Riparian Plant Research Articles

The response of plant diversity to human dominance in the meta-watershed ecosystem of Southwest China

• Intensified urban development threatened forest and riparian plant diversity. • Socioeconomic and water conservancy development deteriorated plant diversity. • Riparian plants were more susceptible to artificial development than forest plants. • Human dominance destroys ecosystem services provision in meta-watershed ecosystems. Plant diversity is essential to maintain terrestrial ecosystem stability and balance, but it is highly susceptible to environmental changes that are generally dominated by human activities. In the natural habitat, plant growth and distribution patterns are known to be regulated by abiotic environments such as water, temperature, and nutrient. However, how growing human dominance impacts plant diversity at the watershed scale remains unclear. From the view of the meta-watershed ecosystem, this study constructed indicators to examine the plant diversity responses in karst watersheds of different urban development intensities. The results revealed that the growing urban development intensity deteriorated plant diversity and riparian plant diversity in the meta-watershed ecosystem. Both socioeconomic and water conservancy development had noticeable adverse effects on plant diversity. The riparian plants were more susceptible to artificial development than forest plants. The predicted results of various development scenarios suggest that, by the middle of the 21st century, plant diversity and food production in the watershed will meet a crisis unless forest protection policies are applied, and large-scale urban expansion is curbed. In the meta-watershed ecosystem, growing human dominance increasingly destroys plant diversity and the ecosystem supply. Policies and measures are urgently needed to reverse the potential deteriorating trend of the ecosystem, maintain the stability of the ecosystem, and promote the sustainable development of human society.

Warming water and leaf litter quality but not plant origin drive decomposition and fungal diversity in an experiment.

The fungi associated with leaf litter play a key role in decomposition and can be affected both by the warming water and the invasion of non-native species in riparian vegetation. Warming water and invasion of non-native riparian species on stream fungal communities have been studied mainly in temperate ecosystems. We tested the effects of warming water and non-native plant Psidium guajava on leaf litter decomposition, conidia density, species richness and beta diversity of tropical stream fungi. Thus, we carried out an experiment using the current mean temperature of streams from northwestern Paraná in South Brazil (22°C) and two temperatures above the current mean temperature (26°C and 29°C). We also used the leaves of a non-native plant (P.guajava), and two native plants (one of similar nutritional quality, and the other of higher nutritional quality than the non-native species) occurring in Neotropical streams riparian vegetation. Warming water accelerated leaf litter decomposition and reduced conidia density and fungal richness in native and non-native plants. However, species composition and beta diversity were not affected by water temperature. Our study showed that warming affects the fungi of streams, the main microorganisms responsible for decomposition and that the nutritional quality of the leaves may be more important than the origin of riparian plant species. Despite this, further investigations should be conducted on the interaction of P.guajava with the flow of nutrients in these environments and how it can affect other ecosystem processes and the food chain. Efforts to study the effects of water warming and biological invasion on the attributes and distribution of fungi in streams are vital, making them a tool for the conservation of riparian ecosystems.

Флора водоемов и водотоков Саратовской области: история изучения и современное состояние

Water plants and coastal riparian plants are an integral part of the habitat forming component of water ecosystems in Saratov region. This article gives a review of long-term research of flora in many water reservoirs and water streams of the Saratov region. The analysis of literature in its historical aspect showed that the degree of scientific knowledge about water flora in the Saratov region is still insufficient despite multiple research projects conducted at the end of the 20th and beginning of the 21st centuries. At the moment some research is being conducted concerning the inventory and monitoring of flora and plants in the water reservoirs and water streams of the Saratov region. In this work a complete list of water plants and coastal riparian plants is represented. The flora of water vascular plants contains 103 types (including hybrids) of 54 species, 32 plant families and 3 plant divisions. The leading plant families are Potamogetonaceae, Cyperaceae, Typhaceae and Poaceae. The most widespread species are Potamogeton represented by 18 types and 3 hybrids (13 % of all flora). Multi-species are Typha, Carex, Scirpus and Lemna. To identify the proportion of water species in flora of water streams and water reservoirs, the hydrofitness index IHg was used. It showed that the most diverse water flora exist in the Volgograd water reservoir and lakes. In ponds and oxbow lakes coastal plants play an essential role which can be explained by fluctuations in the levels of these water bodies. In water reservoirs and streams of the Saratov region the most highly active ones are Phragmites australis Potamogeton pectinatus, Typha angustifolia, Nuphar lutea, Sparganium erectum. The percentage of active types makes up only 5 % of all water flora. Among registered vascular plants 30 types are included in the Red Book of endangered species of the Saratov region. In the researched flora 9 invasive species were detected, such as Bidens frondosa, Elodea canadensis, Zizania latifolia, Typha laxmannii, Acorus calamus, Hydrilla verticillata, Vallisneria spiralis, Lemna gibba, Lemna minuta.

