Projecting the response of ecological risk to land use/land cover change in ecologically fragile regions.

Anthropogenic activities have dramatically altered land use/land cover (LULC), leading to ecosystem service (ES) degradation and further ecological risks. Ecological risks are particularly serious in ecologically fragile regions because trade-offs between economic development and ecological protection are prominent. Thus, ways in which to assess the response of ecological risks to LULC change under each development scenario in ecologically fragile regions remain challenging. In this study, future LUCC and its impact on ESs under four development scenarios in 2040 in western Jilin Province were predicted using a patch-generating land use simulation model and the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model. Ecological risk was assessed based on future LUCC possibilities, and potential ES degradation and potential drivers of ecological risks were explored using a geographic detector. The results showed that the cropland development scenario (CDS) would experience large-scale urbanization and cropland expansion. Carbon storage (CS), habitat quality (HQ), and water purification (WP) degraded the most under the CDS, and grain yield (GY) and water yield (WY) degraded the most under the ecological protection scenario (EPS). The LUCC probability under the CDS (14.37 %) was the highest, while the LUCC probability under the comprehensive development scenario (CPDS) (8.68 %) was the lowest. The risk of WP degradation was greatest under the CDS, but the risk of soil retention (SR) degradation was greatest under the natural development scenario (NDS), EPS, and CPDS. Ecological risk coverage was the largest (98.04 %), and ecological risks were the highest (0.21) under the CDS, while those under the EPS were the opposite. Distance to roads and population density had a higher impact on ecological risks than other drivers. Further attention should be given to the ecological networks and pattern establishment in urbanized regions. This study will contribute to risk prevention and sustainable urban and agricultural development.

Forest swamp succession alters organic carbon composition and survival strategies of soil microbial communities.

Forest swamp ecosystems plays crucial role in the global carbon cycle. However, the effects of forest swamp succession on soil organic matter (SOM) and microbial community structure remain unclear. To determine the drivers of SOM change and soil microbial communities in forest swamp succession, a 'space instead of time' approach was used. Soil samples from 0 to 40 cm were collected along forest swamp (early stage), dried-up forest swamp (middle stage), and forest (late stage) ecosystems. Our findings reveal that as succession progresses, the relative content of aromatics decreases and SOM undergoes a transition towards a more readily degradable form. These changes affect soil carbon sequestration and nutrient availability. Bacterial diversity was significantly influenced by succession and changes in soil depth, with fungi exhibiting higher resilience. Soil properties and environmental conditions exert influence over the structure and function of microorganisms. As succession occurred, microbial interactions shifted from cooperation to competition, with bacteria displaying a deterministic distribution pattern and fungi exhibiting a random distribution pattern. SOM quality plays a key role in shaping microbial communities and influencing their growth strategies. Microorganisms are the major drivers of soil respiration, with K-strategist dominated communities in early succession exhibiting slower degradation rates, whereas r-strategists dominated in later stages, leading to faster decomposition.

Interactions between phenanthrene and polystyrene micro/nano plastics: Implications for rice (Oryza sativa L.) toxicity.

Micro/nano plastics (MPs/NPs) are widely distributed and are one of the global pollutants of current concern. Micro/nano plastics can adsorb a variety of persistent organic pollutants, and different particle sizes and surface charges affect the biological effects of MPs/NPs. Therefore, how the compound pollution of MPs/NPs with different particle sizes and organic pollutants produces toxic effects on plants needs to be further studied. We investigated the toxic effects of phenanthrene (Phe) and amino-modified PS (PS-NH2) with two particle sizes (50 nm, 5 µm) on rice. The stress mechanism of PS-NH2 was different between the two particle sizes. Moreover, 50 nm PS-NH2 inhibited stomatal conductance and transpiration rate, reduced photosynthetic rate, significantly enriched GO functions such as "DNA repair" and "DNA double-strand break," and caused severe DNA damage in rice. Notably, 5 µm PS-NH2 affected the gene expression of "photosynthetic lighting" and "photosynthetic antenna protein" in rice, decreased chlorophyll content, and inhibited rice growth. The toxicity of 50 nm PS-NH2 was stronger. In addition, we found that Phe reduced the toxicity of PS-NH2 with different particle sizes, and the relief effect of 50 nm PS-NH2+Phe was more evident. Further, 50 nm PS-NH2+Phe alleviated the toxicity by stimulating the activities of antioxidant enzymes, reducing oxidative damage to chloroplasts, and inhibiting photosynthesis. However, 5 µm PS-NH2+Phe can reduce the stress by reducing the degree of membrane lipid peroxidation, activating metabolic pathways related to the cell wall and cell membrane formation, and plant antitoxin biosynthesis. The results contribute to the understanding of the mechanism of toxicity of MPs/NPs and polycyclic aromatic hydrocarbons (PAHs) to crops.

