The relation between the flooding regime and the distribution particularly of Pulegium vulgare Miller

This paper describes the reaction of Pulegium vulgare and a number of species from the same locality upon the different flooding regimes of four consecutive years. These species mainly belong to the Lolio-Cynosuretum and the Ranunculo-Alopecuretum. The results show that the effect of a flood on the vegetation strongly depends on the month (the date of the year) during which the inundation occurs. A flood of shorter duration in late summer has a stronger impact than a longer inundation in spring and early summer. Pulegium vulgare strongly decreased after being flooded in July and August and did not recover in the subsequent year. On account of the behaviour of the species after a summer inundation, seven groups were broadly distinguished.Die Arbeit beschreibt die Reaktion von Pulegium vulgare und einiger anderer Arten derselben Lokalität auf Überschwemmungen in aufeinander folgenden Jahren. Die Arten gehören hauptsächlich zum Lolio-Cynosuretum und Ranunculo-Alopecuretum. Die Ergebnisse zeigen, dass die Wirkung einer Überschwemmung auf die Vegetation stark vom Datum derselben abhängt. Eine kurze Überschwemmung im späten Sommer hat eine stärkere Wirkung als eine längere Überschwemmung im Frühling oder im frühen Sommer. Pulegium vulgare ging nach einer Überflutung im Juli und August stark zurück und regenerierte sich im nächsten Jahr nicht. Auf Grund der Reaktion der Arten nach einer Überschwemmung im Sommer werden sieben Gruppen unterschieden

Aufzeichnungen zur Vegetation der schwedischen Inseln Öland, Gotland und Stora Karlsö

Einige Pflanzengesellschaften der schwedischen Ostsee-Inseln Gotland, Öland und Stora Karlsö werden besprochen und mit Tabellen erläutert. Sie beziehen sich auf "Änge" (Komplexe von Laubwald und Wiese), Nadelwälder auf Kalkboden bzw. auf Sand, Saumgesellschaften, Alvar (Helianthemo-Globularion und Alysso-Sedion), feuchte Wiesen und Weiden (Molinion und Lolio-Potentillion), Sümpfe und Gewässer (Caricion davallianae und Littorellion), Salzwiesen (Armerion maritimae), Stranddünen (Ammophiletalia und Festuco-Sedetalia), feuchte Dünentäler und Schwalben-Guano unter Felsrändern.Some plant communities of the Baltic Sea islands of Gotland, Oland and Stora Karlso are investigated and discussed. They concern Ange (mixed stands of deciduous woodland, fringes and meadows, representing an ancient agrarian practice), pine woodlands on limestone as well as on sand, woodland fringes, alvar (open, dry to damp limestone grasslands), damp meadows and pastures, swamps and pools, salt marshes, sea dunes, as well as a nitrophilous Asperugo community on swallow guano

Effect of Vachellia tortilis on understory vegetation, herbaceous biomass and soil nutrients along a grazing gradient in a semi-arid African savanna

The spatial pattern and abundance of herbaceous vegetation in semi-arid savannas are dictated by a complex and dynamic interaction between trees and grasses. Scattered trees alter the composition and spatial distribution of herbaceous vegetation under their canopies. Therefore, we studied the effect of Vachellia tortilis on herbaceous vegetation composition, biomass and basal area, and soil nutrients on sites with varying grazing intensities in the central rift valley of Ethiopia. Data were collected on species composition, cover and biomass of herbs and grasses, and soil moisture and nutrient contents under light, medium, and heavy grazing pressures, both under the inside and outside of V. tortilis canopies. Species richness was similar in both locations but decreased with increased grazing. Only the overall biomass and herb cover were significantly greater under the canopy than outside, and overall biomass showed significant unchanging decline with increased grazing. However, vegetation cover was significantly greater on moderately grazed sites compared to low and heavily grazed sites. All soil variables were significantly higher under V. tortilis canopies than outside. Our findings suggest that V. tortilis has more effect on composition and diversity of herbaceous vegetation than on species richness, and that V. tortilis promotes the herbaceous layer biomass by reducing soil moisture loss and increasing soil fertility under the inside than outside the canopies. Therefore, we suggest that management practices should be directed on reducing pressure on V. tortilis by regulating grazing. Low to moderate grazing levels (i.e., a stocking rate less than 39.6 TLU ha −1 yr −1 ) seems to be tolerable to ensure sustainable conservation of the species in the study area in particular and in semi-arid savannas in general