Revisiting irrigation efficiency before restoring ancient irrigation canals in multi-functional, nature-based water systems

CONTEXTIn the Middle Ages, the Muslims introduced communal water management in the Iberian Peninsula. Some irrigation systems of medieval origin are still in operation in the mountainous areas of Southern Spain. Snowmelt runoff is diverted during spring from high-altitude streams into contoured recharge ditches that convey the water to areas of high infiltration (shallow aquifers). This regulates and delays discharge into the main river, from which downstream flow is diverted, during late spring and summer, to irrigation ditches that supply terraces and fields on river plains. The Busquístar irrigation ditch and its irrigation scheme comprise one of these ancient systems. OBJECTIVES1) To characterize the Busquístar system, its water source and regulation, its water users' association, its multi-functionality, and its quality as a nature-based solution for water security. 2) To review the irrigation efficiency concept applied to the restoration of ancient irrigation systems, taking into account their ecosystem services. METHODSi) Semi-structured interviews with stakeholders to evaluate irrigation system operation and perceptions of multi-functionality; ii) field surveys for description of the irrigation ditch and its riparian flora; iii) satellite imagery for quantifying riparian vegetation; iv) water balance for irrigation efficiency computation. RESULTS AND CONCLUSIONSCrop production is the main function of the Busquístar irrigation scheme but additional ecosystem services are creation of landscape and biodiversity. Eight riparian plant communities were distinguished along the irrigation ditch. The discharge measured at its head on 23 July and 3 September 2017 represented 14 and 50% of the mean river flow in July and September, respectively. The flow measured at the first bifurcation of the ditch was about half that at the head, revealing the proportion filtered along its 6470-m long conveyance reach. The remaining flow was then diverted to 4 branches along the 3140-m long distribution reach proportionally to the irrigable area in each branch. Return flows and irrigation efficiency were estimated for the two measuring dates considering riparian and crop evapotranspiration. The estimated efficiency was highly dependent on which water uses were considered beneficial and on the scale of analysis, field, entire system or watershed. SIGNIFICANCEThe study revealed the integrated approach behind the traditional water management in these ancient systems. The article proposes a review of the irrigation efficiency concept that allows reconciling the character of a nature-based solution with the current restoration of the system, responding to the needs of the emerging export horticulture in the area.

Effects of hydrological regime on Taxodium ascendens plant decomposition and nutrient dynamics in the Three Gorges Reservoir riparian zone

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.

Modelling LEAF stomatal resistance for common REED, peach‐leaf willow and cottonwood riparian plant communities

