Mangrove Soil Analysis

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Soil Analysis

Soil forms the basis of the world we live in. It is the top layer of the Earth’s surface, consisting of rock and mineral particles mixed with organic matter. There are many varieties of soil around the world from Clay to Sand and from Rainforest to Mud. Different types of soil have their own individual characteristics that in turn affect the suitability of growth. This is due to different nutrient levels, water holding capability, pH etc.

Many species of plants have adapted to better suit their soil environment. These adaptations have allowed certain plant species to thrive in an area in which other plants would never survive.

Mangroves are highly admired for the way they have adapted to live in a saline environment. Flora naturally need freshwater to survive just as we do. Then how can mangroves survive growing in salt water? Mangroves have adapted to filter out the salt when it is absorbed along with the nutrient filled water. This salt is excreted through roots, leaves and bark. What is left is freshwater that can be used by the mangrove. This may seem like a big deal when you could just grow in fresh water however this adaptation allows mangroves to have less competition from other flora.

The following experiments are to observe the individual characteristics of 3 different Zones of Mangrove Mud and also Beach, Rainforest and Clay Soil.

The purpose of these experiments is to carry out various experiments and thus observe the different characteristics of soils. These characteristics can be compared to see how differences in soil might determine the type of vegetation that grows there.

Safety Precautions:

Make sure gloves are worn at all times as there are some harmful bacteria and diseases in dirt.

Experiment 1 Soil Texture:

Aim: To find the percentage of sand, clay and silt in different soil samples.

Prediction: I predict that the soil with the highest percentage of sand will be the Trinity Beach sample. The soil with the highest percentage of clay will be the Clay sample. The soil with the highest percentage of silt will be the Outer Zone Mangrove Sample.

Materials:

* 6 x 200mL measuring cylinders        

* 3 x Mud samples from different areas of the mangroves (Inner, Middle and Outer Zones)

* Ruler with mm measurements          

* Disposable Gloves                              

* 3 x Samples of various areas (Beach, Rainforest and Clay Soil)

* Spoons                                

* Sieve

Diagram: (For Step 4 and 5)

Procedure:

  1. Sift all of the samples to remove insoluble lumps of dirt, plant debris etc.
  2. Measure 40mL of the first dried sample (for example Inner Zone Mud) into a measuring cylinder and label it accordingly.
  3. Fill the cylinder with 200mL of water and shake until all the dirt particles are mixed throughout the water.
  4. Put the cylinder down on a level bench and measure the depth of the sediment after the following time intervals: 30 seconds, 30 minutes, and 12 hours.
  5. Repeat for each dirt sample. Record results on the table.

Results:

Mangrove Mud:

Discussion:

There are many different kinds of soil and they all have there own individual characteristics that affect the flora growth in that type of soil. These characteristics are things like:

  • The capacity of soil to hold minerals and water
  • The movement (capillary action) of water into soil
  • The drainage ability of water through the soil

These are just a few of the characteristics affected by the amounts of clay, sand and silt present in the soil. These three sediment types were determined through the experiment above.

It was determined that the soil sample with the highest percentage of sand was Trinity Beach with 84.95% of the sample being made up of sand. This is obviously no surprise but note how it is still made up of other types of sediment. On average sand is made of silica which is a mineral similar to quartz and opal. This is a hard substance that resists erosion. This insoluble mineral does not offer the best conditions for flora growth as nutrient and water trapping in the “soil” is difficult. The sand in the Trinity Beach area upholds the characteristics outlined for silica however due to the results above it is evident that the soil also contains 12.12% of silt and 3.03% of clay. These other sediments may help to trap the necessary nutrients for plant growth in the soil. The flora that grows on the beach is hardy (casuarinas and Spinifex). This is due to the limited amount of water and nutrients available.

The highest percentage of Silt in the soil samples was Stoney Creek rainforest (76.32%). Rainforest is a nutrient high area where flora growth is prominent. This nutrient level is due to the way silt (and also clay) traps the nutrient rich water needed for the extensive growth. Silt is made up of finely eroded rock (this rock is largely made up of quartz and feldspar). This sedimentary silt is washed down with the rain and is trapped amongst the roots of trees. In relation to the mangroves, this silt is washed downstream in the annual floods and trapped in the particular roots (stilt, prop etc). This root network holds the nutrient laden silt to be used when needed. Without these roots (if the mangroves are cut down) the silt will wash through along with the nutrients. This silt collects at river mouths, causing shallower water and in the case of the nearby Great Barrier Reef in the Cairns area silt deposits that destroys the original habitat.

Obviously the clay soil sample contained the highest percentage of clay (53.70%). Clay, when wet, is a flexible substance that can be moulded at will. When dry it becomes rock like and perfect for holding soil together. This characteristic is highly beneficial to the environment in the way it helps to prevent erosion. Clay is not necessarily highly nutrient filled sediment but, like clay, it is finer grained and holds a lot of water. Soil with high clay percentages is not a preferable flora environment because it is not well draining. Some plants still live in clay soil and many Australian plants have adapted to this especially wattles. Mangrove Mud contains its fair share of clay (ranging from 36% to 46%). This clay is responsible for the sticky characteristic of mud when it is wet. Clay helps to hold the mud together to avoid it being washed into the river or wetland. Clay is not well draining and could be responsible for the way mangrove mud appears to be wet even when the tide has long since gone out.

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It was often difficult to take readings of the amount of soil that had settled at different time periods. In the case of the mud samples they are rich in silt and clay and this clouded the water. It was difficult to determine what was actually settled from what was still suspended in the water above. A reading was taken and this was compared to readings taken when the water had cleared and all particles had settled. At this stage it was quite easy to see the different sediments that had settled. This difficulty in recording the levels could ...

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