气候变化对高原湿地优势植物生理生态学特性的影响研究

发布时间：2018-09-04 09:43

【摘要】：全球气候变暖已是毋容置疑的事实。IPCC第五次气候评估报告指出,到本世纪末,全球平均地表温度将在1986-2005年的基础上升高0.3-4.8℃,在未来全球变暖的背景下,极端暧事件将进一步增多,热浪发生的频率更高,时间更长。云南高原湿地是我国的重要生态屏障,湿地生态系统极为脆弱,由于地处较高的海拔,对气候变化高度敏感,更容易受到全球气候变暖的影响。高原湿地植物作为生产者,是整个湿地生态系统功能得以维持的核心和基础,是湿地环境质量的重要指示者,也是对气候变化响应最强烈的组分。本研究利用云南高原独特的立体地形与立体气候特点,采用原位异地技术和空间代时间的方法,选择纳帕海(海拔3260m)湖滨带代表性水生植物水葱、茭草,连同其生长的原位土壤单元,一起移至随海拔梯度变化而产生气候条件差异的拉市海湿地(海拔2437m)和昆明滇池流域(海拔1891m),以转移空间研究对象来解决时间尺度限制问题,进而研究气候变化对高原湿地植物的影响,探讨气候变暖对高原湿地生态系统碳平衡的影响途径和作用规律。得到的主要研究结论如下:(1)随着海拔梯度下降的气候条件改变,气温、水温显著升高,光照强度显著降低,降雨量差异显著,CO_2浓度和相对湿度变化不显著。在气候变化对高原湿地水生植物的影响研究中,气温、水温、光照强度是应该考虑的环境影响因子。CO_2既是植物光合作用的必须原料之一,又是构成植物生存环境的一种环境因子,因此,CO_2浓度也作为一个考虑的环境因子。(2)随着气候条件的改变,水葱、茭草两种植物的净光合速率显著升高:水葱由移出地纳帕海移至拉市海湿地和昆明滇池研究地点后,其生长阶段的平均净光合速率,分别增加了19.1%和18.4%;茭草的平均净光合速率,分别增加了43.5%和44.2%。同时,气孔导度、胞间CO_2浓度以及蒸腾速率也随之显著升高;最大净光合速率、光补偿点、表观量子效率显著升高,而光饱和点显著降低;CO_2补偿点显著降低,而CO_2饱和点和羧化效率显著升高。研究表明,不同气候条件下两种植物的净光合速率与气孔导度、胞间CO_2浓度以及蒸腾速率等生理因子均呈显著或极显著正相关;而不同气候条件下的气温,是影响两种湿地植物光合作用的最主要环境因子。两种供试植物虽然都是广布种,但茭草的气孔导度调节机制优于水葱,使得净光合速率与气温的相关性高于水葱,呈现出茭草对气温升高的高适应性。气候变化引起的温度升高极大地促进了水葱、茭草对光能的利用能力,两种植物的光合固碳能力都得到了很大的提高。(3)随着气候条件的改变,水葱、茭草两种植物的株高、生物量均显著增加。其中,水葱由移出地纳帕海移至拉市海湿地和昆明滇池研究地点后,其生长后期的生物量(生物量最大的生长阶段)分别提高了20.3%和22.5%;茭草生长后期的的生物量,分别提高了42.2%和45.3%。但基径的变化却不显著,因此两种植物的茎不够健壮,甚至容易倒伏,从而不利于抵抗外界环境。另外,茭草的株高、生物量对气温升高的适应能力要大于水葱。研究表明,不同气候条件下的气温,是影响两种湿地植物株高、生物量的最主要环境因子。耐受温度范围宽、适应力强的物种能积极响应气候变暖,光合固碳能力也得到较大提高,生物量显著增加,从而对生态系统的碳输入产生积极的影响。(4)随着气候条件的改变,水葱、茭草两种植物的叶绿素含量均显著增加,丙二醛、过氧化物酶、游离脯氨酸以及可溶性糖的含量均有不同程度的降低。随着气候条件的改变,水葱游离脯氨酸含量的季节动态变化幅度逐渐变小;而茭草游离脯氨酸含量的季节动态变化幅度仍然很大;除此之外的其他生理生化特性,茭草升高或降低的幅度均大于水葱。研究表明,不同气候条件下的气温,是影响两种湿地植物生理生化特性(过氧化物酶除外)的最主要环境因子。总体来看,茭草和水葱均体现了广布种对气候变暖的适应能力,但茭草对环境胁迫的适应能力更强,这有利于该物种的进一步生长和扩张,使其在湿地生态系统中持续保持优势地位。(5)随着气候条件的改变,水葱、茭草两种植物的凋落物分解速率均显著增加:水葱由移出地纳帕海移至拉市海湿地和昆明滇池研究地点后,其凋落物的分解速率分别提高了31.9%和28.9%;茭草的分解速率,分别提高了44.7%和43.6%。温度敏感性(Q_(10))的大小顺序为:混合凋落物(3.48)茭草凋落物(3.06)水葱凋落物(2.52),因此,水温升高对茭草凋落物分解的影响要大于水葱。在生长季,水温对凋落物的分解速率影响较大;在冬季,凋落物的基质质量对分解速率影响较大。C含量、N含量、lignin含量、C:N和lignin:N是水葱、茭草凋落物分解的重要预测因子,但在不同的分解时期,这些凋落物基质质量的重要性也存在着差异:N含量、C:N是第1个冬季最重要的影响因子,lignin:N是第2个冬季最重要的影响因子。研究表明,不同气候条件下的水温,是影响两种湿地植物凋落物分解的最重要环境因子,其次是凋落物的基质质量。气候变暖可以加快水葱、茭草等湿地水生植物广布种的凋落物分解,尤其是混合凋落物的分解,进而可能促进高原湿地生态系统的碳输出。(6)气候变暖对高原湿地生态系统碳库的影响不是单方面的,它通过碳输入和输出影响着湿地土壤碳库的平衡。气候因子决定了植被种类的分布、光合产物生成量和凋落物的分解速度,因此对土壤有机碳的固定和矿化分解过程有极大的影响。从整体上讲,气候变化对水葱凋落物分解的促进要大于对其光合固碳能力的促进,而对茭草凋落物分解的促进基本上等于对其光合固碳能力的促进。在气候变暖的大背景下,水葱可能会削弱高原湿地生态系统的碳汇功能,而茭草对生态系统碳汇功能的影响可能并不大。气候变暖对高原湿地生态系统碳平衡的影响,是一个复杂而又综合的过程,还需进一步的深入研究。
[Abstract]:The fifth IPCC Climate Assessment Report pointed out that by the end of this century, the global average surface temperature will rise by 0.3-4.8 degrees Celsius on the basis of 1986-2005. Under the background of global warming in the future, extreme warming events will increase further, the frequency of heat waves will be higher and the time will be longer. Wetland ecosystem is very fragile and sensitive to climate change because of its high altitude. As a producer, plateau wetland plants are the core and foundation of maintaining the function of the whole wetland