Dealing with privet in a nonshrub model
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 Posts: 5
 Joined: Thu Feb 14, 2008 9:47 pm
Dealing with privet in a nonshrub model
When surveying sample plots we came upon a thicket of privet, approximately 15ft in diameter and with 40+ stems of 1" DBH or bigger, all converging below ground. Due to time constraints we have opted to measure only trees. How should we survey this? Some options we have discussed are:
Measure all stems as individual trees
Treat as 1 tree with multiple stems
Estimate the number of stems and area covered and divide into individual trees
Note as shrub cover in the nonshrub model
Is there anything you can recommend? Thanks!
Measure all stems as individual trees
Treat as 1 tree with multiple stems
Estimate the number of stems and area covered and divide into individual trees
Note as shrub cover in the nonshrub model
Is there anything you can recommend? Thanks!
 Heythatsmybike
 iTree Team
 Posts: 11
 Joined: Tue Jan 16, 2007 10:39 am
 Location: New York
The field data procedures are to count them as each a separate tree. This has happened many times in the field data collection. I have had first hand experience with this issue. In Syracuse, there was a black locust that blew over and sprouted close to 40 new individuals in a hedgerow. With many groans I measured all of the stems hoping to eliminate some of them as multistemmed trees (with no luck).
a member of the iTree Team
We have the same issues in Florida with mangroves, brazilian pepper stands, etc.
What to do It depends on the amount of times you will run across this situation.
If it's rare then measure all stems. If physically or logistically impossible:
*Only measure stems with a DBH > 3"?
*Do sub plots
Hope this helps.
What to do It depends on the amount of times you will run across this situation.
If it's rare then measure all stems. If physically or logistically impossible:
*Only measure stems with a DBH > 3"?
*Do sub plots
Hope this helps.
Francisco Escobedo
Assistant Professor
University of Florida
School of Forest Resources & Conservation
Assistant Professor
University of Florida
School of Forest Resources & Conservation
This is an interesting question, and I have certainly faced it often in the fieldthough usually with sumac or another of the native colonyforming shrubs.
What the protocol says is clear: collect them all. I see, however, some problems with this:
What do you think?

Math:
Area of all 1" stems = 40 * 0.5 * 3.1416 = 62.832
Equivalent single stem area: 3.1416 * R2 = 62.832, so R = sqrt 62.832/3.1416 = 4.3, and thus D = 8.6
What the protocol says is clear: collect them all. I see, however, some problems with this:
 Field people do not have the time that researchers do, and need to produce in an environment where time is money
 Shrubs constitute a very small percentage of the environmental benefits compared to trees; I have been told by a prominent researcher that it is typically on the order of 5% at the highest
 The speciesspecific and even genusspecific data available to the model is reportedly poor for shrubs
 Don't collect shrub data unless shrubs constitute a significant portion of the woody plants in the domain of interest
 Aggregate the stem areas and enter a single generic tree.
What do you think?

Math:
Area of all 1" stems = 40 * 0.5 * 3.1416 = 62.832
Equivalent single stem area: 3.1416 * R2 = 62.832, so R = sqrt 62.832/3.1416 = 4.3, and thus D = 8.6

 Posts: 5
 Joined: Thu Feb 14, 2008 9:47 pm
After reading the posts and speaking with itree personel, we decided that the best option is to measure all stems and aggregate as 1 tree. We then measured the total canopy as if it was 1 tree.
We found 10 stems at 3", 20 stems at 2", and 40 stems at 1"! Using the math below we found the privet to have a basal area of 14.4"... which seems to be a reasonable measurement.
Area of all 1" stems = 40 * 0.5 * 3.1416 = 62.832
2" = 20 * 1 * 3.1416 = 62.832
3" = 10 * 1.5 * 3.1416 = 47.124
Equivalent single stem area: 3.1416 * R2 = 172.788,
R = sqrt 172.788/3.1416 = 7.2,
D = 14.4
Thanks for your help!Jerry wrote: Aggregate the stem areas and enter a single generic tree.
