Ecological Succession

Increasingly, river managers are turning from hard engineering solutions to ecologically based restoration activities in order to improve degraded waterways. River restoration projects aim to maintain or increase ecosystem goods and services while protecting downstream and coastal ecosystems. There is growing interest in applying river restoration techniques to solve environmental problems, yet little agreement exists on what constitutes a successful river restoration effort. 2. We propose five criteria for measuring success, with emphasis on an ecological perspective. First, the design of an ecological river restoration project should be based on a specified guiding image of a more dynamic, healthy river that could exist at the site. Secondly, the river's ecological condition must be measurably improved. Thirdly, the river system must be more self-sustaining and resilient to external perturbations so that only minimal follow-up maintenance is needed. Fourthly, during the construction phase, no lasting harm should be inflicted on the ecosystem. Fifthly, both pre-and postassessment must be completed and data made publicly available. 3. Determining if these five criteria have been met for a particular project requires development of an assessment protocol. We suggest standards of evaluation for each of the five criteria and provide examples of suitable indicators. 4. Synthesis and applications . Billions of dollars are currently spent restoring streams and rivers, yet to date there are no agreed upon standards for what constitutes ecologically beneficial stream and river restoration. We propose five criteria that must be met for a river restoration project to be considered ecologically successful. It is critical that the broad restoration community, including funding agencies, practitioners and citizen restoration groups, adopt criteria for defining and assessing ecological success in restoration. Standards are needed because progress in the science and practice of river restoration has been hampered by the lack of agreed upon criteria for judging ecological success. Without well-accepted criteria that are ultimately supported by funding and implementing agencies, there is little incentive for practitioners to assess and report restoration outcomes. Improving methods and weighing the ecological benefits of various restoration approaches require organized national-level reporting systems.

During the Early Pleistocene, hominins dispersed from Africa to Eurasia via the Levant. The presence of African taxa in higher latitudes has been interpreted as indicative of an Africa savanna habitat in the Early Pleistocene of the Levant and as support for the hypothesis that the spread of grasslands into higher latitudes promoted the dispersal of hominins into Eurasia. To infer the paleoenvironment of the Levant during the Early Pleistocene, a multivariate analysis based on abundance and presence-absence data of mesoherbivores was used. Results indicate that in the Early Pleistocene, the Levant was situated in a Mediterranean woodland habitat. The presence of African taxa in novel environments may be explained using a long distance dispersal model and suggests that the spatial and temporal abundance pattern of African taxa in the Levant is consistent with the early stages of dispersal and is not indicative of the presence of savanna habitats in higher latitudes. The ecological success of hominins in higher latitudes as attested to by their widespread geographic distribution is consistent with their adaptation to novel environments and suggests that they may have been pre-adapted to variable environments.

In the final analysis, sustainable agriculture must derive from applied ecology, especially the principle of the regulation of the abundance and distribution of species (and, secondarily, their activities) in space and time. Interspecific competition in natural ecosystems has its counterparts in agriculture, designed to divert greater amounts of energy, nutrients, and water into crops. Whereas natural ecosystems select for a diversity of species in communities, recent agriculture has minimized diversity in favour of vulnerable monocultures. Such systems show intrinsically less stability and resilience to perturbations. Some kinds of crop rotation resemble ecological succession in that one crop prepares the land for successive crop production. Such rotations enhance soil organic processes such as decomposition and material cycling, build a nutrient capital to sustain later crop growth, and reduce the intensity of pest buildup. Species in natural communities occur at discrete points along the r-K continuum of reproductive maturity. Clearing forested land for agriculture, rotational burning practices, and replacing perennial grassland communities by cereal monocultures moves the agricultural community towards the r extreme. Plant breeders select for varieties which yield at an earlier age and lowerplant biomass, effectively moving a variety towards the r type. Features of more natural landscapes, such as hedgerows, may act as physical and biological adjuncts to agricultural production. They should exist as networks in agricultural lands to be most effective. Soil is of major importance in agroecosystems, and maintaining, deliberately, its vitality and resilience to agricultural perturbations is the very basis of sustainable land use.

Successional patterns, water quality changes, and effects of hydrologic pulsing are documented for a whole-ecosystem experiment involving two created wetlands that have been subjected to continuous inflow of pumped river water for more than 10 years. At the beginning of the growing season in the first year of the experiment (1994), 2400 individuals representing 13 macrophyte species were introduced to one of the wetland basins. The other basin was an unplanted control. Patterns of succession are illustrated by macrophyte community diversity and net aboveground primary productivity, soil development, water quality changes, and nutrient retention for the two basins. The planted wetland continued to be more diverse in plant cover 10 years after planting and the unplanted wetland appeared to be more productive but more susceptible to stress. Soil color and organic content continued to change after wetland creation and wetlands had robust features of hydric soils within a few years of flooding. Organic matter content in surface soils in the wetlands increased by approximately 1% per 3-year period. Plant diversity and species differences led to some differences in the basins in macrophyte productivity, carbon sequestration, water quality changes and nutrient retention. The wetlands continued to retain nitrate-nitrogen and soluble reactive phosphorus 10 years after their creation. There are some signs that sediment and total phosphorus retention are diminishing after 10 years of river flow. Preliminary results from the beginnings of a flood pulsing experiment in the two basins in 2003-2004 are described for water quality, nutrient retention, aboveground productivity, and methane and nitrous oxide gaseous fluxes.

