Period Of Dominance Research Articles

How to Enjoy a Teetotal All-Night Party: Abstinence and Identity at the Sakha People’s Yhyakh

This paper exploits the interconnections between alcohol use and politics, to examine changing forms of Sakha identification in the Sakha people’s northeast Siberian Republic, Sakha (Yakutia). The Sakha people are an indigenous Siberian community; their territories have been under Russian administration since the early seventeenth century. The public event that is this paper’s main focus – the Yhyakh – is a shamanic ritual, which has come to be regarded as a quintessential traditional Sakha practice. Like many other non-Russian communities across the Soviet Union, the Sakha people have been experiencing a cultural revival, in the wake of an intensive attempt at cultural homogenisation during the Soviet era. Moderate Sakha nationalist politicians enjoyed a heady period of political dominance during the 1990s, which ceased with the advent of the Putin administrations. The Sakha people have since then watched the political and economic power of the Sakha nationalist movement fade into nothing, as the central government in Moscow has re-asserted its dominance over the Russian Federation’s subject regions. This brief examination of alcohol consumption at the Yhyakh reveals the emergence of new conventions and discussions surrounding pleasure-seeking, physical discipline, and ethnic identification. It shows how the Sakha identification for many has become integrated into projects of personal reformation, as part of a broader acceptance of the Sakha national revival and its aims. The Yhyakh has become a fulcrum for the physical, spiritual and moral aspirations of a nationalist movement that can no longer exert a political influence, but is nonetheless capable of shaping aesthetic and moral values, and physical practice. keywords: alcohol use, cultural revitalisation, post-Soviet identification, Sakha culture, shamanism, Siberia

Cyanobacterial dynamics in shallow Lake Apopka (Florida, U.S.A.) before and after the shift from a macrophyte‐dominated to a phytoplankton‐dominated state

Summary Paleolimnological data were used to reconstruct the primary producer history of shallow, hyper‐eutrophic Lake Apopka, Florida, U.S.A. Lake Apopka changed from a macrophyte‐dominated state to a phytoplankton‐dominated state in 1947. It has remained phytoplankton‐dominated despite efforts to re‐establish clear‐water conditions and submersed aquatic plants. Photosynthetic pigments, organic matter and nutrients (C, N, P) were analysed in a 4.28‐m sediment core that spans the past c. 8000 years. Our objectives were to: (i) reconstruct the primary producer history of Lake Apopka throughout its c. 8000‐year existence, (ii) determine whether the cyanobacterial dominance established in 1947 in Lake Apopka is the only period of cyanobacterial dominance in the lake's history and (iii) relate changes in the cyanobacterial community to known human impacts and recent management efforts. Lake Apopka possessed a macrophyte‐dominated primary producer community throughout most of its Holocene history, with diatoms, green algae and some cyanobacteria characterising the non‐macrophyte, primary producer component of the community. Since 1947, however, higher plants have been virtually absent in the lake and cyanobacteria have dominated the primary producer community, marking the first time that cyanobacteria have played such an important role in the lake. The cyanobacterial community itself has undergone multiple changes since 1947, confounding management efforts that have focused on a single driver of the primary producer community, that is phosphorus.

Ultrastructural study of human ampullary endosalpinx in different stages of ovarian cycle

IntroductionEfficient tubal transportation of gamete and embryo is essential for successful pregnancy. Tubal pathologies are among the leading causes of ectopic pregnancy and infertility. Scanning electron microscopy [SEM] was used to study the luminal surface morphology of the ampullary part of human Fallopian tube, paying particular attention to the different changes occurring with the progression of ovarian cycle. MethodsThe tubal samples were prepared from 15 women of different stages of ovulatory cycle, undergoing bilateral tubectomy operation for sterilization. After proper processing, the samples were examined under SEM. ResultsThe results demonstrated that, in the free luminal surface of Fallopian tube there were presence of both ciliated and nonciliated cells. In both of these cell types, obvious structural and quantitative cyclical changes were detected during different stages of ovarian cycle. In the follicular phase the ciliated cells were abundant and there was gradual increase in the cilia length. In this phase the nonciliated cells also progressively increased in height to reach their maximal height in the periovulatory period. Subsequently, as the cycle advanced towards the end of luteal phase, both the cell types reduced in height and there was partial deciliation. DiscussionPrimed by a period of estrogen dominance at ovulation and a subsequent shift to progestogen dominance with permissive estrogenic action, the endometrial epithelium undergoes the structural and physiological changes necessary for blastocyst attachment and implantation in utero.

