【作者】 熊伟；

【导师】 王彦辉； 徐德应；

【作者基本信息】 中国林业科学研究院 ， 生态学， 2003， 博士

【摘要】 本文针对干旱半干旱地区需增加森林植被和水资源匮乏及容量有限的矛盾，在六盘山北侧的固原市，选择主要的造林树种及典型植被群落作为研究对象，在2001～2002年的生长季期间，利用先进仪器和设备，应用多种方法和手段，从叶片、单株和群落三个尺度系统研究了植物蒸腾耗水的水分生理生态学特征、植物单株和群落的耗水规律以及它们与环境因子之间的影响机理，其结果不仅可为更精确地估计生态用水定额提供科学依据；而且也可为该区域耐旱节水型造林树种草种的选择及合理林分密度的设计起到科学的指导作用。本文主要开展了以下几方面的研究：* 13个主要造林树种草种的水分生理生态学特性研究* 两种密度条件下3种典型植被单株和林分尺度的蒸腾耗水* 两种密度条件下3种典型植物群落的蒸散量及分量组成比例* 13年生华北落叶松林分蒸腾耗水的模拟与预测本论文取得的主要结果：1） 在无水分胁迫盆栽试验条件下，研究和对比了树种的蒸腾耗水特性，结果表明，针叶树种的蒸腾速率和气孔导度最低，阔叶树种最高，灌木树种位于中间；苗木蒸腾速率和气孔导度由小到大的顺序依次为青杄、侧柏、油松、柠条、白蜡、山杏、臭椿、沙棘、白榆和刺槐。2） 苗木蒸腾速率与凌晨叶水势呈正相关，且随叶水势下降蒸腾速率呈指数下降。不同树种由于其耐旱机理和生物学特性的不同造成了两者关系之间的差异，按树种苗木潜在蒸腾速率的大小及其对叶水势下降的敏感度，可将10个树种划分为四类：青杄、侧柏、柠条和白蜡属低蒸腾-低水分敏感型树种；油松属低蒸腾-高水分敏感型树种；白榆、刺槐和沙棘属高蒸腾-高敏感型树种；山杏和臭椿属中蒸腾-中水分敏感型树种。3） 野外人工水分控制试验表明，华北落叶松属于低蒸腾-高水分敏感<WP=5>型树种，其蒸腾作用主要取决于气孔的调节，因此在干旱半干旱树种的选择时可以作为耐旱节水树种；山桃属于高蒸腾-低水分敏感型树种，其耐旱机理属于典型的低水势忍耐脱水耐旱树种，因此在造林时可以选择水分条件较差的阳坡；紫花苜蓿属高蒸腾-高水分敏感型类别，虽然紫花苜蓿耐旱性较强，但具有较强的蒸腾耗水速率，建议在草种选择时要慎重使用。4） 油松和落叶松树干液流日进程都呈现出较明显的昼夜变化规律。液流量在夜间非常微弱，白天持续上升并呈现出双峰或多峰曲线。华北落叶松虽然峰值较低但持续时间较长；油松恰恰相反，峰值较高但持续时间短。油松和华北落叶松整个树干径向不同位点的液流速度由外到内呈现低→高→低的态势，符合Edwards提出的模型。13年生油松和华北落叶松晴天的单株日耗水量分别为0.0058 m3.d-1和0.0074 m3.d-1，均高于阴天的平均值；油松在两种典型天气下日耗水量和耗水率的平均值分别为0.0055 m3.d-1和1.326 m3.m-2.d-1，要高于华北落叶松。以2001年8月29日至8月30日为例，用24h液流量累积值估算华北落叶松单株的蒸腾量为0.00291m3，而“截干测定”结果为0.00317 m3·d-1，比前者高8.2%，这可能与本研究中所使用热脉冲探头的灵敏程度还难以记录较弱液流有关。5）两种密度条件下单株和林分的蒸腾耗水规律不尽相同。从单株尺度看，华北落叶松间伐林分（1667株/hm2）内单株的生长季蒸腾耗水速率要显著大于未间伐林分（2500株/hm2）内的单株，这种差异是因为间伐后林分微气象和土壤水分因子的改变共同引起的；但从林分尺度看，其生长季蒸腾量由原来的192.67mm下降到145.09 mm；与此相仿，山桃和沙棘间伐林分（2500株/hm2）内单株的蒸腾耗水速率在2002年生长季中期显著大于未间伐林分（3333株/hm2），其增加的原因是由于功能叶的日平均蒸腾速率加大或单株叶面积的增加引起的，但从林分尺度讲，山桃未间伐林分的生长季蒸腾量为241.21mm，比对应间伐林分高16.81%，但沙棘未间伐林分的生长季蒸腾量为255.94mm，比对应间伐林分低13.5%。6）生理法与“多株平衡法”测定三种植物群落蒸腾耗水量的结果基本相近。其中，应用生理法估计华北落叶松未间伐和间伐林分的生长季蒸腾<WP=6>量为204.28 mm和168.08 mm，稍高于“多株平衡法”的相应估计值（分别高出5.68%和13.68%），可能与后者过高地估计了枯落物的截持耗水量和观测误差有关；生理法计算未间伐、间伐山桃林分的生长季蒸腾量分别为235.35mm和219.18mm，与“多株平衡法”的估计值很接近，甚至略低于后者；用生理法估计未间伐和间伐沙棘林分的生长季蒸腾量分别为160.2mm和232.77 mm，均小于多株平衡法，这可能与“多株平衡法”中忽略了山桃和沙棘林的枯落物和林下草本植物的截留耗水有关。7）由于间伐引起的林分密度下降不同程度地导致了典型植物群落总蒸散量及其分量组成比例的改变。华北落叶松间伐林分（1667株/hm2）生长季总蒸散量为413.07mm，比未间伐林分（2500株/hm2）低8.02%，其中林分蒸腾量占总蒸散的比例由未间伐的42.9%下降到35.13%而位居第二，林冠层截持耗水比例由未间伐的15.21%下降到11.29%而位居第四；相反，林下植被的蒸散量比例由未间伐的30.48%提高到37.13%而位居第一，枯落物截持耗水比例由未间伐的11.4%提高到16.46%而位居第三。山桃间伐林分（更多还原

