Contents
- Before you begin
- Measuring Oregon ash forest
- Considerations for long-term monitoring
- Analysis/calculations
- Example of plot data from three Oregon ash forests
- Conclusions
- Acknowledgments
- References and resources
- Appendix I. Oregon Department of Forestry plot methodology
- Appendix II. Data to collect after EAB arrives and kills trees
- Appendix III. Field tools list
The emerald ash borer (Agrilus planipennis, EAB) poses a direct threat to Oregon ash (Fraxinus latifolia) forests in Oregon, Washington and California. EAB is now present in the Willamette Valley. EAB will likely kill most of the ash trees in forests and urban plantings in Oregon over the coming decades.
The Oregon Department of Forestry’s EAB Risk Map (figure 1) indicates that Oregon ash is especially common below 1,000 feet of elevation in seasonal wetlands throughout the agricultural areas of the Willamette Valley and along tributaries of the Umpqua and Rogue rivers. Currently, the Oregon Department of Agriculture, the Emerald Ash Borer Task Force and a coalition of partners are attempting to manage EAB with a suite of methods. In the meantime, a Slow-ash-mortality program (see "Slow-ash-mortality"), along with quarantines that prevent the spread of EAB in infested wood material, may give landowners more time to assess their Oregon ash stands.
Landowners can prepare for an EAB mortality event by understanding the location and composition of ash stands on their property and developing site-based restoration plans for implementation after much of the Oregon ash is killed by EAB. This report describes field techniques and summarizes forest measurement data.
Creating a map of your woodlands can help visualize a variety of information, from property lines to vegetation type. A map is also a necessary first step in creating a management plan. OSU Forestry and Natural Resources Extension recommends that landowners consider creating a forest management plan that reflects their objectives for their property. A management plan helps you assess the types of trees and habitats on your property and helps determine whether active management is warranted. Here are two helpful guides for creating a management plan:
You may also contact a professional consulting forester, your local Extension forester, or your local Oregon Department of Forestry stewardship forester, who can assist in developing a management plan. Landowners who have an existing management plan can add Oregon ash stands to their maps.
When making changes to your management plan and forest management decisions, it is critical to know the composition and structure of your forests. Composition describes the various tree species that make up the forest. Forest structure describes the three-dimensional arrangement of live and dead trees and their size and physical attributes.
For example, we might describe a forest like this: An Oregon ash forest had 200 trees per acre, and 75% of the trees were Oregon ash. Trees averaged 14 inches diameter at breast height and 70 feet tall. There were 15 dead trees per acre, and these averaged 10 inches in diameter.
This information provides a sense of the forest structure. Combining forest composition and structure with physical elements of the stand, such as soils, slopes and hydrology, provides even more important information to landowners.
Oregon ash occurs in a diversity of habitat settings, including mixed forests of ash and other hardwoods (alder, cottonwood, maple) in streamside and riverine forests with well-drained soils. It also occurs in pure stands (figure 2) in high clay soils and swales that are seasonal wetlands. Seasonal wetlands are flooded in winter and begin to dry out in summer. Understanding the type of ash habitats you have on your property will help you manage them in the future. For example, management of tree mortality and finding replacement trees is probably easiest in mixed stands, while pure Oregon ash stands may be much more difficult to manage as a forest after EAB kills the trees.
Landowners can gain a better understanding of the forest structure and composition of their ash stands by measuring some plots. A monitoring plot protocol developed for EAB in the eastern U.S. summarizes field methods for monitoring the impacts of EAB on ash forests. This user-friendly protocol has been field-tested in three locations in the Willamette Valley and adapted in Western Oregon and Washington. The Oregon Department of Forestry has also adopted this plot technique for more widespread research and monitoring of Oregon ash forests.
The approach involves establishing fixed-area circular plots that include all trees measured and assessed over a specified size (figure 3). It also includes sub-plots to assess natural Oregon ash regeneration and other understory shrubs, herbs and grasses. The protocol suggests using at least three plots in a given forest area to capture variation in species composition and structure. This protocol is intended to enable landowners to assess EAB-induced ash tree decline and subsequent plant community responses, determine EAB population trends, and track remnant ash populations after EAB has killed ash trees in the stand. Remnant ash are defined as non-infested ash trees greater than 4 inches diameter at breast height that occur on a site that has been infested by EAB and where more than 95% of trees have already died.
