【作者】 张淑勇；

【导师】 周泽福；

【作者基本信息】 中国林业科学研究院 ， 水土保持与荒漠化防治， 2009， 博士

【摘要】 半干旱黄土丘陵区是我国典型的生态脆弱地区,而水分是制约植被恢复与重建的主要因素。本文针对半干旱黄土丘陵区干旱缺水的主要特征,在山西省中阳县的车鸣峪林场,以白蜡（Fraxinus rhynchophyila Hance.）、刺梨（Rosa roxburghii Tratt.）、火炬树（Rhus typhina L.）、三角枫（Acer buergerianum Miq.）、蒙桑（Morus mongolica Schneid.）、家桑（Morus alba Linn.）、文冠果（Xanthoceras sorbifolia Bunge.）及五角枫（Acer mono Maxim.）8个树种为试验试料,进行盆栽试验设计,运用气体交换和叶绿素荧光监测技术与分析理论,阐明不同树种光合速率、蒸腾速率、水分利用效率等气体交换参数及叶绿素荧光参数在土壤饱和湿度至凋萎湿度内的连续变化过程;揭示不同树种光合特征参数发生显著变化的土壤水分临界点及其变化机制;确定维持不同树种较高光合速率和水分利用效率的土壤水分范围。研究成果对丰富和发展树木光合生理与水分生理研究具有理论价值,对科学指导黄土丘陵区合理树种选择及适地适树具有实践价值。主要研究成果如下:（1）8个树种叶片气体交换参数对土壤水分和光强具有明显的阈值响应①白蜡、刺梨、火炬树、三角枫、蒙桑、家桑、文冠果和五角枫生长适宜的土壤水分范围分别为:39.5%～71.1%、43.6%～73.3%、37.9%～72.4%、37.3%～71.5%、41.6%～79.3%、42.7%～70.3%、42.7%～70.3%、44.2%～73.2%、49%～74.1%。土壤水分最大亏缺分别为:31.7%、36.5%、28.8%、29.8%、34.6%、34.7%、37.6%、33.1%。适宜的光照强度范围分别为:500～1100、300～1100、300～1300、300～900、500～900、500～1100、500～1100、500～1300μmol·m^-2·s^-1。土壤水分最大亏缺越低,表明植物在干旱条件下忍耐干旱的能力也就越强,从土壤水分最大亏缺可以看出主要造林树种抗旱性从高到低依次为:火炬树、三角枫、白蜡、五角枫、蒙桑、家桑、刺梨、文冠果。②8个树种的Φ、R_d和LCP受土壤水分的影响显著,对RWC具有明显的阈值响应。植物对弱光的利用能力由高到低依次为:火炬树、蒙桑、白蜡、家桑、三角枫、五角枫、刺梨、文冠果;不同树种对光合产物的消耗由多到少的顺序为:蒙桑、火炬树、白蜡、家桑、文冠果、三角枫、刺梨、五角枫。耐荫性由高到低的顺序为:刺梨、五角枫、文冠果、家桑、三角枫、火炬树、白蜡、蒙桑。（2）土壤水分影响植物叶片气体交换参数对CO₂浓度的响应过程①研究在不同水分条件下植物叶片气体交换参数对CO₂浓度水平的响应,有助于阐明植物对CO₂浓度和水分条件的响应特性。当RWC>75%时,P_n没有下降,T_r和G_s呈现下降的趋势。RWC为60%～75%时,P_n在达到CO₂饱和点以后缓慢下降,而Tr和G_s急速下降,此时WUE维持在较高值。随着水分胁迫的加剧,P_n、T_r和G_s的CO₂饱和点明显降低,植物的抗旱性增强。在重度水分胁迫下,P_n、Tr和Gs均维持在很低的水平。②8个树种的CE、Γ和R_p对土壤水分的变化具有明显的阈值响应。CE和R_p随着RWC的增加,出现先增大后减小的趋势,且均在RWC为70%左右达到最大值。Г表现出相反的规律,在RWC为60.1%～70.3%左右达到最小值。刺梨的CE值最大,其次为白蜡;8个树种为典型的C3植物;白蜡和刺梨的R_p值较大,约2.1μmol·m^-2·s^-1左右,其它树种的R_p值在1.4～1.8μmol·m^-2·s^-1之间。（3）光合特征参数日动态对土壤水分变化的响应过程与机制①土壤水分显著影响叶片气体交换参数的日动态过程在RWC>75%时,P_n、T_r、G_s均为单峰曲线,WUE差异不显著。当RWC为60%～75%时,白蜡、三角枫、家桑及五角枫没有表现出明显的午休现象,T_r、G_s和WUE为双峰曲线。当RWC达到45%～60%时,P_n、T_r及G_s为双峰曲线,刺梨、三角枫和文冠果的WUE为单峰曲线,其它树种为双峰曲线。在RWC<40%时,P_n和T_r严重午休,表现出典型的“凹”型曲线。除家桑外,其它树种WUE都维持在较高值。②土壤水分显著影响植物光合效率水平在RWC>75%,8个树种之间P_n日均值变动幅度不大。RWC为60%～75%时,除五角枫外,其它树种的P_n维持在最高值,白蜡的P_n最高且与家桑种间差异不明显,文冠果次之。RWC为45%～60%时,五角枫具有最大的P_n,家桑次之,三角枫P_n最低。在RWC>75%,8个树种的T_r有较为明显变化,火炬树最大,三角枫次之,五角枫最低。RWC为60%～75%时,T_r水平维持在最高值,火炬树、家桑和文冠果的T_r较高,依次为刺梨、五角枫、白蜡、三角枫、蒙桑。RWC为45%～60%时,家桑具有最高的T_r。从WUE来看,RWC>75%,五角枫具有最高的WUE,其次为白蜡,三角枫的WUE最低。RWC为60%～75%时,白蜡的WUE最高,其次为蒙桑,火炬树最低。RWC为45%～60%时,树种的WUE维持在最高,白蜡最高,依次为蒙桑、文冠果、五角枫、家桑,刺梨、火炬树和三角枫三者差异不明显。③土壤水分影响光合作用的光抑制,热耗散增加是植物抵御光抑制的主要机制在RWC>75%,树种没有发生光抑制,下午P_n的下降主要是由非气孔限制引起的。RWC为45%～75%时,树种发生了明显的光抑制,随着水分胁迫的缓解,受光抑制的程度降低。超过13:00以后,P_n从气孔限制转向非气孔限制。RWC<40%,植物叶片已发生光氧化破坏。不同水分条件下,林木的NPQ都有午间升高趋势,表明热耗散增加是林木抵御光抑制和缓解光合作用“午休”的主要机制之一。（4）植物叶片气体交换参数具有明显的季节变化和日动态在CK下,家桑和三角枫P_n呈单峰曲线;在T₁处理下,家桑和三角枫P_n最大值和日均值均在7月最高,在9月较低。在5月和9月为双峰曲线,7月为单峰曲线。在T₂处理下,家桑呈单峰曲线,三角枫在5月为双峰曲线,在7月和9月为单峰曲线。家桑的P_n最大值和日均值上表现出明显的季节变化,差异显著。在CK下,家桑在7月的T_r最大,与5、9月差异显著,而三角枫在5月和7月没有明显的差异。两个树种日均值差异显著;在T₁处理下,两树种在5月和7月为双峰曲线;在T₂处理下,两树种在5月出现了蒸腾午休现象,在7月和9月为单峰曲线。家桑T_r要明显高于三角枫;在T₃处理下,T_r一直维持在较低值。两个树种的WUE变化曲线比较平缓,呈不明显的双峰曲线,总体来说,上午的WUE要高于下午。三角枫在不同时期的WUE要高于家桑,在不同水分处理下,家桑和三角枫均在T₂处理下达到最大值,T₁次之,5月份的WUE较高。（5）不同生长期植物光合作用的光抑制、光化学效率及热耗散在CK处理下,家桑和三角枫没有出现明显的光抑制和电子传递效率降低的情况,F_v/F_m、Φ_PSⅡ、NPQ在7月份具有较大值,其次为5月。在T₁和T₂处理下,两个树种都发生了明显的光抑制和电子传递效率降低的情况,7月份光抑制发生的时间提前。家桑在抵抗光抑制,电子传递效率方面要高于三角枫,两个树种都具有较高的耗散过剩光能的能力。在CK处理下,P_n的下降是由非气孔限制引起的。在T₁处理下,上午阶段主要是气孔限制,而在下午转化为非气孔限制,在5月和9月,非气孔限制发生的转折点在13:00,7月份提前到11:00。随着水分胁迫的加剧,植物发生非气孔限制的时间提前。在T₃处理下,P_n的下降主要受到非气孔限制。更多还原

