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Silvi (Subject) / general (single-storied) (Lesson)
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- How describe single-storied forest stands (mix of different variables)? First Group (for mean values): Age, Species, Diameter, Height Second Group (describing whole stand): No. of trees, basal area, volume, biomas Third Group (describing the site and its volume): Vol. growth, site productivity
- A fundamental variable in forestry is the stem volume. How is it calculated? Volume = basal area * height * form factor form factor: calculating the volume of a cylinder and devide it by 3 would be the volume of a cone. the actual tree is something between a cylinder and a cone, form factor.
- What is the form height? What are its purposes? Also purposes on stand level. height * form factor (always top height!) it is more stable over time, compared to just the form factor (which changes with older and denser stands). it is not linear: shape height to top height! on level: volume / ha = basal area * form height (useful for rough estimation of volume in stand)
- Development over time: What is difference between 'height curves' and 'height development curves'? What are the characteristics? - height curve: height over diameter, almost asymptotic, more divers in younger stands and less the older they get. - height development curve: height over age, to estimate site index.
- Eichhorns law? Characteristics? Brutto-Ertrag/gross production over top height, in all stands the same proportions [gross prod. = H (dominant trees)], even though a more fertil site reach top height earlier, useful in growth studies.
- What effects the speed of growth and increment development? - site index - density (spacing, stem numbers)
- Needle mass: characteristics? Culmination? Connections to growth? All densities reach roughly the same total needle mass. But it is reached earlier for denser stands. And more fertile sites have a higher amount of needle mass (which probably explains why there is more growth on fertil sites). After culmination the needle mass remains constant. The needles drive growth but there is no clear connection to stem volume increment!
- Thinning and stand development: self-thinning rule (general) Upper limit on how many individuums are in a certain space, this is influenced by the size. Because of that a certain line can be established which can be seen as the upper limit.
- What is influenced by thinnings? influenced: - diameter - thicker trees and branches (development of longer ones), wider and longer crown (lower branches are not killed of!) - volume (increment) - thinnings reduce self-thinning (mortality) - and by that you actual increase the living volume the same time - that also means the total production (living and dead wood) is decreased (never increased) by the thinning BUT the harvested volume is increased considerably. - thinning influences CAI and MAI (it prolongs the rotation period) --> you do not get higher trees from a thinning but thicker!
- What is effected by the strength of a thinning? - light or heavy thinning. the harder one thins the stand the longer the rotation. Direct influence on CAI and MAI - this effect is even more considerable with thinning from above (even longer rotation) PLUS thinning from above creates lower and thinner stands
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- When does CAI culminate? When MAI? CAI: after 30-50y., drops slowly afterwards MAI: often far beyond 100y. of age.
- Wind and trees. Wind influences the shape of trees, it may also influence the diameter. Trees are like single antennas, ea. of which taking up the wind-energy. If a stand loses trees, other trees have to take up the higher energy.
- Fertilisation. Influenced by F.? --> you get more needles! - diameter increases - denser crowns (because more needles and (first) no longer or wider crown) - volume increases