【作者】 李永华；

【导师】 卢琦；

【作者基本信息】 中国林业科学研究院 ， 水土保持与荒漠化， 2010， 博士

【摘要】 国内外研究认为,气候变化背景下,未来我国西北干旱地区降雨将有不同程度的增加。为研究我国干旱地区典型植被(唐古特白刺,Nitraria tangutorum Bobr.和泡泡刺Nitraria sphaerocarpa Maxim.)在降雨增加背景下的适应能力及变化方向,本研究于2008年选择内蒙古磴口(年均降水145mm)、甘肃民勤(年均降水115mm)、敦煌(年均降水40mm)设立了三个近自然开放式模拟增水试验平台。同时,在三个研究区域各设置5个增水处理(在三个地区多年平均降雨量的基础上额外增加水0%,25%、50%、75%和100%),每个处理设置4个重复,共20块样地。2008年,在植物生长季节(5月10日-9月10日),分10次增水,每次增水间隔时间约15天;2009年,敦煌重新更换样地并将增水梯度调整为0%,50%、100%、200%和300%(磴口、民勤不变),同时将三个地区增水时间间隔调整为30天。本文利用这一平台研究了:(1)降水—土壤水分动态之间相关关系;(2)水分—δ13C值—叶片性状(包括形态:叶片平均长度、宽度、周长、面积、长/宽和周长/面积比;叶片养分:单位重量/面积叶片氮含量;比叶面积等)之间的相关关系;(3)另外采集了三个地区常见物种(共110个样品),研究了三个地区典型植被叶片性状间相关关系。主要结论如下:(1)单次增水量小于10mm时(实际降落到地面的水分约6.5mm),增水仅能影响表层10cm左右的土壤含水量变化,而且这种影响通常会在7天内消失;单次增水在10-20mm之间时(实际降落到地面的水分约6.5-13mm),表层20cm的土壤能收到微弱的水分增加信号;单次增水超过20mm(实际降落到地面的水分约13mm)时,增加的水分才能明显下渗至20cm土层;在所有调查数据中,即使单次增水量高达29mm(实际降落到地面的水分为18.9mm)或生长季节单次自然降水大于30mm,降水也很难影响50cm以下的土壤水分含量变化。(2)由于白刺(泡泡刺和唐古特白刺)叶片形态为长方形或近椭圆形,所以白刺叶片长、宽变化是决定其形态变化的主要因素。2008/2009年,三个实验区增水最多的样地与对比样地比较,白刺叶片长度(与叶片宽度比较)均表现出优先增加的趋势。2009年敦煌300%增水样地与对比样地比较,泡泡刺叶片长、宽分别增加34%和23%(P<0.01);2008/2009民勤100%增水样地与对比样地比较,白刺叶片长度分别增加11%和10%(P<0.01),而宽度变化不明显(P>0.05);2008年磴口100%增水样地与对比样地比较,叶片长度增加9%(P<0.01),宽度变化不明显(P>0.05),2009年100%增水样地与对比样地比较,叶片长度增加10%(P<0.01),而宽度增加6%(P<0.05)。分析叶片长、宽与样地年水分总量关系发现,每增加100mm水分白刺叶片长度增加0.52cm、而宽度增加0.2cm。(3)白刺叶片形态参数间(叶片平均长度、宽度、周长、面积、长/宽和周长/面积比),以及形态参数与叶片养分(单位重量/面积叶片氮含量)、比叶面积、δ13C值之间关系密切。随样地水分总量的增加,白刺周长、叶面积、比叶面积具有增加趋势,长/宽比、周长/面积比、δ13C值具有降低趋势,而叶片养分随水分增加变化趋势不明显。三个地区不同增水样地内叶片比叶面积、养分含量及δ13C值的差异性比较,大部分没有通过统计假设检验(P=0.05)。(4)叶片周长/面积比与δ13C值具有正相关关系。出现这一规律的原因可能是由于周长/面积比较高的叶片同时具有较高的边界层导度。炎热的生长季节,在气孔开度降低或关闭,水分胁迫增强的情况下,叶片边界层导度的增加有利降低叶片表面温度。叶片表面温度的降低一方面有利于保护叶片细胞免受高温的伤害,另一方面可以保护叶片光合组织并提高叶片光合速率,从而提高叶片水分利用效率。在降雨增加的背景下,白刺叶片长度优先增加,可以减缓叶片周长/面积比下降速率、从而阻止δ13C值(叶片水分利用效率)随水分增加而快速下降的趋势。(5)比较磴口、民勤、敦煌三个地区常见物种叶片性状,发现生长于湿地边缘的敦煌灌木,叶片形态与民勤、磴口灌木差异明显,如敦煌灌木具有更高的叶片长、宽及周长等特征。应用单位面积叶片氮含量将全部样品分3类(类群1,单位面积叶氮含量小于2;类群2,单位面积叶氮含量在2与3之间;类群3,单位面积叶氮含量大于3),然后应用单位重量叶氮含量与比叶面积拟合,结果发现:单位重量叶氮含量随比业面积增加而增加,同时三个类群出现明显策略位移,即比叶面积相同的情况下,单位重量叶氮含量比较,类群3>类群2>类群1;单位重量叶氮含量相同的情况下,比叶面积比较,类群3<类群2<类群1。更多还原

