[Effects of Modified Distillers' Grains Biochar on Cadmium Forms in Purple Soil and Cadmium Uptake by Rice].

Biochar and modified biochar have been widely used as remediation materials in heavy metal-contaminated agricultural soils. In order to explore economical and effective materials for the remediation of cadmium (Cd)-contaminated acidic purple soil, distillers 'grains were converted into distillers' grains biochar (DGBC) and modified using nano-titanium dioxide (Nano-TiO2) to produce two types of modified DGBCs:TiO2/DGBC and Fe-TiO2/DGBC. A rice pot experiment was used to investigate the effects of different biochar types and application rates (1%, 3%, and 5%) on soil properties, nutrient content, Cd bioavailability, Cd forms, rice growth, and Cd accumulation. The results showed that:① DGBC application significantly increased soil pH, cation exchange capacity (CEC), and nutrient content, with TiO2/DGBC and Fe-TiO2/DGBC exhibiting better effects. ② DGBC and modified DGBCs transformed Cd from soluble to insoluble forms, increasing residual Cd by 1.22% to 18.46% compared to that in the control. Cd bioavailability in soil decreased significantly, with available cadmium being reduced by 11.81% to 23.67% for DGBC, 7.64% to 43.85% for TiO2/DGBC, and 19.75% to 55.82% for Fe-TiO2/DGBC. ③ DGBC and modified DGBCs increased rice grain yield, with the highest yields observed at a 3% application rate:30.60 g·pot-1 for DGBC, 37.85 g·pot-1 for TiO2/DGBC, and 39.10 g·pot-1 for Fe-TiO2/DGBC, representing 1.13, 1.40, and 1.44 times the control yield, respectively. Cd content in rice was significantly reduced, with grain Cd content ranging from 0.24 to 0.30 mg·kg-1 for DGBC, 0.16 to 0.26 mg·kg-1 for TiO2/DGBC, and 0.14 to 0.24 mg·kg-1 for Fe-TiO2/DGBC. Notably, Cd content in rice grains fell below the food safety limit of 0.2 mg·kg-1 (GB2762-2022) at 5% for TiO2/DGBC and 3% and 5% for Fe-TiO2/DGBC. In conclusion, Nano-TiO2 modified DGBC effectively reduced the bioavailability of soil Cd through its own adsorption and influence on soil Cd forms distribution, thus reducing the absorption of Cd by rice and simultaneously promoting rice growth and improving rice yield. It is a type of Cd-contaminated soil remediation material with a potential application prospect. The results can provide scientific basis for farmland restoration and agricultural safety production of Cd-contaminated acidic purple soil.

[Effects of Different Modifiers on Aggregates and Organic Carbon in Acidic Purple Soil].

The aim of this study was to examine the effects of different modifiers on the changes in aggregates and organic carbon in acidic purple soil， providing a scientific basis for the remediation of acidic purple soil. Using purple soil as the research object， a total of six treatments were set up， including no fertilization （CK）， single fertilization （F）， fertilization with lime （SF）， fertilization with organic fertilizer （OM）， fertilization with biochar （BF）， and fertilization with distiller's grains ash （JZ）. We compared the composition of aggregates in acidic purple soil under the application of different modifiers， as well as the distribution pattern of organic carbon in aggregates of different particle sizes. Combined with the stability indicators of aggregates， we sought to clarify the impact of different modifiers on the structure of aggregates in acidic purple soil. The results showed that fertilization significantly increased the soil pH， with the JZ treatment being the most effective. Fertilization significantly increased soil organic matter content， with the OM treatment showing the largest increase. The BF and OM treatments significantly reduced soil bulk density， whereas the SF and BF treatments significantly increased soil moisture content （P < 0.05）. All treatments used < 0.25 mm aggregates as the dominant particle size. Fertilization could significantly increase the content of large aggregates （aggregate structure units with diameter > 0.25 mm）. At the same time， fertilization treatments significantly increased the soil geometric mean diameter （GMD）， average weight diameter （MWD）， and R0.25 value （ > 0.25 mm aggregate content） and reduced the fractal cone number （D） and aggregate destruction rate （PAD） values （P < 0.05）. Fertilization also promoted the aggregation and stability of soil aggregates， with the OM treatment having the greatest effect. Compared with that in the CK treatment， fertilization could significantly increase soil organic carbon content by 31.71%-209.67%， with the OM treatment showing the most significant change. Different treatments of soil organic carbon were mainly distributed in large aggregates. Compared with that in the CK treatment， each treatment significantly increased the contribution rate of organic carbon in large aggregates by 19.34%-47.76%， with the OM treatment having the most significant effect （P < 0.05）. In general， chemical fertilizer combined with organic fertilizer could promote the formation of large aggregates in acidic purple soil， improve the stability of soil aggregates， and increase the content of soil organic carbon， which is an effective measure to improve the soil structure and improve the quality of acidic purple soil.

