Leaf litter breakdown is an important process in riparian ecosystems, regulated by the concomitant fluctuations of allochthonous organic matter input (quality and quantity), the environmental conditions, and the decomposer community. Our objective was to assess the effects of temporal variability of litter quantity and quality over the stream’s decomposer community. We hypothesized that the litter effects over the decomposer community would be overruled by Cerrado’s harsh environmental conditions. Precipitation fluctuations, especially during dry and rain seasons, did modify the litterfall periodicity, but not the average organic matter entering the system or the litterfall triggers. Fifteen riparian species were identified contributing with organic matter into the stream, however, Richeria grandis contributed with 48% of litter biomass, helping explain the nutritional intra-annual balance given by the litter chemistry, that would be determinant for ecosystem stability. Higher aquatic hyphomycetes sporulation rates and invertebrate density during the dry season suggest that the decomposer community required a more stable environment (consistent low current) in order to colonize and exploit leaf litter. Our results point out that physical fragmentation was the predominant driver of litter breakdown for our system, due to high decomposition rates, litter remaining mass correlated negatively with precipitation, and low decomposer abundance and activity. Invertebrate collectors’ abundance was negatively correlated with litter remaining mass and showed no temporal variation, suggesting that this functional group may have benefited from the particulate organic matter produced by physical fragmentation. Therefore, annual temporal variations on Brazilian savanna stream systems may drive the functioning of the ecosystem.

中文翻译：

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巴西热带稀树草原流中有机质，疏水菌和无脊椎动物群落的时间动态

凋落物分解是河岸生态系统中的一个重要过程，受到异源有机物输入（质量和数量），环境条件和分解者群落的伴随波动的调节。我们的目标是评估垃圾分解量和质量在河流分解者群体中随时间变化的影响。我们假设，塞拉多恶劣的环境条件将推倒垃圾在分解者社区的影响。降水的波动，尤其是在干燥和雨季期间，的确改变了凋落物的周期性，但没有改变进入系统的平均有机物或凋落物的触发因素。共有15种河岸物种被发现与有机物质一起进入河中，但是，大红Rich贡献了48％的凋落物生物量，帮助解释了凋落物化学成分提供的营养年内平衡，这将决定生态系统的稳定性。干旱季节较高的水生菌丝孢子形成率和无脊椎动物密度表明，分解菌群落需要更稳定的环境（一致的低电流）才能定居和利用枯枝落叶。我们的研究结果表明，物理碎片是垃圾分解的主要驱动力，原因是分解速率高，垃圾残留量与降水呈负相关，分解剂的丰度和活性低。无脊椎动物收集者的丰度与垫料剩余质量呈负相关，并且没有时间变化，这表明该官能团可能已经受益于物理裂解产生的颗粒状有机物。因此，巴西热带稀树草原河流系统的年度时间变化可能会驱动生态系统的功能。