Authors:M. Dainese, M. Scotton, F. Clementel, A. Pecile, and J. Lepš
We studied the floristic composition in the pastures of the Southern Alps (Trento Province, Italy). One hundred and five plots in seven different pasture plant communities were sampled: (1) nitrophilous, (2) montane mesic, (3) subalpine mesic, (4) calcareous montane, (5) calcareous subalpine, (6) acid montane, and (7) acid subalpine pastures. Forward selection and variation partitioning were applied to identify the most important factors controlling the species composition and plant traits in the pastures. Aggregated weighted averages were calculated for each plot using the published values of average height, specific leaf area, and seed mass for each species. Explanatory variables were recorded for each site to reflect climate, soil properties, and grazing pressure. We hypothesised that species composition and functional variation in pastures of the Southern Alps are controlled by three main environmental filters: climate, resource availability, and grazing pressure. We found that variables of climate and soil properties had a major role in explaining the species composition and variations in plant traits, while grazing pressure showed a lower independent effect. Species composition and plant traits depended mainly on temperature, soil fertility, and variables of bedrock type — soil pH. Our results confirm the importance of taking the effects of climate and resource availability into account when describing plant and community functions of grasslands.
Authors:M. Carlucci, F. Teixeira, F. Brum, and L. Duarte
The vegetation in the southern Brazilian highlands is characterized by Araucaria forest and Campos grassland. Evidences indicate that Araucaria forest is currently expanding over grassland and that this expansion may occur by nucleation or edge dynamics. Nucleation mechanisms of Araucaria forest expansion are well documented, whereas mechanisms of expansion starting from the forest edge are not. In this study, we aimed (1) to assess how prominent is Araucaria forest expansion over Campos grassland starting from the forest edge, and (2) to discuss about the possible mechanisms underlying sapling community colonization in grassland. We conducted our sampling in 11 transects disposed from the forest edge towards the grassland. The transects were distributed in four study sites. Each transect was 50 m long and was divided into 25 plots with area of 8 m2. All forest woody sapling individuals were identified and registered. We considered distance from forest edge, presence of dead shrubs, Baccharis uncinella cover, nurse tree cover and rock cover as predictors of forest plant abundance and composition. Niche and distance contribution on the explanation of sapling composition and abundance were partitioned using, respectively, canonical correspondence analysis and multiple regressions. Cover of nurse trees explained almost 31% of total variation in sapling abundance, followed by the distance from the forest edge that explained 6.9%. Site explained 7.6% of total variation in sapling species composition, followed by distance from the forest edge, which explained 2.3%, whereas niche had a minor (2.1%) and non-significant proportion of variation explanation. Our findings show that Araucaria forest expansion over native grasslands in southern Brazil relies deeply on the nurse plant effect. Previous studies have demonstrated that Araucaria forest forms nuclei scattered in the grassland where nurse plants or nurse rocks are established. Here, we bring evidences that nurse plants are important also to the tree encroachment starting closer to the forest edge. This study provides new information on the mechanisms involved in the forest expansion over native grasslands.
Authors:E. Santi, E. Mari, S. Piazzini, M. Renzi, G. Bacaro, and S. Maccherini
Farmland ponds represent habitats with a high conservation value that make a significant contribution to regional biodiversity. Understanding the influence of plant species composition and environmental variables in driving variations in animal species composition in ponds is an important issue in the fields of ecological research and conservation biology. Using variance partitioning techniques to quantify independent effects, we examined how plant species composition, local-landscape configuration and physicochemical variables interact in influencing aquatic insect and amphibian community composition. The ponds investigated in this study were located in the Site of Community Importance — Special Protected Area (Natura 2000 Network) “Monte Labbro — Alta Valle dell’Albegna” (Tuscany, central Italy). Our results showed that: (i) plant community composition (such as Carex hirta, Glicerya fluitans, Potamogeton natans, Typha latifolia) is a good predictor for amphibian but not for aquatic insect species composition; (ii) aquatic insect species composition was more strongly affected by the landscape context, whereas for amphibians the local characteristics of the ponds were determining; (iii) the physicochemical context is a poor predictor for these animal taxa; (iv) lastly, and notably, the explanatory variables explained a high proportion of the total variation in amphibian and aquatic insect species composition. Our results have important implications with respect to the creation of new ponds, which should preferentially take place close to semi-natural grasslands and other wetlands, in order to maintain greater connectivity, and away from urban areas. Moreover, larger ponds are preferable for the preservation of pond biodiversity. The management and conservation of ponds is necessary to ensure the protection of habitats, the survival of individual species and overall pond biodiversity.
Authors:L. Duarte, M. Carlucci, C. Fontana, S. Hartz, and V. Pillar
We evaluated the functional relevance of diaspore traits related to disperser attraction (DAT) of woody plants as indicators of plant-disperser mutualisms in the colonization of Araucaria forest patches in southern Brazil. Diaspores of colonizer plant genera were characterized in relation to DAT (diaspore type, size and color). We discriminated the influences of phylogenetic relationships among plant genera, forest patch size and interaction records with frugivorous birds on DAT by using variation partitioning based on Redundancy Analysis (RDA). DAT variation was poorly explained by each factor separately. Nonetheless, variation explanation shared between phylogeny and interactions was considerably high, indicating that the influence of interactions with frugivorous birds on DAT tended to be phylogenetically conserved. Furthermore, the variation related to patch size was high only when shared with phylogeny and interactions. Large, red, orange or brown diaspores, mainly berries and figs were related to more developed patches, while small to medium, violet or black drupes were related to small patches. Patch colonization is likely to result from a balance between plant responses to habitat conditions and plant diaspore traits, which is expected to influence seed deposition patterns depending on habitat use and diaspore handling by dispersers. Although phylogenetic habitat filtering is commonly thought to reflect ecophysiological plant traits, our results suggest that interactions with dispersers could also explain phylogenetic habitat filtering in plants.
Authors:R. E. Lorenzón, A. H. Beltzer, P. M. Peltzer, A. L. Ronchi-Virgolini, M. Tittarelli, and P. Olguin
We studied spatial changes in species composition (i.e., beta diversity) of local assemblages of birds along ∼450 km of the Middle Paraná River, an extensive fluvial system of South America. Point counts were used to survey birds at 60 plots located in shrub swamps and marshes of the floodplain within four sites (15 plots per site). Two sites were surrounded by each of the two upland ecoregions. Beta diversity of bird assemblages was high and was more important than alpha diversity in shaping regional diversity (i.e., gamma diversity) of the fluvial system. Compositional changes were related to species turnover among plots, while nestedness dissimilarity was not important for shaping diversity patterns. Variation-partitioning analysis showed that local conditions (i.e., landscape composition within a radius of 200 m from the center of each plot) accounted for more spatial variation in assemblage composition than did location along the fluvial system. Adjacent upland ecoregions did not account for spatial changes in bird composition within the fluvial system. In conclusion, environmental heterogeneity created by flood pulses is an important factor for sustaining regional diversity of birds within the fluvial system through effects on beta diversity.
J. E. Lawesson. 1998. Vegetation in Danish beech forests: the importance of soil, microclimate and management factors, evaluated by variationpartitioning. Plant Ecology 134: 53-65.
Vegetation in Danish beech forests: the
. 1994. Canonical correspondence analysis with variationpartitioning: some comments and an application. J. Veg. Sci. 5:117-26.
Canonical correspondence analysis with variationpartitioning: some comments and an application