Cruising with the BLM

by Michael L. Hallinan

Lead Cruiser/Appraiser
Siuslaw Resource Area
Eugene BLM

For those of you who have spent many a day cruising for the Bureau of Land Management in the sodden and verdant forests Pacific Northwest, what I am about to describe has become the expected if not quite yet routine.

The name of the sale was Calpooya TS-02-254. It is located in the Eugene BLM District. The sale consisted of: twelve thinning units totaling 270 acres and ranging in size from 8 acres to 49 acres; five separate riparian “selective blue mark” areas totaling 24 acres; and seven right-of-ways (R/W) totaling 10 acres. Douglas-fir was the dominant species in the sale. There were six different minor species of trees in the sale that had to be cruised and appraised, also. BLM policy requires us to achieve a sampling error of 10% or less when t = 2 on all sample cruises. Also, we are required to provide a volume estimate for each administrative unit – on this sale that would be 24 units.

Being the principal Cruiser/Appraiser (C/A) for our Resource Area I did the only responsible thing for me to do. I assigned the sale to our most capable journeyman C/A, Chris Haubrich. We conferred with one another on how to handle this unwieldy looking sale. Due to the variety of different leave tree marking prescriptions employed and the assorted types of cutting units on the sale we settled on using five different cruise methods.

The units were spread out across two townships. We decided the Variable Plot PCMTRE version of the National Cruise Program (NCP) would work best for the thinnings. This version of NCP allows you to randomly select measure trees on your plots instead of doing the traditional count plot/measure plot method. This assured us of getting measure trees spread out amongst all the thinning units. The data collection program we had on our handheld computers did not have a random number selector for the VP portion of the program. Nor, did it allow us to put measure trees into count plots. So, we had to come up with some unique workarounds to avoid some serious keypunching later.

To get around the first problem of selecting sample trees we had two options. The first option required us to set up a dummy 3P sale on a separate handheld to take advantage of its random number generator. We could set the kz just low enough for us to get the desired number of measure trees. We tried this on a previous sale and it worked quite effectively. One of the drawbacks to this is you have to carry two handhelds. That’s okay if you have the luxury of having enough handhelds to go around. The other draw back is who really wants to carry any more weight in the woods than needed. So, we decided to use a method we had heard about at the “Advanced Variable Probability Sampling” workshop we attended the previous year. That of course was the big BAF/little BAF method. This method required no extra equipment because we already use Relaskops to determine in or out trees on plots. All we needed was to pick a BAF large enough but not too large to get us an acceptable number of measure trees. It was decided that on the eight units that were marked to a 25’ to 30’ spacing we would use a 27.78 BAF for basal area measurement and a 184.3 BAF to select our v-bar trees. On the remaining four units that were marked to 20’ to 25’ spacing we used a 20 BAF to measure basal area and a 160 BAF to select the v-bar trees. There were no guarantees the big BAF would pick up any minors so, each cruiser was to select the first “in” minor species they encountered on their plots with both methods. This assured us of a reasonably righteous sample for each minor species.

The next problem dealt with another shortcoming of our data collection program. The program was set up only to deal with count plots or measure plots not measure trees on count plots. The NCP could handle the measure trees spread out amongst the count plots. All we had to do was make sure that the final data set had each measure tree assigned to the correct plot before the data was processed. We decided that each cruiser have a plot number that all their measure trees would be put into. We would then keep notes on which sample number went with which count plot. When we got back to the office we would dump our handhelds on the PC, merge then bridge the data into NCP format and then edit the data to ensure the measure trees were assigned to their corresponding count plot. This required all of about twenty minutes of editing. That took care of the thinning units.

The R/W’s and the riparian blue mark (RBM) areas provided a slightly different challenge. The R/W acres were deducted from the thinning unit acres. In essence they are long skinny clear cuts. We decided that 3P would work best for the Douglas-fir and western hemlock. The grand fir, incense cedar, red cedar, red alder and bigleaf maple were scattered through out all the R/W’s. For simplicity’s sake and the fact that these minors accounted for a little more than 5% of the volume we chose to use the Sample Tree cruise method in NCP. Sample frequencies ranged from a 1 in 1 to a 1 in 10 ratio. The size of the ratio depended on the minor in question and the size of the R/W. We were not too concerned about the sample error as we figured the VP and 3P portion of the cruise would overwhelm them.

The last portion of the sale was the RBM. The Environmental Assessment called for a harvest treatment to occur in some of the riparian areas. Unfortunately, the sale had already been laid out. None of the riparian areas were included inside the posted boundaries. With no good estimate of the acres we were left with few options. Only Douglas-firs were being removed from the RBM area. Trees to be removed were marked in blue paint, of course. This situation lent itself well to a 3P cruise. 3P is not dependent on accurate acres as every tree is visited and estimated. Not wanting to take a chance on missing any trees we both marked and cruised the RBM areas. Being careful not splash too much blue on our handheld while cruising.

Just when we thought we had all our concerns addressed we experienced a bit of a windstorm that blew down about two acres of trees in one of the thinning units. The trees created a logging hazard and required removal. Once more we fell back on a 3P cruise to handle the situation. We traversed the area and subtracted the acres from the thin. We then 3P cruised all the trees that had to be removed. Finally, we were finished with cruising the sale.

Our sampling error for the cruise ranged from 9.2% to 17.87% for each of the five different cruise methods. The combined sampling error was 8.27%. This showed once again how different cruise methods can be combined to achieve the desired answer.

It is hard to say exactly how much time this took. We were involved with this sale from the stand exam stage, to the red tree vole surveys, to the sale layout, to finally the cruise and appraisal. Each stage of the process overlapped in to the other. If I were to hazard a guess on time I would say three of us spent a total of one month in the field doing all the plotting and 3Ping.

More importantly were the lessons we learned from all of this. First and foremost, don’t let the limitations of your computer software dictate the methodology of your cruise. Be creative and find ways to work around those limitations while sticking to your agency or company’s guidelines. Secondly, take the time to work out any problems you might encounter ahead of time. If you have time to do it over you probably had time to do it right the first time. Third, surround yourself with dedicated well-trained people who love working in the woods. If it wasn’t for the imagination and thoughtfulness of every one on the team we would still be out there trying to figure this sale out.

With that I must give credit where credit is due. A big thanks goes out to Chris Haubrich the lead cruiser on this sale and another to Nanci Curtis the ever-resourceful member of our team who made all the little things happen for us.

Originally published January 2004

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