Purpose

Soil erosion is a major threat to agricultural sustainability in the hills of Nepal. However, little is known about the soil erosion rates at a small catchment scale in this region.

Materials and methods

In this study, the soil redistribution rates in a typical small hilly catchment in the Ramechhap District of Nepal were evaluated using the ¹³⁷Cs and ²¹⁰Pb_ex tracer techniques. Nine representative slopes under three land uses and a reference site from the gentle sloping forest land within the catchment were selected as sample plots. A downhill transect was built in each sample plot, and soil samples were collected at 5-m intervals along the transects.

Results and discussion

The results showed that the spatial variations in radionuclide inventory and soil erosion rates measured by ¹³⁷Cs measurements were highly consistent with equivalent estimates from ²¹⁰Pb_ex measurements, suggesting the potential for using ¹³⁷Cs and ²¹⁰Pb_ex measurements to estimate soil redistribution rates. All ¹³⁷Cs and ²¹⁰Pb_ex inventories on the slopes were less than the reference values, indicating that net soil loss has occurred at all of the sampling points. The net erosion rates from sloping farmland (37.08 t ha⁻¹ year⁻¹) and shrub land (32.52 t ha⁻¹ year⁻¹) were significantly higher than those from forest land (14.91 t ha⁻¹ year⁻¹). Furthermore, the soil erosion rates obtained from ²¹⁰Pb_ex measurements were higher than those obtained from ¹³⁷Cs measurements, which implies that soil erosion in the catchment was accelerated during the last two decades. The net soil loss from the study catchment was estimated to be 31.29 t ha⁻¹ year⁻¹, which is mainly contributed by shrub land (55.08%) and sloping farmland (37.68%).

Conclusions

These results indicate that shrub land and sloping farmland are vulnerable to erosion, which should be specifically considered in the sustainable management of small agricultural catchments in the mid-hills of Nepal, especially in dry valley regions.

中文翻译：

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使用137 Cs和210 Pb ex追踪尼泊尔中部小流域的土壤侵蚀速率

目的

水土流失是尼泊尔丘陵地区农业可持续发展的主要威胁。但是，对该地区小流域的土壤侵蚀率知之甚少。

材料和方法

在这项研究中，使用¹³⁷ Cs和²¹⁰ Pb _ex示踪剂技术评估了尼泊尔Ramechhap区一个典型的小山丘流域的土壤再分配速率。选择了三种土地利用下的九个代表性坡度和流域内缓坡林地的参考点作为样地。在每个样地中都建立了一个下坡样带，并沿样带以5 m的间隔收集土壤样品。

结果和讨论

结果表明，通过¹³⁷ Cs测量得到的放射性核素清单和土壤侵蚀速率的空间变化与²¹⁰ Pb _ex测量的等效估计高度一致，这表明使用¹³⁷ Cs和²¹⁰ Pb _ex测量来估算土壤再分配速率的潜力。所有的¹³⁷ Cs和^210个铅_前的山坡上库存均低于基准值，表明在所有的采样点已发生净土壤流失。坡耕地（37.08 t ha ^-1 year ^-1）和灌丛土地（32.52 t ha的净侵蚀率^-1年^-1）显着高于林地（14.91 t ha - ¹年^-1）。此外，从²¹⁰ Pb _ex测得的水土流失率高于从¹³⁷ Cs测得的水土流失率，这表明在过去的二十年中流域的土壤侵蚀加速了。研究集水区的土壤净损失估计为31.29 t ha ^-1 year ^-1，主要由灌木土地（55.08％）和坡耕地（37.68％）造成。

结论

这些结果表明，灌木林地和坡地易受侵蚀，在尼泊尔中部山区，特别是干旱谷地地区的小型农业集水区的可持续管理中应特别考虑这一点。