Shifting regimes and changing interactions in the Lake Washington, U.S.A., plankton community from 1962-1994.

Understanding how changing climate, nutrient regimes, and invasive species shift food web structure is critically important in ecology. Most analytical approaches, however, assume static species interactions and environmental effects across time. Therefore, we applied multivariate autoregressive (MAR) models in a moving window context to test for shifting plankton community interactions and effects of environmental variables on plankton abundance in Lake Washington, U.S.A. from 1962–1994, following reduced nutrient loading in the 1960s and the rise of Daphnia in the 1970s. The moving-window MAR (mwMAR) approach showed shifts in the strengths of interactions between Daphnia, a dominant grazer, and other plankton taxa between a high nutrient, Oscillatoria-dominated regime and a low nutrient, Daphnia-dominated regime. The approach also highlighted the inhibiting influence of the cyanobacterium Oscillatoria on other plankton taxa in the community. Overall community stability was lowest during the period of elevated nutrient loading and Oscillatoria dominance. Despite recent warming of the lake, we found no evidence that anomalous temperatures impacted plankton abundance. Our results suggest mwMAR modeling is a useful approach that can be applied across diverse ecosystems, when questions involve shifting relationships within food webs, and among species and abiotic drivers.

Time Varying Ratings in Association Football: the All-Time Greatest Team is..

SummaryWe present a new methodology to estimate time varying team strengths of football teams. Our dynamic model allows for deterministic, rather than stochastic, evolution of team strengths. We use the model to identify the best team in England since the English Football Association was formed and match results were recorded in 1888. Our results suggest that Chelsea in 2007 were stronger than any other team has been but that Manchester United have experienced the period of most dominance.

Palynological records from two cores in the Gongpoquan Basin, central East Asia: Evidence for floristic and climatic change during the Late Jurassic to Early Cretaceous

Current understanding of late Mesozoic greenhouse climates is mainly based on palaeoclimatic information from oceanic and coastal marine sedimentary rocks. In contrast, detailed information on the climatic evolution of continental interiors is comparatively rare. This study presents a palynomorph record based on two cores drilled in the Gongpoquan Basin of northwest China located in central Asia during Late Jurassic to Early Cretaceous times. Based on these palynomorph records (G2709 and K705 successions), a total of three stratigraphic sequences with long depositional gaps can be distinguished, consisting of the Lower Jurassic Shazaohe Formation, the Lower Cretaceous (Berriasian to Valanginian) Laoshuwo Group and the Lower Cretaceous (Aptian to Albian) Laoshuwo Group. The palynomorph data provides information on prominent changes of vegetation and climate during the late Mesozoic. During Oxfordian times, spore-producing ferns show a short-lived increase, followed by a long-lasting period of Classopollis dominance during the Late Jurassic, which points to the establishment of continuously dry and warm conditions. In contrast, a more humid and probably warmer climate is indicated by the composition and high diversity of the palynoflora in the Early Cretaceous (Berriasian to Valanginian). Comparison with palynofloras of the same age from other continental basins of northwest China shows a similar vegetation change from Late Jurassic Cheirolepidiaceae-dominated forests to Early Cretaceous mixed forests composed of conifers (including Taxodiaceae and Pinaceae), cycads and pteridophytes.

O protocolo hormonal ovsynch e suas modificações em vacas leiteiras de alta produção: uma revisão

A eficiência reprodutiva em vacas leiteiras de alta produção representa atualmente um dos maiores desafios para a viabilidade das explorações. O presente trabalho teve como objetivo reportar as modificações dos protocolos de indução ovulatória baseados na administração programada de prostaglandina F2α (PGF 2α) entre duas aplicações de hormona libertadora de gonadotrofina (GnRH ), seguida da inseminação artificial em tempo fixo (IATF ). Tendo por base o protocolo hormonal Ovsynch, novos protocolos foram desenvolvidos tentando aumentar a sua eficiência reprodutiva, seguindo diferentes estratégias: (1) manipulação dos padrões de desenvolvimento folicular antes da GnRH -1, (2) otimização do ambiente hormonal peri-ovulatório, (3) otimização do intervalo de tempo entre a PGF 2α e a GnRH -2 e o momento da IA após a GnRH -2, (4) suplementação com progesterona antes da IATF , (5) redução do período de dominância folicular e aumento do proestro, e (6) controlo do crescimento folicular após a IATF . As modificações do protocolo Ovsynch permitiram a manutenção da taxa fertilidade à 1ª inseminação, até aproximadamente 40 %, quando comparada com inseminações realizadas após deteção do cio natural, com a consequente melhoria da gestão reprodutiva das manadas. As pesquisas futuras deste tipo de protocolos de indução ovulatória deverão dar enfase a aspetos nutricionais e de produção leiteira das vacas assim como ao stresse térmico em países de zonas mediterrânicas, subtropicais e tropicais.

