The effects of fertilization on part of the Keen of Hamar Serpentine,Shetland

Summary

Winter feeding of stock has caused eutrophication of the lower part of the Keen of Hamar. A nutrient addition experiment is reported which shows that grass cover of the serpentine debris increased greatly following phosphorus fertilization. Long-term observations have shown a substantial increase in grass cover over c. 35% of the lower part of the Keen and in one limited area the complete elimination of a rare species. It is suggested that the effects of eutrophication are likely to persist indefinitely and that it poses a major threat to this habitat and its rare plant species, although it seems that the site could be restored by removal of newly accumulated soil.     

Species turnover and diversity during early stages of vegetation recovery on the volcano Usu,northern Japan

To study the rate of revegetation during succession on the volcano Usu, northern Japan, vegetation structure and species composition were monitored from 1984 to 1988 in permanent quadrats near the summit of the volcano, which had been almost completely deforested by 1 to 3 m thick volcanic deposits in 1977–78. Analyses of vegetation structure included species richness, species diversity (IT), evenness (J'); year-to-year changes were quantified using Community Coefficient (CC), and Percentage Similarity (PS). While species turnover rates fluctuated and vegetation cover gradually increased, species richness, diversity and evenness did not fluctuate much. The diversity parameters showed slightly different levels for three habitat types distinguished. CC values comparing subsequent years with the starting year 1984 suggest only minor changes in qualitative species composition; PS values decreased more rapidly, indicating larger changes in species cover. A few well-rooted perennial plants were predominant, therefore, PS decline resulted from dominance-controlled community structure. PS-value detected not only habitat difference, but also the rate of the volcanic succession, suggesting that PS is most effective to evaluate successional pace.     

Vegetation patterns 25 years after the eruption of Mount St. Helens, Washington, USA

In 2004, we surveyed the vegetation on Mount St. Helens to document changes since 1992. We asked how communities differentiate and if they develop predictable relationships with local environments. We sought evidence from links between species and environment and changes in community structure in 271 250-m(2) plots. The habitats of the seven community types (CTs) overlapped broadly. Ordination methods demonstrated weak correlations among species distributions and location, elevation, and surface variables. Comparisons to 1992 by habitat demonstrated a large increase in plant cover and substantial development of vegetation structure. Pioneer species declined while mosses increased proportionately leading to more pronounced dominance hierarchies in most habitats. In Lupinus colonies, dominance declined, and diversity increased due to the increased abundance of formerly rare species. On once barren sites, dominance increased, but diversity changed slightly, which suggested the incipient development of competitive hierarchies. Weak correlations between vegetation and the environment suggested that initially stochastic establishment patterns had not yet been erased by deterministic factors. A vegetation mosaic that is loosely controlled by environmental factors may produce different successional trajectories that lead to alternative stable communities in similar habitats. This result has implications for restoration planning.     

Vegetation recovery patterns in early volcanic succession

Permanently plots were monitored from 1983 to the present on Mount Usu after the eruptions of 1977–78 which destroyed the pre-eruption vegetation by 1–3 m thick accumulations of ash and pumice in order to clarify the processes and mechanisms of succession. Until now, 163 species were recorded in the summit area. Most of these species were derived from vegetative reproduction throughout the volcanic deposits. Vegetative reproduction plays a major role on increases in cover. Although long-distance seed-dispersal species could immigrate to the crater basin, their cover increase was slow. Seedbank species only established in gullies where the original topsoil was exposed by erosion. Most annuais were supplied by the seedbank in the original topsoil and woody species originated via immigration, suggesting that the source greatly determines the species composition of establishing vegetation. Annual seedlings showed low survival, while overwintering perennial seedlings steadily established. Ground surface movements strongly restricted increases in plant cover and the distance from source vegetation was the principal determinant of plant density. Due to differences in disturbance intensity, successional rates were higher in the stable substrates outside gullies and lower on the exposed original topsoil in some gullies. Recipient of the Botanical Society Award of Young Scientists, 1994     

