Plant biomass dynamics following logging, burning, and thinning in Watersheds 6 and 7, Andrews Experimental Forest, 1979 to present

ORIGINATOR: Kari B. O'Connell
OTHER RESEARCHER: Robert J. Pabst, Frederick J. Swanson, James H. Mayo
ABSTRACTOR: Kari B. O'Connell
3 Jun 2005
4 Mar 2013
Organic matter, Primary production, biomass, community composition, species composition, plant species composition, primary production, thinning, organic matter, forests, understory vegetation
To characterize plant succession after thinning in a small, high-elevation watershed.
Field Methods - TP114:

Protocol for Coring Trees in WS6 & 7, Summer 2002

Tree cores will be taken of all tagged trees in the north ½ of each upland plot and the ½ of each riparian plot in the direction AWAY from the gauging station.

Measure DBH of each tree to the nearest 0.1 cm. One increment core will be taken at DBH for each tree. We will be using the cores to estimate tree ages, so trees should be cored to the pith. On the datasheet, mark down tree core position (uphill, sidehill, downhill) in the 'position' column. Mark 'flat' in the position column when it is too flat to figure out obvious tree core position. On each increment core, measure bark thickness and sapwood thickness with calipers to the nearest 0.1 cm.

All cores will be saved for mounting and inspection in the lab. Cores should be placed in straws labeled with watershed #, plot number, and tree tag number. Staple each straw on both ends so tree core will not fall out.

WS6 and 7 Tree Measurement Procedures Version: June 8, 2002


Use the data form "Watershed 6 and 7 Tagged Tree Measurement." Compete all information in the header. Each tree = 5 cm in the plot should be tagged at DBH with the tag facing the center of the plot. Begin tagging trees at the north side of the plot, and go clockwise around the plot in an orderly fashion to tag the rest of the trees. If tagging trees on a steep slope, always determine the correct height for DBH from the uphill side of the tree. Also, if a tree is forked below DBH, treat each stem as a separate tree. If a tree is forked above DBH, treat the tree as one tree.

1. For live trees tagged at breast height record:

DBA approx. 28 cm above the ground in the DBA column for stumps with DBA > 5 cm. See below for specific information about minimum diameters of stumps. If the stump cannot be measured at 28 cm, take at the closest point and mark in the comments where the measurement was taken. DBH in the DBH column, to the nearest tenth of a centimeter. Canopy class in the CC column: D (dominant, i.e. crown rises slightly above the general canopy layer), C (co-dominant, i.e. crown extends to the top of the canopy layer), I (intermediate, i.e. crown extends into the lower portion of the general canopy layer) and S (suppressed, i.e. crown completely beneath the general canopy layer). Overall vigor of the tree in the OV column as: "1" = good, "2" = fair (some loss of foliage, branches, or crown), or "3" = poor (few needles or live branches, almost dead), Crown ratio to nearest 10% in the CR column. Crown ratio is defined as the proportion of the bole over which live branches cover at least 1/3 of the bole's circumference. Status in the Stat column as "1", meaning present and alive or "3" for stumps.

2. For trees that have been cut:

Stumps that are rooted in the plot and are a result of the 2001 thinning will be measured approx. 28 cm above the ground with small diameter tapes or calipers.

For each stump record: DBA in the DBA column, to the nearest tenth of a centimeter, species in the species column if possible to identify, status in the ST column as "3", meaning stump.



Surface cover types and growth forms. Cover of each type in the 2 x 2 m plot. These % cover should add up to 100%. Estimate what you see on the surface only. For example, if moss is covering a rock, then estimate the % cover of the moss, not the rock.

Definitions for ground surface conditions:

  • Slash = vegetation (boles, stems, branches, and leaves) that was cut in 2001.
  • Both cover (%) and depth in cm (the most common depth in the quadrat).
  • Bare = mineral soil, rock, anything not organic
  • Moss = moss species lumped. Remember to use the vertical projection of cover for moss growing on logs or stumps (this will tend to reduce the true cover).
  • CWD = non-slash, large (greater than 5 cm in diameter) woody detritus. This includes logs, stumps, and exposed roots.
  • Bole = total cover of bole of any live tree of any size (for species classified as trees see the list Species Codes, Names, and Growth Forms).
  • Litter = fine litter, organic matter, any dead branches less than 5cm in diameter.
  • Non-tree vegetation = stems of all vegetation other than trees such as grass, herbs and shrubs.

