【作者】 刘建立；

【导师】 王彦辉；

【作者基本信息】 中国林业科学研究院 ， 生态学， 2008， 博士

【摘要】 考虑林水矛盾和优化林水相互关系是在西北半干旱地区进行林业生态环境建设时必须重视的核心问题,本文在处于半干旱区的六盘山北坡叠叠沟小流域研究了当地主要植被类型的生长及其耗水规律,有关结果充实了半干旱地区林水关系研究中植被和水分相互影响的内容,利于促进发展半干旱地区森林植被建设和管理的理论与技术,提高林水协调管理水平,为当地植被恢复与植被建设提供科学指导。主要研究结论为:1.典型植被样地的土壤水文物理性质不同植被类型的土壤物理性质: 0~100cm土层平均土壤容重为华北落叶松(0.92 g/cm3)<虎榛子灌丛(1.03 g/cm3)<阳坡草地(1.12 g/cm3)<半阴坡草地(1.15 g/cm3)<沙棘灌丛(1.16 g/cm3)。土壤非毛管孔隙度大小顺序是阳坡草地(10.45%)>华北落叶松(7.49%)>沙棘灌丛(5.86%)>虎榛子灌丛(4.86%)>半阴坡草地(4.84%);土壤毛管孔隙度大小顺序是虎榛子灌丛(52.9%)>华北落叶松(51.1%)>半阴坡草地(48.38%)>阴坡草地(46.85%)>沙棘灌丛(44.65%);土壤总孔隙度大小顺序是华北落叶松(58.59%)>虎榛子灌丛(57.82%)>阳坡草地(57.29%)>半阴坡草地(53.22%)>沙棘灌丛(50.51%)。不同植被类型的土壤持水性能:土壤毛管持水量的大小顺序依次为华北落叶松(511.01 mm)>半阴坡草地(492.73 mm)>沙棘灌丛(485.69 mm)>虎榛子灌丛(476.60mm)>阳坡草地(468.46mm)。土壤非毛管持水量大小顺序依次为阳坡草地(104.49 mm)>半阴坡草地(78.74 mm)>华北落叶松(74.81mm)>沙棘灌丛(52.17mm)>虎榛子灌丛(43.74mm),其中阳坡草地土壤非毛管持水量远大于其它样地的一个重要原因是其土壤石砾含量远高于其它样地。土壤最大持水量大小顺序为华北落叶松(585.82mm)>阳坡草地(572.94mm)>半阴坡草地(571.47mm)>沙棘灌丛(537.87mm)>虎榛子灌丛(520.34mm)。地形与土壤物理性质的关系:土层厚度随海拔升高而降低,随坡度增加而变薄。土壤容重随土深增加而逐渐增大。土壤总孔隙度、毛管孔隙度随坡位下降和坡度增加逐渐减少,并可看出总孔隙度随植被覆盖度加大而升高。非毛管孔隙度受多因素影响,但从坡向角度考虑时,阴坡非毛管孔隙度要高于阳坡,这主要是植被根系和土壤生物的影响造成的。阴坡和半阴坡的土壤物理性质明显好于阳坡。2.土壤水分动态土壤水分变化分期和分层:结合研究期间降水分布比较了不同典型样地(0~180 cm)土壤水分的季节变化,可分为土壤水分积累期、消耗期和恢复期;不同样地(0~180 cm)土壤水分垂直变化可大致分为土壤水分速变层、利用层、次要利用层和稳定层4个层次。土壤含水量变异系数的坡面变化:0～100 cm土层的土壤水分变异系数(CV%)在阴坡从坡下部华北落叶松林样地(22.4%)向上呈波浪式增加趋势,到坡顶草地样地(3-8号样地)最大(35%),较大的波动对植被生长十分不利;坡下部的华北落叶松样地(3-3号样地)变异系数也较大,这是因该样地位于林缘附近导致土壤含水量变异程度增加;其他样地的土壤含水量变异程度相似,变异系数范围在16%~22%之间,变化也较平缓;阳坡草地土壤含水量变异系数沿坡面从下向上呈波浪式增加趋势,坡底1号样地最小(22%),坡顶样地最大(38.5%),而坡中下部1-3号样地较小;阳坡坡面土壤水分变异系数范围在22.1%~38.5%之间。半阴坡土壤含水量变异系数的范围为23.5%~43%,在坡面呈单峰型变化趋势,即坡中部的2-3号样地最大(43%)。不同植被类型均处于土壤水分亏缺状态:由于本区降雨是土壤水分的唯一来源,土壤水分消耗量(植被蒸腾和土壤表面蒸发量之和)远大于降水量,导致了土壤水分长期亏缺状态。土壤亏缺量的值是指土壤水分含量低于土壤田间持水量的值,其中,不同植被类型样地的亏缺依次为:虎榛子灌丛>半阴坡草地>沙棘林>华北落叶松林>阳坡草地。不同植被类型下的土壤水分有效性依次为:阳坡草地>华北落叶松>沙棘林>半阴坡草地>虎榛子灌丛。3.华北落叶松树干液流特征及影响因素树干液流速率的日内和季节变化:在整个生长季内,华北落叶松树干液流速率呈逐渐下降趋势,最高值出现在5月份(0.22 cm/min),最低值出现在10月份(0.013 cm/min)。不同月份的树干液流速率的日变化(启动时间、上升过程、到达高峰时间、下降过程和到达低谷的时间)规律趋于一致,基本呈单峰型曲线。生长季内各月平均液流速率大小顺序为:5月(0.27 cm/min)>6月(0.25 cm/min)>8月(0.21 cm/min)>7月(0.2 cm/min)>9月(0.13 cm/min)>10月(0.054 cm/min)。土壤水分的影响:土壤水分不仅影响树干液流速率的峰值,也影响其日进程(启动时间、上升过程、下降过程等)。干旱条件下的液流启动时间和速率峰值比湿润条件下延迟1 h,液流速率变化曲线比较陡峭。无论土壤是干旱还是湿润,单位边材面积的日累计液流量的变化过程趋势基本相同,呈“S”型增长曲线。充足的土壤水分供给可促进植株蒸腾耗水,而在干旱条件时,植株可通过减少蒸腾来维持其生存。树木生长特征的影响:不同径阶样树的液流速率变化过程基本一致,其生长季平均值(0.113 cm/min)也相差不多。但是,由于不同径阶样木边材面积相差很大,造成样木液流通量相差很大。建立了单株液流通量最大值与边材面积的回归方程(R2=0.8848)。林分日蒸腾量和叶面积指数(LAI)不是简单的正比关系,当LAI小于4时,日蒸腾量大致随LAI增加而加大;但当LAI继续增加时,日蒸腾量增大很小,逐渐趋于最大值。气象条件的影响:在5~9月份,太阳辐射对树干液流速率有极显著影响,是主导因子;空气温度仅在5月份呈极显著正相关;土壤温度的相关性不如气温显著;空气湿度则呈极显著负相关;降水过程中的瞬时树干液流速率显著降低;但在阵性降水的日期内,日均液流速率同降水量呈正相关,可能是对降水输入提高土壤水分的响应;大气水势和饱和水汽压差同树干液流速率均呈正相关,但6和8月份的影响不显著;风速对树干液流速率的影响不明显。4.典型植被的降雨截留华北落叶松:华北落叶松林冠的次降雨截留率变化在1.25%~63.5%,截留量变化在0.06 mm~9.20 mm,总截留量为57.22 mm。林冠截留量在低雨量级时随降雨量增加而加大,但增加幅度有限,越来越趋于饱和截留量;华北落叶松林外降雨与林内穿透雨的关系可表示为一元线形回归模型(R2=0.9384)。次降水的树干茎流量所占比重较小,变化在0.001 mm~0.383 mm,平均茎流率为0.2%,树干茎流率随次降雨量增加呈线性加大(R2=0.5347)。灌木:虎榛子灌丛的次降雨林冠截留率变化在1.681~24.3%,平均为13.21%,表现为随雨量级增加呈下降趋势;次降雨的灌木茎流量变化在0 mm~2.95 mm,平均茎流率为8.52%;沙棘灌丛的次降雨林冠截留量变化在0.511~16.23mm,平均截留率为43.5%;次降雨的沙棘灌丛树干茎流变化在0 mm~5.26 mm,平均茎流率为14.64%。