Abundance and seasonality of mid-altitude fellfield arthropods from Marion Island

Fellfield is an important habitat in both the Antarctic and sub-Antarctic. However, few studies have examined the abundance and seasonality of arthropods in sub-Antarctic fellfield habitats. Here, soil arthropod communities were sampled for over a full year in two distinct habitat components (rocky areas and Azorella selago cushions) in a mid-altitude fellfield on Marion Island. Species richness was relatively high (42 spp.) and consisted almost exclusively of indigenous species. Maximum mean annual density in the A. selago cushions was 16,000 individuals m⁻² for Eupodes minutus. In contrast, the highest density of any species in the rocky, inter-cushion areas was 700 individuals m⁻² for Halozetes fulvus. Quantitative analyses highlighted prominent differences in arthropod community structure between the two habitat components, despite the fact that most species were common to both of them. In general, arthropod abundances were lower in the fellfield compared with less extreme vegetation types in the sub-Antarctic, but were not dissimilar to those found in fellfield in the maritime Antarctic. In the Marion Island fellfield, arthropods either showed no pronounced seasonal peak in abundance, or a summer peak, although these patterns differed between habitat components within species, and between species. These data provide a firm quantitative foundation for further investigations of community patterns and seasonality in sub-Antarctic fellfield arthropods. Accepted: 10 June 2000     

Threatened vascular plant species in spontaneously revegetated post‐mining sites

The occurrence of threatened vascular plant species has been occasionally reported from some disturbed sites. Nevertheless, almost nothing is known about the conservation potential of post‐mining habitats for vascular plant species at a landscape scale. We asked how much threatened species occur in the artificial habitats, and if the participation of particular threatened species categories differ over the course of succession. We studied 10 successional series running in 321 post‐mining sites across the Czech Republic, Central Europe. In total, 2,597 vegetation samples comprising 935 vascular plant species were analyzed. We found 235 threatened species (14% of the country's threatened flora). The majority of the threatened plants, namely 223, avoided plots overgrown by woody species, in which only 48 species occurred. The importance of spontaneously revegetated habitats for nature conservation differed among successional stages formed by discontinuous vegetation cover (not fully developed and still open, up to approximately 25 years since site abandonment), which harbored especially critically endangered species of open habitats, and continuous vegetation cover (fully developed and closed, over approximately 25 years), which was suitable for specialized threatened species typical of fully established vegetation. A mosaic of various successional stages comprising both categories of vegetation cover should be applied as an effective restoration solution to maintain a variety of habitats for threatened species.     

Influence of late season fire on early successional vegetation of an Oklahoma prairie

Abstract. The study of vegetation dynamics in tallgrass prairie in response to fire has focused on dormant season fire in late successional prairies. Our objective was to determine if late season fire of varying frequency results in divergent successional patterns in an early successional tallgrass prairie disturbed by grazing and cultivation. Specifically, we evaluated the influence of late‐summer fires of varying frequency on community composition and species richness. We collected vegetation and environmental data on two sites burned in the late growing‐season at varying frequencies. These communities differed in composition depending primarily on edaphic factors, time since the last burn, and year‐to‐year variation. We interpret the time effect as related to changes in species composition accompanying plant succession that followed disturbance either from cropping and heavy grazing on the loamy site or heavy grazing on the shallow site. Other unidentified factors also have a role in vegetation dynamics on this prairie. Community composition and species richness were not consistently responsive to frequency of growing‐season fires.     

Canonical correspondence analysis of early volcanic succession on Mt Usu,Japan

Canonical correspondece analysis (CCA) was applied to explore revegetation patterns during early succession on Mt Usu. Vegetation was buried by deposits of ash and pumice from 1 to 3 m in depth from the 1977–78 eruptions. Three habitats were selected: tephra, tephra in gully and original surface. Plant density and plant cover data were analyzed separately. Environmental factors consisted of five quanticative variables (organic matter, elevation, distance from colonizing source, erosion and deposition of volcanic deposits) and three nominal variables (habitat types: tephra, tephra in gully and original surface). Canonical correspondence analysis showed that the original surface played a special role in vegetation development because the old topsoil supplied both nutrients and seed-bank species. The CCA also suggested that the environmental factors that influence plant density and cover differ. Distance from colonizing source affected plant density while erosion affected cover. Using CCA, factors could be distinguished that influenced seedling establishment from vegetation expansion and vegetation recovery dynamics could also be more clearly interpreted.     

