Primary Succession

Background: Herbivory is an important top-down force on coral reefs that regulates macroalgal abundance, mediates competitive interactions between macroalgae and corals, and provides resilience following disturbances such as hurricanes and coral bleaching. However, reductions in herbivore diversity and abundance via disease or over-fishing may harm corals directly and may indirectly increase coral susceptibility to other disturbances.

Ð In contrast to conventional social insurance, the New Zealand retirement income system comprises a basic individual taxable¯at-rate public pension supplemented by purely voluntary saving. The New Zealand system has proved remarkably durable, acceptable, and ®scally responsible. It does not conform to the World Bank's ideal of three pillars, but oers developing and mature countries a model that is worthy of careful examination. Its primary success lies in ensuring a stable and adequate retirement income for all citizens, moderating income inequality in retirement and protecting all older citizens from uncertainty in times of rapid economic and social change. Ó

Landslides are excellent illustrations of the dynamic interplay of disturbance and succession. Restoration is difficult on landslide surfaces because of the high degree of spatial and temporal heterogeneity in soil stability and fertility. Principles derived from more than a century of study of ecological succession can guide efforts to reduce chronic surface soil erosion and restore both biodiversity and ecosystem function. Promotion of the recovery of selfsustaining communities on landslides is feasible by stabilization with native ground cover, applications of nutrient amendments, facilitation of dispersal to overcome establishment bottlenecks, emphasis on functionally redundant species and promotion of connectivity with the adjacent landscape. Arrested succession through resource dominance by a single species can be beneficial if that species also reduces persistent erosion, yet the tradeoff is often reduced biodiversity. Restoration efforts can be streamlined by using techniques that promote successional processes.

In dry Mediterranean environments, the epiphytic habitats are generally poor in bryophytes. However, Sierra Alhamilla, a mountain embedded in one of the driest areas in Europe, is an exception. It shelters an evergreen oak wood, whose richness in epiphyte bryophytes is similar to or higher than that of humid mountain ranges from the Iberian Peninsula and North Africa. The genus Orthotrichum , besides dominating the epiphyte communities on tree trunks and bases, is the most diverse group (45% of the catalogue), and comprises a bulk of species (e.g., Orthotrichum scanicum , Orthotrichum ibericum , Orthotrichum speciosum var. brevisetum ) that makes this site especially original. The profiles of the recorded bryoflora (dominance of Orthotrichaceae and Pottiaceae, prevalence of cushions and short turfs and high similarity of tree base and trunk bryophyte communities) indicate an epiphytic bryoflora mainly conditioned by the dry climate. However, the species richness and the biogeographical profile (e.g., dominance of temperate element and occurrence of species that have mesic affinities), together with the altitude influence on structure and composition of bryophyte communities, suggest the existence of microclimatic factors that soften the environmental aridity. This softening effect could be more important at higher altitudes, which are floristically richer than the lower ones.

Understanding the mechanisms of ecological succession is fundamental to predict recovery patterns and restore the increasingly disturbed marine habitats; the season in which disturbance occurs severely affects these processes but this factor has not been thoroughly studied in sublittoral cliffs. Thus, seasonal patterns of benthic colonization and succession were investigated on a temperate rocky cliff (Aegean Sea, eastern Mediterranean). Cement panels, seasonally installed on the rocky substratum at 25-30 m depth, were sampled every 3 months over a 1-year period each, yielding 40 floral and 158 animal species. Diversity, cover and abundance were very low at the initial immersion period and increased toward the late periods. The immersion period and the season of installation had a strong effect on diversity and abundance; decapods showed increased colonization on panels installed in spring, and polychaetes on hibernal panels. The vagile fauna responded to the increasing habitat complexity offered by the development of algal turfs and sessile species. Community structure remained highly dynamic up to the end of the experimental installation and quite different from that of the surrounding benthic community. Two stages of succession, considering vagile and sessile biota, either separately or altogether, were observed over immersion periods; the first was characterized by high variability that can be related to the presence of different colonizers in different seasons, whereas the second, exhibited higher species richness and abundance and showed increased endogenous similarity. Thus, regardless of the season colonization started the developed communities converged toward a common structure, after one year of immersion. An exception was hibernal installation, in which the 12-month immersion period was recognized as a third stage characterized by increased diversity also showing an increased similarity with the adjacent algal community; this suggests that benthic colonization in such environments is faster when succession starts in winter.

An alluvial river channel typically meanders by eroding its outer banks and depositing sediments on the inside of bends, producing new land surfaces. Over time the landscape pattern created by these processes is important to the understanding of riparian plant ecology and the spatial structure of riparian forest development for restoration planning and design as well as other purposes. The middle sector of the Sacramento River is an actively meandering channel that deposits sediments in discrete new areas from fluvial geomorphic events creating a land age gradient. Newly formed land undergoes a primary succession by woody species such as willow and cottonwood communities that provide habitat for important conservation target species in California. Conservation and restoration of primary and secondary successional processes is an important management goal on the Sacramento River. The objectives of this paper were: (1) to develop and codify new methods to track the surficial chronological patterns of floodplain land age in a meandering river system, and (2) to analyze land production and the spatial distributions of gravel bars, riparian vegetation communities, and forest structure in relation to the land age gradient. Results from the ecological analysis indicate 71% of extant riparian vegetation was located within the 101-year meander zone; willow (18%) and cottonwood (31-43%) had the highest proportional canopy cover on lands aged 1-9 and 10-44 years, respectively. Potential applications of this approach for conservation and restoration planning and design of alluvial river floodplains are discussed.

Santorini (S Cyclades, Greece) is one of the active volcanoes of the South Aegean volcanic arc, with more than 12 major eruptions during the past 250,000 years. Our research, using a set of 93 phytosociological relevés, focused on the two volcanic islands of Palea Kameni (PK) and Nea Kameni (NK), differing in age and history of vegetation development. Numerical classifi cation techniques were used to defi ne plant communities, and Redundancy Analysis (RDA) was used to investigate the main environmental gradients and identify the explanatory variables with a unique signifi cant contribution to the explanation of the communities' fl oristic composition. In RDA environmental factors such as altitude, slope inclination, relief, aspect, age of geological substrate, distance from the shore, and selected Ellenberg Indicator Values (EIVs) were used. In order to test the robustness of the RDA results, principal components analysis was applied to the relevés data set as well. Partial RDAs (variance partitioning) were also applied to investigated the proportion of variance attributed to the age of the lava substrate as compared to the rest of environmental factors. The classifi cation revealed seven plant communities (four on PK and three on NK), described in terms of unique species composition, characteristic ecology, and distribution. Three of the communities were dominated by perennials (all found on PK), while the other communities were built prevalently of therophytes (all communities found on NK and one occurring on PK). The age of lava substrate was found among the most important and statistically signifi cant variables. Furthermore, EIVs for light, nitrogen, reaction, and salinity were found to explain relatively high and statistically signifi cant proportions of species data variance. However, the proportion of variance attributed purely to the age of lava substrate was by far smaller than that attributed to the rest explanatory variables. Conclusively, we suggest that the formation of local pioneer vegetation on the studied volcanic islands is not solely controlled by the age of the substrate ("maturation" of the communities through saturation of their local species pools), but it is also under strong control of factors such as the distribution of ashes after the recent volcanic eruptions, and the chemical and physical properties (e.g. nutrient content) of the soils formed by the deposition of the ashes.