AbstractAccounting for the impact of riparian plant communities on water balances is usually ignored due to the lack of data and information on water use of these plant communities. This is especially important for areas with limited water resources and in areas where water resources are shared between different users (agriculture, riparian zones, other ecosystems/agro‐ecosystems, municipalities, recreational, mining, agro‐ecology, etc.). Modelling stomatal resistance (rL) of riparian vegetation species is a complex process, but is also one of the limited processes to estimate evaporative losses for these plant communities for more inclusive, complete and robust water balance and hydrologic analyses for forecasting, planning, allocating and managing surface and groundwater resources and for hydrologic modelling. The objectives of this research were to (i) modify Jarvis‐type model for estimating rL for three riparian plant species [Common reed (Phragmites australis), Peach‐leaf willow (Salix amygdaloides) and Cottonwood (Populus sect. Aigeiros)], (ii) investigate the rL response to microclimate/environmental variables, and (iii) evaluate the photosynthetic photon flux density (PPFD) versus rL response curves for estimating hourly rL. A Jarvis‐type model was modified by re‐parametrization using porometer‐measured data collected via extensive field campaigns in 2009 and 2010. Flooding in 2010 impacted the phenology and physiology of all species with increased rL and impedance in growth due to oxygen stress. While R2 values were generally low for both years for all species, the response of rL to the same climate variables under the same environmental conditions exhibited substantial variations between the species. Overall, the response of rL to climatic variables was species‐specific, complex and varied with surface and atmospheric conditions. For all species, stronger relationships between rL versus air temperature and net shortwave radiation were observed. The Jarvis‐type model underestimated rL for all species and hence required independent re‐parameterization for each specie independently. The model performance after re‐parameterization improved substantially during both calibration and validation. Validation of the new modified Jarvis‐type model (NMJ‐model) resulted in good estimates of rL with root‐mean‐squared difference (RMSD) and R2 values of 31 s m−1 and 0.51 for Common reed; 56 s m−1 and 0.81 for Peach‐leaf willow; and 237 s m−1 and 0.51 for Cottonwood, respectively. Strong agreements were found between measured and re‐parameterized NMJ‐model‐estimated rL values for all three species in both years, but the relationships improved significantly in 2009 with no flooding. The NMJ‐model‐estimated rL values were within 10, 7 and 11% of the measured values for Common reed, Peach‐leaf willow and Cottonwood, respectively. rL values estimated using PPFD versus rL response curves developed for individual species were used to estimate hourly rL and the response curves were able to effectively track the trends and magnitudes of rL. With re‐parameterization, the NMJ‐models developed and tested for each riparian vegetation specie provide robust estimates of rL that can be used to quantify evaporative losses of these riparian plant communities for more complete local and regional water balance analyses by accounting for riparian vegetation water use.

The responses of riparian plant communities to environmental and spatial factors in the upper Han River basin, China

Exploring the relative roles of environmental and spatial factors in shaping community composition is crucial to gain insights into community assembly. At present, however, their roles in riparian plant communities remain to be fully elucidated. Here, we investigated the responses of taxonomic and functional trait compositions of riparian plant communities to environmental and spatial factors in the upper Han River basin, China. We aimed to (1) investigate the responses of both taxonomic composition and functional traits to anthropogenic disturbances and (2) compare the relative roles of environmental and spatial factors in affecting both taxonomic and functional trait compositions. Results showed that species diversity of riparian plant communities was highest under mild disturbance, and both types of riparian plant community composition were strongly influenced by anthropogenic activities. In addition, the riparian plant community compositions in the upper Han River basin were driven by both environmental and spatial factors. Compared to spatial factors, environmental filtering was more important in explaining species composition, while the opposite trend was observed for functional composition due to the high environmental heterogeneity of the 5 tributaries and the reproductive mode from riparian plants. Thus, for assessment and management of riparian vegetation, the taxonomic and functional characteristics of communities should be considered as they may respond to important drivers and anthropogenic disturbances differently.

Rhizosphere Soil Microbial Survival States and N-Related Process during Riparian Plant Dormancy: Influences of Plant Locations and Plant Species

