Multiple gradients in mire vegetation: a comparison of a Swedish and an Italian bog

The major environmental gradients underlying plant species distribution were outlined in two climatically and bio-geographically contrasting mires: a Swedish bog in the boreo-nemoral zone, and an Italian bog in the south-eastern Alps. Data on mire morphology, surface hydrology, floristic composition, peat chemistry and pore-water chemistry were collected along transects from the mire margin (i.e., the outer portion of the mire in contact with the surrounding mineral soil) towards the mire expanse (i.e., the inner portion of the mire). The delimitation and the extent of the minerotrophic mire margin were related to the steepness of the lateral mire slope which, in turns, controls the direction of surface water flow. The mineral soil water limit was mirrored in geochemical variables such as pH, alkalinity, Ca²⁺, Mg²⁺, Al³⁺, Mn²⁺, and SiO₂ concentrations in pore-water, as well as Ca, Al, Fe, N and P contents in surface peat. Depending on regional requirements of plant species, different species were useful as fen limit indicators at the two sites. The main environmental factors affecting distribution of habitat types and plant species in the two mires were the acidity-alkalinity gradient, and the gradient in depth to the water table. The mire margin – mire expanse gradient corresponds to a complex gradient mainly reflected in a differentiation of vegetation structure in relation to the aeration of the peat substrate.     

Hydrology,groundwater chemistry and peat chemistry in relation to habitat conditions in a mire on the South – eastern Alps of Italy

The habitat conditions in a mire on the southern Alps of Italy were defined based on data on topography, hydrology, water chemistry, peat chemistry and floristic composition. Water flowed along the main longitudinal axis from the eastern dry sector to the western wet sector of the mire. Along the transverse axes the water table assumed a convex shape during dry periods, which resulted in water flowing towards the margins of the mire. During wet periods the water table assumed a concave shape, determining a flow of water from the margins towards the mire centre. The absence of any vertical groundwater flows enhanced habitat acidification, particularly in the eastern sector of the mire characterised by a smaller peat thickness. Surface water in the central portion of the mire had low calcium concentration and low electrical conductivity, comparable to those found in ombrotrophic bogs. Calcium concentration and electrical conductivity in surface water were higher along the margins, indicating a certain degree of mineral soil water inflow. Total contents of major nutrients (N, P and K) in the peat were rather homogeneous over the mire, while calcium concentrations were slightly higher in the peat layers of the wet portion of the mire. Species distribution was strongly influenced, rather than by surface water chemistry, by water table position and rate of surface water flow.     

Mire vegetation of the Muránska Planina Mts — formalised classification,ecology, main environmental gradient and influence of geographical position

Mire vegetation of the Muránska planina Mts and adjacent parts of neighbouring orographical units was studied in 1998–2005 using the standard Zürich-Montpellier (Braun-Blanquet) approach. We applied the defined phytosociological species groups and national formal definitions of mire associations in data processing. Within the classes Scheuchzerio-Caricetea fuscae and Oxycocco-Sphagnetea, seven associations (Caricetum davallianae, Carici flavae-Cratoneuretum filicini, Valeriano simplicifoliae-Caricetum flavae, Caricetum goodenowii, Carici echinatae-Sphagnetum, Carici rostratae-Sphagnetum and Pino mugo-Sphagnetum) were classified using formal classification criteria. Two other communities (Sphagno warnstorfii-Caricetum davallianae and Eriophoro vaginati-Sphagnetum recurvi) were not classified due to the lack of sufficient number of diagnostic species from species groups. The first DCA axis followed the mineral richness gradient. Vegetation plots were arranged from rich fens over moderately rich fens towards poor Sphagnum fens and raised bog. This fact was confirmed by a strong and significant correlation of the DCA site scores on the first axis with the measured pH and water conductivity as a surrogate of mineral richness. The second DCA axis correlated with mean Ellenberg’s indicator values for both temperature and soil nutrients. This pattern corresponds to that found in other regions of diversified Central-European landscape. We can therefore conclude that marginal geographical position and climatic specifity of the region under study did not alter gradient structure of the mire vegetation. When diversity of mire vegetation was compared to other regions in Slovakia by applying the same formal definitions to different regions, the study region was found to be conspicuously less diverse than the distribution centres of mire habitats in Slovakia (Orava and Vysoké Tatry regions), but more diverse than most of other marginal regions of mire distribution. Relatively high beta diversity of mires was probably caused by variable bedrock and local climate.     

