Intro to Ecology, ECOL 100

Sampling techniques

Laboratory ontechniques to sample vegetation

A bit on background information (modified after D. Ressler, 2004)

The two forests we will visit are Tall Timbers Natural Area and ShadeMountain. We will consider Tall timbersas an old-growth stand of hemlock(Tsuga canadensis)and white pine(Pinus strobus)that was never logged. The forest plants and soil in this area are the closest remnants of what the landscape would have looked like 300-400 years ago. This area is underlain by the Juniata Siltstone and Bald Eagle Sandstone. The former is a grayish red siltstone and sandstone, and the latter is grayish red sandstone.

ShadeMountain has been logged at least three times, on or about 1850, 1920, and 1950. Local residents know blueberries grow best when the forest is thin, so the mountain has been illegally burned on several occasions since the last logging (1950). This mountain represents a frequently disturbed landscape. ShadeMountain is underlain by the white Tuscarora Sandstone, a highly resistant, cemented sandstone and conglomerate. On the western edge, the older bald eagle Sandstone, grayish red sandstone is exposed.

The study locations are only about ten miles apart, lie on virtually the same bedrock formations and are only separated by a small valley. Geologically, they have the same materials from which soils can form, both lie between 1,800-2,200 feet above sea level, so they should have the same climate. During the investigation, make specially note of the soil depths and features, the species present, their characteristics, and their density (number of individuals per area). You will compare these and other characteristics for your lab report.

Once you get to the forests, you should take notes of:

-Identification of the place

-Site description

-Diversity

-Dominant spp & Spp list

-Spatial distribution

-Understory architecture

-Look at organic matter, detritus, and leaf cover at both forests

FOREST ANALYSIS

(After G. Boone, circa 2000)

The analysis of community structure can be a daunting task. The size of a community may prevent you from getting an overall view of the composition and determination of dominant organisms.

A forest presents a unique problem because of its size and the size of individual members of the forest. The size also limits observations as to the common and rare members in the forest.

Using commonly accepted sampling techniques we can determine species; frequency, density, dominance, and importance value, among others.

Normally it is impossible to count all the individuals in a community (a census) so we settle for a sample of the community. In doing so, we must then calculate estimates of the total community based on a few measurements.

There are many different approaches to sampling a community including plot and plotless methods. Plots may be square, rectangular, circular or some other shape. The term quadrat is often interchangeably used for plot, but strictly speaking, a quadrat is a square plot. Quantitative plant sampling methods then can be divided in Plot methods and Plotless methods. Within plot methods, we will mention “Quadrats method” & “Line-Intercept method”. Among plotless methods we will see (and use) “Point-quarter method” (see table).

Quadrats method

A quadrat is usually a square sample unit or plot, which in a vegetation survey may be divided into subplots. Quadrats vary in size, shape, number and arrangement, depending upon the nature of the vegetation and the objectives of the study. In some studies, a quadrat is rectangular, although often circular plots are done. Circular plots can be the easiest to layout, requiring only a center stake and string of desired length. Rectangular plots appear to furnish a more accurate sampling of vegetation composition.

Line-Intercept method

Line-intercept sampling is one-dimensional, and is most useful for sampling shrub stands and woody understory of the forest. The method consists of taking observations on a line or lines laid out randomly or systematically over the study area.

Using any plot method, you will determine the plot size, and then you need to lay out plots, and gather data such as species name, number of individuals per plot, and circumference or diameter of each stem at breast height (CBH or DBH).

Point-quarter method

Point-quarter sampling is useful in sampling communities in which individual plants are widely spaced or in which the dominant plants are large shrubs or trees. The method is especially useful for surveying large tracts of land in which many data points should be obtained, but each data point should not require a long time for data acquisition. Thus, this method can sometimes represent a "quick and dirty" technique for canopy surveys.

In point-quarter the height of each tree may be obtained as a method of indicating the age of certain tree stands. Using a plotless technique is less time consuming because the researcher does not spend time laying out the plots.

PLOTLESS METHOD

This method, as the name implies does not require the construction of plot boundaries. We select a random point and use a compass to create 4 quadrants (see figure). Locate the tree nearest the point in each quadrant, identify the tree to species and measure the distance from the point to the tree and the CBH (or DBH) in meters. Use only living trees and trees with a CBH > 15 cm. Record these three pieces of data (species, distance, circumference).

The easiest way to record data is to assign each species a number. Then when you record a species, distance, circumference, etc. all you need to do is record a number rather than a name.

For example, 1-15-.89

might read 1 = white pine (Pinus strobus), 15 meters from the central point and .89 meters CBH.

You can use this for all methods. Many authors recommend a minimum of 25 points or samples of data.

Table 1 - Plant Composition

Tall Timbers / ShadeMountain
Species
Hemlock, Tsuga canadensis / Red maple, Acer rubrum
Yellow birch, Betula alleghaniensis / Turkey oak, Quercus laevis
Witch hazel, Hamamelis virginiana / White pine, Pinus strobus
Pitch pine, Pinus rigida
Poplar, Populus sp

Intro to Ecology, ECOL:100 Sampling techniques

Datasheet for recording Point-Quarter data

(SP is the species name or number; D is distance from the center point to the plant, in meters; CBH is circumference at breast height, in meters)

Date:Locality:

Point
Number / Compass Quadrant
Northeast / Northwest / Southeast / Southwest
SP / D / CBH / SP / D / CBH / SP / D / CBH / SP / D / CBH
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

Sampling Tech - # 1