The plant dormancy period in the riparian zone affects the activity of microorganisms and their related nitrogen (N) process, which necessitates an investigation of the influence of the dormancy period on the microbial community. This study sampled two groups of soils (ashore and offshore soils) of two typical plants (Acorus calamus, Canna indica) in rhizosphere soils and bulk soils during the dormancy period to study the microbial communities. The results suggested that in ashore soils, especially in Canna indica soils, there was a lower abundance of N-related genes (4.79 × 106 copies/g) due to relatively competitive ecological niche competition because of possible sufficient substrate. Therefore, microbial communities still play a major role in the removal of N-related nutrients during plants’ dormancy period. In addition, the results also showed that during the plant dormancy period, the cell necrosis processes accounted for relatively lower proportions (15.75%, 7.54%, 21.46%, and 5.23% in ashore and offshore Canna indica and ashore and offshore Acorus calamus, respectively), suggesting an unexpected fairly strong microbial survival ability in the dormancy period compared to the commonly expected weak microbial state. This high microbial vitality provides us insight into the restoration of riparian soils during the plant dormancy period.

Transformation of nitrogen compounds in a regenerated urban drainage stream in New Zealand

ABSTRACT Haytons Stream, a low laying stormwater and groundwater-fed stream located in Christchurch, New Zealand, contains some of the highest levels of ammoniacal nitrogen and oxidised nitrogen in the country. To improve its water quality, the watercourse was reconditioned by adding retention ponds and riverbank riparian plants. The objective of this study was to assess the spatial and temporal changes in nitrogen species and concentration along the restored Haytons Stream to gain insight into the drivers of nitrogen compound transformation in urban streams. Water samples were collected from eight sampling stations along the stream in baseflow and stormflow conditions during dry and wet seasons. Results show that under baseflow, inorganic nitrogen was mostly present while under stormflow it was mainly in organic form. Overall, nitrogen concentrations increased from the upper to middle stream sections, decreasing downstream where the watercourse had been restored. The restoration of the stream was found to reduce all forms of nitrogen, except particulate organic nitrogen (PON, i.e. algae). The pond at the outlet of Haytons Stream contribute to converting dissolved inorganic nitrogen to predominantly PON, which should be removed through separation mechanisms in order to prevent PON from entering the Heathcote/Opawaho River at the Hayton’s Stream discharge.

Development of Riparian Plant Diversity Enrichment Book for Biology Student in Kampar Regency

This study aims to develop an enrichment book for Riparian plant species diversity in Kampar Regency. This research was carried out with an ADDIE development model consisting of the Analysis, Design, Development, Implementation and Evaluation stages. limited to the Development stage, namely the Validity Test due to time constraints. The type of data used is quantitative and qualitative data, the data sources are primary data and secondary data. The parameter in this study is the validity which is measured by using a Validation Questionnaire. Subject Experts who are competent in their fields. The results of the Material Expert Validation of the content feasibility component and the presentation of the material obtained an average score of 5 with a very good category. Media Experts for the Language component and Graphic Component obtained an average score of 5 in the very good category, the Biology teacher for the presentation of material/content, the language component, and the graphic component received an average score of 5 in the very good category. The conclusion of the book on Enrichment of Riparian Plant Species in Kampar Regency is the Valid and Eligible Category for use in the next stage.

Nutrient Inputs Alleviate Negative Effects of Early and Subsequent Flooding on Growth of Polygonum hydropiper With the Aid of Adventitious Roots.

Riparian plants are exposed to harmful stress induced by flooding, which is often accompanied by eutrophication in the Three Gorges Reservoir Region. The phenomenon is mainly caused by domestic sewage discharges, slow water flow, and agricultural fertilizer pollution. Simulating abiotic stress, such as flooding at the initial period, can act as a signal and induce positive responses of plants to subsequent severe stress. In addition, eutrophication supplies nutrients, provides a favorable environment in the early stages of plant, and facilitates good performance in later development. However, whether early flooding (with or without eutrophication) acts as positive cue or as stress on plants at different developmental stages remains unclear. To address this question, seeds of Polygonum hydropiper were collected from low and high elevations in the hydro-fluctuation belt of the Three Gorges Reservoir Region. Plants germinated from these seeds were subjected to shallower and shorter early flooding treatments with or without eutrophication. Subsequently, plants were subjected to deeper and longer flooding treatments with or without eutrophication. Early flooding and eutrophic flooding significantly induced generation of adventitious roots, suggesting morphological adaptation to flooding. Although early flooding and eutrophic flooding treatments did not increase plant biomass in subsequent treatments compared with control, stem length, length and width of the 1st fully expanded leaf, and biomass of plants in the early eutrophic treatment were higher than these of the early flooding treatment plants. These results suggest a negative lag-effect of early flooding, and also indicate that nutrient inputs can alleviate such effects. Similarly, subsequent eutrophic flooding also enhanced plant growth compared with subsequent flooding, showing significantly higher values of leaf traits and adventitious root number. Plants originated from low elevation had significantly higher functional leaf length and stem biomass compared with those from high elevation. These results suggest that nutrient inputs can alleviate negative effects of early and subsequent flooding on growth of P. hydropiper with the generation of adventitious roots.

