Joint effects of resources and amphibians on pond ecosystems

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• 作者：Freya E. Rowland ; Madelyn B. Rawlings ; Raymond D. Semlitsch
• 关键词：Food webs ; Salamanders ; Anurans ; Bottom–up ; Top–down
• 刊名：Oecologia
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：183
• 期：1
• 页码：237-247
• 全文大小：
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Ecology; Plant Sciences; Hydrology/Water Resources;
• 出版者：Springer Berlin Heidelberg
• ISSN：1432-1939
• 卷排序：183

文摘

Primary production can be controlled through bottom–up (e.g., resources) or top–down (e.g., predators) constraints. Two key bottom–up resources in small aquatic systems are light and nutrients, and forest canopy cover heavily influences these factors, whereas amphibian and invertebrate colonizers exert top–down pressure as grazers and predators. We designed our experiment to specifically manipulate two different top–down and bottom–up factors. We manipulated resources by altering light (low/high) and nutrient (low/high) availability; omnivores with the presence/absence of southern leopard frog tadpoles (Lithobates sphenocephalus); and predators with the presence/absence of spotted salamander larvae (Ambystoma maculatum) in a full-factorial experiment conducted over 14 weeks. We observed that both bottom–up and top–down effects were important in predicting lower trophic level biomass. We found a significant top–down effect of salamanders on Daphnia, but tadpoles had the strongest overall effect on the food web, influencing phytoplankton (+), periphyton (−), and chironomids (−). None of our models were good predictors of phytoplankton biomass, but both shading and nutrient availability relatively equally boosted periphyton biomass. We also found large temporal differences in food-web dynamics. Our results underscore the need for more information into how ecosystem functioning could be altered by land use, amphibian extirpation, and climate change.