Reclamation of Coastal Soil Salinity towards Sustainable Rice Production and Mitigating Global Warming Potentials in the Changing Climate

Soil salinity has become a major constraint to rice productivity in the coastal region of Bangladesh, which threatened food security. Therefore, field experiment was conducted at salt stressed Shyamnagor Upazilla of Satkhira district to improve the soil salinity status, sustainable rice production and suppression of global warming potentials. Selected soil amendments viz. trichocompost, tea waste compost, azolla compost and phospho-gypsum (PG) were applied in the field plots one week prior to rice transplanting. In addition, proline solution (25 mM) was applied on the transplanted rice plants at active vegetative stage. Gas samples from the paddy field were collected by Closed Chamber technique and analyzed in by Gas Chromatograph. The 25% replacement of chemical fertilizer (i.e., 75% NPKS) with trichocompost, tea waste compost, Azolla compost and Phospho-gypsum amendments increased grain yield by 4.7% - 7.0%, 2.3% - 7.1% 11.9% - 16.6% and 9.5% - 14.2% during dry boro rice cultivation, while grain yield increments of 5.0% - 7.6%, 2.3% - 10.2%, 12.8% - 15.3% and 10.2% - 15.3% were recorded in wet Aman season respectively, compared to chemically fertilized (100% NPKS) field plot. The least GWPs 3575 and 3650 kg CO2 eq./ha were found in PG Cyanobacterial mixture with proline (T10) and tea waste compost with proline (T8) amended rice field, while the maximum GWPs 4725 and 4500 kg CO2 eq./ha were recorded in NPKS fertilized (100%, T2) and NPKS (75%) with Azolla compost (T5) amended plots during dry boro rice cultivation. The overall soil properties improved significantly with the selected soil amendments, while soil electrical conductivity (EC), soil pH and Na+ cation in the amended soil decreased, eventually improved the soil salinity status. Conclusively, phospho-gypsum amendments with cyanobacteria inoculation and proline solution (25 mM) application could be an effective option to reclaim coastal saline soils, sustaining rice productivity and reducing global warming potentials.

Approach of water-salt regulation using micro-sprinkler irrigation in two coastal saline soils

This study aimed to investigate whether saline silt and sandy loam coastal soils could be reclaimed by micro-sprinkler irrigation.The experiments were run using moderately salt-tolerant tall fescue grass.Micro-sprinkler irrigation in three stages was used to regulate soil matric potential at a 20-cm soil depth.Continued regulation of soil water and salt through micro-sprinkler irrigation consistently resulted in an increasingly large low-salinity region.The application of the three stages of soil wateresalt regulation resulted in an absence of salt accumulation throughout the soil profile and the conversion of highly saline soils into moderately saline soils.There were increases in the plant height,leaf width,leaf length,and tiller numbers of tall fescue throughout the leaching process.The results showed that micro-sprinkler irrigation in three soil water and salt regulation stages can be used to successfully cultivate tall festuca in highly saline coastal soil.This approach achieved better effects in sandy loam soil than in silt soil.Tall fescue showed greater survival rates in sandy loam soil due to the rapid reclamation process,whereas plant growth was higher in silt soil because of effective water conservation.In sandy loam,soil moisture should be maintained during soil reclamation,and in silt soil,soil root-zone environments optimal for the emergence of plants should be quickly established.Micro-sprinkler irrigation can be successfully applied to the cultivation of tall fescue in coastal heavy saline soils under a three-stage soil wateresalt regulation regime.

Soil Salinity and Soil Water Content Estimation Using Digital Images in Coastal Field:A Case Study in Yancheng City of Jiangsu Province,China

