Succession in a New Zealand alpine cushion community: a Markovian model

A permanent plot in a low-alpine cushion/tussock/shrub community was mapped at ca. decade intervals from 1953 to 1984. Transition probabilities between vegetation types were calculated, and a Markovian model was fitted.In spite of non-stationarity a Markov model was consistent with the observations, and produced reasonable predictions, especially for the major components of the vegetation. The model predictions were conservative in terms of future changes, in that future changes would be smaller than those observed, but such predictions could be supported by independent evidence, such as the nature of the non-stationarity, plant counts and seedling numbers.The general pattern was of a decrease in the cover of both Chionochloa rigida tussocks and mixed turf, and an increase in the cover of cushion bog species, especially Donatia novae-zelandiae. Shrubs, the suggested climax, showed no tendency to increase. Known climatic changes cannot explain the trend, which therefore seems to be a local retrogressive succession. There may be a cycle of alternating cushion and turf.     

Ongoing Fen–Bog Transition in a Boreal Aapa Mire Inferred from Repeated Field Sampling,Aerial Images,and Landsat Data

Ecosystems - Northern aapa mire complexes are characterized by patterned fens with flarks (wet fen surfaces) and bog zone margins with Sphagnum moss cover. Evidence exists of a recent increase in...     

Vegetation and environment of a New Zealand raised bog

Abstract. The vegetation of a mire in a medium‐high rainfall area of South Island, New Zealand is described. The central part of the bog is raised 6 m above the surroundings, suggesting that it is ombrotrophic, and the species present are those of apparently ombrotrophic bogs elsewhere in New Zealand. pH of < 4.0 and Ca/Mg molar quotient of < 1.0 also indicates ombrotrophic conditions. Within the mire, these criteria provide effective discrimination between the fen (rheotrophic) and bog (ombrotrophic) communities. A bimodal distribution of ordination scores suggests that the change in pH and in Ca/Mg quotients cause a switch to operate.     

The application of multivariate land classification to vegetation survey in the Wicklow Mountains,Ireland

Multivariate land classification and land cover mapping by aerial photographic interpretation were used to model spatial variation of land cover in the Wicklow Mountains, Ireland and to structure a stratified random sampling programme of upland blanket bog vegetation. The total area of blanket bog with gully-erosion features was estimated as 33% of the area studied. Vegetation with hand peat-cutting patterns was estimated at 5%, and there was 35% undissected (intact) vegetation. There were differences between land classes in the estimated area of land cover with gully-erosion features or hand peat-cutting patterns.Sample vegetation quadrats, stratified by land class and aerial photographic land cover type, were grouped by their plant species composition. The groups represented ombrotrophic mire, soligenous mire and shrub heath vegetation. There was significant association between vegetation group and land class, related to variation in regional landscape type, but no significant association between vegetation group and the aerial photographic land cover types, undissected (intact) and dissected (gullied and cut-over) peats. It is proposed that the similarity of vegetation between undissected and dissected blanket bog is related to vegetation regeneration. The need to consider differences in vegetation distribution, composition and dynamics in ecological management strategies is emphasised. The study demonstrated the value of stratified random field sampling for cost-efficient regional ecological assessment in upland blanket bog landscapes typified by the Wicklow mountains, Ireland.     

Little geographic or host plant genetic variation in a

The grass genus Chionochloa in New Zealand exhibits a high degree of mast seeding synchronised across species and habitats. Masting appears to be maintained by a predator satiation mechanism involving three pre-dispersal seed- and flower-feeding insects. It is not clear how important each of the three insects is in favouring the masting strategy. An undescribed cecidomyiid fly (Diptera: Cecidomyiidae) may be particularly important, since its conspicuous larvae are found throughout the South Island of New Zealand on many Chinochloa species. Despite the wide distribution of the larvae, it is not clear whether they are conspecific. Since the species is undescribed and adults are rarely seen, there may be different species on different host plants or in different geographic areas. We used Inter Simple Sequence Repeats (ISSRs) to determine whether cecidomyiid larvae found in four different areas in the South Island and on four species of Chionochloa exhibited molecular variation consistent with the presence of a single species of fly. Cluster analysis using Unweighted Pair-Group Method using Arithmetic averages (UPGMA) based on 38 ISSR fragments showed no clusters based on either host plant or geography. Analyis of Molecular Variance (AMOVA) analyses showed statistically significant differentiation among both host populations and geographic populations, but most of the molecular variation was explained by individual variation within geographic regions and host-plant populations. Thus, the molecular variation in the cecidomyiid larvae suggests the presence of a single species of cecidomyiid. Our data, combined with previous population surveys, suggest that the cecidomyiid is the most widespread of Chionochloa seed predators and may provide the selective benefit for the synchronous flowering observed among different Chionochloa populations in New Zealand.     

