Where Do Trees Get Their Mass?
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- Common Misconception About Tree GrowthInitial QuestionWhere do trees get the matter to grow into some of the biggest organisms on the planet?Popular Beliefs• Trees get rich nutrients from the ground • Soil or air provides the starting material • Roots digging into soil must be taking something from it • Trees look and feel solid like dirtLogical ChallengeIf trees are taking mass from the soil, why isn't there a big hole around the tree where soil has been removed?Initial BeliefIt's intuitive to believe trees get most of their mass from the soil due to visible root systems.
- Van Helmholt's ExperimentExperiment DesignIn the early 1600s, scientist Johann Baptist Van Helmholt carefully measured soil in a pot, planted a tree, and cared for it for five years while ensuring no soil was added or removed.Surprising ResultThe tree weighed 72 kilograms, but the soil mass had only decreased by about 60 grams.Key FindingStrong evidence that the mass of a tree does not come from the soil.Initial ConclusionVan Helmholt concluded the tree was made entirely of water, which while incorrect, showed that tree matter doesn't come from the soil.
- Exploring Alternative SourcesWater and Nutrients• Trees absorb water and nutrients from soil • Water is essentially all trees eat • Seeds, soil, and water combine to make a big treeEnergy QuestionPeople speculate about whether the sun converts energy into mass or if there's something else involved in creating new matter.Ingredient Discussion• Sunlight is needed for trees to grow • Trees wouldn't grow without sunshine • Oxygen is mentioned as a necessary gasMissing PieceThere's acknowledgment that air contains a gas trees need, hinting at something beyond soil and water.
- The Carbon Dioxide RevelationThe Key Ingredient95% of a tree's mass actually comes from carbon dioxide that trees take in from the air.Trees Are AirTrees are largely made up of air, specifically the carbon dioxide they absorb through their leaves and processes.Breathing Cycle• Humans breathe out carbon dioxide and water, losing mass in the process • Trees breathe in the exact same substances to gain mass • This is the inverse relationship between human and tree respirationClosed SystemIn a closed system with just a person and a tree, the person would get smaller while the tree gets bigger, as the person's exhaled carbon dioxide becomes the tree's mass.
