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Dams worldwide have significantly altered the composition of riparian forests. However, research on the functional traits of dominant herbs experiencing flooding stress due to dam impoundment remains limited. Given the high plasticity of leaf traits and their susceptibility to environmental influences, this study focuses on riparian herbs along the Three Gorges Hydro‐Fluctuation Zone (TGHFZ). Specifically, it investigates how six leaf physiological traits of leading herbs—carbon, nitrogen, phosphorus, and their stoichiometric ratios—adapt to periodic flooding in the TGHFZ using cluster analysis, one‐way analysis of variance (ANOVA), multiple comparisons, Pearson correlation analysis, and principal component analysis (PCA). We categorized 25 dominant herb species into three plant functional types (PFTs), noting that species from the same family tended to fall into the same PFT. Notably, leaf carbon content (LCC) exhibited no significant differences across various PFTs or altitudes. Within riparian forests, different PFTs employ distinct adaptation strategies: PFT‐I herbs invest in structural components to enhance stress resistance; PFT‐II, mostly comprising gramineous plants, responds to prolonged flooding by rapid growth above the water; and PFT‐III, encompassing nearly all Compositae and annual plants, responds to prolonged flooding with vigorous rhizome growth and seed production. Soil water content (SWC) emerges as the primary environmental factor influencing dominant herb growth in the TGHFZ. By studying the response of leaf physiological traits in dominant plants to artificial flooding, we intend to reveal the survival mechanisms of plants under adverse conditions and lay the foundation for vegetation restoration in the TGHFZ. [ABSTRACT FROM AUTHOR]

Abstract Dams worldwide have significantly altered the composition of riparian forests. However, research on the functional traits of dominant herbs experiencing flooding stress due to dam impoundment remains limited. Given the high plasticity of leaf traits and their susceptibility to environmental influences, this study focuses on riparian herbs along the Three Gorges Hydro‐Fluctuation Zone (TGHFZ). Specifically, it investigates how six leaf physiological traits of leading herbs—carbon, nitrogen, phosphorus, and their stoichiometric ratios—adapt to periodic flooding in the TGHFZ using cluster analysis, one‐way analysis of variance (ANOVA), multiple comparisons, Pearson correlation analysis, and principal component analysis (PCA). We categorized 25 dominant herb species into three plant functional types (PFTs), noting that species from the same family tended to fall into the same PFT. Notably, leaf carbon content (LCC) exhibited no significant differences across various PFTs or altitudes. Within riparian forests, different PFTs employ distinct adaptation strategies: PFT‐I herbs invest in structural components to enhance stress resistance; PFT‐II, mostly comprising gramineous plants, responds to prolonged flooding by rapid growth above the water; and PFT‐III, encompassing nearly all Compositae and annual plants, responds to prolonged flooding with vigorous rhizome growth and seed production. Soil water content (SWC) emerges as the primary environmental factor influencing dominant herb growth in the TGHFZ. By studying the response of leaf physiological traits in dominant plants to artificial flooding, we intend to reveal the survival mechanisms of plants under adverse conditions and lay the foundation for vegetation restoration in the TGHFZ.

As a type of wetland ecosystem with off-season 30 m water level fluctuation, the huge changes in the ecological environment, plant species, and vegetation dynamics in the hydro-fluctuation zone of the Three Gorges Reservoir (TGR) area have attracted a wide range of attention. In this present study, six typical locations in the water level fluctuating zone were used as the research objects, and the effects of different water surface elevations on the stoichiometric characteristics and homeostasis of leaf nitrogen and phosphorus were studied through a sample survey method. Results revealed that leaf nitrogen content was linearly correlated with leaf phosphorus content along water surface elevation. And water surface elevation significantly affected the nitrogen and phosphorus content of dominant plants. Four dominant species [Cynodon dactylon (Linn.) Pers, Xanthium sibiricum Partin ex Wider, Abutilon theophrasti Medik, and Bidens pilosa Linn] exhibited specific differences in the phosphorus steady state index (Hp) and nitrogen steady state index (HN). Although belonging to different categories, both HP and HN of four dominant species were in the same order: X. sibiricum > A. theophrasti > C. dactylon > B. Pilosa. The interspecific differences in HN and HP indicated that there were differences in the characteristics of nutrient utilization of dominant species and their adaption to water surface elevation. Furthermore, as the elevation increases, the community coverage increased and the community stability index also increased. This might indicate that in the fluctuating zone habitat, the plant's nitrogen and phosphorus utilization strategy affects the distribution and composition of plant community along water surface elevation, and ultimately affects the stoichiometric homeostasis on the community levels. [ABSTRACT FROM AUTHOR]

