Poor-rich Gradient Research Articles

Gradients, Species Richness and Communities in Eastern Finnish Sloping Fens

In Scandinavia, three gradients (poor–rich, water table, margin–expanse) are considered in vegetation classification of mires. We re-analysed the data of Paavo Havas from 1961 on sloping fens in eastern Finland using NMDS ordination analysis, which also revealed a three-dimensional structure of the classic gradients, with the poor–rich gradient associated with pH. Water table level, and the unstable–stable water regime gradient were also of importance. Our analysis confirmed the interpretation by Havas but further stressed the role of the poor–rich gradient as the main direction of variation in sloping fens. Species richness increased with pH, and from mire expanse to margin vegetation, but decreased towards too wet or seasonally too dry conditions. Eastern Finnish sloping-fen plant communities resemble those in sloping fens elsewhere in Scandinavia, but also those in montane-subalpine-alpine fens in central and southeastern Europe.

Hydrology-driven environmental variability determines abiotic characteristics and Oribatida diversity patterns in a Sphagnum peatland system.

We investigated oribatid mite communities in a Sphagnum-dominated boreal peatland system characterised by a mosaic of oligotrophic and meso-eutrophic areas. We aimed to determine the relative importance of environmental factors (pH, Sphagnum nutrient content, water table level, diversity of vascular plants and bryophytes in the surrounding plant community) and spatial variation in influencing abundance, diversity and community composition of aquatic and terrestrial oribatid mites. Among environmental variables, water table level (micro-topography), pH, and K in Sphagnum tissues were the main predictors of Oribatida community structure. Aquatic species were associated with pools; two terrestrial species-Hoplophthiracarus illinoisensis and Nothrus pratensis-were associated with oligotrophic hummocks; the rest of terrestrial species were associated with dryer mesotrophic and eutrophic habitats. Low water table depth (hummocks), high local plant diversity, and high P in Sphagnum tissues were predictors of high abundance of terrestrial Oribatida. Species richness of terrestrial Oribatida was linked with low water table and high plant diversity. For aquatic Oribatida abundance, water table depth was the single most important predictor variable. Plot trophic class (its status on the peatland poor-rich gradient assigned based on plant indicator species) was also a significant predictor of terrestrial Oribatida abundance, richness, and community structure. Spatial structuring was important for terrestrial Oribatida community composition, weak (P < 0.10) for terrestrial Oribatida abundance and richness, and not significant for aquatic Oribatida.

BorealPicea abiesMires of Finland: Cajanderian Site Types and Compositional Gradients in Relation to Species Richness

We used classic sample plot data of Rauno Ruuhijarvi and Seppo Eurola from the early 1960s to compare Cajanderian site types of boreal Picea abies mires in Finland with a classification made with a multivariate method. Classic site types explained the compositional variation in the NMDS ordination better than the analysis, based on numerically derived clusters. Distinct compositional gradients were the poor—rich gradient and the peat thickness (paludification). Additionally, one could interpret a microtopographic gradient in the results. Our results, as well as some other studies support a view that climatic factors affect more than the bedrock the species richness in boreonemoral—boreal Picea abies mires of northern Europe. Soil chemical features (poor—rich gradient) and the microtopography modify the species richness at a site scale. Geographic speciesrichness centre of boreal-temperate Picea abies mires of Europe is unknown, but it is in relation at least to climate, to bedrock and to historical aspects.

Regional and Vegetation-Ecological Patterns in Northern Boreal Flark Fens of Finnish Lapland: Analysis from a Classic Material

We analysed and interpreted ecologically a part of classic peatland vegetation material of prof. Rauno Ruuhijarvi dating from 1960. Sample plots formed a compositional gradient along NMDS 1 across three traditionally recognized peatland subzones of Finnish Lapland, and Cajanderian site types showed a poor—rich gradient along NMDS 2. Analysis-based major vegetation groups were related to the regional and the mire-expanse-to-margin gradient. Southerly-focused Eriophorum gracile—Potentilla palustris—Straminergon stramineum major group was interpreted as an indication of a more voluminous spring flood in a more oceanic climate, while northerly-focused Carex rotundata—Trichophorum cespitosum m. g. was interpreted as a reflection of a minor spring flood in a more continental climate. Regional communities were compatible with Cajanderian site types and showed new regional and vegetation-ecological features for site types. They were related to three European fen alliances, which represented boreal (Stygio-Caricio...

