Diversity and Abundance of Biological Soil Crust Taxa in Relation to Fine and Coarse-Scale Disturbances in a Grassy Eucalypt Woodland in Eastern Australia

Over the last 200 years the box woodlands of eastern Australia have been considerably altered by European farming practices. These changes have been accompanied by a reduction in the size and number of patches of vegetation as well as the quality of the understorey vegetation and underlying soil surface. We measured diversity and abundance of soil crust taxa in relation to habitat complexity, remnant area and width, diversity of vascular plants as well as the number, size and separation of patches of vegetation and grass butts (coarse-scale patchiness), and an index of surface stability derived from measures of seven soil surface features of small microsites (patches of bare/crusted, litter- or grass-covered soil; micro-scale) on both coarse- and fine-textured soils at 35 sites in south-eastern Australia. Fifty taxa were recorded from the 35 sites, and there were more taxa from sites with fine-textured soils (12.7) compared with coarse-textured soils (4.4). The soil crust community was dominated by a few relatively common species, with many species occurring at only a few sites. Half the number of species accounting for <1% of total abundance. Bare and crusted microsites supported more species and greater cover compared with grassy microsites. Crust diversity declined with increasing coarse-level disturbances (i.e. declines in habitat complexity, remnant area and width, and diversity of vascular plants) but the results were not consistent between soil types. No measures of fine-scale disturbance were related significantly to any of the crust diversity or abundance measures, and there was no evidence of a recent grazing effect on crust composition. The fact that few sites had many species (and visa versa) suggests to us that many sites are probably required to conserve soil crust taxa in these highly fragmented landscapes     

Success criteria and adaptive management for a large-scale wetland restoration project

We are using a 20+ year photographic history of relatively undisturbed and formerly diked sites to predict the restoration trajectories and equilibrium size of a 4,050 ha salt marsh on Delaware Bay, New Jersey (USA). The project was initiated to offset the loss of finfishes from once-through cooling at a local power plant. We used a simple food chain model to estimate the required restoration size. This model assumed that annual macrophyte detritus production and benthic algal production resulted in production of finfishes, including certain species of local interest. Because the marsh surface and intertidal drainage system are used by many finfishes and are the focal points for exchange of detrital materials, the restoration planning focused on both vegetational and hydrogeomorphological parameters. Recolonization bySpartina spp. and other desirable taxa will be promoted by returning a natural hydroperiod and drainage configuration to two types of degraded salt marsh: diked salt hay (Spartina patens) farms and brackish marsh dominated byPhragmites australis. The criteria for success of the project address two questions: What is the bound of expectation for restoration success, and how long will it take to get there? Measurements to be made are macrophyte production, vegetation composition, benthic algal production, and drainage features including stream order, drainage density, channel length, bifurcation ratios and sinuosity. A method for combining these individual parameters into a single success index is also presented. Finally, we developed adaptive management thresholds and corrective measures to guide the restoration process.Corresponding editor: R.E. Turner     

Geochemical parameters of sedimentation and the distribution of Silurian brachiopod communities in Lithuania

Silurian rocks from borehole cores in the Baltic Basic were analyzed for Si, Al, Ti, Fe, Ca and Mg oxide content and chemical data were related to sedimentary environment, lithology and brachiopod community distribution. Evaluation of these relationships enables precise positioning of closely related communities within Boucot's (1975) brachiopod Benthic Assemblages. Preliminary attempts are made to evaluate climatic change based on Al/Ti oxide ratios.     

Impacts of tourism on threatened plant taxa and communities in Australia

Summary Many Australian plant species and communities appear to be threatened by tourism. A review of management plans, recovery plans and a survey of experts found that tourism was considered to be a direct or indirect threatening process for 72 plant taxa. This is one fifth of threatened species for which threats have been identified. In addition, many more species are listed as threatened by weeds, trampling, pathogens, clearing and collecting. These are often indirect impacts of tourism, particularly in conservation reserves where tourism is the only commercial activity permitted. Tourism was also considered to be a threatening process for several plant communities. A lack of recognition of the importance of direct and indirect impacts of tourism may potentially hinder the conservation of plant species and communities both in Australia and overseas. It may also limit the effectiveness of sustainable tourism policies, particularly in conservation reserves.     

