For this past week I have been diligently working to decode a massive spreadsheet containing experimental data sampled from around the Brazilian Amazon Rainforest. While I had significant trouble opening it, because it was created in Quattro Pro, I was able to translate into MS Excel format. The zipped datasheet can be downloaded here (500K).
Once I was able to open the file, I began translating and interpreting the data it contains. This spreadsheet was created by Gustavo Negreiros of the University of Washington using data obtained from RADAMBRASIL (I'm not sure if this is the correct link - it's in Portugese), EMBRAPA/FAO, etc. Below is an overview of the table and column structure:
Note: Most of the translations were determined using “babelfish” and are represented using <>.
- Table Name: < Ground Profiles of the Amazon >
Column Names:
- Profile Number (author's reference)
- Volume that the data came from (RADAM)
- Latitude (Hours, minutes, seconds, etc.)
- Longitude (ditto)
- Chart Reference (?)
- Profile Class (using a Brazilian system)
- Original Material
- Horizon Symbol (?)
- Initial/Final Depths of Horizon (sample) (cm?)
- Texture Analysis (soil profile in ?, ?, coarse sand, fine sand, silt, clay) (%)
- H2SO4 Analysis
- pH, C, N, Organic Material Analysis (%)
- Comments on the Data
So, basically, what we have is a compilation of samples taken at (usually) five different depths testing for soil profiles, nutrient concentrations/volumes, etc.
Using this table information, I began to analyze the 7000+ lines of data I had at my disposal. My findings and conclusions are listed below:
Note: Unless otherwise stated, the below figures are averaged across all samples taken at all depths among all the sites of the project in the Brazilian Amazon Rainforest.
- pH – H2O Analysis – 4.89
- pH – KCl Analysis – 4.17
- H2O and KCl refer to different methods for testing for pH (Eva). The KCl value is expected to be lower than the H2O value.
- Because most of the samples were taken in areas that were (probably) not very disturbed at the time, it can be concluded that the soil of the Amazon Rainforest is naturally acidic.
- If this is the case, acid rain may not actually be an issue within the Rainforest (we are currently researching this).
- Also, although the data is a little rough in this area, it appears that the pH of the soil seems to increase with an increase in the depth of soil samples. We are currently researching to see if this is associated with the bedrock.
- C% - 0.92%
- N% - 0.1%
- Organic Matter % - 0.1%
- Although we are not entirely sure what was being tested here, it appears that carbon, nitrogen and “organic matter” concentrations are extremely low in Amazonian soil
- What is not represented here is the sharp change in nutrient concentrations in different soil layers. Nutrients become much scarcer as the depth of the sample increases, even by a small amount. For example, in one sight, an increase in sample depth from 0-5cm (not sure about units) to 20-50 cm gave rise to a change in C% from 2.77% to 0.55%.
- Clay (<0.002mm) – 34%
- Silt (0.002-0.05mm) – 26%
- Fine Sand (0.05-0.2mm) – 25%
- Coarse Sand – (0.2-2mm) – 20%
- “Cascalho” - (2-20mm) – 6%
- “Calhau” - (>20mm) – 0.4%
- It is difficult to draw any conclusions from this data alone, except that the average particle size of the soil in the Amazon is quite small.
- However, when surveying the spreadsheet it can be easily seen that the percentage of clays and silts increase with and increase in sample depth. Clays and silts are not as porous as sands and therefore have decreased ability to hold water and provide nutrients to the plants. I am currently researching variables affecting PAW (plant available water).
So, what we have in this data is the beginnings of a definitive characterization of the land of the Brazilian Amazon Rainforest. As a group we determined that the following list contains the key points we must attend to in our characterization:
- pH
- Soil profile
- Nutrient concentrations/volumes
- PAW (plant available water) and therefore the porosity of the soil (soil profile)
- Underlying bedrock and its effect on the stability/pH of the soil
- Erosion
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