Flooding dynamics on the lower Amazon floodplain: 2. Seasonal and interannual hydrological variability

[1] We analyzed seasonal and interannual variability in hydrological fluxes and inundation dynamics of a large floodplain unit (2440 km2) along the lower Amazon River over a period of 15 years (1995–2010). Floodplain inundation was simulated using LISFLOOD-FP, which combines one-dimensional river routing with two-dimensional overland flow, and a local hydrological model. Dominant sources of inflow varied seasonally among direct rain and local runoff (November), Amazon River (December to August) and seepage (September and October). Shifts in timing of dominance among the water balance components occurred conform variations in annual peak stage. The period of dominance of river inflow over total floodplain influxes began about 1 month earlier and ended 1 month later in the 2009 high flood year compared to the 1998 low flood year. On average, river to floodplain discharge represented 0.75% of the Amazon River discharge at Obidos and 82% of the annual hydrological influxes to the floodplain. We observed an up to ninefold variation in river-floodplain annual discharge. Relatively small increments in main stem peak discharge cause disproportionately large changes in the flow routed through the floodplain. Despite the higher frequency of years with lower minimum stages, the intensification of the hydrological cycle of the Amazon Basin is causing substantially greater amounts of riverine water to flow across floodplain environments.

Emotion and Interhemispheric Interactions in Binocular Rivalry

Previous research has shown that fear-related stimuli presented in peripheral vision are preferentially processed over stimuli depicting other emotions. Furthermore, emotional content can influence dominance duration in binocular rivalry, with the period of dominance for an emotional image (e.g. a fearful face) being significantly longer than a neutral image (e.g. a neutral face or a house). Experiment 1 of the current study combined these two ideas to investigate the role of emotion in binocular rivalry with face/house pairs viewed in the periphery. The results showed that faces were perceived as more dominant than houses, and fearful faces more so than neutral faces, even when viewed in the periphery. Experiment 2 extended this paradigm to present a rival pair in the periphery in each hemifield, with each eye either viewing the same stimulus in each location (traditional condition), or a different stimulus in each location (Diaz-Caneja condition). The results showed that the two pairs tended to rival in synchrony only in the traditional condition. Taken together, the results show that face dominance and emotion dominance in binocular rivalry persist in the periphery, and that interhemispheric interactions in binocular rivalry depend on an eye- as opposed to an object-based mechanism.

High-resolution dynamics of the spring bloom in the Gulf of Finland of the Baltic Sea

During the period from March to the end of May in 2009 and 2010, intensive measurements and sampling were undertaken in the Gulf of Finland. The compiled results indicate a high variability of the phytoplankton distribution both temporally and spatially. The spring bloom dynamics and heterogeneity was influenced by physical forcing, such as prevailing circulation in the surface layer and the development of stratification, including the upward and downward movement of the seasonal thermocline. The estimated ratio of nitrogen to phosphorus consumption during the growth phase of the spring bloom was close to the Redfield ratio during both springs. The maximum phytoplankton carbon biomass was observed after the depletion of inorganic nitrogen from the surface layer, which coincides with the transition in the community dominance from diatoms to dinoflagellates. Diatoms exhibited a short, well-defined period of high biomass, and we argue that measurements with low temporal resolution can overlook this period of diatom dominance in the Gulf of Finland. The observed dominance of dinoflagellates (Peridiniella catenata and the Scrippsiella/Biecheleria complex) and the ciliate Myrionecta rubra might have a substantial biogeochemical impact because these species increase the retention time of newly produced material in the nutrient-limited surface layer in late spring.

The Valley of Fear

In 1949 a good government group in Phoenix began a long period of political dominance. Despite winning every mayoral and council election for two decades, during this era the group suffered a major policy defeat, as a grassroots group linked anticommunist fervor and concerns about private property rights to halt the city’s efforts at urban renewal and rehabilitating older urban housing. While this group reflected local concerns, it was also part of a nationwide far-right campaign against urban renewal and the National Municipal League. In Phoenix this campaign delayed establishment of a housing code for a decade, contributing to the further decline of the center city and encouraging suburban growth.

