Submergence tolerance is crucial when thinking in promising species for restoration of ecosystems prone to suffer extreme flooding events. In this study, two-year-old seedlings of Distylium chinense were subjected to one field study and five controlled experiments: unsubmerged and watered daily as controls (CK) and completely submerged for 30, 60, 90 and 120 days, respectively followed by a 60-day recovery period to test the submergence tolerance. The results showed that the survival decreased with the increasing flooding duration. Different submergence duration treatments affected dry mass accumulation and carbohydrate content of roots, stems and leaves. Flooding stress affected the activities of pyruvate decarboxylase (PDC), ethanol dehydrogenase (ADH) and lactic dehydrogenase (LDH) enzymes, which indicated the roots and leaves adapt to long-term flooding by reinforcing their anaerobic respiration and activities of ADH were higher than those of LDH for roots and leaves with stronger alcoholic fermentation mainly. After de-submergence, the recovery patterns of carbohydrate were coincided with those of dry mass accumulation of the roots, stems and leaves. A significant regression equation analysis showed root starch content and dry mass accumulation were the major factors affecting the seedling survival. And D. chinense accumulated substantial amounts of carbohydrate before submergence and invested more in roots and stems than in leaves, which enhances long-term survival under submergence. Carbohydrate storage is a key functional trait that can explain high survival under submergence. D. chinense may have adopted a suite of growth and respiratory metabolic adaptation strategies to survive long-term submergence.

To investigate whether Distylium chinense can adapt to the artificial water-level-fluctuation zone, which has longer submergence duration and different hydrological regime, its seedlings were submitted to the un-submerged and completely submerged treatments with submergence under 2m water depth. Four different submergence durations included 15, 30, 90 and 120 d and meanwhile with two recovery growth durations of 15 and 60 d after de-submergence. The survival, main stem length, number of epicormic shoots, number of leaf showing chlorosis/senescence, stem basal diameter, aboveground biomass, belowground biomass, root/shoot ratio and total biomass were determined at the end of the submergence experiment. In addition, the recovery growth rate of seedlings was calculated after a 60-day recovery period. The results showed that D. chinense had the high survival and good recovery growth after long-term submergence, which indicated that D. chinense is a relatively high submergence-tolerant species. Thus, D. chinense can be considered as one of the native pioneer tree species in the revegetation and restoration of water-level-fluctuation zone in Three Gorges Reservoir region, China.

Phalaenopsis aphrodite Rchb. F. is a plant of great ornamental and economic value, and its growth has strict requirements in terms of environment. In order to establish the rapid propagation of Phalaenopsis aphrodite Rchb. F., this study used the popular large-flowered variety ‘RED SUN’, which is found on the market, as the material, and studied the effects of pedicel taking time, site, plant growth regulators, and organic substances on the establishment of a regeneration system. The results indicated that the best combination of initiation culture was collecting peduncles in January + upper position of peduncles + 0.1% HgCl₂ sterilization for 8 min. The best recipe for inducing adventitious buds was MS + TDZ 0.4 mg/L + NAA 0.5 mg/L. The optimal combination for adventitious bud propagation was MS + TDZ 0.2 mg/L + NAA 0.4 mg/L. The best recipe for strong seedling from aseptic seedlings was MS + NAA 0.4 mg/L + banana powder 20 g/L + tryptone 2 g. The best recipe for rooting for aseptic seedlings was 1/2 MS + IBA 0.5 mg/L + charcoal 2 g/L. The best combination of acclimation and transplanting for Phalaenopsis was using sphagnum in the training seedling room, which produced a seedling survival rate of 97%. Our findings, therefore, demonstrate the methods of rapid breeding of the Phalaenopsis orchid, which provide a scientific basis for the conservation of this species.

The reservoir water level fluctuation zones (RWLFZs) and the natural riparian zones (NRZs) are two riparian ecosystems with dramatically opposite hydrological rhythms that notably influence the plant guilds. However, little is known about the discrepancies of the functional traits and niche characteristics of plant guilds in the RWLFZs and NRZs under different flooding rhythms. The aims of this study were to assess the divergent influence of natural and non-seasonal hydrological fluctuations on functional traits and niche characteristics of plant guilds. The results showed that 78 vascular plant species were identified in the riparian zones of the Xiangxi River basin. The dominant species were annuals in the two riparian ecosystems and their percentage increased temporally from 65.79% in the NRZs to 67.34% in the RWLFZs. Compared with the NRZs, the specific leaf area, vegetation coverage and the aboveground biomass in the RWLFZs significantly increased by 74%, 27% and 19.6%, respectively, while the water-use efficiency of the RWLFZ decreased by 59.6% and there was no significant difference in the net photosynthetic rate between them, which showed that annuals in the RWLFZs adopted the R adaptation strategy of being fast-growing with a short lifespan and quickly acquiring and investing resources by altering leaf morphology, including expanding the leaf area. The Simpson dominance index of RWLFZs was significantly higher than that of NRZ. Thus, counter-seasonally hydrological alterations had significant effects on functional traits of dominant species in the RWFLZs. Moreover, the highly adaptable and widely distributed species with larger niche breadths and high important values usually had a higher niche overlap value in the RWLFZs than in the NRZs, which showed that the competition in the plant communities after experiencing anti-seasonal flooding was much more intraspecific than interspecific and would facilitate the expansion of species niches. Our findings imply that the species with large niche breadths and high important values should be prioritized in ecological restoration efforts in the newly formed hydro-fluctuation zones of the TGR.

The reservoir water level fluctuation zones (RWLFZs) and the natural riparian zones (NRZs) are two riparian ecosystems with the dramatically opposite hydrological rhythms which notably influence the plant guilds. However, little is known about the discrepancy of functional traits and niche characteristics of plant guilds in the RWLFZ and NRZ under different flooding rhythms. Here the RWLFZs (degraded riparian zones) and NRZs were chosen in the Xiangxi River Basin of the Three Gorges Reservoir (TGR) to investigate the variation in plant community structure, the spatial patterns of diversity, key functional traits and niche characteristics of dominant plant populations. The results showed that a total of 78 vascular plant species were identified in the riparian zones of Xiangxi River Basin. Most of the dominant species were annual herbs in the two riparian ecosystems and the percentage of annual dominant species increased from 65.79% in the NRZ to 67.34% in the RWLFZ. Compared with the NRZ, the specific leaf area, vegetation coverage and the aboveground biomass in the RWLFZ significantly increased by 74%, 27% and 19.6% respectively, while the water use efficiency of the RWLFZ decreased by 59.6% and there was no significant difference in the net photosynthetic rate between them, which showed that annuals in the RWLFZ adopt the R adaptation strategy with fast-growing, short lifespan and quickly acquiring and investing resources by altering leaf morphology such as expanding leaf area. The Simpson dominance index of RWLFZ was significantly higher than that of NRZ. Thus counter-seasonally hydrological alterations had the significant effects on functional traits of dominant species in the RWFLZ. Moreover, the highly adaptable and widely distributed species with larger niche breadths and high important values usually had a higher niche overlap value in the RWLFZ than in the NRZ, which showed that the competition in the plant community after experiencing anti-seasonal flooding was much more intraspecific than interspecific and would facilitate the expansion of species niches. And the distribution of the plant community was mainly driven by elevation (flooding depth), flooding duration and TK in the WLFZs. Our findings imply that the species with large niche breadths and high important values should be prioritized in ecological restoration efforts in the newly formed hydro-fluctuation zone of the TGR.