Fine-scale patterns of genetic variation in a widespread clonal seagrass species

Seagrasses are ecosystem engineers that offer important habitat for a large number of species and provide a range of ecosystem services. Many seagrass ecosystems are dominated by a single species, with research showing that genotypic diversity at fine spatial scales plays an important role in maintaining a range of ecosystem functions. However, for most seagrass species, information on fine-scale patterns of genetic variation in natural populations is lacking. In this study, we use a hierarchical sampling design to determine the levels of genetic and genotypic diversity at different spatial scales (centimeters, meters, kilometers) in the Australian seagrass Zostera muelleri. Our analysis shows that at fine spatial scales (<1 m), levels of genotypic diversity are relatively low (R(Plots) = 0.37 ± 0.06 SE), although there is some intermingling of genotypes. At the site (10’s m) and meadow location (km) scale, we found higher levels of genotypic diversity (R(sites) = 0.79 ± 0.04 SE; R(Locations) = 0.78 ± 0.04 SE). We found some sharing of genotypes between sites within meadows, but no sharing of genotypes between meadow locations. We also detected a high level of genetic structuring between meadow locations (FST = 0.278). Taken together, our results indicate that both sexual and asexual reproductions are important in maintaining meadows of Z. muelleri. The dominant mechanism of asexual reproduction appears to occur via localized rhizome extension, although the sharing of a limited number of genotypes over the scale of 10’s of meters could also result from the localized dispersal and recruitment of fragments. The large number of unique genotypes at the meadow scale indicates that sexual reproduction is important in maintaining these populations, while the high level of genetic structuring suggests little gene flow and connectivity between our study sites. These results imply that recovery from disturbances will occur through both sexual and asexual regeneration, but the limited connectivity at the landscape scale implies that recovery at meadow-scale losses is likely to be limited.

Recovery pathways from small-scale disturbance in a temperate Australian seagrass

Recovery from disturbance is a key element of ecosystem persistence, and recovery can be influenced by large-scale regional differences and smaller local-scale variations in environmental conditions. Seagrass beds are an important yet threatened nearshore habitat and recover from disturbance by regrowth, vegetative extension and dispersive propagules. We described recovery pathways from small-scale disturbances in the seagrass Zostera nigricaulis in Port Phillip Bay, a large embayment in southeastern Australia, and tested whether these pathways differed between 5 regions with different hydrodynamic conditions and water quality, and between sites within those regions. Recovery pathways were broadly consistent. When aboveground biomass was removed, recovery, defined as the point at which disturbed areas converged with undisturbed controls, took from 2 to 8 mo, but when we removed above-and below-ground biomass, it took between 2 and 13 mo. There was no evidence of recovery resulting from sexual reproduction at any sites regardless of the presence of seeds in the sediment or flower production. We found no differences in recovery at the regional scale, but we found substantial differences between local sites. At some sites, rapid recovery occurred because seagrasses grew quickly, but at others, apparent recovery occurred because regrowth coincided with overall declines in cover of undisturbed areas. Recovery time was unrelated to seagrass canopy height, biomass, percentage cover, stem density, seed bank density, epiphyte cover or sediment organic matter in seagrass adjacent to disturbance experiments. This study highlights the importance of understanding fine-scale variation in local recovery mechanisms, which may override or obscure any regional signal.

Variability of sedimentary organic carbon in patchy seagrass landscapes

Seagrass ecosystems, considered among the most efficient carbon sinks worldwide, encompass a wide variety of spatial configurations in the coastal landscape. Here we evaluated the influence of the spatial configuration of seagrass meadows at small scales (metres) on carbon storage in seagrass sediments. We intensively sampled carbon stocks and other geochemical properties (δ(13)C, particle size, depositional fluxes) across seagrass-sand edges in a Zostera muelleri patchy seagrass landscape. Carbon stocks were significantly higher (ca. 20%) inside seagrass patches than at seagrass-sand edges and bare sediments. Deposition was similar among all positions and most of the carbon was from allochthonous sources. Patch level attributes (e.g. edge distance) represent important determinants of the spatial heterogeneity of carbon stocks within seagrass ecosystems. Our findings indicate that carbon stocks of seagrass areas have likely been overestimated by not considering the influence of meadow landscapes, and have important relevance for the design of seagrass carbon stock assessments.