可见灌木的茎流是水量平衡中不可忽视的重要组分。枯落物截持:对降水量和枯落物截持量进行线性回归,拟合方程为:I l = 1. 229×P0.582 R 2 =0.546;一般情况下它的吸水作用是自身的的4倍,持水量相当于4 mm的降水。能很好的涵养水源,增加地表入渗的作用。同时,枯落物在释水过程的6 d后,基本达到分干状态,而这个过程可以持续6 h左右,枯落物这种缓慢释水的这种特性,能起到很好发挥枯落物的涵养水源功能。不同植被类型下枯落物的有效拦蓄深依次为:华北落叶松林地(3.22 mm)>虎榛子灌丛(3.18 mm)>半阴坡草地(1.53 mm)>阳坡草地(0.56 mm)>沙棘林(0.17)。5.样地水量平衡分析在综合生长季内降雨截持、植被蒸散和土壤水分变化等研究结果的基础上,研究发现华北落叶松人工林样地水量平衡中乔木蒸腾量最大,占同期降水量的50%~80%;林下土壤蒸发、植被蒸腾及林冠层降水截留量分别占同期降水量的12%、10%和10%左右;茎流量、降水产流量均较少,不到同期降水量的1%。5月、9月和10月份土壤水分存在亏缺,而6月、7月和8月份同期降水量则可满足林地水分需求。总体上说,整个生长季降水量基本可满足林地植被的蒸腾耗水,1号样地(阳坡草地)和2号样地(半阴坡草地)群落的蒸散量分别为237.8mm和204.2mm,两个样地平衡项均为正值。6.坡面典型植被的生长特征华北落叶松高生长:对本研究涉及的阴坡华北落叶松人工林林分,以其年高生长速率可划分为缓慢生长期(栽植后5年)和迅速生长期(5～20年)。栽植后前10年的平均生长速度以坡上位的6-8号样地最缓,为0.248 m/a;坡中位的6-5号样地居中,为0.472 m/a;坡底部的6-1号样地最高,为0.483 m/a。连年高生长有多种影响因素,相同立地同龄林木的高生长受林木生长和空间特征影响;不同立地同龄林木的高生长同土层厚度呈正相关,其次受林分密度影响。林分密度与林木高生长相关性不很高,说明密度不能很好映林木间竞争关系。阴坡草本植被:阴坡坡面共出现29种植物,各月的物种丰富度均随坡长增加表现为先升高后降低,呈明显的单锋格局,峰值在坡中部出现。物种丰富度最大值出现在生长季中期,而生长季初期和末期最小。阴坡落叶松林下的草本生物量在生长季变化在21.3 ~ 337.9 g/m2之间,平均149.9 g/m2。阳坡草本植被:阳坡坡面共出现23种植物种类,物种丰富度从坡脚向坡顶呈波浪式逐渐较少趋势。总生物量随沿着海拔的增加在坡面,生物量呈现出波浪式的变化,其中在坡脚的1-1号样地最大,生物量最大为2437.5 g/m2;其次是坡中部的1-5号样地,生物量为1951.3 g/m2,而位于坡下部的1-3号样地生物量最小,为1230.1 g/m2。地下生物量以则在坡中下部的1-3号样地最大,坡中上部的1-7号样地最小。随着从坡脚沿海拔向坡顶的延伸,5个不同样地的地上地下生物量的比值依次分别为:11.36%、25.61%、12.48%、10.64%和20.35%。半阴坡草本植被:半阴坡坡面共出现26种植物,物种丰富度从坡脚向坡中部呈波浪式变动趋势,而由坡中部向坡顶则逐渐降低。总生物量沿海拔增加呈现波浪式变化,其中在坡中上部的2-7样地最大,为2617.8 g/m2;其次是坡底部的2-1号样地,为1968.3 g/m2;位于坡下部的2-3号样地最小,为1330.7 g/m2。地下生物量的变化趋势与总生物量一致,而地上生物量的变化规律在整个坡面上不很明显,可见半阴坡草地的总生物量变化趋势取决于地下生物量变化。由坡脚沿海拔向坡顶延伸,5个不同坡位样地的地上地下生物量比值依次为19.15%、28.65%、25.91%、13.21%和44.67%。同时也发现半阴坡草地各样地的地上生物量也均明显小于地下生物量。枯落物现存量:不同植被类型下的枯落物现存量大小顺序为虎榛子灌丛(2985 g/m2)>华北落叶松(948.5 g/m2)>半阴坡草地(567.4 g/m2)>沙棘林(498.1 g/m2)>阳坡草地(204.5 g/m2)。枯落物数量的坡面分布规律为:半阴坡草地,坡底的2-1号样地枯落物现存量最高(567 g/m2),而坡顶的2-8号样地则较少(110 g/m2);在阳坡草地,坡底的1-1号枯落物现存量最大(398 g/m2);在阴坡华北落叶松坡面,枯落物生物量最大值出现在坡中部的3-5号样地(1486 g/m2),最小值出现在坡顶的3-9号样地(82 g/m2),这于华北落叶松的生物量坡面分布规律是一致的。土壤水分植被承载力初步研究:通过降水与叶面积指数建立方程,联合求解出,阴坡可以承载的叶面积指数为2.79,阳坡和半阴坡可以承载的叶面积指数为0.58。通过与实测值进行对比,发现该方法能比较可行,也为土壤水分植被承载力提供一条更加符合生物学特性的计算方法。更多还原

【Abstract】 Considering and optimazing the interrelationship between forest/vegetation and water resources is one of the important subjects for ecological reconstruction and vegetation restoration in the semi-arid zone of Northwest China. In this paper the growth and water use regularities were studied for main vegetation type which is one of the main plantation tree species on north side of the Liupan Mountains. This study is helpful to understand the interrelation between plantation growth and water condition in the semiarid area, and to promote the development of theories and techniques of the restorationan of forest/vegetation in semiarid area. The research conclusions could offer scientific guidance for the harmonious and integrated management of forest and water. The main conclusions were as follows:1. Analysis of soil hydrological-physical properties in different typical plots:Soil physical properties of different vegetation types: The results show obvious