We found 10 stems at 3", 20 stems at 2", and 40 stems at 1"! Using the math below we found the privet to have a basal area of 14.4"... which seems to be a reasonable measurement.
Area of all 1" stems = 40 * 0.5 * 3.1416 = 62.832
2" = 20 * 1 * 3.1416 = 62.832
3" = 10 * 1.5 * 3.1416 = 47.124
Equivalent single stem area: 3.1416 * R2 = 172.788,
R = sqrt 172.788/3.1416 = 7.2,
D = 14.4
Glad that was useful
Great, though I have two cautions to add:
1) It looks like I forgot to square the radius in the first step of my calculation...
So let's do that again! In general, if
N1=first number of stems, N2 = second number of stems, etc.
R1=first radius, R2 = second radius, etc.
The calculation would go like this (^2 = squared):
TotalArea = (N1 * pi * R1^2) + (N2 * pi * R2^2) + ...
For Aggregate Stem (Rt = radius of aggregate stem)
pi * Rt^2 = TotalArea
Rt = sqrt (TotalArea/pi)
Then I think your diameter should be 10.4  sorry!
2) You still have to treat the thing as a shrub, assigning it a correct shrub species and taking the shrub measurements called for (height, width, etc.). Otherwise, if UFORE thinks you have a tree, it will carry out a regression on the aggregate stem diameter and I would think that would result in a severe overestimation of parameters such as the biomass and leaf surface area that are critical to function calculations. The UFORE researchers can tell us more precisely about that.
1) It looks like I forgot to square the radius in the first step of my calculation...
So let's do that again! In general, if
N1=first number of stems, N2 = second number of stems, etc.
R1=first radius, R2 = second radius, etc.
The calculation would go like this (^2 = squared):
TotalArea = (N1 * pi * R1^2) + (N2 * pi * R2^2) + ...
For Aggregate Stem (Rt = radius of aggregate stem)
pi * Rt^2 = TotalArea
Rt = sqrt (TotalArea/pi)
Then I think your diameter should be 10.4  sorry!
2) You still have to treat the thing as a shrub, assigning it a correct shrub species and taking the shrub measurements called for (height, width, etc.). Otherwise, if UFORE thinks you have a tree, it will carry out a regression on the aggregate stem diameter and I would think that would result in a severe overestimation of parameters such as the biomass and leaf surface area that are critical to function calculations. The UFORE researchers can tell us more precisely about that.
The Forest Service's Forest Health Monitoring program uses the diameter at root collar (DRC) calcultion for multistemmed trees:
DRC = SQRT [SUM (stem diameter2)]
Round the result to the nearest 0.1 in. For example, a multistemmed woodland tree with stems of 12.2, 13.2, 3.8, and 22.1 would be calculated as:
DRC = SQRT (12.22 + 13.22 + 3.82 + 22.12)
= SQRT (825.93)
= 28.74
= 28.7
There is an easytounderstand interpretation of this method in the following document:
http://www.itreetools.org/streets/resou ... tocols.pdf
(See page 3 of PDF)
Hope I didn't muddy the water. Scott
DRC = SQRT [SUM (stem diameter2)]
Round the result to the nearest 0.1 in. For example, a multistemmed woodland tree with stems of 12.2, 13.2, 3.8, and 22.1 would be calculated as:
DRC = SQRT (12.22 + 13.22 + 3.82 + 22.12)
= SQRT (825.93)
= 28.74
= 28.7
There is an easytounderstand interpretation of this method in the following document:
http://www.itreetools.org/streets/resou ... tocols.pdf
(See page 3 of PDF)
Hope I didn't muddy the water. Scott
a member of the iTree Team

 Posts: 5
 Joined: Thu Feb 14, 2008 9:47 pm
Re: Glad that was useful
Since we are not including shrubs in our model (due to our limited timebeing a semester project) our only options are to include it as a tree (with all data taken) or note it as % shrub cover only. Since it has stems of > 1" at DBH, we are planning on counting it as a tree with DBH 10.4. Would this skew the data too much, or do you agree with the method?Jerry wrote: You still have to treat the thing as a shrub, assigning it a correct shrub species and taking the shrub measurements called for (height, width, etc.). Otherwise, if UFORE thinks you have a tree, it will carry out a regression on the aggregate stem diameter and I would think that would result in a severe overestimation of parameters such as the biomass and leaf surface area that are critical to function calculations. The UFORE researchers can tell us more precisely about that.
