【作者】 王延平；

【导师】 邵明安；

【作者基本信息】 西北农林科技大学 ， 植物营养学， 2009， 博士

【摘要】 陕北黄土区≥25°陡坡地,植被稀疏,土壤干旱和水土流失极为严重,是黄土高原植被重建和治理水土流失的重点和难点。长期以来,由于降水资源短缺和植被建设缺乏水量平衡的基础,陡坡地植被土壤旱化、生态经济效益低的问题突出存在。合理利用降水资源是陡坡地植被建设可持续发展的关键。为此,研究了陡坡地人工植被的土壤水分生态环境、陡坡地土壤水分和植物生长的关系、陡坡地土壤水分植被承载力和自然降水的高效利用。主要结论如下:1.陡坡地多年生人工植被的土壤水分亏缺极为严重,贫水年0～10m土层贮水量仅相当于田间持水量的26.2%～42.0%,丰水年贮水量也仅占田间持水量的27.0%～43.3%;亏缺次序为:柠条>刺槐>苜蓿>侧柏>杨树>油松>荒坡>杏>枣>农地。年际间同一植被土壤水分含量的变化主要发生在200cm以上土层内,变异程度随土壤深度的增加而减弱。同一生长季,各种植被0～120cm土层含水量的变异系数都较大,但植被间差异较小;120cm以下土层,变异系数较小,但植被间差异较大。陡坡地多年生植被均有永久干层存在,但深层土壤干燥化强度因植物种类和生长年限而存在明显的差异。雨季土壤水分的补偿和恢复深度为1.0～1.4m,但不同植被的土壤贮水增量和补偿度有较大差异。同一植被丰水年的雨水补偿深度比干旱年可增加60cm以上,5m土层贮水增量增加3倍以上。在自然降雨条件下,陡坡地多年生人工植被的土壤贮水亏缺状况不能得到改善,土壤干化现象也不可能有所缓解。2.陡坡地不同植被的干燥化强度可用土壤干燥化指数表示。公式为:SDI =(SM–WM)/(SSM–WM)×(SD-DT)/(SD)×100%,式中,SDI为土壤干燥化指数,SM为土壤湿度,WM为凋萎湿度,SSM为土壤稳定湿度,DT为干燥化厚度,SD为土层深度。陡坡地植被的土壤干燥化强度可划分为6级: (1)若SDI≥100%,为无干燥化;(2)若50%≤SDI<100%,为轻度干燥化;(3)若30%≤SDI<50% ,为中度干燥化;(4)若10%≤SDI<30%,为严重干燥化;(5)若0≤SDI<10% ,为强烈干燥化;(6)若SDI< 0,为极度干燥化。3.杏树林冠截流量次变化在0.30～9.5mm,林冠截留率变化在2.6～67.6%,林冠截流总量占总降雨量的21.10%;柠条林冠截流量次变化在0.21～3.2mm,林冠截留率变化在2.0～28.0%,林冠截流总量占总降雨量的11.73%。降雨次数多、暴雨次数少,林冠截流总量所占比例增大。4.陡坡地植被径流量大。苜蓿地地表径流量随降雨量增大呈指数增长,关系式为:Y = 0.002x2+0.1285x-0.2409(R2 = 0.9731),地表径流量平均占降雨量的12.41%;杏林地地表径流量平均占降雨量的11.41%;柠条林地占降雨量的16.27%。植被类型(冠幅、冠层厚度、郁闭度)、坡度、水保工程是陡坡地地表径流最大的三个影响因素。5.自然降水条件下,陡坡苜蓿地的最大入渗深度为140cm,陡坡杏树地的最大入渗深度达160cm,而陡坡柠条地的最大入渗深度仅为120cm。6.影响苜蓿地土壤水分补给的主要因素为天然降水、地表径流和林冠截留。25°陡坡苜蓿地土壤水分补给量(Y补)与降水量(P)的关系为:Y补=0.8003P+2.8568 (R2=0.987,n=33),33°关系式为:Y补=0.7771P+3.0411 (R2=0.985,n=33)。坡度越大,地表径流量越大,土壤水分补给量越小。杏林地降雨量(P)与根层土壤水分补给量(SWS)的关系为SWS=0.6299P+0.5901,相关系数为0.9829。柠条林地降雨量(P)与根层土壤水分补给量(SWS)的关系为:SWS=0.5708P+28.579,相关系数为0.9658。在降雨量基本一致的条件下,影响冠层截留和地表径流的因素如植被类型(冠幅、冠层厚度、郁闭度)、坡度、水保工程、土壤结构、地表粗糙度、枯枝落叶、耕作管理等都会对土壤水分的补给量产生不同的影响。7.陡坡苜蓿地土壤水分补给量(Y补)与地上部生物量(W干重)呈线性关系,南向25°上坡关系式为:Y补= 0.0247 W + 275.52,R2=0.9598;南向33°上坡关系式为:Y补= 0.0249 W + 279.37,R2=0.9767;南向25°下坡关系式为:Y补= 0.0348 W + 235.83,R2=0.9620;北向25°下坡关系式为:Y补= 0.0304 W + 247.31,R2=0.9727。陡坡苜蓿地土壤水分消耗量(Y耗)与地上部生物量(W干重)呈二次函数关系,南向25°上坡关系式为:Y耗= 0.0001 W2 - 0.4635 W + 854.72,R2 =0.9595;南向33°上坡关系式为:Y耗= 0.0001 W2 - 0.3836 W + 659.16,R2=0.9805;南向25°下坡关系式为:Y耗= 0.0001 W2 - 0.4628 W + 805.53,R2=0.9731;北向25°下坡关系式为:Y耗= 0.0001 W2 - 0.5324 W + 991.67,R2=0.9514。生物产量高,土壤水分消耗量大。坡向对土壤水分消耗量的影响较大,南坡日晒强烈,蒸发量大,土壤水分消耗量大。用FAO法估算可得陡坡地土壤水分可承载的苜蓿最大产量为3992.2～4173.7 kg/hm2;而根据水量平衡原理计算可得陡坡苜蓿地可承载的地上部生物量为2600～3500kg/hm2,比FAO法低16.07～33.52%。由于FAO法是应用了许多气象因子作为参数模拟所得,增大了误差,故现实中应以水量平衡原理计算结果为准。8.陡坡杏林地土壤水分补给量(Y补)与生物量(W)的关系为W =7.6419Y补+1024.1,R2= 0.9369。土壤水分消耗量与生物量关系为:Y耗=0.00001W2-0.0251W+195.61,R2=0.9282。土壤水分可承载的杏树生物量为2423kg/hm2,即可承载的果实产量为3063kg/hm2。9.陡坡柠条林地林冠截留量(I)与密度(D)的定量关系为:I = 0.7359D0.4925,R2 = 0.9642;地表径流(Run)和密度(D)关系为:Run=-0.021D+152.53,R2 = 0.9509;柠条根层土壤水分补给量(Y补)与密度(D)的关系为:Y补=0.0145D+215.4,R2= 0.9582土壤水分消耗量与密度的关系为:Y耗=0.00001D2-0.0089D+200.82。R2=0.9537。陡坡地土壤水分可承载的柠条密度为2852穴/hm2。10.采用塑膜微集水促渗技术,可提高杏、枣栽植成活率、产量、品质和经济效益;杏树自然降水利用率达2.92kg/m3,比对照提高53.68%,枣树自然降水利用率达3.45kg/m3,比对照提高53.33%;集中降雨前后根际区以下(2-6m土层)的贮水增量为31.1mm,相当于对照的近40倍,可有效防止土壤干化及其所导致的植株生长不良的发生。该技术成本低、简单易行、使用年限长、效率高,在我国广大的干旱贫困山区具有广阔的应用前景。更多还原