Successional processes induced by fires on the northern offshore islands of New Zealand

A modern pollen-vegetation data set of 46 samples is presented from subantarctic Campbell Island, 600 km south of the New Zealand mainland. The sampled vegetation includes all major community types: maritime turf and grassland, sedge flushes, dwarf forest, scrub, cushion bog, tussock grassland, and high altitude graminoid turfs and tundra. Macrophyllous forbs—characteristic plants of subantarctic islands—are common throughout. Most taxa have highly restricted pollen dispersal, largely due to the short stature of the vegetation and the high proportion of insect-pollinated species. Percentages of pollen or spores of the dominant taxa have a significant positive correlation with the percent vegetation cover of the corresponding species, the exceptions being the widespread ferns Polystichum vestitum and Blechnum spp., and the ubiquitous macrophyllous forb, Bulbinella rossii .The relationship between the vegetation cover of a given taxon and its pollen representation was usually not strong enough to give confidence in a quantitative reconstruction based on pollen frequency alone. However, the broad vegetation groupings have characteristic pollen and spore spectra clearly related to the abundance of their dominant plant species. Detrended correspondence analysis of the pollen spectra grouped most sites according to their source vegetation type and generated a pattern similar to that of vegetation data analysed in a similar fashion in previous studies of the island. This study, together with recent work on Auckland Island pollen and spore representation, has resulted in a combined modem palynological data base of more than 100 sites for the New Zealand subantarctic islands.     

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.     

Sphagnum divinum (sp. nov.) and S. medium Limpr. and their relationship to S. magellanicum Brid.

Sphagnum magellanicum has been viewed as being a predominantly circumpolar species in the northern hemisphere, but it occurs in the southern hemisphere and was originally described from the southern parts of Chile. It is an ecologically important species in mire ecosystems and has been extensively used as a model to study processes of growth, carbon sequestration and peat decomposition. Molecular and experimental studies have, however, revealed genetic structure within S. magellanicum, and morphological differences associated with these genetic groups. Here we describe Sphagnum divinum in Sphagnum subgenus Sphagnum (Sphagnaceae, Bryophyta) as a new species, based on molecular and morphological evidence. Sphagnum medium is reinstated as a distinct species and is epitypified. Consequently, a new species concept of S. magellanicum is presented including an epitypification. Important morphological characters to separate these three species in the field and under the microscope are presented. Ecology and distribution differ among the species; S. divinium has a wide habitat range including mire margin, forested peatlands and moist heaths, and a circumpolar distribution around the northern hemisphere. Sphagnum medium seems to be more restricted to ombrotrophic mire expanse habitats and shows an amphi-Atlantic distribution in the northern hemisphere. Sphagnum magellanicum has a very broad ecological niche in peatlands and is found in most mire habitats in Tierra del Fuego on the southern tip of South America.     

Patterns of variation in morphological characters and isoenzymes in populations of Sphagnum capillifolium (Ehrh.) Hedw. and S. rubellum Wils. from two bogs in southern Sweden

Abstract

Isoenzymatic and morphological data of four populations from two bogs in southern Sweden are presented. From each bog one population of Sphagnum rubellum was sampled from the mire expanse and one population of S. capillifolium from the mire margin. Data from isoenzyme-electrophoresis show that there is agenetic difference corresponding to the two morphological taxa. It is also indicated that they may hybridize. The fact that the taxa seem to be better separated at the continental Aggarps Mosse than at the suboceanic Traneröds Mosse would suggest that hybridization occurs more often in coastal than in inland climates.     

Field studies of nitrogen fixation of Australian alpine plants and soils

Alpine grassland areas in Victoria and New South Wales have been subjected to summer grazing by cattle and sheep for well over a hundred years. Legumes other than a few species of shrubs, which provide a very small percentage of the vegetation cover in the grasslands, are absent. Other alpine communities include Sphagnum ‘mossbeds’ in the valleys and areas of snowgum woodland and shrubland. Virtually nothing is known of the mineral status of these communities and nothing of their nitrogen economy. On the Bogong High Plains, enclosure of grassland and of Sphagnum mossbeds from grazing and trampling has resulted, in the last few decades, in considerable changes in both cover and composition of the vegetation. A portable gas chromatogram was used to carry out determinations of the capacity of samples of the grassland and Sphagnum to support acetylene reduction to ethylene, by convention equated to a capacity to fix nitrogen. There appears to be a substantial capacity for acetylene reduction associated with the rhizosphere of the grasses (Poa australis agg.). The capacity of the Sphagnum for acetylene reduction is even greater and appears to be due to facultative anaerobes, abundant only in the upper, living part of the Sphagnum. These organisms may depend in part on leakage of photosynthate from the living Sphagnum. Associations of Sphagnum with blue-green algae appear to be unusual in contrast with work on Swedish subarctic mosses, which is discussed. The only non-leguminous Australian alpine plant so far examined for nitrogen fixation is Podocarpus lawrencei. A capacity for acetylene reduction was found for neither the nodules of the roots of this plant nor the associated soils.     