[Effects of Modified Distiller's Lees Biochar on Nutrients and Enzyme Activities in Purple Soil].

In order to investigate the effects of distiller's lees biochar and different modified distiller's lees biochars on soil properties, pot experiments were conducted to study the effects of different soil amendments (CK:no amendment, JZ:distiller's lees biochar, TiO2/JZ:Nano-TiO2 supported by distiller's lees biochar, and Fe/TiO2/JZ:titanium dioxide supported by iron-modified distiller's lees biochar) and the application rates of different amendments (1%, 3%, and 5%) on the characteristics of soil nutrients and enzyme activities under irrigation-drought rotation. The results showed the following:①the modified distiller's lees biochar significantly increased soil pH and CEC (P<0.05). At the 5% Fe-TiO2/JZ addition level, the soil pH reached 7.95 during the rice season, an increase of 2.3 units compared with that in the CK treatment; the CEC reached 12.06 cmol·kg-1, increasing by 21.38%; the soil pH reached 5.99 during the cabbage season and increased by 1.5 units compared with that in the CK treatment; and CEC reached 8.91 cmol·kg-1 at 3% Fe-TiO2/JZ addition and increased by 13.11%. ②At the same time, the contents of soil total nitrogen and available phosphorus were significantly increased (P<0.05). Compared with that in the CK treatment, the soil total nitrogen of 5% JZ, 5% TiO2/JZ, and 5% Fe-TiO2/JZ increased by 20.56%, 85.04%, and 59.61% in the rice season and 12.39%, 22.68%, and 23.70% in the cabbage season, respectively. In the rice season, the increase in soil available P under 5% Fe-TiO2/JZ was the highest, reaching 10.49 mg·kg-1, which was 1.64 times that under CK treatment. In the cabbage season, the soil available phosphorus (P) reached 90.15 mg·kg-1 under 5% TiO2/JZ addition, which increased by 93.38% compared with that in the CK treatment. ③Modified distiller's lees biochar increased catalase and urease activities and decreased alkali-hydrolytic nitrogen content and acid phosphatase activity. At the 3% addition level, catalase activity increased by 12.19%, 48.17%, and 37.30% in the rice season and 5.95%, 8.34%, and 17.42% in the cabbage season, respectively. In the rice season, the soil urease activity reached the maximum under 5% Fe-TiO2/JZ addition, which was increased by 40.90% compared with that in the CK treatment. In the cabbage season, the soil urease activity reached the maximum under 5% TiO2/JZ addition, which was increased by 58.53% compared with that in the CK treatment. The activity of acid phosphatase decreased by 5.39%-24.66% in the rice season and by 54.46%-61.40% in the cabbage season. Distiller's lees biochar and modified distiller's lees biochar could effectively increase soil pH and soil nutrient content, thus affecting soil enzyme activities. The application of iron modified-titanium dioxide-loaded distiller's lees biochar of 3% to 5% in acidic purple soil is more suitable.

[Effects of Chemical Fertilizer Reduction Combined with Organic Fertilizer Application on Bacterial Community Structure in Rhizosphere/Non-Rhizosphere Soil of Lemon].

