Not all plants are the same: the importance of plant choice

for the delivery of environmental benefits in urban areas

Dr Tijana Blanusa

Principal Horticultural Scientist, RHS

What are the problems?

•  Urban areas: trap heat + cool more slowly •  Consequence => higher air temperatures at night (UHI)

•  Energy release from buildings, industry, traffic etc. can also contribute to temperature increase

•  Buildings size / orientation, wind speed / direction, traffic: all affect air flow and heat transmission

2

•  Urbanisation – increases surface run-off (from sandy soil if sparsely populated = 32%, city centre =74%)

•  Gaseous (NOx, CO2, CO, SO2, …) and particulate air pollutants

•  Noise …

Vegetation can help – but the extent and choice of species are important!!

Maintenance …

What are the problems?

•  Air temperatures/ building insulation

•  Pollutant trapping •  Rainfall capture •  Carbon capture •  BVOCs emissions •  …

Plants provide many simultaneous services. PLANTS DIFFER IN THE EXTENT OF SERVICES’ PROVISION!

Vegeta&onandcooling

•  Shadingbya(large)canopy•  Reflec6onofincomingenergy

•  Providinglatentheatlossviaevapo-transpira&on

5E.g. Blanusa et al., 2013, Alternatives to Sedum on green roofs: Can broad leaf perennial plants offer better 'cooling service'? Building and Environment, 59, 99-106

PhD project: Impact of leaf colour and structure on energy balance

Madalena Vaz Monteiro

Modelled energy balance Vaz Monteiro et al., under review

SoilheatfluxUpto10-folddifferences

sensible

LatentheatfluxUpto4-folddifferences

TRANSPIRATION RATE, LEAF COLOUR, HAIRINESS

Vegeta&onandprecipita&on

•  Retainingwaterdropletsoncanopy

•  Restoringsoil’swaterholdingcapacityviaevapo-transpira&on

8

Reducedpressureonurbandrainagesystem

(BLUE-GREENinfrastructure)

Greater LA and ETp are linked with better rainfall capture

PhD: Sarah Kemp

Presence of leaf structures like hairs increases particle capture

Blanusa et al. (2015), Urban Forestry and Urban Greening, 1095-1101

Species differ!

Main messages from ‘green infrastrucutre ecosystem services’ research to date:

NOT ALL PLANTS ARE THE SAME! The complexity of leaf and canopy structure in herbaceous perennial plants (e.g. presence of hairs, larger LAI) AND higher ETp rates contribute to their increased ability to provide multiple / additional ecosystem services When possible, plant choices for our green spaces should not only be based on the survival, but also on the ability of plants to provide MULTIPLE ecosystem services

Thanks J Dr Madalena Vaz Monteiro, Sarah Kemp, Dr Federica Fantozzi, Dr Ross Cameron

Dr Anne Verhoef

Val Jasper, Mike Dawes, Matthew Richardson

Funding: