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.