Plot information includes the following:
- Specific tree species composition (proportion of ash trees in the stand), structure (size classes of trees, dominance by certain tree species) and general health.
- Tree regeneration. What might the future forest look like?
- Tree maturity, crown vigor, seed production and important qualities that can be used to select trees as candidates for chemical protection, value as timber (see "Oregon ash as a timber species") or other management objectives.
- Other site information such as understory vegetation, riparian qualities, soils and hydrology.
The combined information on current trees and other plant species composition and structure can be used to determine the impacts of EAB on the forest stand, and which alternative tree species might be considered for restoration. Although monitoring ash plots may take time, the wealth of information collected will increase understanding of your property and better inform management decisions.
Before you begin
It is critical to know the trees species on your woodland. There are many resources that can help you. We recommend OSU Extension publications, including the field guide Trees to Know in Oregon and Washington (EC 1450) by Edward C. Jensen
Before you decide whether to establish plots, consider a walk-through of your property to observe where Oregon ash occurs. Familiarize yourself with stand conditions (estimated age, average size, density, relative health), landscape setting (topography, slope, stream channels) and stand boundaries. This will give you a sense of whether you have a single stand, whether there are multiple different ash stands of different ages, or whether you have a mixed-species stand of multiple large-canopy trees.
Then, decide if you want a more quantitative assessment of tree species composition and size. Do you want to monitor the invasions of EAB into your stand? These plots are an effective way to document changes to your forest as EAB arrives. Monitoring your plots involves revisiting each tree and assessing growth, decline and mortality. Revisit the plot every five years — this allows for enough tree growth to be measurably different. However, revisiting the stand annually to determine if trees are dying is also an option.
Measuring Oregon ash forest
Forest measurement, or mensuration, is the assessment of the composition, structure and pattern of forest trees as well as the volume of potential lumber. In forestry, the assessment of forest trees is often called forest inventory. There are several ways to approach forest measurement based on forest type and a landowner’s objectives. A forest stand is a contiguous group of trees that are generally similar in composition, age and size distributions, and site conditions.
The techniques and tools of forest measurement are nicely described in two publications, which we suggest reviewing to complement this report:
- Basic forest inventory techniques for family forest owners, PNW 630
- Tools for measuring your forest, EC 1129
There are many ways to inventory a forest, and fixed-area circular plots are one of the easiest and most common. A typical fixed-area circular plot has a plot center, a plot boundary, and a plot radius (figure 3). The easiest way to establish these plots is to locate a plot center and mark it with a stake. We used a white, 4-foot-long, 1-inch-diameter PVC pipe. Determine the plot boundary by running a measuring tape from plot center to the edge of the plot in a circle around the plot center. Hang some flagging to mark the boundary. Keep the measuring tape horizontal as you mark the edge of the plot. Once the plot is established, measure all the trees within the plot that are 4 inches in diameter or greater. The diameter of a tree is measured at 4.5 feet above ground level — this number is referred to as diameter at breast height, or DBH.
One issue that often comes up is choosing “in” and “out” trees at the border of the plot. Trees that have more than half of their ground-level diameter in the plot are considered “in” and would be measured (figure 4). In other words, the center of the tree, as nearly as can be established, falls within the circle.
We recommend sampling during late spring and summer because trees have leaves on and it is easier to determine tree health and decline. In fall, Oregon ash often loses its leaves early in the season, and crown decline can be difficult to assess. Spring and early summer is the best time of year to identify the understory plants. Many herbs die back in summer after the soils dry out.
Location and number of plots
How many plots, and where do you place them in the stand? The answers can be quite nuanced. In general, we recommend a minimum of three plots per stand of ash if you want to get an average picture of stand density (tree abundance), composition and size of trees. Plot locations can be randomly assigned, but this approach is problematic (see Basic forest inventory techniques for family forest owners, PNW 630). In general, it is easiest to place plots deliberately haphazardly spread out over the site, far enough apart to capture some of the variation and away from exposed stand edges. Once you’ve located the plot, place a post in the ground at plot center and record a GPS point.
Sampling within plot area
Each plot consists of a large plot for tree monitoring, a smaller subplot for saplings and microplots to measure seedlings and vegetation (figure 5).
