Abstract
Three woody shrub species [cleyera (Ternstroemia gymnanthera Thunb. ‘Conthery’), Indian hawthorn (Rhaphiolepis indica L.) and loropetalum (Loropetalum chinensis Oliv.‘Ruby’)] were container-grown for one growing season in 2008 using either pinebark (industry standard), clean chip residual or WholeTree (derived by-products from the forestry industry) as potting substrates and then transplanted into the landscape in 2008. An Automated Carbon Efflux System was used to continually monitor soil CO2 efflux from December 2010 through November 2011 in each species and substrate combination. Changes in soil carbon (C) levels as a result of potting substrate were assessed through soil sampling in 2009 and 2011 and plant biomass was determined at study conclusion. Results showed that soil CO2-C efflux was similar among all species and substrates, with few main effects of species or substrate observed throughout the study. Soil analysis showed that plots with pinebark contained higher levels of soil C in both 2009 and 2011, suggesting that pinebark decomposes slower than clean chip residual or WholeTree and consequently has greater C storage potential than the two alternative substrates. Results showed a net C gain for all species and substrate combinations; however, plants grown in pinebark had greater C sequestration potential.
Highlights
There is growing concern that anthropogenic driven changes in the earth’s surface temperatures may impact the future global environment[1,2]
Growth data indicated all three species performed regardless of potting substrate used in container production, similar to previous results reported by Marble et al.[38]
Allison and Murphy[47] investigated wood and bark decomposition rates of several pine species, including loblolly pine (Pinus taeda L.) which was the species used for clean chip residual (CCR) and WT substrates in this study; results showed that ~16.9% of wood C was oxidized compared to 8.6% for bark
Summary
There is growing concern that anthropogenic driven changes in the earth’s surface temperatures may impact the future global environment[1,2]. Extensive research has focused on reducing GHG emissions and increasing carbon (C) storage in agricultural production[1,10,11,12,13,14,15,16,17] Due to their large land area coverage in the U.S, most C sequestration research has focused on row crop (113 million ha) and forest (300 million ha) production systems[18,19]. While there is some indication that ornamental shrubs may impact C sequestration, little or no data currently exist for most landscape species Another often ignored key C sequestration pathway (other than plant biomass) is the substrates these plants were grown in during production. Marble et al.[30] estimated that planting an average 11.5 L nursery container filled with a PB potting substrate would instantly sequester ~1.6 kg of C from the substrate alone, with future C gains realized as plant biomass increases
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