Classification and ordination of the mire vegetation of Stormyra near Tynset, S Norway

The vegetation of Stormyra, a flat fen at Tynset, in Hedmark province, Southern Norway is classified by cluster analyses into seven different plant communities, all of a nonfixed hierarchical, low rank as follows:
(1) Scorpidium scorpioides comm., (2) Campylium stellatum - Drepanocladus revolvers comm., (3) Carex rostrata - Calliergon giganteum comm., (4) Sphagnum papillosum - S. subfulvum comm., (5) Homalothecium nitens - Sphagnum warnstorfii comm., (6) Pinus sylvestris - Sphagnum angustifolium comm. and (7) Empetrum hermaphroditum - Sphagnum fuscum comm.
A DCA-ordination showed that the samples were distributed mainly along a hummock - mud-bottom vegetational gradient, reflecting the local groundwater level. The range of the plant communities in terms of the traditional poor - rich and mire expanse - mire margin vegetational gradients is also dealt with. The vegetation and its relationship to such environmental factors as the ground-water level, and its seasonal fluctuations, the supply or absence of running surface water, the pH and electrical conductivity, are also discussed.     

Vegetation characteristics and eco-hydrological processes in a pristine mire in the Ob River valley (Western Siberia)

Relations between vegetation characteristics and eco-hydrological processes were assessed in a pristine mire in the valley of the Ob River (Western Siberia). Along a transect from the terrace scarp to the river, field data were collected on vegetation composition, peat stratigraphy, peat chemistry, hydrology and hydrochemistry. Based on floristic composition, eight vegetation communities were distinguished. Hydraulic head measurements were used to obtain an indication of groundwater flow directions. The water balance of the mire was calculated with a two-dimensional steady-state numerical groundwater model. Water types were defined based on cluster analysis of hydrochemical data. The results revealed that the dominant hydrological factor in the Ob mire is the discharge of groundwater, which supplies about threefold more water than net precipitation. Although the discharge flux decreases with increasing distance from the terrace scarp, high water levels and a “groundwater-like” mire water composition were observed in the major part of the study site. Precipitation and river water play only a minor role. Despite dilution of discharging groundwater with rainwater, spatial differences in pH and solute concentrations of the surficial mire water are small and not reflected in the vegetation composition. Although small amounts of silt and clay were found in the peat in the proximity of the river, indicating the occurrence of river floods in former times, no river-flood zone could be recognized based on hydrochemical characteristics or vegetation composition. A comparison of the Ob mire with well-studied and near-natural mires in the Biebrza River valley (Poland) revealed substantial differences in both vegetation characteristics and the intensity and spatial pattern of eco-hydrological processes. Differences in the origin and ratios of water fluxes as well as a dissimilar land use history would seem to be key factors explaining the differences observed.     

Effects of nutrient loadings from catchments on Asajino mire, a small coastal ombrotrophic mire in northernmost Japan

The relationship between water chemistry and vegetation was studied in a coastal ombrotrophic mire in northern Hokkaido, Japan. The distributions of Sphagnum and Phragmites communities were separated clearly by the pH and ion concentration of the peat surface-pore water. The drainage ditches along the road across the center of the mire had a high pH and ion concentration, as did the peat water in the western part of the mire. It was found that fields used for livestock farming on a hill to the west of the mire leached materials into the mire through drainage ditches, surface runoff, and probably also through ground water, and thus influenced the water chemistry of the mire. Management of the water, including that in the catchment of the mire, should be introduced before biological buffering capacity against excess nutrient loading caused by human activity is exceeded and the mire loses its ombrotrophic status.     