Background: Herbivory is an important top-down force on coral reefs that regulates macroalgal abundance, mediates competitive interactions between macroalgae and corals, and provides resilience following disturbances such as hurricanes and coral bleaching. However, reductions in herbivore diversity and abundance via disease or over-fishing may harm corals directly and may indirectly increase coral susceptibility to other disturbances.

are useful markers of the mycorrhizal role in plant nitrogen supply because discrimination against 15 N during creation of transfer compounds within mycorrhizal fungi decreases the 15 N/ 14 N in plants (low d 15 N) and increases the 15 N/ 14 N of the fungi (high d 15 N). Analytical models of 15 N distribution would be helpful in interpreting d 15 N patterns in fungi and plants. To compare different analytical models, we measured nitrogen isotope patterns in soils, saprotrophic fungi, ectomycorrhizal fungi, and plants with different mycorrhizal habits on a glacier foreland exposed during the last 100 years of glacial retreat and on adjacent nonglaciated terrain. Since plants during early primary succession may have only limited access to propagules of mycorrhizal fungi, we hypothesized that mycorrhizal plants would initially be similar to nonmycorrhizal plants in d 15 N and then decrease, if mycorrhizal colonization were an important factor influencing plant d 15 N. As hypothesized, plants with different mycorrhizal habits initially showed similar d 15 N values (À4 to À6& relative to the standard of atmospheric N 2 at 0&), corresponding to low mycorrhizal colonization in all plant species and an absence of ectomycorrhizal sporocarps. In later successional stages where ectomycorrhizal sporocarps were present, most ectomycorrhizal and ericoid mycorrhizal plants declined by 5-6& in d 15 N, suggesting transfer of 15 N-depleted N from fungi to plants. The values recorded (À8 to À11&) are among the lowest yet observed in vascular plants. In contrast, the d 15 N of nonmycorrhizal plants and arbuscular mycorrhizal plants declined only slightly or not at all. On the forefront, most ectomycorrhizal and saprotrophic fungi were similar in d 15 N (À1 to À3&), but the host-specific ectomycorrhizal fungus Cortinarius tenebricus had values of up to 7&. Plants, fungi and soil were at least 4& higher in d 15 N from the mature site than in recently exposed sites. On both the forefront and the mature site, host-specific ectomycorrhizal fungi had higher d 15 N values than ectomycorrhizal fungi with a broad host range. From these isotopic patterns, we conclude:(1) large enrichments in 15 N of many ectomycorrhizal fungi relative to co-occurring ectomycorrhizal plants are best explained by treating the plant-fungal-soil system as a closed system with a discrimination against 15 N of 8-10& during transfer from fungi to plants, (2) based on models of 15 N mass balance, ericoid and ectomycorrhizal fungi retain up to two-thirds of the N in the plant-mycorrhizal system under the N-limited conditions at forefront sites, (3) sporocarps are probably enriched in 15 N by an additional 3& relative to available nitrogen, and (4) host-specific ectomycorrhizal fungi may transfer more N to plant hosts than non-host-specific ectomycorrhizal fungi. Our study confirms that nitrogen isotopes are a powerful tool for probing nitrogen dynamics between mycorrhizal fungi and associated plants.

Attempts to understand how communities assemble following a disturbance are challenged by the difficulty of determining the relative importance of stochastic and deterministic processes. Biological legacies, which result from organisms that survive a disturbance, can favour deterministic processes in community assembly and improve predictions of successional trajectories. Recently disturbed ecosystems are often so rapidly colonized by propagules that the role of biological legacies is obscured. We studied biological legacies on a remote volcanic island in Alaska following a devastating eruption where the role of colonization from adjacent communities was minimized. The role of biological legacies in the near shore environment was not clear, because although some kelp survived, they were presumably overwhelmed by the many vagile propagules in a marine environment. The legacy concept was most applicable to terrestrial invertebrates and plants that survived in remnants of buried soil that were exposed by post-eruption erosion. If the legacy concept is extended to include ex situ survival by transient organisms, then it was also applicable to the island's thousands of seabirds, because the seabirds survived the eruption by leaving the island and have begun to return and rebuild their nests as local conditions improve. Our multi-trophic examination of biological legacies in a successional context suggests that the relative importance of biological legacies varies with the degree of destruction, the availability of colonizing propagules, the spatial and temporal scales under consideration, and species interactions. Understanding the role of biological legacies in community assembly following disturbances can help elucidate the relative importance of colonists versus survivors, the role of priority effects among the colonists, convergence versus divergence of successional trajectories, the influence of spatial heterogeneity, and the role of island biogeographical concepts.

A small ichthyological fauna has been sustained for at least eight years in two fissures in an extensive lava shield on the southeastern coast of the Island of Hawai'i. This freshwater ecosystem contains bacterial mats that likely serve as food source for Macrobrachium grandimanus, the only species of macro-invertebrate found in the cracks. Six species of diatoms make up the primary production community of the cracks. These diatom species were found to serve as food source for Sicyopterus stimpsoni, an endemic amphidromous Hawaiian goby and the only vertebrate species found in this freshwater system. This unique system's extreme species paucity can be attributed to the remoteness of the site and the absence of a source stream up current from the fissures.

The co-existence of two arbuscular mycorrhizal fungal (AMF) species, Glomus intraradices and Glomus claroideum, in the root systems of plants was investigated in a greenhouse experiment aimed at reconstructing interactions during an early stage of primary succession on a coal-mine spoil bank in Central Europe. Two plant species, Tripleurospermum inodorum and Calamagrostis epigejos, were inoculated either with one or both AMF species. Fungal development, determined by trypan blue and alkaline phosphatase staining as well as by PCR amplification of rRNA genes with speciesspecific primers, and the expression of five genes with different metabolic functions in the intraradical structures of G. intraradices were followed after 6 and 9 weeks of cultivation. The two AMF closely co-existed in the root systems of both plants possibly through similar colonisation rates and competitivity. Inoculation with the two fungi, however, did not bring any additional benefit to the host plants in comparison with single inoculation; moreover, plant growth depression observed after inoculation with G. claroideum persisted also in mixed inoculation. The expression of all the assayed G. intraradices genes was affected either by host plant or by co-inoculation with G. claroideum. The effects of both factors depended on the time of sampling, which underlines the importance of addressing this topic in time-course studies.

