WVA Tree Mapping

WVA Tree Mapping Plots

Refuge staff and a talented volunteer, Dexter D., initiated and completed an inventory of trees in the Wildlife Viewing Area during 2013/14. Objective of this work: gather baseline data (as directed by the CCP) on the trees (species, size, location, recruitment) in the WVA employing GIS equipment/software and 38 sample plots. Report embedded below.


Field ProcedureTrees .1-1.9" in diameter
Trees 6"+ in diameterTrees < 5 feet tall 
Trees 2-5.9" in diameter              

 

Field Procedure

WVA Tree Mapping Plot-Ponderosa PineThe sampling area of the Wildlife Viewing Area was defined by the property lines on the north and south, Wildfowl Lane or the slough on the east, and the Bitterroot River on the west. A systematic grid was used for planning the inventory plots. A total of 38 plots were sampled. Plot 5 was the only plot east of the slough. Plot spacing was 400 feet and spaced in the cardinal directions of N, E, S, and W. Plots were located using a handheld Garmin GPS, based on the distance and direction from the previous plot. The distance to some plots on the edge of the viewing area was shortened, so the plot would fall inside the sample area. Plot spacing was not less than 300 feet. Plot center was designated with orange flagging tied around a small plant or grass. No permanent plot was established. The sample trees were not designated in any way. The data from four random precruise plots, with 500 feet spacing, was incorporated into the main inventory data.

 

WVA Tree Mapping Plot-WillowCircular fixed area plots were used. A 1/10th acre plot (37.24 ft. radius) was used for the dominate tree species. Borderline trees were measured to the face of the tree, instead of to the center. Any tree over 5 feet tall was sampled in this plot. Total height and diameter at breast height were recorded for each tree. Any visible defect, such as broken tops or decay, were noted. Several trees were bored to determine age and growth rate. Success was very limited due to the tree core getting stuck inside the increment borer bit. Sampling willows, also, proved to be difficult. One main willow stem may have been horizontal, but had several vertical leaders. This was measured as one willow. If the main stem of a black cottonwood was broken out, the height to the tallest leader was measured.

A smaller 1/100th acre subplot (11.78 ft. radius) was used to tally woody stems less than 5 feet tall. Grasses and forbs were not sampled. The identification of many small shrubs was questionable, due to lack of knowledge of local plants by the sampler. 

Data Analysis

After the field data was collected, it was input into an Excel Spreadsheet. Each tree species, (black cottonwood, Ponderosa pine, and willow) were also separated onto a specific worksheet.

All trees over 6 inches diameter 

A total of 38 plots or 3.8 acres were sampled. Ponderosa pine, in this size class, was tallied on 15 plots (39%), with the majority of the plots being in the north half of the viewing area. The average density of Ponderosa pine for the whole viewing area is 12 trees per acre, while the average density when only considering plots with Ponderosa pine is 30 Ponderosa pine trees per acre. The average Ponderosa pine, based on 45 measurements, is 16 inches in diameter and 65 feet tall. The largest Ponderosa pine measured was 39 inches in diameter and the tallest was 110 feet tall.

Black cottonwood, in this size class, was tallied on 22 plots (58%). Average density of black cottonwood for all plots is 38 trees per acre. Average density for black cottonwood, when only considering plots containing black cottonwood, is 66 trees per acre. Based on 144 measurements, the average black cottonwood tree is 14 inches in diameter and 65 feet tall. The largest measured diameter is 33 inches and the tallest is 124 feet. Since black cottonwood has no defined top, height measurements may have lower accuracy.

Willow, in this size class, was tallied on 2 plots (5%). All willow species were tallied as willow. It is not known if more than one species of willow occurs in the wildlife viewing area. Average density of willow, in this size class, for the viewing area is 2 trees per acre or 45 trees per acre when only considering plots containing willow. The largest willow measured was 13 inches in diameter and the tallest willow was 50 feet.

One alder tree (best guess of species) over 6 inches in diameter was tallied. It was estimated to be 20 feet tall.

Trees between 2.0” and 5.9” in diameter and taller than 5 feet

Ponderosa pine, between 2.0” and 5.9” diameter, occurred on 8 plots (21%). Average tree density for the wildlife viewing area is 10 trees per acre, or 50 TPA when only considering plots with this Ponderosa pine size class. Average diameter in this size class is 3.9 inches and 19 feet tall. 

Black cottonwood, between 2.0” and 5.9” diameter, occurred on 7 plots (18%). Average tree density of this size class for the wildlife viewing area is 8 trees per acre or 41 TPA when only considering plots with this cottonwood size class. Average diameter in this size class is 4.2 inches and 22 feet tall.

Willow, between 2.0” and 5.9” diameter, occurred on 2 plots (5%). Average tree density is 1 tree per acre for the wildlife viewing area or 20 TPA for plots containing willow. 

Trees between 0.1” and 1.9” in diameter and taller than 5 feet

Ponderosa pine, in this size class, occurred on 10 plots (26%). Average tree density within the wildlife viewing area is 23 trees per acre or 87 TPA when only considering plots containing this size class.

Black cottonwood in this size class, also, occurred on 10 plots (26).Average tree density within the viewing area is 23 trees per acre or 88 TPA when only considering plots containing this size class.

Willow in this size class occurred on 7 plots (18%). Average tree density within the viewing area is 160 trees per acre or 871TPA when only considering plots containing this size class. The actual count of willow is questionable. In most cases, the main stem had several leaders of similar diameter. When it was easily determined, the main stem with several leaders was counted as only one willow.

Hawthorn in this size class occurred on 3 plots (8%).Average tree density is 4 trees per acre or 50 TPA on plots containing hawthorn. Largest diameter tree measured was 2.5 in. and an estimated 20 feet tall.

Other species, possibly serviceberry and chokecherry were also present on the plots. An accurate identification was not made due to lack of knowledge.

Trees less than 5 feet tall

Ponderosa pine regeneration occurred on 10 plots (26%). Average tree density, in this size class, for plots with ponderosa pine regeneration, was 1070 trees per acre. Average height was 2 feet.

Black cottonwood regeneration occurred on 15 plots (39%). Average tree density, in this size class, for plots with black cottonwood regeneration was 886 trees per acre. Average height was 2 feet. Some black cottonwood regeneration was very short and had several leaders, possibly due to deer browsing. These were tallied as one tree.

Willow regeneration was tallied on 2 plots (5%). Six trees were tallied for an average tree density of 300 trees per acre. Willow was not sampled on subplots located in willow thickets.

Juniper regeneration was tallied on one plot. The tree was 4 feet tall.