Arbuscular Mycorrhizae of Leymus arenarius on Coastal Sands and Reclamation Sites in Iceland and Response to Inoculation

The occurrence of arbuscular mycorrhizae fungi (AMF) was examined in natural and reclaimed sand dunes in Iceland. On the coastal sand‐plain of Myrdalssandur no spores of AMF were found on barren sand, and very few were found in 1‐ and 5‐year‐old reclamation sites of Leymus arenarius (lymegrass). A significantly higher number of AMF spores and root colonization were found in a 10‐year‐old reclamation site and in a natural old dune system of L. arenarius. AMF spores showed seasonal variation with higher occurrence in the fall than in the spring. On the volcanic island Surtsey, no AMF spores or root colonization were found on L. arenarius in 6‐ and 10‐year‐old dunes. However, AMF spores and root colonization were found in the 22‐year‐old Leymus dune. On Surtsey, a colonization pattern was found where AMF non‐dependent plants were the first colonizers followed by AMF facultative plants, then by AMF‐dependent plants. Today AMF facultative plants have the highest number of species but AMF non‐dependent plants have the largest population size. Three different AMF inocula were tested on L. arenarius; growth of seedlings was improved significantly by an indigenous AMF inoculum compared with commercial inocula. Inoculation of nursery grown seedlings of L. arenarius followed by transplantation into barren sand seeded with L. arenarius is recommended because this method will ensure establishment of the plant and enhance succession.     

Seasonality of mycorrhizae in coastal sand dunes of Baja California

 Populations of arbuscular mycorrhizal fungi were estimated from spores associated with seven plant species in coastal dunes at El Socorro, near Ensenada, Baja California, during six months in 1992. The seasonal patterns of percent root colonization were also described in the same species during the wet season (January–March) and the dry season (April–July). Comparisons were made between the pioneer species (Abronia maritima) in the mobile dunes and six species (Abronia umbellata, Atriplex julacea, Camissonia californica, Haplopappus venetus, Helianthus niveus and Lotus spp.) in the fixed dunes. Mycorrhizal colonization in Abronia maritima was slight (<1%) and we observed few spores (<1/g soil). All of the species in the fixed dune formed mycorrhizae with up to 80% colonization in early summer, and no more than 4 spores/g soil by late summer. The highest percentages of total colonization and abundance of spores did not coincide temporally for any of the seven species, but the percentages were higher in summer than in spring. Arbuscules were more abundant when the soil was moist, and vesicles more abundant when it was dry. Accepted: 16 August 1995     

Collembola as bioindicators of restoration in mined sand dunes of Northeastern Brazil

Opencast mining causes severe environmental impacts by removing the vegetation cover and depleting the fauna. Reforestation methods using native species and diverse pre- and post-disturbance approaches aim to recover the original richness and diversity of species found before the impact. Bioindicators are powerful tools to evaluate the restoration of the original environmental conditions in disturbed areas. We used species richness, endemism and diversity measurements of Collembola to compare successional stages in reforested sites of different ages compared with a control undisturbed area. Richness and abundance of Collembola were subjected to correlation analysis with age of plots and vegetational variables. Areas that were reforested for up to 16 years supported a much lower Collembola species richness than undisturbed areas. Both the age of reforestation plots and vegetation variables (number of trees, diameter of crowns, depth of leaf litter and tree species richness) were positively and significantly correlated to collembolan abundance and richness. The results showed that the diversity of the 16-year-old plot was significantly higher than that of younger areas, but significantly less diverse than that of the control area. Endemic species were more sensitive to disturbance than non-endemics. Thus, species richness and diversity of soil Collembola can be only partially restored with appropriate reforestation methods, and although it takes many years, to some extent even endemic species can be gradually restored. Nevertheless, the maintenance of undisturbed diversity reservoirs linked by ecological corridors to reforested plots is imperative, as only undisturbed areas can support most of the endemic species able to re-colonize reforested sites.     

