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1.
J Environ Manage ; 301: 113898, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34626943

RESUMO

In shallow eutrophic lakes, submersed macrophytes are essential for maintaining a clear water state, and they are affected markedly by fishes directly through herbivory and indirectly by fish-invertebrate-periphyton complexity, a pathway that presently is not well understood in subtropical lakes but probably vital to lake managements. We conducted a mesocosm study involving benthic fish (Misgurnus anguillicaudatus), snails (Radix swinhoei) and submersed macrophyte (Vallisneria natans), aiming to examine whether benthic fish is detrimental to reestablishment of clear-water macrophyte-dominated state in eutrophic degraded lakes. In addition, we aimed to investigate the cascading effect that benthic fish might have on periphyton and phytoplankton and to what extent snails can alleviate this effect. Our results showed that benthic fish promoted nutrient release from the sediment and thereby facilitated the growth of phytoplankton and periphyton, leading to reduced growth of submerged macrophytes due to shading. Snails consumed the periphyton attached on the leaves of macrophytes, thereby being beneficial to the plant growth, albeit it could not fully counteract the adverse effects from benthic fish. The water quality indicators in terms of nutrients concentrations, phytoplankton biomass and light extinction coefficient along the water column was affected primarily by benthic fish, followed by macrophytes and snails. To target a clear-water condition, the water quality was best at the presence of macrophytes alone or in combination with snails, and worst at the presence of benthic fish. Our results implied that the removal of benthic fish should be a useful ecological restoration method for rehabilitation of submersed macrophytes and water quality improvement in subtropic, eutrophic, shallow lakes following external nutrient loading reduction.


Assuntos
Hydrocharitaceae , Lagos , Animais , Biomassa , Peixes , Fósforo , Fitoplâncton
2.
Ecol Evol ; 11(14): 9827-9836, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34306665

RESUMO

Spatiotemporal variation in community composition is of considerable interest in ecology. However, few studies have focused on seasonal variation patterns in taxonomic and functional community composition at the fine scale. As such, we conducted seasonal high-density sampling of the submerged macrophyte community in Hongshan Bay of Erhai Lake in China and used the generalized dissimilarity model (GDM) to evaluate the effects of environmental factors and geographic distance on taxonomic and functional beta diversity as well as corresponding turnover and nestedness components. At the fine scale, taxonomic turnover and nestedness as well as functional turnover and nestedness showed comparable contributions to corresponding taxonomic and functional beta diversity, with different importance across seasons. All taxonomic and functional dissimilarity metrics showed seasonal variation. Of note, taxonomic beta diversity was highest in summer and lowest in winter, while functional beta diversity showed the opposite pattern. Taxonomic and functional turnover showed similar change patterns as taxonomic and functional beta diversity. Taxonomic nestedness was low in summer and high in winter. Functional nestedness was also lower in summer. These results suggest that under extreme environmental conditions, both turnover and nestedness can exist at the fine scale and seasonal community composition patterns in submerged macrophytes should be considered. Future investigations on community assembly mechanisms should pay greater attention to long-term dynamic characteristics and functional information.

3.
Sci Total Environ ; 713: 136734, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-32019051

RESUMO

Benthivorous fish disturbance and snail herbivory are two important factors that determine the community structure of submersed macrophytes. We conducted an outdoor mesocosm experiment to examine the separate and combined effects of these two factors on water quality and the growth of two mixed-cultivation submersed macrophytes, Vallisneria natans and Hydrilla verticillata, with different growth forms. The experiment involved two levels of fish (Misgurnus anguillicaudatus) disturbance crossed with two levels of snail (Radix swinhoei) intensity. The results revealed that fish activity rather than snail activity significantly increased the overlying water concentrations of total suspended solids (TSS), total nitrogen (TN), ammonia nitrogen (N-NH4), total phosphorus (TP) and phosphate phosphorus (P-PO4). However, no differences among treatments were observed for chlorophyll a (chl a) concentrations. Fish disturbance or snail herbivory alone did not affect the relative growth rate (RGR) of H. verticillata, but their combined effects significantly decreased the RGR of H. verticillata. Although snail herbivory alone did not affect the RGR of V. natans, fish disturbance alone and the combined effects of these factors drastically reduced its RGR. Both species exhibited increased free amino acid (FAA) contents and decreased ramet numbers, soluble carbohydrate (SC) contents and starch contents in the presence of the fish. Moreover, compared to H. verticillata, V. natans showed exceedingly low ramet numbers and starch contents in the presence of the fish. H. verticillata had a higher RGR and summed dominance ratio (SDR2) than V. natans in all treatments; H. verticillata also displayed a larger competitive advantage in the presence of fish disturbance. The present study suggests that (1) fish disturbance rather than snail activity increases water nutrient concentrations, (2) low snail density may be harmful to submersed macrophyte growth when the plants are under other abiotic stress conditions and (3) the competitive advantage of H. verticillata over V. natans is more preponderant in a turbid environment.


