Articles
Reduction of atmospheric CO2 as affected by the type of photosynthesis of green roof plants
Article number
1417_34
Pages
285 – 290
Language
English
Abstract
Urban green roofs are a sustainable alternative to conventional roofs.
Indeed, green roofs contribute to an aesthetically improved urban environment, support biodiversity, and provide many other ecosystem services, including the reduction of atmospheric CO2. Succulents (CAM photosynthesis plants) are mostly used on green roofs, thanks to their low water requirements.
However, the question arises whether, in xerothermic regions under intense water stress, CAM plants contribute to the reduction of atmospheric CO2 compared to C4 and dry-tolerant native C3 plants.
Thus, in the present work the a) CAM species Sedum sediforme and Mesembryanthemum cordifolium, b) C3 Mediterranean species Pallenis maritima and Cistus × purpureus ‘Alan Fradd’, and c) C4 species Atriplex halimus and Muhlenbergia capillaris were grown in a simulated green roof in a greenhouse, on a 10-cm deep substrate, under regular and sparse irrigation.
Plants were trimmed so that the plant canopy covered the surface of the culture container, and all canopies were maintained at the same height.
CO2 measurements were taken in transparent domes above each container in the morning, midday, and evening at regular intervals during spring and summer.
At both irrigation frequencies, species with C3 and C4 photosynthesis showed similar CO2 assimilation during the day and emission at night, having a positive day-night CO2 balance, while in CAM species, only M. cordifolium had a positive day-night CO2 balance, while S. sediforme appeared to emit a significant amount of CO2 during the day, which was not compensated by the CO2 absorbed at night. S. sediforme, P. maritima, and M. capillaris were the least efficient in CO2 absorption compared to the other species of the same photosynthesis type.
Thus, to ensure the contribution of green roofs to the reduction of CO2 in semi-arid climates, appropriate plant species should be used.
Indeed, green roofs contribute to an aesthetically improved urban environment, support biodiversity, and provide many other ecosystem services, including the reduction of atmospheric CO2. Succulents (CAM photosynthesis plants) are mostly used on green roofs, thanks to their low water requirements.
However, the question arises whether, in xerothermic regions under intense water stress, CAM plants contribute to the reduction of atmospheric CO2 compared to C4 and dry-tolerant native C3 plants.
Thus, in the present work the a) CAM species Sedum sediforme and Mesembryanthemum cordifolium, b) C3 Mediterranean species Pallenis maritima and Cistus × purpureus ‘Alan Fradd’, and c) C4 species Atriplex halimus and Muhlenbergia capillaris were grown in a simulated green roof in a greenhouse, on a 10-cm deep substrate, under regular and sparse irrigation.
Plants were trimmed so that the plant canopy covered the surface of the culture container, and all canopies were maintained at the same height.
CO2 measurements were taken in transparent domes above each container in the morning, midday, and evening at regular intervals during spring and summer.
At both irrigation frequencies, species with C3 and C4 photosynthesis showed similar CO2 assimilation during the day and emission at night, having a positive day-night CO2 balance, while in CAM species, only M. cordifolium had a positive day-night CO2 balance, while S. sediforme appeared to emit a significant amount of CO2 during the day, which was not compensated by the CO2 absorbed at night. S. sediforme, P. maritima, and M. capillaris were the least efficient in CO2 absorption compared to the other species of the same photosynthesis type.
Thus, to ensure the contribution of green roofs to the reduction of CO2 in semi-arid climates, appropriate plant species should be used.
Authors
M. Papafotiou, M. Trigka, G. Liakopoulos, A. Koutsardakis, P. Dariveris, D. Karagianni
Keywords
CAM plant, C3 plant, C4 plant, carbon sequestration, extensive green roof, Mediterranean native plants, succulents, urban CO2
Groups involved
- Division Vine and Berry Fruits
- Division Plant-Environment Interactions in Field Systems
- Division Horticulture for Human Health
- Working Group Vaccinium Species and Management
- Working Group Rubus and Ribes Species and Management
- Working Group Kiwifruit Culture and Management
- Working Group Strawberry Culture and Management
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