【Abstract】 The previous study suggested that climate change would increase the rainfall in the arid region in Northwest China. The purpose of this study was to examine the adaptive strategies and changes of the typical vegetation (Nitraria tangutorum Bobr and Nitraria sphaerocarpa Maxim) in the arid region due to increasing rainfall in the future. We had established three open-simulated rainfall platforms in Dengkou (average annual rainfall 145mm), Minqin (average annual rainfall 115mm), Dunhuang (average annual rainfall 40mm) in 2008. Based on the average annual rainfall of three research regions, five water gradients (increasing water 0%, 25%, 50%, 75% and 100%, respectively) had been set up. Each gradient has 4 replicates (Total 20 plots in each research region). The simulation rainfall was operated per 15 days from 10 May to 10 September in 2008. In 2009, the simulation rainfall interval was adjusted to 30 days, and the rainfall of Dunhuang were adjusted to 0% , 50%, 100%, 200% and 300% based on the average annual rainfall of Dunhuang. This paper had used the platform of simulation rainfall to study: (1) the relationships between rainfall and soil moisture; (2) the relationships among rainfall,δ13C value and leaf traits (including leaf shape: leaf length, width, perimeter, area, ratio of length to width and ratio of perimeter to area; leaf nutrient: area- and mass- based leaf nitrogen content; specific leaf area); (3) The relationships among the leaf traits of common species (110 samples)that collected from the three research regions. The major conclusions as follows:(1) When single simulation rainfall less than 10mm, the soil moisture of 10cm under surface was affected, and the effect usually disappeared within 7 days. When single simulation rainfall was from 10 to 20mm, soil moisture of 20cm under surface had been able to receive weak rainfall signals within 3 days after simulation rainfall. When single simulation rainfall exceeded 20mm, soil moisture of 20cm under surface could be increased significantly. However, even if single simulation rainfall or natural rainfall was up to 29mm or 30mm during the growing season, soil moisture of 50cm under surface could not be affected at all.(2) Leaf shape of Nitraria tangutorum Bobr and Nitraria sphaerocarpa Maxim was close to oval or rectangular, respectively. Leaf length and width were the major factors to determine the leaf morphological changes of. Nitraria tangutorum Bobr and Nitraria sphaerocarpa Maxim With increasing rainfall, leaf length of Nitraria tangutorum Bobr and Nitraria sphaerocarpa Maxim was prior to increase. Compared the plots with 300% increasing water to 0% in Dunhuang in 2009, the leaf length increased 34% (P <0.01), and the leaf width increased 23% (P <0.01); Compared the plots with 100% increasing water to 0% in Minqin in 2008 and 2009, the leaf length increased 11% and 10%, respectively (P <0.01), and the leaf width did not change significantly (P>0.05). Compared the plots with 100% increasing water to that of 0% in Dengkou in 2008, the leaf length increased 9% (P <0.01), and the leaf width did not change significantly (P>0.05). Compared the plots with 100% increasing water to that of 0% in Dengkou in 2009, the leaf length increased 10% (P <0.01), and the leaf width increased 6% (P <0.05). The relationships among leaf length, width and the total annual rainfall in different plots were that leaf length and width increased with the increasing of total annual rainfall. Moreover, the leaf length and width increased 0.52cm and 0.2cm per 100mm, respectively.(3) There were close correlation among leaf shape (leaf length, width, perimeter, area, ratio of length to width and ratio of perimeter to area), leaf nutrients (based area and mass leaf nitrogen content), specific leaf area andδ13C value. With the increasing of total rainfall, leaf area, specific leaf area increased, however, ratio of length to width, ratio of perimeter to area andδ13C value decreased, and the variations of leaf nutrient had no consistent trend. On the other hand, by compared the plots of different rainfall gradient in the three research regions, there were not an obviously trend of the variations of specific leaf area, leaf nutrient content andδ13C value.(4) There was a positive correlation betweenδ13C value and ratios of perimeter to area. This would be caused by that the leaf with high ratio of perimeter to area always have high leaf boundary layer conductance. In the hot growing season, the increasing of leaf boundary layer conductance would help to decrease leaf surface temperature, which could protect photosynthetic machinery and leaf cells against excessive leaf temperatures when stomata conductance decreasing or close in response to water stress, and thus increase water use efficiency. In fact, leaf length of Nitraria increased priority with increasing rainfall, which could slow down the decreasing rate of ratio of perimeter to area, and preventδ13C value (leaf water use efficiency) from rapid declining with increasing rainfall.(5) Compared the leaf traits of common species in Dengkou, Minqin, Dunhuang, the shrub leaf shapes of Dunhuang, which located at the edge of the wetland, had significant differences with Minqin and Dengkou shrubs. Such as, the shrub leaf of Dunhuang had higher leaf length, width and perimeter.Based on the area-based leaf nitrogen content(Narea), all the samples were divided into 3 groups: group 1; Narea <2, group 2: 2<Narea <3, group 3: Narea >3. Comparing specific leaf area and mass-based leaf nitrogen content, the results showed that mass-based leaf nitrogen content increased with the increasing of specific leaf area. Given the specific leaf area, mass-based leaf nitrogen content decreased successively in group 3, group 2 and group 1, while given the mass-based leaf nitrogen content, specific leaf area increased successively in group 3, group 2 and group 1.更多还原