Stem Exclusion. Objectives 1.Understand the patterns and processes within the stem exclusion stage 2.Understand when processes of crown closure and self-thinning.
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Stem Exclusion
Objectives
1. Understand the patterns and processes within the stem exclusion stage
2. Understand when processes of crown closure and self-thinning occur
3. Understand difference between stratification and differentiation
4. Understand relationship behind these biological processes and stand tending operations
Stem Exclusion
• Number of trees goes down
• Live crown ratio goes down
Crown Closure
• Early in dense stands
• Later in less dense stands
Self-thinning
• Does not occur at crown closure
• Still adequate growing space per tree for growth
• No available growing space
Stratification
• Separation into layers (strata)
• Separation is by species or cohort
Differentiation
• Separation within stratum by vigor
– Dominant
– Co-dominant
– Intermediate
– Suppressed
Differentiation
• Slightly older
• Better microsite
• Less competition
– Other vegetation
– Wider spacing
• Genetically superior
Stem
• Reflection of history
• Accumulation of growth
Tending
• Speeds up natural process
• Directs growth onto certain trees
• Reallocates growth within tree
• Increases total growing space
Self-thinning
• Growing space is limited
• Repartitioning of growing space
• Trees must get bigger to live
Fixed amount of growing space
• Large number of small things
• Small number of big things
• Small number of small things – space left over
Concept
Size
number
X
X
Concept
Size
number
Concept
Size
number
X
Concept
Size
number
X
Concept
Size
number
Concept
Ln
(size)
number Ln (number)
Relative density
• Number of trees / maximum number– Of that size
Concept
Size
numberX Y
RDI = x/y
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