Sequence for plot establishment (easiest with two people):
- Step 1: Establish plot center with a 3- to 4-foot wooden stake or a length of PVC pipe or rebar.
- Step 2: Flag the boundaries of the 1/10-acre (37.2-foot radius) plot around your plot center. Lay a tape on the ground across the diameter of the plot to help visualize tit.
- Step 3: Begin with the north aspect and tag tree No. 1.
- Step 4: Sweep clockwise and give a new number to each tree, measure its diameter, and take the other data. If you have two people, one person can stand in the center of the plot, record data on the data sheet, and guide the other person in numbering trees.
- Step 5: Take a regeneration estimate for the 1/20-acre (26.3-foot radius) subplot by sweeping around the plot and counting saplings.
- Step 6: Review the data sheets in the field at the plot before leaving the plot. Check for missing data in the columns and rows.
- Optional: if you plan to collect data for the seedling/vegetation microplots, complete the microplot data collection after Step 2 before tagging trees and taking data for the main plot. These are smaller 5.3-foot radius plots that are located 20 feet from plot center in the cardinal directions: north, east, south and west. Recording microplot data prior to the main plot data will provide a more accurate record of seedlings and herbaceous plants before they are trampled.
Tree measurement: 1/10-acre main plot
Each circular large main plot has an area of 1/10 of an acre (37.2-foot radius) for monitoring ash trees greater than or equal to 4 inches DBH. Measure all tree species within the main plot rather than just focusing on Oregon ash. Begin with the north aspect and scan clockwise through the plot. Tag the first tree as No. 1. Depending on your preference, you can either number all subsequent trees with a tree tag or wrap them with durable flagging. Each tree is numbered in the datasheet, however. All trees greater than or equal to 4 inches are measured with a specialized diameter tape (See Tools for measuring your forest, EC 1129). Table 1 lists all the data recommended for collecting.
|
Column heading |
Description |
Example |
|---|---|---|
| Plot | A different plot number is assigned to each plot. | 1, 2 or 3 |
| Tree | Each tree is assigned a unique number | 1, ... 100 (unique number) |
| Species | Scientific or common name or code | Oregon ash, Fraxinus latifolia, or FRLA |
| DBH = Diameter at breast height in inches | The diameter of the tree at 4.5 feet height above ground. Easiest to use a standard diameter tape. | 10.4 (specific number with one decimal point) |
| Dead (Y/N) | Indicate whether tree is dead. If the tree has green leaves, it is considered alive. |
Y = tree is dead, that is, it is a snag N = tree has green leaves, is alive |
| Crown class |
The relationship of an individual tree crown to the rest of the forest canopy. Dominant: Above general canopy of stand; receives direct sunlight on top and all sides. Co-dominant: Average position in stand; receives direct sunlight on top and at least one side. Intermediate: Below general canopy; receives direct sunlight on top. Suppressed: Completely overtopped; receives no direct sunlight. |
1 = dominant 2 = co-dominant 3 = intermediate 4 = suppressed |
| Crown ratio | Percentage of trunk length with live crown | 35% (exact number, often rounded to the nearest “5.” For example, 70, 75 or 80) |
| Ash condition | For live Oregon ash greater than or equal to 4 inches only. The ash canopy condition rating scale is used to quantify degree of decline and dieback of ash trees. In dense stands, the lower crown branches may decline from shading. EAB often kills the tree from the top down. |
1 = Canopy is full and healthy 2 = Canopy has started to lose leaves (thinning), but no dieback (dead top canopy twigs without leaves) present 3 = Canopy has less than 50% dieback 4 = Canopy has more than 50% dieback 5 = Canopy has no leaves; epicormic sprouts may be present on the trunk |
| Sex (M/F) | Ash trees are either male or female. Female will have seed hanging from the ends of branches. However, this can be difficult to see and determine. Note trees that have an obvious seed crop; they are definitely female. A good seed tree is important for regeneration. |
M = male F = female |
| EAB exit holes (Y/N) | EAB adults create a small D-shaped exit hole in the bark approximately 1/8-inch wide as they exit the tree (figures 6 and 7). |
Y = yes N = no |
| Woodpecker activity (Y/N) | Woodpeckers will flake the bark in search of EAB larvae. This activity commonly penetrates to the bark-wood interface, but sometimes the pecking can penetrate the outer layers of wood (figure 8). |
Y = yes N = no |
| Epicormic sprouts (Y/N) | An epicormic sprout is a secondary branch that forms from latent buds along the trunk or branches of a tree. |
Y = yes N = no |
| Basal sprouts (Y/N) | Basal sprouts are a type of epicormic sprout that occurs below DBH on the lower trunk of the tree (figure 9). |
Y = yes N = no |
| Bark splits (Y/N) | Bark splits caused by EAB are linear openings in the bark that expose the wood below the bark. The bark may have a raised appearance. Bark splits on branches are oriented in the direction of the branch growth. Bark splits on the trunk are oriented vertically (figures 10 and 11). |
Y = yes N = no |
| Tree notes | Record details about important or unique features of the tree. Is wildlife using this tree? Do the height or form of the tree indicate its potential value for lumber? |
Regeneration measurement: 1/20-acre subplot
Tree regeneration are the small saplings that have established in the understory but are larger than seedlings. All saplings are taller than 4.5 feet and less than 4 inches DBH. They are measured within a nested subplot centered in the plot (1/20-acre, 26.3-foot radius from plot center) (figure 3).
