I have create two site table files, one for 1890 and one for 1986. I will use both files and data given to me by Dr. Diggins to try to construct quadrats on simforest. I will continue to search for more up to date weather data and contiue my literature searches.

~Erin K. Pfeil

I'm not entirely sure what to do with the equations. Water stress is low for Zoar Valley, so you could try changing the value so that it is smaller then .4 or if that makes it worse experiment and try a larger number until the equation works. Since its very difficult to inquire about these things to the creators of the simforest program, that is what i would do. Perhaps if you can get it to work using a different value, we can figure out the meaning of the value itself or perhaps there is a problem somewhere else in the equation. I also suggest raising the amount of available light, if I understand the previous blog entry correctly. We may be underestimating it far more then we thought. If the equipment was available, it would be best to find the available light ourselves, but maybe I can find a value from a study done on a similar old growth forest.

Regarding the excel file, I have looked at it and it does not have data for 2006. Soooo i will use the newest one I have, to create the new site quality table. I am also in the process of emailing the site quality table I have already created and send that along as well.


~Erin K. Pfeil

Progress on NetLogo so far

After going through the equations used in NetLogo and comparing them to those used in SimForest, I saw that for the most part these equations are functioning and being used correctly in combination with other equations. Currently, I am going through the values generated by these equations to see if the values being generated are actually correct.

I’ve found a few issues with the equations after going through them, mostly related to the recruitment equation, one of the three major equations used to drive the model (the other two being birth and death). Recruitment determines the number of new saplings planted depending on a particular species’ tolerance to light/shade (represented in the program on a scale of 1 – shade-intolerant, 2 – shade intermediate, or 3 – shade-tolerant). Two parts of the main recruitment equation involve the variable sitequality, which is itself an equation involving three other variables: wiltfactor, nitrogenfactor and tempfactor.

One problem that arose involves the wiltfactor equation, which incorporates the variable “waterstress”. This variable is defined in the SimForest equation editor as “[returning] the water stress at the site in the current year, computed based on the site's properties using a complex equation”. However, no other information is given on how to actually calculate the value. This creates a problem as the value we are currently using for waterstress in the wiltfactor equation (arbitrarily chosen to be 0.4) results in the equation producing a value of zero. This occurs because the wiltfactor equation is designed to return the higher of two values, either 0 or a value produced by list ((1.0 - ((waterstress / wlMax) ^ 2))) (0) In this case, the value that comes from this equation is negative, so 0 is always chosen. This in turn leads to the entire sitequality equation to be zero, as sitequality is defined as

tempfactor * nitrogenfactor nitrogen * wiltfactor

Some value needs to be found for waterstress that allows wiltfactor to return a non-zero value, so that it can in turn be used in sitequality

Another second problem that arises is with the variable representing available light. This calculation represents the amount of light available at the current tree's height, and the creators of SimForest admit that they have not included the actual equations for inspection in either their Glass Box or Black Box versions, which makes it difficult to determine if the value chosen is correct. In this case, we have again chosen an arbitrary value, 0.74, for available light.

This is a problem when we get to the recruitment equation. When light = 1, the formula availLight >= 0.989999 and sitequality > 0.0 is used to determine whether or not to perform the recruitment equation or just set recruitment to zero. Since 0.74 is always <>

A similar problem arises when light = 2. The equation used is minSaplingLight > availLight and availLight < light =" 2.

The two values for available light needed for light = 1 and light = 2 are not compatible, but the available light must be calculated so that one of these equations does not keep constantly returning 0 for tree recruitment.

NOTE: light = 3 has not been discussed yet because it relies upon the sitequality equation, which is currently returning 0.

Resolving these two issues is important in allowing development of the model to continue. In the meantime, I am working on adding the rest of the equations that the model uses (Growth, Age, etc), particularly those pertaining to the growth of the tree itself, which I am planning on incorporating into the NetLogo model if possible.

Forest Dynamics

http://research.microsoft.com/displayArticle.aspx?0rc=n&id=2029

Weather Data

Hello Everyone

Here is a site were I finally found weather data that begins in 1900 and runs up to 2006.

http://cdiac.ornl.gov/epubs/ndp/ushcn/monthly.html

I chose the city of Brockport, New York. It is ~96 mi from Gowanda, but it is the closest and what I feel more similar to Zoar Valley then the given New Hampshire site parameters. I created an excel spreadsheet (through the use of the site) and highlighted which columns we will probably be using. The only thing I am having problems with is converting the data from inches to millimeters in excel and also Fahrenheit to Celsius. Can anyone tell me how to do it? I will email you the file.

~Erin K. Pfeil

Goals for NetLogo Program

Now that we are aware of the different capabilities of both the Glass Box and Black Box versions of SimForest, we are also looking to re-create some of the capabilities of these programs in NetLogo. This software will allow us to create a forest-modeling program from the ground-up, and perhaps give a little more flexibility in what we can do with either of the previously-mentioned versions of SimForest. However, doing this presents some unique challenges, since we are starting from scratch. Using the SimForest programs as a basis, we must translate their equations, which are done in Director Lingo, into the language of NetLogo, which has its own unique syntax, procedures and commands. Some of the goals to work towards are:

· getting the recruitment equation running

· incorporating different species into the simulation

· being able to plant the trees one by one

· introducing a topographical map of Zoar Valley into the simulation background

Once a running simulation has been achieved, it can be cross-checked against the other models to check if it is producing realistic values.