Water quality pollution assessment and source apportionment of lake wetlands: A case study of Xianghai Lake in the Northeast China Plain.

Surface water pollution has always posed a serious challenge to water quality management. Improving water quality management requires figuring out how to comprehend water quality conditions scientifically and effectively as well as quantitatively identify regional pollution sources. In this study, Xianghai Lake, a typical lake-type wetland on the Northeast China Plain, was taken as the research area. Based on a geographic information system (GIS) method and 11 water quality parameters, the single-factor evaluation and comprehensive water quality index (WQI) methods were used to comprehensively evaluate the water quality of the lake-type wetland in the level period. Four key water quality parameters were determined by the principal component analysis (PCA) method, and more convenient comprehensive water quality evaluation models, the minimum WQI considering weights (WQImin-w) and the minimum WQI without considering weights (WQImin-nw) were established. The multiple statistical method and the absolute principal component score-multiple liner regression (APCS-MLR) model were combined to analyse the lake pollution sources based on the spatial changes in pollutants. The findings demonstrated that the WQImin-nw model's water quality evaluation outcome was more accurate when weights were not taken into account. The WQImin-nw model can be used as a simple and convenient way to comprehend the variations in water quality in wetlands of lakes and reservoirs. It was concluded that the comprehensive water quality in the study area was at a "medium" level, and CODMn was the main limiting factor. Nonpoint source pollution (such as agricultural planting and livestock breeding) was the most important factor affecting the water quality of Xianghai Lake (with a comprehensive contribution rate of 31.65%). The comprehensive contribution rates of sediment endogenous and geological sources, phytoplankton and other plants, and water diversion and other hydrodynamic impacts accounted for 25.12%, 19.65%, and 23.58% of the total impact, respectively. This study can provide a scientific method for water quality assessment and management of lake wetlands, and an effective support for migration of migratory birds, habitat protection and grain production security.

Molecular mechanisms of toxicity and detoxification in rice (Oryza sativa L.) exposed to polystyrene nanoplastics.

Nanoplastics (NPs) are an emerging threat to higher plants in terrestrial ecosystems. However, the molecular of NP-related phytotoxicity remains unclear. In the present study, rice seedlings were exposed to polystyrene (PS, 50 nm) NPs at 0, 50, 100, and 200 mg/L under hydroponic conditions to investigate the induced physiological indices and transcriptional mechanisms. We found that 50, 100, and 200 mg/L PS significantly reduced root (53.05%, 49.61%, and 57.58%, respectively) and shoot (54.63%, 61.56%, and 62.64%, respectively) biomass as compared with the control seedlings. The activities of antioxidant enzymes, including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and ascorbate peroxidase (APX), were significantly activated in all PS treatment groups, indicating that PS inhibited plant growth and induced oxidative stress. Transcriptome analyses showed that PS modulated the expression of the genes involved in cell detoxification, active oxygen metabolism, mitogen-activated protein kinase (MAPK), and plant hormone transduction pathways. Our study provides new insights into phytotoxicity by demonstrating the potential underlying toxicity of PS NPs in higher plants.

Toxicological effects and transcriptome mechanisms of rice (Oryza sativa L.) under stress of quinclorac and polystyrene nanoplastics.

