Purpose

We investigated how the C flow from plants to microorganisms varies throughout the year in a temperate grassland. Additionally, we investigated how the C flow relates to saprotrophic activity and vegetation changes.

Methods

In situ stable isotope pulse labelling (¹³CO₂) was employed to estimate the flow of recently plant-derived C to soil microorganisms by using signature fatty acids. Bacterial and fungal growth was estimated using radio-labelling in laboratory incubations.

Results

The C flow from plants to arbuscular mycorrhizal (AM) fungi peaked during the warmer parts of the year, but saprotrophic microorganisms showed little temporal variation in C flow. Also saprotrophic fungi received considerable amounts of C from plants throughout the year. Bacterial and fungal growth showed temporal variation with a growth peak in August for both. This suggests a shift in the C source from mainly rhizosphere C in colder parts of the year, to older C-sources in warmer parts of the year (August).

Conclusion

We conclude that AM fungi, saprotrophic fungi and bacteria differ in the amount of recently-fixed C they receive from plants throughout the year. Hence, temporal patterns need to be considered to understand ecosystem functioning. The studied plant community included winter annuals, which potentially maintain a high C flow to saprotrophic fungi during the cold season.

中文翻译：

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使用13C标记和特征脂肪酸测量从草地植被到土壤微生物的碳流动的时间模式

目的

我们调查了温带草原中一年四季从植物流向微生物的碳的变化情况。此外，我们研究了C流量与腐养活动和植被变化之间的关系。

方法

原位稳定同位素脉冲标记（¹³ CO ₂）被用于通过使用特征性脂肪酸来估计最近植物衍生的C向土壤微生物的流动。在实验室培养中使用放射性标记估计细菌和真菌的生长。

结果

从植物到丛枝菌根（AM）真菌的碳流量在一年中较暖的时期达到顶峰，但是腐生微生物的碳流量几乎没有时间变化。一年四季，腐养真菌也从植物中吸收了大量的碳。细菌和真菌的生长均表现出时间变化，两者均在八月达到生长高峰。这表明碳源从一年中较冷的部分主要是根际碳转移到一年中较热的部分（8月）的较老的碳源。

结论

我们得出的结论是，全年中，AM真菌，腐生真菌和细菌在从植物中获得的最近固定的C量不同。因此，需要考虑时间模式以了解生态系统功能。所研究的植物群落包括冬季一年生植物，在寒冷季节，它们可能会保持较高的碳流向腐生真菌。