The status and role of genetic diversity of trees for the conservation and management of riparian ecosystems: A European experts' perspective

Abstract Riparian vegetation supports high biodiversity providing many services and is, therefore, an important landscape element. Riparian ecosystems are subject to numerous pressures leading to population decline and genetic erosion of riparian plants. This may have cascading effects at various ecosystem levels, including decreasing ecosystem services, so identifying the current status of genetic diversity of riparian tree species is vital to improve the effectiveness of restoration efforts. We aimed to elicit expert views on the status and importance of genetic diversity of tree species, and conservation needs across European riparian ecosystems. Sharing of such information among researchers, managers and policymakers has the potential to enhance ecological restoration and management of riparian ecosystems. We identified experts in riparian genetic resources conservation and management across Europe. These included stakeholders with different perspectives, ranging from researchers to practitioners. We designed a set of questionnaires where our identified experts were asked to answer questions related to the status and conservation of genetic diversity of riparian tree species in their respective countries. Specifically, we asked about societal awareness, legislative tools, good practices and conservation or restoration projects accounting for intraspecific genetic diversity and differentiation of tree species in riparian ecosystems. Questionnaire responses were analysed and discussed in light of the scientific literature to define needs and priorities related to the management and conservation of genetic diversity of riparian tree species. The experts recognized that a combination of in situ and ex situ measures and/or integrative conservation of riparian ecosystems is the most appropriate option for conserving the genetic diversity of riparian tree species. Simultaneous application of conservation measures at the level of priority species, identified by experts, and protection of riparian areas are required. Synthesis and applications. This study revealed the importance of recognizing the ecological processes that shape the genetic diversity of riparian tree species in hydrographic networks (dendritic spatial configuration, specific patterns of gene flow among riparian populations, fragmentation of river by dams) but also the need to overcome socio‐economic barriers, such as lack of policy priority, deficiency in funding and weak legislation framework.

Shift from soil chemical to physical filters in assembling riparian floristic communities along a flooding stress gradient

Understanding community assembly is a key issue in recognizing community succession and guiding the restoration of degraded ecosystems. Based on the stress-dominance hypothesis (SDH), along a gradient of increasing environmental stress, the relative importance of environmental filtering is supposed to be dominant but species interaction could be a minor process in assembling communities. However, this hypothesized model of the assembly-rule shift was equivocally supported by various studies. In this study, by examining riparian plant communities with the zonation distribution of species composition along a markedly contrast flooding-stress gradient, a general aim was to clarify whether assembly rules of the communities would be also sorted into the zonation pattern as expected by the SDH. Another aim was to identify how edaphic factors associate with the assembly processes. Firstly, we found that even under the distinct stress gradient, community assembly was not stratified into different rules as the SDH expected, but environmental filtering appeared as a dominant assembly process across the stress gradient. Secondly, although filtering holds as a dominant assembly rule, environmental filters were found different along the gradient. By disentangling the filters of edaphic attributes, we found that the filters significantly shifted from soil physical properties to chemical nutrients governing the filtering process along the gradient. This result revealed that, across the contrast gradient, the environmental deterministic process on assembly is so strong that the other assembly processes became weaker. By synthesizing our results, the SDH may not be applied even under the context of a contrast stress gradient, which suggests that environmental context may be a key in testing and applying the SDH. Finally, in guiding riparian restoration under strong stress, we suggest that soil physical structure rather than chemical nutrients shall be given a priority for consideration in rebuilding the degraded riparian communities.