Patch distribution and dispersal limitation of four plant species in Swedish semi-natural grasslands

This study examined whether the patch distribution of four plant species Agrimonia eupatoria, Carlina vulgaris, Hypochoeris maculata and Plantago media were affected by dispersal limitation. Analysis of the patch size/isolation relationship was combined with a seed sowing experiment examining the recruitment of the species. Patch size was negatively correlated to isolation in Carlina, Hypochoeris and indicating that dispersal processes might affect the distribution pattern. Patch size of Agrimonia was not correlated, or in one case positively correlated, to isolation. Agrimonia was also the only species among the four where the recruitment not was affected by disturbance treatment or locality. The recruitment of Carlina, Hypochoeris and Plantago was higher in disturbed plots compared to undisturbed, and the latter two species were also affected by locality. This suggests that Agrimonia is less sensitive to isolation (and the ongoing fragmentation of the landscape) compared to the other three species, probably due to better dispersal and recruitment ability. We conclude in a discussion how different management strategies could serve to maintain viable populations of these species. This revised version was published online in August 2006 with corrections to the Cover Date.     

Rare, threatened and alien species in the gastropod communities in the clay pit ponds in relation to the environmental factors (The Ciechanowska Upland, Central Poland)

The objectives of the present survey were to formulate a zoocenological analysis of the gastropod communities in clay pit ponds, as well as to determine the relationships between the gastropods and their environments, and to evaluate the water habitats in terms of their ecological-conservation value. The physical and chemical parameters of water, gastropod species and macrophytes occurring in the ponds indicate mesotrophic conditions. Principal Component Analysis (PCA) reveals a correlation between gastropod density and nitrates, a correlation between gastropod density and alkalinity, and additionally shows a correlation between gastropod density and chlorides. The pond surface area, nitrates, chlorides concentrate, alkalinity, and substratum have all affected these gastropod communities. The occurrence of the first permanent population of Ferrissia clessiniana (Jickeli, 1882) was recorded in Poland. Valvata naticina Menke 1845 has become a critically rare species (CR) due to the pollution of water environments. Five other species, e.g. Anisus vorticulus (Troschel, 1834) and Planorbis carinatus O.F. Müller, 1774 are recorded on the Polish Red List of Species. The clay pit ponds of the Ciechanowska Upland, because of their distinctive environmental features, provide a refuge where a number of rare, threatened and alien gastropod species live.     

Some vicariating plant communities in Brazil,Malaysia and Singapore

Dune communities with dominant Ipomoea pes-caprae (coastal strand vegetation) and communities with dominant Gleicheiniaceae (fern communities of forest borderlines) were distinguished and comparatively studied in Brazil, Malaysia and Singapore, and compared with similar stands around the world. A total of 71 vegetation relevés was collected. In coastal dune vegetation, the new associations Ipomoeo pediscaprae-Sporoboletum virginicae was distinguished for Brazil, and the vicariant Wedelio biflorae-Ipomoeetum pedis-caprae is described from Malaysia and Singapore. The vegetation of forest borderlines is characterized in Brazil by the new association Lycopodio cernuui-Gleicheinietum bifidae, which was subdivided in two subassociations (droseretosum capillaris and typicum). A physiognomically similar community was detected and described in Malaysia and Singapore as the new association Lycopodio cernuui-Dicranopteridetum curranii with two subassociations (typicum and dicranopteridetosum linearis).     

