Data from: Recognizing cross-ecosystem responses to changing temperatures: soil warming impacts pelagic food webs

The energy and materials that move across ecosystem boundaries influence food web structure and key ecosystem functions. Despite the acknowledged importance of such ecological subsidies, surprisingly little information is available regarding the role of environmental temperature in influencing subsidy quality and the response of the recipient ecosystem. We evaluated the impacts of temperature-mediated changes in leaves from deciduous trees, an important subsidy from terrestrial to freshwater ecosystems, on both the producer-based and detritivore-based components of a pelagic pond food web in a field mesocosm experiment. We hypothesized that variation in leaf chemistry driven by increased soil temperature would alter both the quality of leaf subsidies and the pond response. We collected red maple (Acer rubrum) leaves from heated and ambient temperature plots from the long-term soil warming experiment at the Harvard Experimental Forest and added them to 167 L field mesocosms containing established plankton communities, creating “no leaf”, “ambient leaf” and “heated leaf” treatments during autumn 2012. We then monitored physical, chemical, and biological responses to treatments until the mesocosms froze 6 weeks later. Experimental soil warming altered the chemical composition of deciduous leaves, the physical and chemical environment of the aquatic ecosystems to which leaves were added, and the pelagic pond food webs as measured by community composition. Compared to leaves from ambient-temperature soils, leaves from warmed soils initially resulted in lower water column phosphorus and dissolved organic carbon, reducing bacterial densities. However, the diminished carbon and phosphorus resulting from soil warming also increased light availability that ultimately stimulated cladoceran zooplankton relative to ambient-temperature leaves. Our results suggest that changes in temperature can alter ecological subsidies in unanticipated ways, and suggest that accurately predicting the potential consequences of climate change will require conducting research across ecosystem boundaries.跨生态系统边界流动的能量与物质，会对食物网结构与关键生态系统功能产生影响。尽管此类生态补贴（ecological subsidies）的重要性已得到学界公认，但有关环境温度如何影响补贴质量以及受体生态系统响应的相关研究信息却极为匮乏。本研究依托野外中型实验（field mesocosm experiment），评估了落叶树叶片——这是陆地向淡水生态系统输送的重要生态补贴——的温度介导变化，对浮游池塘食物网中基于生产者与碎屑食性动物的两个组分的影响。我们提出如下假说：土壤温度升高所驱动的叶片化学性状变异，将同时改变叶片补贴的质量与池塘生态系统的响应。我们从哈佛大学实验森林（Harvard Experimental Forest）长期土壤增温实验的加热样地与常温样地，采集了红枫（Acer rubrum）叶片，并于2012年秋季将其添加至容积为167升的野外中型实验容器中，这些容器内已预先建立浮游群落，由此设置了"无叶片""常温叶片"与"增温叶片"三组处理。随后我们对各处理组的物理、化学与生物学响应进行了持续监测，直至6周后中型实验容器内的水体完全结冰为止。实验性土壤增温改变了落叶树叶片的化学组成、叶片所汇入的水生生态系统的物理与化学环境，以及通过群落组成表征的浮游池塘食物网结构。与取自常温土壤的叶片相比，取自增温土壤的叶片最初会降低水柱中的磷与溶解有机碳含量，进而导致细菌密度下降。然而，土壤增温所引发的碳与磷含量降低，同时也提升了光照可利用性，最终相较于常温叶片处理组，促进了枝角类浮游动物（Cladoceran Zooplankton）的相对丰度。本研究结果表明，温度变化能够以未被预期的方式改变生态补贴，同时也提示，若要精准预测气候变化的潜在影响，需开展跨生态系统边界的相关研究。