1Large-scale destruction of ecosystems caused by surface mining provides an opportunity for the study of colonization processes starting with primary succession. Surprisingly, over several decades and without any restoration measures, most of these sites spontaneously developed into valuable biotope mosaics with many endangered plant species.2Investigations were carried out in 10 open-cast mined sites. Data from extensive floristic mapping of mined sites and their surroundings were combined with functional traits.3Using binary logistic regression, we showed that eight variables have a significant influence on the probability of the occurrence of particular plant species in mined sites. The regional species pool explained the highest proportion of variance. Further significant variables were distance of source populations, abundance in the habitat species pool, capacity for long-distance dispersal by wind and birds, terminal velocity of seeds and requirements for light and nitrogen.4In the 10 study mine sites, 143 establishing events of Red List species have been recorded. For 40% of these establishing events, the nearest recorded seed source is 3–10 km away, while for 19%, the distance to the nearest seed source exceeds 10 km.5This study showed for the first time that the abundance of species up to a distance of at least 17 km plays an important role in colonization processes following large-scale destruction of ecosystems. In large-scale, nutrient-deficient, open sites, an accumulation of plant species, including rare species, can be expected in time frames amenable to planning (several decades), because the sites acted as huge seed traps in the landscape.6Synthesis and applications. The floristic colonization probability of restoration sites is higher if large-scale, open and nutrient-poor habitats are available. In regions where such habitats have become highly fragmented, restoration planning of derelict land (e.g. surface mines, quarries, landfills) that supports the creation of such conditions can contribute to the regional survival of rare pioneer species. In future restoration planning, a new protocol must be established that combines the utilization of site potential with spontaneous colonization processes.Large-scale destruction of ecosystems caused by surface mining provides an opportunity for the study of colonization processes starting with primary succession. Surprisingly, over several decades and without any restoration measures, most of these sites spontaneously developed into valuable biotope mosaics with many endangered plant species.Investigations were carried out in 10 open-cast mined sites. Data from extensive floristic mapping of mined sites and their surroundings were combined with functional traits.Using binary logistic regression, we showed that eight variables have a significant influence on the probability of the occurrence of particular plant species in mined sites. The regional species pool explained the highest proportion of variance. Further significant variables were distance of source populations, abundance in the habitat species pool, capacity for long-distance dispersal by wind and birds, terminal velocity of seeds and requirements for light and nitrogen.In the 10 study mine sites, 143 establishing events of Red List species have been recorded. For 40% of these establishing events, the nearest recorded seed source is 3–10 km away, while for 19%, the distance to the nearest seed source exceeds 10 km.This study showed for the first time that the abundance of species up to a distance of at least 17 km plays an important role in colonization processes following large-scale destruction of ecosystems. In large-scale, nutrient-deficient, open sites, an accumulation of plant species, including rare species, can be expected in time frames amenable to planning (several decades), because the sites acted as huge seed traps in the landscape.Synthesis and applications. The floristic colonization probability of restoration sites is higher if large-scale, open and nutrient-poor habitats are available. In regions where such habitats have become highly fragmented, restoration planning of derelict land (e.g. surface mines, quarries, landfills) that supports the creation of such conditions can contribute to the regional survival of rare pioneer species. In future restoration planning, a new protocol must be established that combines the utilization of site potential with spontaneous colonization processes.

Changes in rotifer soil communities along a primary succession chronosequence was studied on brown coal post mining areas near Sokolov, NW part of the Czech Republic. The chronosequence of unreclaimed plots was 2, 11, 14, 20, 43 years old. The rotifers were extracted from soil samples using a modification of the Baermann funnel method with combined light and temperature gradients.

In this study we hypothesized that a change in the composition of vegetation communities is closely linked to a concurrent change in the structure of microbial communities through the decisive role of plant residues in regulating the quality of carbon sources for soil microbes. The study was carried out in a boreal forest along an 80-m-long successional transect (willow, alder, birch, spruce) located on the landuplift coast of the Gulf of Bothnia, western Finland. The field and ground layer vegetation were recorded by species percentage cover on 2 m 2 sample plots located at 10 m intervals. Organic layer samples were taken from around each vegetation sample plot for the determination of phospholipid fatty acid (PLFA) profiles and chemical composition of the organic layer, as characterized by the concentrations of neutral and acidic sugar units in non-cellulosic polysaccharides, cellulose, the acid-soluble lignin (ASL), and acidinsoluble residue (AIR). The organic layer along the transect showed a decrease in pH (from 5.2 to 4.4), moisture content and concentrations of ASL and the hemicellulosic sugars arabinose, rhamnose, xylose, galactose, and glucuronic acid, while the AIR concentration increased. These organic matter fractions and pH also showed a strong positive or negative correlation with the vegetation and the PLFA ordination. The percentage cover of grasses significantly correlated with the PLFA data, as well as with that of herbs and field layer species. However, PLFA ordination showed a higher correlation with the organic layer properties than with the coverage of plant species groups. In conclusion, our data showed a strong directional relationship between the organic matter characteristics and structure of the vegetation and microbial communities along the study transect. This study is, to our knowledge, the first investigation to apply acid methanolysis in the characterization of non-cellulosic polysaccharides in the organic layer.

Very little is known about the degree and ecological correlates of mycorrhization of lycophytes and ferns, although mycorrhizae are believed to be crucial for the majority of land plants. We screened the degree of mycorrhizal colonization for all 75 fern species recorded in nine survey plots across a wide range of soil conditions on the island of La Réunion, including five plots on lava flows of different age. Overall, 66% of all samples had mycorrhizae, but ground-dwelling species had significantly higher colonization levels (78%) than epiphytes (58%). Among ground-dwelling species, 98% of the individuals belonged to species with mycorrhizae, which was significantly higher than at the species level. Most samples had glomeromycetes as fungal partners, but septate endophytes were found in 41% of the colonized samples. While we found no significant relationship between the percentage of fern species with mycorrhizae per plot and seven ecological parameters, the percentage of fern individuals with mycorrhizal colonizations per plot significantly increased on shallow soils with high pH values and high base-saturation. This supports the idea that mycorrhizal colonizations confer an ecological advantage to colonized individuals, and that this advantage is more pronounced on nutrient-deficient sites. Our study thus provides evidence for an ecological advantage of mycorrhizae for ferns, but raises the question why, despite this advantage, species level mycorrhization among ferns (68%) is so much lower than the average for land plants (85%).

Patterns of community development vary among studied glacier forelands around the world. However, there have been few studies of primary succession on glacial forelands in temperate regions of North America. We described patterns in community composition, vegetation cover, diversity, and vegetation heterogeneity during primary succession on the foreland of Coleman Glacier, in Washington State, USA. Community composition changed rapidly with high turnover between age classes. Cover increased through succession as expected. Species richness and diversity were highest in early succession at small scales and in late succession at larger scales. At small scales, heterogeneity decreased in early succession but increased in mature sites. At larger scales, heterogeneity reached its lowest point earlier in succession. These scaledependent patterns in diversity and heterogeneity differ from results of other studies of glacier forelands. We hypothesize that these patterns arise due to the development of a dense canopy of the deciduous shrub Alnus viridis followed by a dense canopy of Abies amabilis, Tsuga heterophylla, and Pseudotsuga menziesii.

Very little is known about the degree and ecological correlates of mycorrhization of lycophytes and ferns, although mycorrhizae are believed to be crucial for the majority of land plants. We screened the degree of mycorrhizal colonization for all 75 fern species recorded in nine survey plots across a wide range of soil conditions on the island of La Réunion, including five plots on lava flows of different age. Overall, 66% of all samples had mycorrhizae, but ground-dwelling species had significantly higher colonization levels (78%) than epiphytes (58%). Among ground-dwelling species, 98% of the individuals belonged to species with mycorrhizae, which was significantly higher than at the species level. Most samples had glomeromycetes as fungal partners, but septate endophytes were found in 41% of the colonized samples. While we found no significant relationship between the percentage of fern species with mycorrhizae per plot and seven ecological parameters, the percentage of fern individuals with mycorrhizal colonizations per plot significantly increased on shallow soils with high pH values and high base-saturation. This supports the idea that mycorrhizal colonizations confer an ecological advantage to colonized individuals, and that this advantage is more pronounced on nutrient-deficient sites. Our study thus provides evidence for an ecological advantage of mycorrhizae for ferns, but raises the question why, despite this advantage, species level mycorrhization among ferns (68%) is so much lower than the average for land plants (85%).