Effect of Restoration on Plant Greenness and Water Use in Relation to Drought in the Riparian Corridor of the Colorado River Delta

ABSTRACTRevitalization of the Colorado River delta riparian corridor and increasing riparian plant greenness and water use may be accomplished by added water and restoration efforts to offset declines measured since 2000 by Landsat. We use the two‐band Enhanced Vegetation Index (EVI2; a proxy for greenness) and evapotranspiration (ET, mm/day) using EVI2 and potential ET(ETo) from Yuma Valley. We assess if restoration with only 7.5% landcover had an impact on the unrestored reach‐level landcover by measuring these two metrics, EVI2 and ET(EVI2) by comparing restored and unrestored areas. A key finding is that over 21‐years EVI2 in the unrestored corridor decreased by 23.6% and ET(EVI2) decreased by 32% (0.87 mm/day). Since 2011, the unrestored reaches lost EVI2 (11%) and −0.73 mm/day ET(EVI2) (28%), but restored sites increased in EVI2 (36%) and 0.58 mm/day ET(EVI2) (20%). Water delivered to restored sites increased EVI2 by 33.6% and 1.29 mm/day ET(EVI2) (58%). EVI2 and ET(EVI2) as a function of the Standardized Precipitation Evapotranspiration Index for drought periods highlight that restored and unrestored sites respond differently. Unrestored reaches are in decline; restored sites show increases in EVI2 and ET(EVI2). Restored sites do not have a significant impact on unrestored adjacent area, but smaller surface flows, a greater reliance on directed agricultural return flows, and deliveries of water to active restoration sites have revitalized habitat and increased ecosystem services in the delta.

Does large dam removal restore downstream riparian vegetation diversity? Testing predictions on the Elwha River, Washington, USA.

Large dams and their removal can profoundly affect riparian ecosystems by altering flow and sediment regimes, hydrochory, and landform dynamics, yet few studies have documented these effects on downstream plant communities. Ecological theory and empirical results suggest that by altering disturbance regimes, reducing hydrochory, and shifting communities to later successional stages, dams reduce downstream plant diversity. Dam removal could reverse these processes, but the release of large volumes of sediment could have unexpected, transient effects. Two large dams were removed on the Elwha River in Washington State, USA, from 2011 to 2014, representing an unprecedented opportunity to study large dam removal effects on riparian plant communities. Our research objectives were to determine: (1) whether the Elwha River dams were associated with lower downstream plant diversity and altered species composition across riparian landforms pre-dam removal, and (2) whether dam removal has begun to restore downstream diversity and composition. To address these objectives, we compared plant species richness and community composition in river segments above, below, and between the two dams. Plant communities were sampled twice before (2005 and 2010) and four times after (2013, 2014, 2016, and 2017) the start of dam removal, with 2013 and 2014 sampled while the upstream dam removal was ongoing. Prior to dam removal, native species richness was 41% lower below dams compared with the upstream segment; 6 years after dam removal began, it increased ~31% between the dams, whereas nonnative species richness and cover were not apparently affected by dams or their removal. Deposition caused by large volumes of released reservoir sediment had mixed effects on native species richness (increased on floodplains, decreased elsewhere) in the lowest river segment. Plant community composition was also different downstream from dams compared with the upstream reference, and has changed in downstream floodplains and bars since dam removal. In the long term, we expect that diversity will continue to increase in downstream river segments. Our results provide evidence that (1) large dams reduce downstream native plant diversity, (2) dam removal may restore it, and (3) given the natural dynamics of riparian vegetation, long-term, multiyear before-and-after monitoring is essential for understanding dam removal effects.

