Abstract Aims Seed bank strongly influences composition and structure of aboveground vegetation. Little attention has been paid to the role of allelopathy driving soil seed bank dynamics, even though allelochemicals released by allelopathic plants might determine whether a species can or cannot germinate from the soil seed bank and, therefore, to co-exist in the neighborhood of the allelopathic species. Hence, the effects of allelopathic plants on community organization through the effects of allelochemicals on soil seed bank remain largely unknown. In this study, we assessed spatial heterogeneities in soil seed bank caused by the presence of allelopathic plants, and evaluated allelopathic effects on seed bank germination and seedling mortality.
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Abstract Aims Seed bank strongly influences composition and structure of aboveground vegetation. Little attention has been paid to the role of allelopathy driving soil seed bank dynamics, even though allelochemicals released by allelopathic plants might determine whether a species can or cannot germinate from the soil seed bank and, therefore, to co-exist in the neighborhood of the allelopathic species.
Hence, the effects of allelopathic plants on community organization through the effects of allelochemicals on soil seed bank remain largely unknown. In this study, we assessed spatial heterogeneities in soil seed bank caused by the presence of allelopathic plants, and evaluated allelopathic effects on seed bank germination and seedling mortality.
Methods We examined the effects of the allelopathic shrub Artemisia herba-alba Asso on the spatial structure in terms of species richness and seed density of the soil seed bank of a semi-arid ecosystem in NE Spain.
Specifically, we evaluated seed bank richness and density at three microsites: under the canopy of A. In addition, we assessed the effects of aqueous extract of A. Important Findings We found that seed bank richness and density were higher under shrub canopy than they were in bare soil.
However, seed bank density was higher under A. On the other hand, aqueous extract did not influence the emergence timing of seedlings. We conclude that, although the presence of allelopathic plants does not cause relevant changes in seed bank structure relative to similar non-allelopathic shrubs, their presence can actually result in a reduction of seedling emergence from the seed bank, which leads to low plant species richness and density nearby.
To our knowledge, this is the first study to examine the effect of an allelopathic plant on the structure and germination in an entire soil seed bank. It is a well-studied process in the field of agriculture Narwal et al. In addition, allelopathic mechanisms are proposed often to explain the success of non-native plant species in invaded communities Callaway and Ridenour ; Thorpe et al. However, much less attention has been paid to the role of allelopathy in natural ecosystems Inderjit et al.
In Mediterranean-like regions, many herbaceous, aromatic shrubs and trees species exhibit allelopathy Thompson ; Scognamiglio et al. Apart from being a widespread feature of plants in those habitats, production of allelochemicals or its phytotoxicity are enhanced under stressful conditions Pedrol et al. Furthermore, in those stressful environments, where facilitative interactions predominate Soliveres and Maestre , allelopathy might arise as an evolutionary mechanism for avoiding such interactions van der Putten and, therefore, lessen direct competition for resources with surrounding vegetation Gant and Clebsch Thus, allelopathy might be particularly relevant driving the dynamics of arid and semi-arid plant communities.
The highly unpredictable climate of drylands makes soil seed bank a crucial factor that strongly influences the persistence and co-existence of some species in the community Chesson et al. In those environments, vegetation cover is clumped into patches that alternate with inter-patches areas of bare soil. Patches of vegetation act as seed sources and sinks Caballero et al. Consequently, the soil seed bank follows a similar patchy pattern, and the number of species and density of seeds under vegetation patches is higher than it is in bare soil Aguiar and Sala ; Caballero et al.
Thus, it is expected that seedling emergence occurs mostly in vegetation patches Aguiar and Sala But the chemical microenvironment constitutes a determinant factor that promotes or inhibits seed germination Long et al. The presence of allelochemicals can determine whether a species can tolerant or cannot intolerant co-exist in the neighborhood of the allelopathic species Ehlers et al. However, the consequences that the presence of allelopathic plants have on community organization through the effects of allelochemicals on soil seed bank remain poorly understood Fabbro et al.
Assessing the allelopathic activity of allelochemicals often relies on identifying their influence on seed germination and seedling performance Gniazdowska and Bogatek ; Scognamiglio et al. It is well known that allelochemicals typically inhibit seed germination Escudero et al. Mechanisms underlying those effects are multiple and they are associated with a disruption of normal cell metabolism, rather than with a cell damage Gniazdowska and Bogatek Positive effects of allelochemicals have been reported too Fernandez et al.
Many of those studies on allelopathy, however, have been based on greenhouse experiments that included one or two test species only Escudero et al. Lactuca sativa L. Model species are not useful for demonstrating the significance of allelopathy in natural communities because they do not co-exists with the allelopathic species Inderjit and Callaway Furthermore, the use of a single test species does not allow for the assessment of species—specific responses to allelopathy Linhart et al.
Soil seed bank might constitute a valuable alternative to test for the effects of allelopathy on several species that co-exists with the allelopathic one in natural plant communities and, thus, provide meaningful information about the role of allelopathy in seed germination in natural environments. In this study, we investigated the effects of the allelopathic species Artemisia herba-alba Asso on the dynamics of a semi-arid plant community through the effects on soil seed bank.