Assuntos
Herbivoria , Qualidade da Água , Animais , Clorofila A , Hydrocharitaceae , Fósforo
4.
Sci Total Environ ; 704: 135269, 2020 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-31796282

RESUMO

Low underwater light availability and benthivorous fish-mediated disturbance are two important factors that influence the growth of submersed macrophytes. However, the combined effects of these factors remain unclear. To determine the combined effects of low light and fish-mediated disturbance on the growth of two submersed macrophytes with contrasting growth forms, i.e., Vallisneria natans and Hydrilla verticillata, we conducted an outdoor mesocosm experiment with a two-by-two factorial design. The experiment involved two fish-mediated disturbance levels (0 and 1 Misgurnus anguillicaudatus) crossed with two levels of light intensity (ambient light and a low-light environment created by culturing the macrophytes under a shelter). The results showed that the chlorophyll a (chl a) concentration in the overlying water showed no difference among treatments for each macrophyte species. The fish-mediated disturbance significantly decreased the relative growth rate (RGR) of both species in the low-light environment but showed no effects in the ambient light environment. Low light availability and/or fish-mediated disturbance led to increased plant heights of both species compared with the heights under the ambient light regime. Low light availability combined with fish-mediated disturbance significantly reduced the ramet number and soluble carbohydrate (SC) content of both species; however, the free amino acid (FAA) content was not affected. Compared to V. natans, H. verticillata exhibited a high RGR and high ramet numbers in a low-light environment combined with fish-mediated disturbance. Our results indicated that the adaptability of H. verticillata is better than that of V. natans in turbid, shallow and hydrostatic water. Fish-mediated disturbance can negatively influence submersed macrophyte recovery in lakes when light is not abundant.


Assuntos
Clorofila A/análise , Peixes/fisiologia , Hydrocharitaceae/fisiologia , Animais , Lagos , Nitrogênio , Fósforo , Luz Solar
5.
Front Plant Sci ; 10: 442, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31031783

RESUMO

Leaf soluble carbohydrates (SC), free amino acids (FAA), starch, total phenolics (TOPH), carbon (C), and nitrogen (N) stoichiometry of 24 aquatic macrophyte species were studied at 52 selected sites in eastern, 31 sites in southwestern and 6 sites in western China, including 12 submerged, 6 floating-leaved, 4 emergent and 2 free-floating macrophytes. The leaf stoichiometric characteristics differed significantly among the plant species of the four different life forms, the lowest C content occurring in submerged macrophytes and the highest N content in free-floating macrophytes. Overall, though the variance explained by the linear regression models was low, the C and N contents decreased toward the northern latitudes, the C content and the C:N ratios increased with increasing altitude. Multiple regressions revealed that the stoichiometric characteristics of submerged macrophytes varied significantly across the large spatial and climatic gradients and among the species studied. For floating-leaved and emergent macrophytes, no correlation between climate factors and SC, FAA, starch, TOPH, C, and N contents and C:N ratio was observed. For free-floating macrophytes, the TOPH content was markedly positively correlated with latitude and altitude. We conclude that the C and N contents related more closely to latitude, altitude or mean annual air temperature than did the C and N metabolic indicators for the submerged macrophytes, while the relationships with the metabolic indicators turned out to be insignificant for most species of the other life forms. The results helped us to identify species with significant physiological plasticity across geographic and climatic gradients in China, and such information is useful when conducting restoration of lost aquatic plants in different climate regions.

