Land use effects on soil organic carbon, nitrogen and salinity in saline-alkaline wetland

Land-use and soil management affects soil organic carbon （SOC） pools, nitrogen, salinity and the depth distribution. The objective of this study was to estimate land-use effects on the distribution of SOC, labile fractions C, nitrogen （N） and salinity in saline-alkaline wetlands in the middle reaches of the Heihe River Basin. Three land-use types were selected： intact saline-alkaline meadow wetland, artificial shrubbery （planting Tamarix） and farmland （cultivated for 18 years） of soils previously under meadow wetland. SOC, easily oxidized carbon, microbial biomass carbon, total N, NO3--N and salinity concentrations were measured. The results show that SOC and labile fraction carbon contents decreased significantly with increasing soil depth in the three land-use wetlands. The labile fraction carbon contents in the topsoil （0-20cm） in cultivated soils were significantly higher than that in intact meadow wetland and artificial shrubbery soil. The aboveground biomass and soil permeability were the primary influencing factors on the contents of SOC and the labile carbon in the intact meadow wetland and artificial shrubbery soil, however, the farming practice was a factor in cultivated soil. Agricultural measures can effectively reduce the salinity contents; however, it caused a significant increase of NO 3--N concentrations which posed a threat to groundwater quality in the study area.

Denitrification Potential of Marsh Soils in Two Natural Saline-alkaline Wetlands

Little information is available on denitrification potential of marsh soils in natural saline-alkaline wetlands. The denitrification potentials of an open wetland in the floodplain(Erbaifangzi wetland) and a closed wetland(Fulaowenpao wetland) in backwater areas in Jilin Province of Northeast China were monitored by an anaerobic incubation at 30℃ for 25 days. Our results showed that the relative denitrification index(RDI) increased gradually with incubation time, and showed a rapid increase in the first 5 days of incubation. The RDI values declined quickly from surface soils to subsurface soils and then kept a small change in deeper soils along soil profiles over the incubation time. Denitrification proceeded much faster in the top 20 cm soils of open wetland than in the closed wetland, whereas no significant differences in RDI values were observed in deeper soils between both wetlands. The RDIs were significantly negatively correlated with bulk density and sand content, while a significantly positive correlation with clay content, soil organic matter, total nitrogen and phosphorous. The maximum net NO–3-N loss through denitrification in 1 m depth were higher in the open wetland than the closed wetland with higher soil pH values. Future research should be focused on understanding the influencing mechanisms of soil alkalinity.

CONCEPT, DISTRIBUTION LAW AND FORMATION MACHANISM OF INLAND SALINE ALKALINE WETLAND─ ─ Taking Songliao Plain for Example

The paper, taking Songliao Plain for example, studied the concept, distribution law and formation mechanism of inland saline alkaline wetland. The inland saline alkaline wetland is distributed over the inland region of arid or semi arid climate; it is the wet or slightly stagnant environment, forming saline alkaline soil and salt vegetation and making the geogra phical environment fonming complex with an ecosystem of saline alkaline wetland. The laws of zone nature and non zone nature control the distribution of the inland saline alkaline wetland that extensively spreads in north part of China and other countries. The inland saline alkaline wetland is formed jointly by atmosphere, hydrosphere, lithosphere and biosphere including intellectual sphere. Under the special condition, the artificial activity is possibly the key function. In order to improve the human environment, it is a great duty confronting the whole world to rationally transform the inland saline alkaline wetland. Therefore, we presented an anti inland theory to promote the environment transformation.

Soil Carbon, Nitrogen and Phosphorus Concentrations and Stoichiometries Across a Chronosequence of Restored Inland Soda Saline-Alkali Wetlands, Western Songnen Plain, Northeast China