Arbuscular mycorrhiza in relation to management history,soil nutrients and plant species diversity

Thelow nutrient status of semi-natural grasslands, pastures and meadows,reflects a continuity of nutrient reduction by grazing and hay-making. Ithas been hypothesized that the nutrient depletion itself may reduce competitionbetween individuals, and that mycorrhiza smooths out differences in nutrientuptake and competitive ability, so that competition for nutrients is evenfurther reduced. This interaction between site history, nutrient status andmycorrhiza could thus be one explanation for a high species diversity usuallyfound in semi-natural grasslands. To determine variation in colonizationof arbuscular mycorrhizal fungi (AM), three species(Achillea millefolium L., Ranunculusacris L. and Anthriscus sylvestris L.) weresampled at sites with different management history. All three species hadmycorrhizal colonization. Correlations between species diversity patterns atdifferent spatial scales (0.04,1 and total species number in the site) andmycorrhizal colonization were examined. In addition, soil samples were analysedconcerning P, K, N and pH. When combining measures for the three speciestogether there were significantly higher AM colonization at sites with a longcontinuous management regime, compared to sites with short or interruptedmanagement regime. A significantly positive correlation was also found betweenplant species diversity and colonization of mycorrhiza. Soil nutrient status androot weight density did not differ among the sites with different managementregime. This indicates that increasing nutrient status, or root competition, arenot likely causal mechanisms behind a reduced AM colonization rate at sites withshort or interrupted management regime. The correlation with species diversityis more likely a result of management continuity itself. A long continuousmanagement is associated with an increasing likelihood of successful dispersalof plant species as well as of fungal species.     

Environmental and anthropogenic factors associated with coastal wetland differentiation in La Mancha,Veracruz, Mexico

At least 10% of the wetlands in Mexico are situated in the State of Veracruz on the central Gulf coast. The region has been intensively used for agriculture by humans for the last thousand years and today pastureland for cattle ranching is the dominant element of the landscape. We present a study of the wetland vegetation in a series of representative and internationally significant freshwater wetlands near the coastal lagoon La Mancha in Veracruz State. We obtained eleven wetland types formed by three wetland communities dominated by trees (mangrove or swamps), eight dominated by herbaceous species which we classified as marsh, five of which were native emergent marsh, one was a non-native emergent marsh and two were floating-leaved marsh. The highest diversity values were found in the Annona swamp, followed by the Sagittaria marsh and the Rhizophora–Laguncularia–Avicennia mangrove. CCA ordination showed that water level, disturbance and species number were the major factors explaining variation along axis 1, and on axis 2 conductivity, salinity, and bulk density. Wetland size was a major factor in both axes. We examined the interplay of intrinsic and extrinsic factors that give rise to the nature and diversity of wetland types that characterize the important wetland landscapes in this part of Mexico, being disturbance by human activities an important factor that favors the appearance of diverse species combinations.     

Vertebrate browsing impacts in a threatened montane plant community and implications for management

Montane ecosystems are vulnerable to the removal of vegetation cover through browsing by feral or native vertebrate fauna. The highest elevated peaks of the Stirling Range in Western Australia provide habitat for an endemic plant community, Critically Endangered due to plant disease, frequent fire and an emerging threat of browsing by vertebrate fauna. Survey and camera trapping confirmed the herbivorous feral Rabbit (Oryctolagus cuniculus) and native Quokka (Setonix brachyurus) are present. Dietary analysis through faecal examination revealed contrasting diets and implicates native rather than feral species as responsible for impacts on dicotyledonous species, and in particular those of conservation significance. Exclosure experiments conducted over 1 year revealed significant changes in abundance, cover and height of perennial herbs and an increase in growth and/or reproduction of four threatened endemic plants. Detrimental impacts caused by native browsing fauna are not unprecedented and may be attributed to disequilibria in ecosystem processes due to multiple interacting threats. Montane ecosystems may be particularly vulnerable to browsing due to their naturally slow recovery after disturbance and browsing may also create environmental conditions more conducive to plant disease. For plant species with critically low population numbers, the impact of browsing poses a threat to population persistence and undermines investment into other conservation recovery actions. For effective management, it is critical to determine the relative impact of browsing species present. Where native species are implicated, the physical protection of high value assets in wire exclosures is warranted to complement other recovery actions and ensure effective species and community recovery.     