Saplings and shrubs of other species may also be counted within the subplot. The subplot is similar to the size of the Forest Inventory and Analysis subplot and can generate data that use FIA methods for determining canopy cover. Canopy cover is an estimate of the percentage of the plot covered by the foliage and crowns of a particular species of plant. Table 2 describes the data we recommend collecting.
|
Column heading |
Description |
Example |
|---|---|---|
| Plot | The plot number assigned to the main plot. | 1, 2 or 3 |
| Tree species | Count all tree species occurring in subplot taller than 4.5 ft and less than 4 inches DBH. List each species found in the subplot. | Oregon ash, Fraxinus latifolia, or FRLA |
| # | Number of individuals of that species and size range in the subplot | 15 (total number) |
Seedlings and understory vegetation measurement: Four 1/500-acre microplots
Surveillance of ash seedlings less than 4.5 feet tall is accomplished with four microplots (1/500-acre plot, 5.3-ft radius) placed 20 feet from plot center in each cardinal direction: north, east, south and west (figure 5). Identify and count seedlings of all tree species and characterize understory vegetation. However, if you want to sample understory, do so in late spring or early summer to capture all the plants. Seedlings can be counted at any time but are easiest to identify when leaves are present in spring and summer. Table 3 describes the data we recommend collecting.
|
Column heading |
Description |
Example |
|---|---|---|
| Plot | # of the main plot | 1, 2 or 3 |
| Microplot | # of microplot | 1, 2, 3 or 4 |
| Seedling species | A seedling is any tree less than 4.5 ft tall. List all the species present of that size. | Oregon oak, Quercus garryana, or QUGA |
| Number of individual seedlings | Number of individuals of that species and size in the microplot | 13 (a specific number) |
| Vegetation species/group |
You can identify ALL vascular plants to species, or categorize understory vegetation: shrubs, herbs, grasses or bare ground. Shrub = woody, perennial plant. Herb = nonwoody plants that die down to the ground after flowering. Grasses = herbaceous plants with grass-like leaves (includes grasses, sedges and rushes). Pay special attention to specific rare plants or invasive weeds. The columns of the data sheets can reflect landowner preferences. |
Common or scientific names |
| Percentage of vegetation cover | Estimate % COVER within the microplot. Looking from above, what is the % of the area of the microplot that is occupied by an individual species? This can add up to over 100% because of overlap of individual species. | 45 (specific number) |
Considerations for long-term monitoring
If you plan to re-measure plots on a long-term basis, there are a few things to consider that will make tree remeasurement more accurate, especially if you want to know how fast trees are growing. One course of action is to tag every tree with an aluminum nail and numbered tag. Aluminum nails are recommended because they don’t harm a chain saw and are better for tree health. The DBH measurement is then taken at the nail, in the same spot each time data are collected. However, if the tree is not tagged, it is difficult to re-measure diameter at the same location each time. A less permanent option is to use tree paint and put a dot at DBH height and use that as a marker for remeasurement. Marking plot center with a sturdy material like rebar or PVC is also useful, including hanging flagging at and through the forest to plot center. Flagging is not a good way to mark trees, however. Revisiting plots will also be easier if you have them located on a mapping app on your phone so you can walk right to them.