Forest transition theory describes a reversal in land-use trends for a given area, from a period of net forest area loss, to a period of net forest area gain. Some assume that such forest gain necessarily equates with biodiversity conservation. We question this assumption, based on research conducted in Oaxaca, Mexico. In Oaxaca's northern highlands, low intensity forest use and rotational (milpa) agriculture have led to pronounced spatial heterogeneity in forest structure and composition, and created a highbiodiversity forest-agriculture mosaic. In the Zapotec community of San Juan Evangelista Analco and the Chinantec community of Santiago Comaltepec, as across much of Oaxaca, fewer people are farming; farmers are cultivating less land, working closer to settlements, and growing fewer crop varieties. Widespread agricultural abandonment has initiated unprecedented changes in ecological succession, patch size, and edge effects, which we speculate will be having an impact on the biodiversity of the landscape mosaic. Our work suggests that the decline of land use activity may result in a gradual loss of the forest-agriculture mosaic, leading to localised declines in biodiversity, despite (or because of) extensive forest resurgence. These findings support the view that indigenous cultures in Oaxaca and Mexico should not be seen as an environmental constraint but rather as an agent of landscape renewal that allows for both cultural and biological diversity to flourish, a reality that national and international conservation bodies need to more fully recognise and incorporate into policy. ß

Synopsis This article derives from a society-wide symposium organized by Timothy Bradley and Adriana Briscoe and presented at the 2009 annual meeting of the Society for Integrative and Comparative Biology in Boston, Massachusetts. David Grimaldi provided the opening presentation in which he outlined the major evolutionary events in the formation and subsequent diversification of the insect clade. This presentation was followed by speakers who detailed the evolutionary history of specific physiological and/or behavioral traits that have caused insects to be both ecologically successful and fascinating as subjects for biological study. These include a review of the evolutionary history of the insects, the origins of flight, osmoregulation, the evolution of tracheal systems, the evolution of color vision, circadian clocks, and the evolution of eusociality. These topics, as covered by the speakers, provide an overview of the pattern and timing of evolutionary diversification and specialization in the group of animals we know as insects.

After a millenarian history of overexploitation, most forests in the Mediterranean Basin have disappeared, leaving many degraded landscapes that have been recolonized by early successional shrub-dominated communities. Common reforestation techniques treat these shrubs as competitors against newly planted tree seedlings; thus shrubs are cleared before tree plantation. However, empirical studies and theory governing plantplant interactions suggest that, in stress-prone Mediterranean environments, shrubs can have a net positive effect on recruitment of other species. Between 1997 and 2001, we carried out experimental reforestations in the Sierra Nevada Protected Area (southeast Spain) with the aim of comparing the survival and growth of seedlings planted in open areas (the current reforestation technique) with seedlings planted under the canopy of preexisting shrub species. Over 18 000 seedlings of 11 woody species were planted under 16 different nurse shrubs throughout a broad geographical area. We sought to explore variation in the sign and magnitude of interactions along spatial gradients defined by altitude and aspect. In the present work, we report the results of a meta-analysis conducted with seedling survival and growth data for the first summer following planting, the most critical period for reforestation success in Mediterranean areas. The facilitative effect was consistent in all environmental situations explored (grand mean effect size d ϩ ϭ 0.89 for survival and 0.27 for growth). However, there were differences in the magnitude of the interaction, depending on the seedling species planted as well as the nurse shrub species involved. Additionally, nurse shrubs had a stronger facilitative effect on seedling survival and growth at low altitudes and sunny, drier slopes than at high altitudes or shady, wetter slopes. Facilitation in the dry years proved higher than in the one wet year. Our results show that pioneer shrubs facilitate the establishment of woody, late-successional Mediterranean species and thus can positively affect reforestation success in many different ecological settings.

The giant kelp Macrocystis is the world's largest benthic organism and most widely distributed kelp taxon, serving as the foundation for diverse and energy-rich habitats that are of great ecological and economical importance. Although the basic and applied literature on Macrocystis is extensive and multinational, studies of large Macrocystis forests in the northeastern Pacific have received the greatest attention. This review synthesises the existing Macrocystis literature into a more global perspective. During the last 20 yr, the primary literature has shifted from descriptive and experimental studies of local Macrocystis distribution, abundance and population and community structure (e.g., competition and herbivory) to comprehensive investigations of Macrocystis life history, dispersal, recruitment, physiology and broad-scale variability in population and community processes. Ample evidence now suggests that the genus is monospecific. Due to its highly variable physiology and life history, Macrocystis occupies a wide variety of environments (intertidal to 60+ m, boreal to warm temperate) and sporophytes take on a variety of morphological forms. Macrocystis sporophytes are highly responsive to environmental variability, resulting in differential population dynamics and effects of Macrocystis on its local environment. Within the large subtidal giant kelp forests of southern California, Macrocystis sporophytes live long, form extensive surface canopies that shade the substratum and dampen currents, and produce and retain copious amounts of reproductive propagules. The majority of subtidal Macrocystis populations worldwide, however, are small, narrow, fringing forests that are productive and modify environmental resources (e.g., light), yet are more dynamic than their large southern California counterparts with local recruitment probably resulting from remote propagule production. When intertidal, Macrocystis populations exhibit vegetative propagation. Growth of high-latitude Macrocystis sporophytes is seasonal, coincident with temporal variability in insolation, whereas growth at low latitudes tracks more episodic variability in nutrient delivery. Although Macrocystis habitat and energy provision varies with such ecotypic variability in morphology and productivity, the few available studies indicate that Macrocystis -associated communities are universally diverse and productive. Furthermore, temporal and spatial variability in the structure and dynamics of these systems appears to be driven by processes that regulate Macrocystis distribution, abundance and productivity, rather than the consumptive processes that make some other kelp systems vulnerable to overexploitation. This global synthesis suggests that the great plasticity in Macrocystis form and function is a key determinant of the great global ecological success of Macrocystis .