Restoration of managed pine fens: effect on hydrology and vegetation

Question: How does restoration affect the hydrology and the understorey vegetation of managed pine fens? Location: Oligotrophic pine fens in Natura 2000 areas in Kainuu, eastern Finland. Methods: Eleven managed pine fens and eight pristine reference pine fens were chosen for the study in 2005. The managed fens, which had been drained for forestry during the 1970s and 1980s, were restored in 2007. The water table was monitored in all fens over four growing seasons during 2006 to 2009, and vegetation was surveyed from permanent sample plots in 2006 and 2009. Results: Before restoration in 2006, the water table was at a significantly lower level in the managed fens compared with the pristine fens. Immediately after restoration, the water table rose to the same level as in the pristine fens, and this change was permanent. Forest drainage had had little impact on the understorey vegetation of the managed fens in the three decades before restoration, with species typical of pristine fens still dominating the sites. Forest dwarf shrubs and feather mosses had started to increase in cover, but mire dwarf shrubs and Sphagnum mosses still dominated the managed fens. Only the typical hollow species Sphagnum majus, Sphagnum balticum and Scheuzeria palustris were missing from the managed fens. Two years after restoration, the changes in species composition were also marginal, with increased cover of mire dwarf shrubs and sedges being the only significant change. Conclusions: The success of restoration of oligotrophic pine fens seems likely, given that changes in hydrological functioning occurred rapidly, and since little change has occurred in the vegetation composition after draining. Speeding up the regeneration process in these peatland types by restoration may, therefore, be recommended, especially if the drainage effect extends to nearby pristine mires and influences their biodiversity.     

Chemical-Features of

Chionochloa species vary in the degree to which they are grazed by introduced ruminants. This is presumed to reflect the relative nutritive value and/or palatability of the forage provided by these indigenous grasses. Data are presented here on silicon content, in vitro organic matter digestibility (OMD), metabolisable energy (ME), crude protein and total nutrient mineral (TNM) contents of mature leaves of eleven Chionochloa species in southern New Zealand. Silification in all species is low, possibly as an evolutionary consequence of the absence of native mammalian herbivores in New Zealand. OMD determinations indicate a generally low nutritive value for these tussock grasses. Species characteristic of oligotrophic Peats (C. acicularis and C. crassiuscula ssp. torta) produced very low values (20-25%) but others (C. pallens ssp. cadens, C. macra and C. ovata) approached OMD levels of medium quality pasture (50-60%). Crude protein values are also in the poor to moderate range (4.13% in C. acicularis to 8.34% in C. ovata). The values for total nutrient mineral content largely parallel those for protein. The results are discussed in relation to the apparent relative palatability of each species in the field, and the vulnerability to grazing of some species with restricted distributions.     

Vegetation changes of a Danish mire 1957–1981

A Danish mire influenced by culture until ca. 100 years ago and since then with incipient growth of Betula pubescens , was analyzed in 1957 and 1981 with regard to height of the Betula trees and cover percentage of plant species in the field layer. In 1957, every m2 along a 110 m transect was examined; in 1981 only 56 m2 representatively selected from the transect were examined. Betula showed considerable changes with a net intake of 10 trees (23%) and a net loss of 23 trees (52%), i.e. a net loss of 13 trees (30%). The mean height of the trees has, however, increased by 80 cm and the sum of the height of the trees per m2 by 29 cm. An increased total cover was found for Em–petrum nigrum, Molinia coerulea , and Erica tetralix , and a decreased total cover for Calluna, Sphagnum magellanicum, S. nemoreum, S. rubellum, Hypnum cupressi–forme, Pleurozium schreberi , and Aulacomnium palustre. An almost unchanged total cover was found for Eriophorum vaginatum, E. angustifolium, Sphagnum recurvum, Andromeda polifolia, Drosera rotundifolia , and Oxycoccus palustris. On the basis of quantitative changes in the individual plots, a specific index of change is calculated, decreasing in the order Empetrum > Sphagnum magellanicum > S. recurvum = Molinia > Calluna > Hypnum cupressiforme > Pleurozium schreberi> Oxycoccus palustre> Sphagnum nemoreum = S. rubellum = Eriophorum vaginatum = E. angustifolium > Aulacomnium palustre > Erica> Drosera > Andromeda. Analyses from 1981 demonstrate that usually the light conditions and/or the water content and rarely the bulk density of the soil is correlated with the change in cover of the individual species. For some species it is also shown that the change is correlated with the strongly increased cover of Empetrum in particular. The changes are finally illustrated by showing the position of the species along ecological gradients in 1981.     

