Sand Dune Soil Research Articles

Limited effects of simulated acidic deposition on seedling survivorship and root morphology of endemic plant taxa of the Athabasca Sand Dunes in well-watered greenhouse trials

The Athabasca Sand Dunes of northern Saskatchewan support 10 endemic vascular plant taxa listed under the Species at Risk Act (SARA). The Athabasca Sand Dunes are subject to acidic deposition; the potential impacts of which are a significant knowledge gap to a comprehensive reassessment of the conservation status of these taxa. We used a greenhouse experiment to assess the potential effects of acidic deposition on the root system morphology of the following three endemic species: Armeria maritima (P. Mill) Willd. ssp. interior (Raup) Porsild, Deschampsia mackenzieana Raup, and Stellaria arenicola Raup. We found limited effects of three pH treatments on root diameter, root length, surface area, and branching. Although acidic deposition is likely not a short-term threat, current and future deposition still may be a significant long-term threat. The Athabasca Sand Dune soils are considered highly sensitive, and acidification and nutrient leaching can take several decades to manifest. This should be considered when assessing the conservation status of these endemic taxa, particularly A. maritima, as this species may be more sensitive than the other species to acidic deposition owing to a small population size and limited habitat breadth.

生物土壤结皮对荒漠土壤线虫群落的影响

Biological soil crusts(BSCs) play an important role in dune fixation and maintaining soil biota in arid desert ecosystems.Soil nematodes can be used as significant bio-indicators to reflect soil recovery regimes and important biological properties in studies of the restoration and health of sandy ecological areas.However,the relationship between BSCs and nematodes is currently poorly understood.To understand how BSCs affect soil nematodes,sand dune soils under algal and moss crusts were investigated in an artificially revegetated desert area at the southeastern edge of the Tengger Desert,China.Sample plots were selected in four areas that had undergone different periods of sand-fixing(the sand dunes were stabilized in 1956,1964,1981 and 1991,respectively).Mobile sand dunes were used as the control.Soil samples from different soil layers(0—10,10—20 and 20—30 cm,respectively) under algal and moss crusts were collected in different months(4,7,9 and 12,respectively) to analyze the temporal and spatial variation of soil nematodes in the artificially revegetated desert areas at the southeastern edge of the Tengger Desert.Natural vegetation areas at Hongwei in the Shapotou area were used as the control.Soil nematodes were separated using the improved Baermann funnel method and were identified and counted by an optical microscope.Our results showed that algal and moss crusts could significantly enhance nematode abundances,generic richness,Shannon-Weaver index,enrichment index and structure index in the sand dunes,artificially stabilized in 1956,1964,1981 and 1991,respectively(P0.05).This can be attributed to the presence of BSCs providing an essential food source and the creation of suitable habitats for soil nematodes.The time of sand dune fixation was positively correlated with soil nematode abundances,generic richness,Shannon-Weaver index,enrichment index and structure index under crusts(P0.05).This result suggested that long periods of sand dune fixation were more beneficial to the survival and reproduction of soil nematodes than short periods of sand dune fixation.Crust type significantly affected soil nematode communities,with moss crusts having higher nematode abundances and generic richness than those of algal crusts.This result suggested that the late-successional moss crusts were more beneficial to the survival and reproduction of soil nematodes than the early-successional algal crusts.In addition,algal and moss crusts significantly increased soil nematode abundances and generic richness in the 0—10,10—20 and 20—30 cm soil layers.However,the effect gradually decreased with increasing soil depth,which demonstrated that BSCs were more beneficial to the survival of soil nematodes in topsoil than in subsoil.There were also seasonal changes of nematode abundances under algal and moss crusts,in the following order: autumn summer spring winter.Seasonal changes could reflect changes in the biomass,cover and species composition of BSCs with season changes.Therefore,the presence and succession of BSCs were beneficial to the survival and reproduction of soil nematodes,which increased their amount,species and diversity.The results indicate that BSCs could improve the recovery of soil and corresponding ecological systems in the artificially revegetated desert areas at the southeastern edge of the Tengger Desert.

