Inland Soils Research Articles

The Origin and Nature of Magnetic Particles From Soils and Sediments Constrained by Hydrodynamics and Geochemistry Around a Tropical Lagoon System

AbstractMagnetic iron oxides are commonly enriched in soils and sediments on Earth's surface. Magnetic properties are widely employed in soil taxonomy, sediment tracing and paleoclimate reconstruction as indicators of associated pedogenic and depositional processes. However, in coastal regions, frequent shifts in pedogenesis and diagenesis accompanied by changes in hydrodynamic and geochemical conditions from land to sea can influence the formation and preservation of magnetic particles in sediment sequences. To discern the origin and nature of magnetic particles driven by these processes, we systematically examined soils and sediments around a tropical lagoon that has been closing for two hundred years. We found that the finest superparamagnetic particles are enriched along with hematite from inland soils with high‐Fe and high‐Al backgrounds, which was driven by pedogenesis. Single‐domain ferrimagnetic particles are enriched along with amorphous iron oxides in the lagoon with high‐Mg and high‐Mn backgrounds, which was driven by early diagenesis in quiet and reducing depositional environments. Coarse titanomagnetite particles are strongly enriched in inshore sediments with high‐Si and high‐Ti backgrounds, which was driven by seawater elutriation. However, magnetic particles in barrier bar soils have mixed features depending on the neighboring environment. Identifying magnetic particles derived from different soils and sediments in tropical coastal regions can assist in tropical coastal paleoclimate and paleoenvironment reconstruction on the basis of magnetic properties along coastal sediment sequences.

Vigna marina as a Potential Leguminous Cover Crop for High Salinity Soils

The beach bean (Vigna marina) exhibits robust growth in habitats characterised by sandy substrates, limited nutrient availability, and elevated saline levels. The utilisation of V. marina, a potentially beneficial leguminous cover crop, allows for its cultivation in regions characterised by soil salinity, hence facilitating the alleviation of environmental stress and the promotion of nitrogen fixation within the soil. A study assessed the feasibility of V. marina as a leguminous cover crop, in which this legume was cultivated in both coastal and inland soils. Pueraria javanica and Mucuna bracteata, widely recognised as established leguminous cover crops, were used as the control in this experiment. The observations involved were total plant biomass, nitrogenase activity, and leaf chlorophyll content of the host plants. The experiment consisted of five replicates arranged in a randomised complete block design, respectively. The effects of commercialised rhizobial compost on the development of the leguminous plants planted in both plots were also investigated. The results indicated that V. marina flourished in coastal and inland soils with the highest leaf chlorophyll concentration throughout the eight weeks of growth. It showed that V. marina has the potential to outperform the other two established leguminous cover crops when planted in highly salinised soils. The results also showed evidence that V. marina was an excellent potential leguminous cover crop, especially for any agricultural plots of high salinity soils, compared to the other two well-established leguminous cover crops, P. javanica and M. bracteata.

The role of tidal creeks in shaping carbon and nitrogen patterns in a Chinese salt marsh

Tidal creeks play a crucial role in lateral transport of carbon and nutrients from tidal salt marshes. However, the specific impact of tidal creek development on carbon and nutrient distribution within the marsh remains poorly understood. The objective of this study is to assess the influence of lateral tidal flooding through the tidal creeks on the spatial distribution of carbon and nitrogen fractions in the soils of a Chinese temperate salt marsh. We conducted a comprehensive analysis of the relative variations in different carbon and nitrogen fractions, along with soil physicochemical and microbial indicators, between the bank soil of the tidal creek and its lateral inland soils across high, middle, and low flats. Our findings highlight that tidal creek development significantly affects the middle flat, leading to substantial variations in organic carbon and total nitrogen. The low flat mainly experiences changes in dissolved inorganic carbon levels. Furthermore, a lateral increase in microbial biomass is observed in the middle flat, indicating that the significantly lower SOC in the middle flat might be ascribed to enhanced microbial decomposition. The lateral enrichment of dissolved inorganic carbon in the low flat is possibly related to the nearshore location and/or abiotic adsorption in inorganic carbon sequestration. Overall, this study demonstrates the critical role of tidal creek development in shaping the distribution patterns of carbon and nitrogen fractions in tidal salt marshes.