difference of the soil physical properties between different vegetation types. Soil bulk density showed the following order: Ostryopsis davidiana stands(1.16 g/cm3) > semi-shady grassland(1.15g/cm3) > sunny grassland(1.12g/cm3) > Hippophae rhamnoides stands(1.03g/cm3) > Larix principis-rupprechti stands(0.92 g/cm3). The size order of soil non-capillary porosity is sunny grassland(10.45%) > Larix principis-rupprechti stands(7.49%) > Ostryopsis davidiana stands(5.86%) > Hippophae rhamnoides stands(4.86%) > semi-shady grassland(4.48%). The size order of capillary porosity is Hippophae rhamnoides stands(52.9%) > Larix principis-rupprechti stands(51.1%) > semi-shady grassland(48.38%) > sunny grassland(46.85%) > Ostryopsis davidiana stands(44.65%). The size order of total porosity is Larix principis-rupprechti stands(58.59%) > Hippophae rhamnoides stands(57.82%) > sunny grassland(57.29%) > semi-shady grassland(53.22%) > Ostryopsis davidiana stands(50.51%).Soil water hoding capacity of different vegetation types: Results of soil water holding capacity showed obvious difference between different vegetation types. The size order of soil capillary capacity is Larix principis-rupprechti stands(511.01mm) > semi-shady grassland(492.73mm) > Ostryopsis davidiana stands(485.69mm) > Hippophae rhamnoides stands(476.60mm) > sunny grassland(468.46mm). The size order of non-capillary capacity is sunny grassland(104.49mm) > semi-shady grassland (78.74mm) > Larix principis-rupprechti stands(74.81mm) > Ostryopsis davidiana stands(52.17mm)>Hippophae rhamnoides stands(43.74mm). The maximum water capacity showd the following order: Larix principis-rupprechti stands(585.82mm) > sunny grassland(572.94mm) > semi-shady grassland(571.47mm) > Ostryopsis davidiana stands (537.87mm) > Hippophae rhamnoides stands (520.34mm).The influence of landform upon soil physical properties: By analyzing influence factors of soil physical properties in plots with different slope position and aspect, it was concluded that there was a passive correlation between the soil depth and slope position, and also a passive correlation between the soil depth and slope gradient. Soil total porosity and capallary porosity decreased with soil depth increasing, and total porocity increased with vegetation coverage increasing. The non-capallary porocity was influenced by many environmental factors such as biological factors, stone content, etc, but in terms of slope aspect , the non-capallary porocity in shady slope was higher than sunny slope since mainly of influence of vegetation root and soil biology. Generally speaking, the soil physical properties of shady slope and semi-shady slope were better than sunny slope.2. Study on soil water dynamicsSoil water dynamics during different periods and between different layers: Considering the precipitation during the research period, the soil water seasonal dynamic in different typical plots(0~180cm) can be divided into accumulating period and consuming period and restoring period; soil water dynamics in vertical direction can be