Session

Seed rain is an important element of vegetation dynamics, but still a topic which is not fully understood. Especially in restoration ecology the knowledge about seed rain plays a crucial role to assess the potential contribution of natural grassland to the restoration process. For measuring the natural seed rain, various methods have been used, but there is no standard. The aim of this study was to test four different types of seed traps (Funnel, Pot, Glue and Sticky, the first two 2 cm, the others 50 cm above the ground surface) under two different management regimes (grazed and ungrazed) in a semi-natural pampa grassland in Bahía Blanca (Argentina). The study was set up as a split-plot design with 6 blocks, with the management regime being the main plot and the seed trap type being the sub-plot. We investigated the following dependent variables: (1) contamination with non-seed, trapped material (insects, plant parts and soil), (2) effectiveness in catching seeds (seed density and species number), (3) effectiveness of representing as far as possible the whole plant community (Bray-Curtis Index, Jaccard Index, Pearson correlation and Mantel test). We found the highest contamination with insects for the Sticky traps, with plant parts for the Funnel traps and with soil for the ground-installed traps Funnel and Pot. We found the Funnel and Pot traps to be the most effective traps concerning seed density and the Pot traps concerning species number, respectively. Similar results were also found for the community. According to all measures (Bray-Curtis, Jaccard Index, Pearson correlation), the highest similarity between plant community and the trapped seeds was found for the ground-installed traps Funnel and Pot. Nevertheless, the Mantel test indicated only for the Pot traps a significant representation of the community. Our results underline the importance of seed traps selection for a better depiction of the studied community, an information that is not yet considered in most of the studies. Therefore, more studies are needed to increase the knowledge about the dispersal of seeds to understand the potential role of regeneration from surrounding areas.