A first step towards successful conservation: understanding local oviposition site selection of an imperiled butterfly, mardon skipper

Lack of basic biological information is a key limiting factor in conservation of at-risk butterflies. In the Puget prairies of Washington State little is known about the habitat requirements of mardon skipper (Polites mardon, federal candidate, WA endangered). We investigated oviposition site selection and used our results to assess oviposition habitat quality at a restored site with reintroduction potential. During the 2009 flight season we marked eighty-eight eggs and sampled vegetation at oviposition and random locations, measuring habitat variables with respect to the oviposition plant, vegetation structure, and vegetation cover. Eighty-six of the eighty-eight eggs were laid on Festuca roemeri, a native, perennial bunchgrass. Discriminant function analysis revealed selection of oviposition sites based on habitat structure; females laid eggs in small F. roemeri tufts in sparsely vegetated areas of the prairie. These results are contrary to results from a previous study in the Cascade Mountains of WA where females are generalists and selected densely vegetated areas, suggesting that the species has geographically specific habitat requirements. To assess oviposition habitat at a potential reintroduction site we measured the six variables most important for oviposition at the occupied site and a proposed reintroduction site. Results revealed differences in habitat quality between locations and suggest a need for further habitat management at the reintroduction site. Our results highlight the importance of understanding the local habitat use of a rare species where restoration activities occur and increase our ability to target habitat management where it is most needed for the persistence of the species.     

Is microclimate-driven turnover of dung beetle assemblage structure in regenerating coastal vegetation a precursor to re-establishment of a forest fauna?

We questioned the capability of post-mining rehabilitation and successional changes in coastal vegetation to achieve restoration of dune forest, dung beetle assemblages in the Maputaland Centre of Endemism, South Africa. A repeat 2010 study of structural turnover between dung beetle assemblages across a 33 year successional sere of rehabilitating vegetation and old-growth forest (>73 years) produced comparable results to an earlier study across the 23 year chronosequence of 2000. Despite overlap, three structural patterns along the 33 year chronosequence were associated with specific stages of vegetation succession and their characteristic microclimates as in 2000. Although species biased to unshaded habitat dominated the earliest succession, there was rapid re-establishment of dominance by shade-associated forest species. In concert with progression from unshaded, post-mining vegetation to strongly shaded, early successional, Acacia shrub-woodland, there was an initial increase in similarity of the dung beetle fauna (species-poor, low abundance) to that in strongly-shaded forest (also species-poor, low abundance). However, in concert with decreasing shade cover in late successional woodland, the dung beetle fauna became species-rich with high abundance so that the early successional trajectory of increasing similarity to forest fauna either levelled off to a plateau (species in 2000; abundance in 2010) or declined (species in 2010, abundance in 2000). It remains to be seen if gaps forming in the oldest Acacia woodland permit forest tree saplings of the exposed understorey to recreate a forest canopy that would be tracked by dung beetles to re-establish a typically species-poor, deep shade, forest assemblage with low abundance.     

