Wetland Ecosystems In China Research Articles

Key processes of carbon cycle and sink enhancement paths in natural wetland ecosystems in China

Key processes of carbon cycle and sink enhancement paths in natural wetland ecosystems in China

Seasonal covariations of diet-gut microbiota in the adaptation of the newly reintroduced Père David's deer (Elaphurus davidianus) to the northern habitat

Milu (Père David's deer, Elaphurus davidianus), once extinct in the wild, was one of the few indigenous large herbivores of the wetland ecosystem in China. The reintroduction of milu in northern China has just started and is expected to restore not only that species, but also the ecosystem. To acquire insights into the adaptive process of the milu population first rewilded in the northern habitat and provide knowledge for the on-going and future reintroduction attempts, we used DNA metabarcoding to analyze the diets and gut microbiota of those milu in the first year after releasing. The results showed strong seasonality in both diet and gut microbiota. Significant higher dietary diversity was detected in in autumn than summer and winter. Woody dietary components increased continuously from summer to winter. A significant correspondence was found between the dietary and microbial diversities. Enrichment of metabolic pathways involved in lipid and amino acid metabolism was identified in summer, and of those involved in carbohydrate and glycan metabolism was identified in winter. Pathways related to metabolism of certain amino acid were differently abundant in the breeding season. The study indicated the contribution of foraging and gut microbial seasonality to the overwintering, reproduction and environmental adaption of the reintroduced milu. The enrichment of opportunistic pathogen Treponema and lower microbial diversity indicated higher health risk in winter, and thus disease prevention measures were suggested. Pre- and post-release food evaluation and monitoring was recommended to ensure food sufficiency in the reintroductions.

Biophysical warming patterns of an open-top chamber and its short-term influence on a Phragmites wetland ecosystem in China

Passive-warming, open-top chambers (OTCs) are widely applied for studying the effects of future climate warming on coastal wetlands. In this study, a set of six OTCs were established at a Phragmites wetland located in the Yellow River Delta of Dongying City, China. With data collected through online transmission and in-situ sensors, the attributes and patterns of realized OTCs warming are demonstrated. The authors also quantified the preliminary influence of experimental chamber warming on plant traits. OTCs produced an elevated average air temperature of 0.8°C (relative to controls) during the growing season (June to October) of 2018, and soil temperatures actually decreased by 0.54°C at a depth of 5 cm and 0.46°C at a depth of 30 cm in the OTCs. Variations in diel patterns of warming depend greatly on the heat sources of incoming radiation in the daytime versus soil heat flux at night. Warming effects were often larger during instantaneous analyses and influenced OTCs air temperatures from −2.5°C to 8.3°C dependent on various meteorological conditions at any given time, ranging from cooling influences from vertical heat exchange and vegetation to radiation-associated warming. Night-time temperature depressions in the OTCs were due to the low turbulence inside OTCs and changes in surface soil-atmosphere heat transfer. Plant shoot density, basal diameter, and biomass of Phragmites decreased by 23.2%, 6.3%, and 34.0%, respectively, under experimental warming versus controls, and plant height increased by 4.3%, reflecting less carbon allocation to stem structures as plants in the OTCs experienced simultaneous wind buffering. While these passive-warming OTCs created the desired warming effects both to the atmosphere and soils, pest damages on the plant leaves and lodging within the OTCs were extensive and serious, creating the need to consider control options for these chambers and the replicated OTCs studies underway in other Chinese Phragmites marshes (Panjin and Yancheng).©2023 China Geology Editorial Office.

Hands-off, artificial construction, or penalty? How to deal with the increasingly polluted coastal wetland ecosystem in China

As the destruction of coastal wetlands in China becomes more and more serious, the government needs to strengthen the management of the wetland ecosystem. Considering that pollution is an important factor in the destruction of coastal wetlands in China, the government can deal with the problem of wetland pollution through three modes: hands-off, artificial construction, and penalty. In this article, the differential game model is constructed under these three modes. The balanced social benefits of the government and polluting enterprises under the three modes are obtained, and the applicable conditions of various wetland treatment paths are compared. The results show that when the revenue generated by taxation and the indirect income generated by artificial construction are small, the government will choose the laissez-faire mode. However, with the gradual increase of indirect income generated by artificial construction, the government will be inclined to choose the artificial construction mode. When the income from government fines is small, the social benefits of polluters in the hands-off mode are greater than those in the penalty mode. With the increase of fines, the social benefits of polluting enterprises will first decrease and then increase, which will eventually be greater than the social benefits under the hands-off mode.

