How much are isolated relict forest reserves influenced by local and external factors? – A case study on vegetation and moths in Northern Italy
Human populations all over the world are increasing and have become the main force driving landscape structure, ecosystem functioning and biodiversity (Zalasiewicz, Williams, Steffen, & Crutzen, 2010). In most biota, only few fragmented near-natural habitat areas are remaining, which are embedded in highly transformed anthropogenic landscapes. The negative effects of habitat fragmentation, degradation and land-use change on biodiversity and ecosystems are manifold (Newbold et al., 2015).
Nevertheless, isolated and fragmented patches are often designated as conservation areas to maintain their biota and important ecosystem services, but gradients of habitat quality inside the reserves arising from multiple influences are underrepresented in recent studies (Mortelliti, Amori, & Boitani, 2010) as well as the consideration of the landscape context.
There is a strong need to better understand the multiple impacts on nature reserves to ameliorate conservation management and to improve the survival chances of the last near-natural habitats in the age of the anthropocene (Oldfield et al., 2013).
Analyzing anthropogenic influences on ecosystems by investigating special study sites has always the disadvantage that there is not only one single factor that can clearly be determined to be the main driver of changes in organismal communities. There is always a multitude of different factors, possibly interacting, strengthening or dampening one another.
Interactions between the different trophic layers can influence the biodiversity - ecosystem stability linkages and accordingly affect the results of biodiversity studies (Worm & Duffy, 2003). If no experimental manipulation is feasible, the only way to understand the relationships between multiple environmental factors and plant or animal communities in real ecosystems is to get as much information of the local circumstances as possible and to subsequently infer possible causal pathways using data-analytical approaches.
The main focus of my work will deal with nocturnal Lepidoptera (Macroheterocera and so-called "microlepidoptera") in two isolated relict forests (Pineta san Vitale and Pineta di Classe), being part of the national park “Parco regionale del Delta del Po” located near the Adriatic coast of the Emilia Romagna (Italy). I will try to evaluate, how far moth communities inside the forest reserves are determined by abiotic factors, local vegetation, landscape context and/or external pollution sources.
The following working hypotheses will be tested:
- Plant communities are mainly determined by local factors like soil mineralization or microclimate, which can be influenced by surrounding land-use. Landscape heterogeneity is no determining factor for plant diversity inside relict forest sites.
- Pineta san Vitale has a higher moth Alpha-Diversity than Pineta di Classe, though it is more influenced by pollution and soil salinity. Surrounding landscapes and the habitats inside the Park are more heterogeneous and so “dissimilarity of local communities determines biodiversity and overrides negative local effects” (following Tscharntke et al. (2012)).
- Local vegetation and the degree of disturbance (for example the distance to pollution sources) are important for moth community composition and occupation of functional niches