黄土塬区土壤水分分布特征及其对不同土地利用方式的响应

    Soil moisture distribution in deep layers and its response to different land use patterns on Loess Tableland

    • 摘要: 该文就陕西省长武黄土塬区主要土地利用方式下0~20 m土壤剖面水分分布特征及其与土壤质地的关系进行了调查与分析,以期服务于土地利用方式的优化配置及区域水文水资源研究。结果表明,黄土剖面古土壤层物理黏粒含量较黄土层高约2%~6%,质地较重;0~20 m剖面田间持水率和萎蔫湿度分别为(21.39±0.13)%和(8.06±0.45)%。黄土深层土壤水分分布特征与黄土-古土壤序列有关,一般情况下,一层黄土和一层古土壤构成一次湿度高低起伏,并有随深度增加湿度变大的趋势。荒草地、18年苹果园地、8年生及23年生苜蓿草地0~20 m土层平均湿度分别为18.89%、15.45%、14.77%和10.59%,连作高产小麦地0~13 m土层平均湿度为18.74%。高产麦田和荒草地3 m以下土层没有发生干燥化现象;18年苹果园地在10 m以上土层发生了中度和轻度为主的土壤干燥化现象;8年苜蓿草地在10 m以上土层发生了重度、中度和轻度的土壤干燥化现象,其中重度干燥化现象出现在4 m以上土层;而23年苜蓿在整个20 m土层都发生了重度和中度的土壤干燥化现象,其中重度干燥化现象出现在17 m以上土层。可以看出,高耗水型人工林草因水分负平衡所导致土壤干燥化,随年限增加渐进地向深层土层发展,这在苜蓿草地上表现的更为突出。

       

      Abstract: The characteristics of soil moisture distribution in 0~20 m loess profiles under different land use patterns and its relations with soil texture on the Changwu Loess Tableland were investigated for the optimal allocation of land use patterns and the study of regional hydrology and water resources. Results showed that physical clay in soil layers of red-brown paleosol was 2%-6% higher than in loess layers. Field capacity and wilting point were (21.39±0.13)% and (8.06±0.45)%, respectively. The characteristics of soil moisture distribution in deep layers were related to the loess- paleosol sequences. Generally, one paleosol layer and one loess layer constituteda up-down humidity level and there was an increasing trend in soil moisture with increased depth. The average soil moisture contents in the loess profiles in grassland was measured, 18-yr apple orchard, and 8-yr and 23-yr planted alfalfa grasslands were 18.89%, 15.45%, 14.77%, and 10.59%, respectively. The average soil moisture content at 0-13 m layer in high-yield wheat field was 18.74%. There was no soil desiccation below the depth of 3 m in high-yield wheat field and grassland. In 18-yr apple orchard, soil desiccation occured in the upper 10 m of the profile, being mainly moderate desiccation and light desiccation. In 8-yr planted alfalfa grassland, soil desiccation occured above 10 m of the profile, being severe desiccation, moderate desiccation, and light desiccation, and the severe desiccation occured above 4 m of the profile. In 23-yr planted alfalfa grassland, soil desiccation occured in the whole loess profile and the severe desiccation occured in the upper 17 m of the profile. The soil desiccation caused by negative water balance can gradually develop to deep soil layers with age in planted woodland and grassland and it is more prominent in alfalfa grassland.

       

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