Topsoil Carbon Stocks in Urban Greenspaces of The Hague, the Netherlands

Urbanization influences soil carbon (C) stocks and flows, which, in turn, affect soil-derived ecosystem services. This paper explores soil C storage in urban greenspaces in the Dutch city of The Hague along a transect from the suburban seaside towards the city centre, reflecting a toposequence from dune to peaty inland soils. C storage and C mineralisation potential were evaluated in relation to soil type and greenspace categories. Several soil-quality characteristics were measured, including dissolved organic C, pH, electrical conductivity, nitrogen, phosphorus, sulphur, calcium carbonate, and the water-holding capacity of the soil to evaluate what drives soil C storage in the urban context. The total SOC storage of the upper 30 cm of the greenspaces in The Hague (20.8 km2 with 37% greenspace) was estimated at 78.4 kt, which was significantly higher than assumed given their soil types. Degradability of soil organic matter in laboratory batch tests varied between 0.2 and 3 mg C gSOC−1 day−1. Degradability was highest in the seaside dune soils; however, extrapolated to the topsoil using the bulk density, topsoil C mineralization was higher in the urban forest. Soils beneath shrubs appeared to be hotspots for C storage, accounting for only 13% of the aerial cover but reflecting 24% of the total C storage. Land ownership, land use, greenspaces size, litter management and soil type did not result in significantly different C stocks, suggesting that processes driving urban soil C storage are controlled by different factors, namely land cover and the urbanization extent.

Salinization of coastal saline-alkali soil might enhance H2S release by affecting H2S-related bacterial communities

Bacterial metabolism can result in the production and release of hydrogen sulfide (H2S), a reductive gas, in soils. Hydrogen sulfide-releasing bacteria (HSRB) assimilate organic sulfur or dissimilate sulfate to generate and release H2S, whereas H2S-oxidizing bacteria (HSOB) oxidize H2S generated by themselves or other bacteria to soluble sulfate resulting in sulfur retention in soil. However, the effects environmental factors such as electrical conductivity on both these bacterial groups and H2S release remain unclear; some key processes such as H2S oxidation also remain underexplored. In this study, we found that high electrical conductivity in coastal saline-alkali soil affects these bacterial communities, especially HSRB, potentially enhancing H2S release. The “sink” of H2S gas, represented by sulfidic sulfur (concentration, 0.2–3.4 nmol/g) in coastal saline-alkali and inland soils, was determined using the methylene blue method, and found to be positively correlated with soil electrical conductivity, suggesting that more H2S gas potentially volatilized from salinized soil. We then revealed that the proportion of HSRB clones was correlated positively and significantly with the electrical conductivity and sulfidic sulfur of soil, but not with the pH or sulfur source. Further, 16S rRNA gene sequence comparison indicated significantly reduced richness and diversity of bacterial communities and considerably altered the composition of dominant bacterial populations in coastal saline-alkali soil. The phyla Proteobacteria, Bacteroidetes, and Gemmatimonadetes accounted for 38 %, 30.1 %, and 11.1 % and for 28 %, 12.9 %, and 2.5 % of the bacterial populations in coastal saline-alkali and inland soil, respectively. PICRUSt analysis showed that the richness of genes encoding the key H2S oxidation enzymes, sulfide:quinone reductase and sulfate hydrolase, was decreased significantly and negatively correlated with the detected sulfidic sulfur. These enzymes are usually expressed by HSOB in coastal saline-alkali soil, implying a low sulfide oxidation capacity. These results indicate that the number of HSRB is increased whereas the ability of H2S oxidation is decreased in coastal saline-alkali soil, which might lead to enhanced H2S release. Overall, this study provides new insights for understanding the sulfur biological cycle in saline-alkali soils.

