City’s Umbrella: 4 B.C. Evergreen Bushes’ Canopy Rainwater Interception Ability

By Herong (Alina) Zhang
Intermediate Category (Grades 9-10)
Experiment | Environment

Out of Buxus microphylla (boxwood), Taxus chinensis (Chinese yew), Euonymus japonicus (silver euonymus), and Cedrus (cedar bush), which bush has the best canopy interception ability?

If I measure the soil mass difference between dried soil samples before the experiment and after the experiment under Buxus microphylla, Taxus chinensis, Euonymus japonicus, and Cedrus, then I will find that Buxus microphylla will have the least soil mass difference, because out of the experimental group, Buxus microphylla has the densest-packed and thickest leaves. This gives Buxus microphylla bush a better ability to intercept, hold while absorbing the rainwater with its strong and dense canopy.

Firstly, I collected 100g of soil in 3 different locations on flat ground with no vegetation cover. Secondly, I collected 100g of soil in 3 different locations under a bush. Thirdly, I poured 2L of water on the bush with a watering can slowly and evenly to make sure the water drops are small as possible. I waited for 20 minutes. Then I collected 100g of soil in 3 different locations under a bush. I put the soil samples in a baking pan in each hole. After that, I baked soil samples at 100-105°C for 24h. Then, I weighed the soil sample again and record the mass. I subtracted the mass of dried soil sample after watering from the mass of dried soil sample after before, I recorded and compared data. In the end, I repeated the above for all 5 bushes, 3 times each day for 3 days.

However, there are few sources of error, including the unevenness of pouring water caused by human error, other factors in the nature such as distractions from previous rain and other organisms helping in the process of controlling water flow. These small errors still could not deny the result I got. The result was clear and straightforward that Buxus microphylla intercepted most water while Euonymus japonicas intercepted the least.

Overall, my experiment had well answered my questions and led to my conclusion Buxus microphylla had the best canopy rainwater interception ability. My hypothesis was correct. Proper vegetation can be a contributing factor to reducing environmental damage to cities and lives.

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