Analysis of riparian vegetation of a recreation site in Jeli, Kelantan

Lata Keding is recognised as one of the recreational areas in Jeli, Kelantan. It has the function to protect the riparian plant habitats but it is potentially threatened by anthropogenic activities. This study was aimed to determine riparian plant species diversity and estimate species abundance of riparian plant vegetation at Lata Keding, Jeli, Kelantan. The line transect method was used to collect vegetation data. The line transect was established about one km long and each plant species that exist within 3 m up to 5 m from the river bank were recorded. A total of 2389 individuals belonging to 36 families and 49 species were recorded in the study area. Species diversity with Shannon-Wiener Diversity Index (H’) with a value of 2.89, while Hmax was 3.99 and Evenness Index (EH) value was 0.72 for the study area. The most dominant families recorded with a high diversity of plant species were Family Melastomataceae (5 species), Asteraceae (5 species) and Fabaceae (3 species). A total of 529 individuals of Clidemia hirta from Family Melastomataceae was recorded as the most dominant species. Thirty-six species are classified as Not Evaluated (NE), six species classified as Least Concern (LC), four species as Near Threatened (NT), two species Vulnerable (VU) and one species listed as Critically Endangered (CR).

Photosynthetic acclimation of riparian plant Distylium chinense to heterogeneous habitats

Distylium chinense is an evergreen dominant shrub with strong adaptability under heterogeneous habitats, including natural riparian zone (NRZ), anti-seasonal water level fluctuation zone (ASWLFZ), and no water level fluctuation zone (NWLFZ) in the Three Gorges Reservoir Region (TGRR) in China. In order to understand the photosynthetic ecological adaptability and habitat adaptation strategies of D. chinense under heterogeneous habitats, its photosynthesis and chlorophyll fluorescence parameters were investigated. The results showed that photosynthetic characteristics were significantly different among heterogeneous habitats (p<0.05). The PSII potential activity and PSII maximum photochemical efficiency (Fv/Fm) of D. chinense in the ASWLFZ were the highest among heterogeneous habitats. Non-photochemical quenching coefficient (qN) in the NWLFZ was higher than that in the NRZ and ASWLFZ (p<0.05). Stepwise regression analysis showed that water use efficiency and stomatal conductance were correlated with specific leaf area (SLA), leaf area and leaf dry weight. Regression curve fitting and canonical correspondence analysis revealed that light intensity, soil water content, air humidity and temperature were the main factors affecting photosynthetic characteristics and leaf functional traits. Our results evidenced that D. chinense adapted to the high water content and low light intensity environments, especially in the valley waterfall habitats, by increasing stomatal conductance and net photosynthetic rate, reducing SLA and maintaining moderate qN and Fv/Fm with adopting a profligate water use pattern to improve photosynthetic productivity. Therefore, D. chinense has a wide photosynthetic acclimation to different environments, which provided baseline information for the conservation and ecological restoration in the newly formed hydro-fluctuation zone and other similar degenerative riparian ecosystem.

A Green New Balance: Interactions among riparian vegetation plant traits and morphodynamics in alluvial rivers

AbstractThe strength of interactions between plants and river processes is mediated by plant traits and fluvial conditions, including above‐ground biomass, stem density and flexibility, channel and bed‐material properties, and flow and sediment regimes. In many rivers, concurrent changes in (1) the composition of riparian vegetation communities as a result of exotic species invasion and (2) shifts in hydrology have altered physical and ecological conditions in a manner that has been mediated by feedbacks between vegetation and morphodynamic processes. We review how Tamarix, which has invaded many southwestern US waterways, and Populus species, woody pioneer trees that are native to the region, differentially affect hydraulics, sediment transport, and river morphology. We draw on flume, field, and modelling approaches spanning the individual seedling to river‐corridor scales. In a flume study, we found that differences in the crown morphology, stem density, and flexibility of Tamarix compared to Populus influenced near‐bed flow velocities in a manner that favoured aggradation associated with Tamarix. Similarly, at the patch and corridor scales, observations confirmed increased aggradation with increased vegetation density. Furthermore, long‐term channel adjustments were different for Tamarix‐ versus Populus‐dominated reaches, with faster and greater geomorphic adjustments for Tamarix. Collectively, our studies show how plant‐trait differences between Tamarix and Populus, from individual seedlings to larger spatial and temporal scales, influence the co‐adjustment of rivers and riparian plant communities. These findings provide a basis for predicting changes in alluvial riverine systems which we conceptualize as a Green New Balance model that considers how channels may adjust to changes in plant traits and community structure, in addition to alterations in flow and sediment supply. We offer suggestions regarding how the Green New Balance can be used in management and invasive species management.

