This cache, and others in the area, are placed in the West Rocky Prairie area of the Mima Mounds with permission from the Washington State Department of Fish and Wildlife.
1. Regulations: knowing these are important before you visit this very fragile area:
- Stay on roadways. (The caches I have placed in the area may be a few feet off the roadway; however, each cache location has been approved by a staff person.)
- Foot traffic only. No bikes, horses or motor vehicles. Strollers would be acceptable.
- Dogs must be on a short leash and kept on the roadways at all times. It might be easier to leave them home.
- A Discover Pass is required.
Following these regulations will preserve the natural environment while still allowing the public to enjoy it.
Even one single short walk off the roadways will cause soil compaction. Compaction prevents the natural plant life from growing and allows hardier, invasive species to take their place.
2. In order to log this earthcache, copy and paste these questions into an e-mail to me.
- if sending answers for more than one person, give me those names with the answers.
- if someone else sent your answers, give their name in your found log.
- each person must post a personalized photo with his/her found log.
"Question" 0 - only answers sent through the message center can be guaranteed quick responses, particularly if I am traveling.
Question 1 - somewhere in your log mention that you walked to the posted coordinates and what the conditions were like when you did that.
Question 2 - this is more a requirement than a question - post a photo of yourself near the posted coordinates with your found log.
Question 3 - as you walk from parking to the coordinates, you will be walking through 3 distinct environments. Describe them in your own words. Proper names for the ecosystems are not necessary. Just be observant. Think about how this relates to the soil structure described below.
Question 4 - what two threats to the mounds did you observe on your walk? Be specific about what you actually saw, not just what you think is true.
Question 5 - give the average height and diameter of the mounds in this area.
3. Earthcache information
HOW WERE THE MOUNDS FORMED?
For theories about the formation of the Mima Mounds, refer to GC1E305, another great earthcache to visit.
WHAT IS A MAJOR THREAT TO THE MOUNDS IN THIS AREA?
While we may not fully understand the formation of the mounds, we do know some very specific threats to the health of the area.
A major threat to the Mima Mounds in this area is soil compaction. While the mounds actually sit on a base of flat, compacted clay soil, they themselves consist of fine gravel, loose sand, and decayed plants. There may also be some black sandy loam due to charcoal content from aboriginal burning on the prairies.
The top layer of organic-rich soil in the mounds is more than 2 meters thick, compared to most land surfaces where that layer rarely exceeds 1.5 feet in depth. This organic top layer contains dead plants and animals.
WHAT IS SOIL COMPACTION?
Soil compaction occurs when soil particles are pressed together, reducing pore space between them. Heavily compacted soils contain few large pores and have a reduced rate of both water infiltration and drainage from the compacted layer. This occurs because large pores are the most effective in moving water through the soil when it is saturated. In addition, the exchange of gases slows down in compacted soils, causing an increase in the likelihood of aeration-related problems. Finally, while soil compaction increases soil strength (the ability of soil to resist being moved by an applied force,) a compacted soil also means that roots must exert greater force to penetrate the compacted layer.
WHAT ARE THE CONSEQUENCES OF SOIL COMPACTION FOR PLANT GROWTH?
Soil compaction can have both desirable and undesirable effects on any plant growth. One of the desirable effects is actually undesirable for mounds preservation. That effect, desirable in other circumstances, is that slightly compacted soil can speed up the rate of seed germination because it promotes good contact between the seed and soil. In addition, moderate compaction may reduce water loss from the soil due to evaporation and, therefore, prevent the soil around the growing seed from drying out. It can also increase root branching and secondary root formation, allowing roots to more thoroughly explore the soil for nutrients.
In the Mima Mounds, however, desirable plant ecology already exists. The original soil structure was ideal for that plant life. By compacting the soil to any degree, this existing fragile plant life is damaged or killed. The slightly compacted soil is then a perfect medium for invasive species to grow and thrive, further robbing the native plants of their space and ability to continue to thrive. Taking the compaction a step further to the level of continual walking and driving prevents all growth of these fragile native species.
WHAT IS BEING DONE TO PRESERVE THE MIMA MOUNDS?
Controlled burns are one step to preservation of the area. In past years, the original inhabitants of the area burned the prairies on an annual basis. As a variety of trees and invasive species have started to thrive amongst the mounds, this practice has once again been established in well-defined areas.
Burns are fast due to the fact that there are only low growing plants. The soil does not have time to heat up and destroy the roots and bulbs of the established native plants. Very little compaction takes place during this practice.
There are times when volunteers spend time pulling larger invasive species. Again, the impact on the soil in the area is limited, and the benefits outweigh the negative.
WHAT CAN YOU DO?
Enjoy the area by remaining on the roadways. It is important that you don't allow your dogs to go off the roadways, either.
Volunteer your time. If this is something you would like to do, just look on-line for Mima Mounds volunteer opportunties.