Pioneer Stage Research Articles

Two new pioneer communities of Sorbus aucuparia and Sorbus aria in the southern Julian Alps

Abstract In the southern Julian Alps we described two communities whose tree layer is dominated by species from the genus Sorbus and noted two successional stages in the overgrowing of abandoned agricultural land (pastures, hay meadows). In the secondary succession on former subalpine pastures above the alp Planina Razor und under the Breginjski Stol ridge, where potential natural vegetation consists of subalpine beech forest, dwarf pine has been overgrown with mountain ash (Sorbus aucuparia) whose stands are classified into the new association Rhododendro hirsuti-Sorbetum aucupariae. Whitebeam (Sorbus aria) has established itself on steep former hay meadows in the belt of altimontane beech forests under Mts. Jalovnik and Krikov Vrh, on gullied slopes on mixed geological bedrock dominated by chert, and these stands are classified into the association Calamagrostio arundinaceae-Sorbetum ariae. While occupying only small areas these two pioneer stages, as the sites of some rare or protected species, are nevertheless important biotopes and play a vital role in protection against avalanches.

Diversity of phytophagous beetles (Coleoptera: Chrysomeloidea, Curculionoidea) in steppe communities in the forest-steppe of the High Trans-Volga region

A total of 551 species from 10 families of phytophagous beetles (superfamilies Chrysomeloidea and Curculionoidea) have been recorded in the steppe communities of the High Trans-Volga forest-steppe zone, 62% of which belong to the steppe landscape-geographic complex. The vast majority of the species belong to three families: Curculionidae (254 species; 46%), Chrysomelidae (186 species; 34%), and Apionidae (51 species; 9%). The regional steppe fauna has a complex arealogical structure combining the Western Scythian and Sarmatian elements, as well as relict species of the Angarian origin and some Eastern European ones. The highest diversity of phytophagous beetles is observed in the zonal meadow steppe communities (299 species; 54%). The most specific are the petrophilous steppe complexes which also include the greatest number of relict forms. Xerophilous Kazakhstan- Turanian species are mostly concentrated in the saline steppe communities of the southernmost forest-steppe zone. The species diversity is also high (249 species) in the open ruderal communities dominated by species characteristic of the pioneer stages of the steppe successions. Some steppe reservations include over 50% of the entire regional fauna of phytophagous beetles. The species diversity in the steppe localities decreases northward due to a gradual decrease in the number and proportion of the Scythian species: from 55% in the middle of the foreststeppe zone to 36% near its northern boundary. The species diversity of the slope communities in the forest-steppe zone is at least not lower than that in the similar areas of the steppe zone. The ratio of the number of Curculionoidea species to that of plant species is very high, reaching about 3: 4 in the model steppe localities of the High Trans-Volga forest-steppes, as compared to 1: 2 in the zonal steppe communities (according to the published data). The data considered confirm the significance of the forest-steppe zone as an important biodiversity center in the East European Plain and as a reservation of relicts of different origins.

Pioneer zone geo-ecological change: Observations from a chronosequence on the Storbreen glacier foreland, Jotunheimen, southern Norway

The first 33years of primary geo-ecological succession is investigated in the pioneer zone of the Storbreen glacier foreland using the chronosequence approach. Pitfall trapping of invertebrates and the sampling of higher and lower plants and habitat factors from quadrats were used on three replicate transects across a till plain accurately dated by annually monitored glacier front variations combined with the mapping of annual moraine ridges. Unstable, saturated sediments deglacierized for <1year are colonized first by very large numbers of Collembola and a small number of epigeal beetles and spiders. Improved drainage, loss of fine matrix by pervection and frost sorting lead to the development of an active stone pavement after 6–21years, which is colonized by sparse herbaceous perennials, a slowly-developing cryptogamic crust dominated by mosses, and moderately abundant epigeal beetles, spiders and the glacier harvestman (Mitopus morio). Further soil development and stabilization of the stone pavement lead, via a transition phase (21–26years), to a fast developing ecosystem (26–33years) in which the cover of most of the plants and pitfall catches of invertebrate groups are increasing rapidly (including a resurgence in Collembola catches and the spread of Racomitrium moss, terrestrial lichens and shrubs). Spatial heterogeneity reflects gradual successional trajectories related to small variations in physical habitat conditions. The sequence of changes is summarized in a conceptual geo-ecological model in which abiotic and biotic processes combine to drive the pioneer stages of both invertebrate and plant succession with little evidence of highly integrated biotic communities.

