Carbon flux in arid and semiarid area shrublands, especially in old-growth shrub ecosystems, has been rarely studied using eddy covariance techniques. We are taking long-term eddy covariance measurements at 3 distinct stands of chaparral at Sky Oaks Field Station. We have found that over a 100-year old-growth chamise-dominated chaparral shrub ecosystem can be a carbon sink, from -96 to -155 g C m-2 yr-1 under normal weather conditions. It can also be a weak sink of -18 g C m-2 yr-1 and a strong source of 207 g C m-2 yr-1 during a severe drought. The annual sink strength of carbon in at the old-growth stand during a 7-year period was -52 g C m-2 yr-1. Our studies indicate that, in contrast to previous thought, the old-growth chaparral shrub ecosystem can be a significant sink of carbon under normal weather conditions and, therefore, be an important component of the global carbon budget.
This is a long-term project, and nearly every member of GCRG has contributed to the project.