The absorption and accumulation of nanoplastics (NPs) by plants is currently attracting considerable attention. NPs also tend to adsorb surrounding organic pollutants, such as pesticides, which can damage plants. However, molecular mechanisms underlying the phytotoxicity of NPs are not sufficiently researched. Therefore, we analyzed the toxicological effects of 50 mg/L polystyrene NPs (PS 50 nm) and 5 mg/L the herbicide quinolinic (QNC) on rice (Oryza sativa L.) using 7-day hydroponic experiments, explaining the corresponding mechanisms by transcriptome analysis. The main conclusion is that all treatments inhibit rice growth and activate the antioxidant level. Compared with CK, the inhibition rates of PS, QNC, and PS+QNC on rice shoot length were 3.95%, 6.68%, and 11.43%, respectively. The gene ontology (GO) term photosynthesis was significantly enriched by QNC, and the combination PS+QNC significantly enriched the GO terms of amino sugar and nucleotide sugar metabolisms. The chemicals QNC and PS+QNC significantly affected the Kyoto Encyclopedia of Genes and Genomes (KEGG) of the MAPK signaling pathway, plant hormone signal transduction, and plant-pathogen interaction. Our findings provide a new understanding of the phytotoxic mechanisms and environmental impacts of the interactions between NPs and pesticides. It also provides insights into the impact of NPs and pesticides on plants in the agricultural system.

Response of vegetation variation to climate change and human activities in semi-arid swamps.

Vegetation is a sensitive factor in marsh ecosystems, which can provide nesting sites, foraging areas, and hiding places for waterfowl and can affect their survival environment. The Jilin Momoge National Nature Reserve, which consists of large areas of marshes, is located in the semi-arid region of northeast China and is an important stopover site for the critically endangered species of the Siberian Crane (Grus leucogeranus). Global climate change, extreme droughts and floods, and large differences in evaporation and precipitation in this region can cause rapid vegetation succession. In recent years, increased grain production and river-lake connectivity projects carried out in this area to increase grain outputs and restore wetlands have caused significant changes in the hydrological and landscape patterns. Therefore, research on the response of variation trends in vegetation patterns to the main driving factors (climate change and human activities) is critical for the conservation of the Siberian Crane. Based on the Google Earth Engine (GEE) platform, we obtained and processed the Normalized difference vegetation index (NDVI) data of the study area during the peak summer vegetation period for each year from 1984 to 2020, estimated the annual vegetation cover using Maximum value composites (MVC) method and the image dichotomy method, calculated and analyzed the spatial and temporal trends of vegetation cover, explored the response of vegetation cover change in terms of climate change and human activities, and quantified the relative contribution of both. The results revealed that first, from the spatial and temporal changes, the average annual growth rate of regional vegetation was 0.002/a, and 71.14% of the study area was improved. The vegetation cover showed a trend of degradation and then recovery, in which the percentage of high vegetation cover area decreased from 51.22% (1984-2000) to 28.33% (2001-2005), and then recovered to 55.69% (2006-2020). Second, among climate change factors, precipitation was more correlated with the growth of vegetation in the study area than temperature, and the increase in precipitation during the growing season could promote the growth of marsh vegetation in the Momoge Reserve. Third, overall, human activities have contributed to the improvement of vegetation cover in the study area with the implementation of important ecological projects, such as the return of farmland to wetlands, the return of grazing to grass, and the connection of rivers and lakes. Fourth, climate change and human activities jointly drive vegetation change, but the contribution of human activities in both vegetation improvement and degradation areas (85.68% and 78.29%, respectively) is higher than that of climate change (14.32% and 21.71%, respectively), which is the main reason for vegetation improvement or degradation in the study area. The analysis of vegetation pattern change within an intensive time series in semi-arid regions can provide a reference and basis for studying the driving factors in regions with rapid changes in vegetation and hydrological conditions.

Integration of MFC reduces CH4, N2O and NH3 emissions in batch-fed wetland systems.

