西安地区苹果林地与农田土壤水分变化研究

【作者】 李艳芳；

【导师】 赵景波；

【作者基本信息】 陕西师范大学 ， 环境科学， 2009， 硕士

【摘要】 黄土高原地处半湿润地区,降雨量偏少而集中,加之地下水埋藏深度大,使土壤水分在黄土高原的植被建设中显得尤为重要。地表的蒸发和植物的蒸腾,使得土壤水分出现亏损,部分植被下的土壤中出现了干层。土壤水分已成为制约西北生态环境建设的首要因子,也是制约该区农林业发展的重要因素。因此,研究人工植被下土壤-水环境对生态环境建设和农林业发展具有极其重要的意义。本文通过对黄土高原南部的西安地区不同人工植被下0～6m土壤含水量的测定,研究了该地区2008年农田和苹果林地土壤含水量的季节变化,区域差异,农田土壤水分的变化情况,苹果林地土壤水分的消耗过程等问题。本文研究的样品利用轻型人力钻采取,钻孔深度为6m,采样间距为10cm,每孔一般采样60个。土壤含水量的测定采用了被认为是准确可靠的烘干称重法。所选研究地点包括长安区郭杜镇大学城附近、少陵塬、咸阳庞西村和礼泉。所选人工植被有7龄、10龄、15龄苹果林,还有麦地和玉米地。通过对不同季节苹果林地和农田土壤含水量的测定与分析,得出了以下认识:（1）同一地点相同季节和相同降水条件下,不同人工植被土壤含水量是有差异的。在我们所选择的人工植被中,农田0～6m土壤平均含水量为16.95%,10龄苹果林地平均土壤含水量为14.61%,比农田减少了2.34%。在0～200cm、200～400cm和400～600cm农田的平均土壤含水量分别为14.63%、17.10%和19.12%,而10龄苹果林地分别为13.63%、15.01%和15.18%,比玉米地减少了1%、2.09%和4.36%。说明果树经济林比农田耗水多。（2）咸阳不同树龄果树林地土壤含水量存在明显差异。幼龄苹果林地土壤含水量明显高于中龄苹果林地含水量。但在相同地形条件下,6m深度范围内不同树龄苹果林地土壤水分随深度变化情况较为相似,总体上呈波动减小趋势。（3）在2008年秋季,少陵塬玉米地土壤含水量最高,大学城附近次之,庞西村最低。庞西村和礼泉中龄苹果林地土壤含水量都较低,分别为11.42%和12.94%,而且中龄苹果林在4m以下土壤含水量普遍小于12%,这充分说明该地区中龄苹果林下普遍存在干层。（4）西安地区近半个世纪以来气候趋于暖干化,但从2003年丰水年之后到现在,本区农田土壤含水量仍相当高,农田并无土壤干层发育,即使在冬小麦的耗水高峰期,农田土壤含水量仍然能够满足农作物生长的需求。这与近6年该区降水基本正常有关,表明土壤含水量受短期降水影响。（5） 2007年西安地区降水量为698.5mm,属于丰水年。但经过2008年一年的消耗,西安地区15龄苹果林地土壤含水量明显降低。表明西安地区中龄苹果林地水分消耗速度快,而且仅靠丰水年的降水难以维持中龄苹果林的正常生长。（6）通过最小二乘法对西安地区不同人工植被0～6m土壤含水量变化趋势进行模拟,发现5次多项式ψ=c₁+c₂z+c₃z²+…+c₆z⁵对土壤含水量模拟结果最好。（7）利用土壤水分动力学模型,模拟了地处半湿润地区的西安市长安区大学城附近从2008年3月25日到2008年4月8日的土壤含水量的变化,并与实测值进行了对比,其离差为0.0078,模拟效果较好。土壤表层0～1m模拟效果较下层差,这是由于土壤水分动力学模型对植物的根系分布、土壤水分的扩散率和导水率的敏感性较强的缘故。更多还原