Analysis/calculations
Main plot
The approximate number of trees (4+ inches in diameter) per acre in each forest was calculated by first adding all three main plot totals together (total amount in tables 2, 4 and 6). Each main plot is 1/10 of an acre. With the three plot values merged, the total amount is equal to the total number of trees in 3/10 of an acre. The combined three main plot tree totals were then divided by three and rounded to the nearest whole number to approximate the average total number of trees per 1/10 of an acre. To convert to trees/acre, multiply by 10. To get an average number, you need three or more plots.
- Average # of trees per plot = (total # of trees on all three plots)/(# of plots)
- Trees per acre = (average # trees per plot) x 10
For example, to determine trees per acre:
- The total amount of Oregon ash in three 1/10-acre plots was 100 (data from table 2).
- 100/3 = 33.3 trees per 1/10-acre plot on average
- 33.3 trees per plot x 10 = 333 trees per acre
- This forest stand has approximately 333 trees greater than or equal to 4 inches DBH per acre.
Subplot
The approximate number of saplings (saplings are taller than 4.5 feet and less than 4 inches DBH) per acre was calculated by first adding all three subplot totals together (total amount in tables 3, 5 and 7). Each subplot is approximately equivalent to 1/20 of an acre. With the three plot values merged, the total amount is equal to the total number of saplings in 3/20 of an acre. Combined main plot sapling totals were then divided by three and rounded to the nearest whole number to approximate the average number of saplings in 1/20 of an acre. To convert to trees per acre, multiply by 20.
- Average # of regeneration per plot = (total # of individuals on all three plots)/(# of plots)
- Tree regeneration per acre = (average # tree per plot) x 20
For example, to determine regeneration per acre:
The total amount of Oregon ash in three 1/20-acre plots was 33 (data from table 3).
- 33/3 = 11 trees per 1/20-acre plot on average
- 11 trees per plot x 20 = 220 trees per acre
This forest stand has approximately 220 Oregon ash saplings per acre.
Example of plot data from three Oregon ash forests
The plot design for Oregon ash forest vegetation measurement was tested on three separate ash forests in Oregon. Two of the plots (Forest A, Forest B) were privately owned land while the third (Forest C) was public. Forest A is southwest of Forest Grove, Oregon. Forest B is south of Albany, Oregon. Forest C is west of Corvallis, Oregon. Data about understory vegetation for the microplots were not recorded in these three forests because the herbs had died back by the date of collection time in August. Microplot data is best recorded in spring, when it’s easier to identify vegetation. Two people worked together to measure these plots.
After plot locations were selected and numbered (1–3), the team marked plot centers by pounding a 4-foot white PVC pipe partially into the ground. The latitude and longitude of the plot centers were measured using a GPS device. (Position the device for two minutes for a more reliable reading.) They recorded the data on the field data sheets. They used a measuring tape to find the radius of each plot, with one end tied or held over plot center and the other moved in a circle to determine the plot boundaries. Flagging was spread about 8 feet apart around the circumference of each plot. Landowners may choose to place more flags.
The team then worked together to assign numbers to and collect data on the trees. One person stood at plot center to record data on field data sheets (figures 5, 6 and 7) and determine crown class, ash condition and crown ratio. The other person went from tree to tree calling out information on tree number, DBH, EAB holes, bark splits and so on. Any extra observations about snag heights, bole damage, and so on, can be recorded in the “tree notes” section of the main plot field data sheet. Once all of the main plot data were recorded, we moved on to the smaller subplot and repeated the process of measuring and flagging the boundary. Below are tables, charts and figures summarizing the results of the monitoring plots on Forests A, B and C.
Forest A
Three plots were positioned in Oregon ash stands within the mosaic wetland, conifer and hardwood forest habitat of Forest A (figures 12, 13). No trees were found to have EAB exit holes, and none was suspected to be infested with EAB. Data collected in the main plots showed that there were 389 trees per acre (greater than 4 inches in diameter) averaged across all three plots. Oregon ash comprised 86% of the trees in Forest A, while the next most abundant species were cascara (Frangula purshiana) at 4%, followed by Douglas-fir (Pseudotsuga menziesii) at 3%. The plot with the highest concentration of Oregon ash was A1 at 93%, whereas plot A3 had the lowest proportion of Oregon ash at 60%. Plot A3 contained the highest level of tree diversity with six different tree species, compared to four species in plot A2 and two species in plot A1 (table 4).
