Clonal ability,height and growth form explain species’ response to habitat deterioration in Fennoscandian wooded meadows

Fennoscandian calcareous wooded meadows have high conservation value due to very high diversity which has been maintained by consistent mowing, but undergo species loss when this management is abandoned. We compared species richness and composition of regularly mown and abandoned wooded meadows in Estonia and established species groups with respect to their response to abandonment. These meadows were very species rich with a maximum of 43 species per 0.25 m². Species whose populations are maintained by mowing constituted >60 % of the floristic diversity of the mown wooded meadows. Abandonment suppressed species with a preference for dry infertile open habitats. Response to abandonment was related to clonality, height and growth form. The greatest negative response was associated with low graminoids, short-lived and non-clonal species, rosette and semi-rosette growth form. Weak competitors with low height and light seeds exhibited a slow decline; perennial life span and clonality enable a delay in local extinction of these species. Response groups had similar persistence at a national level, revealing that earlier assessment of species dynamics at larger spatial scales could underestimate the number of threatened species. Application of restoration measures could avoid local extinctions of many mowing-supported species, whereas some of the mowing-dependent species likely need reintroduction.     

Aspect-vegetation complex effects on biochemical characteristics and decomposability of soil organic carbon on the eastern Qinghai-Tibetan Plateau

Background

Meadows and shrublands are two major vegetation types on the Qinghai-Tibetan Plateau, but little is known about biochemical characteristics and its relation to decomposability of soil organic carbon (OC) under these two vegetation types. The present study was designed to evaluate effects of aspect-vegetation complex on biochemical characteristics and decomposability of soil OC.

Methods

Two hills were randomly selected; both with vegetation being naturally divided into southward meadows and northward shrublands by a ridge, and soils were sampled at depths of 0–15 and 15–30 cm, along contours traversing the meadow and shrubland sites. Particulate (particle size 2–0.05 mm) OC and nitrogen (N), microbial biomass C and N, non-cellulosic sugars, and CuO lignin were analyzed, and OC mineralization was measured for 49 days at 18 and 25 °C under laboratory incubation, respectively.

Results

More than half of soil OC was present as particulate fraction across all samples, indicating the coarse nature of soil organic matter in the region. Averaging over depths, shrublands contained 87.7???114.1 g OC and 7.7???9.3 g N per kg soil, which were 63???78 and 26???31 % higher than those in meadows, respectively. Meanwhile the C/N ratio of soil organic matter was 11.4???12.3 under shrublands, being 29???40 % higher than that under meadows. Soil OC under meadows was richer in noncellulosic carbohydrates and microbial biomass in the 0–15 and 15–30 cm depths but contained less lignin in the 15–30 cm depth. Ratios of microbially- to plant-derived monosaccharides and between acid and aldehyde of the vanillyl units were greater in soils under shrublands, showing more abundant microbially-derived sugars and microbially-transformed ligneous substances in OC as compared to meadow soils. By the end of 49 days’ incubation, total CO₂–C evolution from soils under meadows was 15.0–16.2 mg g^?1 OC averaging over incubation temperatures and soil depths, being 27–55 % greater than that under shrublands. Across all soil samples over two sites, total CO₂ ? C evolved per g OC at either 18 or 25 °C was closely correlated to enrichments of noncellulosic carbohydrates and microbial biomass. This indicates that the greater soil OC decomposability under meadows was associated with its larger abundances of readily mineralizable fractions compared with shrublands. However, temperature increase effect on soil OC decomposability did not differ between the two types of vegetation.

Conclusions

Our findings suggest that the aspect-vegetation complex significantly affected pool size, biochemical characteristics, and decomposability of soil OC on the northeastern edge of Qinghai-Tibetan Plateau. However, the response of soil OC decomposability to temperature was similar between southward meadows and northward shrublands.     

Why are many anthropogenic agroecosystems particularly species-rich?

