Aims

Fire regimes are key drivers of ecosystem dynamics and are changing worldwide. Uncertainty about how fire history affects responses to individual fires hampers predictions of fire impacts on important ecosystem functions such as C cycling. Thus, we assessed how fire and fire history affect soil CO₂ flux and aboveground net primary production (ANPP).

Methods

We utilized a 35-year fire frequency experiment in a mesic grassland to quantify how two aspects of fire history, long-term fire frequency (fire every one, two, or four years, or no fire) and number of years elapsed since the most recent fire, affect soil CO₂ flux. We used long-term annual records from the same grassland to compare this to the effect of fire history on ANPP.

Results

Historic fire frequency altered the soil CO₂ flux response to fire, with greater post-fire stimulation in grassland burned annually than in grassland burned less frequently (~100% vs. ~44% increase over long-term unburned grassland). The flux increase persisted for up to two years after fire. Though fire also stimulated ANPP, this increase did not vary by long-term fire frequency and did not persist into later years.

Conclusions

Fire history modifies the soil CO₂ flux response to individual fires in this grassland. Predicting the dynamics of this important C flux will require considering not only the presence vs. absence of fire, but also fire history.

中文翻译：

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火灾历史是决定草地土壤CO 2通量的关键因素

目的

消防制度是生态系统动态的关键驱动力，并且正在全球范围内变化。火灾历史如何影响对单个火灾的响应的不确定性阻碍了火灾对重要生态系统功能（如碳循环）的影响的预测。因此，我们评估了火灾和火灾历史如何影响土壤CO ₂通量和地上净初级生产力（ANPP）。

方法

我们在一个中型草原上进行了为期35年的火灾频率实验，以量化火灾历史的两个方面，即长期火灾频率（每两年，四年或四年，或无火灾）和自最大火灾以来经过的年数。最近起火，影响土壤CO ₂通量。我们使用来自同一草原的长期年度记录，将其与火灾历史对ANPP的影响进行了比较。

结果

历史上的火灾频率改变了土壤CO ₂通量对火的响应，与每年不经常燃烧的草地相比，每年燃烧的草地对火灾后的刺激更大（与长期未燃烧的草地相比，增加约100％，而相对增加约44％）。火灾后通量增加持续了长达两年。尽管火灾也刺激了ANPP，但这种增加并没有因长期火灾频率而变化，并且一直持续到以后几年。

结论

火灾历史改变了该草地对单个火灾的土壤CO ₂通量响应。预测这种重要的C通量的动力学不仅需要考虑着火的存在与否，还需要考虑着火的历史。