Soil is the essential part for agricultural and environmental sciences,and soil salinity and soil water content are both the important influence factors for sustainable development of agriculture and ecological environment.Digital camera,as one of the most popular and convenient proximal sensing instruments,has its irreplaceable position for soil properties assessment.In this study,we collected 52 soil samples and photographs at the same time along the coast in Yancheng City of Jiangsu Province.We carefully analyzed the relationship between soil properties and image brightness,and found that soil salt content had higher correlation with average image brightness value than soil water content.From the brightness levels,the high correlation coefficients between soil salt content and brightness levels concentrated on the high brightness values,and the high correlation coefficients between soil water content and brightness levels focused on the low brightness values.Different significance levels(P)determined different brightness levels related to soil properties,hence P value setting can be an optional way to select brightness levels as the input variables for modeling soil properties.Given these information,random forest algorithm was applied to develop soil salt content and soil water content inversion models using randomly 70%of the dataset,and the rest data for testing models.The results showed that soil salt content model had high accuracy(R_(v)^(2)=0.79,RMSE_(v)=12 g/kg,and RPD_(v)=2.18),and soil water content inversion model was barely satisfied(R_(v)^(2)=0.47,RMSE_(v)=3.04%,and RPD_(v)=1.38).This study proposes a method of modeling soil properties with a digital camera.Combining unmanned aerial vehicle(UAV),it has potential popularization and application value for precise agriculture and land management.

Microbial diversity in the saline-alkali soil of a coastal Tamarix chinensis woodland at Bohai Bay, China

Soil salinization or alkalization is a form of soil desertification. Coastal saline-alkali soil represents a type of desert and a key system in the network of ecosystems at the continent-ocean interface. Tamarix chinensis is a drought-tolerant plant that is widely distributed in the coastal saline-alkali soil of Bohai Bay, China. In this study, we used 454 pyrosequencing techniques to investigate the characteristics and distribution of the microbial diversity in coastal saline-alkali soil of the T. chinensis woodland at Bohai Bay. A total of 20,315 sequences were obtained, representing 19 known bacterial phyla and a large proportion of unclassified bacteria at the phylum level. Proteobacteria, Acidobacteria and Actinobacteria were the predominant phyla. The coverage of T. chinensis affected the microbial composition. At the phylum level, the relative abundance of y-Proteobacteria and Bacteroidetes decreased whereas Actinobacteria increased with the increasing coverage of T. chinensis. At the genus level, the proportions of Steroidobacter, Lechevalieria, Gp3 and Gp4 decreased with the increase of the vegetation coverage whereas the proportion of Nocardioides increased. A cluster analysis showed that the existing T. chinensis changed the niches for the microorganisms in the coastal saline-alkali soil, which caused changes in the microbial community. The analysis also distinguished the microbial community structure of the marginal area from those of the dense area and sparse area. Furthermore, the results also indicated that the distance to the seashore line could also affect certain groups of soil bacteria in this coastal saline-alkali soil, such as the family Cryomorphaceae and class Flavobacteria, whose population decreased as the distance increased. In addition, the seawater and temperature could be the driving factors that affected the changes.

Effects of water application intensity of microsprinkler irrigation on water and salt environment and crop growth in coastal saline soils

Laboratory and field experiments were conducted to investigate the effects of water application intensity（WAI） on soil salinity management and the growth of Festuca arundinacea（festuca） under three stages of water and salt management strategies using microsprinkler irrigation in Hebei Province, North China. The soil water content（è） and salinity of homogeneous coastal saline soils were evaluated under different water application intensities in the laboratory experiment. The results indicated that the WAI of microsprinkler irrigation influenced the è, electrical conductivity（ECe） and p H of saline soils. As the WAI increased, the average values of è and ECe in the 0–40 cm profile also increased, while their average values in the 40–60 cm profile decreased. The p H value also slightly decreased as depth increased, but no significant differences were observed between the different treatments. The time periods of the water redistribution treatments had no obvious effects. Based on the results for è, ECe and p H, a smaller WAI was more desirable. The field experiment was conducted after being considered the results of the technical parameter experiment and evaporation, wind and leaching duration. The field experiment included three stages of water and salt regulation, based on three soil matric potentials（SMP）, in which the SMP at a 20-cm depth below the surface was used to trigger irrigation. The results showed that the microsprinkler irrigation created an appropriate environment for festuca growth through the three stages of water and salt regulation. The low-salinity conditions that occurred at 0–10 cm depth during the first stage（-5 k Pa） continued to expand through the next two stages. The average p H value was less than 8.5. The tiller number of festuca increased as SMP decreased from the first stage to the third stage. After the three stages of water and salt regulation, the highly saline soil gradually changed to a low-saline soil. Overall, based on the salt desalinization, the microsprinkler irrigation and three stages of water and salt regulation could be successfully used to cultivate plants for the reclamation of coastal saline land in North China.