Species-rich meadow and pasture habitats are recognised by the European Union Habitats Directive as targets for biodiversity conservation. High species richness is hypothesised to be associated with diversity in plant functional traits and life-history strategies, which are potentially restricted in situations of extremely high and low biomass production. However, variability in functional traits has yet to be investigated across a broad biomass range in nature. We measured variability in a range of functional traits and Grime's competitor, stress-tolerator, ruderal (CSR) strategies for species comprising lowland meadows, subalpine pastures, abandoned grassland and field margins at sites in northern Italy, alongside peak above-ground biomass. The factor most highly and positively correlated with species richness was strategy richness (the number of CSR strategies; Pearson's r = 0.864, P < 0.0001, n = 39), followed by variance in traits involved in leaf resource economics and the timing of flowering. Species richness, trait variance and strategy richness were greatest at intermediate biomass. Thus whilst extremes of biomass production were associated with relatively few taxa exhibiting similar trait values and specialised strategies, greater species richness was apparent in meadows and pastures in which species exhibited divergence in resource economics trait values, reproductive timing and strategy richness.     

Transpiration in seven plant species colonizing a fishpond shore

In 7 species (Eleocharis palustris R. Br.,Juncus bufonius L.,Gypsophila muralis L.,Trifolium repens L.,Agrostis stolonifera L.,Potentilla anserina L. andAchillea millefolium L.) growing in a gradient of habitats from aquatic to terrestrial, on a sandy fishpond shore in Southern Bohemia, Czechoslovakia, the daily course of transpiration rate and water content was assessed gravimetrically in their cut-off transpiring parts on two typical summer days. Transpiration rate was largely controlled by microclimate but depressions occurred inJuncus and in some species growing in the drier habitats. The highest instantaneous transpiration rate and total daily transpiration per unit dry weight, about 100 mg g^?1 min^?1 and 50 g g^?1 d^?1, respectively, were recorded inAchillea andTrifolium. The water turnover rate ranged from 16.1 g g^?1 (H₂O) d^?1 inJuncus to 10.7 inGypsophila. The estimated daily maximum water saturation deficit was highest inEleocharis (45.7%) and lowest inAchillea (15.0%). The adaptational significance of the observed phenomena is discussed.     

Early responses of drought-resistant and -susceptible tomato plants subjected to water stress

Three-week-old seedlings of one drought-susceptible tomato cultivar (Lycopersicon esculentum cv. “New Yorker”) and two drought-resistant species of tomato (Solanum pennellii andLycopersicon chilense) were subjected to various degrees of PEG 8000-induced water stress from ?0.017 to ?1.0 MPa for a duration of 24 h so that their early responses to water stress could be compared. Such a comparison would determine if there was a relationship to root cytokinin levels following sudden induction of water stress in the drought-resistant species. Transpiration rates of leaves were monitored throughout the 24-h period, shoots were evaluated for leaf water potential (LWP), and roots were extracted for levels oft-zeatin riboside (t-ZR) and dihydrozeatin riboside (DHZR) using a monoclonal antibody enzyme immunoassay. Transpiration rates were evaluated gravimetrically by difference every 6 h up to 24 h. Transpiration rate decreased with increasing PEG levels and passage of time in all three species, measured at 6 and 12 h, logarithmically in the case of the twoLycopersicon species and linearly in the case ofSolanum. From 12–18 h (while plants were in darkness), transpiration rate was a function of the level of PEG only and not time in all three species. When light resumed from 18–24 h, only 5.pennellii showed no further decrease in transpiration rate over time with increasing PEG. Drought-susceptibleL. esculentum had a stronger linear decrease in LWP with increasing PEG 8000 concentration than the other two species.L. esculentum also had a higher initial transpiration rate than did either of the drought-resistant species. The two drought-resistant species showed less change in LWP with 5.pennellii having a small decrease andL. chilense having little change. OnlyS. pennellii exhibited a decrease in roott-ZR levels, which may imply a role for root cytokinin within the first 24-h exposure to water stress in this species.L. esculentum exhibited no change in roott-ZR. The levels oft-ZR inL. chilense were less than that ofL. esculentum but showed only a slight decrease with increasing PEG.S. pennellii andL. chilense, although both drought-resistant tomato species, showed different patterns of response with respect to pattern of decline in transpiration rate, LWP, and roott-ZR levels.     