Trace-elements evaluation of composted municipal solid wastes used in dry season production of tomato (Lycorpersicum esculentus) in an inland valley soils of Delta State, Nigeria

Trace-elements evaluation of composted municipal solid wastes used in dry season production of tomato (Lycorpersicum esculentus) in an inland valley soils of Delta State, Nigeria

A High-Resolution Digital Elevation Model in Combination With Water Table Depth and Continuous Soil Redox Potential Measurements Explain Soil Respiration and Soil Carbon Stocks at the ICOS Site Sorø

Quantification of activity data and emission factors for carbon (C) in inland wetland mineral soils (IWMS) lack suitable low cost indicators for key soil C processes in temperate forests. In a beech (Fagus sylvatica L.) forest near Sorø, Denmark, SOC stocks and the risk of losing pre-drainage legacy SOC were studied using a digital elevation model (0.4 m resolution), redox potential and soil respiration measurements. The results were compared with a digitized legacy soil map used in the national GHG reporting to UNFCCC. In upland, flat and sloping terrain, an aerobic soil environment (Eh > 400 mV) prevailed throughout most of the year, but in a peat-filled topographic depression (TD) anaerobic conditions (Eh < 400 mV) fully or sporadically occurred in the growing season, controlled by the ditching-affected water table. The relief included SOC rich TDs making up 18.9% of the area based on the “Filled sink” algorithm (Saga GIS). In contrast, the peat cover on the legacy soil map was 8.2%. Furthermore, the mapped peat polygons were offset from the TDs defined by the DEM. The SOC stocks at 0–40 cm depth outside TDs (least squares mean 8.4 ± sem 0.3 kg C m−2) were significantly lower than within TDs (11.9 ± sem 0.5 kg C m−2). Average annual soil respiration increased linearly with the SOC stock by 0.06 kg C per kg SOC up to a SOC stock of 11 kg C m−2 to 20 cm depth, and a SOC loss of 0.23 ± se 0.10 kg C m−2 yr−1 was indicated inside the TD areas, close to the IPCC estimate of 0.26 kg C m−2 yr−1 for drained organic soils under forest. Our results show that continuous sensor-based monitoring of redox potential and shallow water tables linked with high-resolution DEMs offer the possibility to estimate the spatial extent of inland wetland mineral soils and their status as aerobic or anaerobic as indicated by iron rods with higher accuracy than previously. This underpins the potential use of such data for activity data mapping in Tier 3 greenhouse gas reporting.

Early Performances of Topaz Gen-1 Tenera Clones in Clonal Trials and Commercial Plots in Indonesia

Asian Agri’s oil palm research station’s (OPRS-Topaz) breeding programme involves the complementary development of both seedling and clonal planting materials. From 2010-2018, a total of 18 clonal trials and 890 hectares of commercial clonal plots were established in two provinces (North Sumatra, Riau) and on three major soil types (volcanic, inland, peat). This paper reports on the early performances of the clones in the latter sites. Comparatively, elite clones only achieved 82 per cent and 85 per cent of their ortet fresh fruit bunch (FFB) and crude palm oil (CPO) yields, respectively. Analysis undertaken in five of the oldest mineral soil trials indicated either a negative or very low positive correlation between clone and ortet FFB yield, but correlations of oil to bunch (O/B) and annual height increment (Hi) were positive and highly significant, confirming the better heritability of the latter two parameters and their suitability as criteria for ortet selection. In clonal trials, the highest yields were obtained on inland soils in Riau province, with elite clones recording average peak FFB and CPO yields of 45.1 tonnes per hectare and 11.6 tonnes per hectare, respectively. Slightly lower yields were attained on volcanic soils (36.2 tonnes FFB/ha; 9.9 tonnes CPO/ha) and on deep peat (32.6 tonnes FFB/ha; 8.5 tonnes CPO/ha) in North Sumatra. However, as the latter two sites contained some younger trials, they may have yet to achieve their maximum potential. O/B values also differed for the same clones planted on three different soil types. On average, oil content of clones planted on peat was approximately 3 percentage points lower than their counterparts planted on either inland or volcanic soils. In all nine trials which included DxP seedling controls, the top five clones recorded higher CPO yield over their seedling controls by 7-47 per cent. However, these results should be interpreted with caution as all the DxP seedling controls belonged to the same generation as the clones. Their true yield superiority can only be ascertained when evaluated against the latest improved Topaz Series 4 DxP crosses. Nevertheless, nine clones showed good potential for commercial scale propagation, having high CPO yield (9.5 tonnes/ha), O/B (32 %) and good adaptability and consistency in performance over a wide range of sites. Performances of untested clones (directly planted in commercial plots without evaluation in clonal trials) followed the same trend as in clonal trials. Highest yields were recorded on inland soils (39.4 tonnes FFB/ha), followed by volcanic (30.8-36.0 tonnes FFB/ha) and peat soils (27.1-29.8 tonnes FFB/ha). Likewise, as some of the latter commercial plantings were only 5-6 years of age, it is likely that their peak yields have yet to be attained. Census conducted from 2014 to 2016 indicated a low incidence of palms with mantled fruit, averaging 3.3 per cent in clonal trials and only 0.3 per cent in commercial plantings. Such acceptable to low abnormality levels are a reflection of the good quality control practices adopted by AA’s tissue culture laboratory. Keywords: Clones, height increment, oil to bunch, oil palm, tissue culture.