Sufficiency and Deficiency Indices of Soil Available Zinc for Rice in the Alluvial Soil of the Coastal Yellow Sea

To determine the sufficiency and deficiency indices of soil available Zn by the Agro Services International （ASI） method （ASI-Zn） for Zn fertilizer recommendation in rice production in the alluvial soil of the coastal Yellow Sea, the relationship between relative rice yield and soil available ASI-Zn concentration was analyzed from a ten-field experiment with various soil test classes ranging from low to high fertility in 2005 and 2006, and nine Zn fertilizer application rates （0, 7.5 15, 22.5, 30, 37.5, 45, 52.5 and 60 kg Zn/ha） arranged at random with three replications in each field. There was a significant quadratic relationship between soil available ASI-Zn and rice yield, and a significant linear relationship between soil available ASI-Zn concentration and Zn fertilization rate. For rice variety Wuyujing 3, soil available ASI-Zn was deficient when the value was at lower than 1 mg Zn/L, low at 1 to 2 mg Zn/L, sufficient at 1 to 2 mg Zn/L, excessive at higher than 7.5 mg Zn/L. Thus, Zn fertilizer recommendation could be done according to the sufficiency and deficiency indices of soil ASI-Zn. For most of alluvial soils of the coastal Yellow Sea in the study, the available ASI-Zn was lower than 1 mg Zn/L, and then the optimum application rate of Zn fertilizer was about 20 kg Zn/ha.

Effect of different water application intensity and irrigation amount treatments of microirrigation on soil-leaching coastal saline soils of North China

In coastal regions, Bohai Gulf is one of the most affected areas by salinization. To study the effects of mocrosprinkler irrigation on the characteristics of highly saline sandy loam soil（ECe（saturated paste extract）=22.3 d S m^–1; SAR（sodium adsorption ratio）=49.0） of North China, a laboratory experiment was conducted. Five water application intensity（WAI） treatments（1.7, 3.1, 5.3, 8.8, and 10.1 mm h^–1）, five irrigation amount（IA） treatments（148, 168, 184, 201, and 223 mm） and three time periods of water redistribution（0, 24 and 48 h） were employed in the study. A compounding microsprinkler system was used for the WAI treatments, and a single microsprinkler was used for the IA treatments. The results indicated that, as soil depth increased, soil water content（θ） increased and then slightly decreased; with WAI and IA consistently increasing, the relatively moist region expanded and the average θ increased. Meanwhile, soil ECe increased as soil depth increased, and the zone with low soil salinity expanded as WAI and IA increased. Although the reduction of the average SAR was smaller than that of the average electrical conductivity of the ECe, these variables decreased in similar fashion as WAI and IA increased under microsprinkler irrigation. The average p H decreased as soil depth increased. Longer time periods of water redistribution led to lower salinity and slight expansion of the SAR zone. Considering the effects of leached salts in coastal saline soils, greater WAI and IA values are more advantageous under unsaturated flow conditions, as they cause better water movement in the soil. After leaching due to microsprinkler irrigation, highly saline soil gradually changes to moderately saline soil. The results provide theoretical and technological guidance for the salt leaching and landscaping of highly saline coastal environments.

Reclamation of Coastal Saline Soils by Bnilding Dykes for Freshwater Fish－Farming

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Effects of Reclamation on Soil Carbon and Nitrogen in Coastal Wetlands of Liaohe River Delta,China