Differences in flooding tolerance between species from two wetland habitats with contrasting hydrology: implications for vegetation development in future floodwater retention areas

Background and Aims

Plants need different survival strategies in habitats differing in hydrological regimes. This probably has consequences for vegetation development when former floodplain areas that are currently confronted with soil flooding only, will be reconnected to the highly dynamical river bed. Such changes in river management are increasingly important, especially at locations where increased water retention can prevent flooding events in developed areas. It is therefore crucial to determine the responses of plant species from relatively low-dynamic wetlands to complete submergence, and to compare these with those of species from river forelands, in order to find out what the effects of such landscape-scale changes on vegetation would be.

Methods

To compare the species'' tolerance to complete submergence and their acclimation patterns, a greenhouse experiment was designed with a selection of 19 species from two contrasting sites: permanently wet meadows in a former river foreland, and frequently submerged grasslands in a current river foreland. The plants were treated with short (3 weeks) and long (6 weeks) periods of complete submergence, to evaluate if survival, morphological responses, and changes in biomass differed between species of the two habitats.

Key Results

All tested species inhabiting river forelands were classified as tolerant to complete submergence, whereas species from wet meadows showed either relatively intolerant, intermediate or tolerant responses. Species from floodplains showed in all treatments stronger shoot elongation, as well as higher production of biomass of leaves, stems, fine roots and taproots, compared with meadow species.

Conclusions

There is a strong need for the creation of temporary water retention basins during high levels of river discharge. However, based on the data presented, it is concluded that such reconnection of former wetlands (currently serving as meadows) to the main river bed will strongly influence plant species composition and abundance.Key words: Acclimation, biomass allocation, climate, complete submergence, flooding tolerance, retention areas, shoot elongation, soil flooding, waterlogging, wetland species     

Water relations pattern of understorey species influenced by sunflecks

Water relations of plant cenopopulations of understorey species (7 herbaceous perennials, 1 shrub, and 1 tree seedling) growing in an oak-hornbeam forest in SW. Slovakia is markedly influenced by natural sunflecks moving on the forest floor, where stomatal conductance and transpiration rate are significantly higher than in shade areas. In the course of a day, the leaf stomatal conductance fluctuates, following irradiance of the leaf, from minimum in full shade to maximum in sunflecks, including intermediate values in transient conditions. Therefore, there is also a large variability in water saturation deficit and transpiration rate within the cenopopulations of the understorey species. These variations should be considered in modelling the physiology of woodland understorey species.     

Does the Aboveground Herbivore Assemblage Influence Soil Bacterial Community Composition and Richness in Subalpine Grasslands?

Grassland ecosystems support large communities of aboveground herbivores that are known to directly and indirectly affect belowground properties such as the microbial community composition, richness, or biomass. Even though multiple species of functionally different herbivores coexist in grassland ecosystems, most studies have only considered the impact of a single group, i.e., large ungulates (mostly domestic livestock) on microbial communities. Thus, we investigated how the exclusion of four groups of functionally different herbivores affects bacterial community composition, richness, and biomass in two vegetation types with different grazing histories. We progressively excluded large, medium, and small mammals as well as invertebrate herbivores using exclosures at 18 subalpine grassland sites (9 per vegetation type). We assessed the bacterial community composition using terminal restriction fragment length polymorphism (T-RFLP) at each site and exclosure type during three consecutive growing seasons (2009–2011) for rhizosphere and mineral soil separately. In addition, we determined microbial biomass carbon (MBC), root biomass, plant carbon:nitrogen ratio, soil temperature, and soil moisture. Even though several of these variables were affected by herbivore exclusion and vegetation type, against our expectations, bacterial community composition, richness, or MBC were not. Yet, bacterial communities strongly differed between the three growing seasons as well as to some extent between our study sites. Thus, our study indicates that the spatiotemporal variability in soil microclimate has much stronger effects on the soil bacterial communities than the grazing regime or the composition of the vegetation in this high-elevation ecosystem.     