South Patagonian ombrotrophic bog vegetation reflects biogeochemical gradients at the landscape level

Question: Which environmental variables affect the floristic composition of south Patagonian bog vegetation along a gradient of climate and biogeochemical changes with increasing distance from the Pacific ocean? Location: Trans‐Andean transect (53° S), southern Patagonia Material and Methods: Floristic composition, peat characteristics (water level, decomposition, pH, total nitrogen, total carbon, ash content and plant available P, K, Na, Ca, Mg, Fe, Mn, Zn, and Al) and climatic constraints of ombrotrophic peat‐lands were measured at 82 plots along a gradient of increasing distance from the Pacific Ocean. Results: Climatic constraints and biogeochemical peat characteristics significantly change with increasing distance from the Pacific. Peatland vegetation shifted from hyperoceanic blanket bogs dominated by cushion forming vascular plants to the west to Sphagnum bogs to the east. Climatic and biogeochemical variables explained a large proportion of the floristic variation along the first DCA axis. The second axis represented a water level gradient. When ‘distance to the Pacific’ was defined as a covariable in partial CCA, the proportion of variance explained declined for most other variables, especially in the case of annual precipitation and exchangeable base cations and related traits. The differences in biogeochemical characteristics related to peat were mainly attributed to the input of sea‐borne cations. Conclusions: While variation in vegetation composition along a longitudinal gradient crossing the southern Andes was attributed to climatic constraints as expected, vegetation composition was also strongly affected by the biogeochemical characteristics of peat. Sea spray was of high ecological importance to peat chemistry and, consequently, to floristic composition. Presumably, south Patagonian peat bogs represent a glimpse of pre‐industrial environments, so that these peat bogs may act as reference systems with respect to atmospheric inputs in mire ecology research.     

Ecological processes and trophic status of two low-alpine patterned mires,south-central South Island,New Zealand

Abstract Vegetation and environmental patterns, and associated ecological processes, were quantified from 42 sites on several transects in each of two extensive (5 and 220 ha) low-alpine patterned mires in the same region of south-central New Zealand. Plant communities, as derived from multivariate analyses, were correlated with 15 physical and chemical environmental factors. Various measures of water availability and chemistry were consistently the most significant factors in relation to vegetation patterns in both mires. In the smaller mire, plant cover adjacent to pools, which were partly or completely drained through underground tunnels, dominated the overall correlations. The nutrient status of surface water had a consistent negative relationship with water availability. No consistent spatial or temporal patterns were found in the concentrations of Ca, Mg, K or Na, nor pH or conductivity in pool water. Evaporative enrichment of cations on the surface of both mires was noted, with levels consistently higher in surface than in adjacent pool water. The somewhat higher nutrient status in the smaller mire may be a result of the size and/or the amounts of run-off from the surrounding slopes onto the mire surface or through the underground pipe system. Hydrogen (D) and oxygen (¹⁸O) isotopic compositions in water from pools, the mire surface and below ground from the smaller mire, suggested that there was negligible mixing of evaporation-enriched surface water with groundwater. Differences in overall nutrient levels in the two mires were relatively small and indicative of mesotrophic or marginally ombrotrophic status for these mires. Although of international significance, the wetland complex currently has inadequate formal protection. Possible options are assessed.     

Base mineral inflow in a remnant cool-temperate mire ecosystem

Kiushitou (42°28N, 141°9E) is a lowland mire located in a residential area of northern Japan. We examined the 2-D distribution of hydrochemical variables and their seasonal changes in relation to plant communities in an attempt to conserve the Sphagnum fen (Sphagnum subfulvum). This mire is gently sloping and the upper area consists of alder and ash forests, while the lower area is covered with fen communities. The grassy fen, Moliniopsis japonica, occurs throughout the lower area, whereas the Sphagnum fen is restricted to the southwest part of the mire. anova and canonical correspondence analysis revealed that the occurrence of Sphagnum fen is negatively correlated with Mg, Ca and electrical conductivity (EC). These variables indicated that water in the upper forest area contained a high concentration of minerals from the neighboring residential area. Seasonal changes in EC values revealed that the watercourse from a spring point in an upper corner to the lowest drainage ditch was divided into two, southwest and northeast, courses. Because the northeast-course spring water joins mineral-rich water flowing from a point at the upper margin, the northeast part of the lower area contains considerable Ca and Mg. In contrast, the mineral-poor spring water flowing into the southwest part of the mire ensures the survival of the Sphagnum fen. Thus, when we stop the supply of mineral-rich water from the upper margin the area of the Sphagnum fen will expand into the northeast part of the mire. Two-dimensional details of the hydrochemical regime clarify the impact of mineral inflow and the expansion mechanisms of these minerals.     