Greenhouse gas emissions and environmental drivers in different natural wetland regions of China

Wetlands sequestrate carbon at the highest rate than any other ecosystems on Earth. However, the spatial and temporal dynamics of GHGs emissions from the wetland ecosystems in China are still elusive. We synthesized 166 publications that contain 462 in situ measurements of GHGs emissions from the natural wetlands in China, and further analyzed the variability and the drivers of GHGs emissions in eight subdivisions of China's wetlands. The results show that the current studies are mainly concentrated in the estuaries, Sanjiang Plain, and Zoige wetlands. The average CO2 emissions, CH4 fluxes and N2O fluxes from Chinese wetlands were 218.84 mg·m−2·h−1, 1.95 mg·m−2·h−1 and 5.8 × 10−2 mg·m−2·h−1, respectively. The global warming potential (GWP) of China's wetlands was estimated to be 1881.36 TgCO2-eq·yr−1, with CO2 emissions contributing more than 65% to the GWP value. The combined GWP values of Qinghai-Tibet Plateau wetlands, coastal wetlands and northeastern wetlands account for 84.8% of GWP of China's wetlands. Correlation analysis showed that CO2 emissions increased with the increasing mean annual temperature, elevation, annual rainfall, and wetland water level, but decreased with soil pH. CH4 fluxes increased with the mean annual temperature and soil water content but decreased with the redox potential. This study analyzed the drivers of GHGs emissions from wetland ecosystems at the national scale, and GWP values of eight wetland subregions of China were comprehensively assessed. Our results are potentially useful for the global GHGs inventory, and can help assess the response of GHGs emissions of wetland ecosystem to environmental and climate change.

High-Resolution Mapping Changes in the Invasion of Spartina Alterniflora in the Yellow River Delta

The propagation of the invasive <i>Spartina alterniflora</i> (<i>S. alterniflora</i>) has seriously affected the health of coastal wetland ecosystems in China and thus requires an urgent response. In this research, we construct a feature vector set containing phenological and other time-series features based on the Google Earth Engine (GEE) platform by combining dense time-series images from the Sentinel-1 and Sentinel-2 satellites. We obtained the dataset of the annual distribution of <i>S. alterniflora</i> in the Yellow River Delta (YRD) from 2016 to 2021 by developing an object-oriented random forest classification model. The results show that <i>S. alterniflora</i> has different phenological features from other wetland plants that played an important role in its classification based on the images. A combination of multiple phenological and temporal features improved the classification accuracy of <i>S. alterniflora</i> (multi-year average OA: 95.38&#x0025;; UA: 95.01&#x0025;; PA: 95.17&#x0025;). Our results suggest that from 2016 to 2021, the growth rate of the area occupied by <i>S. alterniflora</i> was 2.17 km² per year, and a new patch of the <i>S. alterniflora</i> appeared in the south of the study area in 2018. The work here provides scientific data to support the monitoring and control of the invasive <i>S. alterniflora</i> at a large scale.

Effects of Imazapyr on Spartina alterniflora and Soil Bacterial Communities in a Mangrove Wetland

The invasion of Spartina alterniflora (S. alterniflora) has caused serious damage to coastal wetland ecosystems in China, especially the mangrove wetlands in South China. This study aimed to validate the effect of imazapyr on S. alterniflora and soil. The controlled experiment was conducted in May 2021 at the Zhangjiangkou Mangrove Wetland Reserve. In the experiment, 25% (W) imazapyr was used, and six treatments were set up: 3035, 6070, and 9105 mL/acre 25% imazapyr and 1299, 2604, and 5202 mL/acre of AGE 809 + 6070 mL/acre 25% imazapyr. The results showed no side effects on mangrove plants in the spraying area. The highest control efficiency (95.9%) was given by 2604 mL/acre of AGE 809 + 6070 mL/acre 25% imazapyr. The residues of imazapyr in different soils were reduced to 0.10–0.59 mg/kg. The sequencing results showed no significant difference in the overall bacterial communities under different treatments (p &gt; 0.05). The soil bacterial diversity in the samples with adjuvant was higher than that in the samples without adjuvant, while the abundance values were the opposite. There were 10 main communities (&gt;0.3%) at phylum level in all soil samples, among which Proteobacteria, Bacteroidetes, Acidobacteria, Chloflexi, and Actinobacteria were the dominant communities, and the latter four’s abundance changed significantly (p &lt; 0.05). There were significant abundance differences between the groups of oligotrophic and eutrophic bacteria. The redundancy analysis and Monte Carlo tests showed that the total organic carbon (TOC), total phosphorus (TP), available phosphorus (AP), ammonia nitrogen, and total nitrogen were the main factors affecting soil bacterial diversity. At the same time, TOC, AP, and TP were the most critical factors affecting the overall characteristics of soil bacterial communities in different treatments, while soil residues had no significant effect on bacteria. This might be due to the addition and degradation of imazapyr and the coverage of S. alterniflora. The best recommendation is 2604 mL/acre of AGE 809 + 6070 mL/acre 25% imazapyr to be applied in China’s mangrove wetland reserves and coastal wetlands.

