【作者】 张宁南；

【导师】 徐大平；

【作者基本信息】 中国林业科学研究院 ， 森林培育， 2010， 博士

【摘要】 过去20年桉树在华南地区大面积发展,目前桉树人工林种植面积达250万hm2。在其它国家桉树经常被指责消耗大量水导致水资源减少。本文以广东雷州半岛沿海平原区和高要丘陵山区的桉树人工林为研究对象,针对这两种主要立地类型桉树人工林树干液流、树木蒸腾耗水、林分蒸散与水量平衡各分量及相关的环境因子进行了连续系统的研究。获得以下几方面的结论与认识:1、桉树液流密度及影响因素:桉树树干形成层以内木质部不同深度的液流密度不同,其中靠近形成层部分液流速度较快,但各层都具有相同的日变化趋势;不同直径尾叶桉的日液流密度具有相似日变化趋势,大树较小树的液流密度高主要与大树更多受光有关;树干液流与饱和蒸汽压差（Vapour pressure deficit, VPD）和太阳辐射相关性极显著;桉树人工林边材面积与胸径具有显著的相关性,利用边材面积进行单株向林分尺度耗水的转换是可行的。2、沿海平原区桉树人工林耗水特征:对广东省雷州半岛沿海平原区两种主要土壤类型下（河头、纪家）的4 a生尾叶桉（Eucalyptus urophylla）耗水量（用热脉冲法）与水量平衡进行为期1 a的观测。河头是保水能力差的浅海沉积物发育的砂质土,纪家为玄武岩发育的砖红壤。河头、纪家尾叶桉人工林日平均液流密度分别为2772±66、1839±86 L·m^-2·d^-1,这与土壤水文特征及林分边材面积差异有关;旱季的日均液流密度值为2477±86、1715±73 L·m^-2·d^-1,而雨季则为3 241±88、1 970±67 L·m^-2·d^-1,桉树林分树液流密度具有相似的季节变化节律;雨季由于雨热同期,液流密度值相对较高,而旱季由于土壤水分相对短缺,液流密度值明显减少。河头与纪家尾叶桉人工林林分日均耗水量为1.49、1.53 mm,年耗水量分别为542、559 mm,占年降水量的35 %和36 %,其中旱季日耗水量分别为1.25、1.35 mm·d^-1,雨季为1.83、1.69 mm·d^-1;木材的水分利用效率4.75×10-3、4.24×10-3 m3·m-3 （木材/水）;开阔的林冠及较小的叶面积指数、旱季时土壤有效水的减少及较低的VPD等在不同程度上都限制了桉树的耗水量。河头与纪家的年蒸散量分别为1040和1081 mm,占同期降水量的67.9 %和70.2 %。旱季时蒸散量大于降水量,表明蒸散可用深层土壤水,土壤水在雨季可以得到补充。由于土壤质地的差异,纪家的持水性高,有更多的水分以地表蒸发的形式散失。砂质土的河头持水性差,但渗透性高,旱季时桉树人工林有可能吸收深层土壤水。3、丘陵山区桉树人工林耗水特征:用热扩散法（Thermal dissipation probe method, TDP）测定高要山地的4-6 a生尾巨桉（E. urophylla X grandis）日均液流密度分别为1032±30、867±22和659±26 L·m^-2·d^-1,其中旱季日均液流密度值分别为782±32、739±25和529±30 L·m^-2·d^-1,而雨季则为1 279±41、972±31和798±36 L·m^-2·d^-1。另外随着尾巨桉林龄增加液流密度呈下降趋势。日耗水量均值分别为1.22、1.10和0.99 mm·d^-1,年耗水量分别为443.6、402.0和362.6 mm,占年降水量的26.7 %、24.5 %和29.0 %;3 a年均耗水量为402.8 mm（占年降水量26.5%）,其中旱季为162.9 mm、雨季为239.9 mm,分别占同期降水量的77.8%和18.3%。年蒸散量分别为944.3、862.1和843.0 mm,分别占年降水量的56.9 %、52.5 %、67.3 %。桉树人工林0¹00cm土层的最大蓄水量为470.06 mm,其中非毛管蓄水量为98.22mm,土壤总孔隙度和非毛管孔隙度随土壤深度增加呈递减趋势;0¹0cm土壤层的初渗速率和稳渗速率分别为25.03和8.83 mm·min^-1,且随土壤深度增加而逐渐减小。对高要山地集水区4 a生尾巨桉人工林耗水量与水量平衡进行了为期3 a的观测,平均年输入降水量1517.8 mm,其中径流量、蒸散量、土壤蓄水量变化分别为637.3、883.2、^-2.6 mm,分别占年降水量42.0%、58.2 %、-0.2%;蒸散量中冠层截留量、树木蒸腾耗水量、地表蒸发量分别为202.2、405.3、275.7mm,分别占降水量的13.3%、26.7%、19.3%。热脉冲法和热扩散法（TDP）均被认为是准确、有效测定树木蒸腾耗水量的方法,可适用人工林水量平衡方面研究。以上研究结果表明在当降水量超过1200mm,桉树人工林不会抽取地下水及对区域水量平衡有负面影响。更多还原