【Abstract】 The Loess Plateau is situated at semi-humid area,where the rainfall is little and concentrates, and the underground water buried depth is deep,which cause the soil moisture to be especially important in vegetation construction of the Loess Plateau.Surface evaporation and plant’s transpiration cause the soil moisure to be serious lost,and the dry layer has appeared in soil under some vegetation.The moisture content is the most important factor that restricts northwest ecological environment construction and the important factor that restricts the development of the agriculture and the forestry,so the research to the soil-water environment in the artificial vegetation has the extremely vital significance.Through determining the soil moisture in different artificial vegetation from the surface to below 6 meters in Xi’an area of the most south of the Loess Plateau,this artical has studied some problems such as in local area the soil moisture content’ seasonal variation in farmland and apple forest land in 2008,the region difference of different artificial vegetation,the soil moisture variation condition of the farmland,the soil moisture consumption process of the apple forest and so on.The samples studied are got through light-duty manpower.The depth of the hole is 6 meters,and the distance is 10 centimeters.In every hole 60 samples are got.The determination of the soil moisture content uses the drying weight method which is considered accurate and reliable.The spots include the university city and Shaoling plateau in Chang’an area,Pangxi village in Xianyang area, as well as Liquan and so on.Kinds of the artificial vegetation were chosen including the 7 age,10 age,15 age apple forest,the wheat and the corn and so on.Through the determination and analysis to soil moisture content of apple forest and farmland in the different seasons,we have obtained the below knowledge.（1） The soil moisture content under different artificial vegetation of Xi’an area is different. Among the artificial plant chosen by us,average of soil moisture content of farmland is 16.95%.,for ten-year-age apple tree plantation,it is 14.61%which is less than farmland’s by 2.34%.In the depth of 0-200cm,200-400cm and 400-600cm,average of soil moisture content of farmland is 14.63%, 17.10%and 19.12%,for apple tree plantation,it is 13.63%,15.01%and 15.18%.Above data show that water consumption of apple tree plantation is more than farmland.（2） Different age of apple forest have obvious difference in soil moisture content.The Young age of soil moisture of apple forest is higher than middle age.In the same condition of terrain,for 6 m,soil mositure of different age apple forest have same resemblance that is changed by depth..（3） In autumn of 2008,the soil moisture in "universities city",Pangxi village and Shaoling Plateau was measured and obtain the result that Shaoling plateau is the highest then is universities city the last is Pangxi village.In Pangxi village and Liquan,the middle age of soil moisture of apple forest is generally low,which is 11.42%and 12.94%.And soil moisture of below 4m of middle age generally is less than 12%.This evidence adequately shows that soil of middle age of apple forest in this area generally has dry layer.（4） In half century climate of Xi’an is apt to warming and drying.From 2003 year having enough precipitation to now,soil moisture of farmland still remains high.Farmland has no dry layer even at high peak of water consumption of wheat,soil moisture also meet need of crop growing. This evidence is related with normal precipitation during these 6 years in this area.The conclusion is that soil moisture is influenced by precipitation in short period.（5） Precipitation in Xi’an,2007,is 698.5mm,enough rainy water year.After 2008 consumption,soil moisture of 15-year-age apple forest obviously decreased.The conclusion is that the consumption speed of the soil moisture under middle age apple forest land in Xi’an area is very quickly,moreover it is difficult that only depending on the precipitation in the rainy year to maintain the middle age apple forest’ normal growth.（6） By minor 2 multiplications to simulate fluctuation of 0-6cm soil moisture content for different artificial vegetation,the finding isφ=c₁+c₂z+c₃z²+…+c₆z⁵,this algebraic expression with five terms can evaluate the soil moisture.（7） By the mode of soil moisture dynamics,simulate and contrast fluctuation of semi-humid area of soil moisture in Chang’an district of xi’an from 25^th,March,2008 to 8^th April,2008,the deviation is 0.0078.Data is very near to reality.The simulating data of 0-1m of surface soil is poor because of strong sensibility of soil moisture dynamics for root distribution,diffusivity of soil moisture and conductivity.更多还原