a b s t r a c t Ecological succession is described by the 2nd law of thermodynamics. According to the universal law of the maximal energy dispersal, an ecosystem evolves toward a stationary state in its surroundings by consuming free energy via diverse mechanisms. Species are the mechanisms that conduct energy down along gradients between repositories of energy which consist of populations at various thermodynamic levels. The salient characteristics of succession, growing biomass production, increasing species richness and shifting distributions of species are found as consequences of the universal quest to diminish energy density differences in least time. The analysis reveals that during succession the ecosystem's energy transduction network, i.e., the food web organizes increasingly more effective in the free energy reduction by acquiring new, more effective and abandoning old, less effective species of energy transduction. The number of species does not necessarily peak at the climax state that corresponds to the maximumentropy partition of species maximizing consumption of free energy. According to the theory of evolution by natural selection founded on statistical physics of open systems, ecological succession is one among many other evolutionary processes.

Successional patterns, water quality changes, and effects of hydrologic pulsing are documented for a whole-ecosystem experiment involving two created wetlands that have been subjected to continuous inflow of pumped river water for more than 10 years. At the beginning of the growing season in the first year of the experiment (1994), 2400 individuals representing 13 macrophyte species were introduced to one of the wetland basins. The other basin was an unplanted control. Patterns of succession are illustrated by macrophyte community diversity and net aboveground primary productivity, soil development, water quality changes, and nutrient retention for the two basins. The planted wetland continued to be more diverse in plant cover 10 years after planting and the unplanted wetland appeared to be more productive but more susceptible to stress. Soil color and organic content continued to change after wetland creation and wetlands had robust features of hydric soils within a few years of flooding. Organic matter content in surface soils in the wetlands increased by approximately 1% per 3-year period. Plant diversity and species differences led to some differences in the basins in macrophyte productivity, carbon sequestration, water quality changes and nutrient retention. The wetlands continued to retain nitrate-nitrogen and soluble reactive phosphorus 10 years after their creation. There are some signs that sediment and total phosphorus retention are diminishing after 10 years of river flow. Preliminary results from the beginnings of a flood pulsing experiment in the two basins in 2003-2004 are described for water quality, nutrient retention, aboveground productivity, and methane and nitrous oxide gaseous fluxes.

The genus Castor comprises two species: the Eurasian beaver Castor fibre , and the North American beaver Castor canadensis . Both species suffered from overexploitation, but have seen a revival since the 1920s due to increased protection and reintroduction programmes. Increases in the populations and distributions of species that are able to modify ecosystems have generated much scientific interest. Here

Wetlands are exceptional ecosystems that contribute to biodiversity and play a key role in the hydrological and carbon cycles. Knowledge of their long-term ecology is essential for a proper understanding of these valuable ecosystems. We present the application of multi-proxy analyses to a 115 cm-thick core from La Molina mire (Alto de la Espina) located in NW Iberia, with a chronology spanning since ∼500 BC. The mire is located in an area intensively mined for gold during the Roman period, and close to a water-canalization system used for mining operations at that time. Our aim was to get insights into the development of the wetland by combining palynological records of hydro-hygrophytes, non-pollen palynomorphs and geochemical analyses, supported by 14C datings and multivariate statistics. The results indicate a complex pattern of ecological succession. During the local Iron Age the wetland was minerotrophic. Since ∼20 AD it was subjected to dramatic hydrological changes due to a rise of the water-table, fluctuating between the presence of open water and phases of drawdown. Finally, by ∼745 AD, the wetland experienced a rapid evolution towards ombrotrophic conditions. High grazing pressure was detected for the last decades. The significant change occurred during Early Roman Empire seems to have been the consequence of the direct use of the wetland as a water-reservoir of the canalisation system used for gold-mining. Thus, the current nature of the mire may be the result of human impact, although multiple human- and climate-induced causes were potentially linked to the detected shifts. However, the system seems to have been resilient, successfully buffering the changes without substantial alterations of its functioning. Our investigation shows that palaeoecological research is necessary to understand modifications in the structure of wetland ecosystems, their long-term ecology and the role of human-induced changes.► We performed a multi-proxy study of a peat core sampled in a mire from NW Spain. ► The mire is located in an area extensively exploited for gold in Roman times. ► Pollen and chemical records show dramatic changes linked to water table variations. ► The evolution of the mire seems to have been coupled to human transformations. ► Long-term ecological series are crucial for proper conservation plans of wetlands.