ecosystem and an important indicator of wetland environmental quality. Using the unique three-dimensional topography and climatic characteristics of the Yunnan Plateau, the representative aquatic plants of the Napa Sea (3260m above sea level) lacustrine zone, including onion and stubble, were selected to move to the altitude along with the in situ soil units. The Lashihai Wetland (2437m above sea level) and the Dianchi Lake Basin (1891m above sea level) with different climatic conditions caused by gradient change were used to solve the time-scale limitation problem by transferring spatial research objects. The effects of climate change on plants in plateau wetland were studied, and the ways and effects of climate warming on carbon balance in plateau wetland ecosystem were discussed. The main conclusions are as follows: (1) With the change of climatic conditions, the temperature, water temperature, light intensity, rainfall, CO_2 concentration and relative humidity are not significantly different. CO_2 is not only one of the necessary raw materials for plant photosynthesis, but also an environmental factor for plant survival environment. Therefore, CO_2 concentration is also considered as an environmental factor. (2) With the change of climate conditions, the net photosynthetic rate of water onion and stubble plants increased significantly: water onion moved from Dinapa. Meanwhile, stomatal conductance, intercellular CO_2 concentration and transpiration rate also increased significantly. Maximum net photosynthetic rate, light compensation point, and surface photosynthetic rate increased by 19.1% and 18.4% respectively. The results showed that the net photosynthetic rate was significantly positively correlated with stomatal conductance, intercellular CO_2 concentration and transpiration rate under different climatic conditions. Temperature under climatic conditions is the most important environmental factor affecting the photosynthesis of the two wetland plants. Although both species are widely distributed, the regulation mechanism of stomatal conductance of the sturgeon is superior to that of the onion, which makes the correlation between net photosynthetic rate and air temperature higher than that of the onion, showing a high adaptability of the sturgeon to temperature rise. With the change of climate conditions, the plant height and biomass of water onion and stubble increased significantly. Among them, water onion moved from Dinapa Sea to Lashihai Wetland and Kunming Dianchi Lake. After the location, the biomass of the late growth stage (the maximum biomass growth stage) increased by 20.3% and 22.5% respectively, and the biomass of the late growth stage increased by 42.2% and 45.3% respectively. But the change of basal diameter was not significant, so the stems of the two plants were not strong enough, and even lodging easily, which was not conducive to resistance to the external environment. The results showed that the temperature under different climatic