Weed invasion of milled-over bog

In Ireland, about 90 000 ha of midland bog are being subjected to peat harvesting, principally by surface milling operations. Immediately after milling, the bog surface is free of plants and seeds. The invasion by plants of such surfaces, which have been left idle for periods of 1–12 years and which are adjacent to a peatland experimental farm, is described. The significance of such colonization for weed infestation of any subsequent crops grown on the area is inferred from data on weed proliferation on the experimental farm which has produced principally horticultural crops. Sixty-seven species of flowering plants, of which 39 are potential weeds, were recorded on the milled-over areas. This is in contrast with only 12 weed species on the experimental farm after 10 years of cropping although that number has grown to 52 species after 25 years. The farm functions as a seed source for the surrounding milled-over bog, but it is not the sole source of supply, as potential weeds (Sinapis arvensis, Veronica hederifolia) not found on the farm have been found on the bog. Wind appears to be the principal transport agency for invading species. Polygonum lapathifolium, which is dependent on flood-waters or on man for transport, is a major weed on the farm, but was not found on the milled-over bog. Tussilago farfara is much more evident on the milled areas examined than it was on the site of the farm before crop production began and than it is on the farm in 1984. Invasion de marais tourbeux par les mauvaises herbes après broyage En Irelande, environ 90 000 ha de marais au centre du pays subissent des opérations de tour-bage, surtout par broyage de la surface. Tout de suite après le broyage, la surface du marais se trouve indemne de plantes et de graines. Les auteurs décrivent l'invasion par des plantes de certaines surfaces contigues à une ferme tourbière expérimentale, après une période sans utilisation allant d'une à 12 années. A partir de données sur la prolifération des mauvaises herbes dans la ferme expérimentale, consacrée surtout à des cultures maraîcheres, ils considèrent si une telle colonisation est significative en ce qui concerne l'enherbement de cultures implantées ultérieurement sur ces surfaces. Soixante-sept espèces de plantes à fleurs, dont 39 éventuellement des adventices, ont été signalées sur les surfaces broyées. Par contre, la ferme expérimentale n'a produit que douze espèces adventices au bout de 10 ans de cultures; cependant au bout de 25 ans on a signalé 52 espèces de mauvaises herbes. La ferme fournit des graines aux marais broyés environnants mais elle n'en constitue pas la source unique, puisque certaines espèces éventuellement adventices (Sinapis arvensis, Veronica hederifolia) qu'on ne trouve pas à la ferme ont paru sur le marais. C'est surtout le vent, parait-il, qui véhicule les espèces envahissantes. Polygonum lapathifolium, espèce qui dépend d'inondations ou de l'homme pour véhiculer ses graines, est une mauvaise herbe importante à la ferme, mais n'a pas été signalé sur le marais broyé. Tussilago farfara se trouve sur les surfaces broyées en plus grand nombre que sur l'emplacement de la ferme avant l'introduction des cultures; en 1984 il est toujours moins abondant sur la ferme. Unkrautbesiedelung von oberflächlich gefrästen Torfflächen In Irland werden gegenwärtig ca. 90 000 ha Sumpfböden der mittleren Landesteile durch oberflächliche Bearbeitung mit Bodenfräsen zur Torfgewinnung genutzt. Unmittelbar nach dem Fräsen ist die Bodenoberfläche frei von Pflanzen und Samen. Die pflanzliche Besiedelung solcher, während einem bis zu zwölf Jahren sich selbst überlassenen und an eine Versuchsfarm angrenzenden Flächen ist Gegenstand vorliegender Untersuchung. Die Entwicklung der Unkrautpopulation in einer später darauf angebauten Kultur wird von der Unkrautflora der benachbarten, hauptsächlich Gartenbau betreibenden Versuchsfarm beeinflusst. 67 Blütenpflanzen, wovon 39 potentielle Unkräuter, wurden in den früher gefrästen Arealen festgestellt. Diese Beobachtung steht in Kontrast zu nur 12 Unkrautarten auf der Versuchsfarm nach zehn Jahren gärtnerischer Nutzung; allerdings stieg die Artenzahl auf 52 nach fünfundzwanzig Jahren. Die Farm wirkt als Unkrautquelle für die sie umgebenden Torfflächen; sie stellt aber nicht die einzige Quelle dar, da potentielle Unkräuter (Sinapis arvensis, Veronica hederifolia) vorgefunden wurden, die auf der Versuchsfarm fehlten. Es seheint, dass der Wind das wichtigste Transportmittel für einwandernde Arten darstellt. Polygonum lapathifolium, zur Verbreitung auf den Menschen oder fliessendes Wasser angewiesen, ist auf der Farm ein wichtiges Unkraut, wurde jedoch in der Umgebung nicht festgestellt. Tussilago farfara tritt auf den gefrästen Torfflächen viel stärker auf, als dies vor Aufnahme der gärtnerischen Produktion auf der Farm, aber auch 1984 der Fall war.     