divided into soil water variable greatly layer, soil water using layer, soil water subactive using layer and water stable layer.The law of soil water variation in different position on slope: the variance coefficient of soil (0~100 cm) water of Larix principis-rupprechti ahowed a fluctuant rising, and the biggest(35%) appeared on the upper slope,which was unfavorable for vegetation growth. But the variance coefficient of soil water was also very big in 3-3 plot, since the plot is located at the forest edge. The change of other plots showed a similar and quite smooth tendency. The variance coefficient ranged from 16% to 22%. The variance coefficient of sunny slope soil water showed a fluctuant rising and the lowest value (22%) appeared on the down slope, and the biggest(38.5%) on the upper slope. The variance coefficient ranged from 22.1% to 38.5%. The variance coefficient of soil water of semi-shady slope showed single peak and the biggest value (43%) appeared in 2-3 plot at the middle slope, and the variance coefficient ranged from 23.5% to 43%.The soil was in water deficit under all vegetation types: this is because the precipitation is the only source of soil water in the study area and soil water consumption (including transpiration water consumption and soil evaporation) was much larger than precipitation. This has resulted in long-term soil water deficit under almost all vegetation types. The water deficit ranking were: Hippophae rhamnoides stands > semi-shady grassland > Ostryopsis davidiana stands > Larix principis-rupprechti stands > sunny grassland, and soil water availability ranking were: sunny grassland> Larix principis-rupprechti stands > Ostryopsis davidiana stands > semi-shady grassland > Hippophae rhamnoides stands.3. Characters of sap flow of Larix principis-rupprechtii and the influencing factorsDaily and seasonal variation of sap flow velocity (SFV) : . Sap flow velocity decreased gradually in the whole season. the highest value(0.22 cm/min) was observed in May, and the lowest value(0.013 cm/min) was observed in October. The daily change of sap flow velocity(starting, rising, peaking, falling and reachingthe low valley) tend to uniform and that showed a single-peak curve. The average sap flow velocity in the whole growing season showed the following order: May(0.27 cm/min) >June(0.25 cm/min)> August(0.21 cm/min)> July(0.21 cm/min) > September(0.13 cm/min) > October(0.054 cm/min).The effect of soil water: The soil water effected not only the peak value of SFV but also the diurnal course (starting time, rising process and falling process). Under drought condition, peak value and staring time of SFV delayed one hour than wet condition, and the dynamic curve was more abrupt. The trend of daily accumulated sap flow amounts of sapwood were similar in soil drought and wet period, and the entire process of daily sap flow presented a S-shape curve. Enough soil water would promote the vegetation transpiration water consumption, while reduced the transpiration water consumption in drought period to