To evaluate the influence of wetland reclamation on vertical distribution of carbon and nitrogen in coastal wetland soils, we measured the soil organic carbon(SOC), soil total nitrogen(STN) and selected soil properties at five sampling plots(reed marsh, paddy field, corn field, forest land and oil-polluted wetland) in the Liaohe River estuary in September 2013. The results showed that reclamation significantly changed the contents of SOC and STN in the Liaohe River estuary(P < 0.001). The SOC concentrations were in the order: oil-polluted wetland > corn field > paddy field > forest land > reed marsh, with mean values of 52.17, 13.14, 11.46, 6.44 and 6.16 g/kg, respectively. STN followed a similar order as SOC, with mean values of 1351.14, 741.04, 632.32, 496.17 and 390.90 mg/kg, respectively. Interaction of reclamation types and soil depth had significant effects on SOC and STN, while soil depth had significant effects on SOC, but not on STN. The contents of SOC and STN were negatively correlated with pH and redox potential(Eh) in reed marsh and corn field, while the SOC and STN in paddy field had positive correlations with electrical conductivity(EC). Dissolved organic carbon(DOC), ammonium nitrogen(NH_4^+-N) and nitrate nitrogen(NO_3~–-N) were also significantly changed by human activities. NH_4^+-N and NO_3~–-N increased to different degrees, and forest land had the highest NO_3~–-N concentration and lowest DOC concentration, which could have been caused by differences in soil aeration and fertilization. Overall, the results indicate that reed harvest increased soil carbon and nitrogen release in the Liaohe River Estuary, while oil pollution significantly increased the SOC and STN; however, these cannot be used as indicators of soil fertility and quality because of the serious oil pollution.

Effects of Tamarisk shrub on physicochemical properties of soil in coastal wetland of the Bohai Sea

There are many different and even controversial results concerning the effects of Tamarisk on the physicochemical properties of soil. A year-round monitoring of soil salinity, p H and moisture is conducted beneath the Tamarisk shrub in a coastal wetland in the Bohai Sea in China, to ascertain the effects of Tamarisk on the physicochemical properties of soil in coastal wetland. Compared with the control area, the soil moisture content is lower around the area of the taproot when there is less precipitation in the growing season because of water consumption by Tamarisk shrub. However, the soil moisture content is higher around the taproot when there is more precipitation in the growing season or in the non-growing period because of water conservation by the rhizosphere. The absorption of salt by the Tamarisk shrub reduces the soil salinity temporarily, but eventually salt returns to the soil by the leaching of salt on leaves by rainfall or by fallen leaves. The annual average soil moisture content beneath the Tamarisk shrub is lower than the control area by only 6.4%, indicating that the Tamarisk shrub has little effect on drought or water conservation in soils in the temperate coastal wetland with moderate annual precipitation. The annual average salinity beneath the Tamarisk shrub is 18% greater than that of the control area, indicating that Tamarisk does have an effect of rising soil salinity around Tamarisk shrubs. The soil p H value is as low as 7.3 in summer and as high as 10.2 in winter. The p H of soil near the taproot of the Tamarisk shrubs is one p H unit lower than that in the control area during the growing season. The difference in p H is less different from the control area in the non-growing season, indicating that the Tamarisk shrub does have the effect of reducing the alkalinity of soil in coastal wetland.

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.

Feasibility and Prospect about the Cultivation of Apocynum venetum L. in Coastal Salt-affected Soils

[Objective]The aim of this paper was to analyze the feasibility and prospect of Apocynum venetum L.cultivation in coastal salt-affected soils.[Method]The habitat and distribution of Apocynum venetum L.in coastal area of north China were studied.A method to integrate the charicteristics of Apocynum venetum L.（Luobuma） with the utilization of salt-affected soils in this region was proposed.[Result]The introduction,domestication and growth of plants on coastal salt-affected soils can realize the protection of endangered wild species,and achieve the purpose of improving soil.The characteristics of Apocynum venetum L.can produce optimum economic and ecological benefits.[Conclusion]The implementation will provide references for the protection and exploitation of wild plant,and it is of positive significance for the integration of soil and plant resources.

