三峡库区消落带芦苇穗期光合生理特性研究

THE RESEARCH OF PHOTOSYNTHETIC CHARACTERS ON PHRAGMITES COMMUNIS(REED)IN HYDRO-FLUCTUATION BELT OF THREE GORGES RESERVOIR AREA

三峡水库运行时,在库区两岸将形成周期性变化的水陆交错地带即消落区,它是陆地和水生生态系统的交错地带,具有生态脆弱性、生物多样性、水分变化周期性和人类活动的频繁性等特点,它对水、陆生态系统具有重要影响。同时,它也面临着严峻的生态与环境问题。以嘉陵江岸边的常见芦苇Phragmites communis(reed)为研究对象,模拟三峡库区消落带土壤含水量变化特征,设置了T1(淹水超过土壤表面2 cm)、T2(土壤含水量为田间持水量的70%—100%)、T3(土壤含水量为田间持水量的40%—60%)3个不同处理组,用嘉陵江江水灌溉芦苇,研究三峡库区不同消落带带位土壤不同含水量条件下芦苇穗期的光合生理生态响应机理,为消落带植被恢复重建和生态环境保护提供理论依据。实验结果表明:土壤不同含水量显著影响了芦苇穗期的叶片水分含量、表观光量子效率(AQY)、暗呼吸速率(Rd)和光补偿点(LCP),而最大净光合速率(Amax)和光饱和点(LSP)没有受到显著影响。T1、T2和T3的最大净光合速率Amax值分别为17.63、19.13和20.97μmol CO2/m2.s。T3的表观光量子效率AQY值为0.055μmol CO2/μmol hotons,且明显(P<0.05)高于T1(0.042μmol CO2/μmol Photons)和T2(0.046μmol CO2/μmol Photons)。这表明T3条件下芦苇的光能转化率高,光合能力强,并且T3的水分利用效率(WUE)和光量子利用效率(QUE)最高,自由水/束缚水比值最小,说明芦苇具有较强的抗干旱的能力。光补偿点LCP中T2的值为35.43μmol/m2.s,该值明显地(P<0.05)高于T1(14.55μmol/m2.s)和T3(12.79μmol/m2.s)。T1、T2和T3的光饱和点LSP分别为912.5、803.89和897.22μmol/m2.s,表明T1条件下芦苇对光的利用范围较宽,并且T1的Ci值最大,光合作用的源物质多,Rd值最小,暗呼吸所消耗的底物少。与其他耐水淹植物相比,T1条件下芦苇具有较高的Amax(17.63μmol/m2.s),说明芦苇具有较强的耐水淹能力。因此,研究表明芦苇不仅具有耐水湿的特点,还具有耐旱性,芦苇可以作为三峡库区消落带植被恢复重建和生态环境保护的禾本科先锋物种。

When the Three-Gorges Reservoir was put into use, riparian zones have been formed on both sides of the reservoir where the water level changes periodically. This ecotone of overlapping water aquatic ecosystem and terrestrial ecosystem, owing to its characteristic ecological vulnerability, biodiversity, water periodical fluctuation and high frequency of human activities, has a profound influence on the water aquatic and terrestrial ecosystems. At the same time, the zones will confront rigorous ecological and environmental problems. Therefore, this paper researches upon the reed （Phragmites communis） which lives on the both sides of Jialingjiang River. For researching on soil moisture contents of the hydro- fluctuation belt in Three Gorges Reservoir Area and provide the theoretic evidences of restoration and rehabilitation of vegetation and eco-environment protection, three different types of water treatments were applied to the reed （Phragmites communis ） to determine its photosynthetic eco-physiological characteristics. The treatments T1 （with soil being complete submerged 2cm）, T2 （with soil water content being 70 % to 100 % of field capacity） and T3 （with soil water content 40% to 60 % of field capacity） simulated the conditions in the hydro-fluctuation belt. During the experimental process, the reed was irrigated with the water from the Jialingjiang River. The results showed that the water content of leaves, apparent quantum yields （AQY）, dark respiration rate （Rd） and light compensation point （LCP） were affected significantly under different soil moisture content conditions, however, there were no significant differences about light saturation point （LSP） and the maximum net photosynthetic rates （Amax）. The maximum net photosynthetic rates （Amax） of the reed （Phragmites communis） were clearly different for the three treatments. The Tl-plants （i. e. the flooded plants） was 17. 63μmol CO2/m^2·s, while the T3-plants （i. e. the ＇dry-treatment＇ plants） was 20.97μmol CO2/m^2·s; In addition, the apparent quantum yields （AQY） of the T3-plants was 0. 055 μmol CO2/μmol Photons, which was higher than that of the T1- and T2-plant significantly, it indicated that T3 had high transitive efficiency of light energy and photosynthetic ability ; moreover, the T3 - plant had the highest water use efficiency（WUE） and light quantum use efficiency （QUE）, but the smallest ratio of free water to bound water, it suggested that the reed（Phragmites communis）had high tolerance to drought. The light compensation point of the T2-plant was 35.43μmoL/m^2 · s, which was higher than that of the T1- and T3-plant significantly, and light saturation point （LSP） of the T1-plant, T2 and T3 were 912.5, 803.89 and 897. 22μmol/m^2 · s respectively, which showed that there was a wider use range of light in group T1. Moreover, Ci of T1 was the highest than that of T2 and T3, but the dark respiration rate was the lowest in group T1, which showed its resource was very plentiful and be consumed rarely. Compared to other plant species, the flooded reed （Phragmites communis） had still the maximum net photosynthetic rate （17. 63μmol/m^2· s） , which indicated that reed also has a high tolerance to inundation. It was also demonstrated that the reed （Phragmites communis） could not only tolerate water submersion and wet condition but also endure drought. Therefore, the reed （Phragmites communis） could be a precedent species for restoration and rehabilitation of vegetation and eco-environment protection in the hydro-fluctuation belt of Three Gorges reservoir region.