Natural ecosystems generally include litter decomposition as part of the natural cycle since the material properties and the environment greatly influence the decomposition rate. The invasion of exotic plants alters the species diversity and growth characteristics of plant communities, but its impact on litter decomposition is unknown in the riparian zone. This study examines how invasive plants affect the early stages of litter decomposition and how species richness impacts them. This experiment involved a random litter mixture of exotic (Alternanthera philoxeroides and Bidens pilosa) and native species in the riparian zone of the Three Gorges Dam Reservoir in China. There were 43 species mixture types, with various species richness ranging from 1 to 6. Litterbags were placed in the hydro-fluctuation zone and terrestrial zone, where they decomposed over the course of 55 days. Invasive plants decompose rapidly compared to native plants (35.71% of the remaining mass of the invasive plant). The invasive plant A. philoxeroides has the potential to accelerate native plant decomposition (0.29 of non-added synergetic effect), but Bidens pilosa cannot. Nonetheless, species richness had little effect on the decomposition rate. These effects are dependent upon differences in chemical functional characteristics among the species. The initial traits of the plants, specifically C, N, and C/N, were significantly and linearly correlated with the loss of mixed litter mass and mixing effect strength (P < 0.01). In addition, submergence decomposition conditions reduce the disturbance of invasive plants and predict decomposition rates based on litter characteristics. Invasive plants can therefore impact the material cycle of an ecosystem. There is a need to examine decomposition time, which may also involve considering other factors. [ABSTRACT FROM AUTHOR]

Hydrological fluctuations accelerate biodiversity loss and damage riparian ecosystems surrounding dams and reservoirs. Restoration of vegetation is urgently required in such highly impacted buffer zones. However, it is not known how the nonstructural carbohydrate (NSC) and organic acid concentrations of prominent woody plants such as Salix matsudana would alter under the hydrological regime described in the literature. The study aims to investigate the tap and lateral roots of S. matsudana in the Three Gorges Reservoir, as well as the NSC and organic acid metabolism of these roots. Three groups of two-year-old S. matsudana saplings were planted in this experiment: control (SS), moderate submergence (MS), and deep submergence (DS) at altitudes of 175 m, 170 m, and 165 m, respectively. The results indicated that hydrological regimes restrained the height of S. matsudana with less impact on diameter at P tartaric acid > oxalic acid. The tartaric acid content of the lateral roots and the total roots was significantly higher in MS than in SS1. Conversely, the oxalic acid and malic acid levels in tap roots, lateral roots, and total roots were higher in DS than in SS2. There were strong Pearson's correlations between root starch and NSC with tartaric and malic acids; these correlations ranged from −0.898

Riparian plants are an integral part of the river ecosystem and have significant impacts on the water quality of the reservoir area. The special hydrological process of the riparian zone makes it possible to become a “source” or “sink” of organic matter and nutrients. This study quantifies the flooding period on the decomposition as well as nutrient dynamics of leaves from artificially regenerated Taxodium ascendens in the riparian zone of the Three Gorges Reservoir (TGR) in China. Five decomposition treatment groups were exposed to 10, 30, 60, 90, and 180 days of decomposition: conventional water (T1), mild drought stress (T2), saturated water content (T3), light flooding stress (T4), and severe flooding stress (T5). In T4 and T5, the decomposition rate of T. ascendens leaves was significantly higher than that of T1, T2, and T3. All the leaf C, N, P, and K concentrations at the end of the test were lower than their respective starting values. The concentrations of N and P in the overlying water decrease to various degrees due to decomposition. At the end of the study, the TN content was 1.34 times (T4) and 1.16 times (T5) higher than that of the control group, and the TP content was 3.97 times (T4) and 3.21 times (T5) higher than that of the control group. Leaf decomposition increases the content of N and P in the overlying water under flood conditions, which adversely affects the water environment. This study establishes a theoretical framework for understanding how hydrological processes affect leaf decomposition and nutrient release in riparian areas, providing a scientific basis for riparian zone management in TGR.