Effects of NaCl stress on the biochemical substances in Bt cotton as well as on the growth and development and adult oviposition selectivity of Helicoverpa armigera

BackgroundRecently, due to the development of food security strategies, cotton has been planted in inland saline-alkali dry soils or in coastal some saline-alkali soils in China. Under the condition, to comprehensively prevent and control Helicoverpa armigera in cotton fields with saline-alkali soils, it is important to study the larval growth and development of H. armigera and to study adult oviposition selectivity in H. armigera adults that feed on NaCl-stressed cotton plants.ResultsIn this study, Bt cotton GK19 was used for the experimental group and its nontransgenic parent Simian 3 was used for the control to study the effects of biochemical substances in cotton as well as larval growth and development and adult oviposition selectivity of H. armigera. The experiments were performed by growing cotton indoors under NaCl stress at concentrations of 0 mmol·L− 1, 75 mmol·L− 1 and 150 mmol·L− 1, respectively. The results showed that the expression of Bt protein was significantly inhibited for NaCl-stressed Bt cotton. The content of soluble protein and K+ in the leaves of cotton were decreased, while the content of gossypol and Na+ were increased. In addition, the 5th instar H. armigera larvae exhibited shorten the life span in a 13-day trial period. Under enclosure treatments and at different female densities, the adult oviposition of H. armigera decreased on high NaCl-stressed nontransgenic cotton, while the oviposition on Bt cotton tended to first increase but then decrease under low, moderate and high NaCl stress treatments.ConclusionsUnder certain content ranges of NaCl stress treatments, larval of H. armigera growth and development, and adult oviposition were no significant difference in the change for a certain period. However, under high NaCl stress, larval growth, development and adult oviposition were affected, which may provide insights for the prevention and control of H. armigera for Bt cotton in saline-alkali soils.

ECe prediction from EC1:5 in inland salt-affected soils collected from Khorat and Sakhon Nakhon basins, Thailand

ABSTRACTWe estimate the electrical conductivity of saturated soil paste extract (ECe) from electrical conductivity of a 1:5 soil-water dilution ratio (EC1:5) in Northeastern Thailand. Soil samples of various textures and salinity collected from Sakhon Nakhon basin were used to develop multiple regression models, from which the linear model was chosen and was validated on soil samples from the Khorat basin. Comparison with previous models indicated that most linear models gave a good fit, but the non-linear models either over or underestimated the measured values. The models performed very well for low values of ECe (<5 dS m−1), while the prediction errors increased significantly for ECe levels >35 dS m−1. The present model performed well at various ECe levels and can be used to predict salinity levels for soils weathered from salt deposits in sedimentary rocks with similar rock formation in countries like Malaysia, Vietnam, Cambodia, and Laos.

Variable decomposition of two plant litters and their effects on the carbon sequestration ability of wetland soil in the Yangtze River estuary

Highly efficient sequestration of carbon into soil by plants is crucial to wetland ecosystems under rising atmospheric CO2. The carbon sequestration ability of wetland can be roughly evaluated from the amount of carbon fixed through plant's photosynthesis, but the decomposition properties of plant litter returning to soil are also essential to its evaluation. We examined litter decomposition of Phragmites australis (P. australis) and Spartina alterniflora (S. alterniflora), two dominant plants from Jiuduansha wetland in the Yangtze River estuary, returned to soil in-situ and ex-situ, to clarify their effect on soil respiration and carbon sequestration efficiency. Both mass and carbon content of S. alterniflora were lost faster than P. australis when their plant litters were returned to soil. Soil type exerted a significant effect on litter decomposition but not on plant ranking for decomposition rate (k). High moisture and low nitrogen content in the wetland soils resulted in the lower decomposition rates of litter, compared with inland soils. Litter properties were determining factors in ranking of decomposition rate, in which the k was negatively correlated with the lignin/N and C/N ratios, and positively correlated with the initial nitrogen content. P. australis had low nitrogen content, high lignin/N and C/N ratios, so it had the lower decomposition rate and soil respiration. Combine the plant biomass, litter decomposition and soil respiration, P. australis wetland possesses the higher carbon sequestration ability in the Yangtze River estuary than S. alterniflora wetland.

