Data from: Removal of an apex predator initiates a trophic cascade that extends from herbivores to vegetation and the soil nutrient pool

It is widely assumed that organisms at low trophic levels, particularly microbes and plants, are essential to basic services in ecosystems, such as nutrient cycling. In theory, apex predators' effects on ecosystems could extend to nutrient cycling and the soil nutrient pool by influencing the intensity and spatial organization of herbivory. Here, we take advantage of a long-term manipulation of dingo abundance across Australia's dingo-proof fence in the Strzelecki Desert to investigate the effects that removal of an apex predator has on herbivore abundance, vegetation and the soil nutrient pool. Results showed that kangaroos were more abundant where dingoes were rare, and effects of kangaroo exclusion on vegetation, and total carbon, total nitrogen and available phosphorus in the soil were marked where dingoes were rare, but negligible where dingoes were common. By showing that a trophic cascade resulting from an apex predator's lethal effects on herbivores extends to the soil nutrient pool, we demonstrate a hitherto unappreciated pathway via which predators can influence nutrient dynamics. A key implication of our study is the vast spatial scale across which apex predators' effects on herbivore populations operate and, in turn, effects on the soil nutrient pool and ecosystem productivity could become manifest.

人们普遍认为，低营养级（trophic levels）生物（尤其是微生物与植物）是生态系统基础服务（如养分循环（nutrient cycling））的核心支撑。理论上，顶级捕食者（apex predators）可通过调控草食作用的强度与空间分布格局，间接影响生态系统的养分循环与土壤养分库（soil nutrient pool）。本研究依托澳大利亚斯特雷勒基沙漠（Strzelecki Desert）区域跨防野犬围栏（dingo-proof fence）的长期野犬种群密度操控实验，探究顶级捕食者移除对草食动物种群丰度、植被及土壤养分库的影响。实验结果显示：野犬种群稀少区域的袋鼠丰度更高；且在野犬稀少的生境中，排除袋鼠对植被、土壤总碳、总氮及有效磷（available phosphorus）的影响显著，而在野犬常见的生境中该影响可忽略不计。本研究证实，由顶级捕食者对草食动物的致死效应引发的营养级联（trophic cascade）效应可延伸至土壤养分库，揭示了此前未被认知的捕食者调控养分动态（nutrient dynamics）的途径。本研究的核心启示在于：顶级捕食者对草食动物种群的调控作用可在极广空间尺度上发生，进而对土壤养分库与生态系统生产力（ecosystem productivity）产生显著影响。