The impact of land use change on quality evolution of soil genetic layers on the coastal plain of south Hangzhou Bay

Land use change plays an important part in the studies of global environmental change and regional sustainable development. The change of soil quality can particularly reflect the impacts of human socio-economic activities on environment. Taking the coastal plain of south Hangzhou Bay as a study case, we analyzed the effects of land use changes on organic matter （OM）, total nitrogen （TN）, total phosphorus （TP）, available phosphorus （AP）, available potassium （AK）, total salinity （TS）, pH value in soil genetic layers, and assessed soil quality change related to different land use types from 1982 to 2003. The results show that： （1） The general change tendency of soil quality in the coastal plain of south Hangzhou Bay declined obviously in A layer and slightly rise in B （or P） layer and C （or W） layer. The contents of TP decreased generally in all soil genetic layers, but the variety difference of other soil quality indices was relatively great. （2） The change of soil quality in the areas where land use changed is far more remarkable than that with land use unchanged. The value of quality variety is A layer 〉B （or P） layer 〉C （or W） layer. （3） The changes of soil tillage, cultivation, fertilization, irrigation and drainage activities related to land use may make some soil-forming processes disappeared and bring in other new processes which will affect the soil quality and soil genetic layers directly.

Coastal afforestation effects on soil properties at Hatiya in Bangladesh

An exploratory study was conducted in the coastal plantation （12- and 17-year-old Sonneratia apetala） of Char Alim and Char Piya and on their adjacent barren lands at Char Rehania and Char Nurul Islam in Hatiya of Noakhali district, in Bangladesh to determine afforestation effects on soil properties. At soil depths of 0-10, 10-30 and 30-40 cm across three different land strips viz. inland, middle and sea side in 12- and 17-year-old keora （Sonneratia apetala） plantations, soil moisture, particle density, organic matter and C, total N, pH, available P, K, Na, Ca and Mg were significantly （p≤0.05, p≤0.01, p≤0.001） higher, and soil salinity significantly （p〈0.001） lower than that in their adjacent barren lands. Soil moisture, particle density, organic matter and C, total N, pH, soil salinity, available P, K, Na, Ca and Mg of surface soil in Char Alim plantation at inland were 31.09%, 2.24 g.cm^-3, 2.41%, 4.14%, 0.58%, 7.07, 0.09 dS＇cm^-1, 28.06 mg.L^-1, 0.50 mg-L^- 1 11.5 mg-L^-1, 3.30 mg·L^-1 and 2.7 mmol.kg^-1, respectively. Their corresponding values for the same depth and land position at adjacent Char Rehania barren land were 16.69%, 1.25g.cm^-3, 0.43%, 0.74%, 0.25%, 6.57, 0.13 dS.cm^-1, 13.07mg-L^-1, 0.30 mg.L^-1, 1.4 mg.L^-1, 0.30 mmol·kg^-1 and 0.50 mg.L^-1, respectively. Soil moisture, particle density, organic matter and C, total N, pH, available P, K and Ca decreased, and soil salinity, available Na and Mg increased from inland towards sea side in the plantations. Although soil texture did not differ in most soil depths between plantation and adjacent barren land, proportion of sand particle was significantly （p≤0.01） lower and silt particle significantly （p〈0.001） in the plantations higher than that in their adjacent barren lands. In the study, evaluation of all the parameters was also done for the other pair of lands.

Comparison of Soil Nutritional Status between Different Muscat Hamburg Vineyards in Coastal Areas of Tianjin

To study the effects of different soil conditions on winter nutrient storage of Muscat Hamburg branches,this study compared the soil texture,bulk density,total salt content and soil K,Ca,Na,Mg and total Fe contents of Muscat Hamburg vineyards in Ninghe District and Hangu District,Binhai New Area of Tianjin and analyzed the soluble sugar and soluble protein contents in one-year-old vine branches. The results showed that the soil p H was lower,and the soil K,Ca and total salt( 0. 445%) contents were higher in the vineyard of Ninghe District than those in the vineyard of Hangu District. There were no significant differences in the soil Mg,Fe and Na contents between the vineyards in the two regions. The soil of the vineyard in Ninghe District is medium loam,and that in Hangu District is heavy loam. In short,all the soil indicators of the vineyard in Ninghe District were better than those in Hangu District except the indicator of soil salt content. The soluble sugar and soluble protein contents of one-year-old vine branches differed significantly between the two regions.

