Part 1 - Above Ground Interactions, Light, Photosynthesis, and Carbon Allocation

Part 1 - Above Ground Interactions, Light, Photosynthesis, and Carbon Allocation

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Unformatted text preview: Trees and Forests Trees and Forests Lecture 6: Aboveground Interactions: Lecture 6: Aboveground Interactions: light, photosynthesis and carbon light, photosynthesis and carbon allocation allocation Outline Outline I. Photosynthesis introduction II. Light-3 types of light; PAR; sunflecks; LAI and the understory light environment I. Net photosynthesis and respiration-Construction vs. maintenance respiration; environmental effects on net photosynthesis IV. Leaves and leaf adaptations-Compromise between carbon gain, temperature and water loss; sun vs. shade leaves; evergreen vs. deciduous leaves V. Carbon allocation-Tradeoff between growth and reproduction; above vs. Trees must photosynthesize to provide fixed carbon for all activities 1)Growth 2)Reproduction 3)Water and nutrient acquisition 4)Tissue maintenance Fixed carbon is the currency of plant fitness! I. Photosynthesis introduction I. Photosynthesis introduction Photosynthesis Photosynthesis CO 2 + H 2 O carbohydrate + O 2 sunlight Requires input of energy in the form of sunlight! Tree canopies absorb photosynthetically active radiation ( PAR ), via chlorophyll and accessory pigments Light quality is an important factor in forest photosynthesis red blue green II. LIGHT II. LIGHT 3 types of light in 3 types of light in forests forests: 1) Direct sunlight 2) Diffuse light 3) Filtered light Diffuse light = Direct light that is scattered by tree trunks, moisture or particles in the atmosphere Filtered light = Filtered through the leafy canopy. Which has more PAR? sunfleck : Short period of direct sunlight on forest floor as sun passes over a canopy opening can be very brief (30 sec.- 10 minutes) but still important for forest photosynthesis! May account for 50% of annual PAR on forest floor Light in forest understories: Importance of Light in forest understories: Importance of sunflecks sunflecks Forest Canopies are Multi-layered Forest Canopies are Multi-layered Species that occupy different canopy horizons experience very different light environments Light decreases with depth in canopy and increasing leaf area index (LAI) LAI= Area of leaves per area of forest floor (m 2 /m 2 ) Leaf area index (LAI) is a useful general indicator of forest productivity Green tissue, mostly leaves, absorb Green tissue, mostly leaves, absorb light light C fixed C fixed...
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Part 1 - Above Ground Interactions, Light, Photosynthesis, and Carbon Allocation

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