Through the Betula nigra afforestation test in the engineering treatment area of the Wuxi Section of the Daning River in Chongqing, the feasibility of arbor vegetation restoration in the comprehensive management of the engineering treatment areas of the Three Gorges Reservoir was explored. The results showed that; (J) before the flooding in the project area, the survival rate of B. nigra seedlings was high, over 95%, and (2) in 2021, after a water storage period, affected by factors such as seedling specifications, flood and flooding time, the survival rate of the seedlings planted in 2020 was low, and the one-year-old seedlings were greatly competed by weeds and grew less. Two-year-old B. nigra seedlings were replanted in 2021, and the survival rate of the B. nigra seedlings was 100% in 2022. Two-year-old B. nigra seedlings have strong adaptability and have little impact on the stability of the engineering treatment area, and can be used as afforestation tree species in engineering treatment areas of hydro-fluctuation zones. [ABSTRACT FROM AUTHOR]

Ecological stoichiometric studies can be useful for managing the deteriorated riparian zones of mega-reservoirs in which nutrients significantly impact the balanced vegetation cover. The present study aims to explore the effects of periodic submergence on the stoichiometric ecological characteristics of carbon (C), nitrogen (N), and phosphorus (P), as well as the growth conditions of two leading conifer species (Taxodium distichum and Taxodium ascendens) in the hydro-fluctuation zone of the Three Gorges Reservoir (TGR) region, China. The stoichiometrical contents of C, N, and P in fine roots, leaves, and branches, and the growth conditions of T. distichum and T. ascendens were measured in July 2019. The results showed that periodic submergence affected the stoichiometric characteristics and growth conditions of these two woody species, and the impact was restrained, but both grew well. The effects of inundation on the C, N, and P ecological stoichiometric characteristics differed in different parts of trees. In general, the C contents showed the following pattern: leaves > branches > fine roots. The N and P content showed the following pattern: leaves > fine roots > branches, while the C/N and C/P ratios showed an opposite trend to that of N and P. The N and P content in all parts of T. distichum (with means of 17.18 and 1.70 g/kg for leaves, 4.80 and 0.57 g/kg for branches, and 6.88 and 1.10 g/kg for fine roots, respectively) and T. ascendens (with means of 14.56 and 1.87 g/kg for leaves, 5.03 and 0.63 g/kg for branches, and 8.17 and 1.66 g/kg for fine roots, respectively) were higher than the national average level (with means of 14.14 and 1.11 g/kg for leaves, 3.04 and 0.31 g/kg for branches, and 4.85 and 0.47 g/kg for fine roots, respectively). Except for N and P contents in the leaves of T. distichum, there was a significant correlation between N and P elements in other parts (p < 0.05). Nevertheless, the N/P ratio (10.15, 8.52, 6.44, and 7.93, 8.12, 5.20 in leaves, branches, and fine roots of T. distichum and T. ascendens, respectively) was lower than the critical ratio of 14. The growth conditions of T. distichum and T. ascendens were significantly negatively correlated with their leaf C contents and significantly positively correlated with their fine root N and P contents. This study showed that T. distichum and T. ascendens could maintain their normal growth needs by properly allocating nutrients between different organs to adapt to the long periodic submergence in the hydro-fluctuation zone of the TGR region.