The mechanism for exclusion of Pinus massoniana during the succession in subtropical forest ecosystems: light competition or stoichiometric homoeostasis?

Competition for light has traditionally been considered as the main mechanism for exclusion of Pinus massoniana during succession in subtropical forest ecosystems. However, both long-term inventories and a seedling cultivation experiment showed that growth of mature individuals and young seedlings of P. massoniana was not limited by available light, but was strongly influenced by stoichiometric homoeostasis. This is supported by the results of homoeostatic regulation coefficients for nitrogen (HN) and phosphorus (HP) estimated using the measured data from six transitional forests across subtropical China. Among three dominant tree species in subtropical forests, P. massoniana and Castanopsis chinensis had the lowest values of HP and HN, respectively. Therefore P. massoniana cannot survive in the advanced stage due to soil phosphorus limitation and C. chinensis cannot successfully grow in the pioneer stage due to soil nitrogen limitation. Our results support that stoichiometric homeostasis is the main reason for gradual exclusion of P. massoniana from the transitional forest and the eventual elimination from the advanced forest during the subtropical forest succession. Therefore greater attention should be paid to stoichiometric homeostasis as one of the key mechanisms for species exclusion during forest succession.

What was an interglacial river like? Sedimentological investigation of Holsteinian fluvial deposits in eastern Poland

Holsteinian fluvial deposits in the Samica River valley in eastern Poland have been studied, in an approximately 12-m-thick succession filling palaeochannels and comprising sandy channel facies succeeded by a package of gyttja, peat and silt deposited in oxbow. Channel belts including palaeochannel fills cut into outwash sands and are overlain by diamictic sands reworked by solifluction under periglacial conditions. Sedimentological and palynological investigations in combination allowed the recognition of glacial and interglacial deposits. The channel belt was formed by a typical sand-bed, meandering river with deposition controlled by abundant point bars. The sedimentary evolution of the Samica valley is interpreted in the context of the glacial-interglacial cycle. Valley-scale erosion and change of river style from braided to meandering occurred coevally with the decay of an ice sheet (deglaciation) and the main phase of meandering river sedimentation is attributed to latest Elsterian and early Holsteinian. The next part of the interglacial, from pioneer stage to established temperate conditions, is recorded in a biogenic oxbow-lake fill. The succession studied has been compared with published data on the European fluvial deposits of Middle Pleistocene interglacials. It is pointed out here that river channel patterns in western and eastern Europe differed. Based on this observation, some general hypotheses regarding the continental-scale climatic distinctness are put forward.

Community structure and diversity of vegetation and flower-visiting wild bees (Hymenoptera: Apoidea) in sandy dry grassland: are there congruent characteristics?

We studied community structures of mainly threatened types of sandy dry grassland, and those of flower-visiting wild bees, in successional, non-ruderal or ruderal gradients in the Upper Rhine Valley (Germany). We searched for congruent characteristics in the floristic/faunistic structure of plant and bee species, and for differences between two study years. We also asked which vegetation type or complex plays the most important role as a pollen or nectar resource for wild bees, and what conclusions can be drawn for nature conservation. The vegetation types or complexes range from basiphytic pioneer stages to consolidated basiphytic to slightly acidophytic grasslands (classes Koelerio-Corynephoretea and Festuco-Brom- etea): Koelerion glaucae complex (1), Armerio-Festucetum trachyphyllae (2a, typical; 2b, ruderalized), ruderalized ex-arable field (3), and Allio-Stipetum capillatae (4). We used a plot-based approach for recording vegetation data and flower-visiting wild bees. Releves were sampled and flower- visiting bees netted on defined flower resources (2004, 2005). Data were analyzed by ordination, mixed linear models and regres- sion analysis. Phytosociological table and DCA show clear floristic differentiations between the vegetation types and complexes. For the bee data there were weaker species-based differentiations. In the year 2004 there were two bee assemblages, in the year 2005 this dif- ferentiation was not detectable. The most species- and individual-rich wild-bee populations were detected in the vegetation types 2b, 3 and 4. These types were characterized by a high diversity of entomophilous plant species in combination with high flower density. Although ruderalized sandy grasslands have only moderate conservation value based on vegetation characteristics, they offer remarkable resources for species-rich populations of wild bees. Important flower resources for endangered wild-bee species are, among others, Centaurea stoebe s.l., Berteroa incana and Carduus nutans. The diversity characteristics of the studied vegetation types or complexes do not always correspond to those of the flower-visit- ing bees, which should be taken into account in developing conservation strategies.

