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1.
Alan J. Terry 《Journal of mathematical biology》2010,61(6):843-875
We consider a model for a creature inhabiting two patches between which migration may occur. The creature is assumed to have
a life cycle with two stages, namely juvenile and adult, giving rise to a delay differential system. The creature could represent
an insect crop pest whilst the patches could represent neighbouring farms. Given that it is common to control crop pests by
adult impulsive culling, we impose an adult impulsive culling regime on each patch. We find conditions on the regimes such
that the pest will be eradicated on both patches simultaneously. The regime on one patch is assumed to be independent of the
regime on the other patch to reflect the possibility that the patches represent farms with different owners where each owner
has autonomy in their pest control decisions. In the special case where the birth functions on both patches are of an Allee
type, we calculate explicit finite upper bounds for the number of culls needed on each patch to guarantee eradication. Simulations
corroborate our theoretical results. 相似文献
2.
Culling can be an effective management tool for reducing populations of invasive species to levels that minimize ecological effects. However, culling is labour-intensive, costly, and may have unintended ecological consequences. In the Caribbean, culling is widely used to control invasive Indo-Pacific lionfish, Pterois volitans and P. miles, but the effectiveness of infrequent culling in terms of reducing lionfish abundance and halting native prey decline is unclear. In a 21-month-long field experiment on natural reefs, we found that culling effectiveness changed after the passage of a hurricane part-way through the experiment. Before the hurricane, infrequent culling resulted in substantial reductions in lionfish density (60–79%, on average, albeit with large uncertainty) and slight increases in native prey species richness, but was insufficient to stem the decline in native prey biomass. Culling every 3 months (i.e., quarterly) and every 6 months (i.e., biannually) had similar effects on lionfish density and native prey fishes because of high rates of lionfish colonization among reefs. After the hurricane, lionfish densities were greater on all culled reefs compared to non-culled reefs, and prey biomass declined by 92%, and species richness by 71%, on biannually culled reefs. The two culling frequencies we examined therefore seem to offer a poor trade-off between the demonstrated conservation gains that can be achieved with frequent culling and the economy of time and money realized by infrequent culling. Moreover, stochastic events such as hurricanes can drastically limit the effectiveness of culling efforts. 相似文献
3.
B. M. Mercado-Borrayo Silke Cram Heydrich Irma Rosas Pérez Manuel Hernández Quiroz 《International journal of phytoremediation》2015,17(7):701-708
A natural wetland in Mexico City Metropolitan Area is one of the main suppliers of crops and flowers, and in consequence its canals hold a high concentration of organochlorine (OC) and organophosphorus (OP) pesticides. There is also an extensive population of water hyacinth (Eichhornia crassipes), which is considered a plague; but literature suggests water hyacinth may be used as a phytoremediator. This study demonstrates bioaccumulation difference for the OC in vivo suggesting their bioaccumulation is ruled by their log Kow, while all the OP showed bioaccumulation regardless of their log Kow. The higher bioaccumulation factors (BAF) of the accumulated OC pesticides cannot be explained by their log Kow, suggesting that the OC pesticides may also be transported passively into the plant. Translocation ratios showed that water hyacinth is an accumulating plant with phytoremediation potential for all organophosphorus pesticides studied and some organochlorine pesticides. An equation for free water surface wetlands with floating macrophytes, commonly used for the construction of water-cleaning wetlands, showed removal of the pesticides by the wetland with room for improvement with appropriate management. 相似文献
4.
Summary We have attempted quantitatively through a series of assortative mating models to gain insight into the interaction between the usually antagonistic tendencies of artificial and natural selection pressures. We summarize some of the robust conclusions. In cases where natural selection is expressed only through the phenotype and acts in the opposite direction to the culling incline, then fixation of the dominant or recessive type can be achieved and which occurs depends critically on the initial composition of the population and the magnitude of the degree of culling compared to the selection coefficients.With traits determined at two loci in the case that the double heterozygote is the desired kind, the effect of selfing can only be overcome by very strong artificial selection pressures (high culling order). The degree of culling to achieve its objective can be relaxed with weakening of linkage. The relevant comparison is r
2 + (1 – r)2 < (1 – c)indicating the precise extent of culling needed, to prevent fixation. The relationships are more complex when natural selection forces are also involved (see Model IV).Supported in part by NIH Grant USPHS 10452-09. 相似文献
5.