Although ecological succession is one of the principal focuses of recent restoration ecology research, it is still unclear which factors drive this process and positively influence species richness and functional diversity. In this study we sought to elucidate how species traits and functional diversity change during forest succession, and to identify important factors that determine the species in the observed assemblages. We analyzed species richness and functional diversity of ground beetle assemblages in relation to succession on post-industrial localities after habitat deterioration caused by spoil de-position. We selected ground beetles as they are known to be sensitive to landscape changes (with a large range of responses), and their taxonomy and ecology are generally well-known. Ground beetles were sampled on the spoil heaps during the last 30 years when spontaneous succession occurred. To calculate functional diversity, we used traits related to habitat and trophic niche, i.e. food specialization, wing morphology , trophic level, and bio-indication value. Ground beetle species were found to be distributed non-randomly in the assemblages in the late phase of succession. Ordination analyses revealed that the ground beetle assemblage was significantly associated with the proportion of forested area. Environmental heterogeneity generated assemblages that contained over-dispersed species traits. Our findings indicated that environmental conditions at late successional stages supported less mobile carnivorous species. Overall, we conclude that the decline in species richness and functional diversity in the middle of the studied succession gradient indicated that the assemblages of open habitats had been replaced by species typical of forest ecosystems.

Blooms of the disaster opportunist Guembelitria species are proxies for environmental catastrophes, whether impact or volcanism, leading to severe biotic stress crises that may range from temporary exclusion of ecological specialists and generalists to mass extinctions. During the late Maastrichtian and early Danian (zones P0 and Pla), Guembelitria blooms show global distributions, but with the largest blooms (40 -80% Guembelitria) in low and middle latitudes and only minor blooms (10 -20%) in high latitudes. Late Maastrichtian Guembelitria blooms are, so far, known from the Indian Ocean and eastern Tethys. The most intense Guembelitria blooms (>60% Guembelitria) occurred in shallow continental shelf areas, slope/shelf margins and volcanic provinces of the Indian Ocean. What these environments have in common is high nutrient influx (eutrophication) either from continental runoff, upwelling along continental margins or volcanic input. At times of biotic crises, Guembelitria blooms may have spread rapidly to the exclusion of most or all other species, much like today's red tides, but with near global distributions.

After a millenarian history of overexploitation, most forests in the Mediterranean Basin have disappeared, leaving many degraded landscapes that have been recolonized by early successional shrub-dominated communities. Common reforestation techniques treat these shrubs as competitors against newly planted tree seedlings; thus shrubs are cleared before tree plantation. However, empirical studies and theory governing plantplant interactions suggest that, in stress-prone Mediterranean environments, shrubs can have a net positive effect on recruitment of other species. Between 1997 and 2001, we carried out experimental reforestations in the Sierra Nevada Protected Area (southeast Spain) with the aim of comparing the survival and growth of seedlings planted in open areas (the current reforestation technique) with seedlings planted under the canopy of preexisting shrub species. Over 18 000 seedlings of 11 woody species were planted under 16 different nurse shrubs throughout a broad geographical area. We sought to explore variation in the sign and magnitude of interactions along spatial gradients defined by altitude and aspect. In the present work, we report the results of a meta-analysis conducted with seedling survival and growth data for the first summer following planting, the most critical period for reforestation success in Mediterranean areas. The facilitative effect was consistent in all environmental situations explored (grand mean effect size d ϩ ϭ 0.89 for survival and 0.27 for growth). However, there were differences in the magnitude of the interaction, depending on the seedling species planted as well as the nurse shrub species involved. Additionally, nurse shrubs had a stronger facilitative effect on seedling survival and growth at low altitudes and sunny, drier slopes than at high altitudes or shady, wetter slopes. Facilitation in the dry years proved higher than in the one wet year. Our results show that pioneer shrubs facilitate the establishment of woody, late-successional Mediterranean species and thus can positively affect reforestation success in many different ecological settings.

The present study compares the soil chemical properties of a new burnt site and an old burnt site, which had experienced three and one ®re(s) respectively since 1988. The new burnt site is presently reduced to grassland and the old burnt site to mixed grassland/scrubland. Repeated ®res raised soil pH by 0.27±0.33 units, exchangeable H and K the old burnt site. Fire similarly reduced the effective cation exchange capacity (ECEC) and the base saturation by 85% and 90%, respectively. The occurrence of successive ®res is therefore hazardous to the environment and in the absence of ®re for 6 years the old burnt site has accumulated suf®cient organic matter and nitrogen needed for the invasion of the more nutrient-demanding tree species. The selection of tree species and site preparation pertaining to enhancement planting of the ®re-disturbed slopes to accelerate forest development are discussed. #

Los estudios ecológicos demuestran que los sistemas agroforestales y los barbechos de la roza, tumba y quema sirven como hábitats para la vida silvestre, como corredores entre parches de bosque y como escudos contra los efectos de borde, tales como temperaturas extremas, desecación e incendios. Además, los bosques se recuperan mucho más rápidamente después de la agricultura migratoria que tras la ganadería o los monocultivos de altos insumos. Sin embargo, los agricultores migratorios son percibidos como la amenaza principal contra la Reserva de la Biosfera Maya. En un afán por mejorar las condiciones de vida de los pequeños agricultores y a la vez proteger los bosques, algunos grupos conservacionistas están promoviendo prácticas que permitan a los agricultores producir más alimentos e ingresos con menos área cultivada.