The combination of microbial fuel cells (MFCs) with constructed wetlands (CWs) for enhancing water purification efficiency and generating bioelectricity has attracted extensive attention. However, the other benefits of MFC-CWs are seldom reported, especially the potential for controlling gaseous emissions. In this study, we have quantitatively compared the pollutant removal efficiency and the emission of multiple gases between MFC-CWs and batch-fed wetland systems (BF CWs). MFC-CWs exhibited significantly (p < 0.01) higher COD, NH4+-N, TN, and TP removal efficiencies and significantly (p < 0.01) lower global warming potential (GWP) than BF CWs. The integration of MFC decreased GWP by 23.88% due to the reduction of CH4 and N2O fluxes, whereas the CO2 fluxes were slightly promoted. The quantitative PCR results indicate that the reduced N2O fluxes in MFC-CWs were driven by the reduced transcription of the nosZ gene and enhanced the ratio of nosZ/(nirS + nirK); the reduced CH4 fluxes were related to pomA and mcrA. Additionally, the NH3 fluxes were reduced by 52.20% in MFC-CWs compared to BF CWs. The integration of MFC promoted the diversity of microbial community, especially Anaerolineaceae, Saprospiraceae and Clostridiacea. This study highlights a further benefit of MFC-CWs and provides a new strategy for simultaneously removing pollutants and abating multiple gas emissions in BF CWs.

Effects of individual and combined polystyrene nanoplastics and phenanthrene on the enzymology, physiology, and transcriptome parameters of rice (Oryza sativa L.).

Owing to their wide distribution, easy production, and resistance to degradation, microplastics (MPs) represent a globally emerging group of pollutants of concern. Furthermore, their decomposition can result in the generation of nanoplastics (NPs), which cause further environmental issues. Currently, the impact of the combination of these plastics with other organic pollutants on crop growth remains poorly investigated. In this study, a hydroponic experiment was conducted for seven days to evaluate the effects of 50 nm, 50 mg/L polystyrene (PS), and 1 mg/L phenanthrene (Phe) on the growth of rice plants. The results revealed that both Phe and PS inhibited growth and improved the antioxidant potential of rice. Relative to Phe alone, exposure to a combination of PS and Phe reduced Phe accumulation in the roots and shoots by 67.73% and 36.84%, respectively, and decreased the pressure on the antioxidant system. Exposure to Phe alone destroyed the photosynthetic system of rice plant leaves, whereas a combination of PS and Phe alleviated this damage. Gene Ontology (GO) analysis of the rice transcriptomes revealed that detoxification genes and phenylalanine metabolism were suppressed under exposure to Phe, which consequently diminished the antioxidant capacity and polysaccharide synthesis in rice plants. Kyoto Encyclopaedia of Genes and Genomes (KEGG) transcriptome analysis revealed that the combined presence of both PS and Phe improved photosynthesis and energy metabolism and alleviated the toxic effects of Phe by altering the carbon fixation pathway and hormone signal transduction in rice plants. The combination of PS and Phe also prevented Phe-associated damage to rice growth. These findings improve our understanding of the effects of MP/NPs and polycyclic aromatic hydrocarbons on crops.

Effects of polystyrene nanoplastics with different functional groups on rice (Oryza sativa L.) seedlings: Combined transcriptome, enzymology, and physiology.

Plastic particles originate from the daily use of plastics and have become a new form of pollutant. However, the effects of nanoplastics (NPs) on higher plants remain largely unclear, thus requiring further research. In this study, rice plants were exposed to polystyrene (PS) NPs with different functional groups to determine their toxicity. The presence of NPs reduced the biomass and photosynthetic capacity of rice. Compared with control (CK), the heights of rice plants exposed to no-modified PS, carboxyl-modified PS (PS-COOH) and amino-modified PS (PS-NH2) groups decreased by 13.59%, 26.61%, and 42.71%, while the dry shoot weight decreased by 47.46%, 50.09%, and 71.04%, respectively. All treatments activated the antioxidant levels of rice and reduced photosynthesis. Transcriptome analysis showed that NPs induced the expression of genes related to antioxidant enzyme activity in rice roots. Rice could partially reduce the xenobiotic toxicity caused by external sources by regulating phenylpropane biosynthesis and the processes involved in cell detoxification. PS mainly affected the process of RNA metabolism, while PS-COOH mainly affected ion transport, and PS-NH2 mainly affected the synthesis of macromolecular protein, which had different effects on rice growth.

Shift in nitrogen transformation in peatland soil by nitrogen inputs.