Maintaining Critical Habitat in a Heavily Managed Landscape: Effects of Power Line Corridor Management on Karner Blue Butterfly (Lycaeides melissa samuelis) Habitat

The Karner blue butterfly (KBB) (Lycaeides melissa samuelis), a federally listed species, has historically been a component of barren and savannah ecosystems in the northeastern and midwestern United States. In New York, it now occurs primarily on managed, early‐successional sites such as power line corridors (utility rights‐of‐way) from Albany to Glens Falls. Blue lupine (Lupinus perennis), the exclusive larval food source of the KBB, has been suggested to be the most limiting factor for the butterfly within the eastern portion of its range. Power line corridor management maintains early‐successional habitats by suppressing the regrowth of woody species, creating potentially important habitat for the conservation and restoration of the KBB complex. This research compared the effects of several vegetation‐clearing methods on Blue lupine populations and associated communities of nectar species for KBB over an 8‐year period. Methods evaluated differed in intensity (annual, 4‐, or 8‐year intervals) and type (herbicide or mechanical). Blue lupine and plant community responses did not significantly differ among the treatment types applied to the power line corridors. However, Blue lupine cover, clump size, and density of stems per clump increased following the application of treatments in general. The number and cover of nectar species, total herbaceous cover, and species richness also responded positively to treatment overall. The percentage of non‐native species temporarily increased following treatment but declined to near pre‐treatment levels again as woody cover increased. Temporal changes in plant community composition were not related to management methods. The management tools assessed, mowing and herbicide application, will accomplish the goal of halting or reversing succession, maintaining critical habitat for the KBB in a landscape that provides little other suitable habitat.     

Restoring Sage‐grouse nesting habitat through removal of early successional conifer

Conifer woodlands have expanded into sagebrush (Artemisia spp.) ecosystems and degrade habitat for sagebrush obligate species such as the Greater Sage‐grouse (Centrocercus urophasianus). Conifer management is increasing despite a lack of empirical evidence assessing outcomes to grouse and their habitat. Although assessments of vegetation recovery after conifer removal are common, comparisons of successional trends with habitat guidelines or actual data on habitat used by sage‐grouse is lacking. We assessed impacts of conifer encroachment on vegetation characteristics known to be important for sage‐grouse nesting. Using a controlled repeated measures design, we then evaluated vegetation changes for 3 years after conifer removal. We compared these results to data from 356 local sage‐grouse nests, rangewide nesting habitat estimates, and published habitat guidelines. We measured negative effects of conifer cover on many characteristics important for sage‐grouse nesting habitat including percent cover of forbs, grasses, and shrubs, and species richness of forbs and shrubs. In untreated habitat, herbaceous vegetation cover was slightly below the cover at local nest sites, while shrub cover and sagebrush cover were well below cover at the nest sites. Following conifer removal, we measured increases in herbaceous vegetation, primarily grasses, and sagebrush height. Our results indicate that conifer abundance can decrease habitat suitability for nesting sage‐grouse. Additionally, conifer removal can improve habitat suitability for nesting sage‐grouse within 3 years, and trajectories indicate that the habitat may continue to improve in the near future.     

Staphylinidae and Carabidae overwintering in wheat and sown wildflower areas of different age

Species richness and abundance of staphylinid and carabid beetles overwintering in winter wheat fields and 1- to 3-year-old wildflower areas were investigated during 2000/2001 on 16 study sites in Switzerland. Abundance and species richness of overwintering staphylinids significantly increased with successional age of the wildflower areas and were always higher in older wildflower areas than in winter wheat. A similar but less distinct pattern was observed for the abundance and species richness of carabid beetles. The influence of habitat parameters (vegetation cover, fine sand content, organic matter, pH, soil pore volume, surrounding landscape structure, habitat area) on the staphylinid and carabid assemblages based on the number of individuals per species and site was analysed using canonical correspondence analysis. Vegetation cover was the most significant parameter significantly characterizing both staphylinid and carabid assemblages. The amount of vegetation cover explained 15.7% of the variance, fine sand content accounted for 13.3% and surrounding landscape structure for 10.9% of the variance in the staphylinid assemblage. In the carabid assemblage, vegetation cover was the only significant factor, explaining 24.7% of the variance. This study showed for the first time that the significance of wildflower areas as a reservoir for hibernation for generalist predatory beetles increases with progressing successional age.     