6.
Front Plant Sci ; 10: 169, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30842784

RESUMO

Light is a major limiting resource in aquatic ecosystems and numerous studies have investigated the response of submerged macrophytes to low light conditions. However, few studies have tested whether different light response strategies can also have consequences for macrophyte distribution along different littoral slopes in lakes, which are known to affect macrophyte biomass due to differences in drag forces and sediment characteristic. In this study, we tested (1) whether two macrophyte species of different growth forms (canopy-forming: Potamogeton maackianus, rosette-type: Vallisneria natans) differ in their response strategies to low light conditions and (2) how these responses influence their distribution along different basin slopes in the mesotrophic Lake Erhai, China. We hypothesized that the canopy-forming species responds to low light conditions at deeper sites by stem elongation while the rosette-type species increases its shoot chlorophyll content. As a consequence, P. maackianus should have a higher susceptibility to drag forces and thus prevail at sites with lower slopes. Sites with higher slopes should offer a niche for rosette-type species like V. natans that can better withstand drag forces. We surveyed the distribution and abundance of the two macrophyte species at 527 sampling points along 97 transects in Lake Erhai and measured their height, leaf and stem/rhizome biomass, and leaf chlorophyll a content at different water depths. Our results confirmed stem elongation as a strategy to low light conditions by the canopy-forming species P. maackianus, while V. natans produced more chlorophyll a per shoot biomass at deeper sites to tolerate shading. As hypothesized, these alternative response strategies to low light conditions resulted in a trade-off regarding the plants ability to grow at different basin slopes. P. maackianus was dominant at sites with low-moderate slope (0-4%) and low-moderate water depth (2-4 m), while sites with high basin slope (4-7%) combined with moderate-high water depth (3-5 m) were dominantly colonized by V. natans. The latter habitat thus represents a potential refuge for rosette-type macrophyte species that are often outcompeted when shading increases during eutrophication.

7.
Environ Sci Pollut Res Int ; 25(34): 34027-34045, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30280343

RESUMO

Few studies have focused on the biomechanical responses of submerged, rosette-forming macrophytes to wave action, water depth, or their co-occurrence in naturally eutrophic systems. The plant architecture, root anchorage strength-related traits, leaf morphology, and biomechanics of Vallisneria natans inhabiting a range of water depths were examined along three transects (T1, T2, and T3) in a eutrophic lake, Lake Erhai, in Yunnan Province, China. These transects were exposed to weak wave action and hyper-eutrophication (T1), moderate wave action and eutrophication (T2), or strong wave action and eutrophication (T3). The results showed that V. natans was mainly distributed at intermediate depths, with the widest colonization depth in T1. The values of plant architecture, root anchorage strength-related traits, leaf morphology, and biomechanics were generally highest in T3 and smallest in T2. Along the depth gradient, these values were generally highest at 3.5, 2.5, and 2.5 m for the plants growing in T1, T2, and T3, respectively. These findings suggest that V. natans adopts a "tolerance" strategy to cope with the effects of strong wave action in eutrophic habitats and an "avoidance" strategy when exposed to moderate wave action in eutrophic areas. Since the absence of an avoidance strategy increases the resistance to low-light stress at the expense of increased drag forces, there is a limit to the wave action that V. natans can withstand. This study indicates that biomechanics could be important when determining the distribution pattern of V. natans in Lake Erhai.