Fluxo da água subterrânea em sistema de encosta-rio, município de Paulínia (SP): caracterização hidrogeológica e simulação numérica

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Supplementation based on protein or energy ingredients to beef cattle consuming low-quality cool-season forages: I. Forage disappearance parameters in rumen-fistulated steers and physiological responses in pregnant heifers

Two experiments evaluated the influence of supplement composition on ruminal forage disappearance, performance, and physiological responses of Angus x Hereford cattle consuming a low-quality cool-season forage (8.7% CP and 57% TDN). In Exp. 1, 6 rumen-fistulated steers housed in individual pens were assigned to an incomplete 3 x 2 Latin square design containing 2 periods of 11 d each and the following treatments: 1) supplementation with soybean meal (PROT), 2) supplementation with a mixture of cracked corn, soybean meal, and urea (68:22:10 ratio, DM basis; ENER), or 3) no supplementation (CON). Steers were offered meadow foxtail (Alopecurus pratensis L.) hay for ad libitum consumption. Treatments were provided daily at 0.50 and 0.54% of shrunk BW/steer for PROT and ENER, respectively, to ensure that PROT and ENER intakes were isocaloric and isonitrogenous. No treatment effects were detected on rumen disappearance parameters of forage DM (P >= 0.33) and NDF (P >= 0.66). In Exp. 2, 35 pregnant heifers were ranked by initial BW on d -7 of the study, allocated into 12 feedlot pens (4 pens/treatment), and assigned to the same treatments and forage intake regimen as in Exp. 1 for 19 d. Treatments were fed once daily at 1.77 and 1.92 kg of DM/heifer for PROT and ENER, respectively, to achieve the same treatment intake as percent of initial BW used in Exp. 1 (0.50 and 0.54% for PROT and ENER, respectively). No treatment effects (P = 0.17) were detected on forage DMI. Total DMI was greater (P < 0.01) for PROT and ENER compared with CON and similar between PROT and ENER (P = 0.36). Accordingly, ADG was greater (P = 0.01) for PROT compared with CON, tended to be greater for ENER compared with CON (P = 0.08), and was similar between ENER and PROT (P = 0.28). Heifers receiving PROT and ENER had greater mean concentrations of plasma glucose (P = 0.03), insulin (P <= 0.09), IGF-I (P <= 0.04), and progesterone (P = 0.01) compared to CON, whereas ENER and PROT had similar concentrations of these variables (P >= 0.15). A treatment x hour interaction was detected (P < 0.01) for plasma urea N (PUN), given that PUN concentrations increased after supplementation for ENER and PROT (time effect, P < 0.01) but did not change for CON (time effect, P = 0.62). In conclusion, beef cattle consuming low-quality cool-season forages had similar ruminal forage disappearance and intake, performance, and physiological status if offered supplements based on soybean meal or corn at 0.5% of BW.

NDVI and vegetation phenology dynamics under the influence of sunshine duration on the Tibetan plateau

Climate change has significantly influenced vegetation dynamics on the Tibetan Plateau (TP). Past research mainly focused on vegetation responses to temperature variation and water stress, but the influence of sunshine duration on NDVI and vegetation phenology on the TP is not well understood. In this study, NDVI time series from 1982-2008 were used to retrieve spatiotemporal vegetation dynamics on the TP. Empirical orthogonal function (EOF) analysis was conducted to understand the spatiotemporal variations of NDVI. The Start of Season (SOS) was estimated from NDVI time series with a local threshold method. The first EOF, accounting for 35.1% of NDVI variations on the TP, indicates that NDVI variations are larger in areas with shorter sunshine duration. The needle-leaved forest and shrub in the southeastern TP are more sensitive to sunshine duration anomalies (p < 0.01) than broad-leaved forest, steppe, and meadow due to spatial and altitudinal distribution of sunshine duration and vegetation types. The decrease in sunshine duration for the growing season on the TP has resulted in a decreased NDVI trend in some areas of southeastern TP (p ranging from 0.32-0.05 with threshold ranging from 0.05 to 0.25) in spite of the overall NDVI increase. SOS dynamics in most parts of the TP were mainly related to temperature variability, with precipitation and sunshine duration playing a role in a few regions. This study enhances our understanding of vegetation responses to climatic change on the TP.