Availability of dissolved oxygen in interstitial waters of a sandy creek

Dissolved oxygen, pH, conductivity and alkalinity of surface and subsurface interstitial waters were investigated at Mill Creek (a small, rural, predominantly sandy stream in east Texas).Dissolved oxygen concentration tended to decrease with sediment depth, while conductivity and alkalinity did not significantly change with substrate depth. Surface water pH was significantly higher than interstitial water (p = 0.05).Chemical analyses of subsurface water from a pre- to post-storm event showed a depression in dissolved oxygen concentration in moderate and deep interstitial waters, immediately following the return of stream base flow, with the deeper strata returning to pre-storm oxygen levels four days later.A thermal convective current mechanism is proposed which would serve to transport surface water downward into these deeper interstices.     

Shifts in the ecological behaviour of plant species between two distant regions: evidence from the base richness gradient in mires

Aim Water pH and conductivity are known to be major environmental factors controlling the species composition of nutrient‐poor wetlands. Based on the analysis of two large data sets of species co‐occurrence, sampled along the entire pH/calcium gradient, we explored whether species exhibit similar or different ecological behaviour in the two regions. Location West Carpathians (central Europe) and Bulgaria (south‐eastern Europe), situated 800 km apart. Bulgaria represents a range margin for many mire species. Methods The probability of occurrence of the 41 most common species along the pH and conductivity gradients was assessed using logistic regression fitted by means of generalized additive models. The species optimum and amplitude were determined. To check the possible effect of competitive release, we estimated where the potential maximum number of species (maximum overlap in realized niches) occurs along the base richness gradient. Results Most of the 41 frequently occurring species showed a significant response to water pH and ln‐transformed conductivity (approximating total mineral richness) in both regions. Eight species showed a shift in pH optimum greater than one unit, while 12 species showed the same or a larger shift along the conductivity gradient. Nearly all these striking shifts were connected to an extension of species tolerance towards mineral‐poor acid habitats in Bulgaria, which causes links between species and measured factors to be conspicuously weaker in Bulgaria than in the West Carpathians. Regarding ecological amplitude, 24 species exhibited a wider tolerance to water conductivity in the West Carpathians, whereas 17 species exhibited a wider tolerance in Bulgaria. Main conclusions A distinctive variation in the realized niche was observed in a large portion of the species examined. Niche shifts between local populations of the same species were similar to those of closely related vicariant species. Ecotypic adaptation within species is a possible explanation for this pattern. Other possible explanations (competitive release, specific habitat conditions, compensation for climate) seem to be less justified. The local populations of rich‐fen species may have adapted to mineral‐poor acid conditions in the high crystalline mountains of Bulgaria during dry periods of pleniglacials. Nomenclature Marhold & Hindák (1998) ; for Balkan elements not included in this source, Andreev et al. (1992) .     

Contrasting Species—Environment Relationships in Communities of Testate Amoebae, Bryophytes and Vascular Plants Along the Fen–Bog Gradient

We studied the vegetation, testate amoebae and abiotic variables (depth of the water table, pH, electrical conductivity, Ca and Mg concentrations of water extracted from mosses) along the bog to extremely rich fen gradient in sub-alpine peatlands of the Upper Engadine (Swiss Alps). Testate amoeba diversity was correlated to that of mosses but not of vascular plants. Diversity peaked in rich fen for testate amoebae and in extremely rich fen for mosses, while for testate amoebae and mosses it was lowest in bog but for vascular plants in extremely rich fen. Multiple factor and redundancy analyses (RDA) revealed a stronger correlation of testate amoebae than of vegetation to water table and hydrochemical variables and relatively strong correlation between testate amoeba and moss community data. In RDA, hydrochemical variables explained a higher proportion of the testate amoeba and moss data than water table depth. Abiotic variables explained a higher percentage of the species data for testate amoebae (30.3% or 19.5% for binary data) than for mosses (13.4%) and vascular plants (10%). These results show that (1) vascular plant, moss and testate amoeba communities respond differently to ecological gradients in peatlands and (2) testate amoebae are more strongly related than vascular plants to the abiotic factors at the mire surface. These differences are related to vertical trophic gradients and associated niche differentiation.     

