ARS | Publication request: Carbon pools in an arid shrubland in Chile under natural and afforested conditions

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 20, 2010
Publication Date: January 3, 2011
Citation: Perez-Quezada, J.F., Delpiano, C., Franck, N., Snyder, K.A., Johnson, D.A. 2011. Carbon pools in an arid shrubland in Chile under natural and afforested conditions. Journal of Arid Environments. 75:29-37.

Interpretive Summary: Although arid and semiarid ecosystems cover more than 30% of the global continental area and are estimated to contain 20% of the global soil C pool,. little is known about carbon (C) storage in these ecosystems. Similarly, arid and semiarid regions make up about 41% of the continental area of Chile, but estimates of C pools for these areas have not been previously reported. Our study determined the C pools of biomass, litter, and soil for natural and afforested sites in a Mediterranean shrubland in Chile. The natural site had a vegetation cover of 31%, which was dominated by Flourensia thurifera (Molina) DC., Gutierrezia resinosa (S.F. Blacke), and Heliotropium stenophyllum (Hook. & Arn.). The afforested site had a vegetation cover of 12%, which was dominated by F. thurifera, G. resinosa, and two-year-old planted trees of Acacia saligna (Labill.) H.L. Wendl. Mathematical equations were constructed to estimate shrub biomass from tree and canopy measurements. The C contents of biomass and soil were also determined. Calculated shrub volumes were strongly associated with plant biomass. Total plant biomass was 3.69 t C ha-1 at the natural site and was 0.82 t C ha-1 at the afforested site. Soils were the largest C pool at both the natural site (89% of total C) and afforested site (94% of total C). Pools of C were lower at the afforested site than the natural site for all soil depths. Total ecosystem C at the natural site was 36.5 t C ha-1 compared to 21.1 t C ha-1 at the afforested site. These measurements represent an important baseline to assess long-term effects of afforestation on ecosystem C pools in Chile.

Technical Abstract: Arid and semiarid regions comprise 41% of the continental area of Chile, but no estimates of carbon (C) pools have been reported for these areas. This study quantified the C pools of biomass, litter, and soil for natural compared to afforested (two-year-old Acacia saligna (Labill.) H.L. Wendl.) sites in a Mediterranean shrubland in Chile. The natural site had a vegetation cover of 31%, which was dominated by Flourensia thurifera (Molina) DC., Gutierrezia resinosa (S.F. Blacke), and Heliotropium stenophyllum (Hook. & Arn.). The afforested site had a vegetation cover of 12%, which was dominated by F. thurifera, G. resinosa and A. saligna. Allometric functions were constructed to estimate shrub biomass, and C content in biomass and soil was determined. Calculated shrub volumes were highly correlated with plant biomass (R2>0.73), and estimates of total plant biomass were 3.69 and 0.82 t C ha-1 for the natural and afforested sites, respectively. The soil was the largest C pool for both natural and afforested sites (89% and 94% of total C, respectively) and was significantly lower at the afforested than natural site at all soil depths. The natural site had a total ecosystem C of 36.5 t C ha-1 compared to 21.1 t C ha-1 for the afforested site. These measurements represent an important baseline to assess long-term effects of afforestation on ecosystem C pools in Chile.