Bacterial communities in soil mimic patterns of vegetative succession and ecosystem climax but are resilient to change between seasons

Organism succession during ecosystem development has been researched for aboveground plant communities, however, the associated patterns of change in below-ground microbial communities are less described. In 2008, a study was initiated along a developmental sand-dune soil chronosequence bordering northern Lake Michigan near Wilderness Park (WP). It was hypothesized that soil bacterial communities would follow a pattern of change that is associated with soil, plant, and ecosystem development. This study included 5 replicate sites along 9 soils (n = 45) ranging in age from ∼105 to 4010 years since deposition. Soil bacterial community composition and diversity were studied using bacterial tag-encoded FLX amplicon pyrosequencing of the 16S rRNA gene. Bray–Curtis ordination indicated that bacterial community assembly changed along the developmental soil and plant gradient. The changes were not affected by seasonal differences, despite likely differences in plant root C (e.g. exudates), temperature, and water availability in soil. Soil base cations (Ca, Mg) and pH declined, showing log-linear correlations with soil age (r ∼ 0.83, 0.84 and 0.81; P < 0.01). Bacterial diversity (Simpson's 1/D) declined rapidly during the initial stages of soil development (∼105–450 y) and thereafter (>450 y) did not change. Turnover of plant taxa was also more rapid early during ecosystem development and correlated with bacterial community structural change (P < 0.000001; r = 0.56). It is hypothesized that plants help to drive pedogenic change during early (<450 y) soil development (e.g. pH decline, cation leaching) which drive selection of soil bacterial communities. In mature soils (∼450–4000 y), resilient and stable soil bacterial community structures developed, mimicking steady-state climax communities that were observed during latter stages of primary plant succession. These relationships point to possible feedbacks between plant and bacterial communities during ecosystem development.

The impact of heat and water stress conditions on the growth of the biofuel plant Jatropha curcas

Pot experiments were carried out to evaluate the effects of drought and salinity stresses and mulch amendment on Jatropha in sand dune soil under three conditions: glasshouse, shade house and open area. Plants were irrigated with freshwater and diluted seawater adjusted to two levels of electrical conductivity- 3 and 6 dS m-1. The results showed that experimental conditions remarkably affected the evapo-transpiration rate, soil moisture, salts accumulation and plant biomass production. Low temperature (23°C) conditions exhibited highest plant growth and soil moisture and lowest salts deposition. Plants showed no symptoms of heat stress in the glasshouse. The shade house and the open area profoundly reduced plant biomass and water content in the soil. Compared to the control, the mulch amended treatments had sufficient water for plant growth even in the high temperature of the open area. High salt content was found in salinity treated pots but the salinity level did not reduce Jatropha growth. Salt accumulated in the salinity treated pots helped retain more water, reduced the temperature and provided nutrients to the plants, with results which were almost similar to those from the mulch effect. The temperature conditions of the shade house and the open area (max>40°C) caused substantial water loss and induced death of plants. Jatropha is a succulent and drought tolerant plant and a close irrigation interval is not the best option for Jatropha growth. But, organic amendment is needed when there is a big loss of soil water due to heat stress condition.

Leachability of phosphorus in soils after application of burned and unburned poultry litter

Release of phosphorus (P) from terrestrial environments undermines water quality by contributing to eutrophication in lakes and rivers. Soil amendment is considered one of the best management practices to reduce P loss from sandy soils. Laboratory leaching experiments were conducted to evaluate the effectiveness of different soil amendments in reducing P leaching from a typical sandy masa soil in Japan. Burned and unburned poultry litters (PL) are commonly used as a fertilizer and amendment to improve soil productivity. Application of biosolids to meet the nitrogen requirements of crops can lead to accumulation of P in soils, which may result in P loss to water bodies. Long-term application of P with animal manure in amounts exceeding removal with crops leads to buildup of P in soil and to increasing risk of P loss to surface water and eutrophication. We investigated the mobility of P in burned and unburned PL samples from a sand dune Regosol and Masa Terrestrial Regosol (Japanese soils). Soils amended with either PL or poultry litter ash (PLA) differed greatly from those with no litter application. Poultry litter ash application to soils significantly increased the total P as compared to the soils amended with PL. Masa soil contained higher extractable P than sand dune soil. Manure amended soils differed for P release in the order of PLA masa > PLA sand > PL masa > PL sand > control. The higher P concentration in the ash resulted from elimination of the carbon during burning of the litter. The concentrations of K, Ca and Mg in leachate varied irrespective of the total amount applied with PL. Key words: Phosphorus movement, poultry litter ash, soil fertility, metal ions leaching.