Inputs of nitrogen (N) to peatlands in the form of fertilizers have rapidly increased due to the intensification of agricultural systems, impacting ecological processes, and the carbon storage function of peatland. However, detailed information on the impacts of long-term N inputs on the individual steps of N transformation processes in peatland soils still needs to be fully understood. We investigated N mineralization and nitrification rates as well as nitrite dependent anaerobic methane oxidation (n-damo), anaerobic ammonium oxidation (anammox), denitrification, and dissimilatory nitrate reduction to ammonium (DNRA) in a peatland affected by N inputs for >50 years, using isotope tracing technique and quantitative PCR. Based on the results, N inputs increased N mineralization and nitrification rates by 77 and 43%, respectively. Notably, the contributions of n-damo and anammox to N2 production were enhanced by 242 and 170%, accounting for 30 and 12%, respectively. The contributions of denitrification and DNRA to N2 production decreased by 27 and 52%, accounting for 48 and 10% of N2 production, respectively. Nitrifier abundance increased significantly, with AOA being the dominant prokaryote (from 696 to 1090 copies g-1), but AOB responded more strongly to N inputs (from 5 to 68 copies g-1). The N inputs also promoted the growth of n-damo and anammox bacteria, whose abundances increased by 3.7% (from 565 to 586 copies g-1) and 85.7% (from 305 to 567 copies g-1), respectively, while denitrifier abundance was significantly reduced, with nirK and nirS abundances decreasing by 58% (from 738 to 308 copies g-1) and 50% (from 218 to 109 copies g-1), respectively. Soil pH was the key environmental factor influencing N transformations. We show that n-damo plays important roles in N cycling in peatland subjected to N inputs, providing a scientific basis for improved peatland management.

Author Correction: Snow depths' impact on soil microbial activities and carbon dioxide fluxes from a temperate wetland in Northeast China.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Snow depths' impact on soil microbial activities and carbon dioxide fluxes from a temperate wetland in Northeast China.

Snow depth may have a complex influence on carbon cycling in winter. Here we set up a field experiment to investigate how different snow depths (0 cm, 60 cm, 90 cm) influenced carbon dioxide (CO2) in a wetland. The mean ± standard error of CO2 emissions under snow addition treatments (60 cm and 90 cm snow depths) were 0.92 ± 0.16 g·cm-2·s-1 and 0.53 ± 0.16 g·cm-2·s-1, respectively, compared with snow removal treatment (0 cm snow depth), 0.11 ± 0.05 g·cm-2·s-1. In general, snow addition increased CO2 fluxes significantly. As snow depths increased, microbial biomass carbon (MBC) and bacterial diversities increased drastically. More important, the community of bacteria differed under different treatments. Firmicutes, which can resist dehydration and extremely low temperatures, was widely distributed in the snow removal treatment, where it sustained soil biochemical processes. Overall, our study indicates that snow cover counteracts the negative effects on soil microbial activities caused by low temperatures and could play a critical role in winter carbon cycling in wetlands.

Enhancing Cd(II) sorption by red mud with heat treatment: Performance and mechanisms of sorption.

Red mud is a waste generated from the aluminum industry in large quantities. The potential of red mud as a sorbent for beneficial reuse has been the focus of research efforts. However, the limited sorption capacity of red mud has hindered its applications in the removal of environmental pollutants. In this study, the feasibility of heat treatment in improving the sorption of toxic Cd(II) by red mud was investigated in the temperature range of 200-900 °C. Heat treatment at 500 °C resulted in the highest sorption capacity (42.64 mg g-1) and the fastest sorption rate. Further analyses revealed that heat treatment at 500 °C led to significant increases in specific surface area (32.77 m2 g-1), which likely contributed to the enhanced Cd(II) sorption performance. Notably, heat treatment at 500 °C nearly doubled Cd(II) sorption stability as compared with that of raw red mud, as demonstrated by leaching experiments with simulated rainwater. Sequential extraction and XPS analyses indicated that specific sorption was the predominant mechanism involved in Cd(II) removal by red mud heat-treated at 500 °C (RM500). The strength of specific sorption following heat treatment likely contributed to the increase in sorption stability due to the formation of inner-sphere complex (-OCdOH). Metal-metal ion exchange was identified as another sorption mechanism, which, however, likely had only a limited effect on Cd(II) sorption performance. As the final pH (6.57) of the sorption system was typically lower than the pHPZC (about 10.6) of RM500, positive charges would develop on the red mud surface and impede the retention of Cd(II) cations, resulting in weak electrostatic attraction between Cd(II) cations and red mud. In summary, heat treatment at 500 °C considerably enhanced the capacity, rate and stability of Cd(II) sorption by red mud, suggesting red mud could be optimized by heat treatment as a more effective sorbent for Cd(II) removal. These findings represent the first mechanistic characterization of Cd(II) sorption by heat-treated red mud, providing much needed insights into the potential strategies to enhance the effectiveness of red mud in the sorptive removal of toxic heavy metals.

