1. Coarse particulate organic matter (CPOM) is a fundamental resource in freshwater streams, providing food, shelter and habitat for diverse invertebrate taxa and playing a key role in metabolism in low‐order streams. Benthic CPOM stocks are determined by rates of supply and breakdown of detritus and by channel retentiveness (i.e. the capacity for the channel to trap and retain CPOM). We focussed on factors affecting the retentiveness of channels, which theoretically differs among streams with different sediment sizes and concomitant channel morphology.
2. We developed a new, rapid method to measure retentiveness using line‐intercept surveys along transects. With this rapid approach, we surveyed 32 sites from three types of streams (smooth sandy channels, n = 10; gravel channels of intermediate roughness, n = 12; rough cobble channels, n = 10) in Victoria, south‐eastern Australia, and tested the simple hypotheses that: (1) retentiveness increases in channels with increasing channel roughness (i.e. sandy versus gravel versus cobble‐bed streams); (2) different types of channel features (e.g. log jams, cobbles, depositional areas) differ in the efficiency with which they retain CPOM. The line‐intercept survey method was readily adapted to measure retentiveness as m of retentive structure per m of transect (i.e. the Linear Coverage Index) and trapping efficiency as m of CPOM per m of retentive element, for 10 different types of retentive elements.
3. Unexpectedly, the retentiveness of channels did not increase with channel roughness. This occurred because channels with different roughness were dominated by different types of retentive structure. Retentive structure in cobble sites was dominated by cobbles themselves, which were highly retentive in other studies but poorly retentive in our system. Gravel and sand sites had more log jams and depositional areas, such as pools and backwaters, and these features were more effective at trapping CPOM. Thus, retention of CPOM was highest in gravel and sand sites.
4. Our method provides a new tool for investigators testing hypotheses about CPOM retention in streams. The method is rapid, requires a minimum of equipment and personnel, and may be applied in any wadeable stream. Retentiveness is calculated in intuitive units that are directly comparable among sites and may have utility as variables in models of CPOM dynamics. We hope this method will open up new avenues for research that may shed light on how CPOM stocks vary among streams, with implications for diversity of aquatic fauna and ecosystem functions such as decomposition.

中文翻译：

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一种新颖的方法揭示了河床保持力和碎屑储量（CPOM）在床层粗糙度不同的流之间如何变化

1. 粗颗粒有机物（CPOM）是淡水流中的基本资源，可为各种无脊椎动物类群提供食物，庇护所和栖息地，并在低序流中的新陈代谢中发挥关键作用。底栖CPOM的存量取决于碎屑的供应和分解速度以及渠道的保持力（即渠道捕获和保留CPOM的能力）。我们关注于影响通道保持力的因素，这些理论上在具有不同沉积物尺寸和伴随通道形态的河流之间是不同的。
2. 我们开发了一种新的快速方法，可使用沿断面的线截距测量来测量保持力。采用这种快速方法，我们从三种类型的河流中调查了32个站点（光滑的沙质通道，n  = 10；中等粗糙度的砾石通道，n  = 12；粗糙的卵石通道，n = 10）在澳大利亚东南部的维多利亚州，并检验了以下简单假设：（1）随着河道粗糙度的增加（例如，沙土，砾石，鹅卵石床流），河道中的保持力增加；（2）不同类型的通道特征（例如，原木堵塞，卵石，沉积区域）在保持CPOM的效率上有所不同。线截距调查方法很容易适用于测量10种不同类型的保持元件的保持力，即每m个断面的保持结构的m（即线性覆盖指数）和捕集效率，即每m个保持元件的CPOM的m。
3. 出乎意料的是，通道的保持力并未随通道的粗糙度而增加。发生这种情况是因为具有不同粗糙度的通道被不同类型的保持结构所支配。卵石部位的保持结构主要由卵石本身决定，这些卵石在其他研究中具有很高的保持力，但在我们的系统中却保持能力差。砾石和砂石场地的木塞堵塞和沉积区域（如水池和死水）较多，这些特征在捕获CPOM方面更有效。因此，CPOM在砾石和砂土部位的保留率最高。
4. 我们的方法为研究人员测试有关流中CPOM保留的假设提供了一种新工具。该方法是快速的，需要最少的设备和人员，并且可以在任何可涉水流中应用。保持性是以直观单位计算的，这些单位可以在站点之间直接比较，并且可以用作CPOM动态模型中的变量。我们希望这种方法将为研究开辟新的途径，以阐明CPOM种群在溪流之间如何变化，从而对水生动物多样性和生态系统功能（例如分解）产生影响。