Drainage ditching at the catchment scale affects water quality and macrophyte occurrence in Swedish lakes

1. We have limited knowledge of the effects of land use in general and of drainage ditching in particular on macrophyte communities in lakes. I quantified catchment land use, including drainage ditching, as well as water quality and the number of macrophyte species in 17 Swedish lakes in summer 2005. 2. Land use within 1 km of the studied lakes was analysed in a geographic information system. The following variables were included: areas of forests, mires, agricultural land and urbanization, length of drainage ditches (classified according to the use of the land they drained), and shortest distance from lake to an urban area. To extract and analyse general trends in the data sets, redundancy analysis was used. 3. Water quality was explained mainly by three land‐use related variables: the lengths of agricultural, forest and mire ditches. The length of agricultural ditches was positively correlated with lake water conductivity, total dissolved solids, Ca, N and total organic carbon (TOC). The lengths of forest and mire ditches were positively correlated with lake water characteristics, especially TOC. 4. The number of species representing different macrophyte life forms was explained by three environmental variables: conductivity, and lengths of forest and agricultural ditches. The numbers of isoetids, nymphaeids, elodeids and total obligate hydrophytes were negatively correlated with length of forest ditches. In contrast, the number of lemnids and helophytes was positively correlated with conductivity and length of agricultural ditches. Furthermore, the number of isoetids was exponentially related (negatively) to lengths of agricultural and forest ditches, indicating a threshold response to drainage ditch length. 5. The results suggest that effects on water quality and macrophyte communities result from drainage ditching in the lake catchments rather than from land use itself. Given the total area of drainage‐ditched land worldwide (millions of ha in Scandinavia alone), drainage ditching should be considered when evaluating environmental impacts on lake water quality and macrophyte occurrence and when determining reference conditions for catchment land use.     

Ionic and nucleotide requirements for microtubule polymerization in vitro.

The ionic and nucleotide requirements for the in vitro polymerization of microtubules from purified brain tubulin have been characterized by viscometry. Protein was purified by successive cycles of a temperature dependent assembly-diassembly scheme. Maximal polymerization occurred at a concentration of 0.1 M Pipes (piperazine-N,N'-bis(2-ethanesulfonic acid)); increasing ionic strength by addition of NaCl to samples prepared in lower buffer concentrations did not result in an equivalent level of polymerization. Both Na-+ and K-+ inhibited microtubule formation at levels greater than 240 mM, withmaximal assembly occurring at physiological concentrations of 150 mM. Maximal extent of assembly occurred at pH 6.8 and optimal rate at pH 6.6. Inhibition of polymerization was half-maximal at added calcium concentrations of 1.0 mM and magnesium concentrations of 10.0 mM. EGTA (ethylene glycol bis(beta-aminoethyl ether)tetraacetic acid), which chelates Ca-2+, had no effect on polymerization over a concentration range of 0.01-10.0 mM. In contrast, EDTA (ethylenediaminetetraacetic acid), which chelates both Mg-2+ and Ca-2+, inhibited assemble half-maximally at 0.25 mM and totally at 2.0 mM. As determined from experiments using Mg-2+-EDTA buffers, magnesium was required for polymerization. Magnesium promoted the maximal extent of assembly at substoichiometric levels relative to tubulin, but was maximal for both rate and extent at stoichiometric concentrations. Elemental analyses indicated that approximately 1 mol of magnesium was tightly bound/mol of tubulin dimer. Viscosity development was dependent upon hydrolyzable nucleoside triphosphate, and stoichiometric levels of GTP were sufficient for maximal polymerization. The effect of magnesium in increasing the rate of GTP-dependent polymerization suggests that a Mg-2+-GTP complex is the substrate required for a step in assembly.     

