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三峡消落带优势植物狗牙根在水库落干期的叶性状变化

Intra-annual variations in leaf traits of Cynodon dactylon (L.) Pers. during exposure period in riparian zone of Three Gorges Reservoir Area

  • 摘要: 为研究三峡消落带植物叶片功能性状在落干期的变化,于2014年6月和8月,在湿- 干- 湿循环的落干阶段,分别在176、170、164、158 m(不同淹水强度)调查消落带优势草本植物狗牙根(Cynodon dactylon (L.) Pers)的8个叶片功能性状,包括:最大净光合速率(AareaAmass)、比叶面积(SLA)、气孔导度(Gs)、叶片氮含量(NareaNmass)、叶片磷含量(PareaPmass)。结果显示:(1)生长时长(6月和8月)对AareaAmassGs、SLA和Pmass的变异性贡献率与淹水强度相近甚至高于后者,而生长时长对NareaNmassParea变异性的贡献率较低;(2)在8个性状的两两耦合关系中,有5对(Aarea vs. GsAmass vs. Gs,SLA vs. GsAarea vs. NareaPmass vs. Nmass)受到了生长时长的显著影响;(3)AmassNmassPmass在各淹水强度之间无明显变化规律。无论在6月还是8月,158 m的Aarea均大于未淹水的176 m;消落带的SLA显著小于未淹水对照带;Narea的大小依次为:158 m > 164 m > 176 m > 170 m;Parea均表现出消落带高于对照带。研究结果表明,在三峡水库消落带,年内生长时长差异会导致狗牙根的光合能力、比叶面积等多个性状发生显著变化,且对功能性状间的耦合关系影响显著;较少受到生长时长影响的稳定性状NareaParea可能更具群落与环境梯度之间关系的指示作用。

     

    Abstract: To study intra-annual variations in leaf traits of long-term submerged plants in the riparian zone of the Three Gorges Reservoir Area (TGA) during the dry period of the flood-dry-flood cycle, we investigated eight leaf functional traits (maximum net photosynthesis rate (Aarea, Amass), stomatal conductance (Gs), specific leaf area (SLA), leaf nitrogen concentration (Narea, Nmass), and leaf phosphorus concentration (Parea, Pmass)) of Cynodon dactylon ( L.) Pers. at four elevations (176, 170, 164, and 158 m) in June and August 2014. Results showed that: (1) Exposed period significantly contributed to variations in Aarea, Amass, Gs, SLA, and Pmass (more than 26% of total variation), similar to or even higher than submergence intensity. However, exposed days contributed little to variations in Narea, Nmass, and Parea (less than 15%). (2) Five bivariate relationships between leaf traits (Aarea vs. Gs, Amass vs. Gs, SLA vs. Gs, Aarea vs. Narea, Pmass vs. Nmass) showed significant changes between two exposed periods. The intercept of Amass vs. Gs changed significantly between June and August. (3) Amass, Nmass, and Pmass showed no obvious trends in submergence intensity between June and August; Aarea was significantly higher at 158 m than at 176 m regardless of month; SLA and Parea were significantly lower in the riparian zone (170, 164, and 158 m) than at 176 m; variation in Narea was in the order: 158 m > 164 m > 176 m > 170 m. These results suggest that annual exposed period can lead to significant variations in C. dactylon leaf traits, as well as the relationships between them. As Narea and Parea were stable traits (less affected by exposed days and submergence intensity), they may be candidate predictors for the structure and function of the TGA riparian ecosystem.

     

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