Relationships between plant diversity,vegetation cover,and site conditions: implications for grassland conservation in the Greater Caucasus

Overgrazing, land use abandonment and increasing recreational activities have altered the vegetation of high-montane and subalpine grassland of the Caucasus. The failure of previous restoration efforts with unsuitable and exotic plant species indicates the need for information on the present vegetation and in which way it might change. Within the Greater Caucasus, we have described and quantified the mountain grassland which develops under characteristic overgrazed and eroded site conditions. Further, we have proposed potential native plant species for revegetation to restore and conserve valuable mountain grassland habitats. We used non-metric dimensional scaling ordination and cluster comparison of functional plant groups to describe a gradient of grassland vegetation cover. For our study region, we identified four major vegetation types with increasing occurrence of ruderal pasture weeds and tall herb vegetation on abandoned hay meadows within the subalpine zone. Within high-montane grassland a decline of plant diversity can be observed on sites of reduced vegetation cover. Due to a low potential of the grassland ecosystem to balance further vegetation cover damage, the long-term loss of diverse habitats can be expected. We conclude with management recommendations to prevent erosion and habitat loss of precious mountain grasslands.     

Are habitat types compatible with floristically‐derived associations?

Abstract. The habitat type system developed by R. Daubenmire has been widely adopted throughout the western United States. Habitat types result from a site classification derived from the classification of late seral plant communities using selected indicator species. It has been suggested that the classification of late successional vegetation used to derive habitat types does not substantially differ from phytosociological classification in the sense of Braun‐Blanquet approach, and that habitat types can be adopted in their present form into floristically‐based vegetation classifications. Despite the many commonalities between the two systems, however, the classification methods, and specifically the use of indicator species in the habitat type system, yield a significantly different classification than the phytosociological approach. This is demonstrated in the comparison of a habitat type classification with the results of a recent phytosociological classification of forest vegetation in the northern Salish Mountains of Montana.     

Long-term effects of climate and phosphorus fertilisation on serpentine vegetation

The long-term effects of phosphorus fertilisation and climate on serpentine plant communities in Tuscany, central Italy have been investigated by using data from a 12 year before-after control-impact (BACI) experiment. Using the point quadrat method, data on plant communities were collected in June of each year from 1994 to 2005 in eight 2 × 2 m plots, four fertilised with phosphorus and four used as controls. Climatic data were obtained from a nearby meteorological station and summarised in 24 variables. Phosphorus addition significantly affected vegetation cover of both vascular and cryptogamic vegetation but did not influence species richness. The effects on species composition were clear but not marked, and consisted in promoting the abundance of some species already present in the community but not leading to the colonisation of other species. Interannual climate differences affected vegetation cover in the fertilised plots but not in the control ones, while climate affected the species richness values of different/various life-forms in both groups of plots, with more evident effects in the fertilised one. The effects of climate on plant community composition were weak once both the variability among individual plots and the successional dynamics were subtracted from the variance in species composition.     

Restoration of a Landfill Site in Berlin, Germany by Spontaneous and Directed Succession

We report on spontaneous and directed succession on a dry sandy landfill site of low fertility at Berlin‐Malchow, Germany. Changes in species composition and cover were followed on unmown and mown permanent plots of 2 × 2 m size through 5 years of vegetation development. Species richness on unmown plots was relatively constant during the time of observation, with 20 to 25 species per 4 m². Total cover of unmown plots continuously increased from approximately 10% in the first year to 80% in the fifth year. There are no clearly discernible sequential successional stages until present. The species composition includes species of all life forms, which colonized the site immediately after the initiation of the succession process representing the initial floristic composition type of vegetation development. However, perennial grasses and herbs gradually increased in cover up to approximately 40%. Woody plants were also present from the first year of succession and increased up to more than 20% cover in the fifth year, forming a shrub layer (>0.5 m) after the second year. Mowing significantly increased species richness, which was evident from the third year onward. This effect was mainly due to the reduction of the tall perennial grass Calamagrostis epigejos. Solidago canadensis and woody species were also significantly affected (lower cover and height), whereas short perennial herbs like Plantago lanceolata and Trifolium repens benefited from mowing.     