Fertilization Affects Biomass Production of Suaeda salsa and Soil Organic Carbon Pool in East Coastal Region of China

Land use practice significantly affects soil properties. Soil is a major sink for atmospheric carbon, and soil organic carbon （SOC） is considered as an essential indicator of soil quality. The objective of this study was to assess the effects of N and P applied to Suaeda salsa on biomass production, SOC concentration, labile organic carbon （LOC） concentration, SOC pool and carbon management index （CMI） as well as the effect of the land use practice on soil quality of coastal tidal lands in east coastal region of China. The study provided relevant references for coastal exploitation, tidal land management and related study in other countries and regions. The field experiment was laid out in a randomized complete block design, consisting of four N-fertilization rates （0 （NO）, 60 （N1）, 120 （N2） and 180 kg ha-1 （N3））, three P-fertilization rates （0 （P0）, 70 （P1） and 105 kg ha-~ （P2）） and bare land without vegetation. N and P applied to S. salsa on coastal tidal lands significantly affected biomass production （above-ground biomass and roots）, bulk density （Pb）, available N and P, SOC, LOC, SOC pool and CMI. Using statistical analysis, significantly interactions in N and P were observed for biomass production and the dominant factor for S. salsa production was N in continuous 2-yr experiments. There were no significant interactions between N and P for SOC concentration, LOC concentration and SOC pool. However, significant interaction was obtained for CMI at the 0-20 cm depth and N played a dominant role in the variation of CMI. There were significant improvements for soil measured attributes and parameters, which suggested that increasing the rates of N and P significantly decreased Pb at the 0-20 cm depth and increased available N and P, SOC, LOC, SOC pool as well as CMI at both the 0-20 and 20-40 cm depth, respectively. By correlation analysis, there were significantly positive correlations between biomass （above- ground biomass and roots） and SOC as well as LOC in 2010 and 2011 across all soil depth, respectively. The treatment with N at 180 kg ha-~ and P at 105 kg ha-1 was superior to the other treatments. The results from the 2-yr continuous experiments indicated that, in short-term, there were a few accumulation of SOC and LOC concentrations by means of N and P application to S. salsa, whereas in the long run, S. salsa with N and P application was recommended for coastal tidal lands because of its great potential of carbon sequestration, improvements of soil nutrition status and promotion of soil quality.

Disturbance Legacy on Soil Carbon Stocks and Stability within a Coastal Temperate Forest of Southwestern British Columbia, Canada

Although it has been recognized that soils play a critical role in carbon storage and that coastal temperate forests have considerable potential to sequester soil organic carbon (SOC), studies related to SOC stocks and stability are scarce in these ecosystems. Forest disturbances may leave legacies on SOC properties and may further compromise SOC storage capacity of these ecosystems. In the Pacific Spirit Regional Park of southwestern British Columbia, we compared SOC stocks and stability among three second-growth forests that have been affected by disturbances of different magnitudes. We collected data on soil chemical and physical properties to estimate SOC content and assess SOC stability. We found that SOC stocks in the forest characterized by low magnitude disturbance were greater than those of the forest characterized by high magnitude disturbance (8.2 ± 1.3 kg·Cm-2 versus 5.3 ± 0.1 kg·Cm-2 to 30 cm depth). SOC was less stable in the highly disturbed forest and subsequent vegetation changes might have further reduced SOC stability. Our results provide insight into the role of disturbance history in the current SOC storage capacity of coastal temperate rainforests of British Columbia.