【Abstract】 ≥25°steep slopes of Loess region in northern Shaanxi , vegetation is sparse, soil drought and soil erosion is extremely serious, and it is the focus and difficulty in the reconstruction of vegetation and the control of soil erosion in the Loess Plateau.A long time,the problems of soil dry and low ecological and economic benefits were exist on steep slopes,it dued to shortage of rainfall and the lack basis of water balance in vegetation construction.Rational use of rain resources is the key of sustainable development in vegetation construction on steep slopes.To this reason, soil moisture ecological environment of artificial vegetations in steep slope , relationship between plant growth and soil moisture in steep slope, vegetation carrying capacity of soil water, and the efficient use of natural precipitation on steep slope has studied.The main conclusions are that:1.Soil water was extremely deficient under condition of perennial artificial vegetations in steep slope. soil water storage (0～10m) was only equal to 26.2% ~ 42.0% of field capacity in dry years, and in rainy years it was also only equal to 27.0%～43.3% of field capacity. The order of soil water deficit was: Caragana microphylla> locust> alfalfa> Chinese arbor-vitae> poplar> Chinese pine> wild land> apricot> Chinese date> farm land. Annual variations of soil moisture with same vegetation were weakened with soil depth increasing, and happened mainly in 0～200 cm soil layers. In same growth season, all CV (Coefficient of Variation) of soil moisture under different vegetations were bigger and concentrated comparatively in 0 ~ 120 cm soil layers, but difference of CV in different vegetations was small; below 120 cm soil layers, CV were smaller , but difference of CV in different vegetations was bigger. Permanent soil dry layers always happened under condition of perennial vegetations in steep slope , but the difference of soil aridization intensity was obvious among different vegetations and growth years. Soil water compensation and recovery depths in rainy season were 1.0 ~ 1.4 m , but the soil water storage increment and compensation degree in different vegetations were dramatically different. Soil water compensation depth in same vegetation in rainy years was increased over 60 cm than in dry years, while the soil water storage increment in 5 m soil layers was increased over 3 times. Under natural precipitation, the soil water deficit in artificial vegetations in steep slope cannot be reduced, soil aridization also can′t be relieved. 