Calcium intolerance of fen mosses: Physiological evidence, effects of nutrient availability and successional drivers

Species composition of peatlands is determined by the dominance of either Sphagnum or non-sphagnaceous (brown) mosses. Sphagnum species are more or less intolerant to alkaline waters rich in calcium bicarbonate, but the physiological background of this intolerance is poorly understood. Recently, sphagna have been widening their realized niches, expanding to alkaline brown-moss fens and altering their functioning. One possible reason is increased nutrient availability, but existing evidence is equivocal. We approached this problem by a series of laboratory experiments with 15 fen moss species cultivated submerged in solutions corresponding to natural poor- to rich-fen waters. We tested basic ecophysiological mechanisms of calcium tolerance (ion compartmentalization, cell-wall cation-binding properties, phosphorus and iron uptake), the breadth of fundamental pH/calcium niches for protonemata and adult plants, interspecific competition, and relationships between nutrient availability and pH/calcium tolerance. Our results suggest that calcium toxicity in calcifugous bryophytes is caused by insufficient control over the balance of intracellular Ca2+ uptake/efflux. Cell-wall cation-exchange sites of living mosses remain unsaturated with Ca2+ even in calcareous solutions, contradicting the proposed inhibitory effect of Ca2+-oversaturation on cell-wall expansion and monovalent cation uptake. Growth and biomass accumulation of brown mosses was highest in alkaline fen waters, but they could also survive and germinate in poor-fen waters. Calcium-tolerant sphagna survived along the entire poor–rich gradient, but their growth was inhibited by calcium bicarbonate. The three most obviously expanding sphagna produced protonemata even under calcareous conditions. Flowing but not stagnant alkaline fen waters were toxic for calcifugous sphagna, the strongest competitors in poor-fen waters. Increased potassium availability facilitated the survival of calcifugous sphagna in alkaline fens, corroborating field observations that potassium facilitates sphagnum expansion. Surprisingly, the rare and declining moss Hamatocaulis vernicosus was supported by nitrogen and phosphorus more than its competitors. Our comparison of fundamental and realized niches suggests that the dominance of particular moss functional groups in fens is governed by a competitive hierarchy altered by different calcium levels. The expansion of calcium-tolerant sphagna into brown-moss fens therefore requires perturbation that weakens competition. Additionally, expansion of calcifugous sphagna to alkaline environments may be stimulated by potassium availability.

Distribution patterns and environmental correlates of water mites (Hydrachnidia, Acari) in peatland microhabitats

In Europe peatlands are wetlands of postglacial origin. Because of climatic changes and agricultural activities (i.e. drainage and peat extraction), they are one of the most endangered ecosystems worldwide. Water mites are well known as indicators of changing environments in other ecosystems such as springs and lakes. For our study we selected seven peatlands located in North-Western Poland and focused on water mite distribution and associated habitat and water quality variables. We described water mite fauna in various microhabitats (aquatic and semiaquatic) along the mineral-richness gradient to test whether this gradient is reflected in the composition of water mite assemblages. We selected conductivity, pH and vegetation as variables reflecting the poor-rich gradient. Additionally, we measured water depth, temperature and dissolved oxygen, which are often important parameters for water mites. We also noted presence of prey and host taxa of particular water mite species. Based on physicochemical parameters we identified three types of habitats harbouring three distinctive species groups of water mites. We were able to distinguish species that appear to be typical of spring fens (e.g. Hygrobates norvegicus, Lebertia separata), connected with acidic, nutrient poor pools (e.g. Arrenurus neumani, A. pustulator) and species seemingly typical of temporary habitats dominated by Sphagnum mosses (e.g. Piersigia intermedia, Zschokkea oblonga, A. stecki). The poor-rich gradient is strongly reflected in the composition of water mite assemblages. We also found strong correlations between the water mite fauna and both conductivity and pH gradient. Our results show that water conductivity is the most important of the examined factors, driving mite-species distribution in peatlands.