Non-native invasive plants can greatly alter community and ecosystem properties, but efforts to predict which invasive species have the greatest impacts on these properties have been generally unsuccessful. An hypothesis that has considerable promise for predicting the effects of invasive non-native plant species is the mass ratio hypothesis (i.e. that dominant species exert the strongest effects). We tested this hypothesis using data from a four year removal experiment in which the presence of two dominant shrub species (one native and the other not), and subordinate plant species, were manipulated in factorial combinations over four years in a primary successional floodplain system. We measured the effects of these manipulations on the plant community, soil nutrient status and soil biota in different trophic levels of the soil food web. Our experiment showed that after four years, low-biomass non-native plant species exerted disproportionate belowground effects relative to their contribution to total biomass in the plant community, most notably by increasing soil C, soil microbial biomass, altering soil microbial community structure and increasing the abundance of microbial-feeding and predatory nematodes. Low-biomass, non-native plant species had distinct life history strategies and foliar traits (higher foliar N concentrations and higher leaf area per unit mass) compared with the two dominant shrub species (97% of total plant mass). Our results have several implications for understanding species' effects in communities and on soil properties. First, high-biomass species do not necessarily exert the largest impacts on community or soil properties. Second, low-biomass, inconspicuous non-native species can influence community composition and have important trophic consequences belowground through effects on soil nutrient status or resource availability to soil biota. Our finding that low-biomass non-native species influence belowground community structure and soil properties more profoundly than dominant species demonstrates that the mass ratio hypothesis does not accurately predict the relative effects of different coexisting species on community-and ecosystem-level properties.

Question: How do Coriaria arborea, an N-fixing native shrub, and Buddleja davidii, a non-N-fixing exotic shrub, affect N:P stoichiometry in plants and soils during early stages of primary succession on a flood-plain? Location: Kowhai River Valley, northeast South Island, New Zealand. Methods: We measured soil and foliar nutrient concentrations, light levels, plant community composition and the aboveground biomass of Coriaria and Buddleja in four successional stages: open, young, vigorous and mature. Results: Coriaria occurred at low density but dominated above-ground biomass by the vigorous stage. Buddleja occurred at 5.3 ± 1.0 stems/m 2 in the young stage and reached a maximum biomass of 520-535 g.m -2 during the young and vigorous stages. Mineral soil N increased with above-ground Coriaria biomass (r 2 = 0.45), but did not vary with Buddleja biomass. In contrast, soil P increased with Buddleja biomass (r 2 = 0.35), but not with Coriaria biomass. In early successional stages, 70-80% of the species present were exotic, but this declined to about 15% by the mature stage. Exotic plant species richness declined with increasing Coriaria biomass, but no other measures of diversity varied with either Coriaria or Buddleja biomass. Conclusion: These results demonstrate that Buddleja dominates early succession and accumulates P whereas Coriaria dominates later succession and accumulates N. A key ecosystem effect of the invasive exotic Buddleja is alteration of soil N:P stoichiometry.

Questions: How does vegetation first establish on newlyformed lava substrates? Do very small (cm) and meso-scale (m) variations in the physical environment influence this process and subsequent vegetation development? Location: Mount Hekla, southern Iceland (64°00' N, 19°40' W).

Primary succession on the Tanana river floodplain progresses from alder, with C-limited microbes and rapid nitrification, to poplar, with N-limited microbes and little nitrification. To determine the mechanisms controlling this shift, a reciprocal soil transplant experiment was conducted between alder and poplar sites. Mineralization rates (gross and net) and nitrification potentials were measured periodically over 1 year. Nitrification potentials of both soils were higher in the alder site, but transplanted soils showed higher gross rates of N turnover than soils in their native site. Thus, C additions from poplar alleviated C limitation in alder soils, accelerating N turnover, but with a net reduction in N availability to nitrifiers. Transplanting poplar soil to the alder site alleviated N limitation, accelerating N turnover while increasing net N availability. The changes in N cycling between alder and poplar were therefore controlled by changes in N turnover and availability.

Shrub willows (Salix spp.) form associations with arbuscular mycorrhizal (AM), ectomycorrhizal (EM) and dark septate endophytic (DSE) fungi. Willow root colonization by these three types of fungi was studied on a deglaciated forefront of Lyman Glacier, Washington, USA. Root colonization was low; less than 1% of the root length was colonized by AM and 25.6% by DSE. EM colonized 25% of the root tips and 19.4% of the root length. AM and DSE colonization were not related to distance from the present glacier terminus or to canopy cover. EM colonization increased with distance from the glacier terminus based on gridline intercept data but not on root tip frequency data. Availability of propagules in the substrate was low, but numbers of propagules increased with distance from the glacier terminus. The EM communities were dominated by three ascomycetes showing affinity to Sordariaceae in BLAST analyses. Other frequent taxa on the glacier forefront included species of Cortinariaceae, Pezizaceae, Russulaceae, Thelephoraceae and Tricholomataceae. When occurrence of individual taxa was used as a response variable to canopy cover, distance from the glacier terminus, and their interaction, four different fungal guilds were identified: 1) fungi that did not respond to these environmental variables; 2) fungi that occurred mainly in intercanopy areas and decreased with distance from the glacier terminus; 3) fungi that were insensitive to canopy cover but increased with distance from the glacier terminus; 4) fungi that occurred mainly under willow canopies and increased with distance from the glacier terminus. We suggest that fungal colonization is mainly limited by fungal propagule availability. Environmental conditions may also limit successful establishment of plant-fungus associations. We propose that the four EM guilds partly explain successional dynamics. The initial EM commu-nity comprises fungi that tolerate low organic matter and nitrogen environment (first and second guilds above). During later community development, these fungi are replaced by those that benefit from an increased organic matter and nitrogen environment (third and fourth guilds above).