Sterilization has rarely been considered as an alternative to culling or vaccination to control wildlife diseases. Disease control by sterilization, as by culling, has most promise when the host'ss ability for compensatory growth following the removal of density-dependent inhibitions is limited, and when moderate reductions in population density cause disproportionately large reductions in disease prevalence, or even eliminate the disease. For many host/disease examples this will not be the case and vaccination may have overwhelming advantages or may be the only practical option. The impact of sterilization on host density and disease prevalence will develop relatively slowly because sterilization can prevent the recruitment of only one age-cohort at a time. Moreover, unless there is vertical transmission, this age-cohort will consist only of susceptibles. Culling, on the contrary, removes infected as well as susceptible animals. However, for certain disease/host examples, the r elative effectiveness of the different control strategies may be altered considerably if their variable effects on the probability of disease transmission are taken into account. Social perturbation or stress could render certain culling strategies ineffective or even counter-productive. Depending on how disease dynamics are influenced by the host'ss age-structure and reproductive investment, fertility control could offer epidemiological advantages that have been ignored by most disease/host models. We illustrate some of these principles by investigating the theoretical and practical feasibility of an hypothetical sterilization campaign to control bovine tuberculosis in badgers (and hence cattle) in Britain. 相似文献
6.
《Animal : an international journal of animal bioscience》2021,15(5):100204
Taking into account functional traits in the breeding practice should lead to a longer productive life of cows. However, despite the increased contribution of these traits in bull selection indices, their daughters are frequently culled as early as the 2nd or 3rd lactation. The problem is whether and to what extent the genetic potential of animals is realized in the production practice. Therefore, the purpose of this study was to determine the associations between the breeding value (BV) of bulls and their daughters for cow longevity and culling reasons in the Holstein-Friesian cattle population in Poland. Data for 532 062 cows culled in 2012, 2015, and 2018 were analyzed. A majority of 5 045 cow sires originated from Poland, Germany, France, the Netherlands, and the United States. The highest variation in the contribution of culling reasons was for the cows culled at the age of 2–4 years. The contribution of the culling reasons, analyzed in relation to the cow culling age, remained similar and the only exception was culling because of old age, for which a significant increase was observed only for the culling age of at least 9 years (13.8%), which was reached by only 7.3% of the cows. The sires were characterized by generally high BV for conformation and reproductive traits. However, they had, at most, the average genetic potential for functional longevity. There were a number of beneficial associations found between the BV of bulls and the distribution of culling reasons in their daughters. For example, it concerns relations between the somatic cell score in milk and culling due to udder diseases and low milk yield, between the interval from calving to first insemination and low milk yield, between the protein yield and old age, or between the BV for certain conformation traits (size, udder) and cow culling due to age. In these cases, as the BV increased for a given trait, the contribution of the corresponding cow culling reason tended to decrease. Our study showed that it seems reasonable to consider Holstein-Friesian cows aged at least 9 years at culling to be long-living animals. This is primarily evidenced by the rapid increase in the culling due to old age in relation to younger cows. Nowadays the above age limit can be suggested as a criterion of longevity for Holstein-Friesian cows but the criterion should be updated to the relation genotype-environment-economy that tends to change over time. 相似文献
7.
Lu Z Mitchell RM Smith RL Van Kessel JS Chapagain PP Schukken YH Grohn YT 《Journal of theoretical biology》2008,254(1):135-146
Johne's disease is caused by Mycobacterium avium subsp. paratuberculosis (MAP) infection and results in economic losses in the dairy industry. To control MAP transmission in herds, test-based culling has been recommended and immediate culling of high shedding animals is typically implemented. In this study, we quantified the effects of MAP control in US dairy herds, using the basic reproduction ratio R0. The effectiveness of culling strategies was evaluated for good and poor herd management (low- and high-transmission rates, respectively) by a phase diagram approach. To establish a quantitative relationship between culling rates and test properties, we defined the average detection times for low and high shedding animals. The effects of various culling strategies and test characteristics, such as test sensitivity, test turnaround time, and testing interval, were analyzed. To understand the overall effect of model parameters on R0, we performed global uncertainty and sensitivity analyses. We also evaluated the effectiveness of culling only high shedding animals by comparing three test methods (fecal culture, fecal polymerase chain reaction, PCR, and enzyme-linked immunosorbent assay, ELISA). Our study shows that, in the case of good herd management, culling of only high shedding animals may be effective in controlling MAP transmission. However, in the case of poor management, in addition to immediate culling of high shedding animals, culling of low shedding animals (based on the fecal culture test) will be necessary. Culling of low shedding animals may be delayed 6-12 months, however, if a shorter testing interval is applied. This study suggests that if farmers prefer culling only high shedding animals, faster MAP detection tests (such as the fecal PCR and ELISA) of higher sensitivity should be applied with high testing frequency, particularly on farms with poor management. Culling of infectious animals with a longer testing interval is generally not effective to control MAP. 相似文献
8.
