BIOMASS DISTRIBUTION IN THE FOREST AND PRAIRIE

 

Laboratory 1

 

Forest Ecology - FOR 3213

 

The purpose of this exercise is to gain direct experience measuring primary production and energy transfer and storage. This will be achieved through measurements of the components of biomass in a prairie and forest in the Cross-timbers.

Methods:

Prairie - Measure biomass (oven-dry weight) of all above- and below-ground biomass in a square plot, 50 cm on each side (surface area = 0.25 m2), for the following components: 1. standing live, 2. standing dead, 3. litter, 4. crowns 5. roots to 60 cm depth by 15 cm increments. The roots will be sampled with a posthole digger and separated from soil in the field. The diameter of the hole should be 17.8 cm (surface area = 0.025 m2). Determine oven-dry weight after 48 h in oven at 70°C. Report data on a per hectare basis for each component.

Forest - Determine biomass of the following: 1. leaves, 2. twigs, 3. branches, 4. trunk, 5. understory, 6. litter, 7. roots to 60 cm depth by 15 cm increments. All of the herbaceous and woody understory plants alive and dead < 1 cm dbh will be included in the category "understory." The understory plants and litter will be sampled as above for the prairie. Plants > 1.0 cm dbh should be measured for dbh on a circular 0.01 ha plot (radius - 5.64 m). Use the following regression equations and ratios to determine the biomass:

1. log10 (total twig and leaves (g)) - 1.721 + 1.691 log10 (dbh (cm))

note: leaves = 82% of total

2. log10 (branches (g)) = 1.571 + 2.313 log10 (dbh (cm))

3. log10 (stem bark (g)) = 1.692 + 1.983 log10 (dbh (cm))

4. log10 (stem wood (g)) = 1.980 + 2.278 log10 (dbh (cm))

5. root crown = 21% of total aboveground

6. roots = 26% of total aboveground

 

The trunk biomass is the sum of the biomasses of the stem bark, stem wood and root crown. Determine the biomass of each component and express on a per hectare basis. Please note you will have two values for roots in the forest, the measured and the calculated values. Include both values in the report for comparison.

Plot size Multiplier Final Units

0.025 m2 4 x 105 ha

0.25 m2 4 x 104 ha

0.01 ha 1 x 102 ha

Report: The report should show in a table the total biomass for each vegetation type and the percentage of biomass in each of the components. All values should be shown as kg ha-1. We will use the averages for all the plots for the biomass table. The report should include a discussion of the data. Be sure to compare biomass distribution in the prairie and forest on both on absolute and relative scale. Answer the following questions. In all cases explain your answer and show data.

  1. Compare the results from your measurements to those called research on the sheet. The research data were published for sites in Oklahoma.
  2. Compared your results to published data in the course text. Are the Cross-timber sites you measured productive compared to other forests? Do the sites you measured appear to have a larger than average amount of biomass? Is the distribution of biomass unusual?
  3. Is the ratio of NPP to biomass the same in both ecosystems? Is the ratio of NPP to live foliage the same in both ecosystems? Discuss your findings.
  4. Was there any evidence of secondary producers? Which ecosystem would support the largest biomass of secondary producers and why?
  5. How could the NPP be increased ? Give three different ways. Explain your answer.
  6. The Cross-timbers covers 4.8 x 106 ha in Oklahoma, Kansas and Texas. If it were 70% forested and 30% prairie, what would the total biomass and NPP be in tons for the entire area. What would the total biomass and NPP be if the Cross-timbers changes to 100% forest.