【Abstract】 The semi-arid hill area of Loess Plateau is the typical fragile area in our country. In this region, moisture is the key factor to limit the vegetation restoration and reconstruction. Considering semi-arid hill area of Loess Plateau scarce water resource, eight trees of Fraxinus rhynchophyila Hance., Rosa roxburghii Tratt., Rhus typhina L., Acer buergerianum Miq., Morus mongolica Schneid., Morus alba Linn., Xanthoceras sorbifolia Bunge. and Acer mono Maxim. were chose as experimental material to carry out pot experiment in Chemingyu forestry center, Zhongyang county, Shanxi province. Mensuration technology, an analysis theory of gas exchange and chlorophyll fluorescence, was used. In this study, we clarified continuous variety process of gas exchange parameters, such as photosynthesis rate, transpiration rate and water use efficiency etc., and chlorophyll fluorescence parameters from soil saturation humidity to languish humidity; revealled the critical soil moisture in which photosynthesis characteristic parameters took remarkable changes, and its mechanism of taking remarkable changes; and also confirmed the fitting soil moisture range mainting higher photosynthesis rate and water use efficiency. The results have the theoretic value to the practical meaning of scientific directing the reasonable tree choice and fitting area and trees in semi-arid Loess Hilly region. The main results are as follows:（1） The gas exchange parameters of eight trees have notable threshold response value to soil moisture and photosynthetic active radiation.①The range of relative water content （RWC） being suitable for the growth of Fraxinus rhynchophyila Hance., Rosa roxburghii Tratt., Rhus typhina L., Acer buergerianum Miq., Morus mongolica Schneid., Morus alba Linn., Xanthoceras sorbifolia Bunge. and Acer mono Maxim. was 39.5%～71.1%, 43.6%～73.3%, 37.9%～72.4%, 37.3%～71.5%, 41.6%～79.3%, 42.7%～70.3%, 42.7%～70.3%, 44.2%～73.2% and 49%～74.1% respectively. The maximum soil moisture deficit was 31.7%, 36.5%, 28.8%, 29.8%, 34.6%, 34.7%, 37.6% and 33.1%, respectively. The range of most suitable PAR was 500～1100, 300～1100, 300～1300, 300～900, 500～900, 500～1100, 500～1100 and 500～1300μmol·m^-2·s^-1, respectively. According to maximum soil moisture deficit, the drought resistance are Rhus typhina L., Acer buergerianum Miq., Fraxinus rhynchophyila Hance., Acer mono Maxim., Morus mongolica Schneid., Morus alba Linn., Rosa roxburghii Tratt. and Xanthoceras sorbifolia Bunge. in succession.