Soil carbon storage, respiration potential, and organic matter quality across an age and climate gradient in southwestern Greenland

Geological factors influence biological cycling of organic carbon in soils but are not well represented in our understanding of Arctic carbon dynamics. Landscape age, for instance, directly affects quantity and quality of soil carbon, which are two strong controls of the temperature sensitivity of soil organic matter. We investigated soil carbon storage, respiration potential, and organic matter quality for microbial decomposition across a climate and landscape age gradient in southwest Greenland that deglaciated during the Holocene. We measured soil respiration during a 370-day laboratory incubations of active layer soils collected from four study areas across this gradient (ages 1.8 × 102, 6.8 × 103, and 1.0 × 104, coinciding with a climate gradient from drier inland to wetter coastal terrain) and used a soil respiration model comparison approach to assess the substrate quality of stored organic matter for microbial decomposers. Soils store more than three times greater organic carbon at the 10,000-year-old, maritime climate study areas than the 180-year-old, continental climate study areas. Respiration rates were highest in the surface soils of the coastal areas. Model comparisons reveal important heterogeneity in the quality of organic matter for microbial decomposition between areas: coastal soils were best modeled by both one- and two-pooled models, and inland soils were best represented by one-pooled respiration models. Together, the measures of carbon quality (C:N, CO2 production, and model parameters estimating initial CO2 production rates from different organic matter pools) show that shallow soils at the southern coastal area, Kobbefjord, had the highest respiration rates from the recalcitrant carbon pool. This study reveals differences in carbon storage and turnover associated with landscape age and climate factors in western Greenland. When applied to thermodynamic theory, which predicts that temperature sensitivity increases with carbon recalcitrance, our findings suggest that carbon stored in coastal soils may be more sensitive to climate warming than inland soils.

Analysis of Catena on Representative Soils derived from Granite and Granite Gneiss

Soil catena can be characterized by some properties, such as drainage levels and soil textures. Characteristics of soil catena are different drainage levels from a summit to the direction of gravity and similar soil textures. Therefore this study was performed GIS (Geographic information system) and statistical analyses using perimeters from soil series in order to characterize quantitatively and objectively soil distributional properties in Korea. The total of 16 soil series from representative granite and granite gneiss originated soils were selected among inland soils from detailed soil maps (1:25,000 scale) in Rural Development Administration (RDA) and analyzed. After the detailed soil maps were merged by soil series unit, perimeters were measured from one soil series to neighboring soil series using functions of table join, merge, dissolve, buffer, and clip in ArcGIS (10.1). The covering ratio of each soil series unit was calculated from neighboring perimeters by soil series and applied to clustering analysis. Soils that were analyzed were the total of 16 soil series; 7 of sandy loam and 9 of clay loam. As a result, analyzed soil series adjoined complicatedly such as Hyocheon series adjoined 26 series and Jisan did 276 series. The results of the clustering analysis showed that soils were clustered by soil textures except a few soil series. This study applied only one property that was a length of neighboring soil series to GIS and statistical analyses. These results were compared to existing soil groups that were classified by new-soil taxonomy, texture, soil type and drainage level. It showed that these analyses can provide soil characteristics by soil texture. Based on this study, there is a need to investigate further objectively and quantitatively in statistical analyses of soil series.

Characteristics of residual organochlorine pesticides in soils under different land-use types on a coastal plain of the Yellow River Delta.