Soil carbon(C), nitrogen(N) and phosphorus(P) concentrations and stoichiometries can be used to evaluate the success indicators to the effects of wetland restoration and reflect ecosystem function. Restoration of inland soda saline-alkali wetlands is widespread, however, the soil nutrition changes that follow restoration are unclear. We quantified the recovery trajectories of soil physicochemical properties, including soil organic carbon(SOC), total nitrogen(TN), and total phosphorus(TP) pools, for a chronosequence of three restored wetlands(7 yr, 12 yr and 21 yr) and compared these properties to those of degraded and natural wetlands in the western Songnen Plain, Northeast China. Wetland degradation lead to the loss of soil nutrients. Relative to natural wetlands, the mean reductions of in SOC, TN, and TP concentrations were 89.6%, 65.5% and 52.5%, respectively. Nutrients recovered as years passed after restoration. The SOC, TN, and TP concentrations increased by 2.36 times, 1.15 times, and 0.83 times, respectively in degraded wetlands that had been restored for 21 yr, but remained 29.2%, 17.3%, and 12.8% lower, respectively, than those in natural wetlands. The soil C∶N(RC N), C∶P(R CP), and N∶P(R NP) ratios increased from 5.92 to 8.81, 45.36 to 79.19, and 7.67 to 8.71, respectively in the wetland that had been restored for 12 yr. These results were similar to those from the natural wetland and the wetland that had been restored for 21 yr(P > 0.05). Soil nutrients changes occurred mainly in the upper layers(≤ 30 cm), and no significant differences were found in deeper soils(> 30 cm). Based on this, we inferred that it would take at least 34 yr for SOC, TN, and TP concentrations and 12 yr for RC N, R CP, and RN P in the top soils of degraded wetlands to recover to levels of natural wetlands. Soil salinity negatively influenced SOC(r =-0.704, P < 0.01), TN(r =-0.722, P < 0.01), and TP(r =-0.882, P < 0.01) concentrations during wetland restoration, which indicates that reducing salinity is beneficial to SOC, TN, and TP recovery. Moreover, plants were an important source of soil nutrients and vegetation restoration was conducive to soil nutrient accumulation. In brief, wetland restoration increased the accumulation of soil biogenic elements, which indicated that positive ecosystem functions changes had occurred.

Characterization of saline soil for the halophytes of largest inland saline wetland of India using geospatial technology

About 23%of the surface area and 44%of the volume of all the lakes are occupied by saline lakes in the world.Importantly,agricultural diversion,illegal encroachment,pollution,and invasive species could cause these lakes to dry up completely or partially by 2025.Illegal saltpan encroachment is causing Sambhar,India’s largest saline lake,to shrink by 4.23%every decade.This study aims to characterize the soil parameters where halophytes are growing.A literature survey was conducted for halophytes and soil characteristics.The study area was divided into four zones for stratified random sampling.Soil sampling was conducted in February 2021.The soil indicators for halophyte selected were pH,electrical conductivity,moisture,salinity,organic carbon,and organic matter.The obtained results were interpolated in the geospatial platform for soil characteristic mapping.It is found that no research is conducted on halophytes of the lake.Studies on soil are also inconsistent and only six common parameters could be identified.Results show that the pH ranged 9.37-7.66,electrical conductivity was 16.1-0.38,moisture 23.37%-1.2%,organic carbon 3.29%-0.15%,organic matter 5.6%-0.2%,and salinity 8.86%-0.72%.Though these results show improved condition as compared to last few years,in long term,the lake is desiccating.During the UN Decade of Ecosystem Restoration(2021-2030),if these causes are not addressed,the ecosystem may completely dry up.

Extracting Eco-hydrological Information of Inland Wetland from L-band Synthetic Aperture Radar Image in Honghe National Nature Reserve, Northeast China

Taking a typical inland wetland of Honghe National Nature Reserve (HNNR), Northeast China, as the study area, this paper studied the application of L-band Synthetic Aperture Radar (SAR) image in extracting eco-hydrological information of inland wetland. Landsat-5 TM and ALOS PALSAR HH backscatter images were first fused by using the wavelet-IHS method. Based on the fused image data, the classification method of support vector machines was used to map the wetland in the study area. The overall mapping accuracy is 77.5%. Then, the wet and dry aboveground biomass estimation models, including statistical models and a Rice Cloudy model, were established. Optimal parameters for the Rice Cloudy model were calculated in MATLAB by using the least squares method. Based on the validation results, it was found that the Rice Cloudy model produced higher accuracy for both wet and dry aboveground biomass estimation compared to the statistical models. Finally, subcanopy water boundary information was extracted from the HH backscatter image by threshold method. Compared to the actual water borderline result, the extracted result from L-band SAR image is reliable. In this paper, the HH-HV phase difference was proved to be valueless for extracting subcanopy water boundary information.

