Seed production of semi-natural grasslands: Amount and variability in an unfertilized upright brome and a fertilized tall oat-grass meadow

摘要

Seed production is an important grassland feature, as it affects its persistence and botanical composition, and plays an essential role in complex plant-animal interactions. Species-rich seed mixtures from grasslands can be utilized for ecological restoration. Previous studies used different methods to characterize seed production and did not consider all the main aspects involved; hence, they did not allow the complete understanding of the seed production. In this study the seed yield of an unfertilized Mesobromion and a fertilized Arrhenatherion meadow were investigated by considering all main reproductive traits and grassland species. In Arrhenatherion, the viable seed production was 24,000 seeds m(-2) year(-1), with a viable seed set of 21% (ovule number 115,000 m(-2)). These values were three times higher than those in Mesobromion. This difference was mainly attributed to different fertile shoot densities (758 vs. 358 m(-2) for Arrhenatherion and Mesobromion respectively). Grasses transformed ovules to seeds (38%) more efficiently than forbs (11%). The standing seed yield at the first mowing was 35% and 45% of the produced seeds for Mesobromion and Arrhenatherion respectively. Because of late mowing, which is typical for Mesobromion meadows, the proportion of species found as seed at the first mowing was higher than that in Arrhenatherion. However, because many Mesobromion species were found to be poorly seed-producing forbs with high spatial and temporal variabilities of seed yield, harvesting of seeds of all species would be more difficult, and a greater effort would be necessary if the collected seeds are to be used in ecological restoration.