们发现，虽然有一个一致的增加，土壤总氮的氮肥施用量的增加，有一个一致的减少，土壤微生物呼吸。有一个显着的正相关关系，土壤呼吸和pH值。这背后的可能机制尚不清楚，但可能涉及的优势酶的变化，并可能开关之间的优势细菌和真菌。我们还发现BME中燃烧时间的显着影响，但不是由于燃烧频率或割草的发生。我们的研究结果表明，研究可能需要长期的，例如这里至少10年，才能可靠地理解与土壤肥力的关键功能关系。
Soil respiration is often used as an index of fertility because the majority of nutrients are cycled through the microbial biomass. We assessed the role of soil respiration as a measure of resource productivity in three long-term grassland experiments near Pietermaritzburg, South Africa. All of these experiments have shown significant changes in grass species composition and productivity. An ongoing Veld (=field) Fertilizer Experiment (VFE) that manipulated the level of nitrogen fertilizer, phosphorus and lime has been running since 1951. A Burning and Mowing Experiment (BME) has been running since 1950. The third experiment is part of the Nutrient Network (NutNet), a global fertilizer experiment that has been manipulating nitrogen, phosphorus, potassium and micronutrients and has been running since 2009. We found that longer-term experiments were more likely to show significant effects on soil respiration. We found several significant effects in the VFE but no significant differences in soil respiration among fertilization treatments in the shortest-term experiment (NutNet). In the VFE, we found significant differences in soil respiration due to levels of nitrogen fertilizer, form of nitrogen fertilizer (limestone ammonium nitrate and ammonium sulphate), phosphorus and lime. We found no significant relationship between above-ground net primary productivity and soil respiration despite the frequent detection of such a pattern due to the link between soil respiration, soil fertility and productivity. We found that, while there was a consistent increase in total soil nitrogen with increasing levels of nitrogen fertilizer applied, there was a consistent decrease in soil microbial respiration. There was a significant positive correlation between soil respiration and pH. Possible mechanisms behind this are unclear but may involve changes in dominant enzymes and possibly switches between dominance of bacteria and fungi. We also found significant effects of the timing of burning in the BME, but not due to the frequency of burning or the occurrence of mowing. Our results suggest that studies may need to be long-term, for example here at least 10 years, before key functional relationships with soil fertility can be reliably understood.