Research on Protective Development of Wetland Ecological Resources in Poyang Lake

As one of three major ecological regulatory systems in the world, wetlands play an important role in protection of ecological environment and biodiversity. As the largest freshwater lake in China, Poyang Lake is also one of the areas with the most abundant biological resources in wetland ecosystem in China, which has great ecological and economic benefits. In recent years, a string of problems inevitably exist in the further development of Poyang Lake wetland ecological resources. Based on comprehensive introduction of Poyang Lake wetland ecological resources, this paper makes a comprehensive analysis of its development and utilization status and existing problems. Besides, it also puts forward a series of strategies for protection and development of Poyang Lake wetland, in an effort to further protect ecological resources of Poyang Lake wetland and realize the sustainable utilization of resources.

Patterns and Dynamics of the Soil Microbial Community with Gradual Vegetation Succession in the Yellow River Delta, China

As one of the youngest coastal wetland ecosystems in China, the Yellow River Delta has a gradual succession from bare land to grassland. Six typical communities were selected for the present study of the patterns and dynamics of soil microbial community under the gradual transitional succession. In which soil physicochemical properties such as soil pH, electrical conductivity, soil organic carbon, total nitrogen, and available phosphorus were measured simultaneously. The composition, structure, and variety of soil microorganisms were explored. Our results revealed that soil salinity decreased with succession, while soil organic carbon and total nitrogen exhibited an upward trend. Soil salinity, soil organic carbon, and total nitrogen were found to be the main factors that affect microbial composition and diversity in the Yellow River Delta. The phylum Gemmatimonadetes had the highest abundance in the saline bare land. Changes in the soil microbial composition and structure were observed under different succession stages, and microbial richness increased with succession. This research advances our understanding of the relationships among microbial species resources and soil environment with community succession in the Yellow River Delta. It could assist the identification of salt-tolerant microorganisms beneficial for future applications and saline-alkali land improvements.

Predicted effects of Chinese national park policy on wildlife habitat provisioning: Experience from a plateau wetland ecosystem

Abstract Understanding the ecological consequences of conservation policies on wildlife is critical for species conservation and policy implementation. China began to call for establishing a national park system in 2013 and used national parks as the predominant feature for its system of protected areas in 2019. Payment for ecosystem services (PES) and relocation constitute two important management strategies in new Chinese national parks and protected area system. To better understand the potential outcomes of such programs, we studied the winter foraging distribution of the threatened Black-necked Crane (Grus nigricollis), a flagship species of plateau wetlands, in Dashanbao Protected Area, SW China. Field survey data were combined with environmental variables and land use maps to model winter foraging habitat with respect to human settlements subject to PES and relocation. High suitability for foraging was mapped in the core zone around crane roosting sites, villages, and far from disturbance (e.g. main roads). Aiming at converting farmland to wetland, the payment for ecosystem services programs increased probability of occurrence of cranes by changing land cover in appropriate areas relative to crane roosts and other spatially distributed variables. Surprisingly, areas within 1 km of villages were recognized as highly suitable foraging habitats for cranes, which depend on waste grain in farmland in winter, revealing the potential risk of relocation-induced food shortage for wintering cranes. We argue that as an effective strategy in improving wildlife habitat, PES should be encouraged and relocation programs that change the existing long-term established human-wildlife interactions should be implemented only under full understanding of these relationships. As a pioneer study of the effects of conservation policy on wetland ecosystems in China, this study could shed light on conservation management for such ecosystem and species showing high dependence on a human modified environment. Future work should also focus on the social effects of these conservation strategies, especially relocation, during national park planning in China.

