Green Roofs - Living Architecture Monitor Winter 2020 - 28

HETEROGENEOUS SUBSTRATE DEPTH SUPPORTS GREATER
FUNCTIONAL DIVERSITY WITH COMPARABLE STORMWATER
RETENTION AND SUBSTRATE TEMPERATURE SERVICES
TO SEDUM-DOMINANT GREEN ROOFS
Terrell Roulston1, Amy Heim1*, Jeremy Lundolm1
1
Saint Mary's University, Halifax, Nova Scotia, Canada
*Corresponding Author: Heim.amy.e@gmail.com
This study investigates the potential for spatial heterogeneity in substrate depth as a means to increase coexistence of functionally
diverse plant species on green roofs. A treatment with heterogeneous substrate depths of 15 cm ridges alternating with five cm furrows
was vegetated using hydroseed mixtures of forbs and graminoids on the ridges and pre-vegetated mats with succulent species (Sedum
dominant) on the furrows. This was compared to a treatment with homogeneous substrate depth of 10 cm covered with pre-vegetative
mats of succulents that is representative of a standard extensive green roof design. Both treatments reached high plant cover and
successful coexistence was observed between the different growth forms in the mixed vegetation treatment over two growing seasons.
The mixed vegetation treatment performed similar stormwater retention and substrate temperature ecosystem services in comparison
to the succulent-only treatment. The hydroseeding method showed potential for use in green roof applications. Future research on
the effects of substrate depth and topography and hydroseeding on green roofs on a larger scale is needed to determine the validity of
these methods in industrial applications.
Key words: green roof, spatial heterogeneity, substrate depth, hydroseeding

THE INFLUENCE OF MICROCLIMATES CREATED
BY PHOTOVOLTAIC PANELS AND IRRIGATION
ON GREEN ROOF ECOSYSTEM PROPERTIES
Laura Holloway 1, Olyssa Starry 2 *, Rose McClung1, Todd Rosenstiel 1
1
Biology Department, Portland State University, USA
2
University Honors College. Portland State University, USA
*corresponding author: ostarry@pdx.edu
Substrate organic matter, which is composed of living and dead organic materials, influences plant health, water absorption, root
hydraulic conductance, abundance of mycorrhizal fungi, and carbon cycling. Despite this link between substrate and green roof ecosystem function, little information is available on how green roof design elements influence substrate properties and how these change
over time. This study aimed to determine how green roof substrate properties and ecosystem functions will be altered when paired
with photovoltaic (PV) panels under different planting and irrigation scenarios. We found differences in green roof plant establishment
based on stress gradients and physiological traits, with PV panels providing a refuge for less stress-tolerant species. We also provide
evidence of increased arbuscular mycorrhizae and ergosterol in green roof treatment areas with lower substrate moisture content. In
addition to the direct effects of green roof microclimate on plant community composition, indirect effects on below ground root and
substrate processes as well as potential carbon storage should also be considered.
Key words: green roof, Sedum, soil development, SOM, green roof management, mycorrhiza
LIVING ARCHITECTURE MONITOR / WINTER 2020 / 28

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Green Roofs - Living Architecture Monitor Winter 2020

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