The aim of this study was to examine the effects of different fertilization methods on the physicochemical properties and bacterial community structure of lemon rhizosphere/non-rhizosphere soil in order to provide theoretical basis for scientific and rational fertilization of orchards. A pot experiment was carried out, and six fertilization treatments were set up:control (CK), conventional fertilization (FM), organic fertilizer (P), fresh organic fertilizer (NP), 70% chemical fertilizer+30% organic fertilizer (70FP), and 50% chemical fertilizer+50% organic fertilizer (50FP). Chemical analysis, real-time fluorescence quantitative PCR, and terminal restriction fragment length polymorphism (T-RFLP) were used to study the effects of different fertilization treatments on the physicochemical properties of rhizosphere and non-rhizosphere soils, the abundance of the bacterial 16S rRNA gene, and bacterial community structure. Redundancy analysis (RDA) was used to explore the environmental factors affecting the bacterial community structure of lemon rhizosphere/non-rhizosphere soil. The results showed the following:① the pH and contents of organic matter, alkali-hydrolyzed nitrogen, available phosphorus, available potassium, and nitrate nitrogen in rhizosphere/non-rhizosphere soil were significantly increased by reducing the amount of chemical fertilizer and applying organic fertilizer (50FP and 70FP) (P<0.05). Compared with conventional fertilization (FM) and single application of organic fertilizer (P and NP), the soil available P content, available K content, and nitrate nitrogen content increased by 24.76%-97.98%, 6.87%-45.11%, and 18.42%-55.82%, respectively. ② Fertilizer reduction combined with organic fertilizer significantly increased the abundance of soil bacteria and soil respiration intensity (P<0.05), and the abundance of soil rhizosphere bacteria and soil respiration intensity under the 50FP treatment increased by 15.83%-232.98% and 8.0%-162.5% compared with that under conventional fertilization and organic fertilizer alone, respectively. The bacterial abundance of rhizosphere soil was positively correlated with the pH and contents of organic matter, total nitrogen, and total phosphorus. ③ The PCoA and RDA analysis results showed that the single organic fertilizer and organic fertilizer and chemical fertilizer de-weighting of rhizosphere bacterial community structure and not adding fertilizer had a bigger difference between processing, and the main environmental factors influencing the rhizosphere/non rhizosphere bacterial community structure were organic matter, total nitrogen, total phosphorus, total potassium, alkali solution nitrogen, nitrate nitrogen, and available potassium. Fertilizer reduction combined with organic fertilizer could significantly increase soil nutrient content, increase soil bacterial abundance, and change the bacterial community structure of rhizosphere soil, and the 50FP treatment yielded better results. Therefore, 50% Chemical fertilizer+50% organic fertilizer (50FP) was a better fertilization method to improve the physical and chemical properties of orchard soil, increase the abundance of soil bacteria, and improve the soil respiration intensity.

Belowground seed and bud banks play complementary roles in the potential recruitment of dominant macrophyte communities in a Yangtze River-connected floodplain wetland.

Both seed and bud banks play important roles in the recruitment and maintenance of macrophyte communities; however, few studies have investigated them simultaneously. We investigated the abundance, species composition, and seasonal patterns of seed and bud banks in two dominant macrophyte communities, Carex and Miscanthus, in the Dongting Lake wetlands. The seed densities of both communities were lower from November (after flooding) to March and increased dramatically before flooding (in May). The bud densities of the two dominant communities peaked in the coldest month of the year (January), decreased markedly in March, and were the lowest before flooding. The seed banks of the two macrophyte communities were mainly composed of annual species and a few perennial species, whereas the bud banks were composed of only dominant perennials. Furthermore, the perennial species present in bud banks did not occur in seed banks. Among the soil variables, the bud densities of both plant communities were negatively associated with soil bulk density, whereas the seed density of the Miscanthus community was positively associated with soil bulk density. Our results suggest that seed and bud banks are complementary in the potential recruitment of macrophyte communities; that is, bud banks regulate the demography of dominant perennials, and seed banks contribute to the recruitment and dispersal of annual species. Given the high abundance of annuals and near absence of the most dominant perennials in the seed bank, the bud banks of dominant perennial species should be more widely used in wetland restoration and management.

Exploring the relative contribution of flood regimes and climatic factors to Carex phenology in a Yangtze River-connected floodplain wetland.

Hydrological regimes can combine with climatic factors to affect plant phenology; however, few studies have attempted to quantify their complex influences on plant phenology in floodplain wetlands. We obtained phenological information on Carex vegetation through MODIS normalized difference vegetation index (NDVI) data during 2001-2020, and monthly field investigation during 2011-2020. We then explored how these data were correlated with climatic factors and flood regimes in a Yangtze River-connected floodplain wetland (Dongting Lake, China). Our results showed that warmer temperature tended to advance the start of the pre-flooding growing season (SOS1), with a relative contribution of 76.1 %. Flood rising time strongly contributed to controlling the end of the pre-flooding growing season. Flood recession time and inundation duration were dominant factors determining the start of the post-flooding growing season (SOS2). Earlier flood recession time and shortened inundation duration tended to advance the SOS2. Shortened inundation duration, earlier flood recession time, and lower solar radiation tended to advance the end of the post-flooding growing season. The phenology of Carex distributed at high-elevation areas was more affected by hydrology than that of Carex distributed at low-elevation areas. Thus, climatic factors strongly affect the phenology of Carex during the pre-flooding growing season, whereas flood regimes play a dominant role in determining the phenology in the post-flooding growing season. The different responses of Carex phenology to climatic and flooding factors may provide insights for the conservation and management of floodplain wetlands in Yangtze River because Carex are primary food source and habitat for herbivorous waterfowls.

High-light inhibition of two submerged macrophytes in a shallow water experiment.

The negative effects, caused by high light, on algae, terrestrial and marine aquatic plants are well documented; those negative effects on freshwater submerged plants are, however, not well known. We determined the negative effects of two common submerged species, Myriophyllum spicatum and Vallisneria natans, on their growth and reproduction in a shallow water experiment along an irradiance gradient. Our results highlighted that the plant mass, relative growth rate and shoot height of V. natans and M. spicatum, and root mass and root length:root mass of M. spicatum and leaf mass and shoot height:shoot mass of V. natans were significantly negatively affected in shallow water with high-light regime (>50 % of full light). While the ramet number of the two species was stimulated by from 20.0 to 36.4 %, and root length, root:shoot, chlorophyll (a:b), chlorophyll (a + b), leaf carbon, nitrogen and phosphorus contents of the two studied macrophytes were not significantly impacted by light. Our results indicated that the high-light inhibition of plant growth was greater on the shoots than on the roots of the plants, although these effects were significantly different between the two studied submerged species and among the measured traits. Accordingly, we should avoid negative effects caused by high light to improve the performance of submerged species when we conduct submerged aquatic vegetation restoration programmes in eutrophic lakes.

Concurrent effects of flooding regimes and floodwater quality on sediment properties in a Yangtze River-connected floodplain wetland: Insights from field investigations during 2011-2020.

Changes in flood regimes, floodwater quality, and macrophyte types may affect sediment characteristics post-flooding. However, few studies have attempted to unravel their complex influences in floodplain wetlands. From 2011 to 2020, the physical and chemical properties of surface layer sediment pre- and post-flooding was investigated through field surveys in the Dongting Lake wetland. Results indicated that the pre-flooding soil total phosphorus (TP) and total nitrogen (TN) exhibited an increasing trend during 2011-2020. Soil TP increased post-flooding relative to that pre-flooding. The changes in TN, sediment organic matter (SOM), sediment moisture content (SMC), and sediment bulk density (SBD) fluctuated over the years. The best-fitting multi-regression model demonstrated that the changes in sediment variables post-flooding showed a parabolic trajectory along the inundation duration (ID), except for SMC. Changes in soil properties post-flooding were negatively correlated with ID for sediment with a low IDs (<148 days). Meanwhile, changes in soil properties post flooding were positively correlated with ID for sediment with a high IDs (>193 days). Changes in SBD and SOM post-flooding were positively influenced by the TP content in the floodwater. These findings indicate that changes in the flooding regime, and water quality generated by anthropogenic disturbances such as the Three Gorges Dam significantly affect sediment properties, and subsequently influence the ecological functions of the Dongting Lake wetland.

Community Trait Responses of Three Dominant Macrophytes to Variations in Flooding During 2011-2019 in a Yangtze River-Connected Floodplain Wetland (Dongting Lake, China).

In lacustrine wetlands connected to rivers, the changes in flood regimes caused by hydrological projects lead to changes in the community traits of dominant macrophytes and, consequently, influence the structure and function of wetland vegetation. However, community trait responses of macrophytes to the timing and duration of flood disturbance have been rarely quantified. In 2011-2019, we investigated plant species diversity, density, and biomass in three dominant macrophyte communities (Carex brevicuspis C.B. Clarke, Miscanthus sacchariflorus (Maxim.) Hackel, and Polygonum hydropiper L.) through monthly field surveys in Dongting Lake wetlands. Partial least squares regressions were used to analyze how the variations in hydrological regimes affected plant community traits. Apparent inter-annual fluctuations in plant community traits were detected during 2011-2019. The species richness and Shannon index of diversity of Miscanthus and Polygonum communities increased, whereas the Shannon index of diversity of Carex community decreased. Variation in flooding had a greater effect on Polygonum and Carex community traits than on Miscanthus community traits. Flooding disturbed all plant communities, especially when the duration and timing varied. Shorter inundation periods caused the biomass of Miscanthus community to decline, and that of Carex and Polygonum communities to increase. Earlier flood recession caused the species richness and Shannon index of diversity of Polygonum and Miscanthus community to increase, and those of Carex community to decrease. These findings imply that shorter inundation durations and earlier flood recession generated by the operation of the Three Gorges Dam have changed the macrophyte growth pattern.

