Factors controlling the establishment of species-rich grasslands in urban landscaping schemes

A thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Doctor of PhilosophyIn Britain, the creation of species-rich grasslands has generally involved the use of commercial seed mixtures. The present study has experimented with the use of freshly cut hay as a seed carrying medium and has considered some of the factors thought to be important for the creation of new species-rich grasslands. Two meadows, established in the early 1980's using hay cut from a single species-rich donor, were surveyed and a high degree of similarity with the donor meadow was noted. It was apparent, however, that the donor meadow had been replicated with a greater level of success by using fresh hay as opposed to dry hay. A total of 41 plant species were recorded in the meadow created using fresh hay, 26 of which may have been introduced as seed from the donor meadow. The importance of consistent management to sustain diversity was highlighted during the present study. A created meadow which had been poorly managed following its establishment displayed a marked division in its vegetation with large areas dominated by rank grassland species. Some form of site preparation, other than simply cutting the existing grass sward, favoured a more successful introduction of species from the donor meadow. However, it became clear that high levels of soil cultivation encouraged undesirable weeds and may not be necessary. Big baling proved to be an efficient method of collecting fresh hay from a donor meadow. It appeared to maximise seed transfer at any one time and a more diverse grassland was created. A meadow created using big baled hay supported a total of 50 plant species in the second year following its seeding, 32 of which were present in the donor sward. Elevated soil fertility is known to limit plant species diversity in semi-natural and created grasslands. Cropping prior to grassland creation proved to be an effective approach to reducing the effects widely attributed to elevated soil fertility. Although no measurable differences were recorded by chemical analyses, a better species composition and sward structure, and a lower standing crop, were recorded in the created meadows following cropping. Some crops were more effective at reducing the standing crop of the created sward than others. Potatoes and barley worked particularly well with mean standing crop values for the created sward as low as 335.38g/m 2 in the first year following seeding. In comparison, values of 581.68g1m2 were recorded in leaching plots which had been cultivated but not cropped and 837.88g/m2 in control plots in which the original grassland had been retained and which had not been cropped or received hay from the donor meadow. A novel approach to the use of DECORANA (Hill, 1979b), as presented in the VESPAN software package (Malloch, 1988), proved to be a valuable way of analysing the multivariate species data generated during one cropping experiment. The analysis indicated that, in addition to producing a lower standing crop, cropping with potatoes and barley encouraged a diverse sward to develop which included more species associated with the donor meadow. Experiments showed that meadow plots created using strewn hay supported a more diverse grassland sward than similar plots created using a purchased seed mixture with mean numbers of species per quadrat recorded of 16.4 and 7.3 respectively in the second year following seeding. Experiments using different types of donor grassland indicate that the creation of wet grasslands is more problematic than the creation of dry grasslands. In particular created wet grasslands require a longer period in which to become established