Characteristics of Cadmium Sorption by Heat-Activated Red Mud in Aqueous Solution.

Red mud as a waste material is produced in large quantities by the aluminum industry. Heat activation has been used to enhance sorption capacity of red mud for its beneficial reuse as an effective sorbent. In this study, heat-activated red mud (HARM) was investigated for its Cd(II) sorption capacity under various process conditions (Cd concentration, pH and contact time) using response surface methodology (RSM). Analysis with RSM identified pH as the most important process parameter. The positive correlation between higher pH and greater Cd(II) sorption was likely due to: (i) decreased proton competition with Cd(II) for sorption sites at higher pH; (ii) enhanced sorption via ion exchange by monovalent Cd species from hydrolysis at higher pH; and (iii) improved thermodynamics of sorption at higher pH as protons are being released as products. Further analysis indicated the sorption process was thermodynamically favorable with a negative change in Gibbs free energy. Additionally, the sorption process exhibited a positive change in enthalpy, indicative of endothermic nature of sorption; this is consistent with sorption increase at higher temperature. These findings provide needed insight into the mechanisms underlying Cd(II) sorption by HARM for more effective applications of heat-activated red mud as sorbents for Cd(II) removal.

Effect of planting and fertilization on lead partitioning in dredged sediment.

Dredging has been practiced to remove sediment impacted by persistent contaminants, such as heavy metals. Of these metals, lead (Pb) is of particular concern due to its toxicity. Therefore, dredged sediment containing Pb requires further mitigation. One method for Pb mitigation is phytoremediation of dredged sediment. In this study, the partitioning of Pb in sediment during phytoremediation by willow (Salix integra) was assessed. The results showed that, in general, the bioavailable forms of Pb declined with increased application of the standard Hoagland nutrient solution, which appeared to enhance the Fe-Mn oxide fraction and residual inert fraction. In contrast, the addition of excess phosphorus decreased the bioavailable fractions of Pb. However, the bioavailable fractions of Pb increased with additional potassium addition. Planting Salix integra was shown to promote the stabilization of Pb in sediment and led to a transformation from bioavailable forms to non-bioavailable forms. The results suggest that planting Salix integra can remediate Pb-contaminated dredged sediment via Pb immobilization by the roots. During this process, the application of Hoagland nutrient solution and the application of nutrient solutions with excess phosphorus not only promote root growth of Salix integra which would reduce Pb bioavailability, but also further enhance the immobilization of Pb in contaminated sediment, likely through the formation of Pb-containing compounds with low bioavailability.

Slow stamen movement in a perennial herb decreases male-male and male-female interference.

Approximately 80 % of angiosperm species produce hermaphroditic flowers, which face the problem of male-male sexual interference (one or more anthers gets in the way of disseminating pollen from other anthers) or male-female sexual interference (the pistil interferes with disseminating pollen from the anthers by preventing the anther from touching a pollinator, or the anther prevents pollinator from depositing outcross pollen on the stigma). Slow stamen movement in hermaphrodite flowers has been interpreted as an adaptation for reducing male-male sexual interference. Using slow stamen movement in Lychnis cognata (Caryophyllaceae), this study presents new evidence that this phenomenon can reduce both male-male and male-female sexual interference. Ten stamens in L. cognata flowers vertically elongated their filaments in two batches and displayed similar patterns in pollen dispensing. More importantly, 10 stamens bend out of the floral centre by curving the filament also in 2 batches and pollen grains located at the flower centre displayed the highest viability. Thus, three stages of stamen movement can be identified, comprising two male stages (M1 and M2) and one female stage (F). We found that the main pollinator for L. cognata, Bhutanitis yulongensis (Papilionodae) generally preferred M1 flowers. Manipulation experiments show that vertical stamen movement enabled the anthers to dehisce at different times to prolong the presentation of pollen grains. Horizontal movement of the stamen decreased both male-male and male-female interference. However, vertical stamen movement had a minor role in increasing amount of pollen received by the stigma. This study provides the first direct experimental evidence of concurrent male-male and male-female interference in a flower. We suggest that the selection pressure to reduce such interference might be a strong force in floral evolution. We also propose that other selective pressure, including pollen dispensing mechanisms, pollen longevity, pollinator behaviour and weather, might contribute to floral evolution.

