PROTOCOL FOR SAMPLING SOILS IN LANDSLIDES

D. J. Lodge, January 1992 (revised Feb. 4, 1992)

*Description of revegetation plots.*

Each of the extensive and intensive landslides in which we are studying revegetation in the LTER has plots 2x5 m distributed along transect lines at 10 m intervals from the upper lip of the slide. The intensive slides (ES-1, ES-2 and RB-2) have 24 plots each, with a 2x1 m seedling subplot along the lower edge of the plot. The extensive slides have various numbers of plots, and there are no seedling subplots within them.

*Taking the soil samples.*

Take two volumetric soil cores from each plot using the metal ring. These are 9 cm deep with a 12cm diameter. You need to drive it all the way into the soil so that the upper rim is even with the surface. Use a board placed over the ring and pound it with a small metal sledge hammer to drive it in.

Take implements to dig out the soil contained in the ring (e.g. trowels- pallitas, or spoons), and place the contents of the ring in a plastic bag labeled with the landslide name, the plot number (#-# corresponding to the transect line and the distance in meters from the right side of the slide), if it is on the left or right side of the plot, and the date.

The plastic coring tubes do not work well in the landslide because of the quantity of rocks. The final nutrient availability in the plot is calculated by adjusting for the quantity of real soil per unit volume - so we need an accurate

Estimate of the volume of rocks in the sample. Don’t shift the position of the sampling to avoid rocks. If the cores won't go in far because it hits solid rocks, then note this on the sample.

*Placement of the soil samples in the plots.*

In the intensively sampled landslides, take the cores just up hill of the string that divides the large and small subplots.

The division between the plots is located 1m uphill of the lower edge.

In extensively sampled slides, take one sample near the lower left corner, and the other near the upper right corner.

*What to do with the samples when you bring them in.*

Remove 50g fresh weight of soil from each of the two cores from each plot. Pool these together, and use them for seed bank germination experiments with Dr. Randal Myster.

Send the rest of the sample to San Juan - refrigerate if there is any delay.

*Instructions for San Juan Root and Soil Lab.*

Weigh the entire sample, and add 50g to this weight (the amount removed at El Verde for seed bank studies).

Sieve out large rocks on the 4-5 mm mesh sieve/funnels.

Weigh and record rocks.

Remove roots from soil samples by hand. Put live roots < 2 mm diameter into vials with FAA and store in the cabinet for volatiles that is vented to the outside. Place larger roots in paper bags labeled with the landslide, and plot number (roots from the two cores in each plot can be put into the same paper bag), dry, record dry weight, and throw out these root samples.

NOTE: if there is no microbial ecologist interested in the mycorrhizae samples as of December 1992, throw out the roots preserved in FAA and discontinue this part of the procedure.

Instead, place all roots into the bags for drying and weighing.

Consult Jean Lodge and Randall Myster before throwing out roots.

Mix the soil from the big sieve (4-5 mm mesh) in an inflated plastic bag.

Take a sub sample of mixed soil weighing about 100 g, record the initial weight, and pass it through a 2 mm mesh sieve. If there are rocks remaining on the sieve, weigh and record these. Extract 4 g of the fine-sieved soil with KCL and send it for ammonium and nitrate analysis (One extract per Soil core). Freeze the extract if there is a delay in analysis. Take the remaining fine-sieved soil, and get wet and dry weights for percentage moisture (dry at 40-50 C, not any higher). Take the remaining coarsely sieved soil and air-dry it by spreading it out on the plastic bag. Do not do this in the room where the fertilizers are stored.

The soils will be analyzed for nutrients by Bruce Haines at the University of Georgia and Dr. Zoo at Terrestrial Ecology (N, C, Olson P, K, Ca, Mg, Fe, Al). The fine-sieved soil from ES-2 and RB-2 should be sent to Dr. Haines for nutrient analysis, and the coarsely sieved soil should be saved for Dr. Zou (it will need to be finely sieved after it is dry for Dr. Zou - consult him for instructions). Dr. Randall Myster will store the soil samples in his.

office so they are not misplaced.

NOTE: The percentage soil moisture is only one measurement in time.