燕麦对滨海盐渍土的适应性及纳盐改土效果

为探索燕麦植株对滨海盐渍土的适应性及纳盐改土效果,本试验以白燕2号为材料,在东营的3种类型滨海盐渍土上(轻度、中度、重度)设6个区顶凌播种,观测燕麦农艺性状及田间覆盖率,测定燕麦全株及籽粒产量和燕麦不同部位及收获期0~20 cm土层土壤可溶性盐和Na+含量。结果表明,白燕2号在3种滨海盐渍土壤中均能生长,但适应程度不同,全株产量为3.320~18.780 t·hm^(-2),籽粒产量为0.456~4.106 t·hm^(-2),基本趋势为轻度盐渍土>中度盐渍土>重度盐渍土;燕麦利用植株的储盐能力将盐渍土部分可溶性盐移出土壤,燕麦全株移出可溶性盐量为0.161~1.508 t·hm^(-2),籽粒移出可溶性盐量为2.961~43.242 kg·hm^(-2);春季返盐高峰后,裸露地土壤表层盐表聚严重,试验区燕麦收获期0~20 cm土层土壤可溶性盐和Na+含量均有不同程度的降低;燕麦植株不同部位的可溶性盐、Na+分配结果显示,燕麦秸秆含盐量最高,达96.954 g·kg^(-1),是根的3.576倍、籽粒的12.803倍,秸秆内Na+含量最高,为20.242 g·kg^(-1),是根的5.190倍、籽粒的55.763倍。可见,燕麦植株通过在不同部位间合理分配可溶性盐和Na+来提高燕麦的耐盐性。综上表明,燕麦植株通过吸盐、储盐、收获移盐等纳盐过程对滨海盐渍土的改良效果明显。

凋落物输入变化对黄河三角洲柽柳人工林土壤有机碳及其组分的影响

为探究凋落物输入变化对土壤有机碳库的影响,明确凋落物对森林生态系统土壤碳循环的作用,以黄河三角洲滨海盐碱地柽柳人工林为研究对象,通过设置添加凋落物(LA)、去除凋落物(LR)和对照(CK)3种处理方法,分析凋落物不同输入变化对土壤理化性质、土壤有机碳及其组分的影响。结果表明:凋落物添加和去除处理影响土壤理化性质的变化,与对照相比,添加凋落物降低了土壤密度和含盐量,增加了土壤含水量和养分(全氮、全磷、全钾),而去除凋落物则相反。3种处理对土壤有机碳(SOC)及其储量以及活性有机碳组分的影响一致,均表现为LA处理影响最大,LR处理影响最小,其中LA处理比CK增加了SOC质量分数及储量,但增加不显著;LR处理则显著降低了SOC质量分数及其储量,土层深度(d)0<d≤10 cm土层,LR处理比CK处理的SOC质量分数及其储量分别显著降低了34.93%、12.66%,10 cm<d≤20 cm土层,LR处理比CK处理的SOC质量分数及其储量分别显著降低了24.27%、16.13%。LA处理的土壤SOC及可溶性有机碳(DOC)、易氧化有机碳(EOC)、微生物量碳(MBC)质量分数均出现明显的表聚现象,而LR处理影响则不显著,且DOC和MBC则出现随土层深度增加而增大的趋势。土壤惰性有机碳(ROC)质量分数在不同土层间存在差异,0<d≤10 cm土层,各处理表现为LA>CK>LR,10 cm<d≤20 cm土层,各处理则表现为CK>LA>LR,而在CK和LR处理出现随土层增加而增加的趋势,偏于向土层下方积累。土壤密度(BD)与SOC及其各组分呈负相关,而土壤含水量(WC)、全氮、全磷与SOC及EOC、MBC、DOC质量分数呈极显著正相关(P<0.01)。因此,不同处理方式及不同土层深度的土壤密度、全氮质量分数和土壤含水量是影响SOC及组分变化的主要环境因子。

海相软土力学特性及其对城市地下轨道交通工程的影响分析

中国东部沿海地区广泛分布的海相软土,因其独特的力学特性和地质成因,对城市轨道交通建设产生了重大影响。针对中国五个典型区域的11个城市中的海相软土进行详细分析,旨在深入理解其地质成因、颗粒组成、矿物成分和微观结构特点,并总结其物理力学性质、蠕变性和触变性等关键工程特性。通过典型工程案例分析,揭示了城市轨道交通建设在海相软土地层中遭遇的工程风险,并基于实例分析,提出一系列海相软土地区轨道交通工程设计和施工的指导建议。特别强调有效控制和管理相关风险的策略,包括土体加固、改良技术和智能化监测手段的应用。该研究为理解海相软土的复杂工程行为提供了新的视角,对推进沿海地区城市轨道交通建设的安全与稳定具有重要意义。