A revival in the concept of sustainability is appreciated as Earth's human population continues to increase and its related global concerns in disease ecology, energy resource management, environmental literacy, food production, genetic diversity, and landscape vitality continue to magnify. Sustain is defined within this paper as to keep in existence or to supply with resources or necessities to prevent from falling below a given threshold of health or vitality. Barrett et al. (Bioscience 47:531-535, 1997) illustrated how seven (7) processes (behaviour, development, diversity, energetics, evolution, integration, regulation) transcend eleven (11) levels of ecological organization, ranging from the ecosphere to the cellular. Comprehension of how these processes transcend all levels of ecological organization allow programs and initiatives (e.g. preserving biotic diversity) to be defined by informed incentive, rather than regulatory mandate, within societal systems. We describe how the integration of an eighth transcending process-aesthetics-is essential in the approach to and managing of market and nonmarket capital necessary in sustaining societies.

Insects are major components of forest ecosystems, representing most of the biological diversity and affecting virtually all processes and uses. In the USA, bark beetles (Coleoptera: Curculionidae, Scolytinae) heavily influence the structure and function of these ecosystems by regulating certain aspects of primary production, nutrient cycling, ecological succession and the size, distribution and abundance of forest trees. The purpose of this report is to review tree and stand factors associated with bark beetle infestations and analyze the effectiveness of vegetation management practices for mitigating the negative impacts of bark beetles on forest ecosystems. We describe the current state of our knowledge and identify gaps for making informed decisions on proposed silvicultural treatments. This review draws from examination of 498 scientific publications (many of which are cited herein) on this and related topics. #

Substantial nitrogen (N) retention by temperate terrestrial ecosystems results from the rapid storage of newly-deposited N in stable soil organic matter. Yet, we poorly understand the ecosystem properties that regulate the kinetics of this process. We applied mineral 15N to temperate hardwood forest soils to test the hypothesis that N stabilization is faster owing to greater stocks of soil carbon (C) in late-successional than in young forests. Within 26 minutes of addition, about 30% of tracer N was stored in stable form in organic-horizon soil with a median residence time of >29 years. About 5-10% of tracer N was stored in a soluble organic form. An additional 30% of tracer N was recovered within hours from organic-horizon soils in a remineralizable (labile) form, apparently derived from microbial biomass. Over the following year, tracer N storage in stable and soluble organic pools remained constant while recovery from labile and microbial pools declined. Tracer storage was greater in older forests with larger soil C pools, supporting our hypothesis that the accumulation of soil C with forest succession promotes ecosystem N retention. Rapid storage of stable soil N in the O horizon may create a source for chronic dissolved organic N losses from watersheds.

Patterns of benthic colonization and succession were investigated on a temperate rocky cliff (Aegean Sea, Eastern Mediterranean). Cement and ceramic panels deployed on the rocky substratum at 25-30 m depth were sampled every 3 months over a 2-year period yielding 28 floral and 156 animal species. Diversity, cover and abundance had low values at short immersion periods and increased at the long ones. The vagile fauna responded to the increasing habitat complexity offered by the development of algal turfs and sessile species, and the community structure remained highly dynamic. Unlike the duration of immersion, the type of substratum didn't affect species colonization except for decapods that showed a preference for cement panels. Three to four stages of succession were recorded over immersion periods, according to vagile and sessile biota, respectively, during which species richness and abundance increased. The structure of the developed communities on both artificial materials differed from the natural algal-dominated benthic community of the same area, suggesting that the recovery of rocky shore communities on temperate cliffs is time consuming.

1] Northern peatlands are significant stocks of terrestrial soil carbon, and it has been predicted that warmer temperatures and lower water tables resulting from climate change will convert these ecosystems into sources for atmospheric carbon dioxide (CO 2 ). However, these predictions do not consider the potential for hydrologically induced ecological succession or the spatial variability of carbon accumulation rates between different microforms in peatlands. To address these issues, the vegetation community was described, and the rates of gross ecosystem photosynthesis (GEP), ecosystem respiration (R tot ) and net ecosystem CO 2 exchange were determined along poor fen microtopographic gradients at a control site and at a site which experienced a water table drawdown of $20 cm 8 years prior to the study (drained). Sampling plots within these sites were classified as microforms of hummocks, lawns, or hollows. The coverage of Sphagnum moss declined on drained hummocks, drained lawns were invaded by sedges, and hollows shifted from open water plots at the control site to Sphagnum-dominated plots with sparse vascular plant cover at the drained site. As a result, R tot was significantly greater at the drained site at all microforms while maximum rates of GEP declined at drained hummocks and were enhanced at drained lawns and hollows compared to similar control microforms. These results suggest that predictions about the response of northern peatland carbon exchange to climate change must consider the interaction between ecology and hydrology and the differential responses of microforms related to their initial ecohydrological conditions. Citation: Strack, M., J. M. Waddington, L. Rochefort, and E.-S. Tuittila (2006), Response of vegetation and net ecosystem carbon dioxide exchange at different peatland microforms following water table drawdown,

Polar seaweeds are strongly adapted to the low temperatures of their environment, Antarctic species more strongly than Arctic species due to the longer cold water history of the Antarctic region. By reason of the strong isolation of the Southern Ocean the Antarctic marine flora is characterized by a high degree of endemism, whereas in the Arctic only few endemic species have been found so far. All polar species are strongly shade adapted and their phenology is finely tuned to the strong seasonal changes of the light conditions. The paper summarises the present knowledge of seaweeds from both polar regions with regard to the following topics: the history of seaweed research in polar regions; the environment of seaweeds in polar waters; biodiversity, biogeographical relationships and vertical distribution of Arctic and Antarctic seaweeds; life histories and physiological thallus anatomy; temperature demands and geographical distribution; light demands and depth zonation; the effect of salinity, temperature and desiccation on supraand eulittoral seaweeds; seasonality of reproduction and the physiological characteristics of C. Wiencke (&) AE U. H. Lü der microscopic developmental stages; seasonal growth and photosynthesis; elemental and nutritional contents and chemical and physical defences against herbivory. We present evidence to show that specific characteristics and adaptations in polar seaweeds help to explain their ecological success under environmentally extreme conditions. In conclusion, as a perspective and guide for future research we draw attention to many remaining gaps in knowledge.

