氮稳定同位素基准的可变性及对营养级评价的影响

Variability of stable nitrogen isotopic baselines and its consequence for trophic modeling

稳定同位素技术已经成为生态学家研究生态系统特征与过程的重要手段之一。在利用稳定同位素研究植物-动物和动物之间的营养关系或者进行多生态系统的比较研究过程中,通常需要选择某种生物的稳定同位素作为"基准(baseline)"。同位素基准的目的是反映食物网生物最初物质来源的同位素特征。同位素基准的选择取决于具体研究问题与系统。本文综述了水域生态系统研究中初级生产者和初级消费者氮稳定同位素作为基准的应用。不同的研究都根据自身所关注的生态学问题对基准进行选择和校正。然而,找到适当的同位素基准取决于同位素基准种内、种间和时空上的同位素变化特征,同时还取决于所关注的生态学问题的时间、空间尺度。本文评估了季节性和种内的同位素变异性对消费者营养级位置的影响。质量平衡模型的计算结果说明同位素基准可变性可以显著影响对消费者营养级位置的评估。

Ecologists frequently use stable isotopes to measure the pattern and process of interested ecosystems. Comparisons of food web structure among and within ecosystems rely on a baseline isotopic signature for each system. The goal of atrophic baseline is to reflect the isotopic signature of the primary source of materials and nutrients for the food web. In general isotope baseline selection depends on the specific research question and must be tailored to a particular study system. We reviewed the use of the stable nitrogen isotopic signatures of primary producers and primary consumers to develop the baseline in aquatic ecology. Each of these studies used a slightly different method of baseline correction that was tailored to address a question of specific ecological interest. However, choosing an appropriate baseline depends on the inter- and intraspecific spatial, temporal variability of isotopic baselines and on the spatial and temporal context of the ecological question under consideration. We also evaluated to what extent isotopic heterogeneity actually influence consumer＇ strophic positions at the temporal and intraspecifical scales. The result of trophic position output estimated using an isotopic mixing model was generally variable, provided that baseline variability for trophic position estimation were sufficiently distinct in dietary mixing models.