Lu Jiayu, Yang Jinfeng, Keitel Claudia, Yin Liming, Wang Peng, Cheng Weixin, Dijkstra Feike A
CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China.
School of Life and Environmental Sciences, Sydney Institute of Agriculture, The University of Sydney, Sydney, NSW, Australia.
Front Plant Sci. 2022 Jun 24;13:927435. doi: 10.3389/fpls.2022.927435. eCollection 2022.
Photosynthetically derived carbon (C) is allocated belowground, allowing plants to obtain nutrients. However, less is known about the amount of nutrients acquired relative to the C allocated belowground, which is referred to as C efficiency for nutrient acquisition (CENA). Here, we examined how C efficiency for nitrogen (N) and phosphorus (P) acquisition varied between ryegrass () and clover () with and without P fertilization. A continuous C-labeling method was applied to track belowground C allocation. Both species allocated nearly half of belowground C to rhizosphere respiration (49%), followed by root biomass (37%), and rhizodeposition (14%). With regard to N and P, CENA was higher for clover than for ryegrass, which remained higher after accounting for relatively low C costs associated with biological N fixation. Phosphorus fertilization increased the C efficiency for P acquisition but decreased the C efficiency for N acquisition. A higher CENA for N and P in clover may be attributed to the greater rhizosphere priming on soil organic matter decomposition. Increased P availability with P fertilization could induce lower C allocation for P uptake but exacerbate soil N limitation, thereby making N uptake less C efficient. Overall, our study revealed that species-specific belowground C allocation and nutrient uptake efficiency depend on which nutrient is limited.
光合作用产生的碳（C）被分配到地下，使植物能够获取养分。然而，相对于分配到地下的碳，所获取的养分数量（即养分获取的碳效率，CENA）却鲜为人知。在这里，我们研究了在施磷和不施磷的情况下，黑麦草（）和三叶草（）之间氮（N）和磷（P）获取的碳效率如何变化。采用连续碳标记法来追踪地下碳分配。两种植物都将近一半的地下碳分配到根际呼吸（49%），其次是根生物量（37%）和根际沉积（14%）。关于氮和磷，三叶草的CENA高于黑麦草，在考虑到与生物固氮相关的相对较低的碳成本后，三叶草的CENA仍然更高。施磷提高了磷获取的碳效率，但降低了氮获取的碳效率。三叶草对氮和磷更高的CENA可能归因于其对土壤有机质分解更大的根际激发效应。施磷增加了磷的有效性，可能会导致用于磷吸收的碳分配降低，但加剧了土壤氮限制，从而使氮吸收的碳效率降低。总体而言，我们的研究表明，物种特异性的地下碳分配和养分吸收效率取决于哪种养分受到限制。