Growth and photosynthetic responses of soybean seedlings to maize shading in relay intercropping system in Southwest China

Intercropping, a traditional and worldwide cropping practice, has been considered as a paradigm of sustainable agriculture based on complementary mechanisms among different crop species. Soybean (Glycine max) is widely relay intercropped about 60 days before maize (Zea mays) harvest in Southwest China. However, shade caused by tall maize plants may be a limiting factor for soybean growth at a seedling stage. In field research, we studied the ecophysiological responses of two widely cultivated soybean varieties [Gongqiudou494-1 (GQD) and Gongxuan 1 (GX)] to maize shading in a relay intercropping system (RI) compared with monocropped soybean plants (M). Our results showed that soybean seedlings intercropped with maize exhibited significantly downregulated net photosynthetic rate (P _N) (?38.3%), transpiration rate (?42.7%), and stomatal conductance (?55.4%) due to low available light. The insignificant changes in intercellular CO₂ concentration and the maximum efficiency of PSII photochemistry suggested that the maize shading-induced depressions in P _N were probably caused by the deficiency of energy for carbon assimilation. The significantly increased total chlorophyll (Chl) content (+27.4%) and Chl b content (+52.2%), with lowered Chl a/b ratios (?20.5%) indicated soybean plants adjusted their light-harvesting efficiency under maize shading condition. Biomass and leaf area index (LAI) of seedlings under RI decreased significantly (?78.7 and ?71%, respectively) in comparison with M. Correlation analysis indicated the relative reduction in biomass accumulation was caused by the decline in LAI rather than P _N, it affected negatively the final yields of soybean (32.8%). Cultivar-specific responses to maize shading were observed in respects of LAI, biomass, and grain yield. It indicated that GX might be a better cultivar for relay intercropping with maize in Southwest China.     

Halimeda biomass,growth rates and sediment generation on reefs in the central great barrier reef province

The average biomass ofHalimeda per m² of solid substratum increased progressively on a series of reefs situated at increasing distances from the shore in the central Great Barrier Reef. There was none on a reef close inshore, increasing to nearly 500 g m^?2 total biomass (?90% calcium carbonate) on an oceanic atoll system in the Coral Sea. The biomass measured contained 13 species ofHalimeda but was dominated by only two species,H. copiosa andH. opuntia, except on the atoll whereH. minima was dominant. Three sand-dwelling species were also present but did not occur anywhere in substantial quantities. Growth rates of the dominant species were measured bv tagging individual branch tips. A mean value of 0.16 segments d^?1 was recorded but 41% of the branch tips did not grow any new segments whilst only 1% grew more than one per day. The number of branch tips per unit biomass was very constant and has been used in conjunction with growth rates and biomass to calculate productivity rates, and thence sedimentation, in the lagoon of one of the reefs. Biomass doubling time of 15 d and production of 6.9 g dry wt m^?2 d^?1 are considerably higher than previously reported values forHalimeda vegetation and there was little seasonal change detected over a whole year. Those values indicate annual accretion of 184.9 g m^?2 year^?1 ofHalimeda segment debris over the entire lagoon floor (5.9 km²) of Davies Reef, equivalent to 0.13 mm year^?1 due toHalimeda alone, or 1 m every 1,892 years when other contributions to that sediment are taken into account.     

Plant and arthropod community sensitivity to rainfall manipulation but not nitrogen enrichment in a successional grassland ecosystem

Grasslands provide many ecosystem services including carbon storage, biodiversity preservation and livestock forage production. These ecosystem services will change in the future in response to multiple global environmental changes, including climate change and increased nitrogen inputs. We conducted an experimental study over 3 years in a mesotrophic grassland ecosystem in southern England. We aimed to expose plots to rainfall manipulation that simulated IPCC 4th Assessment projections for 2100 (+15 % winter rainfall and ?30 % summer rainfall) or ambient climate, achieving +15 % winter rainfall and ?39 % summer rainfall in rainfall-manipulated plots. Nitrogen (40 kg ha^?1 year^?1) was also added to half of the experimental plots in factorial combination. Plant species composition and above ground biomass were not affected by rainfall in the first 2 years and the plant community did not respond to nitrogen enrichment throughout the experiment. In the third year, above-ground plant biomass declined in rainfall-manipulated plots, driven by a decline in the abundances of grass species characteristic of moist soils. Declining plant biomass was also associated with changes to arthropod communities, with lower abundances of plant-feeding Auchenorrhyncha and carnivorous Araneae indicating multi-trophic responses to rainfall manipulation. Plant and arthropod community composition and plant biomass responses to rainfall manipulation were not modified by nitrogen enrichment, which was not expected, but may have resulted from prior nitrogen saturation and/or phosphorus limitation. Overall, our study demonstrates that climate change may in future influence plant productivity and induce multi-trophic responses in grasslands.     