Assuntos
Hydrocharitaceae/fisiologia , Lagos , Fenômenos Biomecânicos , China , Ecossistema , Eutrofização , Hydrocharitaceae/anatomia & histologia , Folhas de Planta/fisiologia , Raízes de Plantas/fisiologia
8.
Huan Jing Ke Xue ; 39(1): 219-226, 2018 Jan 08.
Artigo em Chinês | MEDLINE | ID: mdl-29965685

RESUMO

The anaerobic-anoxic-oxic (AAO) process was used to investigate the variation of the parameters of water quality when the dissolved oxygen (DO) in the aerobic tank was controlled at a low concentration. The results indicated the system still had good phosphorus and nitrogen removal efficiencies when the DO concentration in the aerobic tank was decreased from 2.00 mg·L-1 to 1.00 mg·L-1 and 0.50 mg·L-1, and the effluent indexes could meet the first class A standard for the "discharge standard of pollutants for municipal wastewater treatment plant" (GB18918-2002) of China. The activated sludge model of the AAO process was developed by BioWin 4.1 software. The sensitivities of the model parameters were analyzed, and the model parameters, such as amount of polyhydroxyalkanoate (PHA) stored per unit of acetate or the propionate sequestered by phosphorus accumulating bacteria (YP/PHA,seq), the amount of phosphorus stored per unit of PHA oxidized in aerobic conditions by phosphorus accumulating bacteria (YP/PHA,aerobic), the maximum specific growth rate of ammonia oxidizing bacteria (µmax,A), and the maximum specific growth rate of nitrite oxidizing bacteria (µmax,N), were calibrated and validated by the dynamic simulation. In addition, the energy consumption of the aeration was simulated and evaluated. The results showed that when the DO concentration in the aerobic tank was decreased from 2.00 mg·L-1 to 1.00 mg·L-1 and 0.50 mg·L-1, the air flow could be reduced by 23.8% and 38.1%, and the oxygen transfer efficiency could be increased by 7.2% and 11.7%, respectively.


Assuntos
Reatores Biológicos , Nitrogênio/isolamento & purificação , Oxigênio/química , Fósforo/isolamento & purificação , Eliminação de Resíduos Líquidos , Bactérias/metabolismo , China , Esgotos
9.
Sci Total Environ ; 625: 1433-1445, 2018 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-29996440

RESUMO

The geo-engineering approach of modified soil flocculation has been widely applied to mitigate algal blooms and eutrophication in relatively small lakes. Nevertheless, its potential ecological risks and feasibility should be examined and identified prior to its application in large natural lakes given the multiple functions of these water bodies in human health and welfare. In situ mesocosm experiments on modified soil flocculation were performed in Lake Taihu during summer 2010 and 2011. Chitosan-modified kaolinite (CMK) soil was used to flocculate algal blooms and improve water transparency to facilitate the re-establishment of the submersed macrophyte Vallisneria natans in this shallow eutrophic lake. Moreover, the ecological effects of CMK soil were assessed. Results showed that repeated additions of CMK (0.3g/L for each time) improved water quality in terms of Chl-a, TN, and TP concentrations; TN/TP ratio; turbidity; redox conditions; and nitrification and denitrification activities. These effects lasted for 48days. After the fourth dose of CMK, the biomass of all phytoplankton categories, except for that of Cryptophyta, decreased by >90% (ca. 1-2×106cell/L or 0.38-0.55mg/L of wet weight). Zooplankton biomass markedly decreased after the first CMK addition, and copepods became dominant. These effects, however, did not last for the long term. Most importantly, submersed V. natans was restored successfully when water clarity and quality were improved through repeated CMK flocculation. Nevertheless, the indices of carbohydrate depletion and free amino acid accumulation indicated that the plant experienced physiological stresses. The reestablishment of V. natans reinforced the positive effects of repeated CMK dosing on water quality, and promoted a clear water state. V. natans is recommended for vegetative restoration in shallow eutrophic lakes given its facile transplantation, high stress tolerance, and physiological traits, which can be applied as indices of post-flocculation effects. In summary, the combination of repeated CMK dosing and revegetation of V. natans can feasibly improve water quality and initiate the restoration of a clear water state in shallow eutrophic lakes.


