Fig. 6. Regolith nitrate N (µg g^–1 based on oven dry soil weight) for quarterly soil cores taken in the extreme drought of 2001–2002, and the following wet year of 2002–2003. An arrow indicates the region of the regolith (on average) that is weathered bedrock (WBR) at each site. (a) Data from the healthy coastal sage scrub site at Lake Skinner (+CSS). Note the distribution of nitrate N that is mainly concentrated within the surface 25 cm. However, there is not as strong an L-shape to the distribution as is evident at the –CSS site. (b) Data from the degraded coastal sage scrub site at the base of the Box Springs Mountains (–CSS). Note the L-shape to the curves indicating the strong stratification of nitrate N within the top 25 cm of the regolith.