The residual levels of organochlorine pesticides (OCPs) were examined in soils covering five types of land use along a salinity gradient on the Yellow River Delta. The most prominent OCPs were dichlorodiphenyltrichloroethane (∑DDT, arithmetic mean=5.11μgkg(-1)), hexachlorocyclohexane (∑HCH, 1.69μgkg(-1)) and ∑endosulfan (10.4μgkg(-1)). The spatial variability of OCPs composition shifted from γ-HCH and o,p'-DDT dominated pesticides in coastal soils to p,p'-DDE dominated pesticides in inland soils. In different land-use types, the percentages of β-HCH and p,p'-DDE are characterized by more recalcitrant components in decreasing order of vegetable fields, cereal fields, cotton fields, wetlands and tidal flats with increasing soil salinity. However, the less recalcitrant components, γ-HCH and o,p'-DDT, showed an opposite trend. Endosulfan sulfate predominated in all land-use types. Residual levels of β-HCH were affected by soil organic matter. The correlations between γ-HCH and clay content and between p,p'-DDE, o,p'-DDT and salinity might associate with the influence of sediment cotransport by the Yellow River and the density of anthropogenic activities in coastal region. Depth distribution of the OCPs in typical soil profiles also implied that local historical usage and sediment transport by the Yellow River both affected the OCPs residual in this region.

Genetic Variation and Heritability Estimates for Bunch Yield, Bunch Components and Vegetative Traits in Oil Palm Interspecific Hybrids

Progeny testing of oil palm interspecific hybrids was conducted in four trials in Kluang, Ulu Paka, Teluk Intan and Carey Island, Malaysia. The interspecific hybrids (O  P) were created according to the North Carolina Model I (NCM I) mating design, using Elaeis oleifera (O) and Elaeis guineensis var. pisifera (P) as the maternal and paternal parents, respectively. Differences among O, P and O-within-P were determined by the performance (bunch yield, components and vegetative traits) of the progenies. There were significant differences among P for fresh fruit bunch (FFB) yield, bunch number (BN) and average bunch weight (ABW) in Kluang, Ulu Paka and Teluk Intan, but not in Carey Island. FFB yield was generally higher on coastal soils (Teluk Intan and Carey Island) than inland soils (Kluang and Ulu Paka). Heritability was calculated based on the intraclass correlation. Heritability estimates for these three yield components were variable, depending on the breeding material and environment in which the materials were tested. Fruit to bunch (F/B) and oil to bunch (O/B) of parthenocarpic fruits were important in determining the overall O/B of the interspecific hybrids. The O  P hybrids in Kluang showed the lowest height increment with only a mean of 14.0 cm/year, whereas in Ulu Paka and Teluk Intan, the values were higher at 24.0 cm/year and 25.0 cm/year, respectively. The study showed that the FFB yields of oil palm interspecific hybrids performed better in coastal soils than inland soils.

Salinity Is an Agent of Divergent Selection Driving Local Adaptation of Arabidopsis to Coastal Habitats.

Understanding the molecular mechanism of adaptive evolution in plants provides insights into the selective forces driving adaptation and the genetic basis of adaptive traits with agricultural value. The genomic resources available for Arabidopsis (Arabidopsis thaliana) make it well suited to the rapid molecular dissection of adaptive processes. Although numerous potentially adaptive loci have been identified in Arabidopsis, the consequences of divergent selection and migration (both important aspects of the process of local adaptation) for Arabidopsis are not well understood. Here, we use a multiyear field-based reciprocal transplant experiment to detect local populations of Arabidopsis composed of multiple small stands of plants (demes) that are locally adapted to the coast and adjacent inland habitats in northeastern Spain. We identify fitness tradeoffs between plants from these different habitats when grown together in inland and coastal common gardens and also, under controlled conditions in soil excavated from coastal and inland sites. Plants from the coastal habitat also outperform those from inland when grown under high salinity, indicating local adaptation to soil salinity. Sodium can be toxic to plants, and we find its concentration to be elevated in soil and plants sampled at the coast. We conclude that the local adaptation that we observe between adjacent coastal and inland populations is caused by ongoing divergent selection driven by the differential salinity between coastal and inland soils.

Composition of bacterial communities in sand dunes of subtropical coastal forests

Coastal sand dunes are a hostile environment for forests. Little is known about the composition and diversity of the bacterial community in forest soils established on sand dunes. This study examines the soil bacterial community in the upland and lowland Casuarina and lowland Hibiscus successional forests in a coastal sand dune ecosystem. The 16S rRNA gene clone libraries were constructed to analyze the structure and diversity of communities. The Acidobacteria and Proteobacteria predominated in the sand dune forest communities, but the proportions of some phylogenetic groups differed among three communities. Some Actinobacteria- and Bradyrhizobium-related clones were only present or abundant in Casuarina forest soils. Because Casuarina could support a symbiotic, N2-fixing soil bacterial community, the composition of the microbial community may reflect its potential roles in the nitrogen budget and the effects of vegetation. Based on the diversity indices, the lowland Casuarina soils had the least diverse community, and the upland Casuarina community was the most diverse. Compared to an inland natural forest community, the dune communities were more diverse and had different proportions of abundant bacterial groups from those in the inland soils. The distribution of the abundant operational taxonomic units also differed among coastal and inland forests. The topography and vegetation type could affect the soil bacterial community composition in sand dune forests. The high diversity of soil bacterial community may be a result of the succession phase of the sand dune ecosystem.