Gene flow in a pioneer plant metapopulation (Myricaria germanica) at the catchment scale in a fragmented alpine river system

River alterations for natural hazard mitigation and land reclamation result in habitat decline and fragmentation for riparian plant species. Extreme events such as floods are responsible for additional local species loss or population decline. Tributaries might provide refugia and subsequent source populations for the colonization of downstream sites in connected riverine networks with metapopulations of plant species. In this study, we analyzed the metapopulation structure of the endangered riparian shrub species Myricaria germanica along the river Isel, Austria, which is part of the Natura 2000 network, and its tributaries. The use of 22 microsatellite markers allowed us to assess the role of tributaries and single populations as well as gene flow up- and downstream. The analysis of 1307 individuals from 45 sites shows the influence of tributaries to the genetic diversity at Isel and no overall isolation by distance pattern. Ongoing bidirectional gene flow is revealed by the detection of first-generation migrants in populations of all tributaries as well as the river Isel, supporting upstream dispersal by wind (seeds) or animals (seeds and pollen). However, some populations display significant population declines and high inbreeding, and recent migration rates are non-significant or low. The genetic pattern at the mouth of river Schwarzach into Isel and shortly thereafter river Kalserbach supports the finding that geographically close populations remain connected and that tributaries can form important refugia for M. germanica in the dynamic riverine network. Conservation and mitigation measures should therefore focus on providing sufficient habitat along tributaries of various size allowing pioneer plants to cope with extreme events in the main channel, especially as they are expected to be more frequent under changing climate.

Research Advances in Plant Physiology and Ecology of Desert Riparian Forests under Drought Stress

Under drought stress, desert riparian forest plants are highly self-regulating and have their own unique water use and regulation strategies, which can respond positively in several aspects such as physiology, ecology, and individual phenotypes when coping and adapting to the stresses brought by external environmental changes. In addition, as an important component of arid zone ecosystems, desert riparian forest plants maintain the cycling process of energy and material in desert areas. Therefore, it is of great ecological value to study the role played by desert riparian forest plants in desertification control and biodiversity conservation in arid zones. The purpose of this study is to provide basic data and scientific basis for the conservation, and restoration of desert riparian forests in the inland river basin of arid zone. In this paper, the physiological and ecological responses of desert riparian plants under drought stress were analyzed by reviewing the literature and focusing on the key scientific issues such as drought avoidance mechanisms, water use, and water redistribution, and the relationship between interspecific water competition and resource sharing of desert riparian plants. The results showed that: (1) In the inland river basin of arid zone, desert riparian plants show a mutual coordination of increasing soluble sugars, proline, malondialdehyde (MDA), and decreasing peroxidase (POD), to form a unique drought avoidance mechanism, and improve their drought tolerance by changing leaf stomatal conductance resulted from regulating abscisic acid (ABA) and cytokinin (CTK) content. (2) Desert riparian forest plants have their own unique water use and regulation strategies. When the degree of drought stress increased, Populus euphratica enhanced the water flow of dominant branches by actively sacrificing the inferior branches to ensure and improve the overall survival chances of the plant, while Tamarix ramosissima weaken hydraulic conductance, and increase subsurface material inputs by reducing plant height to cope with drought stress. (3) The root systems of desert riparian plants have hydraulic uplift and water redistribution functions, and, in the hydraulic uplift process of P. euphratica and T. ramosissima root systems, there is a possibility of assisting with other species in water utilization and the existence of a resource sharing mechanism.