Use of zeolite to alleviate water stress on subsurface drip irrigated barley under hot environments

AbstractWater stress is the primary environmental factor that limits cereal production in Mediterranean environments, where barley (Hordeum vulgare L.) is one of the main crops. This investigation aimed at evaluating the effects of zeolite on barley growth under subsurface drip irrigation, subjected to water and heat stress. A sand dune soil was amended with Ca‐type zeolite and irrigated every 2nd, 3rd, 4th and 5th day. The results showed that zeolite application significantly increased water‐holding capacity of the soil and improved plant growth. Using subsurface irrigation with zeolite amendment helped to reduce water evaporation, kept more water in lower horizons, encouraged salt leaching, and the plants used water more efficiently. Plant growth parameters showed significant differences among treatments and were negatively affected by heat and water stress conditions. High temperatures caused accelerated evapotranspiration, water stress in plants and faster depletion of water from the root zone, causing substantial water loss and inducing water deficit conditions in plants. Using subsurface irrigation poses a better option for the reduction of evaporation and achieving higher water use efficiency. Application of zeolite together with subsurface irrigation may provide favorable conditions for crop production in water‐scarce areas under warm environments. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Contrasting drought tolerance strategies in two desert annuals of hybrid origin.

Woody plants native to mesic habitats tend to be more vulnerable to drought-induced cavitation than those in xeric habitats. Cavitation resistance in herbaceous plants, however, is rarely studied and whether or not annual plants in arid habitats conform to the trends observed in woody plants is unknown. This question is addressed by comparing the hydraulic properties of annual plants endemic to relatively mesic and seasonally xeric habitats in the Great Basin Desert, in both native and experimental settings. Vulnerability to cavitation between species differed as predicted when vulnerability curves of similar-sized native individuals were compared. Contrary to expectations, Helianthus anomalus from the relatively mesic dune sites, on average, exhibited higher native embolism, lower soil-to-leaf hydraulic conductance (kL) and lower transpiration rates, than its xeric analogue, H. deserticola. In transplant gardens, H. anomalus’ vulnerability to cavitation was unaffected by transplant location or watering treatment. In H. deserticola, however, vulnerability to cavitation varied significantly in response to watering in transplant gardens and varied as a function of stem water potential (Ψstem). H. deserticola largely avoided cavitation through its higher water status and generally more resistant xylem, traits consistent with a short life cycle and typical drought-escape strategy. By contrast, H. anomalus’ higher native embolism is likely to be adaptive by lowering plant conductance and transpiration rate, thus preventing the loss of root-to-soil hydraulic contact in the coarse sand dune soils. For H. anomalus this dehydration avoidance strategy is consistent with its relatively long 3–4 month life cycle and low-competition habitat. We conclude that variance of hydraulic parameters in herbaceous plants is a function of soil moisture heterogeneity and is consistent with the notion that trait plasticity to fine-grained environmental variation can be adaptive.

Profile distribution of total and available Sulphur and boron in sandy soils of Nigerian semi-arid savanna .

The total and available sulphur and boron forms were determined in sandy soils formed from sand dunes, sandy alluvial terrace and sandstone formation in northwestern Nigeria. Hot water and Morgan’s solution (sodium acetate/acetic acid solution buffered at pH 4.8) were used as extractants for available boron while calcium phosphate solution was the extractant for available sulphur. In the surface horizons, in all the sandy soils, total boron ranged from 2.03 to 170.85 mg kg-1 soil, while subsoil values varied from 0.59 to 135 mg kg-1 soil. The means of the total boron are highly significantly (p=0.001) different among the sandy soils. The means of hot water extractable boron (Bhw) are also significantly (p=0.05) different for the sandy soils. Generally boron values are significantly higher in the surface horizons than in the sub-surface horizons. In terms of magnitude, the sandy soils may be arranged as follows: Rabah terrace > Wurno sandstone > Sangiwa dunes > Illela dunes > Sokoto dunes. The mean values of calcium phosphate extractable sulphur are significantly (p=0.05) different among the sandy soils. Values in the surface horizons are also generally higher than the sub-surface horizons. The values of Sc are higher in the sand dune soils than the sandstone and terrace soils within the study area. By the critical limits of 0.1 to 0.2 mg kg-1 given in the literature for Nigerian savanna soils, the sandy soils understudied appear to be slightly above this limit especially for the terrace and sandstone soils. For the sand dune soils the surface horizons are marginally adequate but the subsoils are below the critical limit. If thecritical limit of 4 mg kg-1 quoted in the literature is considered, all the sandy soils understudied are deficient in available sulphur except for soils derived from Illela sand dune, which are only marginally sufficient. For optimum crop production on sandy soils within the study area, sulphur and boron addition through the use of boronated single supper phosphate and other sulphur-based fertilizers should therefore, be encouraged.

