摘要
应用时空转换的方法,研究了黑土区自然草地开垦为农田后,在随后2-100年的耕作中1m土层土壤持水能力、C、N储量的变化。结果表明:由自然土壤-植被系统转化为人工农田系统后,黑土储水量减少17.6%-30.8%;对土壤碳库影响是缓慢的,1m土层的碳库储量100年来减少了23.71%;在0-50cm土层中氮素变化与碳库变化相似,但在50-100cm土层氮库100年来变化不大。土地利用与覆盖变化对水土流失效果显著,人工农田系统较自然生态系统多流失水27t/hm2,土为38t/hm2。在这些变化中,时间的作用是缓慢的,不占主导地位,仅起辅助作用,而土地利用/土地覆盖方式起到决定性作用。
Black soils, located mainly in Heilongjiang and Jilin provinces of China, cover a broad area from 43° to 48°N and from 124° to 127°E, with a total area of 5.93 × 106 ha. The black soils were cultivated about 200 years in south, 50 years in north and 100 years in central parts of the black soil area. These soils are one of the most fertile soils in China. These soils were cultivated for a relatively short time as compared to the soils in southern China. The vegetation changed from natural vegetation to crop-weed, to rotation of corn-soybean-wheat, or to rotation of corn-soybean. Steppified herbosa were flourished in black soil area under the proper weather condition for plant growth where the precipitation of about 500mm to 600mm mainly from April to September is synchronized with heat. The water status has changed dramatically with the use of land. If we take the water storage in the depth of 1m in spring in natural soil under the Steppified herbosa vegetation as control, the water storage un- der crops decreased to 20.4% , 20.6% , 22.6% , 27.2% , 29.3% , 27.3% after 2, 8, 15, 30, 50, and 100 years cultivation, respectively. The decrease of water storage was around 17.6% to 30. 8% in summer investigation and about 19.7% to 29.9% in autumn measurement. According to the data from the three times measurement, we make a simulated calculation. The result showed that, the storage of water in this area was as high as a 24. 9 × 109t reservoir in spring. The storage of water has decreased to 19. 2 × 109 t after a hundred year cultivation. The impact of land use/cover on the soil water status is great. The capacity of land for storing water is decreased by 20% when cultivated for crops in contrast to natural soil. After the second year when the land was initially cultivated, the capacity decreased 6.9% every year with the cultivated time. So we concluded that the effect of soil use/cover is bigger than the time effect. The effect on black soil C pool of land use method and land cover is decisive, the C pool has a increase trend under original soil condition and steppified herbosa, it will decrease when black soil were reclaimed from its original state to farmland covered with crops. Compared with the capacity on soil C pool in 1 m soil layer under original soil condition and steppified herbosa, however, the organic C pool were decreased slowly by 23.71% on farmland after cultivation of 100 years. Plants need nitrogen as a macro-element. Method of land use and land cover affected the N pool in black soil in the same trend as for the C pool. Nevertheless the change in C pool in the layer from 50cm to 100cm is not significant in the period of 100 years; it is expected that much longer time is needed to have a significant change. It is land use/cover that makes tremendous influence on water and soil losses, but there is a litde relationship of water and soil losses with the cultivation time. Compared with the original soil and natural vegetation, the annual water loss of reclaimed farmland increased 27t/( ha·a) ; and there are as much as 50. 93 × 106 t of water loss for the whole black soil area. Also the annual soil loss of reclaimed farmland increased about 38 t/ha; and there are 78. 87 × 106 t soil loss for the whole black soil area. The over-cultivation not only resulted in the soil and water loss but also deteriorated the human living environment.
出处
《地理科学》
CSCD
北大核心
2005年第2期203-208,共6页
Scientia Geographica Sinica
基金
中国科学院资源环境领域知识创新工程重要方向项目(KZCX2-320-2
KZCX2-416-3)。
关键词
土地
覆盖
黑土
生态
影响
land use
land cover
black soil
ecology