Germination Responses of the Invasive Triadica sebifera and Two Co-occurring Native Woody Species to Elevated Salinity Across a Gulf Coast Transition Ecosystem

With sea level rise, coastal ecosystems farther inland are expected to experience extended duration of inundation and elevated salinity. However, the effects of elevated salinity on initial recruitment of native and invasive woody species in coastal ecosystems are poorly understood. We assessed effects of elevated salinity across a range of soil types on germination of the invasive Triadica sebifera and two natives, Baccharis halimifolia and Morella cerifera, using growth chamber and greenhouse experiments. In both studies, germination was compared across four salinity levels (0, 10, 20, and 30 g/l). In the greenhouse, percent germination of these species was also compared across soils spanning the five dominant vegetation zones that define a typical coastal transition ecosystem in coastal Mississippi, USA. Final percent germination of all species decreased with increased salinities in both experiments. In the greenhouse, germination of all species was reduced in soils from the most seaward vegetation zones. Overall, there were species-specific germination responses to salinity treatments and soil types. Of the three species, B. halimifolia was least sensitive to increasing salinity. Germination of the invasive Triadica sebifera did not differ across salinity levels in inland soils, displaying plasticity of germination traits. This plasticity may increase the likelihood of successful germination under some degree of salinity stress, and thereby contribute to the inland spread of T. sebifera along coastal transition ecosystems.

In vitro growth of Ganoderma boninense isolates on novel palm extract medium and virulence on oil palm (Elaeis guineensis) seedlings

Aims: Basal stem rot (BSR) disease caused by Ganoderma pathogenic fungi, especially Ganoderma boninense is thriving rapidly in both areas with coastal and inland soils. The objectives of this study were to isolate and characterize Ganoderma isolates collected from various locations in Peninsular Malaysia through the comparison of their growth rate in vitroly on conventional and novel palm extract media, and to determine the degree of virulence caused by the isolates in oil palm seedlings. Methodology and results: In this study, 12 Ganoderma isolates were collected from infected oil palm trees, from various locations – Johor, Negeri Sembilan, Kedah, Perak, Pahang, and Kelantan, in Malaysia in year 2011. Twelve Ganoderma isolates were identified using molecular method with primer set that targeted at small-subunit 18S rDNA fragment, and characterized by determining the in vitro growth rate, and degree of virulence in 2-month-old oil palm seedlings in the nursery using both disease incidence (DI) and disease severity index (DSI) as the measurements to quantify the infection. All the Ganoderma isolates were identified as G. boninense and sequences of the respective isolates were deposited in GenBank. In general, all the isolates proliferated faster on oil palm extract medium (OPEM) compared to malt extract agar (MEA). Twelve G. boninense isolates were observed to illustrate different degree of virulence ranging from highly pathogenic to least pathogenic. Conclusion, significance and impact of study: Cultures of 12 G. boninense isolates were observed to show faster growth rate (P < 0.014) on OPEM under in vitro conditions compared to conventional MEA medium, except Bt Lintang G10 and GBA G12 isolates. OPEM medium could provide a better alternative for maintaining and culturing Ganoderma strains. In the current study, both DI and DSI were highly correlated. However, there were low linear relationships (R 2 < 0.423) between mycelia growth rate (on MEA and OPEM) and degree of virulence (DI and DSI) at 12-, 14- and 16weeks after treatments among the G. boninense isolates tested. Furthermore, different degrees of virulence in twelve separate Ganoderma isolates were reported. Therefore, it is crucial to incorporate more than one isolate into any researches on screening for Ganoderma resistance or tolerance planting materials, searching for potential biological control agents, and studying bitrophic or tri-trophic interactions. In addition, this study was aimed to isolate G. boninense strains with various virulence levels for future studies.