Quantifying the Relative Importance of Climate Change and Human Activities on Selected Wetland Ecosystems in China

Climate change and human activities are important factors driving changes in wetland ecosystems. It is therefore crucial to quantitatively characterize the relative importance of these stressors in wetlands. Previous such analyses have generally not distinguished between wetland types, or have focused on individual wetland types. In this study, three representative wetland areas of the upper, middle and lower reaches of the Heilongjiang River Basin (HRB) were selected as the study area. An object-based classification was used with Landsat TM data to extract the spatial distribution of wetland in 1990, 2000 and 2010. We then quantified the relative importance of climate change and human activities on the wetlands by using the R package “relaimpo” package. The results indicated that: (1) the effects of human activities on wetland changes were greater (contribution rate of 63.57%) than climate change in the HRB. Specifically, there were differences in the relative importance of climate change and human activities for wetlands in different regions. Wetlands of the upper reaches were more affected by climate change, while wetlands in the middle and lower reaches were more affected by human activities; (2) climate change had a greater impact (contribution rate of 65.72%) on low intensity wetland loss, while human activities had a greater impact on moderate and severe intensity wetland loss, with respective contribution rates of 57.22% and 70.35%; (3) climate change had a larger effect on the shrub and forested wetland changes, with respective contribution rates of 58.33% and 52.58%. However, human activities had a larger effect on herbaceous wetland changes, with a contribution rate of 72.28%. Our study provides a useful framework for wetland assessment and management, and could be a useful tool for developing wetland utilization and protection approaches, particularly in sensitive environments in mid- and high-latitude areas.

Dynamic Changes in the Wetland Landscape Pattern of the Yellow River Delta from 1976 to 2016 Based on Satellite Data

The Yellow River Delta wetland is the youngest wetland ecosystem in China’s warm temperate zone. To better understand how its landscape pattern has changed over time and the underlying factors responsible, this study analyzed the dynamic changes of wetlands using five Landsat series of images, namely MSS (Mulri Spectral Scanner), TM (Thematic Mapper), and OLI (Operational Land Imager) sensors in 1976, 1986, 1996, 2006, and 2016. Object-oriented classification and the combination of spatial and spectral features and both the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI), as well as brightness characteristic indices, were used to classify the images in eCognition software. Landscape pattern changes in the Yellow River Delta over the past 40 years were then delineated using transition matrix and landscape index methods. Results show that: 1) from 1976 to 2016, the total area of wetlands in the study area decreased from 2594.76 to 2491.79 km2, while that of natural wetlands decreased by 954.03 km2 whereas human-made wetlands increased by 851.06 km2. 2) The transformation of natural wetlands was extensive: 31.34% of those covered by Suaeda heteropteras were transformed into reservoirs and ponds, and 24.71% with Phragmites australis coverage were transformed into dry farmland. Some human-made wetlands were transformed into non-wetlands types: 1.55% of reservoirs and ponds became construction land, and likewise 21.27% were transformed into dry farmland. 3) From 1976 to 2016, as the intensity of human activities increased, the number of landscape types in the study area continuously increased. Patches were scattered and more fragmented. The whole landscape became more complex. In short, over the past 40 years, the wetlands of the Yellow River Delta have been degraded, with the area of natural wetlands substantially reduced. Human activities were the dominant forces driving these changes in the Yellow River Delta.

Carbon budgets of wetland ecosystems in China.

Wetlands contain a large proportion of carbon (C) in the biosphere and partly affect climate by regulating C cycles of terrestrial ecosystems. China contains Asia's largest wetlands, accounting for about 10% of the global wetland area. Although previous studies attempted to estimate C budget in China's wetlands, uncertainties remain. We conducted a synthesis to estimate C uptake and emission of wetland ecosystems in China using a dataset compiled from published literature. The dataset comprised 193 studies, including 370 sites representing coastal, river, lake and marsh wetlands across China. In addition, C stocks of different wetlands in China were estimated using unbiased data from the China Second Wetlands Survey. The results showed that China's wetlands sequestered 16.87 Pg C (315.76Mg C/ha), accounting for about 3.8% of C stocks in global wetlands. Net ecosystem productivity, jointly determined by gross primary productivity and ecosystem respiration, exhibited annual C sequestration of 120.23 Tg C. China's wetlands had a total gaseous C loss of 173.20 Tg C per year from soils, including 154.26 Tg CO2 -C and 18.94 Tg CH4 -C emissions. Moreover, C stocks, uptakes and gaseous losses varied with wetland types, and were affected by geographic location and climatic factors (precipitation and temperature). Our results provide better estimation of the C budget in China's wetlands and improve understanding of their contribution to the global C cycle in the context of global climate change.

