Résultat de la recherche

Filtres

11
11
2
2
2
Réinitialiser les filtres

Paramètres

Voici les éléments 1 - 2 sur 2
  • Publication
    Accès libre
    Amphibian occupancy and abundance in beaver ponds in Switzerland
    (Neuchâtel : Université de Neuchâtel, 2024)
    Bolle, Patricia 
    ;
    Zemp, Clara 
    ;
    Schmidt, Benedikt
    ;
    Angst, Christof
    As ecosystem engineers, beavers are capable of creating heterogeneous environments that have a positive impact on many species. They increase habitat availability that can be colonised by species (endangered or not) and reduce fragmentation. Amphibians, one of the most threatened groups of vertebrates, are part of the species that could use and colonise the beaver ponds. The aim of this study is to analyse the occupancy and abundance of amphibians in beaver ponds in Switzerland. This analysis addressed the following questions: 1) What is amphibian abundance and occupancy at beaver ponds, 2) Does Rana temporaria use beaver ponds as ovipositional sites, 3) What are the factors (e.g., dam age) that drive amphibian occupancy and abundance in beaver ponds, and 4) if beaver ponds increaseconnectivity. Results of the occupancy analysis revealed that there were some preferences for the type of beaver pond occupied, most of them being flooded forests. Then, results from both abundance and occupancy showed that the strongest predictor that always came up was the dam age. Indicating that the older the dam is, the better, with more individuals in middle aged dams. Results from the connectivity revealed that beaver ponds had higher diversity if there were at least two amphibian breeding ponds nearby (less than one kilometre). Meaning that beavers could extend the already existing amphibian network by creating new ponds. Consequently, they have a good potential for conservation goals by maintaining stable and increasing amphibian populations.
  • Publication
    Accès libre
    Exploring Stand Structural Complexity’s Drivers: A Cerrado (São Paulo State, Brazil) Case Using Stand Structural Complexity Index (SSCI)
    (Neuchâtel : Université de Neuchâtel, 2023)
    Fontaine, Louis 
    ;
    Zemp, Clara 
    Developing and understanding full potential of new tools for large scale reforestation programs has become essential nowadays. In this framework, stand structural complexity (SSC) has been identified as essential driver for multiple ecosystem services. Using terrestrial laser scanner (TLS) with light detection and ranging (LiDAR), I measured stand structural complexity index (SSCI) among four experimental reforestation sites in early development stage (three to eighteen years old) to identify impact of five potential SSC drivers: (1) water availability, (2) species diversity, (3) functional diversity, (4) tree density and (5) treatment applied on reforested sites. I find that (1) increased water availability enhances SSC as well as species diversity on lower level (up to six species) and (3) functional diversity. Contrastingly, no effect on SSC was observed for (2) high species diversity (twenty to one hundred fourteen species), (4) tree density and (5) treatment. SSC is likely to be enhanced by (1) water availability by promoting shade tolerant species abundance, and niche complementarity can explain positive impact on SSC by both (2) species and (3) functional diversity. On the other hand, competition for resources is likely to explain the limited impact on SSC by (4) increased tree density and (5) treatment. Finally, niche complementarity saturation is likely to explain saturating SSC on high species diversity plots. I conclude that (1) water availability plays a crucial role for improving stand structural complexity, being its main driver, (2) species diversity and (3) functional diversity (on lower level) improves it, but high tree density and species diversity as well as increased treatment play a neglectable role for enhancing stand structural complexity on forest’s early stage. Those results put forward the importance of species mixtures with various functional traits in reforestation programs, and the unnecessity of increasing tree density and treatments (resulting in additional costs) for enhancing stand structural complexity.