Estimates for canopy closure

  • Tree foliage cover = all foliage within vertical projection for live trees of any size.
  • This number will vary from 0 to 100%.

Species cover and biomass data

Percent cover should be estimated for every species that is in the vegetation quadrat. For example, if a species is rooted outside the quadrat, but it's foliage is hanging inside the quadrat, the species and cover should be assessed. Also, if a species is rooted inside the quadrat but some of its foliage is hanging outside the quadrat, only include the cover of the part of the plant inside the quadrat. Biomass measures are taken only when a stem is rooted in the quadrat.

Species Name. Write it out fully if you are at all uncertain about the acronym. This will allow us to correct erroneous acronyms. If unknown, record descriptive material here … (e.g., "grass with long awns")

Species Code. Based on Garrison et al. 1974. See the complete list of species names and acronyms. If a plant can only be identified to genus, record the first 5 letters of the genus. If a plant cannot be identified in the field, record it as "UNKN#" (where # is a unique #-# for the plot-quadrat). Collect a specimen from outside the quadrat and include a label in/on the bag with collector's name, date, and WS/transect/plot/quadrat number. Describe the morphology or draw a picture on the data form (back if necessary).

LC. Line count. LC = 1 for the 1st record of a species in a quadrat. If more than one line is necessary to record biomass measures, increment LC as necessary (e.g., 2, 3, etc.). All records for a species do not need to be recorded in order; species can be interspersed.

Cover (%). Projected canopy cover in percent. Cover estimates for the 2 x 2 m slope corrected quadrat should be done mentally or with extra PVC to divide the quadrat into quarters. Minimum cover = 0.1% (even if cover is less than 0.1%, record 0.1%. Maximum = 100%.

Cover should only be recorded once for a species (i.e., for LC = 1).

BIOMASS measures: DBA, DBH, Ht. (Height), No. of stems (or fronds), Len (Length of fronds). These data are recorded for a subset of species: Consult the form entitled Biomass Parameters to Measure. These measures are taken for only those species listed and only when the plants are rooted in the quadrat (not if plants overhang the quadrat from outside the boundaries).

If no stems are rooted in, check "Out?" column (see below). For large trees, "in" or "out" is based on the center of the tree. Only measure trees that are less than 5 cm in diameter.

DBA. For stems less than 5 cm in diameter rooted in the quadrat. Diameter at the base in cm (above major butt swell for tree species) using a caliper or small diameter strip. Measurements are to the nearest 0.1 cm. If a caliper is used on an oval-shaped stem, two measurements should be taken for the perpendicular axes of the stem and the values should be averaged. DBA should be recorded for (1) all tall shrub species (except RUPA), (2) trees without tags (DBH less than 5 cm). Each stem should be measured separately and its diameter placed on a separate line. However, if more than one stem occurs at a particular diameter, you can record the number of stems at that diameter in the "No. stems" column, thus saving additional data entry lines. The first DBA should be recorded on the line for which LC = 1 line (the one with the cover estimate).

Note: some herb species also require a DBA measurement: ARCA3, COCA2, LOCI, LOCR, PTAQ: simple measurement at the base. XETE: gather the leaves into a tight bundle and wrap the diameter strip around the clump at its base.

Height. Either the modal height (ht) (the most common height in the quadrat), or the individual height of a stem, if listed as such on the attached form Biomass Parameters to Measure (these would be coded as i-ht). Measure stem length (rather than height off the ground) because plants often grow at an angle to the slope. Units are in centimeters; precision is to the nearest 5 cm for plants 0 - 1 m tall; to the nearest 10 cm for plants 1 - 2 m tall; and to the nearest 20-50 cm for plants > 2 m tall.

Note: for XETE, when leaves are gathered to measure diameter, measure the length of the leaves when outstretched.

Number of Stems (or Fronds). Recorded for all ferns except POMU, and for PEFR2. The number of stems of a particular length (e.g., ADPE, ATFI, BLSP, POGL4) or diameter (PTAQ). For PEFR2 the number of leaves of a particular height. If different clumps have stems with significantly different lengths, list these clumps on separate lines. Likewise, for PTAQ, the number of stems of a particular diameter are listed on separate lines.

Length: Recorded for all ferns except POMU and PTAQ, and for PEFR2. The height of the fronds, or for PEFR2 the height of the leaf.