Different pioneer plant species select specific rhizosphere bacterial communities in a high mountain environment.

The rhizobacterial communities of 29 pioneer plants belonging to 12 species were investigated in an alpine ecosystem to assess if plants from different species could select for specific rhizobacterial communities. Rhizospheres and unvegetated soils were collected from a floristic pioneer stage plot at 2,400 m a.s.l. in the forefield of Weisskugel Glacier (Matsch Valley, South Tyrol, Italy), after 160 years of glacier retreat. To allow for a culture-independent perspective, total environmental DNA was extracted from both rhizosphere and bare soil samples and analyzed by Automated Ribosomal Intergenic Spacer Analysis (ARISA) and Denaturing Gradient Gel Electrophoresis (DGGE). ARISA fingerprinting showed that rhizobacterial genetic structure was extremely different from bare soil bacterial communities while rhizobacterial communities clustered strictly together according to the plant species. Sequencing of DGGE bands showed that rhizobacterial communities were mainly composed of Acidobacteria and Proteobacteria whereas bare soil was colonized by Acidobacteria and Clostridia. UniFrac significance calculated on DGGE results confirmed the rhizosphere effect exerted by the 12 species and showed different bacterial communities (P < 0.05) associated with all the plant species. These results pointed out that specific rhizobacterial communities were selected by pioneer plants of different species in a high mountain ecosystem characterized by oligotrophic and harsh environmental conditions, during an early primary succession.

Heat tolerance of early developmental stages of glacier foreland species in the growth chamber and in the field.

In glacier forelands, seeds readily germinate, however, a high proportion of seedlings die shortly after their appearance. We hypothesized that besides drought, frost and missing safe sites, heat on the ground surface could be one of the major threats for seedlings. The heat strain in different ground strata was assessed from 2007 to 2010. The heat tolerance (LT50) of eleven alpine species from different successional stages was tested considering imbibed (G1) and germinated seeds (G2) as well as seedlings (G3). Additionally, the heat hardening capacity of seedlings was determined in the field. Across all species, LT50 decreased significantly by 9 K from G1 (55 °C) to G3 (46 °C), similarly in all species of the successional stages. Field-grown seedlings had mostly an increased LT50 (2K). Intraspecifically, LT50 of seedlings varied between 40.6 and 52.5 °C. Along the chronosequence, LT50 in G1 was similar, but was higher in G2 and G3 of early successional species. The highest temperatures occurred at 0–0.5 cm in air (mean/absolute maximum: 42.6/54.1 °C) posing a significant heat injury risk for seedlings when under water shortage transpirational cooling is prevented. Below small stones (0–0.5 cm), maxima were 4 K lower, indicating heat safer microsites. Maxima >30 °C occurred at 32.3, >40 °C at 6.2 %. Interannually, 2010 was the hottest year with heat exceeding LT50 at all microsites (0–0.5 cm). Temperature maxima on sandy surfaces were lower than on microsites with gravel (diameter <5–10 mm). The hot summer of 2010 may be a small foretaste of in future more severe and frequent heat waves. Ground surface temperature maxima at the pioneer stage are already now critical for heat survival and may partly explain the high seedling mortality recognized on recently deglaciated terrain.Electronic supplementary materialThe online version of this article (doi:10.1007/s11258-014-0361-8) contains supplementary material, which is available to authorized users.