Specifically, we assessed i spatial heterogeneities in soil seed bank caused by the presence of allelopathic plants and ii the allelopathic effects on seed bank germination and seedling mortality.
Artemisia herba-alba desert wormwood is an aromatic dwarf shrub that is very common in many arid and semi-arid regions of the Mediterranean basin. Like many other species in the genus Artemisia Asteraceae , its allelopathic nature is well documented Abad et al. We hypothesized that i vegetation patches of either allelopathic or non-allelopathic plants will act as sources and sinks of seeds, which increases species richness and density of seeds in the seed bank compared to bare soil areas.
In addition, we expected to find differences between allelopathic and non-allelopathic plant species in seed bank structure. Although patches created by A. Therefore, we hypothesized that ii species richness and density of the soil seed bank will be lower under A. Alternatively, dispersal and seed trapping might allow A.
To test the first hypothesis, we compared the structure in terms of species richness and density of seeds of viable seed bank of soil samples collected from bare soil areas and vegetation patches. To test the second hypothesis, we compared the structure of viable seed bank of samples collected from under A. To test the third hypothesis, we measured seed bank germination seedling emergence and emergence timing and seedling mortality of samples that were treated with aqueous extract of A.
The average temperature ranges from 7. Topography is characterized by a flat-bottomed valley surrounded by low hills. Soils are very rich in clay and are slightly saline.
The main human activity in the study area involved a traditional agro-pastoral land use Pueyo Natural plant communities on non-cultivated lands are dominated by shrubs e. Dactylis glomerata L. Soil is sparsely covered by lichens e. Diploschistes diacapsis, Squamarina lentigera and Fulgensia sp. Figure 1: A location of the study area and selected individuals.
B Schematic of the seed bank sampling design. Seed bank sampling and experimental design In January , soil samples were collected from three microsites. Specifically, 20 A. Selected individuals of A. S1 , although S. Soil cores were 3.
We followed the seedling emergence method Heerdt et al. First, soil samples were soaked about ten minutes in a sodium bicarbonate NaHCO3 solution to cause disaggregation of clays. Then, soil samples were washed over a 4 mm mesh sieve to remove the coarse fraction of the soil and washed again over a 0. Pots were irrigated with fresh water regularly.
Seedling emergence was monitored during 30 days after the end of the experiment, but further germination did not occur. Pot positions were changed randomly to prevent any potential site effect. The concentration was equivalent to add approximately 0. Aqueous extract was obtained by soaking aerial parts fresh shoots and leaves of different A. Fresh material was collected in spring from a natural population of the study area.
The resultant extract was filtered, stored in small bottles ml and frozen until it was used. Allelopathic activity of aqueous extract of S. Seedling emergence was tracked weekly. In particular, species richness and seed density were quantified as the number of species and the number of seedlings, respectively, that emerged from each sample.
Emergence timing was quantified as the difference, in days, between the time at which the sample was set to germinate and the time at which the seedling was first observed. Seedling mortality was quantified as the ratio between the number of dead seedlings and the number that emerged from each sample. We employed Poisson distribution of errors because our count data did not meet the assumptions of normality, even after various data transformations.
In the analysis of seed density, a negative binomial GLM was performed to deal with data overdispersion. Assessments of seed bank structure were based on the pots that were not treated with aqueous extract. The effect of aqueous extract of A. Specifically, we assessed the significance of differences in species richness and seedling abundance between treated and non-treated pots with separate GLMMs with Poison distribution of errors.
Treatment was set as a fixed factor while microsite and identity of each plant individual or bare soil were included as random factors because soil samples collected from the same individual or bare soil were closer to each other than they were to the other samples.
If two or more models had the same AIC i. A Poison distribution of errors was specified for germination time, and a binomial distribution of errors was specified for seedling mortality. Pot was included as random factor in each model. An observation-level random effect was included to account for overdispersion in emergence timing Harrison All statistical analyses were performed with R software R Core Team GLMMs were performed using the glmer function in the lme4 package Bates et al.
ARTEMISIA HERBA ALBA ASSO PDF
Artemisia pontica Roman wormwood Artemisia arborescens tree wormwood, or sheeba in Arabic is an aromatic herb indigenous to the Middle East used in tea, usually with mint. A few species are grown as ornamental plants , the fine-textured ones used for clipped bordering. All grow best in free-draining sandy soil, unfertilized, and in full sun. Artemisia stelleriana is known as Dusty Miller, but several other species bear that name, including Jacobaea maritima syn. Senecio cineraria , Silene coronaria syn. Lychnis coronaria , and Centaurea cineraria.
Artemisia herba-alba Asso. in diabetes mellitus.
Names[ edit ] Its specific epithet herba-alba means "white herb" in Latin , as its stems and leaves are white and woolly. Leaves are strongly aromatic and covered with fine glandular hairs that reflect sunlight giving a grayish aspect to the shrub. The leaves of sterile shoots are grey, petiolate , ovate to orbicular in outline; whereas, the leaves of flowering stems, more abundant in winter, are much smaller. The plant flowers from September to December. Mainly, eudesmanolides and germacranolides types were reported in most cases. Please review the contents of the section and add the appropriate references if you can. Unsourced or poorly sourced material may be challenged and removed.
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