摘要:
对世界银行贷款“贫困地区林业发展项目”8个项目省(区)新建经济林和垦复竹林地中设置的11个土壤侵蚀定位观测点,连续5年(2001—2005年)观测得到的数据进行了综合分析。结果表明:各经济林地和竹林地在造林或垦复后均发生了不同程度的土壤侵蚀,在11个观测点中,6个观测点发生了微度土壤侵蚀或轻度土壤侵蚀,位于黄土地貌区的3个观测点土壤侵蚀强度较大,个别年份受高强度侵蚀性降雨的影响,发生了强度土壤侵蚀。梯田类整地方式的经济林地观测点土壤侵蚀量较小,水平带及穴状整地方式观测点的土壤侵蚀较为严重;造林后连续间作的经济林每年均发生土壤侵蚀,侵蚀模数随年度无明显变化,对于前4年进行间作,然后停止间作的经济林,土壤侵蚀量急剧下降,在水平带及穴状整地的经济林内进行农作物间作会导致中、强度土壤侵蚀的发生。垦复竹林观测点的土壤侵蚀模数较小,垦复后第1年易发生侵蚀,侵蚀量随林下植被恢复逐年减小,冬笋采挖会导致土壤侵蚀量的增加。建议新建经济林时,尽量采用梯田整地方式,而少用带状和穴状(包括鱼鳞坑)整地方式。梯田整地营建的经济林中可适当进行间作,带状整地和穴状整地经济林则不宜。毛竹低产林垦复改造施工的第1年,应采取沿等高线垦挖、杂草覆盖地表等措施防止土壤侵蚀。
关键词:
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经济林
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造林
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竹林垦复
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土壤侵蚀
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定位观测
Abstract:
A comprehensive analysis was made on the five-year monitoring data of 11 fixed soil erosion monitoring sites of newly established cash crop tree plantations and rehabilitated bamboo forests in eight provinces or autonomous regions of China, which were constructed under the Forestry Development in Poor Area Project (FDPA) financed by the World Bank. The results show that the afforestation and cultivation operations for the cash crop tree plantations and rehabilitated bamboo forests have resulted in soil erosion, but to different degrees. Within the 11 soil erosion monitoring sites, extremely slight or slight soil erosion occurred in six sites and severe soil erosion in three sites during years of frequent and intensive rainfall or on Ioess hills. The occurrence of soil erosion was lighter on planting sites with broad terrace preparation than on sites with strip or hole preparation. Soil erosion occurred annually on planting sites with continuous intercropping, which showed similar soil erosion modulus. But soil erosion decreased to an extremely low level when, after four years of continuous intercropping, the intercropping stopped. Intercropping also caused relatively strong soil erosion on slope planting sites with strip or hole preparation. For the rehabilitated bamboo forests, soil erosion occurred but in small soil erosion modulus and usually occurred during the first year after rehabilitation and decreased annually with the gradual recovery of undergrowth vegetation. The bamboo shoot harvest in winter increased the occurrence of soil erosion. It is recommended that in the newly established cash crop tree plantations, the best preparation method is by broad terrace type, while avoiding strip or hole preparation. Intercropping can be used under suitable conditions in newly established cash crop tree plantations with broad terrace preparation. For the rehabilitation of low productive bamboo forests, several measures can be adopted to prevent soil erosion, i.e. digging the soil along contours, covering the ground with weeds.
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