NR 326 Lecture 6 Succession

PAI : Periodic Annual IncrementAverage increment per year over a 5 or 10 year period Xem nội dung đầy đủ tại: https://123doc.org/document/4463810-nr-326-lecture-7-growth-and-yield.htm

Succession  The gradual supplanting of one community of plants by another  Accompanied by changes in stand structure and species composition Forest succession process Evolution Degradation Grass Pioneer tree species Seral tree species (increasing in tolerance (very intolerant as replacement continues) Climax tree species (very tolerant) Succession Changing in forest structure Succession Changing in species composition Succession Changing in forest ecology Primary Succession where the conditions are originally unfavorable for plant growth, such as bare rock Gradual erosion and deposition in the area allows early (hardy) pioneer species to colonize and survive Secondary Succession Occurs after existing vegetation is removed such as after a flood, fire or mechanical process (agricultural) The soil is already fertile or/and the seed was already in the soil, so plants can easily become established Stand development stages Stand initiation stage Stand initiation stage       Follows major disturbances (wind, fire, clear-cut) Regeneration of open space from seed, sprouts & advance regeneration Pioneer species occupy One cohort or age class High density Stage ends when canopy becomes continuous and trees begin to compete with each other for light and canopy space 10 Impact of Succession on Forest Management Heavy cuts Light Light selection selection VS cuts cuts Great disturbance to the Small disturbance to the natural natural 21 Impact of Succession on Forest Management If you are hoping to regenerate certain species naturally following a harvest, it is important to know what successional stage these species typically occupy; and, what type of harvest will generate the desired conditions for stand establishment (Jeff Martin and Tom Gower, 1996) 22 Impact of Succession on Forest Management Early stages Later stages High percentage of leaf High percentage of woody tissue tissue (branches, twigs and stems) Decomposed process Fast Slow Nutrient concentration Great nutrient concentration Poor nutrient concentration (nutrients The litter being locked up) Water transportation Easy Difficult The growth of forests decreases as they age 23 Impact of Succession on Forest Management Reduce the rotation length Long cutting cycle Sort Sort cutting cutting VS cycle cycle 24 Impact of Succession on Forest Management Uneven-aged management (maintain a balance of healthy, vigorous trees and a smaller number of mature trees) VS 25 Impact of Succession on Forest Management Fertilizing the forest to prevent a nutrient limitation (it is not cost-effective) 26 Today’s Goals  What is ecological succession?  Why is succession important to forest managers?  How does succession influence forest management? 27 Key Concepts  Competition drives stand development  Responses to competition are  Individual tree and stand growth are  As size increases, density decreases due to limited carrying capacity 28 How we often think of succession… A B C D E Disturbance 29 Succession in a warm dry ponderosa pine ecosystem 30 But really… Succession in a warm dry ponderosa pine ecosystem 31 Aspen is often invaded by white pine—and then there are three possible trajectories No fire allows maple and hemlock to replace white pine High intensity fire and return to aspen Low-intensity surface fire maintains white pine  Multiple pathways  One possible climax community?  Disturbance at any stage  Arrested succession  Succession is influenced by disturbance:Biological legacies… 33 34 Stand development 35 ... Climax tree species (very tolerant) Succession Changing in forest structure Succession Changing in species composition Succession Changing in forest ecology Primary Succession where the conditions... Impact of Succession on Forest Management Fertilizing the forest to prevent a nutrient limitation (it is not cost-effective) 26 Today’s Goals  What is ecological succession?  Why is succession. .. Growth is slow or may be negative 19 Impact of Succession on Forest Management Accelerating succession by applied intermediate disturbance 20 Impact of Succession on Forest Management Heavy cuts