Testing the Growth Rate Hypothesis in Two Wetland Macrophytes Under Different Water Level and Sediment Type Conditions.

The growth rate hypothesis (GRH) states that a negative correlation exists between the growth rate and N:P and C:P ratios, because fast-growing organisms need relatively more phosphorus-rich RNA to support their high rates of protein synthesis. However, it is still uncertain whether the GRH is applicable in freshwater wetlands. Several studies have shown that water level and sediment type are key factors influencing plant growth and plant C:N:P characteristics in freshwater wetlands. Thus, this study aimed to elucidate the influence of these factors on plant growth and test the GRH under varying water levels and sediment conditions. We designed a controlled experiment at three water levels and under three sediment types using the two dominant plants (Carex brevicuspis and Polygonum hydropiper) in the East Dongting Lake wetland, and we further investigated the relative growth rate (RGR); concentrations of total carbon (TC), total nitrogen (TN), and total phosphorus (TP); and plant stoichiometry (ratios of C:N, C:P, and N:P) in the aboveground and belowground parts and whole plants in both species. Results demonstrated that the RGR and TC of both species decreased significantly with decreasing sediment nutrient supply and increasing water level. However, TN and TP of both species were markedly higher at high water levels than at low water levels; furthermore, these were significantly higher on clay than on the other two sediment types at each water level. The C:N and C:P ratios of both species decreased with increasing sediment nutrient supply and water level, whereas N:P decreased in both species with increasing sediment nutrient supply. The aboveground part of C. brevicuspis as well as the aboveground part and whole plant of P. hydropiper were negatively correlated with N:P, which is consistent with the GRH. However, the relationship between the belowground RGR and N:P of these species was inconsistent with GRH. Therefore, the water level and sediment type and their interaction significantly influenced plant RGR and C:N:P characteristics. The RGR and plant stoichiometry differed significantly between plant organs, indicating that the GRH needs refinement when applied to wetland macrophytes.

Automated detection and quantification of COVID-19 pneumonia: CT imaging analysis by a deep learning-based software.

BACKGROUND: The novel coronavirus disease 2019 (COVID-19) is an emerging worldwide threat to public health. While chest computed tomography (CT) plays an indispensable role in its diagnosis, the quantification and localization of lesions cannot be accurately assessed manually. We employed deep learning-based software to aid in detection, localization and quantification of COVID-19 pneumonia. METHODS: A total of 2460 RT-PCR tested SARS-CoV-2-positive patients (1250 men and 1210 women; mean age, 57.7 ± 14.0 years (age range, 11-93 years) were retrospectively identified from Huoshenshan Hospital in Wuhan from February 11 to March 16, 2020. Basic clinical characteristics were reviewed. The uAI Intelligent Assistant Analysis System was used to assess the CT scans. RESULTS: CT scans of 2215 patients (90%) showed multiple lesions of which 36 (1%) and 50 patients (2%) had left and right lung infections, respectively (> 50% of each affected lung's volume), while 27 (1%) had total lung infection (> 50% of the total volume of both lungs). Overall, 298 (12%), 778 (32%) and 1300 (53%) patients exhibited pure ground glass opacities (GGOs), GGOs with sub-solid lesions and GGOs with both sub-solid and solid lesions, respectively. Moreover, 2305 (94%) and 71 (3%) patients presented primarily with GGOs and sub-solid lesions, respectively. Elderly patients (≥ 60 years) were more likely to exhibit sub-solid lesions. The generalized linear mixed model showed that the dorsal segment of the right lower lobe was the favoured site of COVID-19 pneumonia. CONCLUSION: Chest CT combined with analysis by the uAI Intelligent Assistant Analysis System can accurately evaluate pneumonia in COVID-19 patients.

Management of Persistent Air Leaks Using Endobronchial Autologous Blood Patch and Spigot Occlusion: A Multicentre Randomized Controlled Trial in China.

