Large carnivores have recently increased in number and recolonized in human-dominated landscapes; however, their ecological roles in these landscapes have not been well studied. In the Shiretoko World Heritage (SWH) site, brown bears have recolonized a previously abandoned mosaic landscape of natural forests and conifer plantations after land abandonment. We previously reported that the bears had recently begun to dig for cicada nymphs in association with the creation of larch plantations. As a result, this digging activity decreased soil nutrients. To deepen the understanding of the novel ecological role of brown bears within human-modified landscapes, we examined the impacts of brown bear digging on the growth of larch trees. We found that brown bear digging decreased fine root biomass of larch, soil water, and nitrogen availability. Brown bear digging negatively affected needle nitrogen content, but not carbon isotope ratios, a water stress index of trees. Tree ring data suggest that digging negatively affected the radial growth of larches. The results imply that digging decreases tree growth due to limited soil nitrogen uptake. Our findings indicate that the ecological roles of large carnivores may differ between natural and anthropogenic landscapes.

中文翻译：

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棕熊的挖掘减少了树木的生长：对人类景观中顶级捕食者的生态作用的影响

最近，大型食肉动物的数量有所增加，并在人类主导的地区重新定居；然而，它们在这些景观中的生态作用尚未得到充分研究。在知床世界遗产 (SWH) 地区，棕熊在土地废弃后重新定居在先前废弃的天然森林和针叶树种植园的马赛克景观中。我们之前报道过，随着落叶松种植园的建立，熊最近开始挖掘蝉若虫。结果，这种挖掘活动减少了土壤养分。为了加深对棕熊在人类改造景观中的新生态作用的理解，我们研究了棕熊挖掘对落叶松树生长的影响。我们发现棕熊挖掘降低了落叶松的细根生物量、土壤水和氮的有效性。棕熊挖掘对针叶氮含量产生负面影响，但对碳同位素比（树木的水分胁迫指数）没有影响。树木年轮数据表明，挖掘对落叶松的径向生长产生了负面影响。结果表明，由于土壤氮吸收有限，挖掘会降低树木生长。我们的研究结果表明，大型食肉动物的生态作用在自然景观和人为景观之间可能有所不同。