Livestock grazing Metapopulation viability Nature reserve management A B S T R A C T Management of semi-natural open ecosystems has become a necessity for biodiversity conservation in Europe. However, management methods are most often experience-based, rather than science-based. Here, we explore the impact of extensive (light) grazing, which is often the only practical management solution to stop ecological succession towards forest.

We assessed earthworm species composition and abundance during secondary succession at the Smithsonian Environmental Research Center, Maryland, USA. Land use history is well known at this site. Adjacent forest stands of different ages and other vegetation patches were sampled in 1998e99 and in 2006. Out of the 12 species three (Eisenoides loennbergi, Bimastos palustris, Diplocardia caroliniana) were native, the rest were European peregrine earthworms. Native species were mainly found in mature forests, otherwise the species composition of mature and successional stands was similar. Earthworm density and biomass was significantly higher in the successional forests, than in the mature forests, and this pattern appears to be stable at a decadal time scale. Two smaller stands that have never been clearcut did not harbor any earthworms. The forest floor on these sites had a thick organic layer, moder humus and low pH. Bulk density was highest in the youngest (50e70 years) forests. It appears that as the forests enter to a late successional stage (150 years), they no longer can support high abundance of litter feeding earthworms.

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 this study we report similar biotic response patterns in planktic foraminiferal assemblages, whether in association with volcanism, impacts or climate change at the end of the Cretaceous and early Tertiary. During and after each type of catastrophe two groups dominate high stress assemblages: (1) the small Guembelitria species, which are interpreted as having thrived in eutrophic surface waters where other species rarely survived; and (2) the low oxygen tolerant small Heterohelix species, which thrived at times of an expanding oxygen minimum zone associated with high nutrients and a stratified water column.

Community succession is an important process in modulating the structure of benthic soft-bottom communities. A field experiment was conducted aiming (1) to describe the successional development in a subtidal soft-bottom community over a two-year period, (2) to estimate the time necessary for the developing community to resemble the surrounding natural community, and (3) to evaluate the effect of seasonal onset

Marx called a social pattern "contradictory" if the conditions of its maintenance are also key ingredients for its demise. The science of ecology, too, studies patterns the conditions for whose maintenance are also key ingredients for their demise. The historical materialist notion of contradiction has a close counterpart in the ecological notion of succession. Succession is a process by which the structure of a biological community --both niche structure and species structure --changes as a result of each species' modification of the habitat. Just by living, each species member alters its environment, and in non-climax communities these effects, summed over all living things, constitute disequilibria. The habitat changes, and with it the niche structure. Gradually the species structure of the community changes. Each seral stage, with its distinctive species structure, requires for its maintenance the ongoing existence of living members of each species in the structure; yet this condition is the key ingredient for succession, for the demise of the seral stage.

Growth of fouling organisms on suspended fish cages is an impediment to aquaculture projects in coastal waters around the world. The present study characterized ecological succession of fouling communities on the netting of fish cages at an open ocean aquaculture site 10 km east of New Hampshire, USA in the western Gulf of Maine. Ecological succession can be defined as the process by which a community moves from a simple level of organization to a more complex community. Routine cleaning of the cages causes loss of organisms and initiation of ecological succession. Experimental panels of nylon net material were deployed at different times of the year and for different durations from September 2002 to September 2003 (eleven sets of 1-month panels, four sets of 3-month panels, two sets of 6-month panels, and one set of 1-year panels), with four replicates of each deployment. Panels were randomly arranged on a grid that was attached to a fish cage at a water depth of ∼15 m. There were substantial and significant differences in density and biomass of the total communities of most successional sequences when comparing panels deployed during May-September to those deployed during the cooler months, October-April. However, the blue mussel, Mytilus edulis, dominated in density and biomass in almost every sequence, regardless of time of initiation or duration. Other species that occurred in high numbers and/or biomass were the amphipods Caprella sp. and Jassa marmorata, the molluscs Hiatella arctica and Anomia sp., the seastar Asterias vulgaris, and the anemone Metridium senile. Juveniles and adults of some species were also present in some early (1-month) successional sequences, indicating that migration may be an important process in community development. Some of the dominant species listed above were present in all successional stages (early, intermediate and late), differing only in relative abundances in the community. The consistent dominance of M. edulis, and other differences in successional patterns compared to what has been typically observed for epifaunal communities in the region, were hypothesized to be the result of a combination of factors: a lack of predators such as seastars and fish that typically consume mussels in natural communities, excessive predation by nudibranchs on those species (e.g., Tubularia sp.) normally abundant in early successional stages, year-round availability of mussel larvae, and cage cleaning protocols that do not remove all the organisms present. The introduction of predatory fishes or seastars into or onto the cages might provide some amount of control on the growth of fouling organisms.

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.