Zonation of vegetation on lacustrine coastal dunes: effects of burial by sand

More than 50 years ago it was proposed that zonation of major plant species on coastal dunes was determined by salt spray. Here, we argue against this hypothesis because (i) salt concentrations rarely exceed toxic levels; (ii) high precipitation in temperate latitudes washes the salt off the plants; (iii) major salt spray events occur in late autumn and winter when plants are dormant; and (iv) zonation also occurs on lacustrine dunes. Instead, we show evidence that zonation may be caused by burial because plant distribution was correlated with sand deposition and species were eliminated when burial exceeded their limits of tolerance, thus creating zones of different plant species. We conclude that in temperate regions (i) burial by sand may be among the most important factors in zonation, while salt spray may play a secondary role; and (ii) single environmental factors cannot be the determinants of a phenomenon as complex as species zonation.     

Disturbance and Seasonal Dynamics of Mycorrhizae in a Tropical Deciduous Forest in Mexico1

Mycorrhizal fungi were sampled in a deciduous tropical forest on the Pacific coast of Mexico during different seasons and in natural treefall gaps and pastures. All 12 plant species sampled in the forest were arbuscular mycorrhizal. The percent root infection and spore production were closely related to the phenology of the plants. Most tree species and all herbaceous species had the highest infection in the summer rainy season, but two species, Opuntia excelsa and Jacquinia pungens, had highest infection in the dry season. Unusually high rainfall during the dry season was associated with increased infection but not increased spore production. Spore density was low for all species at all sample times, except at the beginning of the July 1993 rainy season in, when we observed up to 28 spores/g soil. The percent cover of shrubs or herbs did not increase in gaps after two years, and we observed no colonizing seedlings. No plant species with cover higher than 2.7 percent occurred exclusively in gaps or forest. The percent mycorrhizal infection did not differ significantly between gaps and forest. Spore counts were as high in the gaps as in the forest in two of the three gaps but lower in the third gap. The lack of significant response of plants in these gaps after two years differed from the rapid response in tropical rainforests. It is likely related to the small size of the gaps and to light infiltration to the forest floor. Pastures were dominated by two species of exotic grasses and one species of mycorrhizal fungus, whereas forests had 15 fungal species. The slow regrowth of vegetation in gaps was not limited by mycorrhizal fungi, since they were still abundant after the treefalls, but recovery in pastures could be affected by low fungal diversity and dominance of grasses.     

Arbuscular mycorrhizae in a tropical sand dune ecosystem on the Gulf of Mexico

 Root samples of 37 species distributed on the beach and along a successional gradient (from mobile to stabilized areas) in a tropical sand dune system on the Gulf of Mexico showed that 97% of the species were mycorrhizal. The mycorrhizal inoculum potential of the sand from several dune areas was compared using two different bioassays. Firstly, the field rate of colonization by arbuscular mycorrhizal fungi of Chamaecrista chamaecristoides seedlings transplanted to random plots in the foredunes and in the mobile area was measured. The seedlings were harvested at intervals during 3 weeks to record mycorrhizal structures. In the mobile area, no mycorrhizal colonization was observed during the experiment. In the foredunes, hyphae and external mycelium were present in 40% of the seedlings as early as 8 days after transplanting. After 15 days, arbuscules and vesicles were observed in 60 and 20% of the seedlings, respectively, and after 21 days, 100, 46 and 20% of the seedlings showed hyphae, arbuscules and vesicles, respectively. Secondly, maize seedlings were transplanted to pots previously filled with sand from the foredunes, mobile dunes, grassland and a Dyphisa robinoides shrub area. After 1 month, the lowest mycorrhizal inoculum potential was recorded for the mobile dunes and the highest for the shrub area. As expected, mycorrhizal inoculum potential increased with dune stabilization. Accepted: 17 July 1996     

