Hello all,
I am about to estimate leaf area index (in the leafed period) and canopy area index (in the leafless period) of some sparse oak forest stands. Since these forest are very sparse in density, we should consider, first, some individual trees to estimate and generalize these individual estimates to whole stands then. So, we need to estimate LAI and CAI of single trees. Meanwhile, change detection of aforementioned indexes in various phenological stages is the reason for using hemispherical photos.
Best wishes,
Omid,
Hi Omid,
If your question is about tools to quantify surface area, you should try using image processing softwares such as Image J (the Fiji version is the latest). It can help you select regions of interest on your photograph and calculate SA for those. You will need some standardisation for the image though.
I hope this helps.
Naveen.
Please check the papers that Yaseen Mustafa and I wrote on this matter. They contain some detailed descriptions on how to measure LAI in the field.
Dear Dr. Stein,
It is nice to hear from you! Ok. I will see your papers and write you back if questions arises and , of course, if you don't mind.
Thank you very much,
Omid,
Omid you can use IMage J software for this purpose. Another instrument is LAI 2200 which will give you direct LAI Reading.
Thank you very much dear Nizami,
We are going to do that by using a hemispherical camera.
Dear Omid
You can not calculate single tree LAI using hemispherical photos. They are applicable at stand level. If you can focus on isolated trees with a clear sky as their background, you can simply use ground-based photogrammetry and run some image processing for calculating different indices like LAI or other related indices like transparency of the crown. For the calibration, you might need to directly measure LAI of some trees.
Dear Dr. Sohrabi,
Thank you very much for your very good reply.
But about calibration, as we are going to estimate phonological changes of LAI, that means we must do directly measures of trees on a regular schedule (e.g.every once in a while)?
Thank you again,
Hello Omid,
I agree with Hormoz's statement: it's not possible to calculate LAI for single three using hemispherical photos technique. By the way, I suggest you to follow Axel's suggestion about to see Waring's paper, since he has done a good job in Australia about LAI investigations.
Good luck!
Regards,
Sergio Silva
Hello Omid,
I am currently writing up a study using hemispherical photos in dense conifer stands and came across this paper which may interest you.
Bréda, N.J.J. 2003. Ground-based measurements of leaf area index: a review of methods, instruments and current controversies. Journal of Experimental Botany 54:2403-2417.
The paper differentiates between LAI, plant area index (PAI) and surface area index (SAI), the latter two including branches and stems. It also describes differences between direct and indirect methods of measuring LAI and the formulas used.
As mentioned previously, it seems the use of hemispherical photos is more suited to stand level assessments rather than individual trees.
Hopefully this reference is useful.
all the best,
Anya
Here's a paper you might find useful: "Validation of LAI and FPAR products" (http://data.auscover.org.au/xwiki/bin/view/Good+Practice+Handbook/LAIFPARValidation?xpage=office&attachment=LAIandFPAR_Validation_For_AusCover_Greenbook_v13.docx)
And here's one of the instruments discussed that is good for measuring LAI in the field: http://www.cid-inc.com/products/leaf-area-lai/plant-canopy-imager
Hope that helps!
Hi Omid,
I know this is probably a bit late, but I recommending to take a look at the following study to estimate LAI for individual trees.
Nowak, D.J., 1996. Estimating leaf area and leaf biomass of open-grown deciduous urban trees. Forest Science 42, 504–507.
Nowak (1996) estimates LAI of trees in urban environments that are often isolated from other trees using allometric equations. The author developed equations to calculate LAI using diameter at breast height and crown parameters.
Tyler
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