Reviewing the Final Function of the Disciplinary Institution of Shurta (Police) during Shiite Buyids Government Dominance on Baghdad

During Abbasid Dynasty, Shurta Institution (Police) was one of the disciplinary and security systems whose duty was establishing order and security as well as fighting against the corrupt people and criminals i.e. Ayyaran. During the third period of Abbasid dynasty, which is known as Buyids era, the institution of Shurta experienced a number of changes in comparison with the first Abbasids periods, some of which were. the direct interference of the governors of buyids in appointing Sahib Al-Shurta (Shurta administrator), paying the guaranty fee of this job to the treasury of Buyids in order to accept those jobs by those who were appointed to do so, and also political considerations in appointing Sahib Al-Shurta. In addition, at the end of the dominance of Buyids on caliphate of Abbasids and the beginning of their decline, another period of caliph’s interference was observed in appointing the administrators of the Shurta of Baghdad. This paper is aims at to study and analyze the function of this institution during the period of Buyids dominance on Caliphate of Abbasids in Baghdad (955-1068) and some of its consequences, as well as dealing with security circumstances of that period.

English Reduced Forms in Arabic Scientific Translation : A Case Study = ترجمة المختصرات الإنجليزية في النصوص العلمية إلى العربية : دراسة حالة

This study presents a periodization of the development of translation theory. Five major periods are presented from ancient times to the present. The estimated dates given represent heights in the consideration of issues in translation or period of dominance of certain issues. Even as some of these issues cut across periods, the heights should circumscribe the limitations and breadth of the various theoretical periods.

Differential succession towards woodland along a nutrient gradient

AbstractQuestionsHow do different substrate types and soil nutrient levels influence species composition and successional sequences, as represented by different life‐history traits? Is the rate of succession increasing or decreasing along a gradient from low to high fertility?LocationEcological field station Dahlem, Berlin, Germany.MethodsAn 18‐yr permanent plot study of succession on soils of differing fertility. The original substrates were a nutrient‐poor sandy soil from a sandpit, ruderal subsoil of moderate fertility and nutrient‐rich topsoil.ResultsIn plots with sand, monocarpic perennials were dominant at the beginning, which were then replaced by perennial grasses, those being then replaced by woody perennials. On ruderal soil, monocarpic perennials were co‐dominant with perennial herbs at first, then were replaced by perennial herbs, which were then also replaced by woody plants. Dominance of woody species was attained after about 10 yr, both on sand and on ruderal soil. In plots with topsoil, there was a short phase at the start where monocarpic perennials were co‐dominant with perennial herbs, followed by a relatively long period of perennial herb dominance. There were about twice as many woody species growing on the substrates of low and intermediate fertility compared to the nutrient‐rich soil. If we compare the time necessary for woody species to reach 10% and 50% cover, woody colonization was much slower on the resource‐rich site. DCA ordination revealed a clear separation of samples along the nutrient gradient. It also showed slower community change with increasing soil fertility.ConclusionsThis study demonstrates that woodlands can be created on bare ground in a temperate climate through natural colonization in a relatively short time, if substrates are not too nutrient‐rich. The assumption that the rate of succession increases with increasing productivity could not be confirmed. Succession towards woodland can be rapid on soils of low and intermediate fertility. In contrast, a nutrient‐rich substrate favours perennial herbaceous vegetation, which inhibits woody colonization and arrests succession.

Follicular and endocrinological turnover associated with GnRH induced follicular wave synchronization in Indian crossbred cows

The goal of this study was to record the hormonal and follicular turnover in Jersey crossbred cows when subjected for follicular wave synchronization using GnRH. Six healthy, non-lactating and regularly cycling Jersey crossbred cows (5–6 y) were used for the study. In the control group, the follicular wave pattern was ultrasonographically investigated in 18 cycles (3 cycles/cow). In the treatment group, GnRH analogue (buserelin acetate 10 μg im) was administered on Day 6 of the cycle and follicular wave pattern was studied in 12 cycles (2 cycles/animal). Follicular population was categorized based on their diameter Class I, ≤5 mm; Class II, >5–<9 mm; Class III, ≥9 mm) and the number of follicles in each category was determined on Day 6, Day 8 and Day 10. Plasma FSH and progesterone concentrations were estimated in both control and treatment groups. Out of 18 estrous cycles studied, 14 cycles (77.8%), three cycles (16.7%) and one cycle (5.6%) exhibited three-, two- and four-follicular waves per cycle, respectively. It was evident that the DF of Wave I established its dominance and was in the growing phase by Day 6 of the estrous cycle in all the normally cycling crossbred cows. The DF ovulated in all the animals (100%) in the mean interval of 27.7 ± 0.2 h after GnRH administration. A synchronized homogenous group of follicles emerged two days after GnRH injection (Day of 8.0 ± 0.0) in all the animals (100%). The combination of LH surge induced ovulation of DF (abrupt termination of Wave I) and FSH surge stimulated homogenous recruitment of Class I follicles, led to a synchronized emergence of follicular wave. All the GnRH treated cows had three follicular waves because of early emergence and short period of dominance of Wave II DF.

