Drying, more than warming, alters ecosystem functioning in streams with different energy pathways
Drying, more than warming, alters ecosystem functioning in streams with different energy pathways
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DOI：
10.1111/1365-2435.14351
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发表时间：
2023-05
影响因子：
5.2
通讯作者：
Daniel Nelson;Michelle H. Busch;D. Kopp;D. Allen
中科院分区：
文献类型：
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作者：
Daniel Nelson;Michelle H. Busch;D. Kopp;D. Allen
经验证据和理论表明，气候变暖和干旱事件的频率和持续时间的增加将改变淡水生态系统的代谢平衡。然而，气候变化对生态系统代谢的影响可能取决于能量输入是本地来源还是外来来源。迄今为止，很少有研究探讨变暖和干旱如何相互作用以改变河流代谢，更不用说它们的影响如何取决于食物网的能量基础。我们利用室外围隔生态系统进行了一项多因子实验，以研究变暖和干旱对绿色溪流围隔生态系统代谢过程的单独和协同效应（藻类为基础的）vs.混合（藻类和碎屑为基础的）vs.棕色（碎屑为基础的）能量途径。我们设置了48个中型生态系统，其中有三种不同水平的树荫和落叶输入组合，以创建具有不同主要能量通道的中型生态系统。此外，我们将一半的中型生态系统加热了约2-3°C。我们评估了在24天的干燥事件之前和复湿之后，生态系统呼吸（ER），总初级生产力（GPP），净生态系统生产力（NEP）和有机物质生物量在温暖和环境温度的围隔生态系统中的变化。然而，干燥导致ER和GPP的速率降低，并导致NEP的总体降低。虽然干燥的影响是类似的跨能源通道治疗，减少ER和GPP主要是由底栖和丝状algebraf. Overall生物量的减少，我们表明，干燥导致较低的NEP率在围隔生态系统中，无论能量输入。虽然变暖在我们的研究中几乎没有影响，但我们的研究结果表明，河流干燥事件频率的增加可能会极大地改变许多水生生态系统的代谢平衡。
Empirical evidence and theory suggest that climate warming and an increase in the frequency and duration of drying events will alter the metabolic balance of freshwater ecosystems. However, the impacts of climate change on ecosystem metabolism may depend on whether energy inputs are of autochthonous or allochthonous origin. To date, few studies have examined how warming and drying may interact to alter stream metabolism, much less how their impacts may depend on the energy‐base of the food web.To address this research gap, we conducted a multi‐factorial experiment using outdoor mesocosms to investigate the individual and synergistic effects of warming and drought on metabolic processes in stream mesocosms with green (algal‐based) vs. mixed (algal‐ and detritus‐based) vs. brown (detritus‐based) energy pathways.We set up 48 mesocosms with one of three different levels of shade and leaf litter input combinations to create mesocosms with different primary energy channels. In addition, we warmed half of the mesocosms by ~2–3°C. We assessed changes in ecosystem respiration (ER), gross primary production (GPP), net ecosystem production (NEP) and organic matter biomass in warmed and ambient temperature mesocosms before a 24 day drying event and after rewetting.Surprisingly, experimental warming had little effect on metabolic processes. Drying, however, led to decreased rates of ER and GPP and led to an overall reduction in NEP. Although the effects of drying were similar across energy channel treatments, reductions in ER and GPP were primarily driven by decreases in biomass of benthic and filamentous algae.Overall, we demonstrate that drying led to lower rates of NEP in mesocosms regardless of energy inputs. While warming showed little effect in our study, our results suggest that an increase in the frequency of stream drying events could greatly alter the metabolic balance of many aquatic ecosystems.Read the free Plain Language Summary for this article on the Journal blog.