Effect of saline water irrigation and manure application on the available water content, soil salinity, and growth of wheat

Abstract Good water management combined with appropriate soil management is necessary for sustainable crop production in drylands. A pot culture experiment was conducted using sand dune soil under greenhouse conditions to evaluate the response of wheat (Triticum aestivum L.) to the application of farmyard manure (FYM) or poultry manure (PM), and irrigation with water at two salinity levels (0.11 and 2.0 dS m−1) and two irrigation intervals (daily and every second day). The manure was applied at a rate of 20 Mg ha−1. The soil water content, measured 1 h before every irrigation, showed that soil treated with PM retained more water than that treated with FYM, while the control (no manure) contained the least water. FYM treatment resulted in 78 and 21% higher dry matter yield compared to the control and PM treatments, respectively, under daily irrigation using good-quality water. The increase was 29 and 55%, respectively, when saline water was used for daily irrigation. A similar trend was observed with the alternate day irrigation treatment; FYM gave the highest dry matter yield. The number of tillers and plant height showed that FYM was better than PM, which in turn was better than the control under irrigation with good-quality water regardless of the irrigation interval. When water of the highest salinity was used for irrigation, FYM was still always the best, but the control was now better than the PM treatment. The electrical conductivity of the soil measured at the end of the experiment was slightly higher with PM, as compared to the FYM and control treatments. A significant interaction between irrigation water quality and manure application was observed, affecting plant growth. PM aggravated the adverse affect of saline water on plant growth by increasing soil salinity.

Recycling of Chicken and Duck Litter Ash as a Nutrient Source for Japanese Mustard Spinach

ABSTRACT Recycling combusted poultry litter ash as a soil amendment would potentially ameliorate problems normally associated with poultry waste management. We evaluated the effect of chicken litter ash (CLA) and duck litter ash (DLA) as nutrient sources for Japanese mustard spinach (Brassica rapa L. var. perviridis) grown on a sand dune soil. Chicken and duck litter were ashed at five temperatures: 200, 400, 600, 800, and 900°C and the resulting ash samples were applied at the rate of 100 kg phosphorus (P) ha−1. Laboratory analysis showed the highest P extraction with citric acid from CLA and DLA obtained at 600°C. Chicken litter ash was richer in P and potassium (K) than DLA but the later contained more calcium (Ca) and magnesium (Mg). The amount of ammonium acetate soluble calcium (Ca), magnesium (Mg), and K recovered increased with increasing temperature except for Ca and Mg at the highest temperatures, 800 and 900°C. Plants grown in pots with the CLA and DLA obtained at 400°C had the highest P concentration, yielding significantly more biomass with dense green leaf color but on average, the DLA amended soil had greater biomass. However, the P level was higher in CLA treated plants than DLA due to the higher available P level (citric acid soluble). Increases in electrical conductivity and pH of the soil were noted after harvest due to litter ash application. Our experiment demonstrated that poultry litter is potential source of P and other nutrients for horticutural crops.

Assessing radiation impact at a protected coastal sand dune site: an intercomparison of models for estimating the radiological exposure of non-human biota

This paper presents the application of three publicly available biota dose assessment models (the ERICA Tool, R&D128/SP1a and RESRAD-BIOTA) to an assessment of the Drigg coastal sand dunes. Using measured 90Sr, 99Tc, 137Cs, 238Pu, 239+240Pu and 241Am activity concentrations in sand dune soil, activity concentration and dose rate predictions are made for a range of organisms including amphibians, birds, invertebrates, mammals, reptiles, plants and fungi. Predicted biota activity concentrations are compared to measured data where available. The main source of variability in the model predictions is the transfer parameters used and it is concluded that developing the available transfer databases should be a focus of future research effort. The value of taking an informed user approach to investigate the way in which models may be expected to be applied in practice is highlighted and a strategy for the future development of intercomparison exercises is presented.