BACKGROUND: Optimal management of persistent air leaks (PALs) in patients with secondary spontaneous pneumothorax (SSP) remains controversial. OBJECTIVE: To evaluate the efficacy and safety of endobronchial autologous blood plus thrombin patch (ABP) and bronchial occlusion using silicone spigots (BOS) in patients with SSP accompanied by alveolar-pleural fistula (APF) and PALs. METHODS: This prospective multicentre randomized controlled trial compared chest tube-attached water-seal drainage (CTD), ABP, and BOS that were performed between February 2015 and June 2017 in one of six tertiary care hospitals in China. Patients diagnosed with APF experiencing PALs (despite 7 days of CTD) and inoperable patients were included. Outcome measures included success rate of pneumothorax resolution at the end of the observation period (further 14 days), duration of air leak stop, lung expansion, hospital stay, and complications. RESULTS: In total, 150 subjects were analysed in three groups (CTD, ABP, BOS) of 50 each. At 14 days, 60, 82, and 84% of CTD, ABP, and BOS subjects, respectively, experienced full resolution of pneumothorax (p = 0.008). All duration outcome measures were significantly better in the ABP and BOS groups than in the CTD group (p < 0.016 for all). The incidence of adverse events, including chest pain, cough, and fever, was not significantly different. All subjects in the ABP and BOS groups experienced temporary haemoptysis. Spigot displacement occurred in 8% of BOS subjects. CONCLUSION: ABP and BOS resulted in clinically meaningful outcomes, including higher success rate, duration of air leak stop, lung expansion, and hospital stay, with an acceptable safety profile.

Crucial sites and environmental variables for wintering migratory waterbird population distributions in the natural wetlands in East Dongting Lake, China.

Dongting Lake is the second largest freshwater lake in China and is one of the globally important wintering sites for migratory waterbirds in the East Asian-Australasian Flyway. Crucial sites and environmental variables for wintering migratory waterbirds are of great concern in the Dongting Lake wetlands. In this research, based on annual (2003/2004-2016/2017) waterbird and habitat census data, we recognized the crucial sites for waterbirds during wintering seasons by comparing the difference of waterbird populations at the community, foraging guild and species levels in different natural wetlands within East Dongting Lake, and then identified the crucial environmental variables affecting waterbird distributions by analyzing the relationship between waterbird populations and the environmental variables, including vegetation area, mudflat area, water area with the depth of 0-20 cm, water area with the depth of 20-50 cm, water area with the depth of 50-100 cm, water area with the depth >100 cm, growth status of vegetation (Min, Mean and Max NDVI), and the human disturbance. Results indicated that five natural wetlands, i.e., Daxiaoxi, Chunfeng, Baihu lakes, Dingzi dyke and Tanjiaweizi, were recognized as the crucial wintering sites for migratory waterbirds in the East Dongting Lake. Among the ten selected environmental variables, water areas with the depth of 0-20 cm, 20-50 cm and >100 cm, human disturbance, Min and Mean NDVIs were identified as the crucial environmental variables overall. Waterbirds at different levels exhibited significant linear relationship with certain environmental variables, with the exception of Bean goose and Lesser White-fronted goose at the species level, which showed Gaussian distribution with changes in mean NDVI. The crucial environmental variables appeared to be foraging guild- and species-specific. These findings provide significant information for managers to understand the differences of wetlands and waterbird populations within East Dongting Lake, and to make more targeted conservation efforts.

Changes of Vegetation Distribution in the East Dongting Lake After the Operation of the Three Gorges Dam, China.

Water regime is regarded as the primary factor influencing the vegetation distribution in natural wetland ecosystems. However, the effect of water regime change induced by large-scale hydraulic engineering on vegetation distribution is still unclear. In this study, multi-temporal TM/ETM+/OLI images and hydrological data from 1995 to 2015 were used to elucidate how the change in water regime influenced the vegetation distribution in the East Dongting Lake (EDTL), especially after the operation of the Three Gorges Dam (TGD) in 2003. Using unsupervised and supervised classification methods, three types of land cover were identified in the study area: Water and Mudflat, Grass, and Reed and Forest. Results showed that the total vegetation area in EDTL increased by approximately 78 km2 during 1995-2015. The areas of Reed and Forest and Grass exhibited a contrasting trend, dramatic increase in Reed and Forest but sharp decrease in Grass, particularly after the operation of TGD. The lowest distribution elevations of Grass and Reed and Forest decreased by 0.61 and 0.52 m, respectively. As a result of water level variation, submergence duration increased at 20-21 m and 28 m elevations (1-13 days), but significantly decreased at 22-27 m and 29-30 m elevations (-3 to -31 days). The submergence duration of Grass and Reed and Forest was 246 and 177 days, respectively. This study indicated that wetland vegetation pattern significantly changed after the operation of TGD, mainly as a result of changes in submergence condition. Submergence duration might be an effective indicator to predict the shift of vegetation distribution in EDTL, and which could provide scientific guidance for vegetation restoration and wetland management in this lake.