Forest A subplots contained an average of 321 saplings (less than 4 inches in diameter and taller than 4.5 feet) per acre. Four species of saplings were found within subplots, with 67% of them being Oregon ash. The next most abundant species in Forest A subplots was western crabapple (Malus fusca), accounting for 21% of all saplings recorded (table 5). Oregon ash greater than 4 inches in diameter were grouped into three diameter size classes (4–10 inches, 10.1–15 inches and 15.1–20 inches). The 4–10-inch-diameter class contained most of the trees, about five times more trees than in the 10.1–15-inch class. Very few trees were assigned to the 15.1–20 inch and greater diameter class (figure 14).
Conclusions about Forest A: The forest is currently 86% ash. When EAB kills nearly all the ash trees (greater than or equal to 4 inches DBH), few other tree species will be present. But there was a diversity of options based on trees at these sites. Cascara and crabapple are not commercial tree species but are important to wildlife. The landowner may want to consider harvest and hazard tree management in anticipation of this mortality event. Douglas-fir, cascara, crabapple, grand fir, Oregon white oak, white alder and bigleaf maple can likely grow in this area, depending on wetness of the specific site. Consider management activities that enhance the number and vigor of non-ash species that can maintain forest cover and ecological benefits.
|
Species |
Amount |
Amount # trees/acre |
Average Forest A composition (%) |
A1 composition (%) |
A2 composition (%) |
A3 composition (%) |
|---|---|---|---|---|---|---|
|
Oregon ash |
100 | 333 | 85.47 | 93.22 | 90.91 | 60 |
|
Douglas-fir |
4 | 13 | 3.41 | 6.78 | 0 | 0 |
|
Cascara |
5 | 17 | 4.27 | 0 | 3.03 | 16 |
|
Bigleaf maple |
1 | 3 | 0.85 | 0 | 3.03 | 0 |
|
Black hawthorn |
3 | 10 | 2.56 | 0 | 3.03 | 8 |
|
Oregon white oak |
1 | 3 | 0.85 | 0 | 0 | 4 |
|
Unknown |
1 | 3 | 0.85 | 0 | 0 | 4 |
|
Western crabapple |
2 | 7 | 1.71 | 0 | 0 | 8 |
|
Total |
117 | 389 | ||||
|
Species |
Amount |
Saplings per acre |
|---|---|---|
|
Oregon ash |
33 | 220 |
|
Grand fir |
1 | 7 |
|
Indian plum |
4 | 27 |
|
Western crabapple |
10 | 67 |
|
Total |
48 | 321 |
Forest B
Forest B was composed almost entirely of Oregon ash with Oregon white oak (Quercus garryana) scattered throughout (figures 15, 16). No trees were found to have EAB exit holes, and none was suspected to be infested with EAB. The main plots captured a total of 120 trees, all of which were Oregon ash. The average number of Oregon ash per acre in the three Forest B plots was 400, the highest of the three forests (table 6).
Forest B subplots contained an average of 74 saplings per acre. Out of the 11 total saplings captured by the three subplots, six were cascara, four were Oregon ash and one was a species of Prunus or plum (table 7). Oregon ash greater than 4 inches in diameter were grouped into three diameter size classes (4–10 inches, 10.1–15 inches and 15.1–20 inches). The 4–10-inch-diameter class had about three times the amount of Oregon ash as the 10.1–15-inch-diameter class. The 15.1–20-inch-diameter class had very few trees (figure 17).