conditions was the most important environmental factor affecting the plant height and biomass of the two wetland plants. (4) With the change of climate conditions, the chlorophyll content of Allium mongolicum and Zizania latifolia increased significantly, while the contents of malondialdehyde, peroxidase, free proline and soluble sugar decreased to some extent. The seasonal variation range of acid content decreased gradually, while the seasonal variation range of free proline content of the sturgeon was still very large; in addition to other physiological and biochemical characteristics, the increase or decrease range of the sturgeon was greater than that of the onion. On the whole, the adaptability of the widespread species to climate warming is reflected in the water onion and the sturgeon, but the adaptability of the sturgeon to environmental stress is stronger, which is conducive to the further growth and expansion of the species, making it maintain a dominant position in the wetland ecosystem. The litter decomposition rates of Allium mongolicum and Zizania latifolia both increased significantly: the litter decomposition rates of Allium mongolicum increased by 31.9% and 28.9% respectively after it moved from Dinapa Sea to Lashihai Wetland and Kunming Dianchi Lake, and the decomposition rates of Zizania latifolia increased by 44.7% and 43.6% respectively. Water temperature had a greater influence on litter decomposition rate than water onion. In the growing season, water temperature had a greater influence on litter decomposition rate; in winter, litter substrate quality had a greater impact on litter decomposition rate. C content, N content, lignin content, C: N and lignin: N content. It is an important predictor of litter decomposition of Allium mongolicum and Zizania latifolia, but the importance of litter substrate quality varies in different decomposition stages: N content, C:N is the most important influencing factor in the first winter, and lignin:N is the most important influencing factor in the second winter. Climate warming can accelerate litter decomposition, especially the decomposition of mixed litter, which may promote carbon output of plateau wetland ecosystem. (6) Climate warming can accelerate the decomposition of litter of aquatic plants in Plateau wetland. Climate factors determine the distribution of vegetation species, photosynthate production and litter decomposition rate, so they have a great impact on the process of soil organic carbon fixation and mineralization decomposition. The promotion of litter decomposition was greater than that of photosynthetic carbon sequestration, but the promotion of litter decomposition was basically equal to that of photosynthetic carbon sequestration. The effect of climate warming on carbon balance in plateau wetland ecosystem is a complex and comprehensive process, which needs further study.
【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：Q948.112

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