2. The dry strength of Vegetation on steep slopes can be indicated by soil desiccation index.Formula: SDI =(SM–WM)/(SSM–WM)×(SD-DT)/(SD)×100%,there, SM is soil moisture, WM is wilting moisture, SSM is the stable soil moisture, DT is the drying thickness, SD is the soil depth.The soil drying strength of vegetation on steep slopes can be divided into six levels: (1) SDI≥100%, non-drying; (2) 50%≤SDI <100%, mild desiccation; (3) 30%≤SDI <50%, moderate desiccation; (4)10%≤SDI <30%, serious desiccation; (5)0≤SDI <10%, strong desiccation; (6) SDI <0, extreme desiccation.3. Interception of Prunus armeniaca change in 0.30 ~ 9.5mm at each rain, rate of interception change in 2.6~ 67.6%, account for 21.10% of the total rainfall. Interception of Caragana korshinskii change in 0.21 ~ 3.2mm at each time, rate of interception change in 2.0 ~ 28.0%,account for 11.73% of the total rainfall. Rainfall frequency is more,or torrential rain is less, rate of interception account precipitation is bigger.4. Runoff is large on steep slopes.Runoff increases exponentially with the increase of rainfall in Alfalfa land, the relationship is: Y=0.002x2+0.1285x-0.2409(R2=0.9731),and runoff accounts for 12.41% of mean precipitation in Alfalfa land; runoff accounts for 11.41% of mean precipitation in Prunus armeniaca land; and runoff accounts for 16.27% of mean precipitation in Caragana korshinskii land.5. Under the condition of natural rain, the greatest infiltration depth is 140cm in alfalfa land in steep slope, the greatest infiltration depth is 160cm in apricot land in steep slope, the greatest infiltration depth is only 120cm in Caragana korshinskii land in steep slope.6. The main factors impact to soil moisture supplies in alfalfa land are natural precipitation, interception and surface runoff. In alfalfa land on 25°steep slope the relationship between soil moisture supply(Ys) with precipitation (P) is: Y up = 0.8003P +2.8568 (R2 = 0.987, n = 33), in 33°steep slope the relationship is: Ys = 0.7771 P +3.0411 (R2 = 0.985, n = 33). The slope is greater, the surface runoff is greater too, but soil moisture supply is less. In apricot land the relationship between rainfall (P) with soil water supply (SWS)is: SWS = 0.6299P +0.5901, correlation coefficient is 0.9829. In Caragana korshinskii land the relationship between rainfall (P) with soil water supply (SWS) is: SWS =0.5708P+28.579, correlation coefficient is 0.9658.7. In alfalfa land on steep slopes , the relationship between soil moisture supply (Ys) with aboveground biomass (Wd) showes a linear relationship,in 25°slope up to south the relationship is: Ys =0.0247W+275.52, R2 =0.9598; in 33°slope up to south the relationship is: Ys=0.0249 W +279.37, R2 =0.9767; in 25°slope down to south the relationship is: Ys =0.0348 W + 235.83, R2 = 0.9620; in 25°slope down to north the