【Abstract】 Plantations of Eucalyptus and other exotic species have been extensively established in southern China during the past 20 years. Over 2.5 millions hm2 of Eucalyptus plantations have been established in southern China. In other countries, Eucalyptus have sometimes been shown to have high annual water use, which leads to depletion of water resource. This dissertation reports studies on whole-tree transpiration （sap flow）, canopy interception, soil evaporation, soil moisture dynamics, weather conditions and tree growth conducted for 1 year in 4-year-old Eucalyptus urophylla trees grown at two sites （Hetou and Jijia） in the coastal flat area of the Leizhou peninsula and for 3 years in a of 4-6-year-old plantation of E. urophylla X grandis in hilly area in Gaoyao of Guangdong province, China.Investigatations the characteristics of sap flux density （SFD） of 4-year-old E. urophylla trees in Leizhou using heat pluse method and 4-year-old E. urophylla X grandis trees in Gaoyao using heat dissipiation probe method, respectively. Results indicated that SFD of outer sapwood moved faster than the inner one. The daily patterns of SFD of trees of different sizes of diameter were similar pattern, and larger trees had higher SFD than smaller ones probably due to better radiation exposure. Among meteorological factors, solar radiation and vapour pressure ddficit （VPD） were the main factors controlling the sap flow.The results also revealed that the relationship of between sapwood area and diameter at breast height （DBH） in Eucalyptus urophylla and E. urophylla X grandis trees were highly significant and therefore it was possible to use the sapwood area to scale up estimation of water use from individual trees to a stand level. The mean daily SFDs in Hetou and Jijia in dry season were 2477±86 and 1715±73 L·m^-2·d^-1, while in wet season 3241±88 and 1970±67 L·m^-2·d^-1, with annual averages of 2772±66 and 1839±86 L·m^-2·d^-1, respectively. Annual mean daily water use Eucalyptus plantations at Hetou and Jijia were 1.49 and 1.53 mm·d^-1 (1.25 and 1.35 mm·d^-1 in dry season, 1.83 and 1.69 mm·d^-1 in wet season), respectively. Annual total water use calculated from sap flow were 542 and 559 mm, respectively, which were equivalent to 35 and 36 % of annual rainfall. Water use efficiency, defined as total stem volume growth per unit of water transpired, was 4.75×10-3 m3·m-3 at Hetou and 4.24×10-3 m3·m-3 at Jijia. Low water use in this region may have resulted from combined effects of several factors, including open canopy and low leaf area index, soil water decline in the dry season, and low VPD that limited water consumption of the trees.The annual evapotranspiration （ET） （October 1999 to September 2000） in Hetou and Jijia were 1040 and 1081 mm, which were equivalent 67.9 % and 70.2 % of annual rainfall. Dry season water balances showed ET exceeded or approached rainfall in the same period, indicating water use from soil water storages was associated with soil water depletion, particularly at Hetou. However, soil water storages were replenished by high water recharge in wet season. The differences in soil properties between the two sites resulted in greater soil water store at Jijia that provided a supply for soil evaporation. Sandier soils at Hetou with poor water holding capacity had greater drainage in wet season and higher abstraction in dry season from water storages of deep soil.The annual mean daily SFD of 4-6-year-old E. urophylla X grandis plantations in Gaoyao over the three years were respectively 1032±30, 867±22 and 659±26 L·m^-2·d^-1, and those in dry season were 782±32, 739±25 and in wet season 529±30 L·m^-2·d^-1 and 1279±41, 972±31 and 798±36 L·m^-2·d^-1, respectively. Mean values of daily water use in the three years were 1.22, 1.10 and 0.99 mm·d^-1. Water use of plantations per annum was 443.6, 402.0 and 362.6 mm respectively, or 26.7 %, 24.5% and 19.3 % of annual rainfall, respectively. Annual water use were 402.8 mm, or 26.5 % of annual rainfall in the three years,of which 162.9 mm occurred in dry season, accounting for 77.8% of rainfall in the same period and 239.9 mm or 18.3 % of rainfall in wet season. The maximum water-capacity of the soil layer from 0 to 100 cm depth is 470.06 mm, and the non-capillary water-capacity accounts for 20.90 % （98.22 mm） of the total. Both of the total and non-capillary porosities show a decreasing trend with the increasing soil depth. The initial and steady infiltration rates in the surface (0^-10 cm) are 25.03 and 8.83 mm·min^-1 respectively, and also decrease with the increasing soil depth. Average annual precipitation was 1518 mm, and 42.0 %, 58.2 % and -0.2 % of which were allocated to total runoff （637.3 mm）, ET （883.1 mm） and change of soil water storage (^-2.6 mm). Annual values of ET were 944.3, 862.1 and 843.0 mm, which were equivalent to 56.9 %, 52.5 % and 67.3 % of annual rainfall. Annual ET was allocated to 202.2 mm （13.3 %） of canopy interception, 405.3 mm （26.7 %） of tree transpiration and 275.7 mm （19.3%） of soil evaporation。 Both the heat pulse method and heat dissipation probe （TDP） method were proved to be valid and accurate way to measure transpiration by eucaypt platnations and recommended for wider application in water balance studies of tree plantions.Comparison of the water balance of the above eucalypt plantations with other type of plantations in the same region did not support the opinion that eucalypt plantation will deplete ground water reserves and negatively affect regional water balance in regions with annual rainfall of≥1200 mm.更多还原