Assuntos
Recuperação e Remediação Ambiental/métodos , Floculação , Lagos/química , Plantas , Solo/química , Poluentes da Água/análise , Biomassa , China , Monitoramento Ambiental , Eutrofização , Nitrogênio/análise , Fósforo/análise , Fitoplâncton
10.
Sci Total Environ ; 622-623: 421-435, 2018 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-29220767

RESUMO

Eutrophication and hydrodynamics determine the final distribution patterns of aquatic macrophytes; however, there is limited available knowledge regarding their interactive effects. Morphological and biomechanical responses to eutrophication and hydrodynamic stresses were assessed by sampling five abundant and dominant species, Potamogeton maackianus, P. pectinatus, P. lucens, Ceratophyllum demersum and Myriophyllum spicatum, in three macrophyte beds in Lake Erhai, Yunnan Province, China: one exposed to eutrophication and moderate southeast (SE) wind; one with mesotrophication, but sheltered by the lakeshore, with weak wind disturbance; and one with meso-eutrophication and strong SE wind. The results showed significant interactive effects of eutrophication and hydrodynamics on most biomechanical traits and some morphological traits, suggesting that aquatic macrophytes preferentially undergo biomechanical adjustments to resist the coexisting eutrophication and hydrodynamic stresses. In particular, hydrodynamics increased both the tensile force and tensile strain of P. maackianus under meso-eutrophication and dramatically decreased them in eutrophic areas, suggesting that eutrophication triggers mechanical failure in this species. Additionally, P. pectinatus, C. demersum and M. spicatum showed the lowest and highest values for the biomechanical variables (greater values for M. spicatum) in the most eutrophic and hydrodynamic areas, respectively, implying that increases in hydrodynamics primarily induce mechanical damage in eutrophic species. The plants generally exhibited greater tensile strain in both shallow and deep waters and the greatest tensile force at moderate depths. The stem cross-sectional area, plant height, stem length, internode length, and branch traits were all responsible for determining the biomechanical variables. This study reveals that hydrodynamic changes primarily induce mechanical damage in eutrophic species, whereas eutrophication triggers mechanical damage in sensitive species.


Assuntos
Monitoramento Ambiental , Eutrofização , Hidrodinâmica , Potamogetonaceae/fisiologia , Traqueófitas/fisiologia , China , Lagos
11.
Sci Rep ; 7(1): 8294, 2017 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-28811648

RESUMO

Ecological processes are generally scale-dependent and there is little consensus about the relative importance of deterministic versus stochastic processes in driving patterns of biological diversity. We investigated how the relationship between functional dispersion and environmental gradients changes with spatial scale in subtropical freshwater lakes. The functional alpha and beta dispersions of all the tested traits were significantly under-dispersed across spatial scales and along environmental gradients. Results showed more functional similarity within communities in leaf dry mass content and flowering duration but less functional turnover among communities in all the tested traits at regional scales (Yunnan-Guizhou plateau and the middle and low reaches of the Yangtze River). The strengths and directions of environmental effects on the functional alpha and beta dispersions depended on the selected traits, diversity metrics and spatial scales. Surprisingly, broad-scale factors - elevation and water transparency - decreased the functional turnover for most traits along the gradients, whereas fine-scale factors - water depth - produced the opposite patterns along the gradient, depending on the trait selected. Our study highlights the dominant role of deterministic assembly processes in structuring the local functional composition and governing the spatial functional turnover of macrophyte communities across multiple spatial scales.


Assuntos
Biodiversidade , Clima , Ecossistema , Água Doce/microbiologia , Lagos/microbiologia , Meio Ambiente , Análise Espacial
12.
Environ Sci Pollut Res Int ; 24(9): 8108-8119, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28144862

RESUMO

The present study was carried out to determine the efficacy of root foraging and the physiological response of Vallisnaria natans grown in heterogeneous sediments. V. natans was cultivated in two homogeneous and two heterogeneous sediments. The results suggested that V. natans grown in heterogeneous sediments presented a significantly higher root proportion in its total biomass, exhibited root foraging, and grew well, as indicated by a total biomass, ramet number, and plant height very close to those of plants grown in nutrient-rich clay sediment. Moreover, the more sensitive physiological response of the roots than the stems or the leaves to sediment nutrients suggested that root foraging occurred, and the approached values between the two heterogeneous sediments and the homogeneous clay sediment indicated that V. natans could satisfy its nutrient requirements via root foraging. The results may be useful in the recovery of macrophytes that remodel part (rather than all) of the substrate and can potentially improve habitats that are unsuitable for plant growth.