Sampling for adults of the planthopper Myndus crudus a vector of lethal yellowing of palms 1

Abstract

Tests were made using coloured sticky traps to determine trap efficacy in catching adult Myndus crudus Van Duzee (Homoptera, Cixiidae) under field conditions. Blue traps caught more M. crudus adults than any of the other colour traps tested. Blue traps caught adults of both sexes during the day and night although significantly more adults were caught during the day. A sampling bias was shown in that blue traps caught significantly more males than expected from the field population. Blue sticky traps were more effective at sampling adult M. crudus populations than previous sampling techniques based on host plant attractiveness and should be considered for use in future sampling.     

SOIL ATTRIBUTES AFTER THE CONVERSION FROM FOREST TO PASTURE IN AMAZON

The conversion from forest to grassland is drastically changing soil characteristics in Amazon, leading to land degradation when it is poorly managed. Chemical and physical changes of a Typic Hapludox were evaluated as a function of the conversion (by means of fire) from forest to Brachiaria brizantha cultivation. Samples from the remaining forest were also sampled. Treatments were made to pastures eight (P8), thirteen (P13) and fifteen (P15) years after conversion, and to land under continuous grazing, and to a remaining forest area (control). The forest soil was more acidic than the pasture soils. Soil density and Ca⁺² increased after the conversion, regardless of the period of grazing. Carbon stocks varied from 31·2 t ha⁻¹ in the forest soil to 37·4 (P8), 33·5 (P13) and 30·7 t ha⁻¹ (P15). Copyright © 2011 John Wiley & Sons, Ltd.     

Rhodophyta Seaweed Species as Bioindicators for Monitoring Toxic Element Pollutants in the Marine Ecosystem of Ghana

Six seaweed species of the Rhodophyta family were sampled for atwo-year period from June 1996 to August 1998 along the Atlanticcoast of Ghana (part of the Atlantic Ocean). The species wereanalysed to determine the levels of eleven chemicalelements namely: Al, As, Br, Cd, Fe, La, Mn, Ni, Hg, V and Zn byInstrumental Neutron Activation Analysis (INAA). Al, Br, Ni, andZn were measured in all the seaweed species studied. The elementAl generally showed the highest concentrations in most of thespecies analysed while Hg levels were the lowest. Precision andaccuracy of the method have been evaluated and the detectionlimits also calculated. The results showed high variability inand between species, among sampling sites and times ofcollection. The high values of metal concentrations in themacroalgae suggest that these marine organisms can be used asbiological indicators for studing marine pollution.     

Dispersal potentials determine responses of woody plant species richness to environmental factors in fragmented Mediterranean landscapes

While maximizing plant species richness continues to be central in the design, conservation and reforestation action plans, plant life histories are receiving increasing attention in assessments for the conservation of biodiversity in fragmented landscapes. We investigated the determinants of woody plant species (trees, shrubs and climbers) richness in the forest patches of the Guadalquivir river valley, a Mediterranean agricultural landscape with ∼1% forest cover. We analyzed three species richness variables, total, and those corresponding to species with short-distance (ballistic, barochorous, myrmecochorous and short-distance anemochorous) and long-distance (anemochorous, endozochorous, exozoochorous, hydrochorous and dyszoochorous) dispersal systems, which significantly characterize earlier and late successional stages, respectively. We selected eleven predictor variables related to habitat structure (patch area, shape, distances to the nearest patch and reserve, and general isolation), physical environment (temperature, precipitation, elevation, and lithological heterogeneity), and anthropogenic influences (disturbance and proportion of old-growth forest). We used ordinary-least-squares multiple regression (OLS) and the Akaike's information criterion (corrected for spatial autocorrelation) and derived indices to generate parsimonious models including multiple predictors. These analyses indicated that plant species richness increase primarily along with increasing patch area and decreasing disturbance, but also detected secondary effects of other factors when dispersal was considered. While the number of species with potential long-distance dispersal tended to increase in more isolated patches of areas with greater precipitation and lithological heterogeneity (e.g. highlands at the valley edges), the number of species with short-distance dispersal increased towards drier and less lithologically complex zones with shorter between-patch distances (e.g. central lowlands). Beyond emphasizing the need to consider dispersal in fragmentation studies, our results show that woody plant species richness would be favoured by actions that increase patch area and reduce anthropogenic disturbances particularly in lowland forests.