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Dendrometry, increment and biomass
Phenology – studies the flushing (bud burst), flowering, fructification and aging cycle considering the time placement during the year. The observation of external changes (phenophases) during the life cycle of the plant is done. The quantitative description of the growing process (e.g. elongation of shoots, radial increment, biomass and leaves increment etc.) is studied in the field of phenometry.
- Buds - studies the flushing and following buds evolution; the most often transition changes between several development stages (phases) during the flushing are observed, e.g. for the spruce or beech buds we can recognize 4 development stages after the dormancy stage (see Fig.).
- Vegetative - studies the volumetric changes of growing plant organs, e.g. length increment of the current-year shoots (following after branches flushing), height and radial increments of stems; measuring of leaf area changes (using LAI).
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Development stages of the Norway spruce (Picea abies [L.] Karst.) buds – above and beech tree (Fagus sylvatica L.) – below. According to Murray et al. 2000.
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Relative height (H) and radial increments of the stem (DBH) for Norway spruce trees of the 2nd age class. Trees are grown in the sparse (FS, 1800 pc.ha-1) and dense (FD, 2500 pc.ha-1) plantations. Leaf area increment is evaluated by the leaf area index (LAI; 100% = maximal seasonal increment LAI).
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Dendrometry - studies mensurational data of trees and whole stands, their correlations and methods of forest mensuration; mensurational data describe tree dimensions, forms, and volumes or its individual parts (crown, stem etc.).
The increment (growth) is defined as a change of these dendrometric parameters. The growth can be characterised as a plant volume increase during its ontogenetic evolution. Also a modification of plant fresh or dry (more frequently) biomass could be used for the quantification of its growth.
The tree biomass is usually determined on the base of stem diameter and height increments and allometric relationships. These relationships are experimentally evaluated by the detail destructive method. Total stand biomass can be distinguished between above-ground (leaves, branches and stems) and below-ground (course and fine roots).
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Instruments for biomass increment measurements. Above – mechanical dendrometer (EMS, Brno, CR) for radial increment monitoring of the stem during the vegetation season, below – altimeter (Forestor-Vertex, I. Haglöf AB, Sweden) for the measurements of stem height.
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Alometric relationship between the stem diameter at the breast height (DBH, red triangles) or tree height (H, empty blue circles) and total above-ground biomass (TB) of Norway spruce, n=34.
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Leaf area, LAI – leaf area index is an important quantitative parameter of leaf area. LAI expresses the leaf area of the tree (or stand) above the normalized unit of soil surface (area of transverse section of the crown, stand area, etc.). Because the leaves and needles don’t have always the flat shape, LAI is distinguished as: LAIp – projected LAI (projection leaf area), LAIt – total LAI (total leaf surface), LAI (half of the LAIt).
Methods of LAI estimation – direct (destructive), based on leaves sampling and determination of the specific leaf area (SLA) – i.e. the ratio between the fresh leaf area (mostly projection) and dry weight; semi-direct, which use the allometric relation between easily measured dendrometrical parameter and carried leaf area; - indirect (non-destructive, optical methods), which use the relation between the leaf density and the amount of transmitted solar radiation through the canopy, or a probability of the transmission of this radiation to the ground floor (i.e. gap-fraction).
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Instruments used for the indirect determination of LAI: LAI–2000 PCA (Li-Cor, USA), ALAI-02D (LEFR, Brno, CR), or old/ new versions of CEPTOMETER (LEFR, Brno, CR). Portable area meters (e.g. LI-3000 Li-Cor, USA), scanners and suitable software (e.g. Cernota) are used for the direct determination of LAI. |
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