Güsewell S., Zuberbühler N. and Clerc C. 2005. Distribution and functional traits of Solidago gigantea in a Swiss lakeshore wetland. Bot. Helv. 115: 63-75.Alien plant species are of particular ecological concern when they invade native vegetation of high conservation value and alter its functioning. We mapped the area and cover of stands of invasive alien species in the lakeshore wetland "Grande Cariçaie" (CH) and examined whether the main invader, Solidago gigantea Ait., differs functionally from the resident vegetation. Seven alien species considered to be invasive in Switzerland occurred with a total area of 22.2 ha. The most frequent invaders were S. gigantea (60 stands) and Robinia pseudoacacia (42 stands, mostly in forest). Less than 1% of the non-forested wetland area was colonised by alien species, mostly S. gigantea. Dense stands of S. gigantea (> 50% cover) occurred in mesotrophic, non-flooded vegetation, suggesting that its spread is limited by high water level rather than by low nutrient availability. S. gigantea appeared functionally similar to the invaded wetland vegetation: its shoot size, specific leaf area, and biomass N and P concentrations were similar to or lower than those of co-occurring native species. Total soil N and P concentrations under S. gigantea stands did not differ from those under non-invaded vegetation. Thus, the impact of invasive alien species on the non-forested wetlands of the Grande Cariçaie currently seems rather low but possible changes in soil processes as well as effects on other biota remain to be investigated.

Using environmental parameters we studied the distribution of two endangered species, Hydrocharis morsus-ranae L. and Rumex hydrolapathum Huds., in a low-lying marshland of the Swiss Plateau, a region in which aquatic vegetation is particularly threatened. A large part of the study site is regularly mown by a machine for site management purposes. The caterpillar mower digs ruts, which are especially pronounced along the tracks used to reach the mown compartment. To assess the effects of site management on these species, we have tested six environmental parameters (vegetation unit, water conductivity, water supply indicated by altitude, time elapsed since the last cut, distance from major ruts and disturbance of major ruts) that can potentially influence plant distribution. All the plots of these two species have been found in mowed compartment, which seems to indicate a correlation between site management operations and occurrences. The other factors driving the distribution of these plants are vegetation unit, distance from major ruts and water supply.

Wetlands are amongst the richest, yet most threatened types of habitats on Earth. One major threat is the modification of water regime for human activities, which disrupts normal ecosystem equilibrium. In lacustrine wetlands, reduced flooding allows shrubs to take over, ultimately leading to a shift towards woody communities. To counter this, wetland managers have initiated a variety of measures, including mowing, burning, and pasturing. Because of the short time frames of previous studies on the subject, little is known on their potential negative side effects on the ecosystem. Here, we evaluate the long-term effect of mowing on breeding populations of the five most abundant species in our central European study area (the reed warbler Acrocephalus scirpaceus, the common reed bunting Emberiza schoeniclus, Savi's warbler Locustella luscinioides, the water rail Rallus aquaticus, and the bearded reedling Panurus biarmicus). This study, of an unprecedented time scale (30 years), shows that rotational mowing has no long-term detrimental effects on birds. However, optimal mowing regime for the birds might often be less frequent than what is usually applied. We recommend that mowing be spaced every 3 years at least, and ideally every 6 years or more. We discuss additional measures that could be implemented to complement mowing. Because of the widespread distribution of the target habitat and species, our study provides readily applicable information for wetland managers in Europe and worldwide.

Using environmental parameters we studied the distribution of two endangered species, Hydrocharis morsus-ranae L. and Rumex hydrolapathum Huds., in a low-lying marshland of the Swiss Plateau, a region in which aquatic vegetation is particularly threatened. A large part of the study site is regularly mown by a machine for site management purposes. The caterpillar mower digs ruts, which are especially pronounced along the tracks used to reach the mown compartment. To assess the effects of site management on these species, we have tested six environmental parameters (vegetation unit, water conductivity, water supply indicated by altitude, time elapsed since the last cut, distance from major ruts and disturbance of major ruts) that can potentially influence plant distribution. All the plots of these two species have been found in mowed compartment, which seems to indicate a correlation between site management operations and occurrences. The other factors driving the distribution of these plants are vegetation unit, distance from major ruts and water supply.