Effects of forest cover types and environmental factors on soil respiration dynamics in a coastal sand dune of subtropical China

Trees on sand dunes are more sensitive to environmental changes because sandy soils have extremely low water holding capacity and nutrient availability. We investigated the dynamics of soil respiration(Rs) for secondary natural Litsea forest and plantations of casuarina,pine, acacia and eucalyptus. Results show that significant diurnal variations of Rsoccurred in autumn for the eucalyptus species and in summer for the pine species, with higher mean soil respiration at night. However, significant seasonal variations of Rswere found in all five forest stands. Rschanged exponentially with soil temperatures at the 10-cm depth; the models explain 43.3–77.0% of Rs variations. Positive relationships between seasonal Rsand soil moisture varied with stands. The correlations were significant only in the secondary forest, and the eucalyptus and pine plantations. The temperature sensitivity parameter(Q10 value) of Rsranged from 1.64 in casuarina plantation to 2.32 the in secondary forest; annual Rswas highest in the secondary forest and lowest in the pine plantation. The results indicate that soil temperatures and moisture are the primary environmental controls of soil respiration and mainly act through a direct influence on roots and microbial activity. Differences in root biomass, quality of litter,and soil properties(pH, total N, available P, and exchangeable Mg) were also significant factors.

Habitat Use, Home Range, and Hibernaculum of the Mongolian Racerunner, Eremias argus (Lacertidae, Reptilia) in a Coastal Sand Dune in South Korea

Information on habitat use is critical in sizing protected areas for endangered reptile species. To investigate habitat use, home range, and hibernaculum of the endangered Mongolian Racerunner(Eremias argus), we radio-tracked 40 specimens in a coastal sand dune in South Korea. Of the 163 locations recorded during the breeding season, 150(92.0%) were in grass sand dunes, and the rest(8.0%), all associated with the same lizard, were in shrub sand dunes. All of the 123 locations recorded during the non-breeding season were in grass sand dunes. No lizards were found in the grasslands abutting the dunes. The four lizards with identifiable hibernation sites were found under an average of 17.8 cm of sand and were all located in grass sand dunes. The lizards moved approximately 5 m daily and used 162 m2of home range(computed by minimum convex polygon, MCP) during the breeding season, and they moved approximately 2 m and used 68 m2of home range during the non-breeding season. However, the mean daily moved distances and MCP home ranges were not statistically significantly different between the seasons or between males and females. Our results suggest that in coastal sand dunes, E. argus uses grass sand dunes as its main habitat throughout the year. This finding could be used to determine the appropriate habitat size and to designate for the conservation of this endangered species.

Endophytic fungi of wild legume Sesbania bispinosa in coastal sand dunes and mangroves of the Southwest coast of India

Evaluation of 450 surface sterilized tissue segments of a seasonal wild legume, Sesbania bispinosa （Jacq.）, of coastal sand dunes and mangroves of southwest India yielded 546 isolates comprising 39 endophytic fungi with six dominant taxa （Aspergillus flavus, Aspergillus niger, Cladosporium tenuissimum, Fusarium moniliforme, Penicillium chrysogenum and morpho sp. 1）. A consortium of saprophytic, pathogenic and toxigenic fungi exists as endophytes in S. bispinosa. Number of segments colonized, number of isolates obtained, species richness and diversity were higher in S. bispinosa in mangroves compared to coastal sand dunes. Seeds yielded more fungal isolates, but species richness and diversity were low. In spite of low fungal colonization in root segments, the diversity was high. Up to 30-40 % endophytic fungi of S. bispinosa differed between coastal sand dunes and mangroves revealing partial host- and habitat-specificity. As S. bispi- nosa is extensively used as green manure and forage in southwest India, further studies especially on the bioactive compounds of its endophytic fungi might broaden its range of uses. In addition to conventional morphologicaltechniques, molecular tools would provide precise insight on the endophytic fungi of coastal sand dunes and mangroves.

