The importance of Ecoparks for saproxylic beetles : a study on general ecological hypotheses in differently managed landscapes

Abstract: Current forestry practices have led to a decline of deadwood availability in Swedish forests. Even though deadwood has increased somewhat in Swedish forests in later years, it is still far from estimated deadwood threshold levels and of those found in natural systems. This has in turn led to a decline in species associated with deadwood e.g. saproxylic beetles, which will be the focus group of this study. In order to halt this development, it is essential to study how different landscape management systems might influence saproxylic beetles. It is also of great importance to understand the major drivers of biodiversity, such as habitat amount or habitat heterogeneity. Ecoparks are Sveaskog’s landscape parks with a majority of the forest land being of conservation concern. Two of Sveaskog’s Ecoparks, one in northern and one in southern Sweden were the selected sites of this study, representing a multi-purpose driven forest landscape. Ecoparks are landscape-scale forest parks where at least 50% of the forest land is exempt from forestry measures. Reference sites where chosen to represent conventionally managed landscapes, but with similar properties as respective Ecoparks. Beetles were collected during 3 years in sun-exposed plots, where local (20m radius) habitat structure data was collected as well. Ecoparks held larger abundance and richness of red-listed beetles, but not of all saproxylic (deadwood dependent) beetles, compared to reference sites. Ecoparks contained different beetle community assemblages from reference sites. Deadwood amount had a positive relationship with the abundance of saproxylic beetles, as well as richness of facultative saproxylics in southern Sweden. Abundance of red-listed beetles also showed positive relationship with deadwood amount in southern Sweden. Deadwood diversity showed no conclusive effect other than being important for southern Sweden beetle community assemblages. Deadwood amount showed negative relationships to abundance within Ecoparks, compared to reference sites. Results show that more diverse and complex landscapes host different saproxylic community assemblages and larger amounts of red-listed beetles. This study supports the habitat amount hypothesis but not the habitat heterogeneity hypothesis. There are also indications that landscape complexity might influence local deadwood responses, giving support to the landscape intermediate complexity hypothesis. The results suggest that deadwood amount, in conventionally managed landscapes, should be increased at local levels. In more diverse landscapes, maintaining diversity and habitat size should be the main focus.