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Abstract

Adopting the ecosystem approach to nitrogen supply on extensive green roofs, using legumes (nitrogen-fixers), may create a self-regulating system of nitrogen acquisition for non-leguminous plants. This study aimed to determine whether legumes could contribute to non-leguminous plants’ total nitrogen concentrations at two points over the growing season T1: 18th June 2018 and T2: 10th September 2018. Comparisons of plant total nitrogen between legumes treatments, fertiliser treatments and a control treatment (i.e. no-legumes and no-fertiliser), over the same time series, were compared to determine legumes’ ability to supply similar levels of total nitrogen when compared to fertiliser treatments. Differences of total nitrogen in four specific species of non-leguminous plants (i.e. Festuca. ovina, Centaurea. nigra, Fragaria. vesca, Sedum. acre) were also examined over the two-time series to determine whether these species would be better adapted to nitrogen acquisition on extensive green roofs where legumes were the source of nitrogen. Generally, plant total nitrogen in treatments containing legumes increased over time, however, this was not significant. A significant increase of total nitrogen over time, did occur when comparing legumes-only treatments to the control treatment (p = < 0.05), clearly demonstrating legumes contribution to total nitrogen in the absence of any other significant nitrogen source. In comparison, fertiliser treatments had a clear effect on plant total nitrogen (p = < 0.05) over time. All individual plant species in mixed plots demonstrated increases of total nitrogen in legumes-only treatment over time (T1 – T2), except for Sedum. Acre, however, the effect of legumes was not significant in Fragaria. Vesca and Sedum. acre. Festuca. Ovina and Centaurea. nigra, were close to demonstrating an effect on total nitrogen acquisition (p = 0.054 and 0.055 respectively). The results are ecologically significant and demonstrate the potential for legumes to supply sufficient levels of total nitrogen for plants on extensive green roofs in the absence of synthetic fertilisers.

Course: Master of Philosophy - MPhil

Date Deposited: 2024-07-10

URI/permalink: https://library.port.ac.uk/dissert/dis14423.html