Germination and water dispersal of seeds from a threatened plant species Penthorum chinense

To conserve a threatened plant species (Penthorum chinense Pursh) in Japan, seed germination responses to pretreatment (imbibition and/or chilled), temperature and light, and seed dispersal by water were examined. The seeds collected from abandoned paddy fields in a warm temperate region, central Japan, germinated in light (14 h photoperiod; light 22°C, dark 21°C) after a moist-chilled treatment. After this pretreatment, the seeds germinated well at 10–25°C (optimum temperature 15°C), but did not germinate in darkness even at the optimum temperature. Most of the seeds floated on distilled water, but 20–60% of the seeds that were collected from several populations sank in distilled water, indicating dimorphism in seed dispersal by water. The floating and sunken seeds did not show significant differences in weight and germination rate within a population. The addition of a surface-active agent in distilled water submerged the seeds, indicating that the buoyancy of the seeds is attributable to an oil coating on the seed surface that enhances the interfacial tension on the seeds. Three times the number of seeds sank in river water collected from a rural area than in distilled water. A greater number of seeds also sank in water that had increasing concentrations of linear alkylbenzenesulfonate, which is a major component of synthetic detergents. This suggests that the water dispersal of this species is suppressed by surface-active agents, including detergents, in river water.     

Rare and infrequent southern African grasses: assessing their conservation status and understanding their biology

The taxonomic treatment for the grasses of southern Africa was one of the first to be based on computerised data and the DELTA system. These data, based on over 70,000 herbarium records, are amenable for analysis of species parameters including abundance, frequency and distribution. This information is suitable for the allocation of species into the seven categories of rarity proposed by Rabinowitz using a combination of habitat specificity (“Narrow” or “Broad”), population structure (“Sparse” or “Abundant”) and distribution (“Restricted” or “Widespread”). We compare the species lists obtained for each combination of these three aspects to published Red Data Lists (RDLs) for southern and South Africa. Ninety-three species are placed in the most sensitive or potentially threatened category (Narrow habitat, Sparse populations and Restricted distributions; RSN). This is substantially more than the number of species listed in current RDLs for the region. Chi-square tests indicate a statistically significant bias in taxa from the Fynbos Biome for three of the categories (RSN, RAN and WSN), from the Savanna Biome for the WAN category and from the arid Succulent Karoo and Desert Biomes for the RAB category. Analyses of habitat requirements indicate that many grasses listed (especially those associated with a “Narrow” habitat) are found in some form of wetlands (ephemeral or permanent), especially those at higher altitudes (montane). Despite concerns about the subjective nature in determining the boundaries between the categories, this method is shown to provide a meaningful and valuable list of taxa that require prioritisation for more detailed assessment according to the IUCN criteria.     

Recovering threatened plant species and their habitats: The need for integrated action

As an introduction to the Special Issue on the restoration of threatened plant species and their habitats,this editorial shows how the various papers in the issue address the range of in situ interventions involved in species population management and restoration of their habitat, together with examples of case studies implementing these actions. It stresses the need for integrating these various interventions.It highlights the importance of protected areas in providing a degree of protection for threatened species but also the need to complement this with actions at the species level to ensure the effective conservation and long term persistence of these species. It emphasizes that ecological restoration is a complement to, not a substitute for conservation, and that the balance of effort and allocation of resources between them is a key issue.     

The role of a native tussock grass (Paspalum quadrifarium Lam.) in structuring plant communities in the Flooding Pampa grasslands, Argentina

The patches of Paspalum quadrifarium-dominated grasslands found atpresent could be remnants of the vegetation that defined the Pampas landscape inthe past. The mere presence of such physical structures should lead to systemsin which many other species are dependent upon both the autogenic creation ofsurface area for living space and the autogenic and allogenic modulation ofresources controlled by these structures. We carried out amensurative–comparative study in naturally occurring sites dominated byP. quadrifarium that occupy different positions within thelandscape in the Flooding Pampa. We found different species assemblages in thesestructurally homogeneous stands, related to the edaphic and topographicgradients. The comparison with sites from similar positions in the landscapewhere this native tussock-grass was absent showed that the dominance ofP. quadrifarium is a minor determinant of floristicdifferences, which are mainly controlled by abiotic factors. We assigned thesedominated grassland stands to previously delimited vegetation units for theFlooding Pampa grasslands and we compared them with the vegetation unitsassigned, in terms of composite properties of the community that may beindicators of ecosystem processes, such as biological invasions andproductivity. Our results show that this native tussock grass is associated withhigher floristic richness, higher representation of perennials and grasses andlower presence of alien plants. This homogeneous pattern of variation across thevegetation units would suggest that, despite the absence of dramatic changes incommunity composition, the dominance of this tussock grass plays an importantrole in structuring species diversity patterns.     

