【作者】 秦景；

【导师】 贺康宁；

【作者基本信息】 北京林业大学 ， 水土保持与荒漠化防治， 2011， 博士

【摘要】 本文以黄土高寒区主要造林树种沙棘(Hippophae rhamnoides Linn.)、沙木蓼(Atraphaxis bracteata A. Los.)、银水牛果(Shepherdia argentea (Pursh) Nutt.)、白桦(Betula platyphylla Suk.)、华北落叶松(Larix principis-rupprechtii Mayr.)和青海云杉(Picea crassifolia Kom.)为试验材料,通过系统研究不同干旱胁迫、盐胁迫条件下植物的生长形态、叶片水分和光合生理响应以及林木蒸腾耗水规律,深入探讨该区主要造林树种的抗旱耐盐机理及耗水特性,为不同立地条件下植被恢复中抗逆树种的筛选及栽培奠定基础,进而为当地的生态环境建设及退耕还林还草工程提供科学的理论依据。本文主要得出以下结论：(1)黄土高寒区主要造林树种抗旱特性干旱胁迫对沙棘、白桦和银水牛果三种幼苗的株高生长、单株叶面积、生物量均产生了显著抑制,且干旱胁迫程度越高,下降幅度越大。总体来说,白桦的生长及生物量对干旱胁迫反应最剧烈,沙木蓼次之,银水牛果和沙棘的表现最好。干旱胁迫下沙棘和银水牛果幼苗光合作用的降低在W1(>22.7%)至W3(7.6%-15.1%)处理下为气孔限制,在W4(<7.6%)处理下为非气孔限制因素所致。沙木蓼幼苗光合作用的降低在W1和W2处理下为气孔限制,在W3和W4处理下为非气孔限制因素所致。而白桦幼苗光合作用的降低在W2(15.1%～22.7%)处理下就转为非气孔限制。(2)黄土高寒区主要造林树种耐旱机理判别萎蔫试验中,白桦土壤水分下降最快,在萎蔫试验30天、土壤含水量降低至5.75%时,出现严重的萎蔫现象。沙棘的土壤水分下降最慢,且忍耐干旱的时间最久,在45天、土壤含水量降低至3.85%时,才出现萎蔫。沙木蓼和银水牛果在40天时出现萎蔫。由此判断,白桦的耐旱性最弱,银水牛果和沙木蓼的耐旱性强,沙棘的耐旱性最强。根据耗水指数排序,耐旱性强弱为：沙棘>银水牛果>沙木蓼>白桦。四种植物的清晨叶水势与土壤含水量的关系可以应用y=a+b/x拟合；叶水势与土壤水势的关系可以应用y=axb拟合。利用土壤水分和土壤水势的两种判别模型,四种植物的判别结果一致,均为低水势忍耐脱水耐旱树种。(3)黄土高寒区主要造林树种耐盐生理沙棘和白桦幼苗叶片的光合能力即使在最低浓度下(200 mmol·L-1 NaCl)也受到了强烈的抑制,而沙木蓼尤其是银水牛果光合能力仅在最高盐浓度下(600 mmol·L-1 NaCl)受到明显的抑制。从整体表现看,银水牛果的耐盐性最强,沙木蓼次之,沙棘和白桦最弱。盐胁迫下,四树种叶片叶绿素含量均显著下降,植物叶片Na+含量显著增加,而K+、Ca2+的吸收受到抑制,造成植物体内离子不平衡。本研究进行了30d的盐胁迫持续观测,结果表明：白桦幼苗在400 mmol·L-1 NaCl处理23 d、600 mmol·L-1 NaCl处理18 d时全部死亡。沙棘幼苗在600 mmol·L-1 NaCl处理22 d时全部死亡。银水牛果和沙木蓼即使在最高盐浓度处理30 d时,叶片特性无明显变化。因此,银水牛果和沙木蓼都可以忍耐600 mmol·L-1 NaCl长达30d左右属于极其耐盐的树种。植物在短期盐胁迫时,气孔因素起主要作用,而受长期盐胁迫时,非气孔因素(如叶绿素含量降低、离子失衡、光合机构受损等导致的光合能力的下降)逐渐成为限制光合作用的主要因素,而且树种耐盐性越弱,NaCl浓度越高,由气孔限制转为非气孔限制的时间越早。(4)黄土高寒区主要造林树种耗水特性青海云杉、华北落叶松两树种各月份液流速率呈明显的节律性。各树种液流通量变化趋势与液流速率一致,但因胸径差异,值差异较大。整个生长季,青海云杉1、青海云杉2、华北落叶松和沙棘耗水总量分别为449.46、3708.65、663.33和75.94 kg。四树种边材液流变化与主要环境因子之间存在显著的相关性,青海云杉、华北落叶松和沙棘三树种与太阳辐射、空气温度、风速之间呈极显著正相关,与相对湿度呈极显著负相关,可见树木边材液流受各种气象因子的综合影响。更多还原

