Vascular flora of 71 artificial islands of varying agewas analyzed in 22 fishponds, Třeboň Basin, the Czech Republic. Data on species richness were interpreted in terms of Wilson’s (1969) hypothesis on the development of biotic communities. An increase in species richness during the non-interactive stage (one to two years) and a decrease in the interactive stage (three to six years) were both statistically significant. As predicted, by Wilson’s hypothesis, there was also an increase in species richness in the assortative stage (seven to >50 years), however, this trend was not significant. This successional pattern was confirmed by the vegetation development recorded on 34 re-sampled islands. For these islands the positive change in species richness during the assortative stage was significant based on both paired t- and binomial tests. Contributions of island area, elevation, and isolation during individual successional stages were evaluated. As a whole, this is probably the first clear confirmation of Wilson’s hypothesis for vascular plant communities on islands.
Various stages in the succession of vegetation of peat bogs following disturbance were studied in the Třeboň Basin, Czech Republic. The disturbance was of two types: (a) natural, represented by windthrow, with subsequent bark beetle attack, and fire, and (b) human-made peat digging and industrial peat milling. The species composition at different stages in succession following disturbance were compared with that in undisturbed plots. Regeneration of peat bog vegetation was faster after a natural than after human-made disturbance. The lowest impact was caused by windthrow, followed by fire. Regeneration after peat digging took much longer. Regeneration after industrial peat harvesting only occurred if the groundwater table level remained high.
The factors influencing plant species diversity in secondary and ancient forests can differ. Apart from environmental variability caused by natural conditions, secondary forests are influenced by historical factors (previous human activity). However, the effect of historical factors on vegetation is not fully understood. Secondary forests that have developed in abandoned villages in the Doupovské hory mountains, Czech Republic, were surveyed and compared with ancient forests in an attempt to determine the effect of historical factors and separate it from that of natural gradients. The results show that secondary forests in abandoned villages form a unique type of vegetation that differs from ancient forests mainly in the presence of species indicating a high nutrient content and high pH of the soils. This indicates that the previous high nutrient input in the villages still influences the soils and causes the differences. Variability of village forests is influenced mainly by a gradient in the available phosphorus content of the soils, soil moisture (approximated by wetness index) and organic matter content. The pattern in the phosphorus content and pH indicate a different intensity of historical influence in the centre compared to the periphery of the villages. Vegetation variability is modified by former land-use and village structure. The effect of historical factors is relatively strong and cannot be explained by coincidental initial conditions.
Succession of weeds and small mammal species was studied and compared on alfalfa field in two periods (cultivated 1996–1998 and set-aside 2001–2003). Composition of the plant community changed between the two periods of study. In the first period high biomass of green alfalfa biomass was available to the common vole which dominated small mammal community (88.7 %) and pronounced variation in maximal autumnal densities, typical of cyclic vole populations. Massive invasion of seed bearing weeds was stated after the field was set-aside and alfalfa biomass lowered. With the succession of weeds other rodent species such as Apodemus sp. increase their relative abundance (RA) and that of the pygmy field mouse was higher in the abandoned field compared with the common vole. The trend toward increasing RA was quite distinct (Z = 1.883; P = 0.060). Diversity of herb species and the small mammal species increased with abandonment. The monthly RA of the common vole was, on average, lower in the abandoned field than in the former period (Z = 2.353, P = 0.019). Also the cyclicity disappeared and RA of the population exhibited only seasonal oscillations. Biomass of the small mammal community decreased after the field was set-aside (Z = 3.021, P = 0.002).
The intermediate disturbance hypothesis predicts that species diversity in biotic communities should peak at intermediate levels of disturbance. The vegetation of eight calcareous screes in the Northern Calcareous Alps, Austria was studied to test this hypothesis. Data on total vegetation cover and on cover of individual species were obtained from 0.25 m2 , 0.5 m2 , and 1.0 m2 plots. An index [100 – vegetation cover (%)] was used as a surrogate for direct quantification of disturbance (movement of stones and destruction of biomass). Its suitability was substantiated by the observation of position changes of marked stones after two years. In agreement with the intermediate disturbance hypothesis, significant unimodal responses of both species richness and species diversity to disturbance were found using plots of all three sizes. However, the maxima of species richness- and species diversity-disturbance curves were shifted towards higher vegetation cover (= lower disturbance) with increasing mean diameters of the scree-building stones. This shift can be interpreted either as a synergistic effect of disturbance frequency combined with disturbance intensity/extent, or as a result of an increase in spatial heterogeneity promoting species coexistence in successionally more advanced patches of vegetation.
Viticulture is one of the most intensively managed agricultural ecosystems in Europe. Therefore, the conservation problems of vineyards and the ecological benefits of increasing the amount of fallow land are addressed using butterflies as a model group. We established 43 transects, each 100 m long, in a vineyard region in the vicinity of Trier (Rhineland-Palatinate, Germany) and recorded the butterflies observed along these transects on 20 occasions from late May to early August 2003. Transects crossed vineyards, fallow land and transitional areas of land. 4041 individuals of 34 species showed the typical pattern of relative abundance with few common and many relatively rare species. Fallow land had more individuals and species and a higher Shannon species diversity index than vineyards. Community evenness and average butterfly dispersal ability were highest in the vineyards. Principal Factor Analyses and UPGMA cluster analysis distinguished between fallow land and vineyards. The difference between early meadow and late forest fallow land areas was not strong, but the former tended to have a higher diversity than the latter. Vineyards thus might act as a sink for butterflies. Therefore, a clear separation between vineyards and fallow land is best for nature conservation. As young fallow land tends to have a higher diversity than older fallow land in this study, it is likely that the conservation value of vineyards for butterflies could be increased by active management of fallow land areas.