Effects of Forest Types and Environmental Factors on Soil Microbial Biomass in a Coastal Sand Dune of Subtropical China

Coastal sand dune ecosystems generally have infertile soil with low water-holding capacity and high salinity. However, many plant species have adapted to the harsh sand environment along the southeastern coast of China. Studying the microbial biomass in such an ecosystem can improve our understanding of the roles that microbes play in soil fertility and nutrient cycling. We investigated the differences in soil microbial biomass carbon(MBC) and nitrogen(MBN) contents and their seasonal dynamics in five forest types(a secondary forest and plantations of Casuarinas, Pine, Acacia, and Eucalyptus). The results indicated that the seasonal variations of soil MBC and MBN contents in all five forest stands were higher in spring and winter, but lower in summer and autumn. The MBC content was lower in the Casuarinas plantation than in the other plantations in the same soil layer. However, no significant differences were observed in MBN contents among the different forest types. The MBC and MBN concentrations were positively correlated with soil moisture, but negatively correlated with soil temperature. The MBC and MBN contents also decreased with increasing soil depth. Across all soil layers, secondary forest had the highest MBC and MBN concentrations. Our study also showed that the MBC and MBN contents were positively affected by total soil carbon(TC), pH, and litter N content, but were negatively impacted by soil bulk density and litter C content. Moreover, the MBN content was positively correlated with root N content. In summary, environmental factors and the differences in litter and fine roots, soil nutrient contents, as well as the soil physical and chemical properties caused by different tree species collectively affected the concentrations of the soil MBC and MBN.

Impact of Sand Mining and Sea Reclamation on the Environment and Socioeconomic Activities of Ikate and Ilubirin Coastal Low Income Communities in Lagos Metropolis, Southwestern Nigeria

Land reclamation is gradually posing negative impact on man due to unplanned urbanization. A study was carried out on impact of land reclamation through sand mining of coastal communities in Ikate and Ilubirin in Lagos, Nigeria. Ten waters (8 surface and 2 groundwater sources), 10 soil samples and air were collected and taken for analysis. Results of water revealed concentrations lower than WHO (2017) and SON (2007) standards. Soil/sediment with average crustal value revealed Pb and Cd above standard values, which is attributed to anthropogenic influence on soils. Quality of air in the study was mainly particulate matter arising from the sea and reclaimed land in the surroundings of the environment with the highest Total Suspended Particulate of 0.8 mg/m3 in sulfur dioxide. This explains corrosion found on the roofs of the communities. Therefore, in the development planning adequate precautions should be put in place to avert environmental degradation.

Effect of Cu and Zn on Maize (<i>Zea mays</i>L.) Yield and Nutrient Uptake in Coastal Plain Sand Derived Soils of Southeastern Nigeria

Laboratory, greenhouse and field studies were undertaken to investigate the status of Cu and Zn and to find out whether the addition of these nutrient elements in soils would increase maize grains and yield components and also, remediate their constraints in coastal plain sand derived soil of southeastern Nigeria, for optimization of maize (Zea mays L.) yields. Dry matter yields, plant concentrations, plant uptake, and maize grain yields were used to evaluate the effects of Cu and Zn levels. In both the greenhouse and field experiments, hydrated Cu and Zn sulphate fertilizers were applied to the soils in separate experiments at seven levels (0, 2, 4, 6, 8, 10 and 12 kg·ha&#45;1) for Cu and Zn respectively. The recommended N, P, and K at rates of 120, 60, 30 kg·ha&#45;1, respectively, were also used as basal application. The results showed the status of available Cu and Zn by 0.1 N HCl was found to be low in the soil. The application of Cu and Zn into the soils significantly (P < 0.05) increased maize dry matter production, concentration, uptake and grain yields. The estimated optimum rates for Cu and Zn under greenhouse environments were established at 10 kg·Cu·ha&#45;1 and 8 kg·Zn·ha&#45;1, respectively. Maximum uptake and grain yields in maize were also established at 10 kg·Cu·ha&#45;1 and 8 kg·Zn·ha&#45;1, respectively. However, maize response curve showed that for optimum grain yield, concentration for Cu was determined to be 10 mg·kg&#45;1, while for Zn it was 8 mg·kg&#45;1. The current study showed that though the soils have a severe Cu and Zn deficiency, which could be due to their strong sorption capacity and nutrients mining due to intensive and continuous cropping, maize production can still be increased considerably in this soil and other similar soils in the same agro-ecological zone within a coastal plain sand derived soil by applying Cu and Zn at rates of 10 kg·Cu·ha&#45;1 and 8 kg·Zn·ha&#45;1, respectively.

A Numerical Model of Coastal Processes of Sand Beaches Based on Long-Term Wave Series

A numerical model of shoreline change of sand beaches based on long-term field wave data is proposed, the explicit and implicit finite difference forms of the model are described, and an application of the model is presented. Results of the application indicate that the model is sensitive to the order of the input wave data, and that the effects of long-term wave series and the effects of the mean annual wave conditions on the model are different. Instead of a single wave condition, the wave series will make the calibration and the verification of the model more practical and the results of the model more reasonable.

