Purpose

Soil erosion and loss threatens vast tracts of agricultural and non-agricultural land, worldwide. High soil erosion severely affects establishment of vegetation via effects on plant growth and productivity on already degraded lands. However, information on soil loss impact on tree plantation and their relationships is scarce in the ravine lands. Therefore, we assessed soil loss effects on tree growth and soil characteristics, and role of conservation measures in degraded ravine land.

Methods

The study consisted of comparing three systems, i.e., terracing, trenching, and sole slope to observe the effects on soil erosion and the resultant losses. In first system, a terraced land was designed from ravine top to bottom by dividing the slope into the four plots. In second system, ninety-seven trenches sized 2.0 m × 0.5 m × 0.5 m were designed on slope, while in third system, a continuous slope was maintained. Twenty-seven trees were planted at 8 m × 8 m spacing in each system. In all the systems, annual runoff, soil loss, tree growth, biomass and carbon stock, and soil properties were observed for the 7 years.

Results

Annual soil loss was recorded highest (5.1 t ha⁻¹ year⁻¹) in slope followed by trench (4.4 t ha⁻¹ year⁻¹) and terrace (3.8 t ha⁻¹ year⁻¹) systems, during the 7 years. In the slope system, increased soil loss resulted in the decreased tree height and collar diameter growth by 3–12% and 12–21%, respectively. Total biomass, carbon stock, and CO₂ sequestration declined by 44–86% with the increased soil loss on the slope during the same period. Tree canopy area was also recorded lower in the slope, compared to terrace and trench measures. The soil loss relationship with tree characteristics revealed that growth, biomass, carbon stock, and canopy area consistently declined with the increased soil loss. In soil, proportional loss of organic carbon (11–21%), nitrogen (10–13%), phosphorus (25–32%), and potassium (4–13%) was also observed with increased soil erosion on the slope, compared to conservation measures. In contrast, soil loss reduction in the terrace and trench based measures improved the tree growth, biomass, carbon stock, and soil properties during the same period.

Conclusion

The soil loss negatively affected the tree growth, productivity and their restoration potential, while soil conservation measures showed strong potential to ameliorate the highly eroded ravine slopes. Therefore, tree plantations should be augmented with the appropriate soil and water conservation measures for achieving greater ecological and economic benefits in degraded ravine lands.

中文翻译：

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水土流失阻碍了高度侵蚀的山坡上树木的恢复潜力

目的

水土流失和损失威胁着全世界范围广泛的农业和非农业用地。高水土流失通过影响已经退化土地上的植物生长和生产力，严重影响植被的建立。然而，在沟壑地区，关于水土流失对人工林及其关系的影响的信息很少。因此，我们评估了土壤流失对树木生长和土壤特性的影响，以及保护措施在退化的沟壑地带中的作用。

方法

该研究包括比较三个系统，即梯田，开沟和单一坡度，以观察对土壤侵蚀的影响和由此造成的损失。在第一个系统中，通过将坡度分为四个地块，从山沟的顶部到底部设计了梯田。在第二个系统中，在坡度上设计了97个尺寸为2.0 m×0.5 m×0.5 m的沟槽，而在第三个系统中，则保持了连续的坡度。在每个系统中，以8 m×8 m的间隔种植了27棵树。在所有系统中，都观察到了7年的年径流量，土壤流失，树木生长，生物量和碳储量以及土壤性质。

结果

在这7年中，坡度的年度土壤流失量最高（5.1 t ha - ¹ 年^-1），其次是沟渠（4.4 t ha - ¹ 年^-1）和梯田（3.8 t ha - ¹ 年^-1）。在斜坡系统中，土壤流失的增加导致树木高度和衣领直径的增长分别降低了3–12％和12–21％。总生物量，碳储量和CO ₂在同一时期，由于坡地土壤流失的增加，固存量下降了44–86％。与梯田和沟渠措施相比，树冠区域的坡度也较低。土壤流失与树木特征的关系表明，随着土壤流失的增加，生长，生物量，碳储量和冠层面积持续下降。在土壤中，随着坡度土壤侵蚀的增加，还观察到有机碳（11–21％），氮（10–13％），磷（25–32％）和钾（4–13％）的比例损失，与保护措施相比。相反，基于梯田和沟渠的措施减少了土壤流失，在同一时期改善了树木的生长，生物量，碳储量和土壤性质。

结论

水土流失对树木的生长，生产力及其恢复潜力产生负面影响，而土壤养护措施则显示出改善高度侵蚀的山坡的巨大潜力。因此，应在人工林中增加适当的水土保持措施，以在退化的沟壑地带获得更大的生态和经济效益。