Department of Biology and Biodiversity, Lund University, Lund, Sweden.
Department of Biology and Microbial Ecology, Lund University, Lund, Sweden.
Glob Chang Biol. 2017 Dec;23(12):5372-5382. doi: 10.1111/gcb.13803. Epub 2017 Aug 17.
A decisive set of steps in the terrestrial carbon (C) cycle is the fixation of atmospheric C by plants and the subsequent C-transfer to rhizosphere microorganisms. With climate change winters are expected to become milder in temperate ecosystems. Although the rate and pathways of rhizosphere C input to soil could be impacted by milder winters, the responses remain unknown. To address this knowledge-gap, a winter-warming experiment was established in a seminatural temperate grassland to follow the C flow from atmosphere, via the plants, to different groups of soil microorganisms. In situ CO pulse labelling was used to track C into signature fatty acids of microorganisms. The winter warming did not result in any changes in biomass of any of the groups of microorganisms. However, the C flow from plants to arbuscular mycorrhizal (AM) fungi, increased substantially by winter warming. Saprotrophic fungi also received large amounts of plant-derived C-indicating a higher importance for the turnover of rhizosphere C than biomass estimates would suggest-still, this C flow was unaffected by winter warming. AM fungi was the only microbial group positively affected by winter warming-the group with the closest connection to plants. Winter warming resulted in higher plant productivity earlier in the season, and this aboveground change likely induced plant nutrient limitation in warmed plots, thus stimulating the plant dependence on, and C allocation to, belowground nutrient acquisition. The preferential C allocation to AM fungi was at the expense of C flow to other microbial groups, which were unaffected by warming. Our findings imply that warmer winters may shift rhizosphere C-fluxes to become more AM fungal-dominated. Surprisingly, the stimulated rhizosphere C flow was matched by increased microbial turnover, leading to no accumulation of soil microbial biomass.
陆地碳（C）循环中的一系列关键步骤是植物固定大气 C，随后将 C 转移到根际微生物。预计随着气候变化，温带生态系统的冬季将变得更加温和。尽管冬季变暖可能会影响根际 C 向土壤输入的速率和途径，但这些响应仍不清楚。为了解决这一知识空白，在半自然温带草原中建立了冬季变暖实验，以跟踪 C 从大气经植物到不同土壤微生物群的流动。使用原位 13CO 脉冲标记来追踪 C 进入微生物的特征脂肪酸。冬季变暖并没有导致任何微生物群体的生物量发生变化。然而，植物到丛枝菌根（AM）真菌的 C 流动量因冬季变暖而显著增加。腐生真菌也接收了大量来自植物的 C-表明根际 C 的周转比生物量估计更为重要-尽管如此，这种 C 流动不受冬季变暖的影响。AM 真菌是唯一受冬季变暖正向影响的微生物群体-与植物关系最密切的群体。冬季变暖导致植物在季节早期的生产力更高，而这种地上变化可能会导致受暖区的植物养分限制，从而刺激植物对地下养分获取的依赖和 C 分配。对 AM 真菌的优先 C 分配是以牺牲对其他微生物群体的 C 流动为代价的，而这些微生物群体不受变暖的影响。我们的研究结果表明，温暖的冬季可能会使根际 C 通量发生变化，变得更加以 AM 真菌为主导。令人惊讶的是，刺激的根际 C 流与增加的微生物周转相匹配，导致土壤微生物生物量没有积累。
