Korobushkin Daniil I, Gongalsky Konstantin B, Tiunov Alexei V
A. N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, 33 Leninsky prospect, Moscow, 119071, Russia.
Rapid Commun Mass Spectrom. 2014 Jun 15;28(11):1303-11. doi: 10.1002/rcm.6903.
Stable isotope analysis (SIA) is used widely for reconstructing trophic links of vertebrate and invertebrate animals. Soil macrofauna form a substantial food source for a range of predators including amphibians, reptiles, birds and mammals. SIA-based estimations of their trophic niches require knowledge on the full range of isotopic signatures of potential preys. Considering the extremely high diversity of soil animals, this information is not easy to obtain.
We estimated a typical range of the isotopic signatures of soil macrofauna by compiling published and original data on soil macroinvertebrates in 11 temperate forests. We examined whether the baseline correction (i.e. subtracting δ(13)C or δ(15)N values of local litter) would decrease the between-site variability in the δ(13)C and δ(15)N values of soil animals. The dataset was subsequently used to estimate the frequency distribution of δ(13)C and δ(15)N values in saprophagous and predatory soil animals.
The baseline correction reduced the between-site variability in δ(15)N, but not in δ(13)C values of soil animals. Over 95% of the taxa or individuals examined fell into an isotopic space with uncorrected δ(13)С values ranging from -27.9 to -22.5‰, and litter-normalized δ(15)N values from 0.8 to 9.6‰. Saprophagous and predatory soil animals were on average enriched in (13)C relative to plant litter by 3.5 and 2.7‰, respectively, which is likely to reflect the importance of saprotrophic microorganisms as the main energy source in soil food webs. The difference in δ(15)N values between saprophages and predators averaged 2.8‰, which fits the anticipated trophic enrichment per trophic level.
Our results indicate that the range of possible δ(15)N values of soil macrofauna in temperate forest ecosystems can roughly be predicted based on the δ(15)N values of plant litter. On the other hand, no site-specific normalization is usually required when predicting the range of δ(13)C values of soil macroinvertebrates.
稳定同位素分析（SIA）被广泛用于重建脊椎动物和无脊椎动物的营养联系。土壤大型动物是包括两栖动物、爬行动物、鸟类和哺乳动物在内的一系列捕食者的重要食物来源。基于SIA对其营养生态位的估计需要了解潜在猎物的完整同位素特征范围。考虑到土壤动物的极高多样性，这些信息并不容易获得。
我们通过汇编11个温带森林中土壤大型无脊椎动物的已发表数据和原始数据，估计了土壤大型动物同位素特征的典型范围。我们研究了基线校正（即减去当地凋落物的δ(13)C或δ(15)N值）是否会降低土壤动物δ(13)C和δ(15)N值的站点间变异性。随后，该数据集被用于估计腐食性和捕食性土壤动物δ(13)C和δ(15)N值的频率分布。
基线校正降低了土壤动物δ(15)N的站点间变异性，但未降低δ(13)C值的变异性。超过95%的被检查分类群或个体落入一个同位素空间，未校正的δ(13)С值范围为-27.9至-22.5‰，凋落物标准化的δ(15)N值范围为0.8至9.6‰。相对于植物凋落物，腐食性和捕食性土壤动物的平均(13)C富集分别为3.5‰和2.7‰，这可能反映了腐生微生物作为土壤食物网主要能量来源的重要性。腐食者和捕食者之间的δ(15)N值差异平均为2.8‰，这符合每个营养级预期的营养富集。
我们的结果表明，基于植物凋落物的δ(15)N值，可以大致预测温带森林生态系统中土壤大型动物可能的δ(15)N值范围。另一方面，在预测土壤大型无脊椎动物δ(13)C值范围时，通常不需要进行特定地点的标准化。