Comparison of Botanical Composition, Soil Carbon Content, and Root Distribution of Subirrigated Meadows in The Nebraska Sandhills

Characterizing vegetation composition, carbon/nitrogen (C/N) content of soils, and root-mass distribution is critical to understanding carbon sequestration potential of subirrigated meadows in the Nebraska Sandhills. Five subirrigated meadows dominated by cool-season (C3) graminoids and five meadows dominated by warm-season (C4) grasses were selected throughout the Nebraska Sandhills. Vegetation, soil carbon and nitrogen, and root-mass density distribution were sampled in each meadow. Meadows dominated by C3 vegetation had 12% greater (P < 0.1) yields than meadows dominated by C4 vegetation. Total root-mass density was 30% greater (P < 0.1) in C4-dominated meadows than C3-dominated meadows. Total carbon and nitrogen content was 65% and 53% greater (P < 0.1), respectively, in the A horizon of C3-dominated meadows, but was 43% and 52% greater (P < 0.1), respectively, in the C horizon of C4-dominated meadows. Although meadows dominated by C3 vegetation had more carbon in the soil profile, much of the carbon in C3-dominated meadows appeared to be recalcitrant C4 carbon from historic vegetation.

Streptomyces brevispora sp nov and Streptomyces laculatispora sp nov., actinomycetes isolated from soil

The taxonomic positions of two actinomycetes isolated from a hay meadow soil sample were determined using a polyphasic approach. The isolates had chemical and morphological properties typical of streptomycetes and formed a distinct 16S rRNA gene subclade together with the type strain Streptomyces drozdowiczii NRRL B-24297(T). DNA DNA relatedness studies showed that the three strains belonged to different genomic species. The organisms were also distinguished using a combination of phenotypic properties. On the basis of these data it is proposed that the isolates be assigned to the genus Streptomyces as Streptomyces brevispora sp. nov. and Streptomyces laculatispora sp. nov., with BK160(T) (=KACC 21093(T) =NCIMB 14702(T)) and BK166(T) (=KACC 20907(T) =NCIMB 14703(T)) as the respective type strains.

Gradients in the number of species at reef-seagrass ecotones explained by gradients in abundance

[EN] Gradients in the composition and diversity (e.g. number of species) of faunal assemblages are common at ecotones between juxtaposed habitats. Patterns in the number of species, however, can be confounded by patterns in abundance of individuals, because more species tend to be found wherever there are more individuals. We tested whether proximity to reefs influenced patterns in the composition and diversity (‘species density’ = number of species per area and ‘species richness’ = number of species per number of individuals) of prosobranch gastropods in meadows of two seagrasses with different physiognomy: Posidonia and Amphibolis. A change in the species composition was observed from reef-seagrass edges towards the interiors of Amphibolis, but not in Posidonia meadows. Similarly, the abundance of gastropods and species density was higher at edges relative to interiors of Amphibolis meadows, but not in Posidonia meadows. However, species richness was not affected by proximity to reefs in either type of seagrass meadow. The higher number of species at the reef-Amphibolis edge was therefore a consequence of higher abundance, rather than species richness per se. These results suggest that patterns in the composition and diversity of fauna with proximity to adjacent habitats, and the underlying processes that they reflect, likely depend on the physiognomy of the habitat.