maintain normal growth.The effect of tree growth characteristics: the varying process of SFV was quite consistent between sample trees with different diameter, and the average value(0.113 cm/min) was similar, too. However, the sap flux density different is quite obvious since the sapwood area difference between the different diameter sample trees is significant. The maximum sap flux density and sapwood area were used to get the regression equation (R2=0.8848) . According to the fact that there were not simple proportional relation between daily transpiration rate and leaf area index, the daily transpiration rate increased with the leaf area index when leaf area index is less than 2 m2/m2. But if the leaf area index kept increasing after that, the daily transpiration rate would decrease.The effect of meteorological factors: During the period from May to September, solar radiation showed very significant effect on SFV, and could be regarded as the dominant influencing factor. Air temperature was obviously and negatively related with SFV only in May. The effect of soil temperature was less significant than that of air temperature. There was a significant negative correlation between relative air humidity and SFV. During the precipitation process, the instantaneous SFV would markedly decrease to a very low level; But duringintermittent rainfall, the daily average SFV was positively related with the precipitation, and this could be the response to the increased soil wetness caused by rainfall infiltration. A positive correlation was observed between the SFV and air water potential as well as air saturation vapor pressure deficit, but it was not significant in June and August. There was no significant effect of wind speed on SFV.Simulation of SFV and the accumulated sapflow (SFC): A regression equation (R=0.832) was established for relating daily SFV with daily solar radiation, soil water potential within 1 m depth, and air temperature.5. rainfall interception of typical vegetationLarix principis-rupprechti: The result shows that the rainfall interception ratio of Larix principis-rupprechti was 1.25%~63.5%, and the total canopy interception was 57.22 mm, accounting for 15.5% of total rainfall and ranging from 0.06 to 9.20 mm. Total interception kept at a high level while the rainfall class was low, then decreased sharply and headed for a stable value gradually untill the highest interception capacity was reached. Relationship between rainfall inside forest and rainfall outside forest was simple linear regression. The average stemflow accounted for 0.2% of total rainfall, ranging from 0.001 to 0.383 mm, and increased linearly (R2=0.5347) with the rainfall.Shrub: The canopy interception ratio of rainfall of Hippophae rhamnoides was 36.8%, ranging from 1.25% to 63.5%, and gradually reducing with rainfall class increasing. The average stemflow accounted for 8.52% of total rainfall, ranging from 0.00 to 2.95 mm; The canopy interception ratio of rainfall was 53.5% for Hippophae rhamnoides, ranging from 0.511% to 20.661%. The