Accumulation rates of soil organic matter in wet dune slacks on the Dutch Wadden Sea islands

A long-term monitoring program (ranging from 16 to 77 years) on the Dutch Wadden Sea Islands provided well-documented examples of vegetation succession in wet dune slacks. We used this opportunity to study soil organic matter (SOM) accumulation in relation to vegetation succession. The aim of this paper is to identify the factors which regulate accumulation rates of SOM in wet dune slacks. We used several soil chronosequences using data from the monitoring program together with data from a long-term research activity and more recent measurements. We used several soil chronosequences using data from the monitoring program together with data from a long-term research (up to 150 years) and more recent measurements. Field measurements included pH, soil organic matter, above ground standing crop and water levels. Water level regimes (inundation duration and mean minimum water level), were simulated using a hydrological model. Capable of simulating inundation duration and water-level fluctuations, this model used field measurements collected over more than 5 years, as well as precipitation and evapotranspiration data collected over a period of 25 years. Sampling two synchronic chronosequences showed that SOM accumulations increased linearly during the first 50–60 years and then levelled off. Sampling various diachronic chronosequences over time showed a wide variation in accumulation rates. Slacks with low productive species, such as Littorella uniflora, showed low accumulation rates (0.02–0.08 kg/m2/year), and persisted even over a period of more than 90 years. In contrast, slacks dominated by high productive species, such as Phragmites australis, showed ten times higher accumulation rates (0.17–0.26 kg/m2/year) over a similar time period and comparable annual inundation periods (176–240 days). A multiple linear regression showed that variation in SOM accumulation rates was best explained by above-ground biomass of the vegetation. We conclude that the rate of SOM accumulation in wet dune slacks is primarily controlled by plant above-ground biomass. Both above-ground biomass and SOM accumulation can remain very low over a long period of time when dune slacks are flooded during most of the year and plants with adaptive traits are able to maintain vegetation succession at a pioneer stage.

Polymeric nanoparticles for molecular imaging

Conventional imaging technologies (X-ray computed tomography, magnetic resonance, and optical) depend on contrast agents to visualize a target site or organ of interest. The imaging agents currently used in clinics for diagnosis suffer from disadvantages including poor target specificity and in vivo instability. Consequently, delivery of low concentrations of contrast agents to region of interest affects image quality. Therefore, it is important to selectively deliver high payload of contrast agent to obtain clinically useful images. Nanoparticles offer multifunctional capabilities to transport high concentrations of imaging probes selectively to diseased site inside the body. Polymeric nanoparticles, incorporated with contrast agents, have shown significant benefits in molecular imaging applications. These materials possess the ability to encapsulate different contrast agents within a single matrix enabling multimodal imaging possibilities. The materials can be surface conjugated to target-specific biomolecules for controlling the navigation under in vivo conditions. The versatility of this class of nanomaterials makes them an attractive platform for developing highly sensitive molecular imaging agents. The research community's progress in the area of synthesis of polymeric nanomaterials and their in vivo imaging applications has been noteworthy, but it is still in the pioneer stage of development. The challenges ahead should focus on the design and fabrication of these materials including burst release of contrasts agents, solubility, and stability issues of polymeric nanomaterials.

Intraguild predation in pioneer predator communities of alpine glacier forelands

Pioneer communities establishing themselves in the barren terrain in front of glacier forelands consist principally of predator species such as carabid beetles and lycosid spiders. The fact that so many different predators can co-inhabit an area with no apparent primary production was initially explained by allochthonous material deposited in these forelands. However, whether these populations can be sustained on allochthonous material alone is questionable and recent studies point towards this assumption to be flawed. Intraguild predation (IGP) might play an important role in these pioneer predator assemblages, especially in the very early successional stages where other prey is scarce. Here, we investigated IGP between the main predator species and their consumption of Collembola, an important autochthonous alternative prey, within a glacier foreland in the Ötztal (Austrian Alps). Multiplex PCR and stable isotope analysis were used to characterize the trophic niches in an early and late pioneer stage over 2 years. Results showed that intraguild prey was consumed by all invertebrate predators, particularly the larger carabid species. Contrary to our initial hypothesis, the DNA detection frequency of IGP prey was not significantly higher in early than in late pioneer stage, which was corroborated by the stable isotope analysis. Collembola were the most frequently detected prey in all of the predators, and the overall prey DNA detection patterns were consistent between years. Our findings show that IGP appears as a constant in these pioneer predator communities and that it remains unaffected by successional changes.