If moisture availability to plants is desired, I suggest placing porous cup tensiometers in the sample plots and sampling them on a regular basis.

An analysis of the soil texture is valuable in determining water availability (sand holds less water than clay; see Dr. Zou). If something more sophisticated is desired, Dr. Bruce Haines at the University of Georgia can test

Intact soil cores on a tensiometer plate to determine the percentage soil moisture at 0, -5, -10, and -15 bars, etc.

*Data Analysis and Management:*

The following data should be sent from the soil lab to Eda Melendez for data entry in the landslide soil data set of the LTER landslide revegetation project, and to Dr. Randall Myster.

Landslide Identifier (e.g., ES-2, RB-2)

*Sampling Date*

Names of the people taking the soil samples

Plot Identification: Transect number - Plot number (e.g., 6-14)

Location in the Plot: for Intensive landslides (ES-1 and ES-2),

R (right, when facing the top of the slide), and L (left);

For - Extensive slides, LL (lower left) and UR (upper right)

Total Initial Fresh Weight (weight of the entire soil core fresh

(Add the 50 g removed at El Verde to the weight recorded in San Juan).

Weight of large rocks removed on the 4-5 mm mesh sieve.

Weight of wood or dead organic matter

Fresh weight of roots

Dry weight of roots

Weight of soil sub sample (ca. 100 g) put on the 2 mm mesh sieve

Weight of rocks remaining on the fine (2 mm mesh') sieve.

Weight of finely sieved soil placed in tube for extraction of N with KCL (about 4 g).

Wet weight of the finely sieved soil sub sample that was placed in the drying.

The preceding data should be aligned with soil nutrient data from the chemistry lab and the Univ. of Georgia chem. lab.

*Calculating Nutrient Availability in the top 9 cm of soil: *

1. Calculate ‘effective’ bulk density (this accounts for the fact that a large fraction of the ‘soil volume’ may be rock).

Subtract the following weights from the Total Initial Fresh

*Weight:*

Weight of big rocks (from 4-5 mm mesh sieve)

Fresh weight of roots

[Weight of small rocks on 2 mm mesh sieve]/[Weight of soil sub sample placed on 2 mm mesh sieve] X {[Total initial fresh weight – (big rocks + fresh roots)]/[weight of soil sub sample placed on the 2mm sieve]}

*This is the wet weight of real soil in the core sample:

Take the wet weight of real soil (as calculated above) and multiply by the fraction of the wet soil weight, which is soil (i.e., not water).

The fractional dry weight of the soil is calculated as:

[Net dry weight of finely sieved soil] / [Net wet weight of finely sieved soil that was placed into the drying oven].

To calculate effective bulk density of soil for each core sample:

Divide the dry weight of the soil in the core sample (from above) by the volume of the core in cubic centimeters.

The volume of the corer is as follows:

V = 3.14 * (6.0 cm)2 * 9 cm

V = 3.14 * 36.00 cm2 * 9 cm

V = 1,017.36 cm3

*To calculate nutrient availability for the plot*.

First take the effective bulk density of soil from each core (from above) and multiply by the nutrient concentration per g dry weight of soil from the corresponding soil sample. This gives the nutrient content of the top 9 cm of soil from each sample.

Second, determine the mean amount of nutrients available per soil core by averaging the results from the two cores.

Third, calculate the nutrient availability for the top 9 cm in the entire plot as follows: The mean nutrient content of the core samples represents 36 cm2 of surface area to a depth of 9 cm.

Your plot is 2 X 5 m. To get the nutrient content on a per m2 basis, multiply the mean nutrient content of the soil cores by 277.77 (you should now have g or mg of nutrients per m2 to 9 cm depth). There are 10 m2 in each plot, so multiply your nutrient content per m2 to get nutrient content of the soil in the entire plot to 9 cm depth.

*Who needs these data?*

The members of the landslide revegetation project: Dr. Lawrance Walker, Dr. Bruce Haines and Randall Myster. Dr. Randall Myster will be responsible for checking the accuracy of the data management reports, and transmitting data to Dr. Walker and Dr. Haines. The soils data will be compared to the patterns of revegetation by particular species of landslide colonizing plants.