Assuntos
Hydrocharitaceae/crescimento & desenvolvimento , Raízes de Plantas/crescimento & desenvolvimento , Biomassa , Sedimentos Geológicos , Folhas de Planta/crescimento & desenvolvimento , Caules de Planta/crescimento & desenvolvimento
13.
Sci Rep ; 6: 34028, 2016 10 03.
Artigo em Inglês | MEDLINE | ID: mdl-27694880

RESUMO

To evaluate the relative importance of photosynthetic versus morphological adaptations of submersed macrophytes to low light intensity in lakes, rapid light curves (RLCs), morphological parameters, relative growth rate (RGR), clonal reproduction and abundance of two submersed macrophytes (Potamogeton maackianus and Vallisneria natans) were examined under 2.8%, 7.1%, 17.1% and 39.5% ambient light in a field and outdoor experimental study. The plants increased their initial slope of RLCs (α) and decreased their minimum saturating irradiance (Ek) and maximum relative electron transport rate (ETRm) of RLCs under low light stress, but V. natans was more sensitive in RLCs than P. maackianus. Accordingly, the RGR, plant height and abundance of P. maackianus were higher in the high light regimes (shallow water) but lower in the low light regimes than those of V. natans. At the 2.8% ambient light, V. natans produced ramets and thus fulfilled its population expansion, in contrast to P. maackianus. The results revealed that P. maackianus as a canopy-former mainly elongated its shoot length towards the water surface to compensate for the low light conditions, however, it became limited in severe low light stress conditions. V. natans as a rosette adapted to low light stress mainly through photosynthetic adjustments and superior to severely low light than shoot elongation.

14.
Environ Sci Pollut Res Int ; 23(22): 22577-22585, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27557960

RESUMO

Carbon (C), nitrogen (N) and phosphorus (P) are the three most important essential elements limiting growth of primary producers. Submerged macrophytes generally absorb nutrients from sediments by root uptake. However, the C:N:P stoichiometric signatures of plant tissue are affected by many additional factors such as taxonomy, nutrient availability, and light availability. We first revealed the relative importance of taxonomy, sediment, and water column on plant C:N:P stoichiometry using variance partitioning based on partial redundancy analyses. Results showed that taxonomy was the most important factor in determining C:N:P stoichiometry, then the water column and finally the sediment. In this study, a significant positive relationship was found between community C concentration and macrophyte community biomass, indicating that the local low C availability in macrophytes probably was the main reason why submerged macrophytes declined in Yangtze floodplain shallow lakes. Based on our study, it is suggested that submerged macrophytes in Yangtze floodplain shallow lakes are primarily limited by low light levels rather than nutrient availability.


Assuntos
Carbono/química , Sedimentos Geológicos/química , Nitrogênio/química , Fósforo/química , Plantas/química , Biomassa , China , Lagos , Plantas/classificação
15.
PLoS One ; 10(7): e0131630, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26167856

RESUMO

Trait-based approaches have been widely applied to investigate how community dynamics respond to environmental gradients. In this study, we applied a series of maximum entropy (maxent) models incorporating functional traits to unravel the processes governing macrophyte community structure along water depth gradient in a freshwater lake. We sampled 42 plots and 1513 individual plants, and measured 16 functional traits and abundance of 17 macrophyte species. Study results showed that maxent model can be highly robust (99.8%) in predicting the species relative abundance of macrophytes with observed community-weighted mean (CWM) traits as the constraints, while relative low (about 30%) with CWM traits fitted from water depth gradient as the constraints. The measured traits showed notably distinct importance in predicting species abundances, with lowest for perennial growth form and highest for leaf dry mass content. For tuber and leaf nitrogen content, there were significant shifts in their effects on species relative abundance from positive in shallow water to negative in deep water. This result suggests that macrophyte species with tuber organ and greater leaf nitrogen content would become more abundant in shallow water, but would become less abundant in deep water. Our study highlights how functional traits distributed across gradients provide a robust path towards predictive community ecology.