Appropriate Nutrient Economy in Phragmites australis at Different Phases of Estuarine Succession

The common reed Phragmites australis (Cav.) Trin ex Steudel – the dominant macrophytic plant species in the Kokemäenjoki River delta, western Finland – showed distinct and appropriate trends in the nutrient economy according to the previously determined successional phases of the vegetation development. The height and weight of individual aboveground shoots (ramets) decreased in the order: Pioneer stage > Mature stage > Regressing stage. The concentrations of the major nutrients nitrogen and phosphorus were determined only partly by amounts of these nutrients in the plants’ rhizospheres. The estuary is eutrophic, and the river water guarantees a continuous supply of nutrients, and thus the levels of nitrogen and phosphorus are high throughout the study area. The levels of nutrients correlated significantly with the contents of organic matter in the rhizospheres of the reed stands. On the basis of the relationships between the major nutrients’ concentrations in the leaf blades, nitrogen appeared to be the growth-limiting nutrients in the pioneer stage of succession in these estuarine habitats. The N/P-ratios in the three stages were as follows: Pioneer stage: 10.75, Mature stage: 13.59, Regressing stage: 14.67. In general, the values below 15 are considered to be nitrogen-limited. The actual levels of N and P in the leaf tissues were, however, high throughout the study. As evaluated by the concept of critical concentration, i.e. the level of a nutrient, which guarantees maximal growth potential, the habitats at all the three successional phases showed adequate level of nutrient availability for the maximal production of Phragmites. At the pioneer stage, where the rhizosphere resources of nutrients were poorest, the common reed showed an appropriate morphological adaptation. In the pioneering stands, the common reed produces considerable amounts of adventitious roots (water roots) on the underwater sections of the culms. In the pioneer stage, the average weight of the water roots was 675 mg/ramet in the fertile (flowering) shoots and 267 mg/ramet in the sterile (non-flowering) shoots, i.e. 2.6–5% of the total weight of the aboveground shoots. In the mature stage, the amount of adventitious roots was minor, but in the regressing stage – where growth enhancement and substantial flowering is essential for the future of the species – the reeds produced more adventitious roots again.

Long-term natural succession improves nitrogen storage capacity of soil on the Loess Plateau, China

Land-use change resulting from natural succession enhances the nitrogen (N) accumulation capacity of terrestrial ecosystems. To explore those factors that foster changes in soil N storage under evolving conditions of vegetation succession, a study on N storage at differing stages along a 150-year chronosequence was conducted in the Ziwuling Forest Region in the central part of the Loess Plateau, China. A principal finding was the rapid increase in N storage in the 0–60 cm soil layer, which achieves a stable value after the shrub community stage (~50–60 years), leading to the overall long-term (~150 years) accumulation of soil stored N in the post-abandonment secondary forest. Soil N accumulated mainly in the pioneer stage and showed a significant increase before the shrub community stage (P &lt; 0.05). The N storage in the 0–60 cm soil layer changed from 5.8 to 8.4 Mg ha–1 during the transition from abandoned farmland (~3–5 years) to climax community (Quercus liaotungensis Koidz forest) (~150 years). The N storage values were higher in the upper (&lt;20 cm) than the deeper soil layers (&gt;20 cm). In the topsoil (0–20 cm), N storage values showed a markedly positive correlation with soil organic carbon (SOC), total soil N and fine roots. In the deeper soil layers (20–40 and 40–60 cm) there was a correlation only with TN. Soil bulk density, soil water content and soil pH were not the determining factors behind N storage values in the topsoil (0–20 cm), although they did show negative, positive and negative correlations, respectively. In addition, they showed no consistent correlations in the lower soil layer (&lt;20 cm). The results suggest that changes to N storage values were the result of the accumulation of SOC, total N and primary productivity during the process of forest succession, and this capacity is positively related to post-abandonment forest succession on the Loess Plateau, China.