J. Mark Scriber 《Journal of Insect Conservation》2004,8(2-3):243-263
Management programs for major forest defoliators such as gypsy moths or forest tent caterpillars, and crop pests such as the European corn borer have shifted from broad-spectrum insecticides to more environmentally benign microbial pesticides such as Bacillus thuringiensis (foliage sprays and transgenic toxin expression in plant tissues). Phytochemically resistant host plants and natural enemies have been used as alternative pest management strategies (including generalist tachinid flies such as Compsilura, viruses, microsporidians, and fungi), but all of these have some non-target impacts, as described from literature review. A sequence of lab and field studies were conducted to determine non-target impacts on native Lepidoptera in North America. The conclusions reached are that a decision not to spray Bt pesticides (i.e. to allow defoliation and natural pest outbreaks to run their course) could be as bad or worse for non-target Lepidoptera as the microbial insecticides would be. The important concept that must be maintained is that all pest management programs have some risk of negative non-target impacts, but it is the magnitude and relative importance that will remain the most critical issue for environmental impacts and pest management. 相似文献
9.
Alternative environmentally friendly methods for pest control are in high demand because of the environmental impacts of pesticides. Notably, predator-released kairomone is a natural compound released by natural enemies, which mediates non-consumptive effects between natural enemies and prey. However, this novel pest control agent is underutilized relative to pesticides and natural enemies. Additionally, the effects of spraying predator kairomone on the number and diversity of arthropods in fields and whether this method is environmental-friendly are poorly understood. In the present study, a predator kairomone, rove beetle (Paederus fuscipes Curtis) abdominal gland secretion (AGS), was sprayed in rice fields to investigate whether AGS can suppress pest populations or will affect the fields’ arthropod communities. After AGS spraying, the abundance of arthropods decreased throughout the first 12-d period, including arthropod pests such as hemipterans (small brown planthopper, Laodelphax striatellus (Fallén), brown planthopper, Nilaparvata lugens (Stål), white-backed planthopper, Sogatella furcifera (Horváth), and leafhoppers), and lepidopterans (rice leaf folder, Cnaphalocrocis medinalis Guenée). The abundance of arthropod predators was not affected, except for predatory spiders, which decreased, and rove beetles (P. fuscipes), which increased. In the terms of arthropod diversity, neither pests nor their natural enemies were changed by AGS application. This work highlights that predator kairomone can temporarily suppress pest populations in fields but has no adverse effects on arthropod diversity; thus, this approach is environmentally friendly and can be used in real-world applications. Broadly, present studies suggest that the application of predator kairomone may have synergistic or cumulative effects on pest suppression. 相似文献
10.
Now you See them, Now you don't! – Population Crashes of Established Introduced Species 总被引:4,自引:3,他引:1
Substantial populations of invasive non-indigenous species occasionally collapse dramatically. Although disease is often invoked, the causes are rarely studied experimentally and/or quantitatively, and some collapses remain quite mysterious. The widespread invasive snail Achatina fulica and pondweed Elodea canadensis appear to be characterized by rapid expansion followed by rapid decline. For the former species, disease may be the proximal cause of the collapse, while repeated collapse of the latter species is unexplained. Several other widely cited collapses of introduced species may simply be temporary lows during a more or less regular boom-and-bust cycle. However, on a restricted site (such as a small island), a boom-or-bust cycle may be impossible and recovery may never ensue; local extinction may even occur. In several instances, apparently spontaneous crashes were in fact probably caused by subsequently introduced competitors. Except for the few species in which spontaneous collapse has been repeatedly observed, the possibility of such an event is unwarranted as a potential rationale for a do-nothing approach to management. For such species, even if a crash ultimately occurs, the species may already have caused persistent ecological damage. 相似文献
11.
N. Rashevsky 《Bulletin of mathematical biology》1966,28(2):283-308
To the extent that all biological phenomena are perceivable only through their physical manifestations, it may be justified
to assume that all biological phenomena will be eventually represented in terms of physics; perhaps not of present day physics,
but of some “extended” form of it. However, even if this should be correct, it must be kept in mind that representing individual
biological phenomena in terms of physics is not the same as deducing from known physical laws the necessity of biological
phenomena. Drawing an analogy from pure mathematics, it is possible that while every biological phenomenon may be represented
in terms of physics, yet biological statements represent a class of “undecidable” statements within the framework of physics.
