Combining bulk and amino acid stable isotope analyses to quantify trophic level and basal resources of detritivores: a case study on earthworms
Combining bulk and amino acid stable isotope analyses to quantify trophic level and basal resources of detritivores: a case study on earthworms
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DOI：
10.1007/s00442-018-04335-3
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发表时间：
2019-01
期刊：
影响因子：
2.7
通讯作者：
A. Potapov;A. Tiunov;S. Scheu;T. Larsen;Melanie M. Pollierer
中科院分区：
文献类型：
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作者：
A. Potapov;A. Tiunov;S. Scheu;T. Larsen;Melanie M. Pollierer
定量的细菌，真菌和植物能量渠道的营养营养的营养是方法学上的挑战。对于蚯蚓来说尤其如此，因为蚯蚓会吞食大量的垃圾和混合了微生物的土壤。与整体稳定同位素分析（bulk SIA）相比，单个氨基酸中C和N的化合物特异性稳定同位素分析（CSIA）等新方法有望在该领域取得重大进展。本研究将CSIA和碳氮的大量SIA结合起来，量化了北温带和温带森林生态系统中表观和内源蚯蚓物种与不同能量通道的联系。结果表明，植物直接向蚯蚓输送的能量显著（33-50%的必需氨基酸，EAA）改善了蚯蚓在土壤食物网中的地位，既是微生物的竞争者，也是微生物的消费者。附生蚯蚓主要依赖于植物凋落物，内生蚯蚓主要依赖于细菌和土壤有机质。这两组与植物或微生物能量通道的联系可能是由碎屑质的驱动的。块状15n和13c的富集与蚯蚓的营养水平有关。此外，15N的富集与日粮中细菌和植物EAA的比例有关。营养水平（氮的CSIA）与植物EAA的比例（碳的CSIA）呈显著负相关，表明这两种新方法都可以反映营养动物的微生物化程度。氨基酸的CSIA提供了关于营养动物基础资源和营养水平的详细和独立于基线的信息。
Quantification of the bacterial, fungal, and plant energy channels to the nutrition of detritivores is methodologically challenging. This is especially true for earthworms that ingest large amounts of litter and soil mixed with microorganisms. Novel methods such as compound-specific stable isotope analysis (CSIA) of C and N of individual amino acids promise major progress in this field in comparison with bulk stable isotope analysis (bulk SIA). Here, we combine CSIA and bulk SIA of carbon and nitrogen to quantify the linkage of epigeic and endogeic earthworm species to different energy channels across boreal and temperate forest ecosystems. The results showed pronounced flux of energy directly from plants to earthworms (33–50% of essential amino acids, EAA) refining the position of earthworms in soil food webs as both competitors and consumers of microorganisms. Epigeic earthworm species primarily relied on plant litter and endogeic species primarily relied on bacteria and soil organic matter. The linkage of both groups to plant or microbial energy channel was likely driven by the quality of detritus. Both bulk15N and13C enrichments were related to the trophic level of earthworms. Furthermore,15N enrichment was related to the proportions of bacterial and plant EAA in the diet. Strong negative correlation between trophic level (CSIA of nitrogen) and the proportion of plant EAA (CSIA of carbon) suggests that both novel methods can indicate the degree of microbivory in detritivores. CSIA of amino acids provide detailed and baseline-independent information on basal resources and trophic levels of detritivores.