Out?. If a species with cover requires a biomass measure (e.g., diameter, height … see below), but it is not rooted within the quadrat, place a check mark here. This way we know that the biomass measure was not forgotten. Biomass measures are taken only when a stem is rooted in the quadrat.

Whole plot species list

All species encountered in the vegetation quadrats and tree measurements should be recorded on the datasheet entitled "Whole plot species list." A thorough inspection should then be made of the rest of the 250 m2 plot to add any vascular plant species not previously recorded. If a plant cannot be identified in the field, follow the directions given above under "species code."

Experimental Design - TP114:

Sampling Strategy:

The 2 small watersheds will have sampling plots arrayed along transects that are based on the original structure of the transect/plot network for each watershed. Five riparian plots will be added to this design in each watershed.

WS06 will have 16 upland plots that will be placed on a subset of the existing plot locations. The five riparian plots will follow the channel from the lowest elevation of that streambed in the treated area.

WS07 will have 17 upland plots and 5 riparian plots following the same criteria as WS06.

The riparian area will be determined during field reconnaissance, and the location of the riparian plots will be chosen subjectively. Because the riparian plots will have a different sampling density than the upland plots, the data from the riparian plots will be weighted according to the percent of total area sampled in the riparian zone vs. the upland zone.

Upland plots are set up as a series of parallel transects spaced 264 feet apart with plots spaced 264 feet apart. Riparian plots are spaced 115 feet apart and centered directly on the main channel of the stream. Circular plots 250 m sq with one central subplot (2 by 2 m) in upland plots and 2 subplots in riparian plots (1 central, 1 on outer edge).


Each plot will be a specified distance from every other plot and will be circular, 250 m2:

All live trees = 5 cm dbh will be tagged and measured for diameter, vigor, canopy class, and near tree. Since our primary goal is to get a rough estimate of biomass in these watersheds vs. tracking regeneration through time, we decided to focus on the overstory which should be a much larger contribution to biomass. Thus, we will not keep track of clumps nor attempt to measure trees less than 5cm in diameter except in the understory plots.

Diameters at base will be taken on cut tree stumps left from the harvest activity of last fall. These diameters, along with a taper equation determined from live trees on the plot, will be used to determine the dbh for the trees that were cut.

A subset of the trees in each plot will be cored and the cores collected for reading in the lab. The subset of trees will be taken from a portion of each plot (either ¼ or ½ of the plot) or from ½ of the plots in each watershed. This is yet to be decided. To be able to scale productivity measurements from this subsample of trees, we need to take the cores in a defined area, not from scattered trees throughout the plot as has been done in the past. A random sample of these cores will be used for determining nutrient concentrations.

Each plot will have a 2 x 2 m subplot in the center to be sampled for the understory and herbal components of the stand: Percent cover will be measured for all vascular species rooted in the plot and basal diameters will be collected for tall shrubs and tree seedlings. If the plan is to collect all the necessary data to generate biomass estimates, it is a bit more complicated than this … some “herbs” require diameters, heights, etc. and ferns require counts of fronds/heights so we still need to decide if our understory data collection will emphasize biomass estimates vs. biodiversity before we make final decisions about what understory data will be collected.

There is still some discussion as to whether we should take any estimates of canopy cover. I don’t believe that these make sense here unless we want to follow canopy closure of a thinned forest. I have been thinking of the measurement of these watersheds as a one-time snapshot of what is there now with a possibility of future measurements. Our one-time snapshot would then be available for the hydrologists if anything changes as far as streamflow etc. If anything really interesting happens, we can then go from there.

Dead wood will be sampled by both occurrence in plots (stumps, snags) and by line transects (downed logs). The line transects will also be used to sample fine woody debris and forest floor material. Mark is planning to much of this work with Jay and Becky and volunteers. This will not be a primary responsibility of the field crew.

Plant tissue nutrient concentrations will be sampled by collections of foliage, branches, and tree and forest floor cores. Exact method for sampling, selecting species, individuals, stratifying by size, etc. had not been decided yet.

We will take measure slope and aspect at each plot.

Data Management:

Physical collections (tree cores, forest floor material, sampled live materials) will be indexed and stored and all data will be processed and archived using FSDB protocols.

Garrison et al., 1976
Watersheds 6 and 7 at the Andrews Experimental Forest
Ground condition