As study area we selected the glacier foreland of Morteratsch (approx. 1900–2100 m a.s.l.) near Pontresina northwest of the Bernina pass, Upper Engadine, Grisons (Switzerland). The aim of this study is a multimethodological approach using floristic inventories, vegetation and soil mapping of the pro-glacial area in order to detect crucial parameters controlling plant resettlement in recently deglaciated areas as related to time, local microtopography and soil development.The following methodological approaches were included in this study: (i) floristic relevees along a chronosequence covering 134 years (1857–1990); (ii) dendrochronological data on tree establishment, collected on a grid with a mesh width of 40 m in the area, which became ice-free between 1857 and 1980; (iii) vegetation mapping; (iv) soil analyses including physical and chemical properties of 11 typical profiles; (v) soil mapping and (vi) data evaluation using GIS.Retreating glaciers successively expose mineral substrates that are colonised within a few years by vascular plants, mosses, lichens and soil biota. With increasing plant cover, also the abundance of soil organic matter increases. At first sight, the large-scale patterns of vegetation and soil seem to be driven by the time since deglaciation, whereas the small scale patterns may appear chaotic since they depend on local site conditions, which may change dramatically over short distances.The large-scale pattern seems to develop as follows. About 7 years after deglaciation the first pioneer plants establish themselves and form after an additional 20 years period the Epilobietum fleischeri community, which today dominates the recently deglaciated areas, but may be found in patches more or less on the whole pro-glacial area. By contrast, the first elements of the short living Oxyrietum digynae community appear approximately 10 years after deglaciation and persist for only about 30 years. Dendrochronology showed that the first European larch and Swiss stone pine trees established themselves 15 and 31 years, respectively, after deglaciation. Surprisingly, on the study area, Swiss stone pine is about twice as frequent as the typical pioneer species European larch (88 stems per ha vs. 45 stems per ha), despite the fact that larch starts earlier and grows faster than Swiss stone pine (annual height increment: 21 cm vs. 8 cm). Up-to-now, however, nowhere in the 150-year-old glacier foreland a near-to-mature larch-Swiss stone pine forest can be found.Besides large-scale factors such as time since deglaciation, topography and disturbance (floods, rockfalls, avalanches), also small-scale factors such as grain size and water content of the substrate, micro-relief and micro-climate seem to be crucial for the development of both vegetation and soil. Time since deglaciation and a straightforward single-pathway succession model are clearly not sufficient for understanding the small-scale patterns of succession. A non-linear succession model with different starting points and different pathways of potential primary successions for the different ecological niches is more promising for describing accurately the spatio-temporal vegetation dynamics of the pro-glacial area of Morteratsch.

Current models of ecosystem development hold that low nitrogen availability limits the earliest stages of primary succession, but these models were developed from studies conducted in areas with temperate or wet climates. Global warming is now causing rapid glacial retreat even in inland areas with cold, dry climates, areas where ecological succession has not been adequately studied. We combine field and microcosm studies of both plant and microbial primary producers and show that phosphorus, not nitrogen, is the nutrient most limiting to the earliest stages of primary succession along glacial chronosequences in the Central Andes and central Alaska. We also show that phosphorus addition greatly accelerates the rate of succession for plants and for microbial phototrophs, even at the most extreme deglaciating site at over 5000 meters above sea level in the Andes of arid southern Peru. These results challenge the idea that nitrogen availability and a severe climate limit the rate of plant and microbial succession in cold-arid regions and will inform conservation efforts to mitigate the effects of global change on these fragile and threatened ecosystems.

Little is known about the changes in microbial diversity associated with ecosystem development. We measured microbial heterotrophic evenness (a component of diversity) and other soil/humus properties (including basal respiration, substrate-induced respiration, pH, total C, N and P) at different stages in the development of ®ve different ecosystems, with plant assemblages being used to de®ne the phase in the successional sequence. Our objectives were to determine whether there were common patterns in establishment of microbial heterotrophic evenness with ecosystem development and whether changes in evenness were correlated to soil properties. Samples were collected from ®ve sequences: Gisborne land slips (a chronosequence of re-vegetating landslip scars); Mount Tarawera (primary succession on aeriallydeposited ash from a volcanic eruption); Rangitoto island (primary succession on a lava¯ow from a volcanic eruption); Franz Josef (primary succession initiated on gravels after the retreat of a glacier); and Swedish islands (a series of islands of differing size supporting different stages of plant succession). Heterotrophic diversity was measured using the catabolic response pro®le technique where CO 2 ef¯ux is measured during a 4-h incubation of samples amended with 25 different carbon substrates. Heterotrophic evenness was calculated from the CO 2 responses using the Simpson±Yule index (maximum possible is 25). For Tarawera and Gisborne sequences, heterotrophic evenness was signi®cantly lower at the ®rst stage of succession (11.5 and 19.9, respectively), but subsequently plateaued, ranging between 21 and 23. Heterotrophic evenness declined signi®cantly with succession at Rangitoto and Franz Josef sequences, but there was no trend along the Swedish island sequence. Despite the lack of a common pattern of heterotrophic evenness along all the sequences, there were signi®cant linear correlations between heterotrophic evenness and basal respiration for Rangitoto (r 0.51, P , 0.01), Gisborne (r 0.88, P , 0.01) and the Swedish islands sequences (r 0.52, P , 0.01), while the relationship was marginal at Franz Josef (r 0.69, P , 0.06), but not signi®cant at the Tarawera sequence. Plant evenness along two sequences (Rangitoto and Swedish islands) was not correlated with heterotrophic evenness. These data suggest that heterotrophic evenness re-establishes rapidly following major disturbance once organic matter inputs occur then subsequently declines. Patterns of change in heterotrophic evenness may, in part, be dependent on changes in the availability of organic carbon or resources to heterotrophs. q

Four plant communities were determined through floristical and non-metric analysis: a Dolichlasium lagascae community in crevices on sunny rock outcrops; a Cercidium praecox ssp. glaucum community on sunny slopes; an Artemisia mendozana}Adesmia trijuga community on shady slopes; and a Eupatorium buniifolium community on dry riverbanks. The discriminant function analysis showed that the first group corresponds to the sunny rock outcrops discriminated by Na content (r"0·53, p(0·05), the second group is for sunny slopes discriminated by electric conductivity and the third for shady slopes}riparian discriminated by the (Ca#Mg) content (r"0·54, p(0·05). A pattern of primary succession on outcrop surfaces is proposed.

. Primary succession refers to the establishment of plant species and subsequent changes in composition following major disturbance such as volcanic activity. The study of succession may assist in recognizing the possible effects of species interactions (i.e. facilitation or inhibition). The barren landscapes created by volcanic disturbance on Mount Merapi, Java, Indonesia, provide excellent opportunities to study primary succession. Fifty-six species belonging to 26 families were recorded in the five nuées ardentes deposits. The highest number of species belonged to the Asteraceae, then Poaceae, followed by Fabaceae and Rubiaceae. In Mount Merapi primary succession, the ecosystem may be developing with time as indicated by the increase in the number of species associations. The number of positive associations was generally higher than the number of negative associations, except in the 2001 deposit where it was equal. Native and alien invasive species had different patterns of interspecific associations. This research demonstrates that in primary succession sites on Mount Merapi, positive interspecific association increased as time progressed, which may support the view that facilitation is more prominent in a severely disturbed habitat as compared to competition.

Study Objective: To compare two methods of double-lumen endobronchial tube placement for thoracic surgery and to identify factors that provide a rational basis for placement method selection. Design: Prospective, randomized study. Setting: Teaching hospital. Patients: 58 ASA physical status II, III, and IV patients scheduled for surgical procedures requiring elective left-sided endobronchial intubation. Interventions: Patients were assigned randomly to either a group in which the initial placement method was the traditional approach of placing the endobronchial tube through the larynx and then advanced blindly into the left mainstem bronchus, or to a second group in which the left mainstem bronchus was intubated under direct vision using the fiberoptic bronchoscope. Measurements and Main Results: Of the 32 patients who underwent the traditional approach, primary success occurred in 27 patients and eventual success in 30. In 27 patients undergoing the directed approach, primary success occurred in 21 patients and eventual success in 25. Two patients in each group required the alternative method. The blind approach took 88 (Ϯ91) seconds and the directed approach took 181 (Ϯ193) seconds (p ϭ 0.029). Timing data were analyzed using analysis of variance with respect to method and secretions and then t-tests as appropriate. Categorical data were analyzed using the Kruskal-Wallis and Fisher's exact tests as appropriate. All values are reported as means Ϯ SD. Conclusion: Both the blind and directed approaches resulted in successful left mainstem placement of the endobronchial tube in the majority of patients but either method may fail when used alone. More time was required using the directed approach. Operator experience with both methods will increase the likelihood of success. The choice of the initial approach may be influenced by patient factors as well as available equipment and personnel.