As one of the most active components in soil, bacteria can affect soil physicochemical properties, its biological characteristics, and even its quality and health. We characterized dynamics of the soil bacterial diversity in planted (with Taxodium distichum) and unplanted soil in the riparian zone of the Three Gorges Dam Reservoir (TGDR), in southwestern China, in order to accurately quantify the changes in long-term soil bacterial community structure after revegetation. Measurements were taken annually in situ in the TGDR over the course of 5 years, from 2012 to 2016. Soil chemical properties and bacterial diversity were analyzed in both the planted and unplanted soil. After revegetation, the soil chemical properties in planted soil were significantly different than in unplanted soil. The effects of treatment, time, and the interaction of both time and treatment had significant impacts on most diversity indices. Specifically, the bacterial community diversity indices in planted soil were significantly higher and more stable than that in unplanted soil. The correlation analyses indicated that the diversity indices correlated with the pH value, organic matter, and soil available nutrients. After revegetation in the riparian zone of the TGDR, the soil quality and health is closely related to the observed bacterial diversity, and a higher bacterial diversity avails the maintenance of soil functionality. Thus, more reforestation should be carried out in the riparian zone of the TGDR, so as to effectively mitigate the negative ecological impacts of the dam. Vegetating the reservoir banks with Taxodium distichum proved successful, but planting mixed stands of native tree species could promote even higher riparian soil biodiversity and improved levels of ecosystem functioning within the TGDR. [ABSTRACT FROM AUTHOR]

In order to understand the effect of submergence on nutrient release of the reforested tree leaves and assess the environmental risk of leaf decomposition under submergence, the mass loss and nutrient release rates of three reforestation tree species, Taxodium ascendens Brongn, Taxodium distichum (L.) Rich., and Salix matsudana Koidz., at different elevation in the hydro-fluctuation zone of the Three Gorges Dam Reservoir (TGDR) region were tested in situ. Results showed that the initial macroelement contents of the leaves of the three tree species varied among different elevations due to different submergence stresses. All foliar mass loss rates of the three tree species at 165 m a.s.l. were significantly higher than that at 175 m a.s.l. (except that of S. matsudana at 165 m a.s.l.), after 179 days of incubation commenced September 20. After 138 days of incubation commenced October 5, the foliar mass loss rates of the three tree species at 170 m a.s.l. were significantly higher than that at 175 m a.s.l. Moreover, the leaf mass loss rates of S. matsudana were higher than the other two species when compared at the same elevation of the same incubation period. In addition, foliar release rates of N and Ca in T. ascendens, C, N, and Ca in T. distichum as well as Ca in S. matsudana at 165 m a.s.l. after 179 days of incubation and at 170 m a.s.l. after 138 days of incubation were significantly higher than that at 175 m a.s.l., respectively. Leaf mass loss rates of T. ascendens were significantly correlated with its initial leaf K, Ca, and Mg contents. In contrast, leaf mass loss rates of T. distichum had significant correlations with the initial leaf P and K contents, as well as C/P and N/P ratios. However, the mass loss rates of S. matsudana significantly correlated with initial leaf N, P, and Ca contents and C/N, C/P, and N/P ratios. Foliar nutrient release rates, especially the foliar release of C, N, and P of the three tree species, had significant correlations with initial leaf C/P and N/P ratios. Our results suggested that submergence facilitated the decomposition and nutrient release rates of the leaves of the three woody species, especially the broad leaves of S. matsudana, which may potentially cause secondary pollution to the water body of the TGDR. Thus, we suggested that a sustainable harvest of leaves of the reforested forest stands prior to submergence should be considered in the hydro-fluctuation zone so as to protect the water quality of the TGDR. [ABSTRACT FROM AUTHOR]

Submergence-tolerant trees are essential for vegetation restoration of the hydro-fluctuation zone of the Three Gorges Dam Reservoir (TGDR) area. Thus, it is of great significance to select the submergence-tolerant plant species by conducting in situ studies. To restore degraded riparian vegetation under the circumstances of dynamic impoundment of the TGDR, Salix matsudana Koidz., a flooding-tolerant native tree species, was introduced to conduct an in situ practical study to test its performance in re-vegetating and restoring the hydro-fluctuation zone of the TGDR. Effects of periodic moderate submergence (MS) and deep submergence (DS) on photosynthesis and growth of Salix matsudana Koidz. were investigated after three water cycles compared to a control (i.e., shallow submergence, abbreviated as SS) in order to specifically assess its application prospects in vegetation restoration under such extreme environment. Results showed that net photosynthetic rate (Pn), intrinsic water use efficiency (WUEi) and limiting value of stomata (Ls) of S. matsudana were significantly reduced in DS. However, pigment content had no significant change in all submergence treatments. Diameter at breast height (DBH) and tree height of S. matsudana were significantly decreased in both MS and DS when compared to that of SS, respectively. In contrast, the primary branch number of S. matsudana was significantly increased as submergence increased. In addition, relative diameter and height growth rates of S. matsudana were also reduced under submergence. Considering the sustained growth of this species, S. matsudana saplings are tolerant to long-term periodic submergence and can be applied to the vegetative restoration of the hydro-fluctuation zone of the TGDR region. [ABSTRACT FROM AUTHOR]

