HORTICULTURE

Feasibility of Wildflower Meadow Plantation

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Feasibility of Wildflower Meadow Plantation

CHAPTER IV: FINDINGS AND ANALYSIS

Diverse semi-natural grasslands in Europe are habitats that are valued for their richness in flora and fauna and often feature rare or highly specialised species. The well-documented decline in the extent of these habitats over recent decades, particularly in Britain, has made them an attractive target of restoration projects. The creation of diverse grassland communities in urban areas could potentially remediate the dramatic decline of house sparrow (Passer domesticus) populations by providing an augmented supply of insect and seed food for these birds. Whilst the creation of diverse and valuable grasslands from bare soil is an established concept, creating perennial plant communities that are sustainable is fraught with difficulties. From studies of restoration projects on ex-arable land, propagule limitation and high residual soil fertility are significant obstacles. Quantitative studies of urban restorations are rare, but propagule limitation, trampling and dog use are likely to be influential factors. The success of projects is dependent on having clear goals. In urban restorations, it may be unsuitable to choose semi-natural plant communities as a target (Webb, 1998, 987).

A total of 116 plant species were identified across all sites: 31 species from the three different seed mixes used and 85 unsown tweed' species. Generally the wildflower meadows were more diverse than the control plots, had significantly taller vegetation and less bare soil. They also contained significantly more sown forb species, fine grasses and less coarse grasses. Abiotic factors such as levels of nutrients and pH did not predict these differences in diversity. The best established plot had a high nutrient status relative to the other sites (Perret's Field, 61% sown forbs, available P = 122ppm, total N = 4548 rngkg'). In contrast, one of the least diverse treatment plots (Waterlow Park - 34% weed species) had available phosphorus levels akin to diverse semi-natural grasslands (P = 12ppm, ADAS index 1.4) and the second lowest level of total nitrogen of all sites (N= 2605 mgkg') (Greenlee & Holt, 2009).

At the site level there was considerable variation in establishment success. Three of the eight treatment plots had a similar species richness to their controls. Whilst this indicated poor establishment of the desired species, the success of these plots depended on whether the vegetation they were replacing had any intrinsic ecological or aesthetic value. Even poorly established plots can be considered successful if the alternative is closely mown turf.

Statistical analysis of the patterns of diversity across the different meadow plots was limited for two reasons. Firstly, to avoid pseudoreplication, quadrat samples from the same treatment plot could not be compared between sites. Secondly, a range of uncontrolled variables affected different treatment plots and their controls in different ways. These include expected variation in the exact management regimes used, complications with different seed mixes and amounts of seed, and differing levels of trampling by people and fertilisation from dogs. These factors are likely to have been hugely influential in determining establishment success at ...