Leaf litter of a dominant cushion plant shifts nitrogen mineralization to immobilization at high but not low temperature in an alpine meadow

Aims

We evaluated the effects of temperature and addition of leaf litter of Androsace tapete MaximWe–a dominant cushion plant species of alpine meadows on the Tibetan Plateau–on carbon (C) and nitrogen (N) mineralization, microbial biomass C (MBC) and N (MBN).

Methods

A laboratory incubation experiment with and without cushion plant litter addition was conducted for 112 days at three temperature regimes (?1, 5 and 11 °C). C and net N mineralization were simultaneously measured during the incubation period.

Results

C and N mineralization were affected by interactions between litter addition and temperature. Litter addition increased C mineralization and MBN but shifted N mineralization to immobilization at higher temperature. The positive relationship between net N mineralization and MBC and MBN was shifted to a negative one through cushion plant litter addition. Cushion plant litter also changed the relationship between C mineralization and net N mineralization from insignificantly positive to significantly negative.

Conclusions

These findings indicate that low temperature in winter could be important for alpine plants because low temperature can increase net N mineralization and supply plants with available N for their growth in the early growing season. During the growing season, climate warming–either directly through a temperature effect or indirectly through triggering increased cushion plant litter production–might lead to stronger competition for N between alpine plants and microorganisms.     

Seasonal abundance of soil-surface arthropods in relation to some meteorological and edaphic variables of the grassland and tree-planted areas in a tropical semi-arid savanna

Seasonality of relative population abundance in different groups of soil-surface arthropods was investigated monthly by pit-fall traps during a 2-year period in the grassland and tree-planted areas of a tropical semi-arid savanna at Warangal (south India). Densities of most groups were lowest during summer and highest during the rainy season. They were less abundant during winter. Arthropods were recorded in higher numbers in tree-planted compared to grassland areas. Certain arthropods that were found only during part of the year were recorded for a longer period in the tree-planted area. Formicidae,Monomorium indicum Forel,Crematogaster sp. andPachycondyla? tesserinoda (Emery), and Coleoptera,Pachycera sp. reached maximum densities in the rainy season and minimum numbers during winter and summer in the grassland area. However, these species had lower densities during the rainy season and reached maximum densities during winter and summer in the tree-planted area. The seasonal abundance of arthropods showed significant linear correlations with different abiotic environmental variables such as rainfall, soil moisture, organic matter, soil and air temperatures, soil pH, relative humidity at the soil surface, and potassium and phosphorus of surface soil. Soil moisture and rainfall were generally the strongest correlates with densities, particularly in the grassland area.     

Feral pigs as hosts for Amblyomma sculptum (Acari: Ixodidae) populations in the Pantanal,Mato Grosso do Sul,Brazil

The Pantanal in Brazil is the largest floodplain of the world. This ecosystem, rich in wildlife, has a large feral pig population. Such a large host biomass must have a strong influence on the parasite fauna. In this work, we evaluated the role of feral pigs in the maintenance of Amblyomma sculptum (formerly Amblyomma cajennense), the most prevalent tick species in the Pantanal. Tick infestations were evaluated on 243 feral pigs and their environment. The suitability of domestic pigs, representing their feral relatives, to A. sculptum adults and nymphs was assessed experimentally. Tick infestation of feral pigs was strongly associated with that of the environment: 96 and 97 % of the ticks, respectively, were A. sculptum. The infestation prevalence on this host species was close to 90 % in the dry season and 100 % in the wet season and mean infestation intensity was above 30 ticks in both seasons. Suitability of pigs as hosts for A. sculptum was shown by the high proportion of nymphs and female ticks found engorging on captured feral pigs and adequate biological parameters displayed by ticks from experimental infestations of domestic pigs. Other tick species on feral pigs, albeit in much lower numbers, were Amblyomma parvum and Ornithodorus rostratus. Results show that feral pigs feed a high proportion of the A. sculptum adults and nymphs in their territories and should be a target for tick-borne diseases studies. This is particularly relevant to public health because all the main tick species found on feral pigs are aggressive to humans as well.     