Microtopography and the Properties of Residual Peat Are Convenient Indicators for Restoration Planning of Abandoned Extracted Peatlands

AbstractThe natural recovery of vegetation on abandoned peat extraction areas lasts for decades and the result of restoration succession can be unpredictable. The aim of the study was to specify environmental factors that affect the formation of the pioneer stages of mire communities and, therefore, be helpful in the prediction of the resulting ecosystem properties. We used the national inventory data from 64 milled peatlands in Estonia, distributed over the region of 300 × 200 km. This is the first national‐scale statistical evaluation of abandoned extracted peatlands. During surveys, vascular plants, bryophytes, and residual peat properties were recorded on three microtopographic forms: flats, ditch margins, and ditches. The microtopography was the main factor distinguishing the composition of plant communities on flats and ditches, while ditch margins resembled flats. The extracted indicator species suggested two successional pathways, toward fen or raised bog community. A single indicator trait—the depth of residual peat, which combines the information about peat properties (e.g. pH, ash content, and trophicity status), predicted the plant community succession in microtopographic habitats. We suggest that peatland management plans about the cost‐efficient restoration of abandoned peat mining areas should consider properties of residual peat layer as the baseline indicator: milled peatfields with thin (&lt;2.3 m) and well‐decomposed residual peat should be restored toward fen vegetation types, whereas sites with thick (&gt;2.3 m) and less decomposed residual peat layer should be restored toward transitional mires or raised bogs. Specific methodological suggestions are provided.

Making a Green World

Collective-action problems occur when it takes inputs and efforts of multiple individuals in order to achieve joint outcomes and it is difficult to exclude beneficiaries of these actions from benefiting even if they do not contribute. Collective-action problems vary in scale from very small problems involving only a few individuals to extremely large problems involving global resources, such as atmosphere and oceans. Solving collective-action problems requires opening public and private spheres of activities ranging from small to very large so as to encourage effective problem solving. Environmental problems and challenges require a multidisciplinary and serious study. It needs an integrated approach on economy, politics, ecology, social stability, sustainability and spatial planning. Environmental policies are principal means by which societies attempt to adapt to ecological constraints, and to mediate between competing demands and values. various strategies can be adopted to make a green world like Sustainable development, Resource Conservation, Green Economy, Bio-regionalism, Ecological Citizenship, Green Democracy, Changing Lifestyles, Enegy Policies, Legislature, Voluntary Control and Green Values. Sustainable development is a huge and complex challenge at least in ethical terms. The nature of this ethical challenge may be summarized in terms of three types of obligation to which sustainable development relates: towards people who are already living, towards people who are not yet born and towards species other than humans.. The basic thrust of Resource Conservation standpoint was to restrain reckless exploitation of forests, soils, etc., characteristic of pioneer stage of modern social development by imposing ethical and legal requirements that natural resources be used wisely, meaning (in Gifford Pinchot's words)that they should be used greatest good of greatest number (of humans), as distinct from being used to profit a few, and that good should be considered in the long run, that is, in terms of a sustainable society. Most Green economists have tackled problem of scale (i.e., protection of ecological carrying capacity) by advocating (i) a range of new fiscal measures (such as resource depletion quotas and higher resource taxes and pollution charges) designed to control resource depletion and reduce material-energy throughput (ii) more comprehensive, and longer-range, environmental impact assessment and technology assessment and (iii) replacement of indiscriminate GDP statistics with an alternative index of economic progress designed to provide a more meaningful yardstick by which to measure economic well-being. Bioregionalism represents a specifically ecological rendition of contemporary movement toward break up of nation-states. It differs from separatists on ground that they demand ecological preconditions of nationhood. Environmental citizenship borrows idea of transnational citizenship from cosmopolitan tradition. Thus environmental citizenship speaks language of obligation, of common good and of global reach of citizenship relations. In these respects it takes a rather different view of human motivation to fiscal incentive strategy. It recognizes (or assumes) that people sometimes act in order to ‘do good’ as well as to try to ensure some gain for themselves.

