Search

Describing the rules of community assembly is a central topic of ecology. Studying successional processes through a trait-based null model approach can help to better understand the rules of community assembly. According to theoretical considerations, at the beginning of succession - after getting over the dispersal limitation stage - community composition is primarily shaped by environmental filters (generating functional convergence), while in later stages limiting similarity (generating functional divergence) will be dominant. However, empirical evidence does not clearly support theoretical expectations. Our aim was to detect the presence and changes of trait-based assembly processes during old-field succession based on twelve traits. Changes in vegetation composition were evaluated by a combination of time series and space-for-time substitution: conducting three resurveys of permanent plots on four old-field age-groups. The individual dispersion of traits was transformed into effect size (i.e. departure from null model expectation). The impact of time since abandonment on effect sizes was tested by generalized additive mixed effect models. We detected a non-random pattern for each trait in at least some part of the succession. Departure from randomness did not change significantly over time for six traits: seed mass, lateral spread and pollination type were divergent, while leaf size, generative height and length of flowering were convergent. Six traits had changing patterns along the succession. Four of them showed increasing divergence (e.g. dispersal type, LDMC), which supports our hypothesis. While two (SLA, life form) displayed increasing convergence, contrary to expectations. We confirmed the general hypothesis that convergence is predominant initially and that divergence can be detected later in succession for four traits. However, the large variation found in trait dispersion indicates that complex processes operate during succession. [ABSTRACT FROM AUTHOR]

Invasion of alien plant species is one of the main reasons for biodiversity loss in terrestrial ecosystems. However, alien plant species are not evenly distributed in the landscape. We studied which factors determine the actual level of neophyte invasion in a landscape with heterogeneous land-use and which habitats are the most infected. Since neophyte species with different life-forms can respond differently to the factors determining the invasion, species groups of annual, herbaceous perennial and woody neophytes were also analyzed separately. The study was conducted within the field site network of the Kiskun-LTER program (Hungary), in 16 sites of 5 km × 5 km. Fifteen habitat types were distinguished belonging to five major land-use/land cover types (agricultural land, abandoned agricultural land, tree plantation, semi-natural grassland and semi-natural forest). Present and past land-use, landscape composition and environmental variables were included as factors with a potential impact on the level of invasion. The most important factor determining invasion level was present habitat type, followed by the past habitat type of the location and landscape context. Tree plantations, agricultural habitats and recently abandoned agricultural habitats had the highest level of invasion. As expected, annual neophytes were most abundant in agricultural habitats, while perennial herbaceous neophytes were most abundant in old-fields and plantations, and woody neophytes in tree plantations. Past agricultural land-use was reflected in the higher levels of invasion of annuals and perennials, and past forestry practice resulted in higher levels of invasion of woody neophytes. In a landscape with a higher proportion of tree plantations, not only the tree plantations, but primary woodland patches also showed higher levels of invasion by woody neophyte species. Our results indicate the importance of present and past land-use in plant invasion and suggest that tree plantations are hot-spots of plant invasion and threaten the remnants of semi-natural vegetation. [ABSTRACT FROM AUTHOR]

Urban-industrial restoration of complex native vegetation, such as grassland-forest mosaics could counteract land degradation and help develop methodology for larger scale complex restorations. We have studied the impact of grassland reconstruction techniques, the resulting biotic conditions, plus abiotic conditions on early woody survival in a forest-steppe reconstruction at an urban-industrial site. The study area is situated at the factory of the LEGO Group, Nyíregyháza in the acidic inland sand dune region of Nyírség, NE Hungary, Europe. Over 10,000 undercut 1-2-year-old saplings of 16 tree and shrub species were planted in patches of various size in November 2015 at ca. 20% of the restoration area. Specific plans were developed for each woody patch within the restored grassland. Tree and shrub survival was counted for all saplings in all patches in the summer of 2016. Vegetation height, cover of herb-layer, and elevation a.m.s.l. were estimated for each woody patch and soils were characterized for each restoration parcel. First year woody survival rates ranged between 4 and 66% for the different species. Only vegetation height had an overall negative impact on woody survival and seven species reflected some (often contradictory) impacts of the studied environmental variables. In our interpretation this shows that woody survival was basically independent of the grassland reconstruction techniques, but also that the management of the herb-layer of new woody plantations can be crucial in long-term maintenance. Our results support that the reconstruction of complex native habitats with a park-like appearance is a viable alternative to landscaping in industrial areas that can counteract land degradation and increase green infrastructure connectivity. The methods applied can be transferred to larger-scale restoration with modifications. • Forest-steppe reconstruction is a viable alternative to traditional landscaping • The impact of grassland introduction technique on woody survival was limited • Only height of the grassland had some impact on early woody survival • Six species reflected some impact of bare surface, soil or elevation • Similar landscaping in unused land can increase green infrastructure connectivity [ABSTRACT FROM AUTHOR]