Measuring the Total Economic Value of Traditional Sand Dredging in the Coastal Lagoon Complex of Grand-Nokoué(Benin)

Sand is a crucial resource for society’s development. Among the most exploited sand quarries in the world are the lagoon and wetland sand. Although mechanical sand dredging is the most spread technique, manual and traditional techniques are still widely used in West Africa. The purpose of this paper is twofold: to describe traditional sand dredging (TSD), highlighting the procedure used and the structural organization of this activity, and to evaluate the total economic value of TSD in order to help decision making about wetland management. Therefore, TSD occurring in the coastal lagoon complex of Grand Nokoué (CLCGN) in Benin was investigated. Field surveys indicate that TSD is mainly dominated by men, about 93% of the actors. It required intense physical efforts including diving to the bottom of the lake and removing manually the sand in backed toward the surface of the water. TSD actors are organized in local associations which deliver extraction license and discuss with both the others actors and the local government. The total economic value of the benefits of TSD to the population, estimated using direct market value and replacement cost, was estimated at 2.44 million USD per year for 127,818 m3 of sand extracted. It is clear that introduction of mechanical sand dredging will increase the amount the sand removed and subsequently will increase some benefits such as reduction of flooding amplitude and mitigation of the filling of the lakes. However, mechanical sand removal will also considerably reduce the profit the local population makes from sand commercialization which currently represents 80% the total economic value of TSD.

Analysis of the Sedimentary Characteristics and Origin of the “Old Red Sands ”in the Coastal Areas of Southeast Fujian

The "Old Red Sands" are widely distributed and typically developed over the coastal areas of Southeast Fujian, but there are different views on their origin. Based on the overall field investigations and a series of lab studies, the paper suggests that the "Old Red Sands" are mainly formed by the beach wind-drift sands and ,locally, by slope wash and alluviation.

Coastal Dunes Mobility Integration and Characterization:Developing of a Flexible Volume Computing Method

Coastal dunes are among the most complex interfaces to study in the world. Improving the knowledge of their morphodynamics is essential to better understand the present evolutions and try to anticipate future. The recent use of the new vectors that are drones, UAV and UAS, improves the temporal and spatial resolutions of geomatic data acquired on these environments. Many studies attempt to measure the sedimentary variations that occur from one date to another by the use of differential volumes. In particular, they make it possible to understand the roles of storms, sometimes erosive, as well as the possible morphological responses of associated reconstruction periods. One of the primary methods for calculating volume evolutions is the assessment of a vertical delimitation of the dune toe. However, it is difficult to limit mobile and variable environment, temporally and spatially, to a simple vertical topographic delimitation. This study was realized to estimate the error induced by the use of the vertical threshold method. In the examples that were done, this error was far from being negligible and might in some cases exceed the evolutions of measured volumes. In overcoming this problem, an alternative method was developed. It was the seemingly better adaptability to these mobile environments that are the coastal dunes.

The modern change and evolution tendency of sand coast in the eastern area of Liaodong Gulf

In studying sand beach erosion and protection tactics in Liaoning Province, the authors calculated the wavedata of 27 a Period (1963-1991) at Bayuquan Observation Station in Liaodong Gulf. Together with the beach levellingsand some simple marking stakes monitoring and by having the aid of local annals, the paper analysed the present situationsof the coastline and the causes of sand coastal recession and serious consequences, and then discussed the dynamic processof alongshore sand transport. Simultaneously, based on alongshore sand transport model, oneline cut-and-fill theory anddynamical water model(sea level rise), the authors preliminary estimated beach process for the future in the area.Recently, the coastline is being eroded and 2/3 of the sand coast is subjected to erosion, which the recession rate ofthe individual sector exceed 7. 0 m/a. Coastal erosion has threatened villages, roads, factories and tourist resources. Sealevel rises and the decreasing amount of materials by rivers discharged into the sea and the activities of man, made coast line recession rate accelerate, and cause a great loss of land in the area.

Heavy Minerals Concentration in the Beach Sands of the Uae Northern Coastline

The northern section of the UAE is bordered by the Gulf of Oman’s northern extension (East Coast) and Arabian Gulf’s Eastern extension (northern West Coast). Unlike the rest, the coastline of this section is more or less faced by mountainous areas of various rock types. The beach sands a long this coastline at both sides (East and northern-West) signify some heavy minerals concentration of an important consideration.