以龟裂地植丛发生演替为例探讨植物对环境的反应与反馈效应

准葛尔盆地荒漠龟裂地植丛发生演替的研究结果表明：在荒漠龟裂地发生演替的初始阶段,环境因子对植物发生具有极大的限制作用。但是,一旦有先锋植物侵入,植物就会通过自身的生命活动不断改善其生存环境,为新植物的进入创造条件,新植物的定居又会反作用于环境,使其生存条件进一步改善,如此往复,推动整个微生态系统由简单至繁杂呈顺序性、方向性发展。生命的存在及其活动过程对环境的反应和对于环境的反馈作用,是导致生态系统顺向发展的根本动力。该研究将为如何改善生境质量提供理论基础,对植被恢复及受损生态系统的重建,特别是对加深全球变化环境下气候与植被关系的理解,提高预测陆地生态系统对全球变化反应的能力有重要的意义。     

Ectomycorrhizal ecology under primary succession on coastal sand dunes: interactions involving Pinus contorta, suilloid fungi and deer

Ectomycorrhizal fungi (EMF) are critical for pine establishment under primary succession. The species of EMF supporting primary successional pine seedlings on coastal sand dunes and mechanisms for their establishment were investigated. Fungi were identified from ectomycorrhizal roots using molecular techniques. Field seedlings were collected from forested and nonforested zones. Laboratory seedlings were grown in soils collected from the same zones, and in sterile soils inoculated with fresh and 1-yr-old dry deer fecal pellets. Suilloid fungi were frequently observed on all seedlings. A diverse group of fungi was available to seedlings in forested zones. A less diverse group of fungi was available to field seedlings in nonforested zones and all laboratory bioassay seedlings. Deer fecal inoculant yielded an average of two EMF per seedling. Both Suillus and Rhizopogon species dominated seedlings inoculated with fresh deer feces, but only Rhizopogon species dominated seedlings inoculated with 1-yr-old feces. Suilloid fungi are dispersed by deer, produce resistant spore banks and are the principle fungi supporting seedlings on the sand dunes.     

Mycorrhizae, crop growth, and crop phosphorus nutrition in maize-soybean rotations given various tillage treatments

Previously, tillage has been found to reduce early-season phosphorus (P) uptake from soil in continuous maize cropping systems. This reduced P uptake has often been associated with delayed colonization of roots by arbuscular mycorrhizal (AM) fungi. Our aim was to determine if similar responses occur in maize-soybean rotations, which are more typical of current farming in Ontario, Canada. Similar responses were expected because both are AM crops, and the mechanism by which tillage reduces P uptake is thought to be a negative impact on the development of effective mycorrhizae. Simultaneous field experiments with either maize-soybean-maize or soybean-maize-soybean rotations were conducted in 1992–4. Treatments imposed were no-till (NT), ridge-tillage (RT), and conventional tillage using a moldboard plow (MP). In 1993, early-season dry mass of maize was similar among treatments, but colonization of maize roots by AM fungi and P uptake of maize were stimulated by NT and RT, compared with MP. In 1994, early growth was more rapid overall than in 1993, but it was reduced in the NT and RT treatments compared with MP for reasons not related to P. For soybean, AM colonization in NT and RT systems was higher than with MP, but P uptake was unchanged. As was found for maize in 1994, early-season shoot dry mass of soybean was higher in the MP treatment than with NT, but both in 1993 and 1994. We conclude that colonization of both maize and soybean by AM fungi is susceptible to slower development in tilled systems, and that for maize, stimulation of P uptake under reduced tillage can occur in rotations with soybean just as easily as it does with continuous maize. Taken with other studies, the data here suggest that responses to tillage of colonization of roots by AM fungi and of P uptake could apply to many cropping systems. The slow early-season shoot growth seen in some years in response to reduced tillage is discussed.     