Ichthyofauna associated with Cymodocea nodosa meadows in the Canarian Archipelago (central eastern Atlantic): Community structure and nursery role

We carried out 84 trawls in 41 seagrass meadows composed of the phanerogam Cymodocea nodosa at three islands of the Canarian Archipelago, during June to September 2003, in order to describe the associated ichthyofauna (composition, richness, and abundance), to analyze the role that this habitat can play in fish recruitment, and to determine the potential relationship between the spatial structure of the seagrass meadow and the patterns of richness and abundance of the fish assemblage. A total of 8298 individuals were captured. The five most relevant species, in terms of abundance and frequency, were Spondyliosoma cantharus, Diplodus annularis, Syngnathus typhle, Mullus surmuletus, and Pagellus erythrinus. Gran Canaria had the largest species richness (36 species) and mean number of species per sample (8.69 ± 0.49; mean ± SE). Lanzarote had the largest number of individuals (64.83% of the total registered) and mean total abundance per sample (168.39 ± 30.91). High densities of individuals were registered (95.86 ± 13.5) and 92.91% of fishes were juveniles. Our data showed that the physical configuration of the seagrass meadows did not significantly affect the patterns of richness and abundance of the associated fish assemblage. In conclusion, the C. nodosa meadows exhibited a singular ichthyofauna and they contribute to the maintenance of the diversity of the coastal fish assemblages in the Canarian Archipelago. This habitat constitutes, during spring and summer, a nursery habitat for juvenile fishes of many species, several of them commercially targeted.

Decadal changes in the structure of Cymodocea nodosa seagrass meadows: natural vs. human influences

[EN] Seagrass meadows are deteriorating worldwide. However, numerous declines are still unreported, which avoid accurate evaluations of seagrass global trends. This is particularly relevant for the western African coast and nearby oceanic archipelagos in the eastern Atlantic. The seagrass Cymodocea nodosa is an ecological engineer on shallow soft bottoms of the Canary Islands. A comparative decadal study was conducted in 21 C. nodosa seagrass meadows at Gran Canaria Island to compare the structure (shoot density, leaf length and cover) between 2003 and 2012. Overall, 11 meadows exhibited a severe regression, while 10 remained relatively stable. During this period, natural influences (sea surface temperature, Chlorophyll-a concentration and PAR light, as well as the number of storm episodes detaching seagrasses) had a low predictive power on temporal patterns in seagrass structure. In contrast, proximity from a range of human-mediated influences (e.g. the number of outfalls and ports) seem to be related to the loss of seagrass; the rate of seagrass erosion between 2003 and 2012 was significantly predicted by the number of human-mediated impacts around each meadow. This result highlights promoting management actions to conserve meadows of C. nodosa at the study region through efficient management of local impacts

Temporal patterns of the seagrass "Cymodocea nodosa" and depth-related patterns of the green algae "Caulerpa prolifera" in the Canarian Archipelago

Máster Oficial en Gestión Costera

Die Entwicklung der Mesofauna eines Weinberges im nordöstlichen Rheinhessen im Vergleich zum Lennebergwald und weiteren Agrarflächen