②The apparent quantum yield （Φ）, dark respiration rate （R_d） and light compensation points （LCP） was affected by soil moisture apparently and had notable threshold response to RWC. According to the utilization of low light intensity, the sequence was Rhus typhina L., Morus mongolica Schneid., Fraxinus rhynchophyila Hance., Morus alba Linn., Acer buergerianum Miq., Acer mono Maxim., Rosa roxburghii Tratt. and Xanthoceras sorbifolia Bunge.. According to the consume photosynthesis production, the sequence was Morus mongolica Schneid., Rhus typhina L., Fraxinus rhynchophyila Hance., Morus alba Linn., Xanthoceras sorbifolia Bunge., Acer buergerianum Miq., Rosa roxburghii Tratt. and Acer mono Maxim.. Based on the ability of shade enduring, the sequence was Fraxinus rhynchophyila Hance., Rosa roxburghii Tratt., Rhus typhina L., Acer buergerianum Miq., Morus mongolica Schneid., Morus alba Linn., Xanthoceras sorbifolia Bunge. and Acer mono Maxim.（2） Soil moisture effected CO₂ response process of gas exchange parameters①Research on CO₂ response process of gas exchange parameters under different soil moisture is meaningful to clarify the response characteristic to CO₂ concentration and soil moisture. When RWC was higher than 75%, T_r and Gs appeared degressive trend, but P_n did not; When RWC was 60%～75%, P_n reduced slowly after CO₂ saturation points, T_r and Gs reduced sharply, while WUE maintained higher value. With the increase of water threatening, the CO₂ saturation points of P_n, T_r and Gs reduced notably and the trait of fighting a drought was improved. P_n, T_r and Gs all kept at very low level under severe water stress.②The carboxylation efficiency （CE）, CO₂ compensation points （Γ） and photorespiration rate （R_p） had notable threshold value to the variety of soil moisture. The CE and R_p increased gradually and reached to the maximal value when RWC was about 70%, and then fell gradually. WhileΓpresented the opposite rule. When RWC was about 60.1%～70.3%, it reached to the minimal value. Rosa roxburghii Tratt. had the highest CE, the next was Fraxinus rhynchophyila Hance.. The results also presented that all of the eight trees are typical C₃ plants, and the R_p of Fraxinus rhynchophyila Hance. and Rosa roxburghii Tratt. was higher than that of others.（3） The response process and mechanism of daily dynamics of photosynthesis characteristic parameters to the variety of soil moisture①Soil moisture effected daily dynamics process of gas exchange parameters notablyWhen RWC was higher than 75%, the curve type of P_n, T_r and Gs was single curve, and the difference of WUE was unapparent; When RWC was 60%～75%, Fraxinus rhynchophyila Hance., Acer buergerianum Miq., Morus alba Linn. and Acer mono Maxim. did not present notable midday photosynthesis depression, and the curve type of T_r, Gs and WUE was double curve; When RWC was 45%～60%, the curve type of P_n, T_r and Gs was double curve, and the curve type of WUE of Rosa roxburghii Tratt., Acer buergerianum Miq. and Xanthoceras sorbifolia Bunge. was single curve, the other trees’curve was double curve; When RWC was lower than 40%, P_n and T_r presented severe middy depression and typical concave curve. The WUE of the other trees all maintained higher value except Morus alba Linn..