Overview
This lecture highlights the importance of trees, explores unique tree species and their histories, and discusses tree preservation efforts worldwide, including the #TeamTrees initiative to plant 20 million trees.
Trees and Their Importance
- Trees provide oxygen, cool urban areas through shade, and prevent soil erosion.
- The #TeamTrees campaign aims to plant 20 million trees via $1 donations, with each dollar funding one tree.
Avocado Trees: Survival and Evolution
- Avocados co-evolved with extinct megafauna that dispersed their seeds through digestion.
- After the extinction of these animals, humans domesticated and cultivated avocados, ensuring their survival.
- Avocados are nutritionally distinct, containing less sugar and more fat and protein than most fruits.
- The large seed helps young trees survive in low-light environments.
The American Chestnut and Restoration Efforts
- The American chestnut was decimated by an Asian fungus (chestnut blight) in the early 20th century.
- The fungus arrived via imported resistant Japanese chestnut trees.
- Breeding programs for natural resistance have had limited success.
- Genetically modified chestnuts with a wheat gene for oxalate oxidase show full resistance but await government approval for widespread planting.
- Concerns exist about ecological impacts of reintroducing GM chestnuts.
The Dancing/Crooked Forests Mystery
- The Dancing Forest in Kaliningrad and the Crooked Forest in Poland feature trees with unusual twisted shapes.
- The causes are unknown, with theories ranging from wind, soil, human intervention, or animal activity.
- Tree shaping (through pressure and phototropism) can permanently alter growth patterns.
Why Leaves Change Color in Autumn
- Deciduous trees (those that shed leaves yearly) reduce photosynthesis in winter.
- Chlorophyll breaks down in fall, revealing carotenoid (yellow/orange) and anthocyanin (red/purple) pigments.
- Trees form a separation layer to drop leaves, conserving resources until spring.
The Oldest Trees on Earth
- The oldest individual tree is a bristlecone pine (over 5,000 years old) in California, thriving in harsh environments.
- Pando, a clonal colony of quaking aspen in Utah, is at least 80,000 years old, with all stems connected by a single root system.
- Trees’ longevity can be due to harsh growing conditions, reduced competition, and unique reproductive strategies.
Key Terms & Definitions
- Megafauna — large prehistoric animals that helped disperse seeds of certain plants.
- Deciduous — trees or plants that shed their leaves annually.
- Phototropism — plant growth in response to light direction.
- Clonal colony — a group of genetically identical individuals from a single ancestor, sharing a root system.
- Oxalate oxidase — enzyme that breaks down oxalic acid, increasing plant disease resistance.
- Transgenic — an organism that has genes from another species via genetic engineering.
Action Items / Next Steps
- Consider donating to #TeamTrees at teamtrees.org; each dollar plants a tree.
- Review key tree species (avocado, American chestnut, bristlecone pine, quaking aspen) for further study.
- Reflect on the ecological roles and preservation methods of diverse tree species.