How to measure average amount of sun light hitting silvopasture floor?

[Joanne Vaughn]

What is a good simple way to estimate the average amount of sunlight hitting the pasture part of the silvopasture over an area of say 10 acres? The goal is to determine if further thinning may be needed to optimize pasture growth.

Thanks for any suggestions.

[Diane Mayerfeld]

I would also love to hear what others have to say about this.  

What I  have done is take 2 HOBO Onset temperature / light loggers to my site on an overcast day.  I check to make sure the clocks in both are synchronized and the loggers are set to measure light at 10 second intervals.  I set one up in open pasture.  Then I take the other one and set it up at random locations in the silvopasture for 3 minutes each.  When I am moving the logger between locations I cover it so it  is easy to tell when it is not set up to record.  

Then I take the ratio of light in the silvopasture locations to light in the open pasture at the same time, and average the ratios.  I only use the middle 2 minutes of light values for the shaded locations.  

I think the temperature loggers I used cost about $60 each.  

[Joanne Vaughn]

Thank you for your response. We are asking the question how much light is actually hitting the pasture forage beneath our tree canopy. We would like to know how much tree cover affects our pasture growth. 

After thinning  trees will grow through the season and and attempt to close cover above. 

The amount of filtered light hitting the ground will vary through the day and growing season.

The amount of filtered light hitting the ground forages will vary as trees grow and age.

In our particular ecosystem, 43N-77.7W I believe that total growing system sunlight is the limiting factor for forage growth; we have many overcast days. Our particular location gets a lot of moisture from higher ground so we did not even notice the drought of last year. 

Gabriel and Chedzoy (webinar) and Chedzoy and Smallidge ("Thinning woodlots and plantations to create Silvopasture) throw out the number of something like 60 sq ft of tba but that number (almost certainly) may need to be adjusted for different locations.

We keep year to year records of sheep days grazing on locations of our land. Over time we should begin to discern a pattern of productivity with respect to tree density and average light on the forage. 

We are thining of using a Lightscout DL 100

taking one measurement in a spot in full sun for 24 hrs and using 2 others at marked locations in the silvopasture.

Different days and seasons can be normalized.

[Joanne Vaughn]

What are you hoping to learn?

Diane Mayerfeld said:

I would also love to hear what others have to say about this.  

What I  have done is take 2 HOBO Onset temperature / light loggers to my site on an overcast day.  I check to make sure the clocks in both are synchronized and the loggers are set to measure light at 10 second intervals.  I set one up in open pasture.  Then I take the other one and set it up at random locations in the silvopasture for 3 minutes each.  When I am moving the logger between locations I cover it so it  is easy to tell when it is not set up to record.  

Then I take the ratio of light in the silvopasture locations to light in the open pasture at the same time, and average the ratios.  I only use the middle 2 minutes of light values for the shaded locations.  

I think the temperature loggers I used cost about $60 each.