Seasonal Abundance and Diversity of Birds of Prey and Owls in Al Wathba Wetland Reserve in Abu Dhabi, UAE

Inland wetlands in Abu Dhabi Emirate are wintering and stopover sites for migratory birds of prey. We conducted long-term regular monitoring surveys in Al Wathba Wetland Reserve (AWWR) from January 1995 to December 2022. Both diurnal and occasionally nocturnal surveys were undertaken to record the migratory raptors and owls in the Wetland Reserve. During the study, a total of 1282 regular monitoring visits were undertaken and 27 species of diurnal raptors and owls representing five families and three orders were detected. These represent 57% of the total species of birds of prey recorded in the UAE. Overall, 63% of all the species that we observed were Accipitriformes followed by 26% Falconiformes and 11% Strigiformes. We found that changes in mean daily temperature have a positive effect on raptor species diversity and abundance in the Wetland Reserve. The species encounter rate was higher in low temperature as compared to high temperature and overall regression equation was statistically significant F (4, 1126) = 8.49), p = 0.00). However, the numbers of raptors did not vary significantly across the years (p = 0.51). Western Marsh-harrier (Circus aeruginosus) and Greater Spotted Eagle (Clanga clanga) were recorded to be the most abundant species in the wetland reserve followed by Common Kestrel (Falco tinnunculus). However, the encounter rate of globally threatened Greater Spotted Eagle was detected to have significantly decreased since 2016. Moreover, 63% of the species detected were uncommon and rarely recorded such as 1) Saker Falcon 2) Lanner Falcon 3) Long-eared Owl & Merlin, which were the rare records from the wetland reserve. Furthermore, 27 years of regular monitoring in the wetland have yielded diverse diurnal raptors and owl fauna (H) = 0.83, (E) = 1.43 (Shannon Diversity Index). The results demonstrate that long-term monitoring surveys in arid environments are essential to determine the trends in the raptor populations and to document rare and globally important species.

Soil remediation of degraded coastal saline wetlands by irrigation with paper mill effluent and plowing

Combined with anti-waterlogging ditches, irrigation with treated paper mill effluent （TPME） and plowing were applied in this study to investigate the effects of remediation of degraded coastal sa- line-alkaline wetlands. Three treatments were employed, viz., control （CK）, irrigated with 10 cm depth of TPME （I）, and plowing to 20 cm deep before irrigating 10 cm depth ofTPME （IP）. Results show that both I-treatment and IP-treatment could improve soil structure by decreasing bulk density by 5% and 8%. Irrigation with TPME containing low salinity stimulated salts leaching instead of accumulating. With anti-waterlogging ditches, salts were drained out of soil. Irrigation with 10 cm depth of TPME lowered total soluble salts in soil and sodium adsorption ration by 33% and 8%, respective!y, but there was no significant difference compared with CK, indicating that this irrigation rate was not heavy enough to remarkably reduce so!l salinity and sodicity, Thus, in-i： gation rate should be enhanced in order to reach better effects of desalinization and desodication. Irrigation with TPME significantly increased soil organic matter, alkali-hydrolyzable nitrogen and available phosphorus due to the abundant organic matter in TPME. Plowing increased soil air circulation, so as to enhance mineralization of organic matter and lead to the loss of organic matter; however, plowing significantly improvedsoil alkali-hydrolyzable nitrogen and available phosphorus. Improvements of physicochemical properties in I-treatment and IP-treatment both boosted soil microbial population and activity. Microbial biomass carbon increased significantly by 327% （I-treatment） and 451% （IP-treatment）, while soil respiration increased significantly by 316% （I-treatment） and 386% （IP-treatment）. Urease and dehydrogenase activities in both I-treatment and IP-treatment were significantly higher than that in CK. Phosphatase in IP-treatment was significantly higher than that in CK. Compared to I-treatment, IP-treatment improved all of the soil properties except for soil organic matter. The key to remediation of degraded sa- line-alkaline wetlands is to decrease soil salinity and sodicity; thus, irri- gation plus plowing could be an ideal method of soil remediation.

