Forest Ecology Midterm

Based on the Study Guide

Xylem

• Transports water and dissolved nutrients

• Moves roots → leaves

Phloem

• Transports photosynthates (sugars)

• Moves leaves → roots

Cambium

• Living meristematic tissue

• Responsible for lateral (diameter) growth

• Produces xylem inward, phloem outward

Pith

• Central stem tissue

• Storage of water and carbohydrates

Primary Growth

elongation (Not diameter)

Secondary Growth

Diameter (Tree Rings)

Root Growth

• Occurs for the shortest portion of the year

Stem elongation

• Concentrated in early–mid growing season

Excurrent branching

• Strong central leader

• Conical form

• Example: Tulip poplar, Norway spruce

Deliquescent branching

• Multiple stems

• Broad, spreading crown

• Common in hardwoods

Epinastic control

• Weak epinasty → excurrent form

• Tulip poplar = weak epinastic control

Gravimorphic growth

• Branches respond to gravity

• Downward orientation = gravimorphic response

TSI

(Timber Stand Improvement)

• Thinning

• Crop tree release

Girdling

• Kills tree by interrupting phloem

• Creates snags

Snags

• Critical wildlife habitat

• Support:

  • Invertebrates

  • Cavity nesting birds

  • Denning mammals

Alpha diversity

• Species richness and evenness within one site

Beta diversity

• Comparison between sites

Gamma diversity

• Landscape-level diversity

Core Equation

Genotype + Environment = Phenotype

Why plasticity is best identified under Situation B

• Low genetic diversity

• Wide environmental variation

• Differences in phenotype are driven by environment, not genetics

This is classic phenotypic plasticity logic, not just a definition

Elevation, Latitude & Climate Relationships

• Higher elevation ≈ higher latitude (further from equator)

• Colder temperatures

• Shorter growing seasons

• Tree line driven by temperature, not elevation itself

Macronutrients

• Nitrogen

• Phosphorus

• Potassium

Soil pH

• Most forest soils are acidic, not alkaline

Growing Space

• Can decrease in cool/dry climates because:

  • Organic matter decomposes slowly

  • Nutrients tied up in forest floor

Intolerant species

- High plasticity in:

• Leaf physiology

• Elongation

Tolerant species

• Lower overall plasticity

• Stable morphology

Species dominance shifts across:

Xeric → mesic → hydric conditions

Competitive advantage depends on

site conditions, not “best species”