The role of livestock grazing in long-term vegetation changes in coastal dunes: a case study from the Netherlands

The vegetation of coastal sand dunes is characterized by high species diversity and comprises some of the rarest vegetation types in North-Western Europe. Among them are dune grassland communities whose species richness relies on grazing. Those communities are assessed as a priority habitat type under the Natura 2000 legislation. In autumn 1990, Galloway cows and Nordic Fjord horses were introduced in the coastal dunes of Meijendel near The Hague (52°7'N, 4°20'E), The Netherlands, to reduce encroachment of tall grasses and shrubs, to develop bare sand patches, and as such facilitating diverse vegetation structures in the dune grasslands. In the 1950s, decades before the introduction of livestock, 41 permanent plots were installed. On average, they were examined every four years. Our study hypothesised that the livestock grazing in the set densities would halt progressive succession and facilitate regressive succession. Up to 1990, we observed an equilibrium between progressive and regressive succession. After 1990, however, our data showed a pronounced progressive succession contradicting the hypothesized effect of the livestock grazing. We relate the main observed patterns with two factors linked to rabbit populations: (i) the myxomatosis outbreak in 1954 and (ii) the rabbit Viral Haemorrhagic Disease (rVHD-1) outbreak in 1989. In addition to livestock grazing, rabbits block progressive succession by feeding on seedlings of shrub and tree species and digging burrows, creating small-scale mosaics of bare sand and initiate blowout development when collapsing. We state that the substantial decrease in rabbit numbers due to the viral diseases likely caused the observed increase of shrubs and trees in the study area's permanent plots. Climate change might have contributed to the observed increase in autonomous blowout development since 2001, as well as a decrease in atmospheric nitrogen deposition since 1990, after a strong increase the decades before

Linking biochemical and biophysical variables derived from imaging spectrometers to ecological models - The HyEco'04 Group Shoot.

peer reviewe

Linking biochemical and biophysical variables derived from imaging spectrometers to ecological models - The HyEco'04 Group Shoot

We report on the first results of the HyEco'04 campaign carried out in summer 2004 as a joint activity of a bi-national team of Belgian and Dutch researchers. This integrated approach of assessing the complexity of managed natural ecosystems is a demonstrator case for recent focus of airborne imaging spectroscopy activities on ecotones. The floodplain Millingerwaard located east to the city of Nijmegen along the river Rhine has been chosen to demonstrate the potential of imaging spectrometer data to support ecological modelling. Several ground support teams supported the data acquisition of the Hymap sensor during its overflight on two days in July and August 2004. Field measurements concentrated on two approaches: first, radiometric measurements supporting the linking between soil-vegetation-atmosphere transfer modelling (e.g., sunphotometer, leaf optical properties measurements, canopy reflectance, structural parameter measurements (gap fraction, leaf angle distribution, leaf area index) have been performed and secondly supporting additional measurements on vegetation (species mapping, destructive biomass sampling) and soil (moisture, temperature) have been performed. First, we will report on the data quality evaluation of the various data sources and their integration into an integrated system, dealing with various aspects of spatial sampling schemes and potential spatial discontinuities, as well as uncertainty measures. Secondly, we discuss two examples of spatially distributed products derived from either ground based measurements and inventory mapping, extrapolated to the full coverage of the test site or imaging spectrometer derived products. The resulting products are discussed in view of potential incorporation into land-biosphere models, where high or even unknown uncertainty in input data, and limited availability of geographically explicit input data are usually the limiting factors for the application of ecological models on a larger spatial extent (e.g. national).status: publishe