Diversity of arbuscular mycorrhizal fungi along a sand dune stabilization gradient: A case study at Praia da Joaquina, Ilha de Santa Catarina, South Brazil

Species diversity of arbuscular mycorrhizal fungi (AMF) was assessed along a dune stabilization gradient (embryonic dune, foredune and fixed dune) at Praia da Joaquina, Ilha de Santa Catarina. The dunes were chosen as a case study to assess whether diversity and mycorrhizal inoculum potential (MIP) increase along the gradient. Ten soil samples were collected from each stage and pooled, and then six 100-g soil sub-samples were taken to identify and enumerate spores. Twelve AMF species were detected, and all three families in Glomales were represented. Gigasporaceae species dominated the embryonic dune, while Glomaceae species dominated the fixed dune. Total spore numbers and richness increased as the dunes became more stabilized. However, indices of Margalef, Simpson and Shannon reached maximal values at different stages, suggesting that species abundance was different among stages. In both embryonic and fixed dunes, species abundance data fit the broken stick model, while in the foredune the log series model best described the data. The MIP followed spore numbers and increased along the gradient, suggesting that spores are important in initiating root colonization in this system. Relationships between edaphic factors and functional roles of Glomales families as determinants of AMF distribution are discussed. This document was subjected to peer and administrative reviews of the U.S. EPA at the National Health and Environmental Effects Research Laboratory, Western Ecology Division, and was approved for publication. Mention of trade names or commercial products in this paper does not constitute endorsement or recommendation of use.     

The growth of external AM fungal mycelium in sand dunes and in experimental systems

We estimated the biomass and growth of arbuscular mycorrhizal (AM) mycelium in sand dunes using signature fatty acids. Mesh bags and tubes, containing initially mycelium-free sand, were buried in the field near the roots of the dune grass Ammophila arenaria L. AM fungal mycelia were detected at a distance of about 8.5 cm from the roots after 68 days of growth by use of neutral lipid fatty acid (NLFA) 16:1ω5. The average rate of mycelium extension during September and October was estimated as 1.2 mm day⁻¹. The lipid and fatty acid compositions of AM fungal mycelia of isolates and from sand dunes were analysed and showed all to be of a similar composition. Phospholipid fatty acids (PLFAs) can be used as indicators of microbial biomass. The mycelium of G. intraradices growing in glass beads contained 8.3 nmol PLFAs per mg dry biomass, and about 15% of the PLFAs in G. intraradices, G. claroideum and AM fungal mycelium extracted from sand dunes, consisted of the signature PLFA 16:1ω5. We thus suggest a conversion factor of 1.2 nmol PLFA 16:1ω5 per mg dry biomass. Calculations using this conversion factor indicated up to 34 μg dry AM fungal biomass per g sand in the sand dunes, which was less than one tenth of that found in an experimental system with Glomus spp. growing with cucumber as plant associate in agricultural soil. The PLFA results from different systems indicated that the biomass of the AM fungi constitutes a considerable part of the total soil microbial biomass. Calculations based on ATP of AM fungi in an experimental growth system indicated that the biomass of the AM fungi constituted approximately 30% of the total microbial biomass. This revised version was published online in June 2006 with corrections to the Cover Date.     

Density and environmental effects on shell size in some sand dune snail populations

Populations ol three species of land snail, Helicella itala. Candidula intersecta and Cochlicella acuta are studied on sand dunes on Coll in the Inner Hebrides.
Population density and mean shell size were estimated on 18 sample sites. The sites were ranked for six environmental factors. Environmental factors which are related to the dune vegetational succession account for much of the variation in the densities of C. intersecta and C. acuta . The density of H. itala , however, shows no strong association with these factors. Both snail density and shell size are reactively independent of total soil calcium levels. For each of the three species, mean shell size is negatively associated with population density; the environmental factors account for little of the variation in shell size.
Four possible mechanisms are suggested to account for the variation of shell size with density. It is argued that a direct influence of density on shell size, possibly mediated by mucus conditioning of the environment is the most probable mechanism. There is some evidence to suggest an inter-specific effect whereby C. intersecta density affects H. itala shell size.     

