Catch crops increase plant species richness in crop rotations, but are most often grown as pure stands. Here, we investigate the impacts of increasing plant diversity in catch crop rotations on rhizosphere C input and microbial utilization. Mustard (Sinapis alba L.) planted as a single cultivar was compared to diversified catch crop mixtures of four (Mix4) or 12 species (Mix12). We traced the C transfer from shoots to roots towards the soil microbial community and the soil respiration in a 13C pulse labelling field experiment. Net CO2-C uptake from the atmosphere increased by two times in mix 4 and more than three times in mix 12. Higher net ecosystem C production was linked to increasing catch crop diversity and increased belowground transfer rates of recently fixed photoassimilates. The higher rhizosphere C input stimulated the growth and activity of the soil microbiome, which was investigated by phospholipid fatty acid (PLFA) analyses. Total microbial biomass increased from 14 to 22 g m−2 as compared to the fallow and was 18 and 8% higher for mix 12 and mix 4 as compared to mustard. In particular, the fungal and actinobacterial communities profited the most from the higher belowground C input and their biomass increased by 3.4 and 1.3 times as compared to the fallow. The residence time of the 13C pulse, traced in the CO2 flux from the soil environment, increased with plant diversity by up to 1.8 times. The results of this study suggest positive impacts of plant diversity on C cycling by higher atmospheric C uptake, higher transport rates towards the rhizosphere, higher microbial incorporation and prolonged residence time in the soil environment. We conclude that diversified catch crop mixtures improve the efficiency of C cycling in cropping systems and provide a promising tool for sustainable soil management.

中文翻译：

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捕捞作物多样性增加根际碳输入和土壤微生物生物量

捕捞作物在轮作中增加了植物物种的丰富度，但最常作为纯林种植。在这里，我们研究了在轮作中增加植物多样性对根际 C 输入和微生物利用的影响。将作为单一品种种植的芥菜 (Sinapis alba L.) 与四种 (Mix4) 或 12 种 (Mix12) 的多样化捕获作物混合物进行了比较。我们在 13C 脉冲标记田间实验中追踪了 C 从芽到根向土壤微生物群落和土壤呼吸的转移。来自大气的净 CO2-C 吸收在混合 4 中增加了两倍，在混合 12 中增加了三倍以上。较高的净生态系统 C 产量与增加捕获作物多样性和增加最近固定的光同化物的地下转移率有关。较高的根际 C 输入刺激了土壤微生物组的生长和活性，这通过磷脂脂肪酸 (PLFA) 分析进行了研究。与休耕相比，总微生物生物量从 14 gm-2 增加到 22 gm-2，与芥末相比，混合 12 和混合 4 分别高 18% 和 8%。特别是真菌和放线菌群落从较高的地下碳输入中获益最多，与休耕相比，它们的生物量增加了 3.4 和 1.3 倍。13C 脉冲的停留时间，在土壤环境中的 CO2 通量中追踪，随着植物多样性的增加而增加了 1.8 倍。这项研究的结果表明，植物多样性通过更高的大气 C 吸收、更高的向根际的传输速率对 C 循环产生积极影响，更高的微生物掺入量和延长土壤环境中的停留时间。我们得出的结论是，多样化的捕获作物混合物提高了作物系统中碳循环的效率，并为可持续的土壤管理提供了一个有前途的工具。