Insects are major conduits of resources moving from aquatic to terrestrial systems. While the ecological impacts of insect subsidies are well documented, the underlying mechanisms by which these resources change recipient ecosystems remain poorly understood. Most subsidy inputs enter terrestrial systems as detritus; thus, soil microbes will likely influence the processing of insect subsidies, with implications for plant community composition and net primary productivity (NPP). In a subarctic ecosystem near Lake Mývatn, Iceland where midge (Diptera: Chironomidae) deposition to land is high, we investigated how insect subsidies affected litter processing and microbial communities. We also evaluated how those belowground effects related to changes in inorganic nitrogen, plant composition and NPP. We simulated subsidies by adding midge carcasses to 1-m² heathland plots, where we measured effects on decomposition rates and the plant community. We then studied how fertilization treatments (control, KNO₃ and midge-carcass addition) affected graminoid biomass and inorganic nitrogen in greenhouse experiments. Lastly, we conducted a soil-incubation study with a phospholipid fatty acid analysis (PLFA) to examine how midge addition to heathland soils affected microbial respiration, biomass and composition. We found that midge addition to heathland soils increased litter decomposition and graminoid plant cover by 2.6× and 2×, respectively. Greenhouse experiments revealed similar patterns, with midge carcasses increasing graminoid biomass by at least 2× and NH₄⁺ concentrations by 7×. Our soil-incubation study found that midge carcasses elevated microbial respiration by 64%, microbial biomass by 43% and shifted microbial functional composition. Our findings indicate that insect subsidies can stimulate soil microbial communities and litter decomposition in subarctic heathlands, leading to increased NPP and changes in plant community composition.

中文翻译：

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水生昆虫补贴影响近岸亚北极荒地的微生物组成和碎屑加工

昆虫是资源从水生系统转移到陆生系统的主要渠道。虽然昆虫补贴的生态影响有据可查，但这些资源改变受援生态系统的潜在机制仍然知之甚少。大多数补贴投入作为碎屑进入地面系统；因此，土壤微生物可能会影响昆虫补贴的处理，对植物群落组成和净初级生产力 (NPP) 产生影响。在冰岛米湖附近的亚北极生态系统中，蠓（双翅目：摇蚊科）在陆地上的沉积量很高，我们调查了昆虫补贴如何影响垃圾处理和微生物群落。我们还评估了这些地下效应如何与无机氮、植物成分和 NPP 的变化相关。我们通过将蠓尸体添加到 1 米来模拟补贴^{2 个}荒地地块，我们测量了对分解速率和植物群落的影响。然后，我们研究了施肥处理（对照、KNO ₃和蠓-胴体添加）如何影响温室实验中的禾本科生物量和无机氮。最后，我们使用磷脂脂肪酸分析 (PLFA) 进行了土壤培养研究，以检查向荒地土壤中添加蠓如何影响微生物呼吸、生物量和组成。我们发现，向荒地土壤中添加蠓类会使凋落物分解和禾本科植物覆盖率分别增加 2.6 倍和 2 倍。温室实验揭示了类似的模式，蠓虫尸体使禾本科生物量增加至少 2 倍，NH ₄ ⁺浓度增加 7 倍。我们的土壤孵化研究发现，蠓尸体将微生物呼吸提高了 64%，微生物生物量提高了 43%，并改变了微生物的功能组成。我们的研究结果表明，昆虫补贴可以刺激亚北极荒地的土壤微生物群落和凋落物分解，导致 NPP 增加和植物群落组成的变化。