UC Davis Department of Plant Sciences

RIPARIAN ECOSYSTEM RESPONSE TO TIMBER HARVSESTING FOR THE PURPOSE OF RESTORING ASPEN


Canopy Cover & Solar Radiation

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Vegetative canopy cover is a critical factor in riparian ecosystems because it blocks solar radiation reaching stream surfaces and thus moderates water temperature and influences in-stream primary production. Additionally, vegetative canopy also serves as an input of nutrients and organic matter to stream systems and provides physical habitat for stream biota.

There were no significant changes in stream canopy cover or solar radiation inputs along the treatment reaches of Pine Creek (PC4 to PC1) or Bogard Creek (BO5 to BO1) in response to Pine-Bogard Phase 2 conifer removal. The lack of significant change is not surprising, given that Phase 2 conifer removal did not occur within the riparian zones of Pine and Bogard Creeks.

There were significant decreases in canopy cover along the treatment reaches of Pine Creek (PC1 to PC4) and Bogard Creek (BO1 to BO5) in response to Pine-Bogard Phase 3 conifer removal (P < 0.002). Canopy cover decreased from a mean of 64 to 55 % along Pine Creek and from a mean of 64 to 39 % along Bogard Creek. Correspondingly, there was a significant increase in the amount of solar radiation arriving at each reach (P < 0.005) (Fig. 6a and b). The significant changes were expected, as Phase 3 conifer removal was carried out directly adjacent to Pine and Bogard Creeks.

 

 

Figure 6. The mean and standard error of percent solar radiation arriving at (a) Pine Creek between stations PC4 and PC1 before (2005) and after (2008) January 2008 Phase 3 conifer removal, (b) Bogard Creek between stations BO5 and BO1 before (2005) and after (2008) January 2008 Phase 3 conifer removal, and (c) Bailey Creek between stations BR1 and BR6 before (2003) and after (2007) September 2006 conifer removal.  

Canopy cover significantly decreased from a mean of 64 to 55 % along the treatment reach of Bailey Creek (BR1 to BR6) in response to conifer removal (P < 0.005).  Correspondingly, there was a significant increase in solar radiation arriving at Bailey Creek following treatment for the months of May through August (P < 0.01) (Fig. 6c).The significant changeswere expected, as portions ofas portions of Bailey Creek conifer removal were carried out directly adjacent to the stream.

 

 

       

 

     

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