Effects of monocular deprivation on the spatial pattern of visually induced expression of c-Fos protein

We studied the pattern of expression of a protein product (c-Fos) of immediate-early gene (IEG) in the visual cortex of rats and mice. The basal expression of c-Fos was very low and visual exposure revealed a large number of c-Fos immunopositive cells in the visual cortex. We found that monocular deprivation during the sensitive period of ocular dominance (OD) plasticity significantly changed both the amount and pattern of c-Fos expression upon monocular stimulation of either eye. The number of immunopositive cells in layer IV of binocular subfields of the primary visual cortex (Oc1B) ipsilateral to the stimulated eye was found to be the most sensitive index of the effects of monocular deprivation during the sensitive period, that is, opened eye stimulation induced significantly larger numbers of c-Fos immunopositive cells, whereas closed eye stimulation induced significantly smaller numbers compared with those induced by monocular stimulation in control animals. In the lateral geniculate nucleus and superior colliculus, the pattern of expression of c-Fos following monocular stimulation was not affected by preceding monocular deprivation. Monocular deprivation imposed after the sensitive period did not affect the pattern of induction of c-Fos. Notably, in age-matched old animals that had been raised in total darkness and then experienced monocular deprivation, the distribution and numbers of c-Fos-expressing cells in visual cortex exhibited the same alterations as found in young animals during the sensitive period. These findings suggest that the present activity mapping method using c-Fos as a molecular marker is useful for examining the activity-dependent regulation of cortical plasticity, and provides an alternative method to conventional electrophysiological recording. This method is particularly powerful when applied to knockout or transgenic mice in which sampling biases in electrophysiological recording have been considered inevitable. Furthermore, these findings suggest that c-Fos is involved in OD plasticity as an IEG that transfers neuronal activity to late gene expression.

4 EFFECT OF A PROLONGED AROMATASE INHIBITOR TREATMENT ON PRE-OVULATORY OVARIAN FOLLICLES IN CATTLE

Letrozole, a non-steroidal aromatase inhibitor, prevents the body from producing its own oestrogen. The potential use of this compound for herd synchronization is supported by previous studies in which letrozole treatment increased mean plasma LH concentrations, prolonged the period of dominance of the extant dominant follicle and delayed emergence of the next follicular wave. Heifers given a 3-day regimen of letrozole exhibited greater corpus luteum diameter indicative of a luteotrophic effect. The objective of the present study was to test the hypothesis that letrozole treatment during the development of the preovulatory follicular wave will delay ovulation. Post-pubertal beef heifers were given 2 luteolytic doses of PGF (12 h apart) and monitored by ultrasonography for ovulation. Ovarian follicular wave emergence was synchronized by ultrasound-guided transvaginal follicular ablation 5 to 8 days after PGF-induced ovulation (Day –1 = follicular ablation, Day 0 = wave emergence) and a luteolytic dose of PGF was given 60 and 72 h later. On Day 1, heifers were divided randomly into 2 groups (n = 15/group) and given an intravaginal device containing 1 g of letrozole or a blank device (control). The intravaginal devices were removed on Day 7, or at the time of ovulation, whichever occurred first. The ovaries were monitored by ultrasonography and a blood sample was collected daily from day of ablation to 12 days post-ovulation. Single point measurements were analysed by t-tests and serial data were analysed by analysis of variance for repeated measures. Multiple contrasts were made by Tukey's test. The interval from placement of the intravaginal device to ovulation was longer in letrozole-treated animals (6.1 ± 0.25 vs 5.1 ± 0.26 days, P &lt; 0.01). Compared with controls, the day-to-day diameter profile of the dominant follicle of the ovulatory wave was larger (P &lt; 0.05) and the maximum diameter greater (14.6 ± 0.51 vs 12.4 ± 0.53 mm; P &lt; 0.01) in letrozole-treated heifers. The diameter profile of the corpus luteum formed post-letrozole treatment did not differ between groups; however, plasma P4 concentrations were higher (P &lt; 0.01) in heifers treated with letrozole. In summary, a slow-release intravaginal letrozole device delayed ovulation by 24 h and induced the formation of a corpus luteum that secreted higher levels of progesterone. A slow-release intravaginal letrozole device may become useful for the development of an aromatase inhibitor-based protocol to control ovulation for herd synchronization and to enhance fertility by increasing circulating progesterone concentrations during the first 7 days post-AI or embryo transfer in cattle. Supported by the Natural Sciences and Engineering Research Council of Canada and Bioniche Life Sciences Inc.

