Invertebrates as Indicators of Human Impact on Soil

1
Invertebrates as Indicators of Human Impact on
Soil

• How do invertebrate populations change with soil
  compaction?

2
My First Model

• Initial Question
• How are surface and underground bug populations
  different in areas that have experienced
  industrial pollution versus areas that have
  experienced mild human development and areas
  relatively undeveloped and not exposed to recent
  pollution or human activity?

3
Ratified Ideas

• Failure to collect sufficient data
• indicating site pollution history
• combined with faulty data collection
  techniques
• Resulted in a revised question and model

4
Revised Model

• Question
• Are insect populations different in habitats
  characterized by serious, moderate and minimal
  soil compaction? Which insects survive better in
  areas with soil compaction?

5
Assumptions

1. Invertebrates could be used as an indicator
   species for soil compaction
2. Soil density is a measure of compaction
3. Soil sample collection method is accurate enough
   to determine relative density of various soil
   samples

6
A little background

• In a study by Lindo and Visser it was determined
  that certain species of micro-arthropods could be
  used as an indicator species for human
  disturbance in the form of forest clear cutting
  and that the factors most likely influencing the
  changes in species diversity and abundance are
  soil compaction and changes in food availability
• Significance
• Study findings may support assumption 1 that
  invertebrates can be used as an indicator of soil
  compaction

7
Site Selection

• Three locations at Discovery Park suspected of
  having different soil densities were selected for
  this experiment.
• Site 1on a main path leading from the visitors
  center to the loop trail
• Site 2 on a less popular path leading behind the
  visitors center
• Site 3 located 30 paces off the path containing
  site 2

8
Location Selection

• 2 data collection locations and 1 soil density
  control location are selected for each site.
• At sites 1 2 the data collection locations are
  placed off center of the path to prevent foot
  traffic interference.
• Control locations are 2 paces off the path for
  sites 1 2 and 2 paces from one of the data
  collection locations for site 3.

9
Determining Soil Density/Compaction

• Insert a standard bulb planting tool into the
  soil up to the 2 mark
• Place soil from bulb planting tool into a
  standard 1 gallon freezer bag
• Weigh soil samples using a triple beam balance
• DensityMass/Volume
• Density can be compared via mass measurements
  because all volumes should be constant

10
Soil Densities by Site
11
Insect Collection Procedures

• 1 pint glass jars are buried in the soil with lip
  even to the ground
• Leaves are tented over the jar opening to prevent
  outside interference in data collection
• Jars are left in place for 96 hour periods and
  checked for insects every 48 hours

Boat-backed Beetle
Common Black Ground Beetle
12
Invertebrates by Location
13
What it all means

• Is there a connection between soil density and
  invertebrate populations size and diversity?
• YES!

14
Conclusions

• 1. Soil density has a visible effect
  on invertebrate populations.

15
Conclusions

• 2. For soil compaction to affect insect
  populations, the compacted area must be larger
  than the width of the paths chosen for this
  study.
• 3. The insect populations sampled for this study
  most likely reflect the populations found in
  areas with soil compaction equivalent to the
  control areas.