average stemflow accounted for 14.64% of total rainfall for沙棘灌丛, ranging from 0.00 to 5.26 mm. The stemflow of shrub was an important part of water quantity balance.The litter existing amount: the litter existing amount of different vegetation type showed the following order: Hippophae rhamnoides stands(2985 g/m2) > Larix principis-rupprechti stands(948.5 g/m2)> semi-shady grassland(567.4 g/m2) > Ostryopsis davidiana stands(498.1 g/m2) > sunny grassland(204.5 g/m2). Distribution of litter existing amount of different slope: the biggest litter value (567 g/m2) appeared in 2-1 plot for the semi-shady slope, and the lowest (110 g/m2) in 2-8 plot; The biggest litter existing amount (398 g/m2) appeared in 1-1 plot for the sunny slope; The biggest litter existing amount (1486 g/m2) appeared in 3-5 plot for the shady slope, and the lowest (82 g/m2) in 3-9 plot and similar to Larix principis-rupprechti biomass.6. Water balance of typical plots After integrating the research results of interception, evapotranpiration, soil water variation etc, the results show that the Larix principis-rupprechti have the maximum transpiration rate, accounting for 50%~80% of total rainfall, except for the August and October. Forest soil evaporation, undergrowth vegetation transpiration and canopy interception accounted for 12%、10% and 10% of rainfall, respectively. The stem-flow and runoff caused by rainfall is relatively small, accounting for less than 1%, respectively. Soil water content deficit existed during May, September and October, and the water demand for vegetation growth could be meet during June, July and August. In general, the rainfall during whole growing season can meet the vegetation transpiration water consumption. The community evapotranspiration rate in sunny grassland and semi-shady grassland was 237.8 mm and 204.2 mm, respectively. The water consumption in sunny grassland was more than semi-shady grassland.7. Analysis of soil hydrological-physical properties in different typical plots:Soil physical properties of different vegetation types: The results show obvious difference of the soil physical properties between different vegetation types. Soil bulk density showed the following order: Ostryopsis davidiana stands(1.16 g/cm3) > semi-shady grassland(1.15g/cm3) > sunny grassland(1.12g/cm3) > Hippophae rhamnoides stands(1.03g/cm3) > Larix principis-rupprechti stands(0.92 g/cm3). The size order of soil non-capillary porosity is sunny grassland(10.45%) > Larix principis-rupprechti stands(7.49%) > Ostryopsis davidiana stands(5.86%) > Hippophae rhamnoides stands(4.86%) > semi-shady grassland(4.48%). The size order of capillary porosity is Hippophae rhamnoides stands(52.9%) > Larix principis-rupprechti stands(51.1%) > semi-shady grassland(48.38%) > sunny grassland(46.85%) > Ostryopsis davidiana stands(44.65%). The size order of total porosity is Larix principis-rupprechti stands(58.59%) > Hippophae rhamnoides stands(57.82%) > sunny grassland(57.29%) > semi-shady grassland(53.22%) > Ostryopsis davidiana stands(50.51%).更多还原