ZusammenfassungrnrnrnDer Köderstreifentest, die Auswertung der Minicontainer und die Erfassung der Bodenlebewesen mit Hilfe der Bodenstechkerne ergeben zusammen eine gut standardisierte Methode zur Darstellung und Beurteilung der Mesofauna. Unter der Vorraussetzung gleicher abiotischer Faktoren ist es problemlos möglich, selbst unterschiedliche Standorte wie Agrarflächen, Weinberge und Waldböden vergleichend zu untersuchen.rnrnAuf den verschiedenen Versuchsflächen des Laubenheimer Weinberges gelingt es deutlich zu zeigen, wie wichtig eine naturnahe Begrünung für den Boden ist. Dies betrifft nicht nur die Entwicklung der Humusschicht und damit die Bodenlebewesen, sondern auch die Schaffung von Kapillaren und Poren, die durch schwere landwirtschaftliche Geräte im Rahmen der Bo-denverdichtung reduziert werden. Erosionserscheinungen kommen vollständig zum Stillstand. Das Ökosystem Boden sollte auch so gut wie keine Belastung durch Herbizide, Insektizide und Pestizide erfahren. Ähnliches gilt auch für agrarisch genutzte Flächen. rnrnDer Lennebergwald als Naherholungsregion von Mainz ist besonders schützenswert, da dieser durch intensiven Immissionseintrag aufgrund der Nähe zu den Autobahnen und durch die Eutrophierung über die Haustiere stark belastet wird. Die immer größere Ausdehnung des Siedlungsgebietes und die damit verbundene steigende Anzahl an Waldbesuchern, die durch Verlassen der vorgegebenen Wege den Boden zerstören, gefährden zusätzlich das Ökosystem.rnrnÜber Sinn und Zweck einer Flurbereinigung zu diskutieren ist hier nicht angebracht. Aus bo-denkundlicher Sicht ist sie nicht zu befürworten, da hiermit alle bodenbewahrenden Maßnah-men ignoriert werden. Wichtig ist es, bei den Landwirten Aufklärungsarbeit zu leisten, was bodenschonende und bodenweiterentwickelnde Bearbeitungsmethoden bedeuten. Mit Hilfe sachgemäßer Aufklärung und richtiger Umsetzung kann durch Begrünungsmaßnahmen der zum Teil sehr stark strapazierte Boden erhalten, gefördert und auf lange Sicht stabilisiert wer-den.rnrnAufgrund der festgestellten Tatsachen wurde ab 2008 auf eine flächige Dauerbegrünung um-gestellt, so dass es auch in den unbegrünten Rebzeilen zu einer Bodenverbesserung kommen kann. Mit großer Wahrscheinlichkeit dürfte diese schneller voranschreiten, da die Mesofauna von den benachbarten begrünten Rebzeilen einwandern kann. rnDie Mesofauna landwirtschaftlich genutzter Flächen und Waldgebiete kann, obwohl extrem unterschiedlich, miteinander verglichen werden.rnrnBrachflächen und Waldgebiete lassen sich aufgrund der unberührten Bodenstrukturen sogar gut miteinander vergleichen. Temperatur- und Niederschlagsverhältnisse müssen dabei über-einstimmen. Die Azidität der jeweiligen Böden gilt es zu berücksichtigen, da verschiedene Tiergruppen damit unterschiedlich umgehen. Collembolen bevorzugen neutrale Böden, wäh-rend Acari als Räuber mit den Lebewesen in sauren Böden besser zurechtkommen. Die Streu-auflage ist dabei von großer Bedeutung.rnrnIm Rahmen von Bearbeitungsmaßnahmen kommt es durch jeglichen Maschineneinsatz zu ei-ner mehr oder weniger starken Veränderung der Bodenstruktur und somit auch der darin le-benden Mesofauna. Bis sich diese erholt hat, steht meist schon die nächste Bodenbewirtschaf-tung an. Die Bodenverdichtung spielt auch eine Rolle. Bei herkömmlichem Ackerbau ist eine Fruchtfolge mit eingeschalteter Brache oder Gründüngung mit Klee oder Luzerne angebracht, um die Mesofauna nicht zu stark zu strapazieren. Organische Düngegaben leicht abbaubarer Streu sind deutlich zu bevorzugen gegenüber sehr zellulose- und ligninhaltigen Pflanzenresten. Die Einbringung von Stoppeln nach Aberntung von Getreidefeldern ist sinnvoll, solange dabei nicht zu tief in die Bodenstruktur eingegriffen wird (ZIMMER 1997).rnrnIm Rahmen der Sonderkultur Wein, bei der eine Bodenbearbeitung aus den aufgezeigten Gründen eigentlich nicht notwendig wäre, sind Dauerbegrünungsmaßnahmen generell von Nutzen: der Erosion wird vorgebeugt, die Bodenfeuchte konstant gehalten, der anfallende Mulch als Gründüngung genutzt. Dies sind alles entscheidende Faktoren, die die Meso- und Makrofauna fördern. Nur die Bodenverdichtung durch schweres Gerät, wie Schlepper und Vollernter, sind für den Boden nicht förderlich (HEISLER 1993, EHRENSBERGER 1993). Nie-derdruckreifen und Verringerung der Befahrung sind geeignete Gegenmaßnahmen. rnrnEntgegen landläufiger Winzermeinung, stellen die Pflanzen einer Begrünung eigentlich keine Konkurrenz für die Weinstöcke dar. Die Vorteile einer Begrünung sind nicht nur die Förde-rung der einheimischen Flora in ihrem standortgerechten Artenreichtum, sondern auch Ver-vielfältigung von Meso- und Makrofauna aufgrund der dadurch mehr anfallenden und ein-zuarbeitenden leicht abbaubaren Streu (GRIEBEL 1995).rn