In the practical world, I think what you are proposing makes the most sense. One further advantage might be that, since the model extrapolates for the whole domain from the sample, you will probably have a more reasonable estimate of privet in your final species distribution this way!
I put in that second caution because I am not quite sure of how that will be treated by the model. But since you are providing a "tree" height and "crown" height/width, now that I think of it, things may work out just fine.
I put in that second caution because I am not quite sure of how that will be treated by the model. But since you are providing a "tree" height and "crown" height/width, now that I think of it, things may work out just fine.
Re: Dealing with privet in a nonshrub model
I’m also conducting a sample inventory without shrubs or herbaceous species models included and had the same question (albeit 11 years on).
Is aggregating the dbh of all stems >1”, and then measuring a single canopy width and tree height still the preferred/recommended solution to measuring privet thickets? Wouldn't it be best to cut them out and paint the stumps with glyphosate...a winwin?
What about other shrub species gone wild like eleagnus?
Amy
Is aggregating the dbh of all stems >1”, and then measuring a single canopy width and tree height still the preferred/recommended solution to measuring privet thickets? Wouldn't it be best to cut them out and paint the stumps with glyphosate...a winwin?
What about other shrub species gone wild like eleagnus?
Amy
Re: Dealing with privet in a nonshrub model
The iTree Eco protocol for considering when woody vegetation is a tree is still the same as it has always been and stated by others above. Woody vegetation that is 1 inch or greater at breast height is entered individually. The practical recommendations to aggregate stems or consider specific vegetation as shrubs are up to users to decide. These are options to consider depending on individual project objectives, time,and resources.
Below is text copied from the current Eco Field Guide pg22
What Is a Tree?
At different stages of its life, a tree can be classified as ground cover, shrub, or tree in the Eco model. The following information is adapted from the journal article “A GroundBased Method of Assessing Urban Forest Structure and Ecosystem Services” (available at www.itreetools.org under Resources > Archives) and may help Eco users distinguish between available options.
Typically, shrubs are defined as woody material with a diameter at breast height (DBH) less than 2.54 cm (1 in), whereas trees have a DBH greater than or equal to 2.54 cm (1 in). Woody plants that are not 30.5 cm (12 in) in height (e.g., seedlings) are considered herbaceous cover.
Trees and shrubs can also be differentiated by species (i.e., certain species are always trees or always shrubs) or with a different DBH minimum threshold. For example, in densely forested areas, increasing the minimum DBH to 12.7 cm (5 in) can reduce the field work required by decreasing the number of trees measured, but less information on trees will be attained.
Below is text copied from the current Eco Field Guide pg22
What Is a Tree?
At different stages of its life, a tree can be classified as ground cover, shrub, or tree in the Eco model. The following information is adapted from the journal article “A GroundBased Method of Assessing Urban Forest Structure and Ecosystem Services” (available at www.itreetools.org under Resources > Archives) and may help Eco users distinguish between available options.
Typically, shrubs are defined as woody material with a diameter at breast height (DBH) less than 2.54 cm (1 in), whereas trees have a DBH greater than or equal to 2.54 cm (1 in). Woody plants that are not 30.5 cm (12 in) in height (e.g., seedlings) are considered herbaceous cover.
Trees and shrubs can also be differentiated by species (i.e., certain species are always trees or always shrubs) or with a different DBH minimum threshold. For example, in densely forested areas, increasing the minimum DBH to 12.7 cm (5 in) can reduce the field work required by decreasing the number of trees measured, but less information on trees will be attained.
A member of the iTree Team