Nocardiopsis arabia sp. nov., a halotolerant actinomycete isolated from a sand-dune soil

The taxonomic status of an unknown actinomycete isolated from a sand-dune soil was established using a polyphasic approach. Isolate S186(T) had chemotaxonomic and morphological properties consistent with its classification in the genus Nocardiopsis, grew on agar plates at NaCl concentrations of up to 15 % (w/v) and formed a distinct phyletic line in the Nocardiopsis 16S rRNA gene sequence tree. Its closest phylogenetic neighbours were Nocardiopsis chromatogenes, Nocardiopsis composta, Nocardiopsis gilva and Nocardiopsis trehalosi, with sequence similarity to the various type strains of 96.9 %, but it was readily distinguished from the type strains of these and related species using a range of phenotypic properties. It is apparent from the genotypic and phenotypic data that strain S186(T) belongs to a novel species of the genus Nocardiopsis, for which the name Nocardiopsis arabia sp. nov. is proposed. The type strain is S186(T) (=CGMCC 4.2057(T) =DSM 45083(T)).

Effects of Zeolite on Soil Nutrients and Growth of Barley Following Irrigation with Saline Water

ABSTRACT Soil salinity is a major abiotic factor limiting crop production but an amendment with synthetic zeolite may mitigate effects of salinity stress on plants. The objective of the study was to determine the effects of zeolite on soil properties and growth of barley irrigated with diluted seawater. Barley was raised on a sand dune soil treated with calcium type zeolite at the rate of 1 and 5% and irrigated every alternate day with seawater diluted to electrical conductivity (EC) levels of 3 and 16 dS m−1. Irrigation with 16 dS m−1 saline water significantly suppressed plant height by 25%, leaf area by 44% and dry weight by 60%. However, a substantial increase in plant biomass of salt stressed barley was observed in zeolite-amended treatments. The application of zeolite also enhanced water and salt holding capacity of soil. Post-harvest soil analysis showed high concentrations of calcium (Ca2 +), magnesium (Mg2 +), sodium (Na+), and potassium (K+) due to saline water especially in the upper soil layer but concentrations were lower in soils treated with zeolite. Zeolite application at 5% increased Ca2 + concentration in salt stressed plants; concentrations of trace elements were also increased by 19% for iron (Fe2 +) and 10% for manganese (Mn2 +). The overall results indicated that soil amendment with zeolite could effectively ameliorate salinity stress and improve nutrient balance in a sandy soil.

Comparison of Twelve Dielectric Moisture Probes for Soil Water Measurement under Saline Conditions

Recently the research on the determination of soil water content and electrical conductivity using automated technique has received tremendous attention. Selecting the type of system that should be used for soil water measurement under saline conditions depends on its precision. A laboratory study was carried out to measure the soil water content (θ) and soil solution electrical conductivity (ECw) using eight portable dielectric moisture probes namely ML1, ML2, MP4, WET, SK8, MIN, EC2 and SM2 and four profile probes namely ES, AG, P1 and P2. Air-dried Tottori sand dune soil was converted into saline by NaCl solutions of various concentrations. The out-put results of moisture probes showed that measurement accuracy was strongly dependent on the concentration of salt in the soil. Among the sensors WET, EC2 and ES exhibited higher sensitivity to the salts and over estimated water content by 0.04-0.08 cm 3 cm -3 whereas MP4, WET, SM2, ES, AG and P1 sensors also over estimated the volumetric water content by 0.02-0.03 cm 3 cm -3 at 3.83 dS m -1 soil salinity as compared to normal soil. Higher ECw increased the relative error of soil water measurement across the sensors. Among the moisture meters, commercially available ML1, ML2, SK8 and P2 gave sufficient accuracy in the presence of salts.