Effect of geomorphology and nitrogen deposition on rate of vegetation succession in inland drift sands

AbstractQuestions(1) At what rate does succession take place in active and more stabilized drift sands in regions with low and high N deposition in the Netherlands? (2) What is the present composition of pioneer vegetation in active and more stabilized drift sands in regions with low and high N deposition? (3) What efforts are necessary to conserve bare sand in drift sands?LocationEight inland dunes in the Netherlands, which represent four active and four more stabilized drift sands in regions with low and high N deposition.MethodsAerial photographs from 1950, 1981, 1995 and 2007 were used to compare rates of succession from bare sand towards forest. For each site, a detailed vegetation map was made in 2007.ResultsIn all studied sites, bare sand decreased, especially in regions with high N deposition. This decline was significantly higher between 1981 and 2007 than between 1950 and 1981. The loss of bare sand did not lead to an increase of pioneer vegetation, which remained more or less stable; it led, however, to an increase of heath and forest. In active drift sands, pioneer vegetation was characterized by Corynephorus canescens and Polytrichum piliferum, while lichens, lichen‐rich grassland and Campylopus introflexus were more common in stabilized drift sands. In regions with high N deposition, the proportion of Campylopus introflexus to older pioneer stages was significantly higher, and the contribution of forest to the ‘heath/forest’ vegetation class was also higher. The calculated life span of bare sand decreased in all sites. Extrapolation of the results suggests that in the absence of restoration measures, bare sand will vanish by 2035.ConclusionsIn both active and more stabilized drift sands, a generic loss of bare sand and an increase in forest area was found. The increase was higher in regions with high N deposition. Conservation management should include the annual transformation of 43 ha of forest into bare sand in order to stop the loss of bare sand.

Unconventional hydrocarbon resources in China and the prospect of exploration and development

Based on analysis of the characteristics of unconventional hydrocarbon resources, this paper assesses the potential for unconventional hydrocarbons in China, summarizes the key technical progress in exploration and development, and discusses the prospects and developing strategies of unconventional hydrocarbons. The resources of unconventional oil and gas in China are abundant. The recoverable tight gas ranges from 8.8×1012 m3 to 12.1×1012 m3, the recoverable shale gas is from 15×1012 m3 to 25×1012 m3, the recoverable coalbed methane 10.9×1012 m3, the recoverable tight oil from 13×108 t to 14×108 t, and the recoverable shale oil 160×108 t. There is also some resource potential for oil sand. Such key techniques as the full-digital seismic exploration, low permeability and low resistivity reservoirs identification have been developed and their applications in oil and gas fields have achieved good results. Tight gas and tight oil are the most realistic resources to develop in China and the development and utilization of coalbed methane and shale gas are at a pioneer stage. In the next ten or twenty years, the production of unconventional hydrocarbon in China will increase considerably and play a major role in national hydrocarbon resources.

Shifts in plant community structure of a threatened sandy grassland over a 9‐yr period under experimentally induced nutrient regimes: is there a lag phase?