Plant communities of the Accra Plains,Ghana

A new classification, using the Zürich-Montpellier procedures, is presented for the grassland, thicket and forest vegetation of the Accra Plains, Ghana. Newly described syntaxa comprise 1 class (Vetiverietea), 4 orders, 9 alliances, 16 associations and 16 subassociations. Altogether 350 species of vascular plants were recorded in 140 relevés. Correlations are made between syntaxa and climatic, edaphic and anthropogenic factors. The floristic distinctness of the area is assessed: 4 endemic species and about 40 widely disjunct species occur. Although the majority of species are of Guinean affinity, the plant communities of the Accra Plains are unique in the context of African tropical vegetation.     

Microalgae Versus Land Crops as Feedstock for Biodiesel: Productivity,Quality, and Standard Compliance

Despite certain environmental advantages over fossil diesel, land crop-derived biodiesels may not satisfy the increasing worldwide demand for transportation fuels. As an abundant photosynthesizer, algae could be an adequate surrogate for biodiesel production. Nevertheless, high production costs, scarce selected species, and inaccurate assumptions about production yields represent industrial uncertainties. In this study, a reliable approach to analyzing algal biodiesel production has been developed based on species-to-species variations in oil productivity and quality. This approach compares biodiesels from Chlorophyta strains with land crop feedstock according to (i) potential yields, (ii) oil quality, and (iii) compliance with biodiesel quality standards. Algal yields were assessed by (i) extrapolating the strain-specific laboratory results to commercial-scale growth systems; (ii) converting volumetric to areal biomass productivity; and (iii) estimating oil yields for each strain, as the product of their projected areal biomass productivity for each growth system, and the oil percentage in biomass as determined in the laboratory. Biodiesel fuel properties were estimated by using fatty acid methyl ester profile predictive models. The Chlorophyta strains in this study provided annual oil yields that were generally higher than those of land crops by one order of magnitude. Six strains yielding more than 40 mg oil l^?1 day^?1 were identified as adequate for sustaining biodiesel production. Trebouxiophyceae algae were the most productive. Critical biodiesel parameters from both feedstock types suggest that most microalgae-derived biodiesels meet international fuel quality standards with better values than those of land crops. Because some of the highly productive feedstock does not simultaneously meet all the standards for a high quality biodiesel, optimization solutions are discussed.     

Comparative Analysis of the Fatty Acid Composition of Microalgae Obtained by Different Oil Extraction Methods and Direct Biomass Transesterification

One of the main challenges for the successful production and use of microalgae for biodiesel production is to obtain a satisfactory level of fatty acid methyl esters (FAME). The aims of this study are to identify the best method of lipid extraction and provide high FAME levels and to evaluate their fatty acid profiles. Six lipid extraction methodologies in three microalgae species were tested in comparison with the direct transesterification (DT) of microalgal biomass method. The choice of extraction method affected both the oily extract yield and the FAME composition of the microalgae and consequently may affect the properties of biodiesel. The efficiency of different lipid extraction methods is affected by the solvent polarity, which extracts different target compounds from lipid matrix. Dichloromethane/methanol extraction and Folch extraction produced the largest oil extract yields, but extraction with hexane/ethanol resulted in the best ester profile and levels. Performing DT reduces the volume of extractor solvent, the time and cost of FA composition analysis, as well as, presents less steps for fatty acid quantification. DT provided biomass FAME levels of 50.2, 636.4, and 258.2 mg.g^?1 in Nannochlorophisis oculata, Chaetoceros muelleri, and Chlorella sp., respectively. On the basis of an analysis of the fatty acids profiles of different species, C. muelleri is a promising microalga for biodiesel production. Depending on the extraction method, Chlorella sp. and N. oculata can be considered as an alternative in obtaining arachidonic (Aa) and eicosapentaenoic (EPA) acids.     