EVAPOTRANSPIRATION OF LOW-LYING PRAIRIE WETLAND IN MIDDLE REACHES OF HEIHE RIVER IN NORTHWEST CHINA

Low-lying prairie wetland, which has characteristics of both grassland and wetland, has irreplaceable ecological functions in inland river basins of Northwest China. Owing to its small-scale distribution, so far, the observation and research on it are rare. The estimation of evapotranspiration is significant to ecological and environmental construction, scientific management of pasture and protection of wetland. For studying the evapotranspiration （ET） of low-lying prairie wetland in the middle reaches of the Heihe River, an inland river, in Northwest China, the automatic weather station in Linze Ecological Experimental Station of Lanzhou University （39°15′ 3″N, 100°03′ 52″ E）, Linze, Gansu Province, was selected as a case study. Based on meteorological data collected, Bowen-Ratio Energy Balance （BREB） method was used to calculate the evapotranspiration （ET） of low-lying prairie wetland. The analysis results showed that in a whole year （September 2003 -August 2004）, the total ET was 611.5mm and mean daily 1.67mm/d. The ET varied with different growing stages. In non-growing stage （NGS）, initial growing stage （IGS）, middle growing stage （MGS） and end growing stage （EGS）, the ET was 0.57, 2.01, 3.82 and 1.49mrrdd, with a percentage of total ET of 18.26%, 9.20%, 61.83% and 10.71% respectively. In March, ET began to increase. But in April, the ET increased most. After that, it increased gradually and got the maximal value in July. From then on, the ET decreased gradually. In September, the ET decreased rapidly. With the ending of growing and the freezing of soil, the ET stopped from the middle of November to February in next year. Hourly ET analysis showed that at 8：00 a.m. （during MGS at 7：00 a.m.）, the evapotranspiration began, at 13：00 p.m. got its maximal value and at 19：00 p.m. （during MGS at 20：00 p.m.）, the evapotranspiration stopped. The intensity of ET in sunny day was much larger than that in cloudy day in the same growing stage.

Cultivation of Chlorella sp.HQ in inland saline-alkaline water under different light qualities

Inland saline-alkaline water can be used for the low-cost cultivation of microalgae,but whether algal biomass under various light sources has the potential to produce biodiesel remains to be developed.Herein,the influence of different light-emitting diode(LEDs)light colors(blue,red,white,mixed blue-red,and mixed blue-white LED)on the growth performance,lipid accumulation,and fatty acid composition of Chlorella sp.HQ cultivated in inland saline-alkaline water was investigated.The highest algal density was obtained under blue LEDs at the end of cultivation,reaching 1.93±0.03 × 10^(7) cells/mL.White LEDs can improve biomass yield,total lipid yield,and triacylglycerol yield per algal cell.The main fatty acid components of Chlorella from inland saline-alkaline water were palmitic acid and linoleic acid.The Biodiesel Analyzer software was used to predict algal biodiesel quality by estimating different quality parameters.The cetane number,kinematic viscosity,and density of Chlorella biodiesel were 51.714-67.69,3.583-3.845 mm^(2)/s,and 0.834-0.863 g/cm^(3),respectively.This flirther proved that the Chlorella biomass obtained from inland saline-alkaline water has the potential to be used as a high-quality biodiesel feedstock.

天津滨海湿地土壤盐分空间演变规律研究

天津滨海的天然湿地主要起源于全新世中、晚期以来的海陆变迁,后来的海陆交互作用以及人类活动使其产生了不同程度的盐渍化.为研究湿地土壤盐分自潮间带向内陆演进的演变规律,依据距海距离,选取潮间带（0 km）、北大港（24 km）、七里海（38 km）和大黄堡（70 km）4个典型滨海湿地,对其土壤盐分的演变规律进行分析.结果显示：（1）土壤含盐量和电导率自潮间带向内陆呈显著指数递减趋势,并表现出表层（0～5 cm）聚集特征.（2）除（HCO3-＋CO32-）外,离子含量与距海距离之间呈极显著指数负相关关系.潮间带、七里海和大黄堡湿地的土壤阳离子均以Na＋为主,而北大港湿地以Na＋和Ca2＋组成占绝对优势.从潮间带到内陆温地,土壤中阴离子从以Cl-为主过渡到以Cl-、SO42-和HCO3-＋CO32-为主.（3）除大黄堡湿地,各湿地含盐量均与Cl-呈极显著正相关,与SO42-从潮间带湿地到内陆湿地由不相关过渡到极显著正相关,HCO3-＋CO32-与含盐量仅在北大港湿地呈极显著正相关.（4）潮间带湿地土壤表层 （0～5 cm）和中间层（20～50 cm）为弱碱化土,次表层（5～20 cm）和深层（50～100 cm）为中度碱化;北大港和大黄堡湿地整个1 m土层均为弱碱化;七里海湿地为中度碱化.