Conclusions about Forest B: All the trees present in this forest are Oregon ash. When EAB kills them, there will be some young cascara and Prunus species survivors. The landowner may want to consider management activities to salvage value from the ash forest, protect some individual trees and regenerate with other desired tree species. There is no evidence of conifers tolerating these site conditions. However, Oregon white oak is scattered and the site could transition to an oak prairie.
|
Species |
Amount |
# trees/acre |
Average composition (%) |
|---|---|---|---|
|
Oregon ash |
120 | 400 | 100 |
|
Total |
120 | ||
|
Species |
Amount |
Saplings per acre |
|---|---|---|
|
Oregon ash |
4 | 27 |
|
Cascara |
6 | 40 |
|
Prunus sp. |
1 | 7 |
|
Total |
11 | 74 |
Forest C
These three plots were located in the ash dominant stand of Forest C, which also contained black hawthorn (Crataegus douglasii) and Indian plum (Oemleria cerasiformis) (figure 18). No trees were found to have EAB exit holes, and none was suspected to be infested with EAB. Main plot data show that Forest C was the least dense, with the average number of trees (greater than 4 inches in diameter) per acre for the three plots being 246. One black hawthorn was recorded in the C1 main plot, while Oregon ash accounted for the other 99% of the trees (table 8). Himalayan blackberry (Rubus armeniacus) was a common weed across the site.
Forest C subplots contained an average of 254 saplings (less than 4 inches in diameter and taller than 4.5 feet) per acre. Out of the six species of saplings found, Indian plum comprised 68%, followed by English hawthorn (Crataegus monogyna) at 19%. An average of only 5% of saplings recorded were Oregon ash at 13 saplings per acre (table 9).
Oregon ash greater than 4 inches in diameter were grouped into three diameter size classes (4–10-inch, 10.1–15-inch and 15.1–20 inch). Forest C had the most evenly distributed diameter classes. The 4–10-inch class had nearly double the amount of trees per acre as the 10.1–15-inch-diameter class. The 15.1–20-inch-diameter class had about half as many trees as the 10.1–15-inch-diameter class (figure 19).
Conclusions about Forest C: This site is dominated by Oregon ash, which made up 99% of the trees. When EAB kills nearly all the ash trees, the forest will be sparsely populated with white alder (observed, but not present in plots), Indian plum and English hawthorn. This will severely influence the quality of shade for the perennial streams. The Himalayan blackberry on the site may expand when the overstory is removed. Consider other tree species options such as white alder along the stream, and Oregon white oak and bigleaf maple on more upland sites.
|
Species |
Amount |
# trees/acre |
Average composition (%) |
C1 composition (%) |
C2 composition (%) |
C3 composition (%) |
|---|---|---|---|---|---|---|
|
Oregon ash |
73 | 243 | 98.65 | 98.63 | 100 | 100 |
|
Back hawthorn |
1 | 3 | 1.35 | 1.37 | 0 | 0 |
|
Total |
74 | 246 | ||||
|
Species |
Amount |
Saplings per acre |
|---|---|---|
|
Oregon ash |
2 | 13 |
|
Indian plum |
26 | 173 |
|
Cascara |
1 | 7 |
|
English hawthorn |
7 | 47 |
|
Black hawthorn |
1 | 7 |
|
Crabapple |
1 | 7 |
|
Total |
38 | 254 |
Conclusions
The emerald ash borer is a recent and growing threat to ash trees across Oregon and the Pacific Northwest. This manual is useful to landowners who seek to assess the status of ash trees before, during and after the arrival of EAB. Using fixed-area plots to quantify Oregon ash forest composition and structure and to monitor the effects of EAB on your forest may be a good approach. General data gleaned from these plots include tree species, tree size, tree abundance, regenerating species and understory vegetation. This approach provides a good foundation for understanding how the loss of Oregon ash will influence your forest. It also creates the opportunity to think about how your management activities can influence the forest conditions on the site into the future.
Acknowledgments
Financial support for this project was provided by USDA Forest Service Forest Health Protection and OSU Forestry and Natural Resources Extension. Special thanks to Corvallis Parks and Recreation, Don Wirth and family, Peter and Pam Hayes and the Oregon Department of Forestry.
References and resources
Belart, F., and L. Grand. 2019. Tools for measuring your forest. EC 1129, Corvallis, OR: Oregon State University Extension Service.
Jensen, E.C. 2020. Trees to Know in Oregon and Washington. EC 1450, Corvallis, OR: Oregon State University Extension Service.
Knight, K.S., B.P. Flash, R.H. Kappleer, J.A. Throckmorton, B. Grafton and C.E. Flower. 2014. Monitoring ash (Fraxinus spp.) decline and emerald ash borer (Agrilus planipennis) symptoms in infested areas. General Technical Report NRS-139, Newton Square, PA: U.S. Forest Service, Northern Research Station.