Density and environmental effects on shell size in some sand dune snail populations

Populations ol three species of land snail, Helicella itala. Candidula intersecta and Cochlicella acuta are studied on sand dunes on Coll in the Inner Hebrides. Population density and mean shell size were estimated on 18 sample sites. The sites were ranked for six environmental factors. Environmental factors which are related to the dune vegetational succession account for much of the variation in the densities of C. intersecta and C. acuta. The density of H. itala, however, shows no strong association with these factors. Both snail density and shell size are reactively independent of total soil calcium levels. For each of the three species, mean shell size is negatively associated with population density; the environmental factors account for little of the variation in shell size. Four possible mechanisms are suggested to account for the variation of shell size with density. It is argued that a direct influence of density on shell size, possibly mediated by mucus conditioning of the environment is the most probable mechanism. There is some evidence to suggest an inter-specific effect whereby C. intersecta density affects H. itala shell size.     

Population dynamics of some major woody species in relation to long-term succession on the dunes of Voorne

This study is a follow-up of medium-term succession studies based on a vegetation map, scale 1:2 500, of the dunes near Oostvoorne made in 1959 and 1980. The area has a marked zonation with partly very young dunes and inner dunes at a distance of >1 200 m from the beach which are 800 yr old. The overall succession trend is a development from a largely open vegetation (resulting from overgrazing in the 19th century, which ceased 1910), to a scrub/woodland complex with locally dying off of patches of woody vegetation. To understand the processes of change, the age structure of most of the major woody species was determined.Two transects were followed in the area running from the seaward coastal ridge towards the inner dunes. 86 plots were analyzed as to represent the vegetation types distinguished in 1980. In each plot all trees and shrubs were estimated on age by means of increment boring and counting of annual rings. The abundance of seedlings and saplings (<4 yr old) of all woody species was estimated in all plots.The most important woody species are Betula (most B. pendula + some B. pubescens). Crataegus monogyna, Rhamnus catharticus, Sambucus nigra, Alnus glutinosa, Quercus robur, Salix(most S. cinerea + S. aurita and their hybrid S. multinervis). Hippophae rhamnoides, Ligustrum vulgare, and Salix repens, three important early successionals, could not be aged easily.Age distribution curves show a marked stand-still in development in the 1960s. Some species stopped rejuvenating at all. Cumulative development curves for different zones show a clear change in growth rate over the zones for Crataegus and a simultaneous rapid development for Crataegus.Two examples of species sequence within a community type are shown. An explanation of these results includes three main factors: (a) overall changes in the whole area related to disturbance and relaxation, (b) soil moisture and (c) rabbit grazing. Two main events in the development of a population are considered: germination and early development of the seedling, and untimely death of a dominant.Nomenclature follows Arnolds & van der Meijden (1976), Standaardlijst van de Nederlandse flora, 1975. Rijksherbarium, Leiden.Research on population dynamics reported on in this paper was carried out by de Cock & de Wildt as MSc students and supervised by van der Maarel, then all at the Division of Geobotany, University of Nijmegen, Nijmegen, The Netherlands. The preparation of the paper including some new observations and calculations were done by the first author in the framework of the project Population dynamics of woody species in primary successions supported by NFR, the Swedish Natural Science Research Council.     

Colonization of the root zone ofAmmophila arenaria by harmful soil organisms

The role of harmful soil organisms in the degeneration ofAmmophila arenaria at coastal foredunes was examined by the growing of seedlings ofA. arenaria in soil samples collected from its root zone. Three sites, each representing a successive stage in foredune succession were examined: (1) a highly mobile dune (sand accretion of 80 cm year⁻¹) with vigorousA. arenaria, colonizing only the upper 30-cm of the annually deposited layer of sand, (2) a mobile dune with vigorousA. arenaria (sand accretion of 22 cm year⁻¹) and a 1-metre soil profile completely colonized by roots and (3) a stable dune (no sand accretion) with degeneratedA. arenaria and young roots mainly present in the upper 0–10 cm. In the upper part of the highly mobile site, the presence of harmful soil organisms was confined to the root layers and at the mobile site for all depth layers a significant growth reduction ofA. arenaria was observed due to the activity of harmful soil organisms. At the stable site, however, growth had only been reduced in some of the depth layers. At all sites newly formed roots ofA. arenaria had been colonized by harmful soil organisms within one year. If present in sand prior to root growth harmful soil organisms reduced root length and root hair formation severely and they enhanced branching of the roots. It is concluded that harmful soil organisms initiate degeneration ofA. arenaria in stable dunes by attack of the root system, which makes the plants suffer from abiotic stress.     