relationship is: Ys= 0.0304 W+247.31, R2=0.9727.In alfalfa land on steep slopes, the relationship between soil water consumption (Yc) with aboveground biomass (Wd) is the secondary function , in 25°slope up to south the relationship is: Yc=0.0001W2-0.4635W+854.72, R2=0.9595; in 33°slope up to south the relationship is: Yc =0.0001W2-0.3836W+659.16, R2=0.9805; in 25°slope down to south the relationship is: Yc=0.0001W2-0.4628W+805.53, R2= 0.9731; in 25°slope down to north the relationship is: Yc= 0.0001W2-0.5324W+ 991.67, R2=0.9514. Soil water consumption is enlarge with high biological production. Impact of aspect on soil water consumption is greater , on southern slope sun is strong, evaporation and soil water consumption is greater.On steep slopes the biggest carrying alfalfa production of soil water is 3992.2 ~ 4173.7 kg/hm2 by FAO method; and it is 2600 ~ 3500kg/hm2 by the principle of water balance,it is lower 16.07 ~ 33.52% than FAO method.because the application of meteorological factors in FAO method , increases the error, so in reality the principle of water balance should be based on whichever calculation results.8. The relationship between supply of soil moisture (Ys) with biomass (W)is: Ys=0.1226W-103.59, R2=0.9369. The relationship between consumption of soil moisture (Yc) and biomass(w) is: Yc=0.00001W2-0.0251W +195.61, R2 = 0.9282. Biomass of apricot that Soil moisture can carry is 2423kg/hm2, fruits production that Soil moisture can carry is 3063kg/hm2.9. In Caragana korshinskii land in steep slope the relationship between interception(I) with density(D)is:I=0.7359D0.4925, R2 =0.9642; the relationship between surface runoff(Run) with density(D) is: Run =- 0.021D + 152.53, R2=0.9509; the relationship between soil moisture supply(Ys) with density(D)is: Ys= 0.0145D +215.4, R2 =0.9582 ,and the relationship between soil water consumption(Yc) with density(D)is: Yc=0.00001D2-0.0089D +200.82. R2 = 0.9537. On steep slopes density that soil moisture can carry is 2852 clump/hm2.10. In loess region in North Shaanxi, the technique of plastic-catchment and promote-infiltration can increase survival rate, yield and quality and economic benefits of apricot and jujube, Rainwater use efficiency of 5 years-old apricot reached 2.92kg/m3, increased by 53.68% compared with CK, Rainwater use efficiency of 5 years-old jujube reached 3.45kg/m3 , increased by 53.33% compared with CK. During concentrated precipitation soil water recruitment below rhizosphere area (2-6m) was 31.1mm, it was almost equal to 40 times of CK. This part water was used by plant in arid season. This technique cost lowly and operated simply. The service life was long, The efficiency was high. It will have broad application prospect in the general drought and impoverished mountainous area of our country.更多还原