• In plantation forests of forest-steppe species richness of forest specialist herbs is very low. • Site preparationdecreases stronger their richness than planting alien trees. • With site preparation alien plants appear and establish permanently in plantations. • Continuity of natural oak forests is the key to preserve richness of specialists. In forestry, several types of management practices are used, which have significant effects on species richness and composition. A number of studies concerning the effect of management on biodiversity have been conducted in the tropical and temperate forest zones. This topic is less studied in the forest steppe biome, where the reestablishment of plants from the surrounding patches is more limited than in the forest biome. Most studies compare alien plantations with seminatural forests. However, the effects of dominant tree species is mixed with the effect of the site preparation and site history in such comparisons, due to intensive site preparation in case of forest plantations. In this study, we separate the effect of these management elements. We examined the potential of currently used forestry protocol in preserving the plant biodiversity of the forest herb layer in the Pannonian sand forest steppe using 266 forest plots from the Kiskunság sand region in Hungary. The total richness and richness of habitat preference groups (forest specialists, grassland specialists, native weeds, and aliens) were compared in natural and plantation forests of different tree species to explore the effects of dominant tree species and site preparation on the species composition. Factors determining the richness of forest specialists in plantations were analyzed by fitting a regression tree, and the habitat preference of these species was described by their fidelity to the forest types. Our results show that total species richness is less sensitive to management than the richness of some species groups with a specific habitat preference. Forest specialist species can survive almost only in continuous seminatural oak forests, that is, in forests that are continuously present and do not undergo any site preparation. They are completely missing from young plantations, most likely because site preparation completely removes them. Their limited recolonization is possible only in plantations of native trees in landscapes where seminatural oak forests have been continuously present. Even under these conditions, only half of the forest specialist species are able to recolonize in the plantations. Grassland specialists, on the other hand, are present in every forest type but with low richness. Site preparation acts as a colonization window for weeds and aliens. However, while the richness of weeds is the highest in young plantations and decreases in established plantations, probably due to the canopy closing, the richness of aliens is the same in both young and established plantations. Considering our results, the current forestry protocol is hardly suitable for maintaining the plant biodiversity of forests in the forest steppe zone, therefore, management practices should be changed to focus more on the conservation of these endangered habitats. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effect of present and past landscape context examined on sand grassland biodiversity. [•] Primary grassland specialist species defined by statistical fidelity measures. [•] Present landscape had no significant relationship with specialist species richness. [•] Landscape context of 19th century affects significantly the present biodiversity. [•] Long term delay of species loss is consistent with the extinction debt hypothesis. [ABSTRACT FROM AUTHOR]

• Plant diversities of quasi natural and moderately managed sites were compared in six major Pannonian habitat complexes. • Novel bootstrap statistics is useful for comparison of diversities of heterogeneous sites. • Gamma diversity (species richness) of specialist species is the most sensitive diversity indicator. • The diversity of loess and dolomite forest steppe complexes and freshwater marshlands is significantly lower in managed sites. • Reduced diversity is coupled with habitat loss. Habitat complexes exhibit varying vulnerability to human land use and thus have different impacts on biodiversity. In this study, we analyzed the effect of moderate land use on the plant species diversity in six characteristic Pannonian habitat complexes: forest steppe complex on sand, on dolomite, and on loess, as well as alkaline habitat complex, freshwater marsh complex, and zonal broadleaf colline forest. We chose two regions for each complex, and in each region, we selected a 2 × 2 km "natural" study site in a mostly protected area, and a moderately used "managed" site of the same size. We compared the alpha, beta, and gamma diversities of the total and the specialist species pools of the natural-managed site pairs by applying stratified random sampling and novel bootstrap statistics. The gamma diversity of the specialist species pool was found to be the most sensitive indicator of naturalness. It was higher in the natural sites of the loess and dolomite forest steppe and the freshwater marshland complexes, while there were no significant diversity differences in the other complexes. The diversity comparisons showed a consistent pattern: there were either no significant diversity differences in any of the natural-managed pairs, or there were significant differences in the gamma diversities of the specialist species pool in both the natural-managed pairs. We concluded that the same differences in naturalness may represent different sensitivities to human management as characterized by differences in diversity measures. Three habitat complexes, the loess and dolomite forest steppe and the freshwater marshland, require more focused nature protection efforts in order to preserve the habitat diversity, especially in maintaining the remnants of the natural woody patches and the most inundated habitats of the marshlands. In the case of the other studied complexes, moderate human land use can be harmonized by nature protection goals. [ABSTRACT FROM AUTHOR]