Streams draining forested landscapes are fuelled by terrestrial plant litter, which can be transported downstream or retained and broken down locally. However, fluxes of plant litter in streams can vary at multiple spatio‐temporal scales, affecting the availability of this key resource in heterotrophic stream food webs. To explore this question we quantified several processes related to litter dynamics (i.e. litter inputs, storage, losses by transport and losses by breakdown) by sampling litter at multiple sites in three streams of the Brazilian Cerrado biome (which has a tropical wet–dry climate) for 2 years. We assessed the relative contribution of different spatial (among and within streams) and temporal scales (annual, seasonal and monthly) to total variability of these processes (hereafter fluxes). Spatial and temporal variability of fluxes were both high, but spatial variation was 1.67‐fold greater than temporal variation (61 versus 37%, respectively), especially at the within‐stream scale (50% overall); an exception was litterfall, which varied less spatially than temporally (24 versus 76%). Temporal variation of litter storage (and hence availability to consumers) was mostly seasonal and due to differences in net transport. Inputs and transport were higher in the wet than the dry season (wet versus dry season, 1.45 versus 0.92 and 1.43 versus 0.06 g litter m⁻² day⁻¹), while breakdown was similar between both seasons (0.88 versus 0.94 g litter m⁻² day⁻¹). Storage (i.e. accumulation) rate was positive and negative in the dry and wet season, respectively, indicating that litter was stored in the dry season and exported in the wet season. The transitional dry–wet season showed the highest inputs, breakdown and storage (3.21, 1.63 g litter m⁻² day⁻¹ and 145 g litter m⁻²), while the wet–dry season showed lower inputs (as in the dry season), higher transport (as in the wet season) and lower breakdown and storage than the other seasons (0.93, 0.65, 0.31 g litter m⁻² day⁻¹ and 24 g litter m⁻²). Our results underscore the role of variation in biophysical drivers of litter fluxes within streams (e.g. pool–riffle configuration, substrate features, biological communities), and suggest that high within‐stream replication is necessary to study litter fluxes at larger scales and over time. The seasonal patterns suggested potential changes in litter dynamics under future climate scenarios in the tropics, including increased storage due to reduced transport in a drier climate.

中文翻译：

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需要高度的河流内复制来预测干湿热带河流中的凋落物通量

流经森林景观的溪流由陆生植物凋落物提供燃料，这些植物凋落物可以向下游运输或在当地保留和分解。然而，河流中植物凋落物的通量可以在多个时空尺度上变化，影响异养河流食物网中这一关键资源的可用性。为了探讨这个问题，我们通过在巴西塞拉多生物群落（具有热带干湿气候）的三个溪流中的多个地点采样垃圾，量化了与垃圾动态相关的几个过程（即垃圾输入、储存、运输损失和分解损失） ) 2 年。我们评估了不同空间（溪流之间和溪流内）和时间尺度（年度、季节性和月度）对这些过程的总变异性（以下称为通量）的相对贡献。通量的时空变异性都很高，但空间变异性是时间变异性的 1.67 倍（分别为 61% 和 37%），尤其是在河流内尺度（总体为 50%）；一个例外是凋落物，它在空间上的变化小于时间上的变化（24% 对 76%）。垃圾储存量（以及消费者的可用性）的时间变化主要是季节性的，并且是由于净运输的差异。雨季的投入和运输高于旱季（雨季与旱季，1.45 与 0.92 和 1.43 与 0.06 克垃圾 m⁻² 天⁻¹），而两个季节之间的分解相似（0.88 与 0.94 克垃圾 m⁻ ² 天⁻¹）。干、湿季贮藏（即堆积）率分别为正负，说明凋落物在旱季储存，在雨季输出。干湿过渡季节的投入、分解和储存量最高（3.21、1.63 克垃圾 m⁻² 天⁻¹ 和 145 克垃圾 m⁻²），而干湿季节的投入较低（如旱季)，比其他季节（0.93、0.65、0.31 克垃圾 m⁻² 天⁻¹ 和 24 克垃圾 m⁻²）更高的运输（如在雨季）和更低的分解和存储。我们的结果强调了溪流内凋落物通量的生物物理驱动因素变化的作用（例如池-浅滩构造、底物特征、生物群落），并表明在更大规模和随着时间的推移研究凋落物通量时，必须进行高度的溪流内复制。季节性模式表明，在热带地区未来的气候情景下，垃圾动态可能会发生变化，包括由于干燥气候下运输减少而导致的储存量增加。