Such a conjecture is reinforced by the history of physics itself and illustrated on several examples. The 19th century physicists
tried in vain todeduce electromagnetic phenomena from mechanical ones. A similar situation may exist in regard to biological and social sciences.
Quite generally, the possibility of representing a class B phenomena in terms of class A phenomena does not imply that the
phenomena of class B can be deduced from those of class A.
The consequences of the above on the relation between physics, biology, and sociology are studied. A tentative postulational
formulation of basic biological principles are given and some consequences are discussed. It is pointed out that not only
can the study of biological phenomena throw light on some physical phenomena, but that the study of social phenomena may be
of value for the understanding of the structures and functions of living organisms. The possibility of a sort of “socionics”
is indicated. 相似文献
12.
Actinobacteria (Actinomycetes) are a significant and interesting group of gram-positive bacteria. They are regular, though infrequent, members of the microbial
life in the rumen and represent up to 3 % of total rumen bacteria; there is considerable lack of information about ecology
and biology of rumen actinobacteria. During the characterization of variability of rumen treponemas using non-cultivation
approach, we also noted the variability of rumen actinobacteria. By using Treponema-specific primers a specific 16S rRNA gene library was prepared from cow and sheep rumen total DNA. About 10 % of recombinant
clones contained actinobacteria-like sequences. Phylogenetic analyses of 11 clones obtained showed the high variability of
actinobacteria in the ruminant digestive system. While some sequences are nearly identical to known sequences of actinobacteria,
we detected completely new clusters of actinobacteria-like sequences, representing probably new, as yet undiscovered, group
of rumen Actinobacteria. Further research will be necessary for understanding their nature and functions in the rumen. 相似文献
13.
R F Shaw 《The Journal of heredity》1991,82(1):77-80
Codons that differ from a terminator triplet by only a single base are sometimes thought, because of their greater risk of undergoing a harmful mutation, to be kept at a reduced frequency by natural selection. The present study on human genes shows that these codons are infrequent, but their low frequency is not directly related to their risk of mutation to terminator. Rather, it is a consequence of their ending in A or G; comparable A-ending and G-ending codons that are not mutable to terminator are also infrequent. Natural selection does not appear to have depressed the frequency of mutable-to-terminator codons by directly eliminating some of them individually. It may have depressed their frequency indirectly by adjusting mutation rates in the population so that most of the purine-ending codons--and consequently most of the mutable-to-terminator ones as well--are infrequent. 相似文献
14.
Assessing the effects of the first 2 years of industry‐led badger culling in England on the incidence of bovine tuberculosis in cattle in 2013–2015
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Lucy A. Brunton Christl A. Donnelly Heather O'Connor Alison Prosser Stuart Ashfield Adam Ashton Paul Upton Andrew Mitchell Anthony V. Goodchild Jessica E. Parry Sara H. Downs 《Ecology and evolution》2017,7(18):7213-7230
15.
The stoat (Mustela erminea) is a specialist predator that evolved to exploit the unstable populations of northern voles and lemmings. It was introduced
to New Zealand, where it is pre-adapted to respond with a population irruption to the resource pulses that follow a heavy
seedfall of southern beech (Nothofagus spp.). Culling stoats during an irruption is necessary to reduce damaging predation on nesting endemic birds. Culling might
not reduce the stoat population long term, however, if high natural mortality exceeds culling mortality in peak years. During
other phases of the beech-mast cycle, culling might have a greater effect on a smaller stoat population, whether or not damage
prevention is critical. We developed a 4-matrix model to predict the effects of culling on λ, the annual rate of change in
the size of the stoat population, through the four annual phases of an average masting cycle, explicitly distinguishing between
apparent and real culling. In the Post-seedfall phase of the cycle, large numbers of stoats are killed, but little of this
extra mortality is additive; in other phases, culling removes larger proportions of smaller total numbers of stoats that would
otherwise have lived. Culling throughout all phases is most effective at reducing stoat populations, but is also the most
expensive option. Culling in Post-seedfall plus Seed or Crash years is somewhat less effective but better than culling in
one phase only. Culling has different short-term effects on stoat age distribution depending on the phase of the cycle when
culling begins. 相似文献
16.