Diversity of Azotobacter in relation to soil environment in Ebinur Lake wetland

Ebinur Lake wetland is the most representative temperate arid zone wetland ecosystem in China and it is the centre of the oasis and desertification of the Northern slope of Tianshan conjugate. Soil samples were collected from three sites (Tamarix ramosissima, Halocnemum strobilaceum, and Phragmites australis) and different soil layers (0–5, 5–15,15–25, and 25–35 cm) within this wetland during spring, summer and autumn, and the diversity of cultured/uncultured Azotobacter based on the 16S rDNA and nifH genes was characterized. Polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) and bivariate correlation analysis were used to evaluate the relationship between the diversity of uncultured Azotobacter and soil environmental factors. A total of 17 cultured Azotobacter strains were isolated, five of which had stronger nitrogen-fixation ability (more than 10 mg/mL). Meanwhile, most of the cultured Azotobacter strain sequences were grouped into Bacillus sphaericus and Bacillus subtilis, and fewer sequences were affiliated with Actinomycetes. Furthermore, PCR-DGGE indicated that the diversity of uncultured Azotobacter was not balanced in some samples and the Shannon diversity index varied from 0.685 to 2.626. The uncultured Azotobacter were grouped into autotrophic genera Azotobacter and Rhizobium. Finally, bivariate correlation analysis showed that the diversity of uncultured Azotobacter was significantly correlated with soil organic carbon, inorganic carbon, NH4+-N, NO3−-N and microbial biomass N in the Ebinur Lake wetland in Xinjiang.

互花米草入侵影响下闽江河口湿地土壤有效硅的时空变化特征

PDF HTML阅读 XML下载 导出引用 引用提醒 互花米草入侵影响下闽江河口湿地土壤有效硅的时空变化特征 DOI: 10.5846/stxb201709041593 作者: 作者单位: 福建师范大学地理科学学院,福建师范大学地理科学学院,福建师范大学地理科学学院,福建师范大学地理科学学院,福建师范大学地理科学学院,福建师范大学地理科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41401114）；福建省基金面上项目（2016J01184）；福建省公益类科研院所专项（2016R1032-1）；福建师范大学地理科学学院研究生科研创新基金 Spatial and temporal variations of available silica content in marsh soils under the Spartina alterniflora invasion in the Min River estuary Author: Affiliation: College of Geographical Sciences, Fujian Normal University,College of Geographical Sciences, Fujian Normal University,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:2016年1-12月，选择闽江河口鳝鱼滩的短叶茳芏湿地、互花米草湿地以及二者的交错带湿地为研究对象，采用定位研究方法探讨了互花米草入侵影响下湿地土壤有效硅含量的时空变化特征。结果表明：互花米草入侵影响下3块湿地土壤有效硅含量随时间推移整体呈波动上升趋势；互花米草入侵显著提高了鳝鱼滩湿地30-60 cm土层土壤有效硅含量（P < 0.01），与短叶茳芏湿地相比，交错带湿地和互花米草湿地30-60 cm土层土壤有效硅含量分别增加了8.56%和19.97%，逐步线性回归分析表明土温和电导是影响其变化的重要因素（P < 0.01）。研究互花米草入侵影响下湿地土壤有效硅含量的变化特征，对于揭示湿地生态系统生源要素硅生物地球化学循环过程以及互花米草入侵及其扩张机制具有重要意义。 Abstract:Silica (Si) is the second most abundant element after oxygen in the soil and plays an important role in many biogeochemical processes, such as controlling the functions of terrestrial, marine, coastal, and inland water ecosystems. Wetland ecosystems are considered very important for Si transport in nutrient biogeochemical cycles. In recent years, Spartina alterniflora has become one of the most important invasive plants in coastal wetland ecosystems in China, which has caused considerable effects on the invaded regions. The Shanyutan marsh is the largest tidal wetland in the Min River estuary in the subtropical zone of southeast China. S. alterniflora started to invade Shanyutan marsh in 2002, and since then has gradually expanded its cover across the intertidal zone. The invasion of S. alterniflora has an important impact on the cycling of carbon, nitrogen, phosphorus, and sulfur, but the effect on available silica (ASi) in the soil is not yet clear. To explore the spatial and temporal variations of ASi contents in marsh soils under the S. alterniflora invasion in Shanyutan of the Min River estuary, the Cyperus malaccensis marsh, S. alterniflora marsh, and their ecotonal marsh were studied from January to December 2016. Results showed that temporal variations of ASi contents of three different marshes generally increased with time. Compared to C. malaccensis marsh, S. alterniflora invasion significantly increased ASi contents in 30-60 cm soil layers, and values in the ecotonal and S. alterniflora marshes increased by 8.56% and 19.97%, respectively. The stepwise linear regression analyses showed that soil temperature and electrical conductivity were the crucial factors affecting the variations of ASi contents. The spatial and temporal variations of ASi contents in marsh soils are important to reveal the biogeochemical cycling of silica to better understand the invasion and expansion mechanisms of S. alterniflora in a marsh ecosystem. 参考文献 相似文献 引证文献