湿地与我国内陆城市的可持续发展

在我国,内陆城市的城市发展水平和经济发展水平都相对落后,因此我国内陆城市的可持续发展是关系到整个国家能否高速、健康发展的决定性因素。湿地是城市生态环境和城市生态支持系统的重要组成部分,城市中以自然景观为主的公共开放空间。本文通过对城市湿地和城市周边湿地功能作用的分析,指出湿地可以为解决我国内陆城市的生态环境问题,实现城市可持续发展,提供基础条件和生态保障。对我国生态城市的发展和建设具有借鉴意义。

松嫩平原内陆盐碱湿地的类型特征及分布规律

内陆盐碱湿地是湿地的重要组成部分,其类型、特征及分布规律的研究十分薄弱。松嫩平原是世界上内陆盐碱湿地发育的典型地区之一。本文参考国内外湿地分类标准,结合松嫩平原的特点,建立了内陆盐碱湿地的分类体系,将该区的盐碱湿地划分为2个湿地类,6个湿地型,13个湿地亚型,描述了各类型的主要特征,并阐述了松嫩平原内陆盐碱湿地的分布规律。这对我国的湿地分类系统是一个重要的补充,对进一步实施内陆盐碱湿地的保护、恢复和重建,促进松嫩平原社会经济和环境的可持续发展都具有重要意义。

内陆盐沼湿地土壤碳氮磷剖面分布的季节动态特征

本文以向海湿地为例探讨了内陆盐沼湿地土壤剖面中碳氮磷等生源要素的季节动态变化特征及其影响因素.结果表明,内陆盐沼湿地土壤中有机碳、全氮和全磷含量与土壤深度之间存在显著负相关,在剖面中均表现为由表层向下层其含量不断减少的趋势,且具有明显的季节波动特征,除表层土壤碳氮含量随季节变化呈持续增加外,生源要素剖面分布的季节变化基本表现为先减少后增加的趋势.有机碳、全氮和全磷含量之间关系密切,且三者受土壤粒度的影响都非常显著.土壤pH值仅与土壤有机碳之间存在显著的相关关系,而对全氮和全磷含量的影响则不显著.

玛纳斯河流域湿地平原水库群对流域生态环境作用的研究

玛纳斯河流域湿地水库群上接大河、下通灌区,是流域供水系统中最主要、保证率最高的供水水源。对位于玛纳斯河流域泉水溢出带中的湿地水库群对流域生态环境的作用进行了研究,结果表明,该湿地水库群在防止湿地萎缩退化、防止次生盐渍化、保护流域内生物多样性、防风固沙、防止土壤沙化、抵御洪、旱灾害威胁、加强湿地调控能力以及增加了绿洲的人口承载能力和生产力等方面起到了很好的保护作用。该湿地水库群的建设为干旱区山前潜水平原地区的生态工程建设、水资源安全与可持续利用提供了一种良好的示范。

内陆碱化湿地土壤有机质和全磷的时空分布特征

以付老文泡湿地为研究对象,分析了内陆碱化湿地土壤有机质和全磷含量的时空分布特征。研究结果表明7月表层土壤有机质和全磷空间分布格局的异质性高于亚表层,而9月亚表层土壤则呈现出较高的异质性。2采样期内有机质和全磷含量均呈现由表层向下呈减少趋势,除9月土壤有机质外,上下土壤层内的有机质和全磷含量均存在显著性差异。湿地全磷随土壤有机质增加呈幂函数增长变化。湿地土壤有机质和全磷随土壤水分含量增加均呈对数衰减变化,但土壤有机质和全磷随pH值增加则分别呈现指数和幂函数衰减变化。