Kral, G., and D.C. Shaw. 2023. Alternatives to ash in Western Oregon: With a critical tree under threat, these options can help fill habitat niche. EM 9396, Corvallis, OR: Oregon State University Extension Service.
McCullough, D.G., N.W. Siegert and J. Bedford. 2009. Slowing ash mortality: A potential strategy to SLAM emerald ash borer in outlier sites. Newton Square, PA: U.S. Forest Service, Northern Research Station.
Owston, P.W. 2009. Oregon Ash, Fraxinus latifolia Benth. In; R.M. Burns and B.H. Honkala (technical coordinators), Silvics of North America: Volume 2. Hardwoods. Miscellaneous Publication, Agricultural Handbook 654. U.S. Forest Service, Southern Research Station.
U.S. Forest Service. 2011. Forest Inventory and Analysis National Core Field Guide Volume I: Field Data Collection Procedures for Phase 2 Plots, Version 5.0. Washington, DC: U.S. Department of Agriculture, Forest Service, Forest Inventory and Analysis.
Zobrist, K.W., D.P. Hanley, A.T. Grotta and C. Schnepf. 2012. Basic forest inventory techniques for family forest owners. PNW 630, Pacific Northwest Extension.
Additional OSU Extension resources
OSU Extension Emerald Ash Borer resource collection
Shaw, D.C., J.W. Pscheidt and A. Gorman. 2023. Oregon ash: Insects, pathogens and tree health. EM 9380, Corvallis, OR: Oregon State University Extension Service.
Gorman, A., C. Hedstrom, K. Ripley, W. Williams, C. Buhl, S. Altenhoff, C. Benemann, J. Gersback, M. Ragozzino, C. Holthouse and A. Ambourn. 2022. What to do about emerald ash borer: Recommendations for tree protection in EAB-infested areas. Corvallis, OR: Oregon State University Extension Service.
Shaw, D.C. 2022. Recognizing ash trees in Oregon, Washington and Northern California. Corvallis, OR: Oregon State University Extension Service.
Saffell, B. and A. Grotta. 2017. Oregon Forest Pest Detector pest watch — emerald ash borer (published in English and Spanish). EM 9160, Corvallis, OR: Oregon State University Extension Service.
B. Saffell and A. Grotta. 2016. Oregon Forest Pest Detector field guide. EM 9127, Corvallis, OR: Oregon State University Extension Service.
D.C. Shaw, A. Grotta, W. Williams, R. Rippy and S. Bowers. 2016. The hidden threat in firewood: Invasive forest pests. EM 9137, Corvallis, OR: Oregon State University Extension Service.
Appendix I. Oregon Department of Forestry plot methodology
The Oregon Department of Forestry is establishing monitoring plots in Oregon ash forests as part of its long-term monitoring of Oregon ash forests in the face of EAB. Their technique uses the 1/10-acre tree plot methods above but does not include regeneration or seedling plots. ODF is locating the sites where little to no management will occur, so that the state can document the changes to forest structure and composition over time by measuring forest structure before, during and after the infestation to document mortality and stand recovery.
Appendix II. Data to collect after EAB arrives and kills trees
Dead from EAB since establishment of the plot.
Snag breakup
Breakup categories used for dead ash trees and rating description
- A: All branches have fine twigs
- B: More than 50% of branches have fine twigs
- C: Less than or equal to 50% of branches have fine twigs
- D: No fine twigs; tertiary branches present
- E: Main stem and possibly primary or secondary branches present
Fallen tree
Fallen tree categories used in ash monitoring plots and code description
- L: Ash leaning
- U: Ash uprooted
- SH: Ash snapped high, above DBH
- SL: Ash snapped low, below DBH
- F: Non-ash tree has fallen on it
- AF: Ash tree has fallen on it
Tree notes
As 95% of the ash trees have died, do any individual trees appear to be surviving?
Appendix III. Field tools list
- Cellphone and/or GPS unit. Several location apps are available for cellphones.
- Data sheets, clipboard, pencils
- Compass
- Field vest
- DBH tape (diameter equivalents of inches)
- 50-foot measuring tape
- Flagging
- Center-point marker (PVC pipe, wooden stake or metal rebar post)
- Sharpie for writing on flagging and backup
- Tags: Affix with a hammer and nails or use a staple gun with a zip tie for tags
About the authors