The Introduction of Woody Plants for Freshwater Wetland Restoration Alters the Archaeal Community Structure in Soil

AbstractDue to the severe degradation of wetland ecosystems in China, great efforts, such as the reconstruction of forested wetlands, have been devoted to restore the damaged and degraded wetlands to support species diversity and ecosystem services. However, less attention has been given to the diversity and ecological significance of prokaryotes of the domain Archaea compared with prokaryotes of the domain Bacteria during the reconstruction of forested wetlands. Here, the effects of introduced woody plants (Taxodium distichum and Alnus trabeculosa) on the archaeal community in a freshwater wetland in the Yangtze estuary were investigated. The results showed that Thaumarchaeota obviously predominated at three studied sites in the freshwater wetland, the relative abundance of which decreased with increasing depth, ranging from 93.9% (0–10 cm) to 1.9% (30–40 cm) in mudflats, from 100% (0–10 cm) to 64.8% (30–40 cm) in T. distichum sediment and from 100% (0–10 cm) to 66.7% (40–50 cm) in A. trabeculosa sediment. The abundances of the archaeal amoA gene in woody plant sediments, ranging from 3.27 × 107 to 2.45 × 108 copies g−1 dry soil, were significantly higher than those in bare mudflat, ranging from 9.23 × 106 to 1.35 × 107 copies g−1 dry soil. The archaeal community, which was significantly affected by pH, microbial carbon and SO42− contents according to a canonical correspondence analysis, was significantly altered by plants and soil depth (p &lt; 0.05). These results indicated that the introduction of woody plants stimulates the proliferation of Thaumarchaeota, especially ammonia‐oxidizing archaea, which could be important contributors to the N cycle in forested wetland ecosystems. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Abundance and diversity of ammonia-oxidizing archaea and bacteria in the rhizosphere soil of three plants in the Ebinur Lake wetland

Ammonia oxidation is carried out by ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). The Ebinur Lake wetland is the best example of a temperate arid zone wetland ecosystem in China. Soil samples were collected from rhizosphere and non-rhizosphere soil containing Halocnemum strobilaceum (samples H and H'), Phragmites australis (samples R and R'), and Karelinia caspia (samples K and K') to study the relationship between environmental factors and the community structure of AOB and AOA. Phylogenetic analysis showed that the AOA sequences belonged to the Nitrosopumilus and Nitrososphaera clusters. AOB were grouped into Nitrosospira sp. and Nitrosomonas sp. Quantitative polymerase chain reaction results showed that the AOA abundance ranged from 2.09 × 104 to 2.94 × 105 gene copies/g soil. The highest number of AOA was detected in sample K, followed by samples R and H. AOB abundance varied between 2.91 × 105 and 1.05 × 106 gene copies/g soil, which was higher than that of AOA. Redundancy analysis indicated that electrical conductivity, pH, and NH4+-N might influence the community structure of AOA and AOB. AOB might play a more crucial role than AOA in ammonia oxidation based on AOB's higher diversity and abundance in the Ebinur Lake wetland in Xinjiang.