Effects of fire on the vegetation of a lowland heathland in North-western Italy

This study focuses on the effect of fire on lowland heathlands at the extreme southern edge of their European distribution (Vauda Nature Reserve, NW Italy). Forty-nine plots (50 m radius) were surveyed between 1999 and 2006. Each year, fire occurrences were recorded and per cent cover of four vegetation types (grassland, heath, low shrubland, and tall shrubland) was estimated in each plot. Vascular plant species richness was also recorded in 255, 1 m² quadrats. After a fire, grassland vegetation expanded, but then declined rapidly as heath and shrubland recovered: 7 years after a fire, tall shrubland encroached on to more than 40% of the plots, and grassland declined from 50% to 20% cover. Between 1999 and 2006, Betula pendula shrubland greatly expanded, while grassland decreased over most of the Reserve, even where fire frequency was high. Tall shrubland had low plant diversity and was dominated by widespread species of lower conservation value. By contrast, early successional vegetation (grassland and low shrubland) had higher richness and more narrowly distributed species, indication that the development of tall shrubland causes significant species loss in the heathland. Italian lowland heathlands are characterized by high rates of shrubland encroachment that threatens both habitat and species diversity. Burning frequencies of once in 3–6 years seem appropriate in this habitat, but burning alone might not suffice without actions to increase herbivore grazing.     

引入草木樨对半干旱黄土高原区早期植物群落演替和土壤养分的影响

植被演替早期的优势物种是影响演替进程的重要因素。以半干旱黄土高原地区退化耕地植被的自然恢复为对照,于植被恢复的早期引入两年生豆科植物草木樨(Melilotus officinalis L.),在种植密度为11.3kg.hm-2条件下,考察了6年内引入草木樨对退化耕地植被恢复过程中植物群落演替进程的影响。结果表明,与自然恢复植被相比,草木樨的引入不仅可以提高地表植被覆盖度和加速植物群落演替进程,促使一些群落演替后期物种如冷蒿(Artemisia frigida)、阿尔泰狗哇花(Heteropappus altaicus)和短花针茅(Stipa breviflora)等在植被恢复的第3年出现,同时有利于提高植被生产力和稳定性。同自然恢复相比,试验期间引入草木樨后的植被地上平均生物量提高67.90%。同时,植被恢复早期生物多样性与土壤全氮含量呈显著正相关,而草木樨的引入有利于提高土壤全氮含量;在植被恢复初期(2003～2005)引入草木樨的土壤全氮平均含量比自然恢复高7.32%;试验期间土壤速效磷含量与物种丰富度呈显著负相关。因此,在半干旱区黄土高原退化耕地植被恢复早期阶段,两年生豆科植物草木樨的引入和磷肥的施用对于加快植被恢复有着积极作用。     

Plant distribution and dispersal mechanisms at the Hassayampa River Preserve, Arizona, USA

This study focuses on the relationships between plant dispersal syndromes and plant distributions at the community scale. Species composition and cover are reported from 29 10 × 20-m vegetation plots along five topographic cross-sections in the riparian zone of the Hassayampa River Preserve, Arizona. We find that spatial patterns of dispersal guilds vary within the flood plain of this semiarid region river. Our main results are: (1) wind-dispersed species are fairly evenly distributed at all elevations and distances from the river, whereas cover of animal-dispersed species increases with elevation above, and at greater distances from, the river; (2) wind-dispersed species are proportionally more abundant in the pioneer Populus–Salix community, whereas plants in the late-seral Prosopis community are predominantly animal-dispersed; (3) most of the species classified as obligate-wetland and facultative-wetland are wind-dispersed, whereas facultative-upland and obligate-upland species are mostly animal-dispersed; and (4) there are significantly fewer wind-dispersed species in areas of high total vegetation cover. These results may reflect successional patterns resulting from periodic flooding. Low areas close to the river flood more frequently and with greater intensity than areas farther from the river. Many pioneer species that establish in disturbed areas are wind-dispersed. Over successional time, pioneer species cede to more drought tolerant species that are predominantly animal-dispersed.