【Abstract】 Aiming to solve the contradiction between demand for the extension of forest vegetation and the limited water supply in arid and semi-arid area, the dissertation chose the main afforestation tree species and typical vegetation communities in Gu Yuan City in the north of LiuPanshan mountains, utilized advanced apparatus, equipments and various approaches, at leaf, tree and community scales, systematically studied the ecophysiological characteristics of plant transpiration and water consumption, rules governing water consumption of tree and community and their control mechanism by environmental factors. These studies could provides scientific bases for accurately estimating ecological water consumption and the choice of drought-tolerance and water-saving afforestation tree and herb species, as well as the properly arrangement of stand density. The dissertation involved following aspects:* The study on ecophysiological characteristics of 13 main afforestation tree and herb species* Transpiration and water consumption of the 3 typical vegetation communities, at whole-tree and stand scale, and under two levels of stand density.* Total and component proportion of evapotranspiration of the three typical vegetation communities at two stand density levels.* Simulation and prediction of stand transpiration and water consumption of 13-year-old Larix principi-rupprechtii Major conclusions are summarized as follows: 1) Under the condition of free soil water stress, the transpiration rate of coniferous trees was the lowest, whilst the broad leaved trees were the highest, and the shrub species fell between coniferous species and broad leaved species.When sorted by potential transpiration rate and stomatal conductance, the increasing orders were: Picea wilsonii Mast.、Platycladus orientalis、Pinus tabulaeformis、Caragana korshinskii、Fraxinus americana L.、Prunus armenniaca var. ansu Maxim、Ailanthus altissima、Hippophae rhamnoides、Ulmus pumila L. and Robinia pseudoacacie L..2) Positive correlation was found between the transpiration rate of seedling and predawn leaf water potential, that is, with the decrease of leaf water potential, transpiration rate reduced exponentially. According to the potential transpiration rate and its sensitivity to<WP=9>leaf water potential, the ten tree seedlings could be divided into four groups as follows: Picea wilsonii Mast.、Platycladus orientalis、Caragana korshinskii and Fraxinus americana L., with low-transpiration-rate-and-insensitive-to-water-stress; Pinus tabulaeformis, belonging to low-transpiration-rate-and-sensitive-to-water-stress species; Ulmus pumila L.、Robinia pseudoacacie L.and Hippophae rhamnoides are of high-transpiration and-sensitive-to-water-stress species, and Prunus armenniaca var. ansu Maxim and Ailanthus altissima are of medium-transpiration-rate-and-sensitive-water-stress species.3) The results of ecophysiological measurements under different soil water status indicated that Larix principi-rupprechtii is a low-transpiration-rate-and-sensitive-to-water-stress specie, and its’ transpiration was mainly controlled by stomatal. As a result, Larix principi-rupprechtii can be selected as a drought-tolerance and low water consumption specie in afforestation in arid and semi-arid areas. Prunus davidiana is a high-transpiration-rate-and-insensitive-to-water-stress species that could be planted in sunny slope where soil water content is low. Medicago sativa is a high-transpiration-rate-and-sensitive-to-water-stress species thus should be careful to use the species for artificial grassland establishment.4）Diurnal course of sap flow of Pinus tabulaeformis and Larix principi-rupprechtii changed regularly from night to day, usually it was very weak in nighttime and started to increase continuously to single-peak or multiple-peaks in the daytime. Relatively, the maximum of sap flow of Larix principi-rupprechtii was lower but the period that kept on the peak was longer , on the contrary, the maximum of sap flow of Pinus tabulaeformis was high更多还原