②Soil moisture effected photosynthesis efficiency significantlyWhen RWC was higher than 75%, the daily average value of P_n in eight trees was equable; When RWC was 60%～75%, the P_n of other trees maintained maximal except Acer mono Maxim., Fraxinus rhynchophyila Hance. had the highest P_n, and had unconspicuous differentia with Morus alba Linn.; When RWC was 45%～60%, Acer mono Maxim. had the highest P_n, Morus alba Linn. was the second, and Acer buergerianum Miq. had the minimal P_n.When RWC was higher than 75%, the T_r in eight trees changed obviously, among them, Rhus typhina L. had the highest T_r, Acer buergerianum Miq. was second, and Acer mono Maxim. had the minimal T_r; When RWC was 60%～75%, the T_r maintained the highest, Rhus typhina L., Morus alba Linn. and Xanthoceras sorbifolia Bunge. had higher T_r than Rosa roxburghii Tratt., Acer mono Maxim., Fraxinus rhynchophyila Hance., Acer buergerianum Miq. and Morus mongolica Schneid.; When RWC was 45%～60%, Morus alba Linn. had the highest T_r.When RWC was higher than 75%, Acer mono Maxim. had the highest WUE, Fraxinus rhynchophyila Hance. was the second, and Acer buergerianum Miq. had the minimal WUE; When RWC was 60%～75%, Fraxinus rhynchophyila Hance. had th highest WUE, Morus mongolica Schneid. was second, and Rhus typhina L. had the minimal WUE; When RWC was 45%～60%, the WUE maintained the highest, Fraxinus rhynchophyila Hance. had the highest WUE, the other was Morus mongolica Schneid., Xanthoceras sorbifolia Bunge., Acer mono Maxim., Morus alba Linn., Acer buergerianum Miq., Rosa roxburghii Tratt. and Rhus typhina L. in turn, in addition, Acer buergerianum Miq., Rosa roxburghii Tratt. and Rhus typhina L. had unconspicuous differentia.③Soil moisture affected photosynthesis photoinhibition, the increase of thermal dissipation was the main mechanism to resist photoinhibitionWhen RWC was higher than 75%, photosynthesis photoinhibition did not occurred in eight trees, the fall of P_n in the afternoon was caused by non-stomatal limitation; When RWC was 45%～75%, obvious photosynthesis photoinhibition appeared in eight trees, and the degree of photoinhibition fell with the melioration of water stress,. The reason causing P_n fall turned from stomatal limitation to non-stomatal limitation after 13:00. When RWC was lower than 40%, the photosynthetic apparatus photooxidation was destroyed. Nonphotochemical quenching coefficient hoist in the middy under different soil moisture, indicating that the increase of thermal dissipation was one of the main mechanism to resist photoinhibition and relief middy photosynthesis depression.