Incorporating Natural Variability into the Assessment of Ecological Health in Australian Dryland Rivers 总被引:2,自引:2,他引:0
Dryland rivers occur over much of Australia’s inland and have some of the most variable patterns of flow in the world. Despite
their dominance in terms of Australia’s river types, dryland rivers have not been the focus of the recent increase in research
on indicators of river health, mostly owing to their spatial remoteness and relatively low levels of water resource development
and human disturbance. Most rivers in arid and semi-arid regions are ephemeral, and only carry significant flows during the
wetter months or following infrequent but intense rainfall events. It is not known which, if any, of the existing approaches
to river health assessment can be used to accurately assess the health of these large ephemeral rivers. This paper considers
why the standard methods for interpreting the currently-used indicators for river health may need to be adapted for variable
systems and suggests the use of trends that recognise natural variation in indicator values for undertaking this. 相似文献
17.
William H. Romme Edwin H. Everham Lee E. Frelich Max A. Moritz Richard E. Sparks 《Ecosystems》1998,1(6):524-534
In this article, we develop a heuristic model of ecosystem-disturbance dynamics that illustrates a range of responses of
disturbance impact to gradients of increasing disturbance extent, intensity, or duration. Three general kinds of response
are identified and illustrated: (a) threshold response, (b) scale-independent response, and (c) continuous response. Threshold responses are those in which the response curve shows a discontinuity or a sudden change in slope along the axis of increasing disturbance
extent, intensity, or duration. The response threshold occurs at a point where the force of the disturbance exceeds the capacity
of internal mechanisms to resist disturbance, or where new mechanisms of recovery become involved. Within this conceptual
framework, we find that some unusually large or intense disturbances, but not all, produce qualitatively different responses
compared with similar disturbances of lesser magnitude. If disturbance impact does not increase with increasing disturbance
extent, intensity, or duration, or if the response curve changes monotonically, then large disturbances are not qualitatively different from small ones. For example, jack pine tends to become reestablished after stand-replacing fire
in boreal forests, regardless of fire size, because its serotinous cones provide an adequate seed source throughout the burned
area. Thus, large fires are not qualitatively different from small fires in terms of jack pine reproduction. However, if disturbance
impact does increase abruptly at some point with increasing disturbance extent, intensity, or duration, often because of thresholds
in the capacity of internal mechanisms to resist or respond to disturbance impact, then large disturbances are qualitatively different from small ones, at least for some parameters of ecological response. For example, balsam fir and
white cedar can recolonize a small burned patch of boreal forest in close proximity to surviving individuals of these species,
but they will be eliminated from a large burn because of their susceptibility to fire-caused mortality and their inability
to disperse their seeds over long distances. The conceptual framework presented here permits some new insights into the dynamics
of natural systems and may provide a useful tool with which managers can assess the potential for catastrophic damages resulting
from large, infrequent disturbances.
Received 14 July 1998; accepted 29 September 1998 相似文献
18.
R. SCHMUCK H. MAGER Ch KÜNAST K-D BOCK S. STORCK-WEYHERMÜLLER 《The Annals of applied biology》1996,128(3):437-451
Nowadays the development of pesticides is not only directed to design compounds with sufficient efficacy against resistant and non-resistant strains of pests as well as with a high margin of safety for man and the environment, but also to allow their potential use in IPM (Integrated Pest Management) programmes. For identification of IPM suitable pesticides, a whole battery of standardised laboratory and semi-field test protocols have been developed. Based on the observed lethal and sublethal effects in those tests, compounds are categorised into different hazard groups which should advise farmers on their suitability for IPM. For a valid classification of compounds on the basis of laboratory test results, threshold values for lethal and sublethal effects have to be developed which reliably differentiate between harmful and safe compounds without bearing the risk of erroneous labelling and/or too frequent requests for higher tier testing. As an evaluation criterion for sublethal effects of pesticides, the reproductive performance of beneficial insects is frequently considered in standard laboratory assays. A preliminary analysis of available data on the reproductive performance of several standard test species elaborated during regulatory testing indicates that this evaluation criterion is subject to high variability. As expected, individual test species differed in their reproductive performance. Aleochara bilineata (Coleop-tera: Staphylinidae) and Orius insidiosus (Heteroptera: Anthocoridae) showed a fairly homogeneous reproductive performance within test series. Based on the observed variability of the reproductive performance in control groups, the average probability of an erroneous labelling of pesticides for these two species was only 4% and 6% (maximum probability: 13% and 19%), respectively, when an adverse effect threshold value of 30% (= actual value of the EU (European Union)) was applied. In contrast, Coccinella septempunctata (Coleoptera: Coccinellidae), Chryso-perla carnea (Neuroptera: Chrysopidae), Aphidius rhopalosiphi (Hymenoptera: Aphidiidae) and Trichogramma cacoeciae (Hymenoptera: Trichogrammatidae) exhibited a high variability in their reproductive performance, giving a mean probability between 25% and 35% (maximum probability: 36–64%) to label a pesticide either false positive or false negative. Besides species-inherent variability, there was an indication that test-inherent factors including parent sex ratio and parent breeding density may have had an influence on the reproductive performance of these insect species. Seasonal influences on the reproductive performance of the beneficial insects in laboratory testing were not evident. Based on our data analyses, there is a significant risk of erroneous classification of pesticides when the reproductive performance is quantitatively assessed following the currently established test protocols and an adverse effects threshold value of 30% is applied. We propose therefore that either the testing procedure for assessing the reproductive performance, or the effect threshold value for this evaluation criterion is reconsidered in the light of the high “species-inherent” variability in the reproductive performance of some beneficial insects. 相似文献
19.