Texture is an important influence on organic matter (SOM) dynamics in upland soils but little is known about its role in riverine soils. We hypothesized that texture might be especially important to SOM accumulation in young alluvial soils. We combined the soil component of the CENTURY ecosystem model, which uses sand, silt, and clay concentration as primary variables, with a simple simulation model of fluvial deposition, and forest production to predict changes in soil carbon (C) and nitrogen (N) during primary succession on floodplains and terraces of the Queets River, Washington. Simulated soil C accumulated to a plateau of about 4000 g m -2 at 110 years, closely matching observed patterns in an empirical chronosequence. Although direct fluvial OM deposition had only a small and short-lived influence on soil C, fluvial silt and clay deposition were an important influence on equilibrium C. The model underestimated soil N by about 35%, which appears to be due to failure of the model to account for N enrichment of an OM pool after its initial formation. These results suggest that basic influences on SOM retention in these young soils are not functionally different than those that apply to upland soils, but occur within highly dynamic physical contexts. Overbank deposition of silt and clay establishes a basic capacity for SOM retention. SOM, in turn, facilitates N retention. In this way, silt and clay are instrumental in propagating N forward from N-fixing red alder (Alnus rubra) stands to mature conifer forests that are frequently N-limited.

In early stages of primary succession, colonizing plants can create resource patches that influence the abundance and distribution of other species. To test whether different colonizing shrubs generate contrasting patches on coastal sand dunes, we compared soil characteristics and light availability under the nitrogen-fixing shrub Lupinus arboreus, under the non-nitrogen-fixing shrub Artemisia pycnocephala, and between shrubs on dunes at a site in northern California. Concentrations of inorganic nitrogen and net nitrogen mineralization rates were generally 1–10 times greater in soil under Lupinus than under Artemisia or between shrubs. Soil water content was mostly lower under shrubs. Mean photon flux density near ground level was reduced by at least 80% at ≥ 35 cm inside shrub canopies. Topography appeared to have more effect on soil moisture but less direct effect on nitrogen availability than did Lupinus. However, Lupinus probably increases nitrogen levels more on higher, drier dunes. Microhabitats under and between nitrogen-fixing shrubs constitute a mosaic of individually poor but complementary patches in which high levels of light and moderate levels of soil nitrogen are present but tend not to occur together.

As an aid for restoration projects, the relative potential for plants to immigrate to sites after severe disturbance was investigated and an index developed to determine their relative immigration potential. The goal was to establish baseline knowledge for the species pool in severely disturbed sites prior to restoration. The method was based on the identification of potential colonists, inventories of populations in surrounding vegetation and autecological information on their maximum fecundity and dispersal by wind, water or animals. 2. The method was applied to milled peatlands in south-eastern Quebec, Canada, after the cessation of peat extraction activities. Thirty-two species, ranging from mosses to trees, which are common in natural or abandoned milled peatlands in southern Quebec, were selected as potential colonists. 3. Populations of study species differed markedly in edges of milled peatlands in terms of their abundance, presence and presence of fertile plants. An edge effect was apparent where the populations of many species varied as a function of distance from milled surfaces, caused, in part, by drainage. 4. Mosses had relatively high potential to immigrate to milled bogs because of their high fecundity and the wind-dispersal ability of their spores. The scarcity of mosses in abandoned milled bogs did not appear to be a result of the lack of immigrant propagules. Herbs had relatively low immigration potential, due to their rarity in edges, but herbs such as Eriophorum vaginatum were able to recolonize milled bogs in spite of this low potential. Shrub species generally had high immigration potential because of their abundance at edges and the high dispersal ability of propagules by wind, water and animals. Trees had high immigration potential due to their abundance at edges and their wind-dispersal abilities. 5. Synthesis and applications. An index of immigration potential provides information on the probable initial species pool after severe disturbance, against which the effects of local habitat suitability and establishment factors can be added to assess probable successional patterns. Its flexibility and applicability to varied life forms should make it useful for diagnosing recolonization bottlenecks in a wide variety of disturbance and restoration situations. It also allows for an assessment of the relative need for introducing species during the restoration of severely disturbed environments.

Question: How do Coriaria arborea, an N-fixing native shrub, and Buddleja davidii, a non-N-fixing exotic shrub, affect N:P stoichiometry in plants and soils during early stages of primary succession on a flood-plain? Location: Kowhai River Valley, northeast South Island, New Zealand. Methods: We measured soil and foliar nutrient concentrations, light levels, plant community composition and the aboveground biomass of Coriaria and Buddleja in four successional stages: open, young, vigorous and mature. Results: Coriaria occurred at low density but dominated above-ground biomass by the vigorous stage. Buddleja occurred at 5.3 ± 1.0 stems/m 2 in the young stage and reached a maximum biomass of 520-535 g.m -2 during the young and vigorous stages. Mineral soil N increased with above-ground Coriaria biomass (r 2 = 0.45), but did not vary with Buddleja biomass. In contrast, soil P increased with Buddleja biomass (r 2 = 0.35), but not with Coriaria biomass. In early successional stages, 70-80% of the species present were exotic, but this declined to about 15% by the mature stage. Exotic plant species richness declined with increasing Coriaria biomass, but no other measures of diversity varied with either Coriaria or Buddleja biomass. Conclusion: These results demonstrate that Buddleja dominates early succession and accumulates P whereas Coriaria dominates later succession and accumulates N. A key ecosystem effect of the invasive exotic Buddleja is alteration of soil N:P stoichiometry.

Landslides are excellent illustrations of the dynamic interplay of disturbance and succession. Restoration is difficult on landslide surfaces because of the high degree of spatial and temporal heterogeneity in soil stability and fertility. Principles derived from more than a century of study of ecological succession can guide efforts to reduce chronic surface soil erosion and restore both biodiversity and ecosystem function. Promotion of the recovery of self-sustaining communities on landslides is feasible by stabilization with native ground cover, applications of nutrient amendments, facilitation of dispersal to overcome establishment bottlenecks, emphasis on functionally redundant species and promotion of connectivity with the adjacent landscape. Arrested succession through resource dominance by a single species can be beneficial if that species also reduces persistent erosion, yet the tradeoff is often reduced biodiversity. Restoration efforts can be streamlined by using techniques that promote successional processes.

