Veronica L. Love
Thesis Title: Shrubs and their role in modifying green roof microclimate
Supervisors: Dr. Ross Cameron (Department of Landscape, University of Sheffield), Prof. Andrea Nardini (University of Trieste, Italy), Dr. Andy Clayden (Department of Landscape, University of Sheffield)
Date started PhD and proposed submission date: 10/2015 – 01/2019
2007 – 2012, BSc Natural Sciences, University of Padua (N Italy)
2012 – 2014, MSc in Environmental Biology, University of Trieste (NE Italy)
My undergraduate years
From when I was a teenager, I imagined my dream job as one that would contribute to improving or protecting the environment. I also hoped to somehow combine my love of nature with writing and art. Plants, especially trees, have always been my passion, but I took a more comprehensive approach when choosing a course to study at university and chose Natural Sciences, which covers all sciences related to the environment. I realised early on in my undergraduate degree that I wanted to pursue botany and plant ecology. In fact, I did an internship at the elegant and charming Botanical Garden of Padua, doing germination tests on seeds belonging to rare plant species that are endemic to an area near Padua of great geological interest. I compared the viability of seeds collected from plants belonging to the same rare species but grown in the Garden with those collected from plants in their natural environment. Interestingly, seeds collected from plants grown in the Botanical Garden and stored in the Seed Bank had a significantly higher percentage of germination, a result that validates the role and importance of these institutions in preserving biodiversity.
My postgraduate years
Following my degree in Natural Sciences, my interest shifted from natural to urban environments, where often the need for preserving and expanding green spaces is highest. I became intrigued with the idea that places like botanical gardens are commonly found in cities and thus become important biodiversity hotspots. Perhaps the most important skills acquired during my Masters in Environmental Biology were learning of the various methods for monitoring diverse terrestrial environments, including plant ecophysiology techniques, and the typical statistical tests used when analysing ecological data. I eventually had the incredible opportunity to do an internship in the Laboratory of Plant Ecophysiology at the Department of Life Sciences (University of Trieste). During the summer months of 2013, I measured and analysed the morphological and ecophysiological responses of fourteen different Mediterranean shrubs growing on experimental green roofs. I also analysed data received from sensors placed in the green roof modules that monitored substrate temperature and moisture levels, as well as storm water runoff data. Among other experiments, I measured gas exchange and leaf water potentials at dawn and midday, relative growth rate, mortality, leaf mass per area, vein density, and analysed pressure-volume curves of leaves to obtain important plant trait measurements that correlate with the plants’ drought resistance (e.g., leaf turgor loss point, osmotic pressure at full turgor, cell wall elasticity, leaf water storage capacitance). The purpose was to compare the responses of shrubs growing on two shallow substrate depths (100 and 130 mm), thereby observing their fitness and survival on the rooftop’s harsh environment. Substrate temperature, moisture, and runoff were also monitored and analysed to compare the green roof performance in terms of both substrate depth and vegetation type (i.e., shrubs vs herbaceous perennials vs sedum). By correlating the values of the various plant traits, I was also able to identify those traits correlated with drought resistance that were easiest to measure, which in turn can potentially be used in protocols for the selection of green roof vegetation.
Coming to Sheffield for my PhD
My lab and field work experience during my internship in the Plant Ecophysiology Lab have been of chief relevance in preparing me and influencing my decision to pursue a PhD in Landscape. At the time, I did not realise that there was such a thing as a PhD in ‘Landscape’! However, I came across many journal articles written by academics from the University of Sheffield while writing my thesis and this raised my curiosity in both the University and the pandemic Department of Landscape. Over the summer of 2015, I realised I wanted to do a PhD because it felt like the natural continuation, and I still had so many questions in me! I became increasingly determined to pursue the field of green roof research and to seek an interdisciplinary and holistic approach. It is now 2017 and currently two years into my PhD and, so far, I have enjoyed living in Sheffield and doing my PhD very much. Sheffield is a very green city, with many parks and gardens and just a few bus stops away from the beautiful Peak District, while the Department of Landscape provides the unique, interdisciplinary research environment I need.
My research project
My research project is called “Shrubs and their role in modifying green roof microclimate” and aims to encourage the greater use of woody shrubs on green roofs by providing evidence that the shrub lifeform has numerous characteristics that can improve green roof performance in terms of thermal insulation and energy savings. The main hypothesis of the study is that different canopy types will have distinct effects on rooftop temperatures at substrate level, with plant spatial arrangement (density) strongly influencing microclimate underneath the canopies. In order to assess these effects, I need to evaluate which rooftop factor (e.g., temperature, relative humidity, irradiance), plant density, and/or morpho-anatomical and physiological plant traits (e.g., foliage cover/shading capacity, leaf thickness, transpiration rates, stomatal conductance, etc.) may have the greatest impact on roof thermal behaviour. Of importance is also the evaluation of the performance and survival of the six different shrub species, which will help answer the question ‘How do rooftop conditions affect the different shrub species and how can specific plant traits help predict plant fitness on green roofs?’ I wish to use the results from my study to determine how points above could be used to maximize green roof functionality and optimise cooling capacity and energy savings, as well as to identify co-factors that may be required to ensure the delivery of these benefits (e.g., irrigation, appropriate plant community structure, spacing, wider abiotic tolerances, etc.). The findings may also provide the inspiration for alternative green roof designs which maximize services and benefits throughout the year, for example, by taking advantage of the varying rooftop conditions and changing plant foliage.
The results so far point to the fact that there seems to be a significant relationship between canopy type (i.e., shape, density, branching), plant density, irradiance, and temperature/relative humidity at substrate level. Moreover, there are important differences in growth and morpho-physiological responses not only when comparing the different shrub species, but also when comparing the same species within the two different plant densities (dense vs sparse). These initial findings suggest that, through opportune selection, shrub canopy type and spacing could represent potentially important factors in increasing green roof thermal performance.
Writing and publications
- Savi, T., Love, V.L., Dal Borgo, A., Martellos, S., Nardini, A., 2017. Morpho-anatomical and physiological traits in saplings of drought-tolerant Mediterranean woody species. Trees – Structure and Function. DOI 10.1007/s00468-017-1533-7.
- Savi, T., Dal Borgo, A., Love, V.L., Andri, S., Tretiach, M., Nardini, A., 2016. Drought versus heat: What’s the major constraint on Mediterranean green roof plants? Science of the Total Environment 566-567, 753-760. DOI 10.1016/j.scitotenv.2016.05.100.
- Savi, T., Boldrin, D., Marin, M., Love, V.L., Andri, S., Tretiach, M., Nardini, A., 2015. Does shallow substrate improve water status of plants growing on green roofs? Testing the paradox in two sub-Mediterranean shrubs. Ecological Engineering 84, 292-300. DOI 10.1016.jecoleng.2015.09.036.
- Green roof technology,
- plant ecophysiology,
- landscape ecology,