Lab #7 Growth Characteristics of Amur Honeysuckle

Rather severe negative impacts of L. maackii on the growth and survival of native herbaceous species and seedlings have been demonstrated in several studies (Gould and Gorchov 2000, Collier and Vankat 2002, Miller and Gorchov 2004). Methods for eradication of L. maackii, and the regeneration of native species following L. maackii eradication (Hartman and McCarthy 2004), are a principal focus of ongoing research in the Gordon Natural Area directed by Dr. Gerry Hertel.

The purpose of this lab is to determine the growth, age structure and biomass allocation of individuals of L. maackii growing in forested vs. more open locations within the WCU Gordon Natural Area (GNA), where the species has become prevalent. The “open” location is a former orchard, abandoned between 1970 and 1980; the forested location is directly adjacent (Fig. 2).



Fig. 2. Aerial photo of study area in 1970 (L) and 2005 (R).


L. maackii is thought to have colonized the area sometime in the 1970s, but whether it arrived first in the wooded area, or in the abandoned orchard, is unknown. Although the species is known to successfully colonize both open and closed habitats, previous work suggests that rates of new stem production, stem mortality, and leaf production per stem may all be influenced by light availability. The dispersion of genets may thus reflect the patchiness of light as well as seed dispersal. Determination of the age of the oldest (usually central stem) will be used to infer the history of establishment by L. maackii in the GNA.

This is a three-part lab. During the first week we will destructively sample several genetic individuals (genets), collecting a range of morphometric data in the field. Teams will age the stems they collected during the following week, and then analyze the data for growth and age properties using Excel during the second lab period.

The class will divide into teams, each assigned to one or more genets. The following equipment will be needed in the field:

 hand saws

 canopy densiometer

 Spring balances

 Quart baggies for returning stem sections to lab for age determination

Each team is responsible for determining the age, diameter and weight of each stem on the genet(s) chosen for study. Fill out the information in Table 1, except for Stem Age, in the field. Retain Table 1 at the end of the field trip for later age analysis:

Now sever each stem, one at a time, at a distance of 10 cm above its base. The cut should be as nearly transverse (perpendicular to the stem length) as possible. Make a second transverse cut about 2 cm further up the stem, and place the 2-cm plug in a quart baggie with a tag indicating sampling date, genet number and stem number. This will be used next week for age determination. Dead stems should be collected as well for measurement of diameter, but will not be aged. Finally, record the stem weight using a spring scale.

Each team should meet with me outside of class time during the week between the fieldwork and indoor data analysis.

Dip one end of the plug in a Stender dish of phloroglucinol for 30 seconds (do not over-stain the plug). Blot once on a piece of paper towel, then dip the end into a second Stender dish of concentrated HCl (corrosive!! be careful not to spill or drip, and notify the boss immediately in the event of a mishap). Again blot dry on a piece of paper towel, then rinse in DI water. Place the plug on a piece of Sharpie-labeled towel, and allow to dry prior to the next lab.
Data Analyses (Part 3)

In SSN381, use sand paper to create a fine surface for viewing the growth rings. Dissecting scopes are available to enhance the image. “Rings” are produced by the alternation of large xylem vessels (produced in the growing season) with smaller xylem vessels produced during the winter. Count the number of rings to determine the age, with 0 = New stem produced this year, 1 = 1 year old (produced last year), etc. See Figure 2 for an example. Once all plugs from your team have been aged (and helping out other teams if necessary), head to the computer lab.

In addition to the columns for Stem Number, Stem diameter, Stem Weight, and Stem Age in columns A-D (in which you need to add your data), notice that column E automatically calculates the log₁₀(stem diameter). Two additional columns contain calculations of what the biomass of stem and branches (combined) should be for a stem with the diameter you entered for a plant growing in the open, with high light (HL) conditions (column F) or under a closed canopy with low-light (LL) conditions (Column G). These are estimates based on a study by Luken (1988; Table 1) of L. maackii in Ohio.

In row 23 use the SUM function to obtain the total weight of all stems (in D23), and the predicted total weight of the stems if the genet had grown under high light (HL) vs. low light (LL) based on Luken (1988) (in cells F23 and G23). Add the summary data for each genet to the table in “Class Data” and on the white board for general class use.

Return to the “Team Data” for your first genet. Highlight the data for Age and (immediately to the right) stem weight including the column titles Age (yr) and Stem Wt (g). Insert an XY Scatterplot below the template. Clean up axis titles, and save the spreadsheet with graph for your write-up. Repeat this procedure for any other genets evaluated by your team.

Now click on the “Class Data” spreadsheet. Highlight the first 4 columns including column titles (for the Orchard data), and pull down under Insert to XY Scatterplot. Customize the resulting graph with appropriate axis titles, and label the graph Orchard. Similarly, create a graph of the Woodlot data, and again customize the titles. Save these two graphs for your write-up.
Write-up

Answer the following questions.

1. 
   Evaluate the age structure of each genet sampled by your team. Where was it found (orchard or woods), and when (what year) did it become established in the area? Summarize its general growth trajectory. (e.g., How rapidly were additional ramets added to the genet? Did any stems die? ). Append the graph of stem weight vs. age of the stems for each genet.
   
2. 
   Recognizing that Luken’s (1988) data excluded leaves, and that his study described very open vs. closed-canopy habitats in Kentucky (unlike the current dataset describing growth under varying light conditions in Pennsylvania, recorded at the very end of the growing season, and including leaves), how closely are the class data related to Luken’s previous work? Is there evidence that genets that colonized the orchard may have benefitted from the initial growth conditions it provided? Discuss, and append the graphs for both the Orchard and Woodlot data.
   

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