Hodge, Jonathan Gareth William; (1997) The control of relative abundance in hay meadows and woodland grasslands. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

1. Thirteen common grassland species were selected from either an MG5a hay meadow or a woodland grassland source in Suffolk, and their performances at four life stage filters (interference between established plants, flower production, seed germination, establishment of small seedlings into turf) were assessed experimentally. 2. In the established plant interference experiment, the plants were transplanted directly into the turf at three meadow and three woodland grassland sites and were harvested ten months later. Eight species showed a positive relationship between their dry masses and field frequencies amongst the six sites, suggesting that adult interference is an important factor controlling their relative abundance. In addition, a strong positive relationship (significant at 0.01%) was found between dry mass and field frequency for all the experimental species growing at the meadow sites, but not at the woodland sites. 3. None of the species showed a strong positive relationship between either flower production, seed germination, or seedling establishment and field frequency. This suggests that these filters are not controlling relative abundance of the experimental species in meadows and woodlands. 4. A study of the seed bank suggested that this might be important for maintaining the presence of ruderal species in the meadow flora between such times as suitable niches exist for their growth in the turf. No such evidence was recorded at the woodland sites. 5. A glasshouse experiment demonstrated the existence of meadow and woodland ecotypes of both Centaurea nigra and Alopecurus pratensis (the latter previously unreported), but not of Holcus lanatus. 6. Interpretation of these results showed that Grime's "CSR" strategies were not useful in predicting the experimental behaviour of the species in the meadow and woodland. 7. Grime's "CSR" strategies were useful, however, in interpreting patterns of species distribution. The species at all sites showed a range of strategies, but those at the meadow sites showed a greater tendency to exhibit a single strategy (C-S-R) preferentially, suggesting that selective forces are more strongly focused in the meadow than in woodland grasslands.

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