PP2: Frameworks of terrestrial ecology: species adaptations and tolerance

Chaos in the woods

• lots of chaotic things going on in the woods, but we can find order if we have a standard with which to compare

• vegetation is constantly changing- succession, management, storms, fires, climate change, etc.

• a more geographic approach gives us one thing to hold onto

What does establishment mean

• establishment means that plants have germinated and survived

• establishment is a key ecosystem process, as is growth and maintenance, and reproduction

• many plants can live on many more sites than they occur, if they could only get established

Competition

• competition is a direct factor determining occurrence of trees in an area within the context of the site

• competition= relationship of two non-symbiotic species with each other capable of occupying the same geographic space

• competition = sum of the processes by which the yield of biomass is reduced

• “open site” = low competition = many species can exist

For a plant to occur in an ecosystem:

1. Establishment on the site (may take 2-5 years to occur)

2. growth and maintenance in the face of competition

3. reproduction via sexual maturity or asexual reproduction

Understory tolerance

• understory tolerance= the relative capacity of a plant to survive and grow in the understory of a forest

• survival of a plant in the understory is the most critical part of its life

• light is the most important factor, but also moisture, humidity, temperature, and fungi

• shade tolerance doesnt apply to plants that NEED shade to survive and will burn up without it

Understory tolerance chart

• Release means if you cut down the trees shading/blocking them, what happens? ​

• Tolerant trees have dense crowns because the leaves on the inside can survive with less lights​

• Natural pruning: branches in the shade fall off​

• Biomass: how dense they're growing/spread out​

• Mesic: moisture avilable throughout the growing season​

Caveats to understory tolerance

• wood strength or rooting depth are not related to tolerance

• best strategy is min-tolerant: can tolerate shade but also quickly release

• juvenile plants are more tolerant than adults

• suckers are more tolerant than seedlings

  • Suckers=sprouts, suckers have a more established root system ​

• tolerance may change with moisture/nutrient availability

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Photosynthesis and amount of light

• quantity and quality of light reaching the surface of the earth is what controls plant growth and ecology

• light is used by plants to produce sugars and carbohydrates in the process of photosynthesis

• CO2 is uptaken from the atmosphere into the leaves through the stomates

• once in the plant, CO2 reacts with water to produce a 6-carbon sugar and a byproduct (sugar)

• Xylum: water from roots to canopy​

• Phloem: sugars from canopy to roots

• At the same time as photosynthesis, plants undergo respiration in all living plant cells, day and night

• respiration uses energy gained for maintenance and construction within the plant​

Tolerant species have a _____ compensation point than intolerant plants, and saturate at lower levels of light

lower

Forest understories differ in the amount of full sunlight they recieve:

• tropical rainforest: 0.25-2%

• beech/sugar maple: 0.4-2%

• oak/hickory: 3-5%

• pine forest: 10-25%

• as expected, specific ecosystems have more/less tolerant species in their understories (B/SM = many, pine = less)