【作者】 杜阿朋；

【导师】 王彦辉；

【作者基本信息】 中国林业科学研究院 ， 生态学， 2009， 博士

【摘要】 本文在处于典型半干旱区的六盘山北段西侧的叠叠沟小流域研究了植被和地形与土壤的坡面水文影响。研究内容包括流域内土壤特性空间分布、植被冠层截留特征、枯落物水文功能、典型乔木和灌木的蒸腾特征、土壤水分入渗、样地土壤水分动态变化、样地水分平衡及流域径流特征,并应用生态水文模型BROOK90进行了多种情景模拟。所得研究成果如下:1 .流域内土壤特性的空间分布规律流域内土壤厚度的空间变异程度属于中等变异。阴坡和半阴坡的土壤厚度均大于阳坡和半阳坡。不同坡位间土厚平均值(cm)差异较大:坡顶(34.8)<上坡(47.7)<中上坡(75.9)<中坡(83.4)<下坡(131.2)<坡底(286.4)。在现有植被中,灌丛多位于土层较薄地段,乔木林地和退耕地多位于土层较厚地段。对流域内93个土壤物理性质测点所得结果统计分析后发现,93个样点所有土层中石砾体积含量平均为5.96%。粒径在2~4mm和4~6mm的总量占总石砾体积的62.39%。表层(0-20cm)土壤石砾体积含量(%)在不同坡向上为:阳坡(3.07)>阴坡(2.89)>半阴半阳坡(1.99);在不同坡位上:下部(3.46)>中上部(3.05)>坡顶(2.46)>中部(2.20)>上部(2.08)。土壤石砾体积含量随土层深度的变化基本呈S型曲线特征。2.植被冠层截留降雨特征在2008年华北落叶松生长季(4月～10月),降水量为389mm,对应的平均截留率为20.03%,5月份的截留率最大,平均为23.73%;9月份最小,仅为18.12%。叶面积指数的空间分布在一定程度上能影响树冠穿透降雨的空间分布。2008年生长季18场降雨的华北落叶松茎流量平均为0.09mm,占每次降雨林外降水量的0.46%。研究期间,虎榛子灌丛穿透雨量变化在1.1～42.4mm,平均穿透率为58.6%;沙棘灌丛穿透雨量变化在0.7～45.0mm,平均穿透率为53.0%。利用大于5mm的降雨场次测定的穿透雨与林外雨数据推得沙棘灌丛的冠层容量为1.58mm,虎榛子灌丛为0.54mm。51.6mm的降雨后各草本植物单位叶面积的截持降水率平均为0.02g/cm2,通过样地地上生物量换算成持水水深为0.85mm,占降水总量的1.64%。3.枯落物水文功能流域内4种植被类型的枯落物最大持水率大小依次为:华北落叶松(332.2%)>沙棘灌丛(288.6%)>虎榛子灌丛(220.6%)>半阳坡草地(219.5%);通过浸水法测定4种植被类型枯落物最大持水深大小依次为:华北落叶松(2.2mm)>虎榛子灌丛(1.3mm)>沙棘灌丛(0.9mm)>半阳坡草地(0.6mm)。利用一场连续降雨事件中测定的华北落叶松枯落物含水量得到了野外降雨条件下枯落物的吸水过程。测得的枯落物最大持水率变动在159.9%～246.6%,平均为219.4%,最大持水量为16.01 t.hm-2,约为浸泡所得枯落物最大持水量的74.3%。枯落物蒸发速率与含水率基本呈现对数关系,蒸发速率随含水率的增加而逐增大并无限逼近所处环境条件下的水面蒸发速率。2008年6月底到10月底华北落叶松林分样地内枯落物持水率的变化在6.0%～192.3%之间。4.华北落叶松和沙棘的蒸腾特征华北落叶松树干液流速率在晴天呈现明显的昼夜变化规律,为典型的“单峰型”。阴天峰型出现较多的无规律波动。降雨发生时,树干液流速率降低到同时期晴天夜间水平甚至更低,并使其出现多峰性。雨后晴天树干液流速率的峰值和日均值都高于雨前晴天,且降雨量越大,降雨前后树干液流速率差值也越大,表明蒸腾受土壤水分限制。在连续干旱条件下,树干液流速率峰值呈降低趋势。华北落叶松树干日液流通量季节变化显著,2008年生长季月平均液流通量为:5月>6月>7月>8月>9月>10月。沙棘液流通量日变化曲线具单峰型特征,观察中发现的“双峰”或“多峰”曲线由当时天气晴阴变化决定。沙棘在夜间有液流存在,约为白天的17.78%,而且干旱时期夜间蒸腾占白天或全天蒸腾的百分比大于较湿润时期的值。5.土壤水分入渗采用小区漫流法测得流域内不同植被类型的土壤稳渗速率(mm?min-1)平均值分别为:天然草地(5.33)、虎榛子灌丛(5.13)、沙棘灌丛(4.29)和华北落叶松林地(3.81)。在水分限制性的植被恢复区,坡向通过影响植被生长状况来影响土壤稳渗速率,以天然草地为重点研究了不同坡向的稳渗速率,依次为阴坡(5.40)>半阴坡(5.23)>阳坡(5.12),不同坡位依次为中坡位(5.92)>下坡位(5.36)>上坡位(4.96)。6.样地土壤水分动态华北落叶松林内土壤水分的时空差异极其显著,依据在2008年观测的土壤水分时间动态可划分为土壤水分的相对湿润期(5月4日～5月21日)、持续消耗期(5月22日～9月7日)和快速恢复期(9月8日～11月1日);依据水分利用特征可将垂直土层划分为土壤水分的微弱利用层(0-20cm)、利用层(20-60cm)和水分调节层(60cm以下)。2008年生长季期间各样地土壤有效水排序为沙棘灌丛>阳坡草地>半阳坡草地>虎榛子灌丛>陡坡华北落叶松林。陡坡华北落叶松样地和虎榛子灌丛的一些土层在6月至9月初出现无效水状态,阳坡草地、半阳坡草地和沙棘灌丛虽然未有无效水状态出现,但在6月至9月初有很多时候处于难效水状态。7.样地水量平衡及流域径流特征各样地的地表径流和壤中流占降水量比例很小,地表径流占0.5%左右,壤中流不到0.5%,所以在分析样地水分平衡时可将其忽略。样地水量平衡分析表明,蒸散量是样地水分平衡的最大分量。阳坡草地、半阳坡草地能向外部输出液态水资源,属输出型;而陡坡华北落叶松林、缓坡华北落叶松林及半阴坡沙棘灌丛需要消耗外部输入的坡面径流水分,为消耗型。流域径流年内分配不均匀,生长季初期以基流为主;进入8、9月份后由降水形成且容易由于暴雨而出现流量骤增的洪峰流量。8.应用BROOK90模型模拟分析植被的水文影响应用BROOK90模型的模拟结果表明,不同植被的生长季蒸散量均占到同期总降雨量的70%以上,3种植被类型下总蒸散量的大小排序为华北落叶松>沙棘灌丛>草地;坡面产流量大小排序为草地>沙棘灌丛>华北落叶松。在相同植被的条件下,阳坡蒸散高于阴坡,其坡面产流低于阴坡。坡面产流受坡向的影响程度以草地最大,沙棘灌丛次之,华北落叶松林最小。坡度较大时的样地产流明显多于坡度较小时的样地产流,随着坡度增加,蒸散各分量均呈下降趋势。土厚对蒸散分量的影响和植被类型有关,土厚主要影响草地的土壤蒸发,对于沙棘灌丛和华北落叶松林的影响主要体现在植被蒸腾上。土厚由20cm增至90cm,华北落叶松植被蒸腾量增加了37.1%,沙棘灌丛增加了26.3%。随着初始土壤水势的降低,蒸散量和样地产流量均呈降低趋势。在综合考虑植被类型、坡向和土壤厚度的坡面产流影响的角度,本研究探讨了适合于当地的植被恢复模式。更多还原

