The beneficial effects of plant roots in decreasing soil detachment in forest ecosystems exposed to rill erosion are well known. However, these effects vary largely between different plant species. There has been lots of research into the relationship between root-soil systems and rill erodibility with a particular focus on grass species. Conversely, fewer studies are available for tree species, especially in forests of semi-arid or arid environments. Greater knowledge is therefore needed to identify the most effective tree species against rill erosion in these ecosystems, where water availability is the limiting factor for vegetation growth and afforestation is often the only solution to control erosion. To fill this gap, this study evaluates the rill detachment capacity of soils with four tree species (Parrotia persica, Carpinus betulus, Quercus castaneifolia, and Pinus taeda) in a semi-arid forest ecosystem in Northern Iran. These species are typical of these forests, but they also grow in other environmental contexts. The rill detachment was simulated in a laboratory flume at five slope gradients (1% to 5%) and five flow rates (0.22 to 0.69 L m⁻¹ s⁻¹) on soil samples with each of the tree species. The specific goal of the study was to evaluate which tree species with its specific root characteristics is most effective at reducing the rill detachment capacity. Moreover, simple prediction models are proposed to evaluate if it is possible to estimate the rill detachment capacity and rill erodibility (K_r) from the unit stream power for the investigated tree species. The soils with Parrotia persica and Carpinus betulus showed the lowest and the highest rill detachment capacity, respectively. The greater root system biomass of Parrotia persica could have played a binding effect on the soil, thus improving its aggregate stability thanks to the action of plant's root system. Based on these results, Parrotia persica is able to provide a higher soil protection capacity against erosion compared to the other tree species. A logarithmic function was accurate in predicting the rill detachment capacity from the unit stream power at water flow rates over 0.0025 m s⁻¹. By a regression between the rill detachment capacity and the shear stress of the soil, rill erodibility and critical shear stress of soils were estimated for the four tree species; the rill erodibility and critical shear stress are important input parameters for physically-based erosion models. Overall, the results of this study can support land planners in the choice of tree species most indicated for soil conservation as well as in the extensive application of erosion prediction models.

众所周知，植物根系在减少遭受小溪侵蚀的森林生态系统中减少土壤脱离方面的有益作用。但是，这些影响在不同植物物种之间差异很大。关于根-土壤系统与小溪易蚀性之间关系的研究很多，特别是草种。相反，针对树种的研究较少，特别是在半干旱或干旱环境的森林中。因此，在这些生态系统中，需要更多的知识来确定最有效的树种以防小溪侵蚀，那里的水供应是植被生长的限制因素，而造林通常是控制侵蚀的唯一解决方案。为了填补这一空白，本研究评估了四种树种的土壤的小溪分离能力（伊朗北部半干旱森林生态系统中的百日草，百子锦，桔小栎和松树（taeda taeda）。这些物种是这些森林的典型特征，但它们也在其他环境中生长。在实验室水槽中以每种树种在土壤样品上以五个坡度梯度（1％至5％）和五个流速（0.22至0.69 L m ^-1  s ^-1）模拟小溪分离。该研究的具体目标是评估哪种具有其特定根部特征的树种最有效地降低了小溪的分离能力。此外，提出了简单的预测模型来评估是否有可能估算钻头的分离能力和钻头的侵蚀性（K _r）从被调查树种的单位流功率中得出）。与土壤Parrotia桃和鹅betulus分别显示的最低和最高的小溪支队能力。百日草的更大的根系生物量可能对土壤产生了结合作用，因此由于植物根系的作用而提高了其总体稳定性。基于这些结果，Perrotia persica能够提供比其他树种更高的土壤侵蚀防护能力。在水流量超过0.0025 m s ^-1时，对数函数可准确地根据单位流功率预测小河的分离能力。通过小溪的分离能力和土壤的剪切应力之间的回归，估算了四种树种的小溪可蚀性和土壤的临界剪切应力。钻蚀性和临界切应力是基于物理的侵蚀模型的重要输入参数。总的来说，这项研究的结果可以为土地规划师提供选择最适合土壤保护的树种以及广泛使用侵蚀预测模型的支持。