Responses to Sedimentation in Ramet Populations of the Clonal Plant Carex brevicuspis.

In aquatic ecosystems, sedimentation is an important factor that affects plant growth, mainly due to sediment depth. Clonal morphological plasticity is an effective strategy in clonal plants for acclimatization to sediment burial. To date, few studies have examined growth responses to sedimentation on the clonal plants at the ramet population level. This study aimed to explore the interactive effects of population size and burial depth on growth and clonal morphology of Carex brevicuspis. Three population sizes (2, 8, and 32 ramets) and 3 burial depths (0 cm, 5 cm, and 10 cm) were used in this experiment. Under shallow (5 cm) and deep (10 cm) burial conditions, biomass accumulation and relative growth rate (RGR) were lower than in the no burial treatment (P < 0.05). RGR of the small and medium populations was especially high compared to the large populations (P < 0.05). Biomass allocation was higher to belowground parts than aboveground parts, except for the small populations in the 5 cm burial treatments. Both shallow burial and smaller populations led to more biomass being allocated to aboveground parts. Deep burial elongated the first order spacer more than shallow burial, and sedimentation had negative effects on the second order spacer length. The number of new ramets did not decrease in the 5 or 10 cm burial treatments compared to the unburial treatment, and larger populations usually had more ramets than smaller ones; the proportion of clumping ramets was higher than the proportion of spreading ramets, and deeper burial and smaller populations led to higher proportions of spreading ramets. These results indicated that the growth of C. brevicuspis was limited by sediment burial at the ramet population level. Smaller populations enable C. brevicuspis to adjust its escape response to burial stress, may allow this species to effectively survive and widely distribute in Dongting Lake wetland.

Differential Strategies to Tolerate Flooding in Polygonum hydropiper Plants Originating From Low- and High-Elevation Habitats.

In species that occur over a wide range of flooding conditions, plant populations may have evolved divergent strategies as a consequence of long-term adaptation to local flooding conditions. In the present study, we investigated the effects of a flooding gradient on the growth and carbohydrate reserves of Polygonum hydropiper plants originating from low- and high-elevation habitats in the Dongting Lake wetlands. The results indicated that shoot length did not differ, whereas the total biomass and carbohydrate reserves were reduced under flooded compared to well-drained conditions for plants originating from both habitat types. However, shoot length, shoot mass, rhizome mass, and total biomass were lower in plants from low-elevation habitats than in those from high-elevation habitats in the flooded condition. Soluble sugar and starch contents in belowground biomass were higher in plants from low-elevation habitats than in those from high-elevation habitats independently of the water level. Therefore, P. hydropiper plants from low-elevation habitats exhibit a lower growth rate and more conservative energy strategy to cope with flooding in comparison with plants from high-elevation habitats. Differential strategies to cope with flooding among P. hydropiper populations are most likely a response to the flooding pressures of the habitat of origin and may potentially drive ecotype differentiation within species along flooding gradients.

Inhibition of litter decomposition of two emergent macrophytes by addition of aromatic plant powder.

Aromatic plants show antimicrobial activity due to their essential oils, but their effect on litter decomposition is unclear. In this study, we evaluated the biomass loss and nutrient dynamics in leaf litters of two macrophytes (Miscanthus sacchariflorus and Carex brevicuspis) with and without addition of powdered material of the aromatic plant Polygonum hydropiper or the non-aromatic plant C. brevicuspis. The two powders had similar basic chemical qualities but P. hydropiperi had a higher essential oils concentration. Leaf litters of M. sacchariflorus and C. brevicuspis were incubated with powdered P. hydropiper or C. brevicuspis (500 g m-3, 250 g m-3, and no addition) for 120 days in a mesocosm experiment. Compared with the control (no addition), P. hydropiperi addition decelerated nutrient release and litter decomposition, while C. brevicuspis addition accelerated those processes. The nitrogen concentrations in both leaf litters and the phosphorus concentration in C. brevicuspis leaf litter were increased by addition of both plant powders. The fungal biomass in both leaf litters decreased after P. hydropiperi addition, due to the antifungal activity of its essential oils. These data indicate that the aromatic plant P. hydropiperi inhibits litter decomposition via its essential oils and that such inhibition is not species-specific.

