Required inputs for calculating leaf surface area

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pete.stewart
Posts: 7
Joined: Tue Apr 03, 2018 1:19 pm

Required inputs for calculating leaf surface area

Post by pete.stewart » Wed Nov 14, 2018 8:11 am

I'm wondering what are the required set of measurements (and also the optimal ones) for calculating leaf surface area.
I'm wanting to use Eco to help me make calculations of the Importance Value of ash trees in series of parks, and trying to settle on a relatively quick data collection protocol.
Are species and dbh by themselves enough for a rough estimate? To improve the estimate should I also measure height, spread, and other variables? Thanks!
azelaya
i-Tree Team
Posts: 329
Joined: Fri Jun 27, 2008 10:50 am

Re: Required inputs for calculating leaf surface area

Post by azelaya » Wed Nov 14, 2018 11:14 am

The following information is extracted from the Use of DIrect Measures by i-Tree Eco v6 document which describes how tree measurements are used for various estimates https://www.itreetools.org/eco/resource ... nships.pdf

DERIVED VARIABLES
• Leaf area is estimated using:
o Species – to identify shade coefficient
o Total height – to estimate height of the crown
o Crown base height – to estimate height of the crown
o Crown width – to identify crown width dimension
o Percent crown missing – to modify base leaf area for actual amount present

In short, your leaf area estimates will be improved by providing more canopy measurements which are used by the model to estimate crown volume and adjust for missing areas, etc. Otherwise, the model is estimating these which may be more inaccurate especially at the individual tree level. There is not a known factor to describe the accuacy difference, but you could always try running a measured tree with and without canopy measurements to compare estimates and get an idea of differences in estimates.
A member of the i-Tree Team
pete.stewart
Posts: 7
Joined: Tue Apr 03, 2018 1:19 pm

Re: Required inputs for calculating leaf surface area

Post by pete.stewart » Thu Nov 15, 2018 9:59 am

Thanks ! That's really helpful.
Am I getting this correct: If I don't enter data for 'Percent Crown Missing', Eco will use 13% as a default for all species? (From the 'Eco Guide to Data Limitations' pdf)
azelaya
i-Tree Team
Posts: 329
Joined: Fri Jun 27, 2008 10:50 am

Re: Required inputs for calculating leaf surface area

Post by azelaya » Thu Nov 15, 2018 11:10 am

Yes. your understanding is correct as a default of 13% will be applied as the Percent crown missing to all trees if you decided not to collect the "Crown" measurments.

You may have noticed in Eco that there are (4) measurements that are required if you toggle on the "Crown Size" option in project configuration.
Height to live top
Height to crown base
Canopy width: East-to-West & North-to-South (2 measurements)
Percent crown missing

Basically, these are all associated and you will need to provide all or nothing with this particular data option.
A member of the i-Tree Team
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