• Hydrological regimes restrained the height of Salix matsudana with less impact on diameter. • Root starch concentrations were higher than those of soluble sugars after hydrological stress. • In this study, the order of the acids was malic acid > tartaric acid > oxalic acid. • Strong Pearson's correlations were found between root starch and nonstructural carbohydrates with tartaric and malic acids. • Salix matsudana can maintain certain levels of starch, malic acid, and tartaric acid under in-situ flooding stress. Hydrological fluctuations accelerate biodiversity loss and damage riparian ecosystems surrounding dams and reservoirs. Restoration of vegetation is urgently required in such highly impacted buffer zones. However, it is not known how the nonstructural carbohydrate (NSC) and organic acid concentrations of prominent woody plants such as Salix matsudana would alter under the hydrological regime described in the literature. The study aims to investigate the tap and lateral roots of S. matsudana in the Three Gorges Reservoir, as well as the NSC and organic acid metabolism of these roots. Three groups of two-year-old S. matsudana saplings were planted in this experiment: control (SS), moderate submergence (MS), and deep submergence (DS) at altitudes of 175 m, 170 m, and 165 m, respectively. The results indicated that hydrological regimes restrained the height of S. matsudana with less impact on diameter at P < 0.05 compared with SS but showed a 100 % survival rate throughout the experiment. Meanwhile, root starch concentrations of 108.46 ± 9.18 mg/g (mean ± standard error) were higher than those of soluble sugars (86.81 ± 12.98 mg/g) after hydrological stress. Moreover, the levels of soluble sugar, starch, and NSC in MS were higher than those of SS1 (1st phase of control). However, soluble sugar, starch, and NSC content in DS were lower than in SS2 (2nd phase of control), where lateral root starch and NSC content were more significant than those in the taproot. After 205 days of submersion (DS), oxalic acid, tartaric acid, and malic acid content were higher than after 135 days (MS). They followed the pattern of malic acid > tartaric acid > oxalic acid. The tartaric acid content of the lateral roots and the total roots was significantly higher in MS than in SS1. Conversely, the oxalic acid and malic acid levels in tap roots, lateral roots, and total roots were higher in DS than in SS2. There were strong Pearson's correlations between root starch and NSC with tartaric and malic acids; these correlations ranged from −0.898 < r < 0.981. These data indicate that S. matsudana can maintain certain levels of starch, malic acid, and tartaric acid to enable it to better adapt to its environment under in-situ flooding stress. [ABSTRACT FROM AUTHOR]

Natural ecosystems generally include litter decomposition as part of the natural cycle since the material properties and the environment greatly influence the decomposition rate. The invasion of exotic plants alters the species diversity and growth characteristics of plant communities, but its impact on litter decomposition is unknown in the riparian zone. This study examines how invasive plants affect the early stages of litter decomposition and how species richness impacts them. This experiment involved a random litter mixture of exotic ( Alternanthera philoxeroides and Bidens pilosa ) and native species in the riparian zone of the Three Gorges Dam Reservoir in China. There were 43 species mixture types, with various species richness ranging from 1 to 6. Litterbags were placed in the hydro-fluctuation zone and terrestrial zone, where they decomposed over the course of 55 days. Invasive plants decompose rapidly compared to native plants (35.71% of the remaining mass of the invasive plant). The invasive plant A. philoxeroides has the potential to accelerate native plant decomposition (0.29 of non-added synergetic effect), but Bidens pilosa cannot. Nonetheless, species richness had little effect on the decomposition rate. These effects are dependent upon differences in chemical functional characteristics among the species. The initial traits of the plants, specifically C, N, and C/N, were significantly and linearly correlated with the loss of mixed litter mass and mixing effect strength ( P < 0.01). In addition, submergence decomposition conditions reduce the disturbance of invasive plants and predict decomposition rates based on litter characteristics. Invasive plants can therefore impact the material cycle of an ecosystem. There is a need to examine decomposition time, which may also involve considering other factors., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Hu, Arif, Ding, Li, He and Li.)

