Using Chlorophyll a Fluorescence Imaging to Select Desiccation-Tolerant Native Moss Species for Water-Sustainable Green Roofs

Ricardo Cruz De Carvalho,Jorge Marques Da Silva,Cristina Branquinho,Teresa Afonso Do Paço

doi:10.3390/w12061748

Abstract

Green roofs have been more thoroughly investigated in the last few years due to the potential benefits they offer to ecosystems in urban areas (e.g., carbon sequestration, particle retention, heat island effect attenuation). However, current climate change models predict an increase in desertification, with an increase in temperature and decrease in rainfall, which means there is an increasing demand for green roofs with lower water consumption. Vegetation with very little water requirements, such as desiccation-tolerant mosses, has shown a potential to complement or substitute for vascular species, increasing the sustainability of lower water use in green roofs. In this study, we use chlorophyll a fluorescence imaging to screen for bryophytes with adequate physiology to be used in green roofs placed in at-risk areas with prolonged drought episodes. Apart from Hypnum cupressiforme, all selected species presented a high potential for use in those conditions, particularly Didymodon fallax, Grimmia lisae, Pleurochaete squarrosa, and Targionia hypophylla. Chlorophyll a fluorescence imaging technology proved to be a simple and non-invasive tool for a fast screening of these poikilohydric organisms, to be used in future studies of bryophyte biology, but more importantly in the green roof industry.

Highlights

Green roofs consist of plant-based structures that are placed on a waterproof layer on top of residences, factories, offices, and other buildings increasing the services provided by green spaces in urban areas [1,2,3,4,5,6]
Chlorophyll a fluorescence analysis shows that, in general, recovery was very similar for all bryophytes, except for H. cupressiforme, which had a slower recovery, reaching their optimal performance at T6
When the samples were dry at T0 and T13 chlorophyll a fluorescence was absent in all samples

Summary

Introduction

Green roofs consist of plant-based structures that are placed on a waterproof layer on top of residences, factories, offices, and other buildings increasing the services provided by green spaces in urban areas [1,2,3,4,5,6]. In addition to an improvement of urban aesthetics, green roofs attenuate flood effects, increasing the retention time of rainwater [5,7]. They contribute to the thermal regulation of buildings and reduce the urban heat island effect, as well as mitigating heat loss during the winter [8,9]. The increased popularity of green roofs began in northern Europe, in areas with cold and humid climates (e.g., Germany, Netherlands) These environments enabled easier maintenance of these structures at a low cost without resorting to irrigation [9]. In the Mediterranean area or in regions with similar latitudes (e.g., California, south-western Australia, South Africa, Chile), characterized by hot and dry summers, the use of classical green roofs requires irrigation, to maintain both plant survival and aesthetic quality [14]

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Discussion

Conclusion