Assuntos
Ecossistema , Entropia , Lagos , Modelos Teóricos , Plantas/metabolismo , China , Especificidade da Espécie
16.
Ecol Evol ; 4(9): 1516-23, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24967072

RESUMO

Functional trait composition of plant communities has been proposed as a helpful key for understanding the mechanisms of biodiversity effects on ecosystem functioning. In this study, we applied a step-wise modeling procedure to test the relative effects of taxonomic diversity, functional identity, and functional diversity on macrophytes community productivity along water depth gradient. We sampled 42 plots and 1513 individual plants and measured 16 functional traits and abundance of 17 macrophyte species. Results showed that there was a significant decrease in taxonomic diversity, functional identity (i.e., stem dry mass content, leaf [C] and leaf [N]), and functional diversity (i.e., floating leaf, mean Julian flowering date and rooting depth) with increasing water depth. For the multiple-trait functional diversity (FD) indices, functional richness decreased, while functional divergence increased with water depth gradient. Macrophyte community productivity was strongly determined by functional trait composition within community, but not significantly affected by taxonomic diversity. Community-weighted means (CWM) showed a two times higher explanatory power relative to FD indices in determining variations in community productivity. For nine of sixteen traits, CWM and FD showed significant correlations with community productivity, although the strength and direction of those relations depended on selected trait. Furthermore, functional composition in a community affected productivity through either additive or opposite effects of CWM and FD, depending on the particular traits being considered. Our results suggested both mechanisms of mass ratio and niche complementarity can operate simultaneously on variations in community productivity, and considering both CWM and FD would lead to a more profound understanding of traits-productivity relationships.

17.
Front Plant Sci ; 4: 263, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23882277

RESUMO

Many plants employ energized loading strategies to accumulate osmotically-active solutes into the phloem of source organs to accentuate the hydrostatic pressure gradients that drive the flow of water, nutrients and signals from source to sinks. Proton-coupled symport of sugars from the apoplasm into the phloem symplasm is the best studied phloem-loading mechanism. As an alternative, numerous species use a polymer trapping mechanism to load through symplasm: sucrose enters the phloem through specialized plasmodesmata and is converted to raffinose-family oligosaccharides (RFOs) which accumulate because of their larger size. In this study, metabolic engineering was used to generate RFOs at the inception of the translocation stream of Arabidopsis thaliana, which loads from the apoplasm and transports predominantly sucrose, and the fate of the sugars throughout the plant determined. Three genes, GALACTINOL SYNTHASE, RAFFINOSE SYNTHASE and STACHYOSE SYNTHASE, were expressed from promoters specific to the companion cells of minor veins. Two transgenic lines homozygous for all three genes (GRS63 and GRS47) were selected for further analysis. Three-week-old plants of both lines had RFO levels approaching 50% of total soluble sugar. RFOs were also identified in exudates from excised leaves of transgenic plants whereas levels were negligible in exudates from wild type (WT) leaves. Differences in starch accumulation between WT and GRS63 and GRS47 lines were not observed. Similarly, there were no differences in vegetative growth between WT and engineered plants, but the latter flowered slightly earlier. Finally, since the sugar composition of the translocation stream appeared altered, we tested for an impact on green peach aphid (Myzus persicae Sulzer) feeding. When given a choice between WT and transgenic plants, green peach aphids preferred settling on the WT plants. Furthermore, green peach aphid fecundity was lower on the transgenic plants compared to the WT plants. When added to an artificial diet, RFOs did not have a negative effect on aphid fecundity, suggesting that although aphid resistance in the transgenic plants is enhanced, it is not due to direct toxicity of RFO toward the insect.