AbstractQuestionsDoes nutrient addition to nutrient‐poor pioneer grassland lead to altered successional pathways after a lag phase? Are there shifts in plant functional types with time after nutrient addition? Is phytodiversity negatively affected by a 9‐yr nutrient addition? Is succession affected by local seed availability?LocationUpper Rhine valley, Germany.MethodsA five‐fold replicated randomized block design was used for addition of phosphorus, organic carbon, nitrogen (low and high dose) or combined applications of high‐dose N with P (NP), potassium (NPK) or other essential nutrients (NPKM) for 9 yr. Seed limitation was assessed as local seed rain. Data were analysed by ordination (DCA) and linear mixed models.ResultsDCA revealed two successional pathways: one typical for sandy grassland, and another on plots with high‐dose N, which was accelerated and clearly separated from the typical one after a distinct ‘lag phase’ of about 5 yr. As a general trend, phytodiversity diminished on all plots during succession, but the decrease was significantly stronger on plots with high‐dose N, which had higher turnover ratios. Habitat‐typical species from pioneer stages (‘stress tolerators’ and ‘ruderals’) and Red Data species decreased with nutrient addition. There was an increase in cover of tall plants, geophytes and hemicryptophytes, ‘competitor/stress tolerator/ruderal’ strategists and competitive graminoids on plots with high‐dose N. Above‐ground phytomass production of phanerogams increased three‐fold, but was significantly lower for cryptogams. Litter accumulation increased five‐fold on high‐dose N plots. In contrast, low‐dose N and P plots only showed responses for legumes, predominantly facilitated by P. Seed rain consisted of autochthonous and allochthonous species, but most abundant species were non‐target species.ConclusionsCommunity structure, plant strategies and general successional trajectories of the studied system changed on plots with high‐dose N after 5 yr. A threatened vegetation type was gradually replaced by one with competitive drivers of succession. These findings emphasize the importance of long‐term observations for studying nutrient effects.

Subtropical Brazilian mangroves as a refuge of crab (Decapoda: Brachyura) diversity

This study characterized seven mangrove areas of different sizes, located on the southeastern Brazilian coast, with respect to their sediment and vegetation features. We also estimated the richness and composition of the brachyuran assemblages in these mangroves. Crab, vegetation and sediment data were collected during low tide. The larger mangroves showed richer and complex forests, and may be more ecologically stable than smaller mangroves. Twenty-eight species of crabs were recorded, members of nine families: Panopeidae, Pinnotheridae, Gecarcinidae, Grapsidae, Sesarmidae, Varunidae, Ocypodidae, Ucididae, and Portunidae. Ocypodoidea predominated over Grapsoidea in the smaller mangrove areas in pioneer stages of forest establishment, whereas the opposite was recorded for larger and more stable mangroves, where the forest can reach advanced stage of development. Comprido is a small mangrove, but its crab assemblage was similar to the larger ones, probably because of other factors not investigated here (e.g., megalopa settling rate). This study provided basic knowledge for developing conservation strategies for vulnerable mangrove ecosystems.

Vegetation Development on Deglaciated Rock Outcrops from Glaciar Frías, Argentina

The retreat of glaciers during past decades has led to the emergence of large rock outcrops in many glaciated areas around the world. Primary succession of vegetation in glacier forelands has been described for many regions, but most studies have been conducted on glacial deposits, whereas deglaciated rock outcrops have received little attention. This study assesses the pattern of primary succession on a chronosequence of five rock outcrops exposed during the past 140 years by the retreat of Glaciar Frías in the Patagonian Andes, Argentina. Data on floristic composition and species cover for algae, lichens, ferns, bryophytes, and vascular plants were recorded on sampling plots. Ordination and classification analyses discriminate three major successional stages, each dominated by a different species assemblage, suggesting directional replacement of species in the succession. The pioneer stage is dominated by the crustose lichen Placopsis perrugosa, the mid-successional stage by a lichen-moss mat dominated by the moss Racomitrium lanuginosum, and the late-successional stage by a large diversity of vascular plants. The low density of Nothofagus dombeyi saplings in the late-successional site indicates that plant succession is still in progress 140 years after deglaciation. Progress in succession appears to be influenced by species life-cycle traits and facilitative interactions among species. The comparison of the successional processes between rock outcrops and unconsolidated glacial deposits suggests that the vegetation sequence is similar, but the rate of succession is slower on rock outcrops. The development of a ground lichen-moss cover, previous to the widespread colonization by vascular plants, accounts for the slower succession progress on rock outcrops. The establishment of Nothofagus stands takes at least 100 yrs longer on the rock outcrops than on glacial deposits. Under predicted climate warming, most Patagonian Andes glaciers will continue the retreat along steep bedrock slopes, where similar, long-term vegetation successional patterns to those observed on Glaciar Frías foreland will eventually occur.