Multiscale factors control community and species distribution in mountain peatlands

We studied the vegetation of 166 fens in Yellowstone National Park, USA, to determine the relationship between species distribution in mountain peatlands and regional-, landscape-, and local-scale environmental variables. Plant communities were identified through hierarchical agglomerative cluster analysis, patterns in species distribution were explored using nonmetric multidimensional scaling, and the relative importance of variables was assessed though partial canonical correspondence analysis. Five major bedrock types influenced groundwater feeding fens: three volcanic types, a glacial till complex, and rock altered by acidic geothermal activity. Ionic concentrations generally increased with pH, but acidic geothermal fens had very low pH and high electrical conductivity. Bryophyte distribution was controlled by groundwater chemistry, while vascular plants responded to a broader range of variables. When partitioned by spatial scale, landscape variables accounted for &gt;60% of the variation explained. When partitioned categorically, geochemical and topographic variables were more important than geographic factors. For fens in mountainous regions, the primary gradient is site-level water chemistry, which is strongly linked to regional bedrock geology. Site- and stand-level topography represent a secondary gradient. Most mountain fens fit within the established poor–rich gradient; however, geochemical acid production creates a distinct category outside the conventional paradigm.

Testate Amoeba (Arcellinida, Euglyphida) Ecology along a Poor‐Rich Gradient in Fens of Western Poland

AbstractWe investigated the relationships between testate amoebae (Arcellinida, Euglyphida), vegetation and water chemistry along environmental gradients in minerotrophic peatlands (fens) in western Poland. We hypothesized that: a) hydrochemistry significantly influences structure of testate amoeba communities, and b) testate amoeba communities are more closely correlated with the hydrochemical variables (environment) than with the vegetation data. Testate amoeba communities and vegetation from 71 sample plots were investigated together with the hydro‐chemistry and hydrology based on 16 environmental variables and vegetation composition. Testate amoeba communities revealed a distinctive poor‐rich gradient in analysed fens. Mineral‐rich habitats, which were dominated by brown mosses, were preferred by a higher number of taxa than acidic habitats, which were dominated by Sphagnum. We recorded a total of 107 testate amoebae taxa. The average species richness of testate amoebae for brown mosses was higher (20) than for Sphagnum (13). We found that testate amoebae communities were similarly correlated with vascular plants, mosses and environmental parameters. Results of direct ordination demonstrate that hydrology, pH, Mg2+ and sodium remain the most important environmental control for the entire data set. CCA showed that in case of brown mosses hydrology, sodium and oxygen affect testate amoeba communities significantly whereas in Sphagnum only sodium emerge as most significant determining testate amoeba assemblages. (© 2011 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Aboveground production and nutrient status of the vegetation of different mire types in the South-eastern Alps (Italy)

We determined aboveground net primary production (ANPP) in five mires in the South-eastern Alps of Italy. The mires differed considerably from each other with regard to pore-water chemistry, ranging from bog to rich fen. In different habitat types (hummock, scrub, lawn, fen meadow, hollow and marginal stream) within each mire type we assessed nutrient status based on measurements of nutrient concentrations and nutrient ratios in the plant biomass in order to test whether ANPP patterns along the poor-rich gradient could be related to the limiting effects of one or several nutrients for biomass production. Vegetation composition varied considerably both among mire sites and among habitat types in terms of individual species and plant functional types (PFTs). Nonetheless, mean ANPP was similar in the five mires. However, ANPP showed a positive correlation with total P concentration and negative correlations with the N:P ratio and with the K:P ratio of the vegetation. We conclude that plant biomass production is limited by P, rather than by other nutrients, across a broad range of mire types in this region.

