THE EFFECTS OF ORGANIC AMENDMENTS ON THE RESTORATION OF A DISTURBED COASTAL SAGE SCRUB HABITAT

The effectiveness of organic mulch as a simple means of enhancing the restoration of disturbed lands by providing a competitive edge to nati ve perennials, such as Artemisia californica (California sagebrush), o ver exotic annuals, such as Avena fatua (wild oat), was studied by inv estigating the effect of organic amendments on microbial activity and nitrogen immobilization through both soil analysis and aboveground pla nt growth. The addition of organic amendment resulted in an increase i n microbial activity, a parallel increase in nitrogen immobilization, and no significant differences in total soil nitrogen. It is likely th at nitrogen was gradually being removed from its more available form o f nitrate and being immobilized in the tissues of the increasing micro bial biomass. The survival rate of planted native perennial seedlings of A. californica in organic amended plots was almost double that of c ontrol-plot seedlings, and plant volume was significantly higher. When the availability of nitrogen was reduced through increased immobiliza tion, amended plots established an environment more conducive to nativ e perennial shrubs, allowing them to outcompete exotic annuals for wat er and nutrients. This simple procedure could have major implications for enhancing the restoration of disturbed lands.