Callus induction and plant regeneration in Vetiveria zizanioides

Callus induction was obtained from basal parts of Vetiveria zizanioides Stapf. leaves cultured on Murashige and Skoog (MS) medium supplemented with 9.0 M 2,4-dichlorophenoxyacetic acid (2,4-d), 5.7 M indoleacetic acid (IAA) and 4.6 M kinetin. Calli were maintained on MS medium with the addition of 0.9 M 2,4-d and 2.3 M kinetin. Shoot formation was obtained from fast growing 14-day-old callus on the same basal medium supplemented with 0.9 M 2,4-d and 9.3 M kinetin. Embryo-like structures were observed. When transferred to basal medium, shoots readily developed roots. Fully developed regenerated plants were then successfully established in soil.     

Long-term change in limnology and invertebrates in Alaskan boreal wetlands

Climate change is more pronounced at high northern latitudes, and may be affecting the physical, chemical, and biological attributes of the abundant wetlands in boreal forests. On the Yukon Flats, located in the boreal forest of northeast Alaska, wetlands originally sampled during 1985–1989 were re-sampled for water chemistry and macroinvertebrates in summer 2001–2003. Wetlands sampled lost on average 19% surface water area between these periods. Total nitrogen and most metal cations (Na, Mg, and Ca, but not K) increased between these periods, whereas total phosphorus and chlorophyll a (Chl a) declined. These changes were greater in wetlands that had experienced more drying (decreased surface area). Compared with 1985–1989, densities of cladocerans, copepods, and ostracods in both June and August were much higher in 2002–2003, whereas densities of amphipods, gastropods, and chironomid larvae were generally lower. In comparisons among wetlands in 2002–2003 only, amphipod biomass was lower in wetlands with lower Chl a, which might help explain the decline of amphipods since the late 1980s when Chl a was higher. The decline in Chl a corresponded to greatly increased zooplankton density in June, suggesting a shift in carbon flow from scrapers and deposit-feeders to water-column grazers. Declines in benthic and epibenthic deposit-feeding invertebrates suggest important food web effects of climate change in otherwise pristine wetlands of the boreal forest. Handling editor: R. Bailey     

Effects of plant species richness and composition on epifaunal colonization in brackish water angiosperm communities

Studies conducted in terrestrial ecosystems have shown that increasing plant diversity enhances ecosystem processes such as primary production. In marine systems, knowledge of how plant diversity influences ecosystem processes and higher trophic levels is still limited. To examine how plant richness and composition influence recruitment and colonization processes, defaunated eelgrass (Zostera marina), sago pondweed (Potamogeton pectinatus) and perfoliate pondweed (Potamogeton perfoliatus) were planted on an unvegetated, sandy bottom in all possible combinations in July and August. Both field experiments lasted 1 week. Our results showed that in these plant assemblages plant richness had a negative effect on faunal diversity (H′) and evenness (J′), while total abundance showed strong temporal variation with weak, positive relationships with plant species richness in both August and July. Plant species composition had strong effects on amphipods (Gammarus spp.), thus both the abundance and biomass were higher in treatments containing P. perfoliatus. The colonization process was significantly influenced by the numerical dominance of a few faunal species, e.g. the settlement of lagoon cockles (Cerastoderma glaucum), and by the timing of the experiments. The results indicate that faunal colonization in these communities is rapid and significantly influenced by the traits of particular plant species.