Crime prevention and community safety policies from a dynamic and comparative perspective: The cases of Rome and London

In the past 30 years, the issue of urban community safety has gained increased social and political relevance, being decisive in the results of national and local elections in Europe and elsewhere. Western countries have responded to increasing levels of fear and insecurity through the diffusion of ‘new prevention’ approaches, giving place to what has been called the ‘preventive turn’. The spread of these new approaches generated a debate around the convergence of policy ideas and solutions. These convergence processes have been widely interpreted as the result of macro-factors such as the deep socio-economic and cultural processes of change impacting post-modern societies, determining a phase of state restructuring rooted on neo-liberal principles. Despite the fact that convergence processes are taking place, significant elements of divergence are still present across Europe. These are attributed to the complexity and heterogeneity of what Hughes defines as ‘geo-histories’ (namely, a place's own geographic and historical context of reference) and to a country's institutional infrastructure. The objective of this work is to offer a contribution to the debate around convergence and policy change processes of crime prevention and community safety in Europe through a comparative analysis of community safety policies in Rome and London. The article concludes that different factors may impact upon policy divergence or convergence at different times. In the period of left-wing dominance up to 2008, local discourses and practices were strongly influenced by the different national and local politics on crime prevention and security, as well as by the different normative framework and governance patterns. However, since 2008 and the shift to right-wing local governments that assumed power, there has been a convergence based on discourses operating more at a symbolic and emotive level. Furthermore, there may be greater continuity in policy between politically different administrations than is immediately apparent.

An Automated Platform for Phytoplankton Ecology and Aquatic Ecosystem Monitoring

High quality monitoring data are vital for tracking and understanding the causes of ecosystem change. We present a potentially powerful approach for phytoplankton and aquatic ecosystem monitoring, based on integration of scanning flow-cytometry for the characterization and counting of algal cells with multiparametric vertical water profiling. This approach affords high-frequency data on phytoplankton abundance, functional traits and diversity, coupled with the characterization of environmental conditions for growth over the vertical structure of a deep water body. Data from a pilot study revealed effects of an environmental disturbance event on the phytoplankton community in Lake Lugano (Switzerland), characterized by a reduction in cytometry-based functional diversity and by a period of cyanobacterial dominance. These changes were missed by traditional limnological methods, employed in parallel to high-frequency monitoring. Modeling of phytoplankton functional diversity revealed the importance of integrated spatiotemporal data, including circadian time-lags and variability over the water column, to understand the drivers of diversity and dynamic processes. The approach described represents progress toward an automated and trait-based analysis of phytoplankton natural communities. Streamlining of high-frequency measurements may represent a resource for understanding, modeling and managing aquatic ecosystems under impact of environmental change, yielding insight into processes governing phytoplankton community resistance and resilience.

The role of management on the rate of secondary succession in Mediterranean shrubland after fire

Ephemeral grasslands follow fire in Mediterranean batha communities on phosphorus-deficient terra-rossa soils, but successional processes rapidly restore shrub dominance. In an experiment aimed at reducing the rate of successional change and extending the period of grassland dominance, phosphorus was applied to a shrub community dominated by Sarcopoterium spinosum. This was done once in 1988, immediately after a fire. Two years later, the regenerating shrubs were treated with herbicide. Subsequently, the vegetation in the treatments was monitored for 20 consecutive years. The vegetation was undisturbed during the winter/spring growing season but was grazed during the dry summer of each year by beef cattle, which were given ad libitum access to poultry litter to supplement the nitrogen deficiency of the dry herbaceous vegetation. In control plots, the shrubs returned to pre-fire dominance within 5 years. With phosphorus and herbicide, shrub dominance was delayed by the vigorous herbaceous vegetation for more than 20 years. The practical feasibility of this management option depends on the relation between costs and benefits. A preliminary economic analysis based on the long-term experiment and a case study allowed us to define the conditions under which control of successional shrub encroachment can be economically feasible.