.5- 



E 1.0 



if 0.5 



LlJ 



Natural invasion 

 of S. alterniflora 

 Oct Nov 

 1973 



a 26 Nov 1973 

 ■ 25 Apr 1972 



20 



40 



60 



Slope distance ( m ) 



Figure 49. Unplanted transect, No. 6, Snow's Cut, 

 25 April 1972 to 26 November 1973. 



There was little difference in elevation gain between the other two 

 planted blocks; the change on these averaged around 15 centimeters. 

 Sediment accumulation definitely decreased in the zone immediately down- 

 slope of the vegetation. 



Records on the four cross sections through the unplanted strips indi- 

 cate little change in elevation during the period of record (Figs. 46 

 through 49). Section 2 (Fig. 46) upstream from the others, exhibited the 

 most accumulation. The effect of volunteer seedlings is clearly visible 

 in the most recent survey on all of these unplanted areas. A minor amount 

 of erosion has occurred along these cross sections, largely at the bottom 

 of the slope. 



There was no way to predict what elevations would exist along the 

 unplanted cross sections if no S. alterniflora were planted in the vicinity. 

 The planted blocks did trap substantial amounts of sediment, and the inter- 

 pretation is that this, along with the behavior of the unplanted strips is 

 reasonable evidence of a strong stabilizing effect of this vegetation. 

 Also, the slowness with which S. alterniflora invaded the unplanted strips 

 appears to indicate that natural colonization of the area would have been 

 extremely slow in the absence of such plantings. No seedlings appeared 



97 