Streptomyces synnematoformans sp. nov., a novel actinomycete isolated from a sand dune soil in Egypt

A polyphasic taxonomic study was undertaken to establish the status of a novel actinomycete, strain S155(T), isolated from a sand dune soil in Egypt. The organism formed characteristic synnemata-like structures and exhibited chemical and morphological features consistent with its classification in the genus Streptomyces. An almost-complete 16S rRNA gene sequence of the isolate was compared with corresponding sequences of representative streptomycetes. The 16S rRNA gene sequence data supported the assignment of the strain to the genus Streptomyces and showed that it formed a distinct phyletic line; the organism was most similar to the type strains of Streptomyces ruber (97.0 %), Streptomyces rubiginosus (97.0 %), Streptomyces roseiscleroticus (96.9 %) and Streptomyces thermoalcalitolerans (97.1 %). It was readily distinguished from the type strains of these species using a combination of phenotypic properties. On the basis of these results, strain S155(T) (=CGMCC 4.2055(T) =DSM 41902(T)) is proposed as the type strain of the novel species Streptomyces synnematoformans sp. nov.

Effect of K-type and Ca-type artificial zeolites applied to high sodic soil on the growth of plants different in salt tolerance

The present study aimed to investigate the effects of K-type and Ca-type artificial zeolites on the growth and water and element absorptions of kidney bean (Phaseolus vulgaris L.), tomato (Lycopersicon esculentum Mill), maize (Zea mays L.) and beet (Beta vulgaris L.) in high sodic soil. Tottori sand dune soil, which was used as a control, was converted to high sodic soil mixed with salts. Each type of zeolite was mixed into the high sodic soil at rates of 0, 1, 2 and 5%. The results showed that kidney bean, tomato and maize died in high sodic soil 25–27 days after transplanting (DAT), whereas beet survived, although its growth was extremely suppressed at 26 DAT. The addition of Ca-type zeolite improved growth in all of the tested plants. Even 4 DAT the growth of beet was improved by recovery of water absorption, and growth of tomato was improved by recovery of Ca and K absorptions and cation balance, and restriction of Na absorption. Growth of kidney bean and maize improved at 11 or 13 DAT by recovery of water absorption and Ca and K absorptions. After 4 DAT, water absorption and P and K absorptions of beet were highly recovered compared with those of the other plants; beet growth improved to a large degree. The ameliorative effect of 5% Ca-type zeolite was lower than that of 2% in tomato, maize and beet because the excessive uptake of Ca restricted P transport from root to shoot, and high electrical conductivity of the soil solution restricted water uptake. Even 1% K-type zeolite addition suppressed growth of beet at 4 DAT, and the addition of 2% or 5% of K-type zeolite suppressed the growth of tomato and maize 11 or 13 DAT. Higher concentrations of HCO− 3 and CO2− 3, and pH of the soil solution of K-type zeolite treatments might inhibit water absorption by roots.

Nonomuraea aegyptia sp. nov., a novel actinomycete isolated from a sand dune

The taxonomic position of an unknown actinomycete isolated from a sand dune soil sample collected at Borg El-Arab in Egypt was established using a combination of genotypic and phenotypic data. Isolate S136(T) had chemotaxonomic and morphological properties consistent with its classification in the genus Nonomuraea and formed a distinct phyletic line in the Nonomuraea 16S rRNA gene tree. It was most closely related to the type strains of Nonomuraea helvata, Nonomuraea kuesteri and Nonomuraea turkmeniaca, sharing 16S rRNA gene similarities with these species of 97.1, 97.2 and 97.3%, respectively. The organism was distinguished from representatives of validly described Nonomuraea species using a range of phenotypic properties. It is apparent that the isolate belongs to a novel Nonomuraea species. The name proposed for this taxon is Nonomuraea aegyptia sp. nov., the type strain is S136(T) (=CGMCC 4.2054(T) = DSM 45082(T)).