Chronology of coastal aeolian deposition and its paleo-environmental implications on the Liuao Peninsula of South China

Coastal dunes are a common geomorphic type in sandy coastal zones.They are a record of the coupled evolutionary processes of the wind and ocean waves.Many coastal dune fields have developed on the east coast of Fujian China and now occur as widespread typical coastal aeolian sand landforms on the Liuao Peninsula,Gulei Peninsula and Dongshan Island,but it is difficult to evaluate the dynamic geomorphologic process of sandy coast due to the lack of systematic and accurate chronological data.In this study,we selected the Hutoushan(HTS)aeolian dune on the Liuao Peninsula as the research object.Optical dating and grain-size analysis were applied to sand samples from the aeolian sequence of a profile of the HTS dune.The results show that the ages of seven samples of this profile were in the range of 37.8–0.19 ka from 4.0 to 0.2 m deep.These correspond to the Marine Isotope Stage 3(MIS3),abrupt climatic change events of 4.2 and 1.1 ka and the Little Ice Age(LIA),respectively.These samples displayed evidence of a longer-term climate trend in this area.The period of formation of this coastal aeolian dune corresponds to a cold and arid climate associated with the East Asia Winter Monsoon(EAWM).Periods of dune fixation and rubification are evidence of a hot and humid climate.Mobilization and stabilization of the aeolian dune is an important characteristic of the coastal evolution in South China since the late Pleistocene.

鄂尔多斯盆地西缘石炭纪羊虎沟组海岸砂坝特征与成因

因对鄂尔多斯盆地西缘石炭纪羊虎沟组海岸砂坝的成因认识不足,阻碍了油藏的进一步开发。在研究区惠探1井、鄂32井、鄂33井、乐1井等取心井的岩心观察和区域地质等资料的基础上,结合岩石粒度分析、测井曲线特征分析和元素分析,对鄂尔多斯盆地西缘羊虎沟组海岸砂坝的沉积特征、砂坝砂体沉积特征和控制因素进行了系统研究。结果表明,研究区砂坝呈条带状沿古隆起聚集,南部的砂坝砂体厚度较大。该结果可为鄂尔多斯盆地羊虎沟组有利区的下一步勘探开发提供有益参考。

珊瑚礁海岸沉积物输运及珊瑚砂岛演变研究综述

珊瑚礁海岸沉积物的输运及珊瑚砂岛的演变研究在我国起步较晚,同时南中国海的珊瑚砂岛是我国重要的海洋空间资源,涉及国家领土主权的核心利益,开展这方面研究具有重要的学术价值和现实意义。综合分析了推移质和悬移质碳酸盐沉积物输运过程及其影响因素,重点介绍了短波、低频长波和海流对沉积物输运的驱动机制,以及粗糙珊瑚对沉积物的遮蔽效应。总结分析了珊瑚砂岛的动态演变规律及其影响因素,并重点介绍了珊瑚砂岛在长期海平面上升和短期风暴潮增强时的演变规律,并提出了今后研究需要关注的方向。

福建海岸沙地5种防护林土壤微生物群落特征

[目的]探明福建海岸沙地不同防护林对土壤微生物群落的影响及机制,为海岸带防护林森林质量提升提供科学依据。[方法]选择5种主要防护林为对象,分别为次生林、木麻黄(Casuarina equisetifolia)人工林、湿地松(Pinus elliottii)人工林、厚荚相思(Acacia crassicarpa)人工林和尾巨桉(Eucalyptus urophylla×E.grandis)人工林,采用磷脂脂肪酸法(Phospholipids fatty acid, PLFA)比较了不同防护林的土壤微生物群落结构。[结果](1)海岸沙地不同防护林土壤中共检测到18种PLFA生物标记,在尾巨桉和次生林中种类最多,湿地松和厚荚相思人工林最少。(2)土壤总磷脂脂肪酸、革兰氏阳性细菌和革兰氏阴性细菌含量均表现为尾巨桉和次生林较高,厚荚相思和木麻黄人工林较低,土壤真菌含量为尾巨桉林最高,丛枝菌根菌含量为次生林最高,真菌和丛枝菌根菌含量在其他防护林间无显著差异。(3)次生林的土壤微生物多样性和均匀度均高于4种人工林。(4)土壤pH、细根碳氮含量为土壤微生物群落的主要影响因子,其次为土壤全氮和硝态氮含量以及凋落物木质素/氮和细根碳氮比。[结论]不同防护林对土壤微生物群落的影响存在显著差异,在海岸带木麻黄防护林中引种尾巨桉和乡土树种,可以增加土壤微生物多样性,提高森林生态功能。