Coastal fore-dune zonation and succession in various parts of the world

A table is presented of the most important species of the fore-dune complex in various parts of the world, representing all continents. The complex is divided into six zones or habitat types, which have proved to be widely applicable for this purpose. The zones are briefly described in terms of floristics, geomorphology, ecology (sand movement, salinity, organic matter) and climate. A major division is indicated between tropical (including subtropical) and temperate (including cold) regions. The former are subdivided into those with humid and those with arid climates, the latter into those with cool to warm-temperate and those with boreal to subarctic climates. The highest, most extensive and most complicated dune areas occur in those regions where the effects of disturbance by wind and fixation by plant growth are about equally strong. A number of species show the retraction phenomenon: a shift from a certain zone towards a more sheltered zone in an area with more harsh conditions (e.g. a shorter vegetation period). The filling of empty niches by introduced species (e.g. in connection with the scarcity of native tidemark species in temperate Australia) is also quite common. Most communities are rich in (sub)cosmopolitan species.Nomenclature: see various regional references.     

Changes in the flora and vegetation of the coastal dunes of Voorne (The Netherlands) in relation to environmental changes

Ecologically the former isle of Voorne is very varied. This is reflected by an exceptionally high number of plant species and vegetation types. Many data regarding flora and vegetation have been collected during more than 25 years. A comparison of the early and the later data show that in this period many changes have taken place in flora and vegetation. The changes are partly the result of a natural development of the vegetation, but to a considerable extent they are due to human activities in the coastal area itself and in its surroundings. Examples of changes produced by natural developments and by human activities are given. The effects on flora and vegetation of the area are illustrated by comparing flora inventories, vegetation maps and permanent plot studies. In addition, the future development in the region which will strongly affect its natural value, is discussed.I would like to thank Michiel Boeken, Joke van der Linden and Elly van Oosterhoud who carried out the second flora inventory and Jeanette van Beuzekom and Inge Boelens who mapped parts of the Voorne dune area. I am particularly indebted to Wiecher Smant who offered assistance in many ways.     

菌根技术在沙地植被恢复中的研究

库布齐沙地植被恢复中的菌根技术研究 ,注重于因地制宜、适菌适技。对此 ,利用当地A、B两种沙壤条件并对其作加入草炭和不加入草炭条件处理 ,选用适合当地造林树种油松、樟子松进行室内模拟实验及野外实地小型造林试验 ,菌剂以单菌剂、组合菌剂方式实施。室内模拟试验结果表明 ,单菌剂对油松幼苗作用效果为 :Cr >Ra >Li>Hm。双组合菌剂Ra Li、Hm Li和Ra Cr接种的幼苗对草炭的依赖性不强。选择出Cr和Ra菌根菌剂为沙地植被恢复较为适合的菌剂。油松和樟子松两树种无论施单菌剂或双组合菌剂 ,油松幼苗长势均优于樟子松幼苗。造林试验结果表明 ,在同一块样地菌剂处理 ,三合一优于二合一菌剂组合。接种菌根菌剂幼苗地上生物量高于施入复混肥的幼苗。不同样地菌剂处理的幼苗成活率在个别菌剂组合中低于复混肥。因个别菌剂培养周期不足而致使其菌丝体与基质发酵不完全 ,而遇到造林基地干旱 ,土壤温度升高 ,导致基质仍再发酵、腐熟 ,这就使部分生长较弱的幼苗受到了伤害 ,因而幼苗成活率低。