The Effect of Biological Soil Crusts on Throughput of Rainwater and N into Lake Michigan Sand Dune Soils

Biological soil crusts composed of cyanobacteria, green algae, bryophytes, and lichens colonize soils in arid and semiarid ecosystems worldwide and are responsible for significant N input to the soils of these ecosystems. Soil crusts also colonize active sand dunes in more humid regions, but studies of structure and function of such sand dune crusts are lacking. We identified the cyanobacterial, algal, and bryophytic constituents and N production and leachates of biological soil crusts that colonize beach dunes at the Indiana Dunes National Lakeshore along southern Lake Michigan in Indiana, USA. To determine the role of these crusts in this system, we conducted a greenhouse experiment in which intact soil cores with biological crusts were subjected to artificial rainfall over a full growing season. The volume and N content of leachate from the cores were quantified in relation to degree of crust development, taxonomic composition, rainfall volume and intensity, light intensity, and the presence of plant litter. Net N throughput significantly exceeded N inputs to cores in rainwater. Net N outputs from crusts to subsurface soil ranged from 0. 01 to 0.19 g NH 4 + -N m−2 yr−1 and 0.01 to 0.61 g NO 3 – N m−2 yr−1. Thus, total inorganic N inputs associated with biological soil crusts ranged from 0.02 g N m−2 yr−1 to 0.8 g N m−2 yr−1. High volume (≥2 cm) rainfall resulted in more N leaching than low volume events, and plant litter added over the surface of crusted soil cores significantly increased the amount of N in leachate. Exploratory path analysis revealed direct and indirect linkages among environmental factors, crust development, and crust composition in regulating the throughput of H2O and N from these intact soil cores. Biological soil crusts at this site, combined with other properties of the soil surface, substantially increase N inputs to this water- and nutrient-limited sand dune ecosystem.

Symbiotic performance of fast-growing rhizobia isolated from the coastal sand dune legumes of west coast of India

The symbiotic efficiency of coastal sand dune rhizobial isolates on four cultivated legumes, cowpea (Vigna unguiculata), green gram (Vigna radiata), black gram (Vigna mungo) and horse gram (Macrotyloma uniflorum), was assessed. Among the isolates of Someshwara (S1–S5), inoculation of S5 resulted in the highest increase of shoot biomass in cowpea (control vs experimental, 1:6), while inoculation of P1 among the Padubidri isolates (P1–P5) induced the highest shoot biomass in cowpea (1:14.4). Inoculation of the isolate P2 induced higher shoot biomass against uninoculated controls of horse gram (12.6:1), green gram (11.2:1) and black gram (6.1:1). One-way ANOVA revealed significant difference in the shoot biomass between uninoculated and inoculated cowpea plants with ten rhizobial isolates (P <0.05). Cultivation of surface-sterilized green gram seeds on unsterilized dune sand resulted in profuse flowering as well as nodules within 6 weeks indicating possibilities for isolating efficient rhizobial strains through cultivating edible legumes on coastal sand dune soils.

Arum- and Paris-type arbuscular mycorrhizas in a mixed pine forest on sand dune soil in Niigata Prefecture, central Honshu, Japan.

Arbuscular mycorrhizas (AM) are the most widespread mycorrhiza in nature and form two morphologies, Arum- and Paris-type. The determining factors defining the two different morphologies are not well understood. In this study, the distribution of Arum- and Paris-type AM was determined in a mixed pine forest. A total of 35 plant species belonging to 20 families and 32 genera were identified and examined for AM colonization and morphological types. AM morphological types in 14 families were confirmed as follows: Arum-type in Rosaceae, Oleaceae, Lauraceae, Vitaceae and Compositae, Paris-type in Aquifoliaceae, Ulmaceae, Araliaceae, Theaceae, Magnoliaceae, Rubiaceae and Dioscoraceae, and both and/or intermediate types in Caprifoliaceae and Gramineae. Plant families whose AM morphological status was previously unknown were clarified as follows: Polygonaceae and Commelinaceae showed Arum-type morphology; Celastraceae, Menispermaceae and Elaeagnaceae had typical Paris-type morphology. The proportion of Arum-type to Paris-type species decreased in the following order: annuals > perennials > deciduous species > evergreen species, and pioneer group > early successional group > late successional group. Evergreen plants had a higher tendency to form Paris-type AM than annuals, perennials and deciduous plants. The results indicate that environmental changes, such as shade during plant succession, control the distribution of plant growth forms in mixed pine forest and may also play a part in the distribution of Arum- and Paris-type morphology. The identity of the plant seems to strongly influence AM morphology, though control by the fungal genome cannot be ruled out.