【Abstract】 With main plantation tree species in high-cold region of Loess Plateau:Hippophea rhamnoides Linn., Atraphaxis bracteata A. Los., Shepherdia argentea (Pursh) Nutt., Betula platyphylla Suk., Larix principis-rupprechtii Mayr. and Picea crassifolia Kom. as test materials, this paper comprehensively studied the physiological responses of plant growth, leaf water relations and photosynthetic characteristics to draught and salt stress, as well as the laws of water consumption of these tree species. The aim of this paper was to deeply analyzed the drought and salinity resistant physiology and water consumption characteristics of the four main plantation tree species in order to pave the way for screening and cultivation of adverse-resistant plants during vegetation recovery period in different site conditions and also to provide a scientific theoretical foundation for the ecological environment construction and returning farmland to forests or grassland project. By means of research, main conclusions are elicited as follows:(1) Drought resistant characters of the four main plantation tree species in high-cold region of Loess PlateauDrought stress significantly decreased stem height, leaf area per plant, biomass yield of H. rhamnoides, B. platyphylla and S. argentea seedlings and the decrement was greater under higher drought stress. Overall, the growth and biomass yield of B. platyphylla seedlings were most sensitive to drought stress, and next was A. bracteata, H. rhamnoides and S. argentea seedlings could well perform under drought stress.Drought-induced inhibition of photosynthesis in the leaves of H. rhamnoides and S. argentea seedlings was attributed to stomatal limitations under W1 (> 22.7%), W2 (15.1%-22.7%) and W3 (7.6%-15.1%) treatments, and attributed to non-stomatal factors under W4 (< 7.6%) treatment. The decrease of photosynthesis in the leaves of A. bracteata seedlings was caused by stomatal limitations under W1 and W2 treatments, and caused by non-stomatal factors under W3 and W4 treatments. In contrast, non-stomatal limitations became a leading factor in the decline of photosynthesis in the leaves of B. platyphylla seedlings from W2 to W4 treatments.(2) Discrimination results of drought tolerant mechanism of the four tree speciesIn the wilting experiment, the largest decline of soil relative water content of B. platyphylla seedlings was found and serious wilting symptoms occurred on 30 d when soil relative water content dropped to 5.75%. H. rhamnoides seedlings had the highest enduring capability to drought stress compared to other three tree species and wilting symptoms were obtained on 45 d when soil relative water content dropped to 3.85%. Meanwhile, A. bracteata and S. argentea seedlings could endure drought stress for 40 days. According to soil water depleted index, and the magnitude of drought tolerance in decreasing order was H. rhamnoides> S. argentea> A. bracteata> B. platyphylla.Relationships between leaf water potential of the seedlings and soil water content and soil water potential were studied in detail. For the optimum effect, this relationship can be expressed by regression equation:y= a+blx for leaf water potential and soil water content and regression equation:y= axb for leaf water potential and soil water potential. Mechanism and types of drought tolerance of tree species can be recognized using the existing models and the discrimination results of drought tolerant mechanism of the four tree species are the same, i.e. drought tolerance by dehydration tolerance at low tissue water potential.(3) Salt resistant physiology of the four main plantation tree species in high-cold region of Loess PlateauSignificant salt-induced suppression of leaf photosynthetic capacity of A. bracteata and S. argentea seedlings appeared only at the highest salinity level (600 mmol·L-1 NaCl solution), whereas rapid decline of photosynthesis of H. rhamnoides and B. platyphylla seedlings was found even at the lowest salinity level (200 mmol·L-1 NaCl solution). Compared with the control, the content of chlorophyll a (Chla), chlorophyll b (Chlb), chlorophyll (Chi) and carotenoid (Car) decreased significantly under salt stress. Salinity also induced an excessive accumulation of Na+ and a severe inhibition of K+ and Ca2+ in the leaves of plants, consequently leading to ionic imbalance. On the whole, the magnitude of salinity tolerance in decreasing order was S. argentea> A. bracteata> H. rhamnoides> B. platyphylla.This experiment was performed for 30 d under native condition in the open air and our results showed that, morphological symptoms of salt injury in H. rhamnoides seedlings occurred on the 10th day, and all seedlings were dead on the 20th day under 600 mmol-L-1 NaCl solution. As for B. platyphylla seedlings, all seedlings were dead on the 23th day under 400 mmol·L-1 NaCl concentration and on the 18th day under 400 mmol·L-1 NaCl. In contrast, S. argentea and A. bracteata seedlings could survive at the highest salinity level (600 mmol·L-1 NaCl solution) for above 30 days without obvious change of leaf characters, indicating that the two species are highly tolerant to salinity.Sanility-induced inhibition of photosynthesis in the leaves was mainly attributed to the stomatal efficient closure predetermined by a low water potential in leaves (i.e. stomatal limitations) in short term, and was mainly due to non-stomatal limitations in long run, including disorder of physiological metabolic of leaves, suppression of chloroplast capacity to fix CO2 caused by severe cellular dehydration, photosynthetic capacity decline caused by degradation of the photosynthetic pigment, ionic imbalance and toxicity, and so on. Moreover, the higher NaCl concentration, the earlier time changing from stomatal limitations into non-stomatal limitations.(4) Water consumption characteristics of the four main plantation tree species in high-cold region of Loess PlateauSap flow fluctuations of H. rhamnoides, L. principis-rupprechtii and P. crassifolia were measured continuously with Granier’s thermal dissipation probe (TDP). It was obtained that sap flow velocity of L. principis-rupprechtii and P. crassifolia had circadian rhythmicity during growing season. Sap flow flux of these three species had the same change rule as sap flow velocity but there were remarkable differences in value of sap flow flux among species because of the breast height. Total water consumption of the tree species during growing season was 449.46 kg for P. crassifolia No.1,3708.65 kg for P. crassifolia No.2,663.33 kg for L. principis-rupprechtii and 75.94 kg for H. rhamnoides, respectively.Correlation analysis between meteorological factors and sap flow velocity of different plants indicated that sap flow velocity was closely related to the fluctuation of meteorological factors. Sap flow velocity had an obviously positive correlation with solar radiation, air temperature and wind speed, but it had a highly negative correlation with relative humidity, indicating that sap flow velocity of tree species was comprehensively impacted by meteorological factors.更多还原