（4） The leaf gas exchange parameters had seasonal variation and diurnal dynamicsIn CK condition, the P_n of Morus alba Linn. and Acer buergerianum Miq. showed a single curve; In T₁ disposal, the maximal value and daily average value of Morus alba Linn. and Acer buergerianum Miq. all reached to the highest in July, and to the lowest in September. the P_n showed a double curve in May and September, and single curve in July. In T₂ disposal, Morus alba Linn. showed a single curve, Acer buergerianum Miq. showed a double curve in May, and a single curve in July and September. The maximal value and daily average value of Morus alba Linn. presented obvious seasonal variation, and had conspicuous differentia in different growth period.In CK condition, the T_r of Morus alba Linn. was the highest in July, and had conspicuous differentia with the T_r in May and September, but the T_r of Acer buergerianum Miq. had unconspicuous differentia in May and July. The daily average value of two trees had conspicuous differentia. In T₁ disposal, two trees took on double curve in May and July; In T₂ disposal, two trees took on transpiration middy depression in May, and put up single curve in July and September. The Tr of Morus alba Linn. was higher than that of Acer buergerianum Miq. obviously; In T₃ disposal, the Tr of two trees always maintained very low value.The curve of WUE of two trees changed tardily, and took on unconspicuous double curve. In a word, the WUE in the forenoon was higher than that in the afternoon. The WUE of Acer buergerianum Miq. was higher than that of Morus alba Linn. in different growth period. The maximum value of WUE took on in T₂ disposal under different water disposal, the next is in T₁ disposal. The WUE in May was higher.（5） The photosynthesis photoinhibition, photochemistry efficiency and thermal dissipation in different growth periodIn CK condition, Morus alba Linn. and Acer buergerianum Miq. did not take on obvious photoinhibition and electron transport efficiency depression. The value of maximal quantum yield of PSⅡin the dark （F_v/F_m）, actural photochemistry efficiency of PSⅡ(Φ_PSⅡ) and non-photochemical quenching coefficient （NPQ） was higher in July, the next was in May. In T₁ and T₂ disposal, two trees all took on obvious photoinhibition and electron transport efficiency depression, and the time occurring photoinhibition brought forward. Morus alba Linn. had higher ability to resist photoinhibition and electron transport efficiency than that of Acer buergerianum Miq.. Two trees had higher ability to consume surplus energy.In CK condition, the fall of P_n was caused by non-stomatal limitation. In T₁ disposal, the fall of P_n in the forenoon was caused by stomatal limitation, and then turned to non-stomatal limitation in the afternoon. In May and September, the turning point occurring non-stomatal limitation was at 13:00, and brought forward 11:00 in July. With the aggravation of water stress, the time occurring non-stomatal limitation forward. In T₃ disposal, the fall of P_n was caused by non-stomatal limitation.更多还原