An examination of the effect of restoration practices on coastal sage scrub.
Authors:Phil Acosta, Duncan Ketel
Mentor:Cheryl Swift, Chair of Environmental Science Department, Whittier College
Plant community restoration is an important tool for mitigating habitat lost due to past or present land use conversion. When restoration is required to mitigate habitat loss, specified targets for community cover are often mandated. Current restoration practices often involve watering of restored areas in the first and sometimes subsequent summers to minimize mortality and improve the chances of meeting plant cover targets set out in the restoration plan. However, the effect of watering on allocation of resources to above and below ground growth and the effects of that allocation on the ability of plants to access water are not well understood. In the summer of 2012 we investigated the effect of watering on restored areas of coastal sage scrub in the Puente Hills, at Arroyo Pescadero. The sites consisted of planted and watered areas, seeded and watered areas, and seeded, un-watered restored areas and lastly areas with native shrubs that were undisturbed which functioned as control sites Three species were compared; White Sage, Purple Sage and Laurel Sumac. We hypothesized that individuals in non-restored areas would be under less water stress than individuals in restored areas, and we expected that individuals in the seeded un-watered restored area would be under less water stress than watered seed or watered planted areas. Water potentials and stomatal conductance were measured from three individuals in each site for each species. Control individuals had higher water potentials than individuals in watered restored areas. The non-watered restored areas also had higher water potentials than individuals in watered restored areas. Individuals in control and restored non-watered areas also had higher stomatal conductance. These findings indicate that the practice of watering may be problematic for long term success in restoration efforts.