Landslides have long been overlooked or underestimated as important natural disturbance agents. In particular the ecological role of landslides in maintaining biological diversity has been largely ignored. Here we provide a western Canadian (British Columbian) perspective on the influences of landslides on biophysical diversity, which is related in several ways to biological diversity. We recognize several types of biophysical/ecological diversity: site diversity, soil diversity, and the derivative habitat or ecosystem (including aquatic ecosystems) diversity. There are also a variety of landslide types, depending on materials and on the rate and style of movement. We discuss the roles of different landslide types on various aspects of terrestrial diversity. Landslides are simultaneously depositional and erosional processes that influence sites by redistributing materials and changing surface expressionusually creating a complex microtopography that can include very dry ridges and hummocks, and sometimes depressions with standing water. Landslide impacts to site also influence soil and soil development. Portions of landslides with exposed parent material are set back to the initial stages of soil development and ecological succession. Landslides can also change soil density, structure, porosity, surface texture, chemistry and microclimate. By changing site and soil, landslides also influence habitat. Landslides influence habitat diversity by engendering a mosaic of seral stages (often both primary and secondary), and in overwhelmingly forested landscapes often create nodes or hotspots of non-forested habitat and biota. In some areas, like the boreal forest, there is an important interplay between landslides and fire, while on the coast of British Columbia debris and snow avalanches can be the dominant disturbance agent. Low-gradient and deep-seated landslides are often opportunistically colonized by beaver and other water and shrub-loving fauna. Sag ponds and impounded streams provide aquatic habitatoften with standing dead trees. Landslide rubble and scarps provide denning/nesting habitat, escape terrain, and cliff habitat for vertebrates.

Abstrak Pulau-pulau Krakatau memiliki dinamika secara geomorfologi, dan berbagai perubahan fisik yang berlangsung memberikan dampak terhadap biota, termasuk pada proses dan tingkat pergantian suksesi komunitasnya. Tujuan penelitian ini untuk menjelaskan kondisi terkini dan proses kolonisasi komunitas karang, termasuk status kerusakan komunitas karang dan disturbansi lingkungan yang mempengaruhinya. Line intercept transect dilakukan di enam stasiun pada dua kedalaman yang berbeda yakni 5 dan 10m. Sedangkan observasi terhadap komunitas koral dilakukan dengan perekaman video. Hasil penelitian ini menunjukkan bahwa suksesi atau perkembangan komunitas (i.e. kolonisasi) karang yang dijumpai di Pulau Anak Krakatau masih mengindikasikan tahap awal kolonisasi, berbeda dengan komunitas karang yang dijumpai di Pulau Rakata dan Panjang. Diversifikasi komunitas karang di kedua pulau tersebut, menunjukkan dominansi spesies oportunis dan pioner (i.e. Pocillopora dan Seriatopora) yang umum dijumpai di Anak Krakatau sudah tergantikan. Dominansi dari beberapa spesies karang telah mengindikasikan terjadinya proses eksklusi kompetitif di antara komunitas karang. Tiga tipe komunitas karang yang dijumpai dapat dibedakan menurut karakteristik masing-masing kawasan, yaitu komunitas kawasan terpapar, semi terpapar/terlindung, dan terlindung. Kerusakan komunitas karang di Krakatau berdasarkan kriteria indeks kerusakan karang (CDI) sudah termasuk kedalam kategori wilayah "hot spot", dimana sangat memerlukan perhatian, pengawasan, pengamatan atau restorasi komunitas karang. Hasil dari penelitian ini memberikan gambaran bahwa terjadinya kolonisasi dan tingkat kerusakan komunitas karang perlu menjadi acuan dalam pengelolaan kawasan terumbu karang di Cagar Alam Laut Krakatau.

In the final analysis, sustainable agriculture must derive from applied ecology, especially the principle of the regulation of the abundance and distribution of species (and, secondarily, their activities) in space and time. Interspecific competition in natural ecosystems has its counterparts in agriculture, designed to divert greater amounts of energy, nutrients, and water into crops. Whereas natural ecosystems select for a diversity of species in communities, recent agriculture has minimized diversity in favour of vulnerable monocultures. Such systems show intrinsically less stability and resilience to perturbations. Some kinds of crop rotation resemble ecological succession in that one crop prepares the land for successive crop production. Such rotations enhance soil organic processes such as decomposition and material cycling, build a nutrient capital to sustain later crop growth, and reduce the intensity of pest buildup. Species in natural communities occur at discrete points along the r-K continuum of reproductive maturity. Clearing forested land for agriculture, rotational burning practices, and replacing perennial grassland communities by cereal monocultures moves the agricultural community towards the r extreme. Plant breeders select for varieties which yield at an earlier age and lowerplant biomass, effectively moving a variety towards the r type. Features of more natural landscapes, such as hedgerows, may act as physical and biological adjuncts to agricultural production. They should exist as networks in agricultural lands to be most effective. Soil is of major importance in agroecosystems, and maintaining, deliberately, its vitality and resilience to agricultural perturbations is the very basis of sustainable land use.

