DISTRIBUTION
GENERAL ECOLOGY LABORATORY

Location: Aghaming Park floodplain forest
Objective: To assess the distribution pattern of trees in a floodplain forest
Hypothesis: Floodplain forest trees are distributed randomly.

Agenda:

Plot Method

1) Establish a grid (50 m X 50 m) consisting of 100 plots (each 25 m2) within a section of forest.

2) Tally the number of trees (all sizes) within each plot.

Plotless Method

1) Randomly place 50 flags within the same area that was used for plot sampling.

2) Measure the distances from each flag to the nearest and next nearest trees.



Analysis:

Plot Method

1) Determine the observed and expected (Poisson, random) distributions for the plot data (pp. 153-154, Table 4C.4). Your first step will be determining the mean number of trees per plot.

2) Compare the observed and Poisson (random) distributions graphically (Fig. 4C.4 and Fig. 4C.5, pp. 154-155). What distribution pattern (random, clumped, uniform) is suggested by the observed data?

3) Use a chi-square goodness-of-fit test (p. 156) to determine whether forest trees were distributed randomly. A calculated chi-square value > the critical value found in Table 1B.3 indicates the distribution is not random.

Plotless Method

1) Use the point-to-plant distances to calculate a Holgate index of aggregation (equation 20, p. 158), and use the index to determine the distribution pattern (0 = random, >0 = clumped, <0 = uniform).

2) Use a t-test (equation 21, p. 158) to determine the significance of the departure of the index from 0 (random). A calculated t-value >1.96 indicates the distribution is not random.

***Do the two methods (plot and plotless) produce similar results?***



Equipment:

Meter tapes

Flagging