Ecological stoichiometric studies can be useful for managing the deteriorated riparian zones of mega-reservoirs in which nutrients significantly impact the balanced vegetation cover. The present study aims to explore the effects of periodic submergence on the stoichiometric ecological characteristics of carbon (C), nitrogen (N), and phosphorus (P), as well as the growth conditions of two leading conifer species (Taxodium distichum and Taxodium ascendens) in the hydro-fluctuation zone of the Three Gorges Reservoir (TGR) region, China. The stoichiometrical contents of C, N, and P in fine roots, leaves, and branches, and the growth conditions of T. distichum and T. ascendens were measured in July 2019. The results showed that periodic submergence affected the stoichiometric characteristics and growth conditions of these two woody species, and the impact was restrained, but both grew well. The effects of inundation on the C, N, and P ecological stoichiometric characteristics differed in different parts of trees. In general, the C contents showed the following pattern: leaves > branches > fine roots. The N and P content showed the following pattern: leaves > fine roots > branches, while the C/N and C/P ratios showed an opposite trend to that of N and P. The N and P content in all parts of T. distichum (with means of 17.18 and 1.70 g/kg for leaves, 4.80 and 0.57 g/kg for branches, and 6.88 and 1.10 g/kg for fine roots, respectively) and T. ascendens (with means of 14.56 and 1.87 g/kg for leaves, 5.03 and 0.63 g/kg for branches, and 8.17 and 1.66 g/kg for fine roots, respectively) were higher than the national average level (with means of 14.14 and 1.11 g/kg for leaves, 3.04 and 0.31 g/kg for branches, and 4.85 and 0.47 g/kg for fine roots, respectively). Except for N and P contents in the leaves of T. distichum, there was a significant correlation between N and P elements in other parts (p < 0.05). Nevertheless, the N/P ratio (10.15, 8.52, 6.44, and 7.93, 8.12, 5.20 in leaves, branches, and fine roots of T. distichum and T. ascendens, respectively) was lower than the critical ratio of 14. The growth conditions of T. distichum and T. ascendens were significantly negatively correlated with their leaf C contents and significantly positively correlated with their fine root N and P contents. This study showed that T. distichum and T. ascendens could maintain their normal growth needs by properly allocating nutrients between different organs to adapt to the long periodic submergence in the hydro-fluctuation zone of the TGR region. [ABSTRACT FROM AUTHOR]

Organic acids are critical as secondary metabolites for plant adaption in a stressful situation. Oxalic acid, tartaric acid, and malic acid can improve plant tolerance under waterlogged conditions. Two prominent woody species (Taxodium distichum-Swamp cypress and Salix matsudana-Chinese willow) have been experiencing long-term winter submergence and summer drought in the Three Gorges Reservoir. The objectives of the present study were to explore the responses of the roots of two woody species during flooding as reflected by root tissue concentrations of organic acids. Potted sample plants were randomly divided into three treatment groups: control, moderate submergence, and deep submergence. The concentrations of oxalic acid, tartaric acid, and malic acid in the main root and lateral roots of the two species were determined at four stages. The results showed that T. distichum and S. matsudana adapted well to the water regimes of the reservoir, with a survival rate of 100% during the experiment period. After experiencing a cycle of submergence and emergence, the height and base diameter of the two species showed increasing trends. Changes in base diameter showed insignificant differences between submergence treatments, and only height was significant under deep submergence. The concentrations of three organic acids in the roots of two species were influenced by winter submergence. After emergence in spring, two species could adjust their organic acid metabolisms to the normal level. Among three organic acids, tartaric acid showed the most sensitive response to water submergence, which deserved more studies in the future. The exotic species, T. distichum, had a more stable metabolism of organic acids to winter flooding. However, the native species, S. matsudana, responded more actively to long-term winter flooding. Both species can be considered in vegetation restoration, but it needs more observations for planting around 165 m above sea level, where winter submergence is more than 200 days. [ABSTRACT FROM AUTHOR]