This paper presents the " Environment and landscape geo-knowledge " project which aims to exploit heterogeneous data sources recorded at the Chizé environmental observatory since 1994. From a case study, we summarize the difficulties encountered by biologists and ecologists experts when maintaining and analyzing collected environmental data, essentially the spatial organization of landscape, crop rotation and wildlife data. We show how a framework which use a spatio-temporal ontology as a semantic mediator can solve challenges related to the analysis and maintenance of these heterogeneous data.