【Abstract】 The effects of vegetation types, terrain and soil on hillslope hydrological process were studied in the small watershed of Diediegou at the northwest part of Liupan Moutains. The contents of the dissertation are comprised of analysis upon spatial investigation of soil hydraulic characteristics, vegetation canopy interception, the hydrological function of litter, transpiration of arbor and shrub, infiltration of soil water, soil water variation, water balance in permanent plots, the character of runoff in watershed and the applications of BROOK90 model for scenarios simulation. The main results are as follows:1. The spatial distribution of soil hydraulic characteristics in small watershedThe special distribution of soil depth in watershed presented a middling degree of variation. The soil depth at shady and semi-shade slopes was much thicker than at the sunny and semi-sunny slopes. The soil depth (cm) in different slope positions showed an order as follows: the slope top (34.8) < the up-slope (47.7) < the middle-up slope (75.9) < the middle slope (83.4) < the down-slope (131.2) < the slope foot (286.4). In the small watershed, much of the shrubs were laid at sites with thin soil, while the arbor woodlands were basically laid at site with thick soil.The average of rock fragment content in all soil layers of all 93 soil plots investigated in this study was 5.96%, and the content in diameter range of 2-6mm occupied 62.39% of the gross rock fragment. The rock fragment content (%) in the surface layer (0~20 cm) at different slope aspects showed an order as follows: sunny slope (3.07) > shady slope (2.89)> semi-shady slope (1.99). The rock fragment content (%) in the surface layer at different slope positions showed an order as follows: down-slope (3.46) > middle-up slope (3.05) > slope top (2.46) > middle-slope (2.20) > up-slope (2.08). The rock fragment content increased with soil depth basically in an S-curve.2. The interception of vegetation canopyThe averaged interception ratio in Larix principis-rupprechtti stand was 20.03% in growing period of 2008 (April to October) with a precipitation of 389mm. The averaged interception ratio in May (23.73%) was the highest and that in September (18.12%) was the lowest. The spatial distribution of throughfall ratio under tree canopy was influenced by the variation of leaf area index (LAI). The averaged stem-flow from 5 Larix principis-rupprechtti trees for 18 rainfall events was 0.09mm, accounting for 0.46% of the gross precipitation.In the research period, the throughfall ranged from 1.1 to 42.4mm in Ostryopsis davidiana community plot, and from 0.7mm to 45.0mm in Hippophae rhamnoides community plot. The canopy interception capacity of these 2 shrubs was obtained by using the statistical analysis between throghfall and open-field precipitation over 5mm. The canopy interception capacity was 0.54 mm for Ostryopsis davidiana, and 1.58 mm for Hippophae rhamnoides. The averaged interception ratio of herbage per unit LAI was 0.02 g/cm2 which was measured after one 51.6 mm rainfall event, accounting for 1.64% of the total rainfall depth.3. The hydrological function of litterBy soaking the litters from 4 different vegetation type plots, the saturated water-holding ratio of litter was in the order as follows: Larix principis-rupprechtti (332.2%) > Hippophae rhamnoides (288.6%) > Ostryopsis davidiana (220.6%) > grassland at semi-sunny slope (219.5%), and saturated water-holding capacity of litter in depth was in the order as follows: Larix principis-rupprechtti (2.2mm) > Ostryopsis davidiana (1.3mm) > Hippophae rhamnoides (0.9mm) > grassland at semi-sunny slope (0.6mm).By the field measuring of the water-content variation process of litter in Larix principis-rupprechtti plot