원소분석기를 이용한 형도 퇴적물의 총탄소 및 총유기탄소 특성

해양 퇴적물내 함유된 총탄소(total carbon; TC), 총무기탄소(total inorganic carbon; TIC)와 총유기탄소(total organic carbon; TOC)의 정량적 이해는 해양 저서 퇴적 환경 해석을 위한 기본 자료이다. 원소분석기(elemental analyzer; EA)는 내륙 토양 및 해양 퇴적물의 탄소성분 분석에 많이 이용되고 있다. 원소분석기로 분석한 표준시료샘플(soil reference material; SRM)의 탄소 및 질소함량은 평균 2.30%와 0.21%이었으며, 표준편차(standard deviation)는 각각 0.02, 0.01이었다, 상대표준편차(relative standard deviation; RSD)는 각각 0.01, 0.06으로 높은 정밀도를 나타내었다. 형도 부지의 총유기탄소(TOC) 2.0% 이하 샘플에 대해 총유기탄소(TOC)와 총탄소(TC) 분석치의 회귀분석은 기울기가 0.9743인 직선형 관계(<TEX>$R^2$</TEX>=0.9989, n=38)를 보였으며, 2개 샘플을 제외한 총유기탄소 0.5% 이하의 총유기탄소량 및 평균입도의 관계 회귀분석 결과는 기울기가 0.0444인 직선형 관계(<TEX>$R^2$</TEX>=0.6937 n=36)를 나타내었다. 형도 표층퇴적물의 총유기탄소(TOC) 함량은 0.10~1.67%(평균 <TEX>$0.26{\pm}0.37%$</TEX>) 범위로 S02 정점에서 1.67%, S07 정점에서 1.31%이고 나머지 점점은 1.00% 이하의 총유기탄소(TOC) 함량을 나타냈다. 주상퇴적물 PC 01 정점의 경우 70 cm 부근에서 총유기탄소(TOC)가 가장 높은 0.20%을 보였고, 주상퇴적물 PC 02 정점의 경우 60 cm 부근에서 가장 높은 0.24%를 나타내었다. 따라서 형도 샘플의 총유기탄소(TOC) 0.5% 이상 함유 샘플에 대해서는 탄산염 같은 무기탄소량이 높은 퇴적물 분석시 오차가 발생할수 있지만, 이와 같은 결과로부터 얻어진 유기탄소분석 방법은 해양 퇴적물의 유기탄소분석에 적용 될 수 있다. 그리고 원소분석기(EA) 정밀도 및 정확도로 해양 퇴적물 표층 및 주상 퇴적물 유기탄소분석 분석 실험에 유용 할 것으로 사료된다. Quantitative understanding of total carbon, total inorganic carbon and total organic carbon contained in ocean sediments is a basic data for interpretation of oceanic sediment environments. Elemental analyzer(EA) is frequently used for the analysis of carbon contents in inland soils and ocean sediments. Carbon and nitrogen contents of the soil reference material analyzed by an EA were 2.30% and 0.21% with standard deviations of 0.02 and 0.01, respectively. Relative standard deviations were 0.01 and 0.06, respectively, representing a high precision. Regression analysis of TOC and TC analysis results for the samples with TOC of less than 2.0% for the site in Hyung-Do showed a linear relationship with a slope of 0.9743(<TEX>$R^2$</TEX>=0.9989, n=38), and the results of a relationship regression analysis between total organic carbon contents less than 0.5% and average grain size except for two samples showed a linear relationship with a slope of 0.0444(<TEX>$R^2$</TEX>=0.6937 n=36). TOC contents of surface sediments were in the ranges of 0.10~1.67%(Average <TEX>$0.26{\pm}0.37%$</TEX>) with TOC values of 1.67% at S02 sampling site, 1.13% at S07 sampling site, and less than 1.00% at remaining sites. In the case of PC 01 core sediments, TOC showed the highest value of 0.20% near 70 cm. In the case of PC 02 core sediments, the highest value of 0.24% was indicated near 60 cm. The analysis method of organic carbon obtained from Hyung-Do Intertidal zone sediment sample results may be considered applicable to an organic carbon analysis for ocean sediments and useful for organic carbon analysis experiments of ocean sediments with a reduction in time required for the analysis and a high precision coupled with a high accuracy.