Positive plant-soil feedback by “ecosystem engineers” is an important driver for the structuring and organization of resource-limited ecosystems. Although ample evidence demonstrates that plant-soil feedbacks can range from positive to strongly negative, their co-occurrence in plant communities have not yet been investigated. We test the hypothesis that the plant-soil feedback generated by the nitrogen-fixer shrub Medicago marina during primary succession in a sand dune community has a positive effect on the coexisting grass Lophochloa pubescens and a negative effect on the shrub species itself. We conducted field measurements and laboratory bioassays to evaluate (1) the effects of islands of fertility on the recruitment and growth of its ecosystem engineer and on the performance of a coexisting species and (2) the mechanisms involved that can explain the opposite effects of islands of fertility on coexisting species. Islands of fertility were present under Medicago crowns evidenced by higher available nitrogen, extractable phosphorus and potassium, organic matter, microbial activity, water holding capacity, soil humidity, and lower salt concentrations. The effects of these islands of fertility were clearly species-specific, with a facilitative impact on Lophochloa and a negative effect on Medicago recruitment. Lophochloa was denser and produced more biomass when rooted inside as compared to outside the crown area of the shrub. Contrarily, the number of seedlings of Medicago was lower inside, despite the higher seed abundance, and higher outside the crown area of adult shrubs as compared to predictions based on random distribution, thus showing a Janzen-Connell distribution. Laboratory experiments demonstrate the occurrence of Medicago negative plant-soil feedback, and that the auto-toxicity of the aboveground senescent plant material is a potentially important underlying mechanism explaining this negative feedback and the resulting Janzen-Connell distribution in the field.

To determine the safety and efficacy of tubeless percutaneous nephrolithotomy (PCNL). Methods: A quasi-experimental study conducted on 50 patients, at a specialized urology centre. Results: The primary success rate of the procedure in terms of stone clearance was 70%. Mean length of hospital stay was 2.44 days. There were no significant complications during or after the surgery. Conclusion: Tubeless PCNL is a safe and effective modification of the conventional procedure. Absence of the nephrostomy tube may help in keeping the patient comfortable after the surgery and reduction in the length of hospital stay (JPMA 57:584;2007).

Post-mining sites Biomass Organic carbon Trapped energy Energy consumption Energy efficiency a b s t r a c t The work presents an assessment of energy efficiency in reclamation to forest as illustrated by an open-cast sand mine in southern Poland. A total of 20 plots of different age class (5, 17, 20 and 25 years old) were set up on reclaimed areas of the open cast or in succession areas.

are useful markers of the mycorrhizal role in plant nitrogen supply because discrimination against 15 N during creation of transfer compounds within mycorrhizal fungi decreases the 15 N/ 14 N in plants (low d 15 N) and increases the 15 N/ 14 N of the fungi (high d 15 N). Analytical models of 15 N distribution would be helpful in interpreting d 15 N patterns in fungi and plants. To compare different analytical models, we measured nitrogen isotope patterns in soils, saprotrophic fungi, ectomycorrhizal fungi, and plants with different mycorrhizal habits on a glacier foreland exposed during the last 100 years of glacial retreat and on adjacent nonglaciated terrain. Since plants during early primary succession may have only limited access to propagules of mycorrhizal fungi, we hypothesized that mycorrhizal plants would initially be similar to nonmycorrhizal plants in d 15 N and then decrease, if mycorrhizal colonization were an important factor influencing plant d 15 N. As hypothesized, plants with different mycorrhizal habits initially showed similar d 15 N values (À4 to À6& relative to the standard of atmospheric N 2 at 0&), corresponding to low mycorrhizal colonization in all plant species and an absence of ectomycorrhizal sporocarps. In later successional stages where ectomycorrhizal sporocarps were present, most ectomycorrhizal and ericoid mycorrhizal plants declined by 5-6& in d 15 N, suggesting transfer of 15 N-depleted N from fungi to plants. The values recorded (À8 to À11&) are among the lowest yet observed in vascular plants. In contrast, the d 15 N of nonmycorrhizal plants and arbuscular mycorrhizal plants declined only slightly or not at all. On the forefront, most ectomycorrhizal and saprotrophic fungi were similar in d 15 N (À1 to À3&), but the host-specific ectomycorrhizal fungus Cortinarius tenebricus had values of up to 7&. Plants, fungi and soil were at least 4& higher in d 15 N from the mature site than in recently exposed sites. On both the forefront and the mature site, host-specific ectomycorrhizal fungi had higher d 15 N values than ectomycorrhizal fungi with a broad host range. From these isotopic patterns, we conclude:(1) large enrichments in 15 N of many ectomycorrhizal fungi relative to co-occurring ectomycorrhizal plants are best explained by treating the plant-fungal-soil system as a closed system with a discrimination against 15 N of 8-10& during transfer from fungi to plants, (2) based on models of 15 N mass balance, ericoid and ectomycorrhizal fungi retain up to two-thirds of the N in the plant-mycorrhizal system under the N-limited conditions at forefront sites, (3) sporocarps are probably enriched in 15 N by an additional 3& relative to available nitrogen, and (4) host-specific ectomycorrhizal fungi may transfer more N to plant hosts than non-host-specific ectomycorrhizal fungi. Our study confirms that nitrogen isotopes are a powerful tool for probing nitrogen dynamics between mycorrhizal fungi and associated plants.

Lyman glacier in the North Cascades Mountains of Washington has a subalpine forefront characterized by a well-developed terminal moraine, inconspicuous successional moraines, fluting, and outwash. These deposits were depleted of symbiotic fungi when first exposed but colonized by them over time after exposure. Four major groups of plant species in this system are (1) mycorrhizaindependent or facultative mycotrophic, (2) dependent on arbuscular mycorrhizae (AM) (3) dependent on ericoid mycorrhiza (ERM) or ectomycorrhizae (EM), and (4) colonized by dark-septate (DS) endophytes. We hypothesized that availability of mycorrhizal propagules was related to the success of mycorrhiza-dependent plants in colonizing new substrates in naturally evolved ecosystems. To test this hypothesis roots samples of 66 plant species were examined for mycorrhizal colonization. The plants were sampled from communities at increasing distances from the glacier terminus to compare the newest communities with successively older ones. Long established, secondary successional dry meadow communities adjacent to the glacier forefront, and nearby high alpine communities were sampled for comparison. DS were common on most plant species on the forefront. Nonmycorrhizal plants predominated in the earlier successional sites, whereas the proportion of mycorrhizal plants generally increased with age of community. AM were present, mostly at low levels, and nearly absent in two sites of the forefront. ERM were present in all species of Ericaceae sampled, and EM in all species of Pinaceae and Salicaceae. Roots of plants in the long established meadow and heath communities adjacent to the forefront and the high alpine community all had one or another of the colonization types, with DS and AM predominating.