Does delaying the first mowing date benefit biodiversity in meadowland?

Background Meadows are regularly mown in order to provide fodder or litter for livestock and to prevent vegetation succession. However, the time of year at which meadows should be first mown in order to maximize biological diversity remains controversial and may vary with respect to context and focal taxa. We carried out a systematic review and meta-analysis on the effects of delaying the first mowing date upon plants and invertebrates in European meadowlands. Methods Following a CEE protocol, ISI Web of Science, Science Direct, JSTOR, Google and Google Scholar were searched. We recorded all studies that compared the species richness of plants, or the species richness or abundance of invertebrates, between grassland plots mown at a postponed date (treatment) vs plots mown earlier (control). In order to be included in the meta-analysis, compared plots had to be similar in all management respects, except the date of the first cut that was (mostly experimentally) manipulated. They were also to be located in the same meadow type. Meta-analyses applying Hedges’d statistic were performed. Results Plant species richness responded differently to the date to which mowing was postponed. Delaying mowing from spring to summer had a positive effect, while delaying either from spring to fall, or from early summer to later in the season had a negative effect. Invertebrates were expected to show a strong response to delayed mowing due to their dependence on sward structure, but only species richness showed a clearly significant positive response. Invertebrate abundance was positively influenced in only a few studies. Conclusions The present meta-analysis shows that in general delaying the first mowing date in European meadowlands has either positive or neutral effects on plant and invertebrate biodiversity (except for plant species richness when delaying from spring to fall or from early summer to later). Overall, there was also strong between-study heterogeneity, pointing to other major confounding factors, the elucidation of which requires further field experiments with both larger sample sizes and a distinction between taxon-specific and meadow-type-specific responses.

Recruitment limitation constrains local species richness and productivity in dry grassland

Species coexistence and local-scale species richness are limited by the availability of seeds and microsites for germination and establishment. We conducted a seed addition experiment in seminatural grassland at three sites in southern Switzerland and repeated the experiment in two successive years to evaluate various circumstances under which seed limitation and establishment success affect community functioning. A collection of 144000 seeds of 22 meadow species including grasses and forbs of local provenance was gathered, and seeds were individually sown in a density that resembled natural seed rain. The three communities were seed limited. Three years after sowing, single species varied in emergence (0–50%), survival (0–69%), and establishment rates (0–27%). One annual and 13 perennial species reached reproductive stage. Low establishment at one site and reduced growth at another site indicated stronger microsite limitation compared to the third site. Recruitment was influenced by differences in abiotic environmental conditions between sites (water availability, soil minerals) and by within-site differences in biotic interaction (competition). At the least water-limited site, sowing resulted in an increase in phytomass due to establishment of short-lived perennials in the second and third years after sowing. This increase persisted over the following two years due to establishment of longer-lived perennials. After sowing in a wetter year with higher phytomass, however, productivity did not increase, because higher intensity of competition in an early phase of establishment resulted in less vigorous plants later on. Due to the generally favorable weather conditions during this study, sowing year had a small effect on numbers of established individuals over all species. Recruitment limitation can thus constrain local-scale species richness and productivity, either by a lack of seeds or by reduced seedling growth, likely due to competition from the established vegetation.