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以黄土高原水蚀风蚀交错带不同退耕模式为研究对象,分析了不同模式退耕地(农地退耕后自然恢复草地、退耕后种植苜蓿和退耕后种植柠条)和相邻未退耕农地土壤有机碳和全氮含量的差异以及它们随退耕年限的动态变化.结果表明:不同退耕模式均能提高0~10cm土层土壤有机碳和全氮含量,但效果受退耕年限的影响.与相邻未退耕农地相比,退耕后自然恢复草地在演替10年时0~10 cm土层土壤有机碳和全氮含量不受影响,而在演替20年时均显著增加;退耕种植苜蓿后0~10 cm土层土壤有机碳和全氮含量分别增加51.6%~82.9%和43.4%~67.0%,其储量的增加速率分别为0.17~0.46和0.015~0.043 t·hm~(-2)·a~(-1),但不同退耕年限间差异不显著;退耕后种植柠条前20年土壤有机碳和全氮含量增加较多,退耕40年时增加量有所降低.农田退耕后种植柠条40年、苜蓿20年,其固存碳、氮的能力优于退耕后自然恢复草地,然而由于受土壤水分条件的限制和自身高耗水的特性,这2种退耕模式可能不具备长期的增碳、增氮能力.
Taking different patterns of returning farmland in the wind-water erosion ecotone in the Loess Plateau as the research object, the effects of different patterns of returning farmland (returning natural grassland after returning farmland to cultivated land, planting alfalfa after returning farmland and planting Caragana cultivating after returning farmland) and soil organic carbon And total nitrogen content and their dynamic changes with the years of returning farmland.The results show that the soil organic carbon and total nitrogen content in 0-10 cm soil layer can be improved by different modes of returning farmland but the effect is affected by the years of returning farmland, Compared with the farmland, the soil organic carbon and total nitrogen content in the 0 ~ 10 cm soil layer after the succession of 10 years of succession were not affected by natural restoration of grassland, but significantly increased after 20 years of succession; Soil organic carbon and total nitrogen in the 10 cm soil layer increased by 51.6% -82.9% and 43.4% -67.0%, respectively, and their rates of increase were 0.17-0.46 and 0.015-0.043 t · hm -2 · a ~ (-1), but there was no significant difference between different years of returning farmland to farmland. The contents of soil organic carbon and total nitrogen increased more significantly after the conversion of karst land to farmland in the first 20 years, Year, alfalfa 20 years, its ability to solidify carbon and nitrogen is better than natural recovery after returning farmland However, due to the limitation of soil moisture and their high water consumption, these two models may not have the long-term ability to increase carbon and nitrogen.