Swampy Meadows Research Articles

The characteristics of habitats colonized by three species ofLymnaea(Mollusca) in swampy meadows on acid soil : their interest for control of fasciolosis

lived in the central ditch. The mean area of L. truncatula habitats ranged from 2.8 to 4.8 m2 in relation to the district studied and was smaller than those of L. glabra (a mean of 3.6 to 7.2 m2 ) and L. palustris (10.3 to 19.3 m2). Mean intervals between the sites occupied by L. truncatula and L. glabra ranged from 6.3 to 12.3 m ; they were greater between the sites occupied by L. glabra and L. palustris (11.6 to 15.4 m). Finally, the mean densities of L. truncatula in June ranged from 11.4 to 19.8/m 2 in relation to the district studied ; those of L. glabra ran­ ged from 22.6 to 27.0 snails/m2, whereas in L. palustris, they ranged from 6.3 to 8.8 snails/m2. The mean values of these first two parameters were significantly lower in the habitats located in Monts d'Ambazac than those recorded in the two other districts. Im­ plications of these results for fasciolosis control are discussed. '

Holocene valley aggradation and gully erosion in headwater catchments, south‐eastern highlands of Australia

AbstractLate Quaternary stratigraphy of a 50 km2 catchment on the south‐eastern highlands of Australia reveals processes and history of denudation, and helps resolve a long‐standing debate about factors controlling episodic valley aggradation and degradation during Holocene times. Valley sedimentation occurred when swampy vegetation fully colonized valley floors and obliterated all channels, promoting aggradation for periods of several thousand years, with most incoming sediment being trapped in swampy meadows. Much of the sediment was reworked from late Pleistocene alluvial fan and valley fill deposits, and primary hillslope erosion was minor during the Holocene. Differing sedimentation patterns between the Late Pleistocene, Holocene and Post‐European settlement periods reflect regional changes in sediment supply and transport capacity as a result of major environmental change. Within the Holocene, however, valley fill stratigraphy is controlled by massive, episodic gully erosion terminating aggradation. Gully initiation appears to be controlled more by thresholds of incision into vegetated valley floors than by changes to sediment supply. Whether the thresholds are exceeded because of climatic change, autonomous change or extreme events cannot yet be determined. Overall, the Holocene history represents continuing complex response to events of the Late Pleistocene, and does not support the K‐cycle concept, which has strongly influenced late Quaternary geomorphology in Australia.

Influence sur l’avifaune nicheuse de l’utilisation agricole et des opérations de drainage des marais de l’Ouest

In the 300 km2 of coastal wetlands around Rochefort and Brouage, western France, the remaining swampy meadows are drained and progressively replaced by croplands. Consequently, there is a decrease in species richness, diversity, and population density of the breeding birds community. The study here reported points out that preserving the ditches in former marshland, together with the former basins of the old salt marshes, allows the preservation of a diverse marsh birds community, even in the middle of intensively cultivated areas. The key factor for the maintenance of both marsh passerines’ and harrier’s breeding populations is the maintenance of adequate reedbed cover.

Die Sumpfwiesen Transdanubiens, Ungarn

Die Sumpfwiesen Transdanubiens, Ungarn