若尔盖高原沼泽湿地N2O排放通量研究

应用静态箱/气相色谱法,测定了若尔盖高原沼泽N₂O排放能量,测定期为该地植物生长期,即2004年4月末至10月初。结果表明,若尔盖高原沼泽湿地N₂O排放通量平均值为0.010mg·m^-2h^-1,最大值为0.079mg·m^-2h^-1,最小值为-0.051mg·m^-2h^-1。高峰排放期为5月,最低排放期为地表水深最大的6月。沼泽湿地N₂O排放通量季节变化与沼泽湿地水深呈负相关关系。沼泽湿地N₂O排放通量日变化与大气温度呈正相关关系,排放高值出现在午后。若尔盖高原沼泽湿地在植物生长期的年排放总量约为0.159Gg·a^-1。     

Responses of Epilithic Diatom Communities to Environmental Gradients in Some Finnish Rivers

Responses of the epilithic diatom communities to environmental gradients were analysed at 135 river stations in Finland. In addition, the biological quality of the water was evaluated using diatoms in five rivers having different types of human pressures. According to CCA, conductivity, total P, pH and humus content had the most significant effect on the diatom community structure. The ratio of the constrained axis (λ₁) and first unconstrained axis (λ₂) was highest for conductivity (1.21), total P (0.83) and pH (0.67). Physical factors had somewhat weaker effects. Five different diatom community types were separated in chemically different rivers using ordination. The effects of purified sewage on diatom‐inferred water quality estimates were strongest in late summer. The effects of cattle‐farming and cultivation were difficult to separate.     

Formal definitions of Slovakian mire plant associations and their application in regional research

We applied the Cocktail method to a large data set of 4 117 relevés of all Slovak vegetation types with the aim to create formalised definitions of all Slovakian mire plant associations. We defined 21 groups of species with the statistical tendency of joint occurrences in vegetation. These groups differed substantially in their position along the pH/calcium gradient. We further defined 24 plant associations according to presence and/or absence of certain groups and/or strong dominance of some species. Only six traditional plant associations were not possible to be reproduced this way. We applied our formalised definitions to the regional data set of mires from the surrounding of the Vysoké Tatry Mts. Combined with frequency-positive fidelity index this method has led to the classification of the majority of vegetation plots into ten associations. When the vegetation types obtained from Cocktail-based classification and from cluster analysis were compared with respect to measured pH and conductivity in the study region, 82% of pairs differed significantly either in pH or in water conductivity in the former classification and 69% in the latter one.     

A phytoecological study of the mire Northern Kisselbergmosen, SE Norway. II. Identification of gradients by detrended (canonical) correspondence analysis

The vegetation of a poor mire is sampled by two procedures; 800 randomly placed sample plots made up the R data set, 765 subjectively selected plots in 153 sample plot series made up the S data set. DCA ordination and constrained ordination by DCCA of the data sets and subsets showed the existence of three coenoclines in the material: (1) the coenocline along the mire expanse: low to high median depth to the water table—mire margin gradient, (2) the poor-rich coenocline, dependent on a complex-gradient in substrate chemistry, and (3) a coenocline attributed to variation in peat productivity. Thus the assumption of Fennoscandian mire scientists embedded in numerous systems for classifying mire vegetation, that three gradients are the most important in the mire ecosystem, is partly confirmed. In the investigated area, two of the gradients normally considered make up one complex coenocline (1), and a fourth coenocline (3) has to be added. The effects of sampling techniques on correlations between coenoclines and on ordination results are discussed, and an improved sampling technique is suggested. The major faults of DCA: (1) the tongue effect, and (2) the instability, are described and discussed. It is concluded that if due attention is taken to reveal effects of the faults of the method, DCA is among the best ordination methods currently available.     

A novel indicator of reducing conditions and water-table depth in mires

1. Direct measurements of water-table depth in a mire were compared with depth to discolouration of polyvinyl chloride (PVC) tape left in situ for 15 months. Discolouration depth was highly correlated with positions of highest and lowest water tables; estimates were systematically biased but generally within 5 cm of measured values.
2. The annual range in water-table position indicated by discolouration depth varied 10-fold along a 30 m transect. Discolouration of PVC tape is an indicator of reducing conditions that could be applied in extensive surveys at very low cost.