A novel unsupervised bee colony optimization (UBCO) method for remote-sensing image classification: a case study in a heterogeneous marsh area

ABSTRACTUnsupervised image classification is an important means to obtain land-use/cover information in the field of remote sensing, since it does not require initial knowledge (training samples) for classification. Traditional methods such as k-means and Iterative self-organizing data analysis technique (ISODATA) have limitations in solving this NP-hard unsupervised classification problem, mainly due to their strict assumptions about the data distribution. The bee colony optimization (BCO) is a new type of swarm intelligence, based upon which a simple and novel unsupervised bee colony optimization (UBCO) method is proposed for remote-sensing image classification. UBCO possesses powerful exploitation and exploration capacities that are carried out by employed bees, onlookers, and scouts. This allows the promising regions to be globally searched quickly and thoroughly, without becoming trapped on local optima. In addition, it has no restrictions on data distribution, and thus is especially suitable for handling complex remote-sensing data. We tested the method on the Zhalong National Nature Reserve (ZNNR) – a typical inland wetland ecosystem in China, whose landscape is heterogeneous. The preliminary results showed that UBCO (overall accuracy = 80.81%) achieved statistically significant better classification result (McNemar test) in comparison with traditional k-means (63.11%) and other intelligent clustering methods built on genetic algorithm (unsupervised genetic algorithm (UGA), 71.49%), differential evolution (unsupervised differential evolution (UDE), 77.57%), and particle swarm optimization (unsupervised particle swarm optimization (UPSO), 69.86%). The robustness and superiority of UBCO were also demonstrated from the two other study sites next to the ZNNR with distinct landscapes (urban and natural landscapes). Enabling one to consistently find the optimal or nearly optimal global solution in image clustering, the UBCO is thus suggested as a robust method for unsupervised remote-sensing image classification, especially in the case of heterogeneous areas.

Farmer's willingness to participate in wetland restoration: a hurdle model approach

Due to a severe degradation of the wetland ecosystem in China, great efforts have been devoted to promote farmers’ willingness to participate in wetland restoration. As the decision-making body, farmer's willingness to participate is critical to wetland restoration. It is thus important to understand factors that will affect farmers’ willingness to participate and their levels of participation. Using a survey sample of 1,009 farmers from the Poyang Lake wetland area in China, this article applies a hurdle model to empirically investigate the factors affecting individual farmers’ sequential decisions on whether or not to participate and how much land to enroll in wetland restoration. Results suggest that farmers’ information and knowledge about wetland restoration compensation policy is crucial in determining whether or not to participate in the first stage. Meanwhile, individual farmer characteristics and household attributes play different roles in influencing farmers’ participation decisions and acreage enrollment decisions. This study provides useful insights to identify effective policy instruments to motivate participation and ensure success of such policies.

Diversity of ammonia-oxidizing bacteria in relation to soil environment in Ebinur Lake Wetland

ABSTRACTAmmonia oxidation is the first and rate-limiting step of nitrification and is carried out by ammonia-oxidizing bacteria (AOB). Ebinur Lake Wetland, the most representative temperate arid zone wetland ecosystem in China, is the centre of oasis and desertification of the northern slope of Tianshan conjugate. Soil samples were collected from three sites (Tamarix ramosissima, Halocnemum strobilaceum and Phragmites australis) and different soil layers (0–5, 5–15, 15–25 and 25–35 cm) in this wetland in spring, summer and autumn and were used to characterize the diversity of AOB based on the ammonia monooxygenase (amoA) gene. Polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) and bivariate correlation analysis were used to analyse the relationship between the diversity of AOB and soil environment factors. The PCR-DGGE indicated that the diversity of AOB was high in the entire sample and the Shannon diversity index varied from 1.369 to 2.471. The phylogenetic analysis showed that the amoA fragments were grouped into Nitrosospira sp. and Nitrosomonas sp. Most amoA gene sequences fell within the Nitrosospira sp. cluster, and only a few sequences were clustered with Nitrosomonas sp., indicating that Nitrosospira sp. may be more adaptable than Nitrosomonas sp. in this area. Bivariate correlation analysis showed that the diversity of AOB was significantly correlated with soil organic matter, conductivity, total phosphorus and nitrate in the Ebinur Lake Wetland in Xinjiang.