Coastal heath vegetation in central Norway

This description of heath vegetation on the outermost coast of Trøndelag was based on 354 sample plots and 243 taxa. TWINSPAN, DCA and Ellenberg's indicator values were used to distinguish the vegetation types and to assess gradients in the vegetation. The aims were to make a phytosociological classification of the open coastal heath vegetation, find floristic gradients, compare the heath vegetation of central Norway with similar vegetation elsewhere and to evaluate the conservation values. The study area belongs to the southern boreal vegetation zone, and comparisons were made to Norwegian boreal and boreonemoral heaths, and to the sub‐montane heaths in the system of British plant communities. In the multivariate analyses, the data set was first separated on the poor–rich gradient. The four main units were separated by the second division of TWINSPAN and a further 16 communities were described. The poor heath communities had few vascular plants and a rather high number of bryophytes and lichens. The opposite was the situation in rich heaths. The studied heaths lack a number of typical species from further south in Europe, while some other species are common, that are absent or only occasionally occurring in coastal heath vegetation in nemoral and boreonemoral zones; e.g. Arctous alpinus, Arctostaphylos uva‐ursi, Betula nana, Chamaepericlymenum suecicum, Empetrum nigrum ssp. hermaphroditum, Rubus chamaemorus, Trientalis europaea, Vaccinium uliginosum, Carex nigra, Eriophorum angustifolium and E. vaginatum. A large number of western species occurs occasionally; Carex binervis is an exclusive, characteristic species for the heaths. In the European hierarchical phytosociological system, the communities were classified in five alliances: Erico–Sphagnion, Ericion tetralicis, Myrtillion boreale, Loiseleurio–Vaccinion and Kobresio–Dryadion. The rich heath types had the highest conservation value.

Vegetation-Environment Relationships in Peatlands Dominated by Sphagnum fallax in Western Poland

We investigated species composition and relative abundance of Sphagnum fallax dominated peatlands in relation to measured environmental variables on the basis of 26 sites in the Wielkopolska region. Most studied plots were characterized by soft waters, poor in Ca2+ but rich in nutrients, especially N-NH4 + and P-PO4 3-, with high electrolytic conductivity and high DOC (dissolved organic carbon) concentration. Six of the 19 measured variables of surface water chemistry (DOC, pH, SO4 2-, P-PO4 3-, Na+ and Ca2+) significantly explained 23% of the variation in floristic composition. In 65 vegetation plots, 107 species were observed. Cluster analysis revealed four types of vegetation in the studied mires. Sphagnum fallax was the most abundant species and formed plant communities in a wide range of habitats: in floating mats, with the plants usually adjoining the mineral basin edge (e.g. E. vaginatum, Andromeda polifolia and Ledum palustre) as well as it occupied central parts of Sphagnum lawn (e.g. Eriophorum angustifolium) and rich fen habitats (e.g. Carex rostrata or Phragmites australis). In Wielkopolska terrestrializating peatlands, four variables determine the poor-rich gradient: conductivity, DOC, SiO2 dissolved, Ca2+ and alkalinity. This study provides new data on the ecology and typology of Sphagnum peatlands in western Poland.

Fenomén prameništních slatinišť a malakologické konsekvence [The uniqueness of spring fens and malacological consequences

The objective of this paper is to (a) summarize the results of malacological investigations of the West Carpathian treeless spring fens and (b) show how unique sites these fens are. The mollusc communities were studied from several ecological points of view such as: response to the poor-rich mineral gradient, calcicole-calcifuge behaviour, geographical distribution, and historical development. The published or prepared articles concerning above-mentioned topics are cited in the text.

Fenomén prameništních slatinišť a malakologické konsekvence [The uniqueness of spring fens and malacological consequences

The objective of this paper is to (a) summarize the results of malacological investigations of the West Carpathian treeless spring fens and (b) show how unique sites these fens are. The mollusc communities were studied from several ecological points of view such as: response to the poor-rich mineral gradient, calcicole-calcifuge behaviour, geographical distribution, and historical development. The published or prepared articles concerning above-mentioned topics are cited in the text.

Water chemistry of mires in relation to the poor-rich vegetation gradient and contrasting geochemical zones of the north-eastern fennoscandian Shield

The relationship of the poor-rich vegetation gradient with water chemistry and geochemical bedrock zones was studied with a data set from 36 pristine mire sites in the middle boreal zone, Finland. The bipartition of bedrock zones into a granitoid zone and three other, more alkaline bedrock zones was clearly connected to the poor-rich gradient in the study area. Mires in the granitoid bedrock zone were predominantly bogs and poor fens, while most of the rich fen sites were located in other bedrock zones. In fens with strongly minerogenous hydrology, the geochemically distinct bedrock zones showed significant differences in concentrations of calcium, manganese, phosphorus, as well as in the total equivalent charge of base cations and the ratio of calcium and magnesium. In light of the indicator species baseda priori poor-rich classification anda posteriori correlations with vegetation ordinations and a poor-rich indicator cover index, pH showed the strongest relationship of the water chemical variables with the poor-rich gradient. High calcium concentrations only separated extremely rich fens from other categories. The poor-rich gradient of mires is considered as a primarily pH-related vegetation continuum. A more general use of pH-classes along with hydrological and vegetation based classification is suggested for mire classification instead of the “poor-rich” terminology.