扎龙盐沼湿地对乌裕尔流域径流变化的水文响应

乌裕尔河流域水环境的变化导致下游湿地迅速退化。探讨了近65 a(1951-2015)扎龙湿地系统对乌裕尔河流域径流量变化的响应。结果表明:乌裕尔河中下游的径流量急剧减少给下游湿地的演替带来明显的影响,上游来水供给不足导致湿地长期处于干旱缺水的状态,湿地水面面积与蓄水量显著减少,并导致扎龙湿地地下水位显著降低(P<0.05)。湿地持续干旱缺水引发此区域大面积的沼泽退化并发生次生盐渍化。近年来,扎龙湿地发育的盐渍土面积达到250 km^2以上,并且向核心区蔓延。湿地持续退化对在湿地栖息和繁殖的珍稀水禽带来巨大的冲击。

内陆湿地保护的水环境控制模式研究

水是湿地生态的基本因子 ,对湿地的形成、演化、保护及发挥其功能具有决定性的控制作用 ,保护湿地的重要措施之一是保护湿地的水环境。根据水对湿地的决定性作用 ,在湿地水量均衡和水质均衡模型的基础上 ,提出湿地保护的水环境控制模式及措施。内陆湿地必须通过补水并适当排水才能控制湿地的水质、水量 ,达到保护湿地的目的。以吉林省查干湖湿地为例应用所建立的数学模型进行分析计算 ,确定该湿地保护所需的补水量及排水量。

西北内陆干旱区河流绿色走廊湿地景观格局变化及其生态效应研究——以车尔臣河下游为例

应用“3S”技术，通过选取景观的多样性、优势度、破碎度和斑块形状等空间格局指数对车尔臣河下游绿色走廊1975～2007年近32a问湿地景观格局变化进行研究，并对景观格局变化产生的生态效应进行了分析。结果表明：1975—2000年，湿地面积与斑块数量小幅度增大；2000～2007年，湿地面积与斑块数量大幅度减小，斑块平均面积与斑块密度持续减小，斑块形状趋于复杂，景观格局的多样性减小，优势度与破碎化程度增大。在各湿地类型中，河流湿地面积变化幅度较小，湖泊湿地面积大幅度增大，沼泽湿地面积大幅度减小。

中国内陆天然湿地的类型特征及分布规律-Ⅰ类的划分

在综述前人湿地分类方法的基础上,提出了湿地分类应遵循的6条原则,借鉴任继周等提出的草原综合顺序分类法,并依上述原则,提出了依照生物气候-湿地基底物质结构-植被的我国内陆天然湿地的综合顺序分类方法。内陆天然湿地综合顺序分类法第一级为类,分类指标是积水深度和>0℃的年积温(∑θ)。积水深度和>0℃的年积温(∑θ)是量化的指标,利用这2个指标将我国天然湿地分为21个类,并得到湿地类别的检索图。第二级———亚类的划分,以湿地基底物质结构作为指标;第三级———型的划分,以植被类型作为指标,分为挺水型、浮叶型、沉水型以及漂浮型。对我国的天然湿地依照生物气候等指标进行类的划分,结果表明,寒冷浅水类(ⅠB)、微温浅水类(ⅢB)、寒温浅水类(ⅡB)、寒冷深水类(ⅠA)和暖温浅水类(ⅣB)是我国分布面积最广的5个湿地类型,占我国内陆天然湿地总面积的79.75%,主要分布在青海、西藏、新疆、甘肃、四川、内蒙古、吉林、黑龙江;而暖热浅水类(ⅤB)、炎热浅水类(ⅦB)、炎热深水类(ⅦA)、亚热浅水类(ⅥB)、寒温深水类(ⅡA)是我国分布面积最小的5个内陆天然湿地类型,分布在安徽、湖北、云南、广东、广西、海南、贵州、青海,仅占我国内陆天然湿地总面积的0.83%。我国现有内陆天然湿地占湿地综合顺序法中21类的20类,炎热季节性类(ⅦC)在我国无分布。由于湿地综合顺序分类法检索图充分体现了天然湿地各个类之间的发生学关系,从而为在全球气候暖干化的背景下,预测未来天然湿地类的演替奠定了基础。