【作者】 林玲；

【导师】 郑维列；

【作者基本信息】 西藏大学 ， 生态学， 2008， 硕士

【摘要】 急尖长苞冷杉在色季拉山分布海拔跨度达1500m以上,该树种生长过程中沿海拔梯度与环境间的响应关系尚不清楚。为此,我们选用大多数植物生态学家认为不但采样方便,而且最能反应植物与环境间响应关系的器官――叶,来研究2900m到4300m跨度范围,急尖长苞冷杉沿海拔梯度变化对环境的适应机制。本文通过对其15个连续海拔梯度上叶片的形态、生物量、氮含量和碳同位素的研究,阐明:(1)急尖长苞冷杉叶片性状是如何随着海拔梯度的变化而发生变化的;(2)急尖长苞冷杉叶片氮含量和稳定碳同位素是如何随着海拔梯度的变化而发生变化的,并解释其适应环境,保证碳代谢正常进行的机制;(3)探讨急尖长苞冷杉叶片稳定碳同位素与叶片氮含量及比叶重之间的关系。结果如下:1.随海拔的升高,叶宽不表现明显的规律,这说明叶宽急尖长苞冷杉比较保守的形态性状,受外界环境因子影响较弱。由于随海拔升高温度逐步下降,湿度逐步升高,叶长和叶面积则与海拔梯度变化呈现显著的曲线相关;叶长和叶面积,在2900-3800m随海拔升高而增大,这与该树种喜欢冷湿的特性相关,3800-4300m反而随海拔升高而减小,是由于较低的土壤温度限制了植物根系对土壤水分的吸收,从而受到了一个逐渐增大的水分胁迫。2.叶片生物量(叶片干重和比叶重)在2900-3800m随海拔升高而增大,3800-4300m,随海拔的升高反而减小。这说明,3800m以下叶片同化CO2的能力在逐步增大,从而叶干物质积累增多。3800m以上受CO2浓度降低,紫外辐射加强等胁迫因子影响,叶片同化CO2能力减弱,叶片生物量减少。3.对急尖长苞冷杉叶片中δ13C沿海拔梯度的变化研究,发现δ13C变化范围小且平均值较低,并且叶片δ13C与海拔梯度之间并不是一个线性增加的关系,而是不规则的变化关系。急尖长苞冷杉叶片中δ13C与海拔梯度这种不规则的变化关系,可能是色季拉山不同树种种间对水分竞争以及温度、降水等因子共同作用的结果。4.特定重量叶片氮(Nmass)含量除在3800m有异常变动外,其余海拔带变化不明显;说明叶氮含量与叶干物质含量不随海拔梯度变化而变化,3800m处的异常增大是因为受特定小环境的影响显著。特定面积叶片氮(Narea)含量沿海拔梯度呈显著的曲线相关,在2900-3800m随海拔升高而显著增大,3800-4300m随海拔的升高反而显著减小;这说明3800m以下,随海拔的升高急尖长苞冷杉最大光合能力在逐步增大,3800以上,区域温度下降明显,土壤温度下降也非常明显,较低的土壤温度限制了急尖长苞冷杉根系对土壤水分的吸收从而产生了水分胁迫,外加海拔升高UV-B辐射加强等其它因素影响,急尖长苞冷杉随海拔的升高光合能力减弱。5.对特定面积氮含量与比叶重关系分析表明,Narea与LMA呈显著的正相关(R2=0.85794),是因为急尖长苞冷杉对其生存环境的进化适应而使更多的氮分配到叶片的光合器官内,所以叶片氮含量相对较大,并导致叶片单位面积生物量也增大。更多还原

【Abstract】 Abies georgei var. smithi is mainly occurred at the elevations above 1500m. Whereas the relationships between growing procedure of this tree species along altitudinal gradient and the environmental conditions are unclear. In our present study, leaf ecophysiological traits, which were closely related to the environmental conditions, were measured at an altitudinal range from 2900 to 4300m to study adaptation mechanisms of the Abies georgei var. smithi to varied environments. By measuring stomatal properties, biomass, nitrogen concentration per mass and stable isotope composition of leaves at 15 altitudinal gradient, we were aimed to address the following questions:(1) How leaf traits of Abies georgei var. smithi varied with altitudinal gradients; (2) how leaf chemical elements including nitrogen concentration per mass and stable isotope composition in the leaves of Abies georgei var. smithi varied with altitudinal gradients and tried to explain the mechanisms that maintained balanced carbon metabolism; (3) to find the relationships between stable carbon isotope composition and leaf nitrogen concentration per mass and specific leaf weight (SLW). Results are:1. Leaves wide showed significant orders along with altitudinal gradient, which indicated a relatively conservative property in leaf morphology of the Abies georgei var. smithi and the influence of environment on this property was weak. The leave length and area had curvilinear correlations with variance in altitudes, probably due to decreases in temperature and increases in relative humidity. Leaves length and area increased with altitude at range of 2900-3800m, which might be correlated to a special a property of this tree, which often favors to cold and wet condition. However, the leaves length and area decreased with altitudinal increases at 3800-4300m. The reason for this might be that the low soil temperature restricts plant root to absorb soil water and gradually enlarges water intimidation. In addition, another reason might be that, at high altitudinal site, decreased leaves length and area are just apparent adaptation property of leaves to the cold and dry climatic condition.2. Leaf biomass (dry weight of leaf and SLW) increased with increasing altitudesl at range of 2900-3800m, but decreased with increasing altitudes at range of 3800-4300m. These indicate that the capability of CO2 assimilation in leaves increases gradually below 3800m, which further promotes dry material accumulation of leaves. While above 3800m, due to the decreased CO2 and increased ultraviolet radiation,decreases in leaf biomass production were detected.3. By studyingδ13C in leaves of Abies georgei var. smithi, we found that the variations ofδ13C were small and the mean values were low. In addition, there were no linear relationship betweenδ13C of leaves and altitudinal gradient and the variation were not regular. The irregular correlation betweenδ13C of Abies georgei var. smithi leaves and altitude might be results of joint effect of interspecies competition between different tree species at Sejila mountain and temperature as well as precipitation etc.4. Except were there abnormal variation at 3800m of altitude, the insignificant variation in nitrogen concentration per mass(Nmass)of specific leaf weight at other altitudinal gradients indicated that Nmass of leaf and dry material of leaves do not vary with altitudes. The abnormal increasing in Nmass and dry material content of leaves at 3800m were significantly effected by specific microclimatic condition. Nitrogen concentration of specific leaf area had curvilinear correlation with altitudinal gradients. At the range of 2900-3800m, the nitrogen concentration of specific leaf area decreased significantly with increases of altitude which indicated that below 3800m the maximum photosynthetic capability of the Abies georgei var. smithi increased gradually with increasing altitudes. Above 3800m, the regional temperature falls significantly and the soil temperature decreases significantly as well. The relatively low soil temperature restricts Abies georgei var. smithi roots to uptake soil water and further produce water intimidation. In addition, UV-B radiation increases with increasing altitudes, the photosynthetic capability of Abies georgei var. smithi was weak.5.Analizing nitrogen content of specific leaf area and SLW indicate that there is a positive correlation between Narea and LMA(R2=0.85794)because Abies georgei var. smithi had made an evolutionary adaptation to its environment and allocate much more nitrogen to its photosynthetic organ and causes the biomass of leaf per unit of area increases with the increase of nitrogen concentration of leaves.更多还原