Kohzu Ayato, Iwata T, Kato M, Nishikawa J, Wada Eitaro, Amartuvshin N, Namkhaidorj B, Fujita N
National Institute for Environmental Studies, Japan.
Isotopes Environ Health Stud. 2009 Sep;45(3):208-19. doi: 10.1080/10256010902871887.
Overgrazing often lowers species richness and productivity of grassland communities. For Mongolian grassland ecosystems, a lack of detailed information about food-web structures makes it difficult to predict the effects of overgrazing on species diversity and community composition. We analysed the delta13C and delta15N signatures of herbaceous plants, arthropods (grouped by feeding habit), wild and domestic mammals, and humans in central Mongolia to understand the predominant food-web pathways in this grassland ecosystem. The delta13C and delta15N values of mammals showed little variation within species, but varied considerably with slope position for arthropods. The apparent isotopic discrimination between body tissue and hair of mammals was estimated as 2.0 per thousand for delta13C and 2.1 per thousand for delta15N, which was large enough to cause overestimation of the trophic level of mammals if not taken into account when using hair samples to measure isotopic enrichment.
过度放牧常常会降低草原群落的物种丰富度和生产力。对于蒙古草原生态系统而言，由于缺乏有关食物网结构的详细信息，很难预测过度放牧对物种多样性和群落组成的影响。我们分析了蒙古中部草本植物、节肢动物（按食性分组）、野生和家养哺乳动物以及人类的δ13C和δ15N特征，以了解该草原生态系统中主要的食物网路径。哺乳动物的δ13C和δ15N值在物种内变化很小，但节肢动物的这些值随坡位有很大变化。哺乳动物身体组织和毛发之间的表观同位素分馏估计为δ13C为千分之2.0，δ15N为千分之2.1，如果在使用毛发样本测量同位素富集时不考虑这一点，这足以导致对哺乳动物营养级的高估。