We investigated the changes in basal respiration (BASAL), microbial biomass as substrate-induced respiration (SIR) and their ratio (qCO 2 ) in the organic layer along a primary successional transect (alder/rowan, birch, birch/spruce, spruce I and spruce II) typical of the landuplift coast in western Finland. PLFA analysis was used to detect concurrent successional changes in microbial community structure. Along the transect the soil C/N ratio increased (from 16 to 37) and pH (H 2 O) decreased (from 5.11 to 3.98) substantially. Concurrently, BASAL and SIR remained mainly stable although, during the most favorable temperature and moisture conditions in the field, they tended to increase along the transect from the alder/rowan site to spruce I, and decreased again in spruce II. qCO 2 showed no consistent trend along the transect. The soil of the birch site had the highest total PLFA and bacterial PLFA concentrations, while the soils of both spruce sites had the lowest. The ordination configuration of the PLFA data in non-metric multidimensional scaling was clearly related to the C/N ratio and pH, and separated the forest sites relatively well. It was possible, on the basis of the similarities in the variation pattern along the transect, to divide the PLFAs into six groups. q

Santorini (S Cyclades, Greece) is one of the active volcanoes of the South Aegean volcanic arc, with more than 12 major eruptions during the past 250,000 years. Our research, using a set of 93 phytosociological relevés, focused on the two volcanic islands of Palea Kameni (PK) and Nea Kameni (NK), differing in age and history of vegetation development. Numerical classifi cation techniques were used to defi ne plant communities, and Redundancy Analysis (RDA) was used to investigate the main environmental gradients and identify the explanatory variables with a unique signifi cant contribution to the explanation of the communities' fl oristic composition. In RDA environmental factors such as altitude, slope inclination, relief, aspect, age of geological substrate, distance from the shore, and selected Ellenberg Indicator Values (EIVs) were used. In order to test the robustness of the RDA results, principal components analysis was applied to the relevés data set as well. Partial RDAs (variance partitioning) were also applied to investigated the proportion of variance attributed to the age of the lava substrate as compared to the rest of environmental factors. The classifi cation revealed seven plant communities (four on PK and three on NK), described in terms of unique species composition, characteristic ecology, and distribution. Three of the communities were dominated by perennials (all found on PK), while the other communities were built prevalently of therophytes (all communities found on NK and one occurring on PK). The age of lava substrate was found among the most important and statistically signifi cant variables. Furthermore, EIVs for light, nitrogen, reaction, and salinity were found to explain relatively high and statistically signifi cant proportions of species data variance. However, the proportion of variance attributed purely to the age of lava substrate was by far smaller than that attributed to the rest explanatory variables. Conclusively, we suggest that the formation of local pioneer vegetation on the studied volcanic islands is not solely controlled by the age of the substrate ("maturation" of the communities through saturation of their local species pools), but it is also under strong control of factors such as the distribution of ashes after the recent volcanic eruptions, and the chemical and physical properties (e.g. nutrient content) of the soils formed by the deposition of the ashes.

We studied microbial community composition in a primary successional chronosequence on the forefront of Lyman Glacier, Washington, United States. We sampled microbial communities in soil from nonvegetated areas and under the canopies of mycorrhizal and nonmycorrhizal plants from 20-to 80-year-old zones along the successional gradient. Three independent measures of microbial biomass were used: substrate-induced respiration (SIR), phospholipid fatty acid (PLFA) analysis, and direct microscopic counts. All methods indicated that biomass increased over successional time in the nonvegetated soil. PLFA analysis indicated that the microbial biomass was greater under the plant canopies than in the nonvegetated soils; the microbial community composition was clearly dierent between these two types of soils. Over the successional gradient, the microbial community shifted from bacterial-dominated to fungal-dominated. Microbial respiration increased while speci®c activity (respiration per unit biomass) decreased in nonvegetated soils over the successional gradient. We proposed and evaluated new parameters for estimating the C use eciency of the soil microbial community:``Max'' indicates the maximal respiration rate and``Acc'' the total C released from the sample after a standard amount of substrate is added. These, as well as the corresponding speci®c activities (calculated as Max and Acc per unit biomass), decreased sharply over the successional gradient. Our study suggests that during the early stages of succession the microbial community cannot incorporate all the added substrate into its biomass, but rapidly increases its respiration. The later-stage microbial community cannot reach as high a rate of respiration per unit biomass but remains in an``energy-saving state,'' accumulating C to its biomass.

Background: The effect of low nutrient availability on plant-consumer interactions during early succession is poorly understood. The low productivity and complexity of primary successional communities are expected to limit diversity and abundance of arthropods, but few studies have examined arthropod responses to enhanced nutrient supply in this context. We investigated the effects of nitrogen (N) and phosphorus (P) addition on plant productivity and arthropod abundance on 24-yr-old soils at Mount St. Helens volcano.

1. Many ecosystems are gaining some species and losing others, leading to large shifts in community composition. Plants that support nitrogen (N)-fixing symbionts (hereafter N-fixers) are major ecosystem drivers but human-induced environmental changes can lead to their loss; the impacts of this loss have seldom been studied. In New Zealand, the gain of some invasive herbivorous mammals leads to the loss of N-fixing shrubs that are pioneers during primary succession. 2. We studied primary successional surfaces caused by river floods and landslides in a remote valley in New Zealand's South Island. We set up and maintained a removal experiment over 10 years, with N-fixing Carmichaelia odorata (hereafter Carmichaelia) either left intact or removed to represent the effects that invasive herbivorous mammals could cause under high densities. 3. Above-ground effects of 10 years of Carmichaelia removal included a 7-fold reduction of woody plant biomass, but had no effect on the shorter non-woody vegetation. Foliar N concentrations of two woody species were also reduced. Carmichaelia removal reduced local or a-diversity but enhanced b-diversity of the remaining vegetation at the functional group but not the species level. 4. Below-ground effects of 10 years of Carmichaelia removal included large reductions in soil carbon (C) and N levels, and biomass or abundance of several groups of soil biota occupying three consumer trophic levels as well as the root-, bacterial-and fungal-based energy channels. Invertebrate bacterial consumers were more adversely affected than were fungal consumers. Carmichaelia loss reduced a-diversity of some below-ground groups, while b-diversity was unresponsive or enhanced. 5. Synthesis. Our results reveal that loss of a single functionally distinct plant species, such as occurs through herbivore invasion, can cause substantial effects both above-ground and below-ground. This may affect the trajectory of the ecosystem over successional time, especially in primary seres that otherwise have very low soil carbon (C) and nitrogen (N) reservoirs. More generally, our results support the view that the simultaneous gains of some organisms (e.g. invasive herbivorous mammals) and resultant losses of others (e.g. palatable N-fixing plants) are a major element of humaninduced global change that may be transforming many communities and ecosystems world-wide.

Questions: Are the vegetation attributes significantly different among lava domes and among geomorphologic units as a result of age and soil features? Are the successional rates equal in all the geomorphologic units of the domes? Are the colonizer species of lava domes totally replaced by other species in the late successional stages?Location: Terceira Island, Azores (Portugal).Methods: Three comparable domes of 240, 370 and 2080 yr old were selected. Data on floristic composition, vegetation bioarea (area occupied by plant species in transects), structure, demography and soil nutrients were collected. Quantitative and qualitative changes along the succession gradient were also analyzed.Results: Vegetation attributes were consistent with the successional stage of each dome in the primary sere; however, the geomorphologic units did not follow the same pattern. The influence of the rates of plant colonization and soil formation are responsible for the decrease of the successional rates from footslopes, to summits, to slopes. The vegetation successionally changes from Juniperus scrub, to Juniperus wood and forest, and there is little species replacement since the similarity in species composition is high between the 3 domes.Conclusions: This is a special type of direct succession that takes place mainly through an increase in biomass and structural complexity. We observed small wooded areas in the fissures of very young domes that are samples of later successional forests — a phenomenon that we call ‘zoom effect’.