Fatal interactions between Scots pine and Sphagnum mosses in bog ecosystems

In this study, we explore how Sphagnum mosses and Scots pine, Pinus sylvestris , interact on different spatial and temporal scales in a boreal bog ecosystem. We were particularly interested in relationships between the occurrence of Sphagnum- dominated habitats and the occurrence of Scots pines of different age and size.
Juvenile and adult pines occurred in different habitats. While juveniles mainly occurred in Sphagnum- dominated habitats, predominantly with Sphagnum rubellum , adult pines were found in habitats dominated by lichens, or with a sparse vegetation cover. Examination of surface peat cores sampled close to adult pines revealed that almost all pines (97%) had established in a Sphagnum -dominated environment and that the habitat had changed since pine establishment. Scots pine is thus capable of changing and exterminating the Sphagnum -dominated environment preferred for germination and establishment. Pines impede Sphagnum growth and peat accumulation significantly once they have reached a stem diameter of approximately 20 mm. It takes from 30 to 90 yr for a pine to reach that size.
Our results show the importance of interactions between Scots pine and Sphagnum mosses in bog ecosystems. We conclude that interactions between trees and Sphagnum mosses are important driving forces behind the vegetation change that has characterised boreal bogs during the Holocene.     

Breeding habitat use and the future management of the critically endangered Southern Corroboree Frog

Summary   The Southern Corroboree Frog ( Pseudophryne corroboree ) is one of Australia's most critically endangered frog species. The species occurs entirely within Kosciuszko National Park, which has a history of cattle grazing (up to the 1970s). A consequence of cattle grazing has been a significant reduction in the extent of montane and sub-alpine peat-bog systems that the species uses as breeding habitat. Furthermore, climate change and associated increased wildfire frequency is expected to further reduce the extent and quality of peat bogs throughout the Australian Alps. In this study, we investigated habitat selection for breeding pools and nest sites within peat-bog systems in order to inform the conservation management of the species and guide other management practices being undertaken in peat bogs where this species occurs. Occupancy of breeding males at bog pools was found to be positively associated with increasing pool area, water depth and mid-day temperature, and negatively associated with extent of bare substrate. The majority of breeding pools identified were ephemeral. Nest sites within vegetation where males call and where females deposit their eggs were located at mid-elevations in a range of vegetation types, with the majority of nests being within moss and sedge dominated by Sphagnum cristatum and Empodisma minor . We also found that male nest sites were not randomly distributed within the edges of pools, but were more often located in areas of loose vegetation. These results highlight the potential sensitivity of the Southern Corroboree Frog to predicted changes in peat-bog systems resulting from climate change such as earlier drying and a possible reduction in the size of bog pools. A monitoring programme focused on key features of the breeding habitat should be undertaken to provide a basis for developing and assessing management actions implemented in peat bogs occupied by this species.     

Dynamics or constancy in Sphagnum dominated mire ecosystems? A 40‐year study

Traditionally mire ecosystems (especially bogs) have been viewed as stable systems with slow changes in the vegetation over time. In this study the mire Åkhultmyren, south‐central Sweden was re‐investigated in 1997 after 40 yr of continued natural development. The results show a high degree of dynamics in a Sphagnum dominated bog and fen. Altogether 97 vascular plant and bryophyte species were recorded in the two inventories of the bog and poor fen vegetation. pH and electrical conductivity in the mire water were also surveyed. In 1997 we found 10 new species and that 8 species had disappeared since 1954 but the over‐all mean number of species per plot (size 400 m²) had hardly changed. However, 21% of the species increased and 21% decreased significantly in frequency. Most of the species that decreased in frequency were low‐grown vascular plants, most common in wet microhabitats. Vascular plant species that increased in frequency included trees (defined as >1.3 m in height) and were generally taller than the unchanged or decreasing species. The frequency of dwarf shrubs and hummock bryophytes increased too. Areas with an initial pH of 4.5–5.0 showed the strongest decrease in pH, coinciding with an enlarged distribution of some Sphagnum species. The species diversity increased on the bog, but decreased in the wettest parts of the fen, where the pH also decreased. Species with unchanged or increasing frequency often showed high capacity to colonise new plots. On average the sum of gains and losses of species in the plots in 1997 was ca 50% of the species number in 1954. The vegetation changes indicate a drier mire surface and an increased availability of nitrogen. The increased tree cover may have triggered further changes in the plant cover.     

