School of the Environment, Yale University, New Haven, CT, USA.
J Anim Ecol. 2021 Jul;90(7):1714-1726. doi: 10.1111/1365-2656.13489. Epub 2021 Apr 13.
Functional traits are useful for characterizing variation in community and ecosystem dynamics. Most advances in trait-based ecology to date centre on plant functional traits, although there is an increasing recognition that animal traits are also key contributors to processes operating at the community or ecosystem scale. Terrestrial invertebrates are incredibly diverse and ubiquitous animals with important roles in nutrient cycling. Despite their widespread influence on ecosystem processes, we currently lack a synthetic understanding of how invertebrate functional traits affect terrestrial nutrient cycling. We present a meta-analysis of 511 paired observations from 122 papers that examined how invertebrate functional traits affected litter decomposition rates, nitrogen pools and litter C:N ratios. Based on the available data, we specifically assessed the effects of feeding mode (bioturbation, detritus shredding, detritus grazing, leaf chewing, leaf piercing, ambush predators, active hunting predators) and body size (macro- and micro-invertebrates) on nutrient cycling. The effects of invertebrates on terrestrial nutrient cycling varied according to functional trait. The inclusion of both macro- (≥2 mm) and micro-invertebrates (<2 mm) increased litter decomposition by 20% and 19%, respectively. All detritivorous feeding modes enhanced litter decomposition rates, with bioturbators, detritus shredders and detritus grazers increasing decomposition by 28%, 22% and 15%, respectively. Neither herbivore feeding mode (e.g. leaf chewers and leaf piercers) nor predator hunting mode (ambush and active hunting) affected decomposition. We also revealed that bioturbators and detritus grazers increased soil nitrogen availability by 99% and 70%, respectively, and that leaf-chewing herbivores had a weak effect on litterfall stoichiometry via reducing C:N ratios by 11%. Although functional traits might be useful predictors of ecosystem processes, our findings suggest context-dependent effects of invertebrate traits on terrestrial nutrient cycling. Detritivore functional traits (i.e. bioturbators, detritus shredders and detritus grazers) are more consistent with increased rates of nutrient cycling, whereas our currently characterized predator and herbivore traits are less predictive. Future research is needed to identify, standardize and deliberately study the impacts of invertebrate functional traits on nutrient cycling in hopes of revealing the key functional traits governing ecosystem functioning worldwide.
功能特征对于描述群落和生态系统动态变化是非常有用的。迄今为止，基于特征的生态学领域的大多数进展都集中在植物功能特征上，尽管人们越来越认识到动物特征也是对群落或生态系统尺度上的过程起关键作用的因素。陆生无脊椎动物是种类繁多、无处不在的动物，它们在养分循环中起着重要作用。尽管它们对生态系统过程有着广泛的影响，但我们目前还缺乏对无脊椎动物功能特征如何影响陆地养分循环的综合理解。我们对 122 篇论文中的 511 对观测结果进行了荟萃分析，这些论文研究了无脊椎动物功能特征如何影响凋落物分解率、氮库和凋落物 C:N 比。根据现有数据，我们专门评估了摄食模式（生物扰动、碎屑分解、碎屑摄食、啃食叶片、刺穿叶片、埋伏捕食者、主动猎食捕食者）和体型（大型和微型无脊椎动物）对养分循环的影响。无脊椎动物对陆地养分循环的影响因功能特征而异。同时包含大型（≥2 毫米）和微型无脊椎动物（＜2 毫米）可分别将凋落物分解提高 20%和 19%。所有碎屑食性的摄食模式都提高了凋落物分解率，生物扰动者、碎屑分解者和碎屑摄食者分别提高了 28%、22%和 15%。食草动物的摄食模式（如啃食叶片者和刺穿叶片者）或捕食者的猎食模式（埋伏和主动猎食者）都没有影响分解。我们还发现，生物扰动者和碎屑摄食者分别使土壤氮素有效性增加了 99%和 70%，而啃食叶片的食草动物通过降低 C:N 比 11%对凋落物化学计量产生了微弱的影响。虽然功能特征可能是预测生态系统过程的有用指标，但我们的研究结果表明，无脊椎动物特征对陆地养分循环的影响具有依赖于环境的特征。碎屑食性功能特征（即生物扰动者、碎屑分解者和碎屑摄食者）与养分循环速率的提高更为一致，而我们目前所描述的捕食者和食草动物特征则不太具有预测性。需要进一步的研究来确定、标准化并有意研究无脊椎动物功能特征对养分循环的影响，以期揭示全球范围内控制生态系统功能的关键功能特征。
