Benthic nematode assemblage composition and diversity during a natural recovery process of Zostera noltii seagrass beds,

In 2008, the stable seagrass beds of the Mira estuary (SW Portugal) disappeared completely; however, during 2009, they have begun to present early symptoms of natural recovery, characterised by a strongly heterogeneous distribution. This study was designed to investigate the spatial and temporal variability patterns of species composition, densities and trophic composition of the benthic nematode assemblages in this early recovery process, at two sampling sites with three stations each and at five sampling occasions. Because of the erratic and highly patchy seagrass recovery and the high environmental similarity of the two sampling sites, we expected within-site variability in nematode assemblages to exceed between-site variability. However, contrary to that expectation, whilst nematode genus composition was broadly similar between sites, nematode densities differed significantly between sites, and this between-site variability exceeded within-site variability. This may be linked to differences in the Zostera recovery patterns between both sites. In addition, no clear temporal patterns of nematode density, trophic composition and diversity were evident.

Generalities of vertebrate responses to landscape composition and configuration gradients in a highly heterogeneous Mediterranean region

Aim To examine the distributional patterns of vertebrates (including birds, bats, carnivores and lagomorphs) along landscape composition and configuration gradients to better understand the effects of landscape modification on occurrence patterns at both species and community level. Location The region of Alentejo, a forest-dominated area of southern Portugal. Methods The study area was framed using 1647 hexagonal plots, each of 259 ha in size. Composition and configuration gradients were obtained for each plot by integrating the proportions of the main land cover types and their configuration patterns using multivariate analyses. Species-specific vertebrate responses were investigated using data from 75 plots in which carnivores, bats and lagomorphs were sampled, and from 135 plots in the case of birds. Community- level responses were investigated through changes in species richness and beta-diversity in 57 plots where all vertebrate groups were simultaneously sampled. At the species-level, an information-theoretic approach was used to determine the effects of landscape gradients on species’ responses. At the community level, Mantel tests were used to determine between-plot differences in species composition using the Sørensen dissimilarity index. Results We found that the occurrence patterns of most vertebrate species were best predicted by composition-related gradients, although configuration gradients were also frequently included in species-specific occurrence models. We also found a weak correlation between species richness and most landscape gradients suggesting a turnover in the identity of species, something that was corroborated by the stronger correlation between environmental gradients and beta-diversity measures. The amount of forest cover and landscape complexity (estimated as the heterogeneity in the size and number of land cover types) were the main composition and configuration gradients determining vertebrate responses at both species and community level. Main conclusions Our work contributes to a more refined understanding of the mechanisms underlying species distributional patterns in real-world human-modified landscapes. By uncovering generalities of species with multiple ecological requirements and by describing the entire landscape mosaic through landscape gradients, we also suggest that our work greatly helps to fill the gap between existing conceptual landscape models aimed to understand species distributional patterns in human-modified landscapes.

Colonização de bermas de estradas do Sul de Portugal por Dittrichia viscosa L. e seus efeitos na diversidade florística das bermas

A distribuição da espécie D. viscosa, nativa em Portugal, foi avaliada ao longo da berma de duas estradas, do sul do país. A composição florística e a percentagem de cobertura do solo das diferentes espécies foram amostradas em áreas de berma com e sem a influência de D. viscosa, para avaliar o seu efeito nas comunidades das bermas. O efeito do corte dos arbustos foi também estudado. A espécie em estudo apresentou uma clara preferência pelas bermas, comparativamente com as áreas envolventes. Os resultados sugerem que a presença dos arbustos provoca uma diminuição na biodiversidade das bermas. As estradas estudadas devem, portanto, ser alvo de controlo da distribuição desta espécie, para impedir a sua invasão. Com base nos resultados, sugerimos que o controlo deve ser efectuado através de dois cortes, no meio da primavera para impedir a propagação de incêndios e no final do verão, para prevenir a dispersão das sementes. ABSTRACT; The distribution of the native species D. viscosa was evaluated along the road verges of two roads in southern Portugal. The plant species composition and cover were surveyed within the roadside habitats, in areas with and without D. viscosa, to evaluate its effect on road verge communities. The effect of mowing on D. viscosa shrubs was also assessed. Shrubs showed a clear preference to verges relative to the surroundings, indicating that D. viscosa seems to be invading the study road verges. Results also suggest that the presence of the shrubs decrease the plant diversity of road sides, with potential effects on animals as well. Therefore, the study roads should be considered as important targets of local and regional efforts to prevent invasions of this species. Based on our results, we suggest that to prevent D. viscosa invasion within roadside ecosystems, the control should be based on two mowings, in mid-spring to prevent fires and in late-summer to prevent seed dispersal.

