Plant interactions and limitations to growth

GROWING TOGETHER

DRY SOIL DRY SOIL

DRY SOIL

MESIC SOIL MESIC SOIL

MESIC SOIL

VIRGINIA PINETULIP POPLAR

Height

Dry WetMesic

Modified from Ellenberg, 1963

Niche Theory

• Fundamental Niche

• Realized Niche

Height

Dry WetMesic

Site Sensitive / Site Insensitive

• No tree ‘likes’ a bad site• Where you see a tree is where it

reproduced and survived• Many examples of trees in the ‘wrong’

place

Communities• Mutualism

– Animals – plants- plants and animals

• Competition– Primary model for this course

• Facilitation– Focus of much current research

Mutualism

• Organisms depend on each other• Communities become a ‘reproducing’

entity• Common in animals

– Food pyramid– Plants don’t eat each other

Competition• Survival of the fittest• Gene – environment interaction• Probabilities• Ultimately natural selection

Facilitation• One plant ‘helps’ another with no

detriment to itself• Interaction must be close to selective

neutral for ‘helper’• Role of mycorrhizae

Climax theory• Historic role of ‘superorganism’

– No way for natural selection to work– Many examples showing this does not hold– Has greatly (negatively) impacted forest

management

Growth Factors• Light

• Water

• Nutrients

• Others?

Photosynthesis

• Chlorophyl in the foliage

• Chloroplasts

• Sun foliage/shade foliage

Photosynthesis

6 CO2 + 6 H2OC6H12O6 + 6 O2

SUNLIGHT

Photosynthate

C6H12O6

“Stuff”

Energy

Respiration

C6H12O6

+ O2

CO2 + H2O

(Not

balanced)

ENERGY

Light

• PAR–Photosynthetical Active Radiation

• Sun foliage/ shade foliage

• Shade tolerance

20%

LIGHT

0%

PsSun foliage

Shade foliage

20%

LIGHT

0%

PsSun foliage

Shade foliage

Shade Tolerance

Ps

Light

Shade tolerant

Shade intolerant

Water

• Input

• Soil

• Stomates

Perc

ent S

oil W

ater

Heaviness of Texture

Field Capacity Available Water

Unavailable Water

From Brady, 1974

AETPET

Precipitation

Water Input

Rainfall Consistent

Cold Hot

Stomatal Behaviour• Internal moisture stress

– Drought avoiders

– Drought endurers

Nutrients

Law of the Minimum

• Growth is limited by whatever factor is most need

Nitrogen

Potential Grow

th

Actual G

rowth

Law of Compensation

• The addition of one factor can

increase the efficiency that a tree

uses another factor

Law of Compensation

With P

Amount of N

Gro

wth

Rat

e

Rule of Efficacy• Diminishing returns

Gro

wth

Amount of “X”

Nutrient Cycling

• Availability• CEC• Weathering• Mineralization• C:N• Nutrient capital• Translocation

Nutrients

• Nitrogen fixers

• Mycorrhizae

Temperature

Growing Space• Sunlight

• Water

• Nutrients

• Physical space

• Total growing space

• Available growing space

Total growing space

• Depends on time and place

– Macro and Micro conditions

Available Growing Space

• Grow

• Regeneration

Thinned

Unthinned

LatewoodEarlywood

No Available Growing Space

• Repartition

• Competition

Priorities for Photosynthate

1. Respiration2. Foliage – Fine Roots3. {Reproduction}4. Primary Growth5. Secondary Growth – Secondary

Compounds

• Photosynthesis > Respiration ?–GROW

• Photosynthesis < Respiration ?–DIE

• Photosynthesis = Respiration ?–NOT A LONG TERM

CHOICE

Volume

• Wood formation (total volume) is:

[ (Photosynthesis-Respiration)]

- Allocation

Where Does It Go? Respiration

Increment

Dominant Tree 26% 42%

Co-dominant Tree 29% 41%

Suppressed Tree 50% 8%[ash stand in Denmark]