Discussion

    Our analysis suggests that the presence of Cheseboro Road has been an important factor influencing Valley Oak recruitment at Cheseboro Canyon between 1994 and 2001.  16 of the 17 specimens are located within 20 meters of the road, a fact which leads to a discussion of why the road might be having such a large affect on recruitment.

  In a previous study, we looked at aerial photos of Cheseboro Canyon obtained from the CSUN map library and determined that Cheseboro Road was paved in 1994.  When a road is paved, it can no longer absorb water, and rainfall tends to runoff and collect on either side.  This fact, along with road splash from passing vehicles, often leads to increased vegetation along roads, especially in areas where water is a scarce commodity.  Passing cars may also keep animals from coming too close to roads.  If this is the case at Cheseboro, it may be significant, given the fact that numerous studies of Valley Oak throughout its range conclude that predation by rodents and small mammals may limit recruitment at many sites.  

  Many studies often list grazing as another potential limiting factor to Valley Oak recruitment.  Grazing ended at Cheseboro in 1985, and yet the first recruit does not occur until 1994, the year that the road was paved.  This, along with the fact that only 1 recruitment in the data set occurred farther than 20 meters from the road, seems to suggest that Cheseboro Road may be a strong explanatory variable influencing recruitment, and that future recruitments may be expected to occur with similar proximity to the road.  If this is so, it may mean that water that was once available to Valley Oak throughout the site may no longer be available, and thus saplings are increasingly relying on water provided by the affects of road-paving.