Above ground biomass functions with vegetation indices for multiple use systems of two evergreen oaks

Remote sensing is a promising approach for above ground biomass estimation, as forest parameters can be obtained indirectly. The analysis in space and time is quite straight forward due to the flexibility of the method to determine forest crown parameters with remote sensing. It can be used to evaluate and monitoring for example the development of a forest area in time and the impact of disturbances, such as silvicultural practices or deforestation. The vegetation indices, which condense data in a quantitative numeric manner, have been used to estimate several forest parameters, such as the volume, basal area and above ground biomass. The objective of this study was the development of allometric functions to estimate above ground biomass using vegetation indices as independent variables. The vegetation indices used were the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Simple Ratio (SR) and Soil-Adjusted Vegetation Index (SAVI). QuickBird satellite data, with 0.70 m of spatial resolution, was orthorectified, geometrically and atmospheric corrected, and the digital number were converted to top of atmosphere reflectance (ToA). Forest inventory data and published allometric functions at tree level were used to estimate above ground biomass per plot. Linear functions were fitted for the monospecies and multispecies stands of two evergreen oaks (Quercus suber and Quercus rotundifolia) in multiple use systems, montados. The allometric above ground biomass functions were fitted considering the mean and the median of each vegetation index per grid as independent variable. Species composition as a dummy variable was also considered as an independent variable. The linear functions with better performance are those with mean NDVI or mean SR as independent variable. Noteworthy is that the two better functions for monospecies cork oak stands have median NDVI or median SR as independent variable. When species composition dummy variables are included in the function (with stepwise regression) the best model has median NDVI as independent variable. The vegetation indices with the worse model performance were EVI and SAVI.

The impact of abandoned/disused marble quarries on avifauna in the anticline of Estremoz, Portugal: does quarrying add to landscape biodiversity?

Although the extractive operations of quarrying are often considered environmental threats, there is some evidence that abandoned quarries may have a significant positive impact on biodiversity by enhancing habitat quality for several species. In Estremoz Anticlinal, SE Portugal, many of the existing marble quarries have been inactive for decades and were abandoned without any restoration project in progress. The impact of quarry abandonment on avifauna diversity was assessed relative to reference conditions using adjacent rural fields as control areas. No significant differences were found in within-community diversity (alpha diversity) between abandoned quarries and reference sites. However, several dissimilarity indices showed a clear divergence in species composition between abandoned quarries and reference sites. Furthermore, statistically significant differences in species compositions were found between quarries abandoned for different periods. Over time, species composition becomes more similar to that observed in reference sites, reflecting ecological succession and landscape resilience to quarrying. Nevertheless, the studied quarrying landscape exhibited higher gamma and beta diversity than the former traditional landscape; thus, our results suggest that abandoned quarries, rather than damaging and destroying niches, can promote new ecological niches and significantly diversify rural landscapes.

The impact of abandoned/disused marble quarries on avifauna in the anticline of Estremoz, Portugal: does quarrying add to landscape biodiversity?

Although the extractive operations of quarrying are often considered environmental threats, there is some evidence that abandoned quarries may have a significant positive impact on biodiversity by enhancing habitat quality for several species. In Estremoz Anticlinal, SE Portugal, many of the existing marble quarries have been inactive for decades and were abandoned without any restoration project in progress. The impact of quarry abandonment on avifauna diversity was assessed relative to reference conditions using adjacent rural fields as control areas. No significant differences were found in within-community diversity (alpha diversity) between abandoned quarries and reference sites. However, several dissimilarity indices showed a clear divergence in species composition between abandoned quarries and reference sites. Furthermore, statistically significant differences in species compositions were found between quarries abandoned for different periods. Over time, species composition becomes more similar to that observed in reference sites, reflecting ecological succession and landscape resilience to quarrying. Nevertheless, the studied quarrying landscape exhibited higher gamma and beta diversity than the former traditional landscape; thus, our results suggest that abandoned quarries, rather than damaging and destroying niches, can promote new ecological niches and significantly diversify rural landscapes.