The reliability of mire water pH measurements—A standard sampling protocol and implications to ecological theory

Abstract The frequency distributions of mire water pH are often bimodal in data sets covering the poor-rich gradient in vegetation. Area-representative data sets of pH could indicate ecologically meaningful differences between regions, independent of differences in mire classification. Comparisons of pH results are, however, hindered by differences in water sampling methods. We conducted a field survey to assess variation of water pH related to the poor-rich gradient, the water-table-depth gradient, time of day, aeration of samples, and different methods of obtaining water samples. Considerable diurnal and fine-scale vertical and horizontal variation of pH was found in samples obtained by depressing from bryophyte capitula or directly from open water surfaces. A diurnal pattern of lower pH at night and higher at day was found, typically with a 0.5–1.0 pH unit range. Open surface-water samples showed a wide range of fine-scale horizontal variation (pH 4.6–8.0) in Scorpidium-flarks, while pipe-well samples ...

Spring fen vegetation and water chemistry in the western carpathian flysch zone

In the western part of the Carpathian flysch zone, aquifers host several springwater chemistry types. Four vegetation types, distinguished along the poor-rich gradient (tufa-forming and peat forming brown moss fens, moderately rich and poorSphagnum fens), have been compared with respect to the main habitat factors. Water calcium and magnesium concentrations, pH and conductivity as well as the soil organic carbon content were the properties measured that showed the strongest correlation with the main vegetation gradient (the poor-rich gradient). Further, significant differences in iron, sodium, potassium, sulphate and phosphate concentrations were also found between pairs of related vegetation types. The range of calcium concentrations is wide (2–300 mg/l). The calcium concentration in tufa-forming springs is higher than values usually reported from northern and western Europe. Tufa formation is influenced not only by high calcium concentrations, but also by the total chemical composition of springwater and both climatic and topographic conditions. There is a great excess of cations over Cl− and SO 4 2− , balanced by HCO 3 − and CO 3 2− in springs with the most intense tufa precipitation. Unusually high calcium concentrations combined with high iron concentrations were found in peat-forming brown moss fens. RichSphagnum-fens with calcitolerantSphagnum species are distinctively low in phosphates. The Western Carpathian poor fens dominated bySphagnum flexuosum have water and soil calcium concentrations comparable to those reported from rich fens of some other areas. The springwater of these fens are rich in iron, phosphates and sulphates. The poorest spring fens withSphagnum fallax, S. magellanicum, S. papillosum andS. auriculatum are not only poor in calcium, but also in iron, sodium and potassium.

Recognition of peat-forming plant communities from their peat deposits in two south Swedish bog complexes

Peat samples, 3 015 from 103 boring points, on two mires (Akhult mire, Store Mosse mire) south Sweden, have been subjected to macrofossil analysis. Based on plant remains, 9 peat groups were distinguished in the field. A further classification using phytosociological methods revealed 29 peat types. The affinities between the peat types were determined from TABORD classification and a Reciprocal Averaging ordination. The primary floristic differentiation is correlated with a gradient from treeless-to wooded stands, which coincides largely with the mire expanse-mire margin gradient. The poor-rich gradient seems to parallel the treeless-wooded gradient as well and may reflect the natural conditions in this mire before it was affected by man. The hummock-mud-bottom gradient is easy to distinguish in peat, formed by bog communities, but is not distinct in peat formed by fen communities and impossible to detect in peat dominated by wood remains. The amount of identifiable remains depends on the decomposition, which is determined by (1) the period of time the plant litter stays in the acrotelm, and (2) the nutrient status. The decomposition is greatest in fen-peat with abundant wood remains. This probably depends on a good supply of oxygen caused by greater horizontal water movements and better nutrient status.