Invertebrates as Indicators Invertebrates as Indicators of Human Impact on Soilof Human Impact on Soil

““How do invertebrate populations How do invertebrate populations change with soil compaction?”change with soil compaction?”

My First ModelMy First ModelInitial Question:Initial Question:

How are surface and underground bug populations different in areas that How are surface and underground bug populations different in areas that have experienced industrial pollution versus areas that have experienced have experienced industrial pollution versus areas that have experienced mild human development and areas relatively undeveloped and not mild human development and areas relatively undeveloped and not

exposed to recent pollution or human activity?exposed to recent pollution or human activity?

Hum

an Impact

As

Bug S

pecies Diversity

Exposure to P

ollution

And

Ratified IdeasRatified Ideas

Failure to collect sufficient data Failure to collect sufficient data indicating site pollution history indicating site pollution history

combined with faulty data collection combined with faulty data collection techniques techniques

Resulted in a revised question and modelResulted in a revised question and model

Revised Model:Revised Model:

Question:Question:

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

Human Activity

Soil Compaction

Aeration

Drainage

Nutrient Content

Insect Population/Diversity

AssumptionsAssumptions

1.1. Invertebrates could be used as an indicator Invertebrates could be used as an indicator species for soil compactionspecies for soil compaction

2.2. Soil density is a measure of compactionSoil density is a measure of compaction

3.3. Soil sample collection method is accurate Soil sample collection method is accurate enough to determine relative density of enough to determine relative density of various soil samplesvarious soil samples

A little background…A little background… In a study by Lindo and Visser it was determined that certain In a study by Lindo and Visser it was determined that certain

species of species of micro-arthropodsmicro-arthropods could be used as an could be used as an indicator indicator speciesspecies for human disturbance in the form of forest clear cutting for human disturbance in the form of forest clear cutting and that the and that the factorsfactors most likely most likely influencinginfluencing the changes in the changes in species diversity and abundance are species diversity and abundance are soil compactionsoil compaction and changes and changes in food availabilityin food availability

Significance…Significance… Study findings may support assumption #1 that invertebrates can Study findings may support assumption #1 that invertebrates can

be used as an indicator of soil compactionbe used as an indicator of soil compaction

Site SelectionSite Selection

Three locations at Discovery Park suspected of Three locations at Discovery Park suspected of having different soil densities were selected having different soil densities were selected for this experiment.for this experiment. Site #1on a main path leading from the visitor’s Site #1on a main path leading from the visitor’s

center to the loop trailcenter to the loop trail Site #2 on a less popular path leading behind the Site #2 on a less popular path leading behind the

visitor’s centervisitor’s center Site #3 located 30 paces off the path containing Site #3 located 30 paces off the path containing

site #2site #2

Location SelectionLocation Selection

2 data collection locations and 1 soil density 2 data collection locations and 1 soil density control location are selected for each site.control location are selected for each site.

At sites 1 & 2 the data collection locations are At sites 1 & 2 the data collection locations are placed off center of the path to prevent foot placed off center of the path to prevent foot traffic interference.traffic interference.

Control locations are 2 paces off the path for Control locations are 2 paces off the path for sites 1 & 2 and 2 paces from one of the data sites 1 & 2 and 2 paces from one of the data collection locations for site 3.collection locations for site 3.

Determining Soil Determining Soil Density/CompactionDensity/Compaction

Insert a standard bulb Insert a standard bulb planting tool into the soil up planting tool into the soil up to the 2” markto the 2” mark

Place soil from bulb Place soil from bulb planting tool into a standard planting tool into a standard 1 gallon freezer bag1 gallon freezer bag

Weigh soil samples using a Weigh soil samples using a triple beam balancetriple beam balance

Density=Mass/VolumeDensity=Mass/Volume Density can be compared Density can be compared

via mass measurements via mass measurements because all volumes should because all volumes should be constantbe constant

Soil Densities by SiteSoil Densities by Site

0

50

100

150

200

250

Soil by Site

Ma

ss

in

Gra

ms

Insect Collection ProceduresInsect Collection Procedures

1 pint glass jars are buried 1 pint glass jars are buried in the soil with lip even to in the soil with lip even to the groundthe ground

Leaves are tented over the Leaves are tented over the jar opening to prevent jar opening to prevent outside interference in outside interference in data collection data collection

Jars are left in place for Jars are left in place for 96 hour periods and 96 hour periods and checked for insects every checked for insects every 48 hours48 hours

Boat-backed Beetle

Common Black Ground Beetle

InvertebratesInvertebrates by Locationby Location

0

2

4

6

8

10

12

14

16

Boa

t-B

acke

d B

eetle

s

Com

mon

Bla

ck B

eetle

s

Cau

lum

bula

Sm

all S

pide

r

Mill

iped

e

Ear

wig

Uni

dent

ified

Ann

alid

Tot

al S

peci

min

s

Com

mon

Bla

ck B

eetle

Ear

thw

orm

Uni

dent

ified

Inse

ct

Sm

all S

pide

r

Uni

dent

ified

Bee

tle

Slu

g

Tot

al S

peci

min

s

Uni

dent

ified

Inse

ct

Sm

all S

pide

r

Mill

iped

e

Tot

al S

peci

min

s

Site 1 Site 2 Site 3

What it all means…What it all means…

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

YES!YES!

Conclusions:Conclusions:

1.1. Soil density has a visible Soil density has a visible effect on invertebrateeffect on invertebrate populations.populations.

Human Activity

DensitySoil Compaction

Aeration

Drainage

Nutrient Content

Insect Population/Diversity

Conclusions:Conclusions:

2.2. For soil compaction to affect insect For soil compaction to affect insect populations, the compacted area must be larger populations, the compacted area must be larger than the width of the paths chosen for this than the width of the paths chosen for this study.study.

3.3. The insect populations sampled for this study The insect populations sampled for this study most likely reflect the populations found in most likely reflect the populations found in areas with soil compaction equivalent to the areas with soil compaction equivalent to the control areas.control areas.