Hierarchical spatial segregation of two Mediterranean vole species: the role of patch‑network structure and matrix composition

According to ecological theory, the coexistence of competitors in patchy environments may be facilitated by hierarchical spatial segregation along axes of environmental variation, but empirical evidence is limited. Cabrera and water voles show a metapopulation-like structure in Mediterranean farmland, where they are known to segregate along space, habitat, and time axes within habitat patches. Here, we assess whether segregation also occurs among and within landscapes, and how this is influenced by patch-network and matrix composition. We surveyed 75 landscapes, each covering 78 ha, where we mapped all habitat patches potentially suitable for Cabrera and water voles, and the area effectively occupied by each species (extent of occupancy). The relatively large water vole tended to be the sole occupant of landscapes with high habitat amount but relatively low patch density (i.e., with a few large patches), and with a predominantly agricultural matrix, whereas landscapes with high patch density (i.e.,many small patches) and low agricultural cover, tended to be occupied exclusively by the small Cabrera vole. The two species tended to co-occur in landscapes with intermediate patch-network and matrix characteristics, though their extents of occurrence were negatively correlated after controlling for environmental effects. In combination with our previous studies on the Cabrera-water vole system, these findings illustrated empirically the occurrence of hierarchical spatial segregation, ranging from withinpatches to among-landscapes. Overall, our study suggests that recognizing the hierarchical nature of spatial segregation patterns and their major environmental drivers should enhance our understanding of species coexistence in patchy environments.

Species richness and composition of butterfly assemblages (Lepidoptera:Rhopalocera) along the altitudinal gradient of Serra da Estrela

Os gradientes altitudinais são importantes modelos em ecologia pois permitem, numa escala reduzida, estudar a influência da variação de diversas variáveis ambientais nos padrões de biodiversidade existentes. Estes padrões são influenciados por diversos factores, desde variáveis climáticas às relacionadas com a perturbação humana. Nesta tese é estudada a variação na composição das comunidades de borboletas ao longo do gradiente altitudinal na Serra da Estrela e são testadas duas hipóteses sobre os padrões de riqueza específica ao longo do gradiente altitudinal: a regra de Rapoport e o “Mid Domain Effect” (MDE). Foram assinaladas 70 espécies de borboletas neste estudo e constatou-se que a variação na riqueza de espécies de borboletas apresenta um padrão “mid peak” apoiando o MDE. Verificou-se também que as comunidades de borboletas do mesmo nível altitudinal são mais semelhantes entre si independentemente da vertente em que se encontram e são também mais semelhantes com as comunidades dos níveis altitudinais adjacentes. Finalmente, a análise da distribuição de algumas espécies ameaçadas de borboletas torna evidente a necessidade de realização de mais estudos sobre a biologia da conservação deste grupo de animais em Portugal; Abstract: Altitudinal gradients are important ecological models because they allow us to study the influence of diverse environmental variables in the existing biodiversity patterns. These patterns are influenced by various factors, from climatic variables to variables related to human disturbance. In this thesis we studied the variations in the composition of the butterfly assemblages along the altitudinal gradient of Serra da Estrela and we tested two hypotheses regarding the species richness patterns along the altitudinal gradient: Rapoport’s rule and the Mid Domain Effect (MDE). In this study 70 butterfly species were marked recorded and it was observed that the butterfly species richness presents a mid-peak pattern supporting the MDE. It was also noted that the butterfly assemblages in the same altitudinal level show more similarity within themselves regardless of the slope they are found in, and are also more similar to the assemblages present in the adjacent altitudinal levels. Finally, the distribution of some threatened butterfly species was analyzed and it became evident the need to do more studies regarding the conservation biology of this animal group in Portugal.