Responses to nitrate pollution, warming and density in common frog tadpoles (Rana temporaria)

Amphibians face a variety of anthropogenic
environmental perturbations that could act alone or in combination to influence
population size. We investigated interactive effects of warming conditions, a
moderate pulse of nitrogen pollution, and conspecific density on larvae of the
common frog, Rana temporaria. The 16-day experiment had a 2 × 2 × 2 factorial design
implemented in 80-l
Ecology outdoor mesocosms. High density and warm
temperature both resulted in reduced activity and visibility; tadpoles grew and
developed more quickly at low density and high temperature. The high-nitrogen
treatment did not influence behavior, growth, or development rate. We attribute
this to several realistic features of our study, including a pulsed treatment
application and natural denitrification within the mesocosms. There was only a
single interaction among the three factors: higher temperature exacerbated
density-dependence in growth rate. These results illustrate that climate
warming may benefit temperate amphibians, although the benefits may be
counteracted by enhanced larval crowding.

两栖动物面临着众多由人类活动引起的生态环境扰动，这些扰动可能单独或联合作用于种群数量。本研究探讨了温暖条件、适度的氮污染脉冲以及同种密度对普通青蛙（Rana temporaria）幼虫的交互影响。为期16天的实验采用了在80升生态学户外中尺度生态系统中的2×2×2因子设计。高密度和高温均导致活动能力和可见性降低；在低密度和高温条件下，蝌蚪的生长和发育更为迅速。高氮处理对行为、生长或发育速率没有影响。我们将其归因于本研究中的一些现实特征，包括脉冲处理的应用和中尺度生态系统内的自然反硝化作用。三个因素之间仅存在一个交互作用：较高的温度加剧了密度依赖性对生长速率的影响。这些结果揭示了气候变暖可能对温带两栖动物有益，尽管这种益处可能因幼虫拥挤程度的增加而被抵消。