Reini W Bretveld Chris MG Thomas Paul TJ Scheepers Gerhard A Zielhuis Nel Roeleveld 《Reproductive biology and endocrinology : RB&E》2006,4(1):30
Some pesticides may interfere with the female hormonal function, which may lead to negative effects on the reproductive system
through disruption of the hormonal balance necessary for proper functioning. Previous studies primarily focused on interference
with the estrogen and/or androgen receptor, but the hormonal function may be disrupted in many more ways through pesticide
exposure. The aim of this review is to give an overview of the various ways in which pesticides may disrupt the hormonal function
of the female reproductive system and in particular the ovarian cycle. Disruption can occur in all stages of hormonal regulation:
1. hormone synthesis; 2. hormone release and storage; 3. hormone transport and clearance; 4. hormone receptor recognition
and binding; 5. hormone postreceptor activation; 6. the thyroid function; and 7. the central nervous system. These mechanisms
are described for effects of pesticide exposure in vitro and on experimental animals in vivo. For the latter, potential effects of endocrine disrupting pesticides on the female reproductive system, i.e. modulation
of hormone concentrations, ovarian cycle irregularities, and impaired fertility, are also reviewed. In epidemiological studies,
exposure to pesticides has been associated with menstrual cycle disturbances, reduced fertility, prolonged time-to-pregnancy,
spontaneous abortion, stillbirths, and developmental defects, which may or may not be due to disruption of the female hormonal
function. Because pesticides comprise a large number of distinct substances with dissimilar structures and diverse toxicity,
it is most likely that several of the above-mentioned mechanisms are involved in the pathophysiological pathways explaining
the role of pesticide exposure in ovarian cycle disturbances, ultimately leading to fertility problems and other reproductive
effects. In future research, information on the ways in which pesticides may disrupt the hormonal function as described in
this review, can be used to generate specific hypotheses for studies on the effects of pesticides on the ovarian cycle, both
in toxicological and epidemiological settings. 相似文献
20.
Abstract. Consequences of sulfide toxicity on succession in wet calcareous dune slacks were investigated. Sulfide may exert an inhibitory effect on dune slack plants, but several pioneer species exhibit ROL (Radial Oxygen Loss) and thereby protect themselves against free sulfide. Under oxic conditions free sulfide will be oxiginated to harmless sulfate. However, successive species when not capable of ROL may be sensitive to free sulfide and cannot invade the area. Therefore, the occurrence of free sulfide may have a stabilizing effect on the pioneer vegetation. Data on the vertical distribution of oxygen, redox and sulfide were collected in mesocosms with Littorella uniflora or Carex nigra, with and without microbial mats and compared to control mesocosms. Also, in situ data were collected in a dune slack on the Frisian Island of Texel. In the mesocosms, free sulfide was detected only at nighttime in C. nigra populated mesocosms and in unvegetated units, but not in L. uniflora vegetated mesocosms. In the field, sulfide and redox profiles showed distinct differences between the groundwater exfiltration and infiltration site of the dune slack. At the exfiltration site, sulfide was only occasionally found; in contrast, measurable amounts of free sulfide were regularly found at the infiltration site of the slack. Since Phragmites australis dominates in the infiltration site of the slack, the results suggest that free sulfide accelerate the succession, rather than slowing it down by the exclusion of some plant species. 相似文献