Interspecific and geographical differences of plant tissue nutrient concentrations along an environmental gradient in Southern Patagonia, Chile

Foliar nutrient concentrations of South Patagonian ombrotrophic peatland species were analyzed along a gradient of increasing continentality. We paid particular attention to nutrient demands of Sphagnum magellanicum, the dominant constituent of continental raised bogs, and to those of cushion-forming vascular plants such as Astelia pumila, dominating in western hyperoceanic blanket bogs. With exception of one graminoid species, nutrient concentrations in leaf tissues were generally low, but showed considerable variation. Extremely low concentrations were measured in S. magellanicum reflecting the unpolluted, pristine character of the investigated bog ecosystems. Nutrient concentrations in cushion plants showed remarkable variation. While nutrient concentrations in Donatia fascicularis were almost as low as in S. magellanicum, they were significantly higher in A. pumila. Variation in foliar nutrient concentrations was predominantly due to differences between species. Nevertheless, there was a significant shift within species along the considered west-to-east continental gradient. The stronger minerotrophic character of the western cushion bogs was reflected by higher Ca contents. N concentrations increased and P concentrations decreased westward in most species. Consequently, the most noticeable shift was an increasing N:P ratio indicating a higher degree of P limitation towards western cushion dominated blanket bogs.     

A phytoecological study of the mire Northern Kisselbergmosen, SE Norway. III. Diversity and habitat niche relationships

Alpha and beta diversity and habitat niche relationships of a poor, boreal mire was studied, based upon an ordination by detrended correspondence analysis and a subjective classification. The three first DCA axes were interpreted as variation along the following ecoclines: (1) mire expanse carpet–mire expanse hummock–mire margin hummock, (2) nutrient status: ombrotrophic–poor minerotrophic, and as a coenocline (3) associated with peat-producing ability of the vegetation with an unclear ecological basis. The autecology of the 39 most frequent species was decribed with respect to these gradients. Alpha diversity patterns varied considerably between coenoclines. Beta diversity was always higher in the bottom layer than in the field layer. Habitat niche breadth was strongly correlated with species abundance, and separable into a frequency-independent and a frequency-dependent component. The former decreased from vascular plants to hepatics, and further to Sphagnum spp. It was argued that the importance of interactions was high in the bottom layer, particularly among Sphagnum spp., but also among hepatics. Interactions among vascular plants was considered unimportant, except in hummocks. Plant strategies were discussed. The niche breadth approach was evaluated, and found fruitful, while niche overlap was considered to provide redundant information. The importance of each of (1) interspecific interactions, (2) destabilizing factors, (3) stress, and (4) chance, as structuring factors in boreal mires, is discussed. Boreal mires are considered to conform to the patch-dynamics theory of non-equilibrium coexistence.     

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.     

Succession changes in diversity and assemblages composition of planthoppers and leafhoppers in natural ancient peat bogs in Belarus

Succession has a strong influence on species diversity and composition of terrestrial ecosystems. Peat bogs are among them. They have a large area in Belarus compared to other Central European countries. While in several studies have analyzed the effects of succession on vegetation in peat bog ecosystems, the response of peatland insects to succession has not been investigated yet. To address this issue were sampled Auchenorrhyncha abundance and environmental parameters on the ancient and one of the largest natural peat bog along a successional gradient from the margin to the bog dome. The results provide evidence that succession of peat bogs has influence on planthoppers and leafhoppers abundance, diversity and species composition. Along the successional gradient from younger towards older successional stages an increase abundance of specialized peat bog species, chamebionts, oligophagous and monophagous was observed. On the contrary, the younger stages of natural peat bog succession offer favorable conditions to eurytopic, polyphagous and chortobiont planthoppers and leafhoppers. The highest abundance and species richness of Auchenorrhyncha were in the lagg zone followed by early stages of natural peat bog succession. The highest diversity was in the middle stages of succession. A determinant of Auchenorrhyncha diversity was the cover of ericaceous dwarf shrubs. Linear models shrub cover and number of plants species had a positive effect on planthoppers and leafhoppers diversity and a negative effect on their abundance. Amount of ericaceous dwarf shrubs within the peat bog could be as a measure of heterogeneity.