Impacts of microhabitat changes on wintering waterbird populations.

Caisang Lake, a human-modified wetland, experienced dramatic habitat alterations from the planting of lotus and culturing of crab. Whether the Caisang Lake still maintains populations of wintering waterbirds is of great concern. Here, we compare the changes in waterbird populations before and after habitat alterations in Caisang Lake and assess the driving factors leading to the dramatic changes in waterbird populations. Results indicate that wintering waterbird populations were significantly impacted by altered forage availability, with species- and guild-specific responses. Dramatic habitat alterations from planting lotus caused significant declines in areas of native vegetation, mudflats, and water that may have caused associated declines in herbivores, insectivores, and fish-eating waterbirds, respectively. In contrast, the increased size of the lotus area appears to have led to an increase in omnivorous waterbirds. A food shortage, potentially caused by a large area of Caisang Lake being used for culturing crab, might be another cause of the observed decline in fish-eating waterbirds. This study demonstrates a powerful approach to systematically evaluate waterbird responses to wetland management policies. These findings are important as efforts are made to protect the wintering waterbirds from the effects of human intervention, particularly at other Ramsar wetlands.

[Effects of selenium valence states and application concentrations on plant growth, ascorbate-glutathione cycle in Citrus junos cv. Ziyang Xiangcheng]. / 硒的价态与浓度对香橙幼苗生长和AsA-GSH循环的影响.

Potted Citrus. junos cv. Ziyang Xiangcheng seedlings were used to study the effects of selenium (Se) valence states (Se6+ and Se4+) on plant growth and antioxidants and antixodases in ascorbate(AsA)-glutathione (GSH) cycle. The results showed that Se6+ and Se4+ (from 1.0 mg·L-1 to 8.0 mg·L-1) stimulated the seedling growth by increasing plant height, leaf areas, and fresh or dry mass. Applying Se6+significantly increased plant Se levels mainly in leaf, and applying Se4+ slightly increased Se content mainly in root. Certain valence states and concentrations of Se increased leaf chlorophyll and hydrogen peroxide (H2O2) content. Se6+≤2.0 mg·L-1 treatments enhanced the activates of glutathione reductase (GR) and glutathione peroxidase (GPX), and the contents of GSH and oxidized glutathione (GSSG), while Se6+≥4.0 mg·L-1 treatments reduced the antioxidant contents and antixodase activities of GSH cycle. Moreover, Se4+≤ 2.0 mg·L-1 treatments increased the activities of dehydroascorbate reductase (DHAR) and ascorbate peroxidase (APX), and resulted in higher AsA/[AsA+dehydroascorbic acid (DHA)] ratio. When Se4+≥4.0 mg·L -1, the antioxidant contents and antixodase activities of GSH cycle were increased. Together, this study showed that different valence states and application concentrations of Se showed different influences on AsA-GSH cycle in citrus, and 2.0 mg·L-1 Se6+ and 4.0 mg·L-1 Se4+ were the best concentrations for plant growth.

Consequences of Repeated Defoliation on Belowground Bud Banks of Carex brevicuspis (Cyperaceae) in the Dongting Lake Wetlands, China.

Despite the predominant role of bud banks in the regeneration of clonal macrophyte populations, few studies have examined the way in which clonal macrophytes adjust the demographic features of bud banks to regulate population dynamics in response to defoliation in wetlands. We investigated the density and composition of bud banks under repeated defoliation in the wetland sedge Carex brevicuspis C. B. Clarke in the Dongting Lake wetlands, China. The density and biomass of rhizome buds and shoots did not decrease significantly in response to repeated defoliation over two consecutive years. The composition of bud banks, which consisted of long and short rhizome buds, also did not change significantly in response to repeated defoliation. Nevertheless, the ramet height and the shoot, root, and rhizome mass of C. brevicuspis declined significantly under repeated defoliation. Our findings suggest that bud banks are a conservative reproductive strategy that enables C. brevicuspis to tolerate a certain amount of defoliation. The maintenance of large bud banks after repeated defoliation may enable C. brevicuspis populations to regenerate and persist in disturbed habitats. However, bud bank density of C. brevicuspis might decline in the long term because the amount of carbon stored in rhizome buds and plants is reduced by frequent defoliation.