The Mediterranean area of Southern Italy is characterized by different natural plant covers that mainly reflect different successional stages (i.e. low maquis, high maquis, Quercus ilex wood) and managed areas with introduced plant species (such as Pinus species). Soil properties could be affected by plant cover types as well as by plant species. Our objective was to determine the relationships of plant cover types and plant species with the chemical and biological characteristics of the soil. In four neighbouring areas with different plant cover types (low maquis, pure high maquis, high maquis with pines and pinewood, with pines planted by foresters in both cases), soil samples were collected under different plant species in order to evaluate the effect of plant cover types and plant species on soil properties. Soil samples were analyzed for nutrient content, microbial biomass, soil potential respiration and enzymatic activity (phosphatase, arylsulphatase, bglucosidase and hydrolase activities) as well as for pH, water holding capacity (WHC) and cation exchange capacity (CEC). Application of cluster analysis and principal component analysis to the data revealed that the plant cover type was the key factor influencing soil properties more than plant species. In fact, the largest differences were observed between pure high maquis soils and all other soils, with pure high maquis soils generally showing the highest values of WHC, CEC, nutrient content, organic and microbial C, soil respiration, phosphatase, arylsulphatase and b-glucosidase activities. The significantly lower values of these variables in the low maquis relative to the pure high maquis probably reflect the effect of ecological succession on soil. The high maquis with pine, differing from the pure high maquis only for the presence or absence of pine, showed values of soil physical, chemical and biological characteristics similar to those found in the low maquis, thus suggesting that the presence of pine retards soil development. q

We view Digital Ecosystems to be the digital counterparts of biological ecosystems. Here, we are concerned with the creation of these Digital Ecosystems, exploiting the self-organising properties of biological ecosystems to evolve high-level software applications. Therefore, we created the Digital Ecosystem, a novel optimisation technique inspired by biological ecosystems, where the optimisation works at two levels: a first optimisation, migration of agents which are distributed in a decentralised peer-to-peer network, operating continuously in time; this process feeds a second optimisation based on evolutionary computing that operates locally on single peers and is aimed at finding solutions to satisfy locally relevant constraints. The Digital Ecosystem was then measured experimentally through simulations, with measures originating from theoretical ecology, evaluating its likeness to biological ecosystems. This included its responsiveness to requests for applications from the user base, as a measure of the ecological succession (ecosystem maturity). Overall, we have advanced the understanding of Digital Ecosystems, creating Ecosystem-Oriented Architectures (EOA) where the word ecosystem is more than just a metaphor.

The effects of artificial ultraviolet radiation [UVR; 8 W m -2 ultraviolet-A (UVA), 0.4 W m -2 ultraviolet-B (UVB)] on photosynthetic performance, growth and the capability to synthesise mycosporinelike amino acids (MAAs) was investigated in the aeroterrestrial green algae Stichococcus sp. and Chlorella luteoviridis forming biofilms on building facades, and compared with the responses of two green algae, from soil (Myrmecia incisa) and brackish water (Desmodesmus subspicatus). All species exhibited decreasing quantum efficiency (F v /F m ) after 1-3 days exposure to UVR. After 8-12 days treatment, however, all aeroterrestrial isolates exhibited full recovery under UVA and UVA/B. In contrast, D. subspicatus showed only 80% recovery after treatment with UVB. While Stichococcus sp. and C. luteoviridis exhibited a broad tolerance in growth under all radiation conditions tested, M. incisa showed a significant decrease in growth rate after exposure to UVA and UVA/B. Similarly D. subspicatus grew with a reduced rate under UVA, but UVA/B led to full inhibition. Using HPLC, an UVabsorbing MAA (324 nm-MAA) was identified in Stichococcus sp. and C. luteoviridis. While M. incisa contained a specific 322 nm-MAA, D. subspicatus lacked any trace of such compounds. UV-exposure experiments indicated that all MAA-containing species are capable of synthesizing and accumulating these compounds, thus supporting their function as an UVsunscreen. All data well explain the conspicuous eco-logical success of aeroterrestrial green algae in biofilms on facades. Biosynthesis and accumulation of MAAs under UVR seem to result in a reduced UV-sensitivity of growth and photosynthesis, which consequently may enhance survival in the environmentally harsh habitat.

How animals are distributed in the world's largest surface environment, the deep sea, is poorly understood. The ANDEEP (ANtarctic benthic DEEP-sea biodiversity, colonisation history and recent community patterns) III cruise probed richness and abundance of one group, peracarid crustaceans (isopods, amphipods, cumaceans, tanaidaceans, mysidaceans), as a model of deep-sea fauna across Southern Ocean (SO) sites. Analysis of samples from the ANDEEP cruises reveals SO isopods to be highly abundant, rich and endemic as many other taxa in the region are known to be. Samples taken across three spatial scales include sites tens, hundreds and thousands of kilometers apart, sites stretching from the Southern Cape Basin (South Atlantic) to continental Antarctica and including depths from 1030 to 5000 m. Across these spatial scales we investigated ecological success (abundance) of peracarids at order, family, and species levels. Remarkably no significant relationship was found between abundance and spatial scale at any taxonomic level. That is, the variability in abundance at major regional scale is no different to that across just tens of kilometres. Most taxa were represented in only a few samples, but we suggest most inhabitants of the deep Weddell Sea environment to be very patchy rather than rare. Separate plots of family, genus, and species abundance by sample number revealed this to be true-nearly all genera and species are an order of magnitude more abundant than 'background' levels in just one or two samples. Our isopod and amphipod samples reveal the Atlantic sector of the SO, one of the most dynamic and important regions influencing the global deep-sea environment, to be highly complex. Our study suggests that, at least with regard to the study taxa and area, the typical comparisons of regions that are made by ecologists miss the scale at which crucial ecological variability happens. Even without ice scours creating topographical complexity (as on the shelf) the deep Weddell Sea is clearly complex at scales smaller than that measured to date. r