Using 13C isotopes to explore denitrification-dependent anaerobic methane oxidation in a paddy-peatland.

Peatlands are organic-matter-rich but nitrogen-limited natural systems, the carbon/nitrogen (C/N) status of which are subject to increasing exposure from long-term nitrate (NO3-) fertilizer inputs and atmospheric nitrogen (N) deposits. To manage and protect these unique environments, an improved understanding of denitrification-dependent anaerobic oxidation of methane (DAMO) in peatlands is needed. In this study, we used stable isotope measurements and incubation with NO3- additions to facilitate an investigation and comparison of the potential DAMO rates in a paddy-peatland that has been influenced by N fertilizer over 40 years and an undisturbed peatland in northeast China. Monitoring of 13CO2 production confimed DAMO did occur in both the paddy-peatland and the undisturbed peatland, the rates of which increased with NO3- additions, but decreased logarithmically with time. When NO3- was added, there were no significant differences between the CH4 oxidation in the paddy-peatland and peatland samples after 36 hours of incubation (97.08 vs. 143.69 nmol g-1 dry peat) and the potential DAMO rate after incubation for 1 hour (92.53 vs. 69.99 nmol g-1 h-1). These results indicate that the occurrence of DAMO in peatlands might be controlled by the amount of NO3- applied and the depth to which it penetrates into the anoxic layer.

The Spatial Distribution of Nitrogen Removal Functional Genes in Multimedia Constructed Wetlands for Wastewater Treatment.

The real-time polymerase chain reaction was used to quantitatively evaluate distribution patterns and nitrogen removal pathways of the amoA, nxrA, narG, napA, nirK, qnorB, nosZ, nas, and nifH genes and 16S rRNA in anaerobic ammonia oxidation bacteria in four multimedia constructed wetlands for rural wastewater treatment. The results indicated that the abundance of functional genes for nitrogen removal in the rhizosphere layer (0 to 30 cm), water distribution layer (30 to 50 cm), multime filler layer (50 to 130 cm), and catchment layer (130 to 170 cm) of the constructed wetlands were closely related. The rhizosphere layer was conducive to the absolute enrichment of dominant genes. The other three layers were favorable to the relative enrichment of rare genes.

Towards multi-level biomonitoring of nematodes to assess risk of nitrogen and phosphorus pollution in Jinchuan Wetland of Northeast China.

Cultivation for agricultural production often poses threats to nearby wetlands ecosystems in fertile landscapes. In this study, nematode ecological indexes were assessed through the main soil properties of the wetlands, farmlands, and edges of wetlands and farmlands in Jinchuan Wetland by the random sampling. Behavior and reproduction in Caenorhabditis elegans (C. elegans) exposed to the sampled waters were also examined. Stress proteins Hsp70 and Hsp90 were measured both in the living field samples of C. elegans and the lab-tested C. elegans. Our results suggested that disturbance to wetland ecosystems by nitrogen and phosphorus reduced nematode richness and proportions of bacterivore nematodes. Bacterivore nematode diversity and plant-parasitic ecological index were proven to be sensitive indicators of the ecological health of wetlands. Nematode Hsp70 were useful biosensors to monitor and assess the levels of nitrogen and phosphorus pollutions in wetlands. Furthermore, multi-level soil faunal assessments by canonical correspondence analysis showed that Jinchuan Wetland is threatened with non-point source pollution from nearby farmlands.