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Arboriculture & Urban Forestry Online
Volume 49, Issue 3 — May 2023

Hardscape of Soil Surface Surrounding Urban Trees Alters Stem Carbon Dioxide Efflux

Thomas E. Marler

Abstract: The diel patterns of stem carbon dioxide efflux (Es) were quantified for 8 lignophyte tree species using paired trees, with one tree surrounded by hardscape from the bole to the canopy perimeter and the second tree surrounded by grass or mulch. Stem Es was measured at a height of 30 to 40 cm on the boles, and measurements were made about every 2 hours during 31-hour measurement campaigns. Nocturnal Es was similar for the hardscape trees and the trees without hardscape. Trees surrounded by hardscape exhibited daytime Es that was 73% greater than nocturnal Es. In contrast, trees surrounded by grass or mulch exhibited daytime Es that was only 55% greater than nocturnal Es. The diurnal maximum of Es was in the morning for trees surrounded by hardscape but was in the afternoon for trees growing in grass or mulch. The results indicated root-respired carbon dioxide was transferred to the bole through daytime transpiration, and more of this carbon dioxide was released from the bole surfaces for trees surrounded by hardscape.

Keywords: Carbon Cycle; Philippines; Stem Respiration

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