during one series of continuous rainfall events, it was obtained that the peak water-holding ratio of litter ranged from 159.9% to 246.6%, the average was 219.4% and the corresponding water-holding capacity of litter in open field was 16.01 t.hm-2, which equals only 74.3% of it obtained by soaking litter.The relation between litter evaporation rate and litter moisture is logarithm. The litter evaporation rate increased with increasing litter moisture, approaching the potential evaporation rate from free water surface. The litter moisture in the Larix principis-rupprechtti plot varied in the range from 6.0% to 192.3% in the research period from Jun. to Oct. in 2008.4. Transpiration of Larix principis-rupprechtti and Hippophae rhamnoidesIn sunny days, the daily variation of sap flow velocity (SFV) of sample trees of Larix principis-rupprechtti was a single-peak curve. The sap flow velocity fluctuated tunelessly in cloudy days. The SFV was dropped down to the night level in rain times and appeared complex curve with much peaks. The peak SFV and the daily averaged SFV in sunny days after rainfall events were higher than the sunny days before rainfall events, and the difference after and before rainfall increased with rising rainfall depth. The peak daily SFV was going to be reduced within continual drought days. The sap flux possesses a seasonal variation, the monthly averaged sap flux of Larix principis-rupprechtti in the growing period of 2008 showed an order as follows: May > June > July > August > September > October.The daily variation curve of sap flux for Hippophae rhamnoides is a single-peaked in sunny days, but double-peaked or complex-peaked in cloudy or rainy days. A night sap flow also existed in Hippophae rhamnoides. The night sap flow can amount to 17.78% of the diurnal volume and the percent in drought period is higher than in wet period.5. Infiltration of soil waterA study on the final infiltration rate was carried out for 4 typical vegetation forms in the small watershed of Didiegou, by using a method of overflowing in slope plots. The final infiltration rate (mm/min) of different vegetation types were: natural grassland (5.33) > shrub of Ostryyopsis davidiana (5.13) > shrub of Hippophae rhamnoides (4.29) > plantation of Larix principis-rupprechtii (3.81). The final infiltration rate was influenced by landform and there was clear difference among slope aspects, slope positions. Taking grassland as an example, the final infiltration rate in different slope aspects showed an order as follows: shady slope (5.40) > semi-shady slope (5.23) > semi-sunny slope (5.12), and the final infiltration rate in different slope positions showed an order as follows: midst slope position (5.92) > lower slope position (5.36) > upper slope position (4.96).6. The variation of soil water condition in permanent plotsThe spatio-temporal difference of soil water condition in the Larix principis-rupprechtii plot was very remarkable. According to the soil water dynamics during growing period in 2008, it can be divided into relatively wetness period (4 May to 21 May), durative consuming period (22 May to 7 Sep) and fast accumulating period (8 Sep to 1 Nov). According to soil water utilizing character, the vertical soil water dynamics with soil depth can be divided into 3 layers: faintness-utilizing layer (0-20cm), mostly-utilizing layer (20-60cm) and adjusting layer (below 60cm).The soil water availability in different plots in growing period of 2008 showed the order as follows: Hippophae rhamnoides shrub > grassland in sunny slope > grassland in semi-sunny slope > Ostryyopsis davidiana shrub > Larix principis-rupprechtii on steep slope. The soil water condition in plots of Larix principis-rupprechtii on steep slope and Ostryyopsis davidiana shrub appeared even an invalidation state from June to September, but other plots were unwieldy state.7. The water balance in permanent plots and the watershed streamflow charactersFor all the plots with different vegetation types in this study, the surface runoff was only about 0.5% of precipitation, and the inter-flow was below 0.5% of precipitation. So they the surface runoff and interflow can be neglected in plot water balance analysis. The results analysis indicated that the evapotranspiration was the biggest item in plot water balance. Grassland (both in sunny and semi-sunny slopes) can be classified into a type of water-yielding, while the Larix principis-rupprechtii plantation (both in steep slope and slow slope) and the Hippophae rhamnoides shrubland in semi-sunny slope can be classified into a type of water-consuming.The seasonal variation of streamflow in the small watershed was very uneven. The streamflow was mainly composed of base flow in initial period of growing season and after November, but composed of fast runoff with peak discharge caused by rainstorms in the rainy season from August to October.8. The applications of BROOK90 model to simulate the hydrological effect of vegetationThe simulation with the calibrated model of BROOK90 showed that the evapotranspiration can amounts to more than 70% of gross precipitation for all the vegetation plots in growing season. The evapotranspiration of 3 vegetation types showed an order as follows: Larix principis-rupprechtii > Hippophae rhamnoides > grassland, but the plot water yield as: grassland > Hippophae rhamnoides > Larix principis-rupprechtii. For all the vegetation plots investigated in this study, the evapotranspiration in sunny slope was higher than in shady slope, but the water yield in sunny slope was less than in shady slope. The effect of slope aspect on plot water yield was different with vegetation types and the magnitude of effect decreased with the order of: grassland > Hippophae rhamnoides > Larix principis-rupprechtii. The steeper slope can yield more water resources than that from gentler slope. The evapotranspiration appeared to be decreased with increasing slope gradient for all plots.Soil depth is very important factor for the evapotranspiration, but this effect varied with vegetation types. The main response to changing soil depth was the soil evaporation in grassland plot, in the plots of shrub and forestland. When the soil depth increased from 20cm to 90cm, the transpiration increased by 37.1% in Larix principis-rupprechtii plot and26.3% in Hippophae rhamnoides plot. The evapotranspiration and water yield from plots decreased with decreasing initial soil water potential. Taking an integrated analysis of the hillslope hydrological effect from vegetation types, slope aspect and soil depth, the suitable vegetation restoration models was discussed for the research areas.更多还原