Genetic species delineation among branching Caribbean Porites corals

Coral species are difficult to discern because of their morphological plasticity, long generation times, and slow rates of mitochondrial DNA evolution. Among Caribbean representatives of the genus Porites are three named species (P. divaricata, P. furcata, and P. porites) with branching colony morphologies whose validity as genetically isolated species has been debated. We present sequence data from the mitochondrial control region, nuclear ITS, and nine single-copy nuclear loci for the Caribbean Porites and a related eastern Pacific species. mtDNA sequences were nearly invariant among the three branching species and their crustose sister P. branneri, and ITS sequences from these four were intermingled. An information theoretic analysis provided no support for upholding the three named Caribbean branching species. Both a clustering analysis and an analysis of molecular variance showed that sequence variation from the three branching forms is partitioned more by geography than by taxonomy. Multi-locus coalescent phylogenetic analysis provided a calibrated estimate for the nuclear DNA substitution rate (0.14 % Ma^?1) close to that for other corals. Because no generalities have emerged from genetic investigations of the validity of morphologically defined coral species, the use of single-copy nuclear data is likely to be important in testing problematic species designations.     

Coal mine drainage effects on a lotic ecosystem in Northwest Colorado,U.S.A.

An aquatic biological survey was conducted in 1979–1980 to determine the effects of drainage from an active coal strip-mine on Trout Creek, in northwest Colorado, U.S.A. Sampling was conducted over four seasons at four stations for periphyton, benthic invertebrates and fish. Periphyton in Trout Creek changed in the relative abundance of algae divisions in no apparent relation to mining. Diatoms were the predominant division at all sites. Golden-brown algae were abundant in spring at the stations upstream and adjacent to the mine. Blue-green algae were relatively important at stations upstream and downstream of the mine in winter. Benthic invertebrates exhibited a progressive increase in density, biomass and number of taxa from the upstream station to the downstream station. Shannon-Wiener diversity index for bethic invertebrates decreased slightly downstream of mine drainage but remained indicative of a clean water community. Aquatic insects (especially Trichoptera) were the predominant invertebrates at all stations. Analysis of functional groups of benthic invertebrates revealed increased importance of collector species at the lower sites while shredders were most important upstream of the mine. Unlike the invertebrates, fish exhibited slightly lower biomass at the station adjacent to the mine. The decrease was due to fewer salmonids. However, salmonid density and biomass increased substantially at the station just downstream of the mine. Non-game species (suckers and minnows) increased in numbers downstream and were most abundant at the lowest station. This coal strip-mine had little discernable adverse effects on the periphyton and invertebrates of Trout Creek. Fish populations did not appear to be significantly affected by the mine. Apparently, the presence of settling ponds and a buffer zone of unmined land between the mine and the stream helped to minimize adverse effects.     

Plant and animal communities in brackish supra-littoral pools (‘dobben’) in the northern part of the Netherlands

Fifty brackish supra-littoral pools bordering the Waddenzee were studied. The structure of plant communities (Potamogeton pectinatus L., Ranunculus baudotii Godr. and Zannichellia pedunculata Rchb.) is discussed in relation to water level fluctuations, chlorinity and water transparency. Chlorinity tolerances of the macrophytes (7 species) are discussed. The macrofauna was studied semi-quantitatively. The aquatic Coleoptera had the greatest diversity (24 species). A distinct relationship between the number of Coleoptera species and the percentage of macrophyte coverage was found. The distribution patterns of the most frequent species with respect to chlorinity categories are shown in histograms. The number of aquatic Heteroptera species is also discussed in relation to chlorinity and vegetation coverage. Less important macrofaunal groups (the Crustacea, Mollusca and Odonata) occurred in low species numbers.