Sediment dynamics in river catchments are controlled by tectonics, climate, and biota effecting material production on hillslopes and transport of sediment from their source to the catchment outlet. Tectonics create topography and control erodibility of the bedrock material, whereas climate controls the efficiency of weathering and transporting processes. In contrast, the effects of biota (i.e. vegetation) are more ambiguous. Vegetation accelerates bio-chemical weathering and effects mass wasting through uprooting, trapping and stabilizing hillslope material. Furthermore, vegetation exerts a strong control on the grain size distribution of hillslope sediments and thus on sediment rooting through catchments.

In this study we compare grain size distributions of hillslope and channel sediments collected in four headwater catchments located in the Chilean Coastal Cordillera covering a strong bio-climatic gradient. 76 volumetric bulk samples were taken with grain sizes ranging from clay (d = 0.3 μm) to boulders (d > 300 mm).

Results show that the production of fine material is strongly dependent on bio-chemical weathering intensity and hence humidity. The coarse fraction in hillslope material and channel sediments increases from arid to sub-humid conditions, presumably reflecting a higher intensity of mass wasting processes. Channels show varying degrees of armouring reflecting nonselective and thus transport-limited conditions under arid climate that are contrasted by relatively well sorted and armoured channel sediments in the humid and vegetated catchments, indicating size selective and supply-limited transport conditions. Channel grain sizes generally show high similarity to hillslope grain sizes of the same catchment, revealing the strong dependency of channel sediments on hillslope supply, at least in headwater catchments, transferring a bio-climatic control from the hillslopes to the channel system.

河流集水区的泥沙动力学受构造，气候和生物区系的控制，影响着山坡上的物质生产以及沉积物从其源头到集水口的运输。构造创造了地形并控制了基岩材料的可蚀性，而气候则控制着风化和运输过程的效率。相反，生物区系（即植被）的影响更为模糊。植被加速了生化风化，并通过连根拔起，诱捕和稳定山坡材料而造成大量浪费。此外，植被对山坡沉积物的粒径分布有很强的控制作用，因此对通过集水区生根的沉积物也有很大的控制作用。

在这项研究中，我们比较了位于智利沿海科尔迪勒拉的四个覆盖有强烈生物气候梯度的源头集水区的山坡和河道沉积物的粒度分布。采集了76份体积大的样品，其粒度范围从粘土（d = 0.3μm）到巨石（d> 300 mm）。

结果表明，精细材料的生产强烈依赖于生物化学风化强度以及湿度。从干旱到半湿润的条件下，山坡材料和河道沉积物中的粗颗粒增加，这可能反映了更大的物质浪费过程强度。河道显示出不同程度的装甲，反映了干旱气候下非选择性的运输受限条件，而在湿润和植被丰富的流域中，相对分类良好的装甲河道沉积物形成对比，表明了大小选择和供应受限的运输条件。河道粒度通常与同一流域的山坡粒度高度相似，这表明，至少在上游水源流域，河道沉积物对山坡供应的依赖性很大，