滨海砂路基结构强度控制研究

为实现滨海砂利用率最大化,针对路基结构强度设计指标要求,采用层状弹性体系理论对两侧包边、上覆改良层的滨海砂填芯路基结构强度进行了研究。明确了砂芯模量、改良层模量及改良层厚度对路基结构顶面回弹模量的影响;提出了路基结构强度控制设计理念和技术。室内外试验结果显示,滨海砂材料的CBR强度随着压实度的提高而增长;经压实后的滨海砂满足公路路基对路基填料CBR值的要求,但滨海砂级配不良、黏聚力低,其单纯滨海砂结构表层无法满足路基结构回弹弯沉指标的要求,因此采取双侧包边和上覆改良层结构可充分发挥滨海砂芯的材料强度性能并满足路基结构回弹模量的强度要求。结果表明:路基顶面当量回弹模量分别与滨海砂自身回弹模量、改良层回弹模量及改善层厚度显著相关,由此建立了多元非线性回归经验公式,获取的路基顶当量回弹模量经验解与层状体系结构的理论解相近;经验公式的提出为改良层的材料选择和厚度优化提供了精准、便捷的计算工具,从而有效实现了对路基结构强度的合理控制,为滨海砂在滨海公路建设中的大量利用、降低建设成本、保护生态环境奠定了可靠的理论支撑。

金属砂矿勘查中基本分析项目与地质品位的确定--讨论及建议

基本分析项目与地质品位的确定是金属砂矿勘查中基础且重要的环节,对我国金属类砂矿开发与利用产生直接影响。我国现有砂矿地质品位确定方法存在一定差异性,模糊性或矛盾性,对这些重要问题进行讨论是有必要的。本文以多年来滨浅海金属类砂矿调查经验为基础,结合前人研究成果,介绍目前勘查中砂矿品位的主流表示与计算方法,分析其优缺点,继而提出面向新一轮找矿突破要求的改进方法并探讨其可行性。结果表明:金属砂矿勘查品位确定应遵循与时俱进、正确对待误差、综合评价原则,并寻求勘查成本与勘查风险的最佳结合点。建议不采用传统重矿物淘洗+鉴定方法作为基本分析获得矿物品位,推荐视勘查阶段、勘查主要目的、勘查类型灵活选用重矿物含量(THM%)测定、化学分析法换算、自动矿物分析(如MLA)3种方法作为基本分析项目。圈定矿体的边界品位与最低工业品位可直接利用“重矿物含量”或采用“综合圈矿指标”。应选取重点研究区,将其与传统方法进行对比研究与验证,同时对砂矿勘查技术规范体系相关内容进行广泛深入讨论,寻求共识,以求加快补充修订。

地震作用下滨海岛礁吹填砂地层液化规律及隧道动力响应特性

以厦门地铁3号线工程为依托,通过FLAC 3D软件结合反映混凝土损伤的弹塑性模型建立土-盾构隧道相互作用模型,探究地震作用下吹填砂地层的液化发展规律及盾构隧道动力响应特征。结果表明:在地震荷载作用下,远离盾构隧道处孔隙水压力、有效应力均逐步上升最后趋于稳定,而在盾构隧道附近处有效应力先减小后增大,超孔隙水压力先增大后减小;地震结束时刻管片损伤最大值在拱腰至拱脚之间,但远小于混凝土的破坏限值;地震引起的损伤增量在拱顶与拱底处最小,在拱腰与拱脚附近最大,故拱腰至拱脚处为隧道衬砌结构抗震最不利部分。

海南滨海粉细砂压实特性试验研究

结合海南环岛旅游公路项目,进行了粉细砂的室内物理指标试验、击实试验及粉细砂路基的压实试验。试验结果表明:海南滨海粉细砂以细砂为主,其次为中砂,取样中无粗砂;细砂的最大干密度为1.66~1.69 g/cm^(3),且与不均匀系数呈线性正相关,满足公路下路堤填料的要求。在工程应用方面,粉细砂路基可用双钢轮压实,碾压方式宜采取静压和振压相结合的方式,松铺厚度不宜大于30 cm,碾压遍数宜为6~8遍,可随挖随填。