18.
PLoS One ; 8(4): e62794, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23626856

RESUMO

Although functional trait variability is increasingly used in community ecology, the scale- and size-dependent aspects of trait variation are usually disregarded. Here we quantified the spatial structure of shoot height, branch length, root/shoot ratio and leaf number in a macrophyte species Potamogeton maackianus, and then disentangled the environmental and ontogenetic effects on these traits. Using a hierarchical nested design, we measured the four traits from 681 individuals across five ecological scales: lake, transect, depth stratus, quadrat and individual. A notable high trait variation (coefficient variation: 48-112%) was observed within species. These traits differed in the spatial structure, depending on environmental factors of different scales. Shoot height and branch length were most responsive to lake, transect and depth stratus scales, while root/shoot ratio and leaf number to quadrat and individual scales. The trait variations caused by environment are nearly three times higher than that caused by ontogeny, with ontogenetic variance ranging from 21% (leaf number) to 33% (branch length) of total variance. Remarkably, these traits showed non-negligible ontogenetic variation (0-60%) in each ecological scale, and significant shifts in allometric trajectories at lake and depth stratus scales. Our results highlight that environmental filtering processes can sort individuals within species with traits values adaptive to environmental changes and ontogenetic variation of functional traits was non-negligible across the five ecological scales.


Assuntos
Meio Ambiente , Interação Gene-Ambiente , Fenótipo , Característica Quantitativa Herdável , Traqueófitas/genética , Adaptação Fisiológica , Biomassa , China , Ecossistema
19.
Freshw Biol ; 58(12): 2532-2540, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25810562

RESUMO

Strategies of carbon (C) and nitrogen (N) utilisation are among the factors determining plant distribution. It has been argued that submersed macrophytes adapted to lower light environments are more efficient in maintaining C metabolic homeostasis due to their conservative C strategy and ability to balance C shortage. We studied how depth distributions of 12 submersed macrophytes in Lake Erhai, China, were linked to their C-N metabolic strategies when facing acute [Formula: see text] dosing.[Formula: see text] dosing changed C-N metabolism significantly by decreasing the soluble carbohydrate (SC) content and increasing the [Formula: see text]-N and free amino acid (FAA) content of plant tissues.The proportional changes in SC contents in the leaves and FAA contents in the stems induced by [Formula: see text] dosing were closely correlated (positive for SC and negative for FAA) with the colonising water depths of the plants in Lake Erhai, the plants adapted to lower light regimes being more efficient in maintaining SC and FAA homeostasis.These results indicate that conservative carbohydrate metabolism of submersed macrophytes allowed the plants to colonise greater water depths in eutrophic lakes, where low light availability in the water column diminishes carbohydrate production by the plants.

20.
Rapid Commun Mass Spectrom ; 25(21): 3267-73, 2011 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-22006389

RESUMO

Stable isotopic turnover with isotopic change due to growth and metabolic tissue replacement associated with a change in environmental conditions is a critical aspect of the use of stable isotope analyses as time-integrating tracers of resource-consumer interactions. However, stable isotopic turnover in plants remains poorly understood compared with those of animals, and here we used continuous flow elemental analyzer-isotopic ratio mass spectrometry (EA-IRMS) to analyse the turnover of stable carbon and nitrogen isotopes in a submersed macrophyte (Vallisneria natans) after transplantation to hypereutrophic and mesoeutrophic treatments in a field mesocosm experiment. The direction and magnitude of the isotopic shifts of V. natans were suggested to be determined by the inorganic nutrient availability and its isotopic content in the different treatments. Based on the modelling results of turnover, the contribution of growth to the isotopic turnover was as high as those observed in various aquatic ectotherms. However, the contribution of metabolism was also considerable, especially for nitrogen in the hypereutrophic treatment, which was argued to be a response, co-occurring with growth inhabitation and biochemical disorder of V. natans, to the stress induced by the eutrophication. Our results indicated that isotope turnover in a macrophyte is a feasible technique for estimating its ecophysiological conditions in the natural environment, and that it may facilitate understanding of isotopic data in field studies of food web and habitat restoration under eutrophic conditions.


Assuntos
Isótopos de Carbono/metabolismo , Eutrofização/fisiologia , Hydrocharitaceae/metabolismo , Isótopos de Nitrogênio/metabolismo , Isótopos de Carbono/análise , Ecossistema , Cadeia Alimentar , Hydrocharitaceae/crescimento & desenvolvimento , Espectrometria de Massas , Isótopos de Nitrogênio/análise
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