Soil Bulk Density, Total Pore Space, and Compaction Due to Human Foot Traffic Jessie Meeks and Ali...
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Transcript of Soil Bulk Density, Total Pore Space, and Compaction Due to Human Foot Traffic Jessie Meeks and Ali...
Soil Bulk Density, Total Pore Space, and Compaction
Due to Human Foot Traffic
Jessie Meeks and Ali Theuer, 2001
Contents:
ïPurpose and ObjectivesïSitesïMethodsïDataïDiscussionïWrapping up
We explored the relationship between calculated soil bulk density (g/cc) and estimated amounts
of human foot traffic.
ïSoil compaction increases bulk density and decreases pore space.ïA decrease in pore space leads to increased erosion and decreased soil productivity.ïLogging trucks are a known hazard, what can feet do?
Site 1: located on the Brook Trail, visited by less than 1,000 people annually (thatís 2,000 feet every year)
Site 2: located along the river trail, visited by just over a thousand people annually
Site 1Site 2
Site 3: located along the main loop trail, over 10,000 visitors per year
Site 4: located along aside trail with about 10,000 visitors per year
What did we do?
Soil samples were obtained by hammering a can of known volume into the ground,
both on and off trail at all four sites.
We took keen and meticulous notes and observations.
Samples were taken back to the lab and weighed.
The shape of some of the cans was compromised while hammering them into the soil.
The new volume of each can was determined using a graduated cylinder.
What did we find?
Bulk Density Data
Site 1 Site 2 Site 3 Site 4 Averages
bulk density=hydrated weight(g)/volume(cm3)on trail BD
265.92g/190.00cm3=1.400g/cm3
677.71g/350.00cm3=1.936g/cm3
218.75g/160.00cm3=1.367g/cm3
881.85g/500.00cm3=1.764g/cm3 1.617g/cm3
off trail BD549.42g/530.00cm3
=1.037g/cm3676.35g/460.00cm3
=1.470g/cm3645.01g/570.00cm3
=1.132g/cm3622.41g/550.00cm3=
1.132g/cm3 1.193g/cm3
difference .363g/cm3 .466g/cm3 .235g/cm3 .632g/cm3 .424g/cm3
% difference 25.93% 24.07% 17.19% 35.83% 25.76%
Bulk Density On and Off Trail
1.400
1.936
1.367
1.764
1.037
1.470
1.132 1.132
0.000
0.500
1.000
1.500
2.000
2.500
0 1 1 2 2 3 3 4 4 5
Site
Bulk Density (g/cm3)
on
off
What does it mean?
ïAn average difference in bulk densities of 25.76% between on trail and off trail was calculated
ïAs bulk density increases, pore space decreases
ïBulk density was greater on trail than off trail, therefore pore space is less on trail
ïSoil bulk density reaches a maximum, leveling off (i.e most of the pore space is compacted)
ïLess pore space results in increased soil erosion and decreased soil productivity
ïRelationships among the number of hammer blows, crumpling of cans, and the calculated bulk density were observed
SummaryHigher bulk densities on trails suggest that their soils areless productive and more susceptible to erosion than their offtrail counterparts
Error: a loss of soil mass may have ensued in the Transporting of samples from container to container
Study Improvements: continue the study over several years, varying the levels of foot traffic at the sample locations,and tracking the bulk density and total pore space over time.
Thanks!