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Occurrence, morphology and growth of understory saplings in Swedish forests

Wikberg, Per-Erik (2004). Occurrence, morphology and growth of understory saplings in Swedish forests. Diss. (sammanfattning/summary) Umeå : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae. Silvestria, 1401-6230 ; 322
ISBN 91-576-6706-3
[Doctoral thesis]

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Growing demands for a multipurpose forestry leads to increased use of silvicultural systems that avoid clear-cutting. Regeneration in such systems is based on establishment and ingrowth of new seedlings under a more or less closed canopy. At long-term forestry planning reliable ingrowth models are needed to predict the future wood production. The objectives of this thesis were to review the field of ingrowth in established stands, to develop a model for prediction of ingrowth for the planning system Heureka and to deepen the insight in the ingrowth process by a case study. The ingrowth model consisted of four parts, describing: Probability for occurrence of saplings (1-39 mm diameter at breast height (DBH)) on plots with r = 5 m. Number of saplings on stocked plots (plots with saplings of target species). Probability for ingrowth of a sapling over 39 mm DBH during a 5-year period. Diameter of ingrown trees at the end of the 5-year period. The model was based on data from permanent plots at the National Forest Inventory. Separate functions were developed for seven species and species groups. Picea abies saplings had the widest distribution and occurred on 58 % of 12 469 representative plots in established forests. Betula spp. saplings occurred on 50 % of the plots, while the occurrence of saplings of other species was less than 20 %. Sapling density on stocked plots was highest for Betula spp, in average 10 per plot. Average ingrowth rate was 14.6 stems per ha and year, and P. abies made up more than half of this. The ingrowth varied according to the different functions with age, density and species composition of the stand and the moisture and fertility of the site. Growth and morphology of young conifers was examined in a species experiment on a clearcut and in shelterwoods of three different densities (41 – 124 stems per hectare). The largest intra-specific differences between clearcut and shelterwood were found for Pinus spp, while moderate differences were found for Picea spp. For Pinus spp, stem height and diameter decreased, while the stem slenderness increased with increasing shelterwood density. Moreover, the number of branches per whorl and the crown ratio decreased with increasing shelterwood density. The proportion of biomass in roots, stem, branches and needles was analysed as a function of estimated irradiance transmission for each individual. The proportion of stem decreased and the proportion of branches increased with increasing irradiance for Pinus spp. No significant trends were found for Picea spp.

Authors/Creators:Wikberg, Per-Erik
Title:Occurrence, morphology and growth of understory saplings in Swedish forests
Series Name/Journal:Acta Universitatis Agriculturae Sueciae. Silvestria
Year of publishing :September 2004
Number of Pages:25
ALLI. Wikberg, P-E., Elfving, B. and Kempe, G. Modelling understory sapling density and distribution in Swedish forests. Manuscript. II. Wikberg, P-E. and Elfving, B. Modelling ingrowth of saplings into the tree layer in Swedish forests. Manuscript III. Wikberg, P-E., Elfving, B., Lundmark, T. Ottosson-Löfvenius, M. and Rosvall, O. Biomass growth and allocation patterns among planted conifer saplings in varying overstory densities. Manuscript.
Place of Publication:Umeå
ISBN for printed version:91-576-6706-3
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:F Plant production > F50 Plant structure
F Plant production > F62 Plant physiology - Growth and development
Subjects:Not in use, please see Agris categories
Agrovoc terms:forest plantations, betula, picea, pinus, undergrowth, models, growth, plant anatomy
Keywords:understory sapling, advance growth, recruitment, ingrowth, model, logistic regression, biomass allocation, growth, morphology, irradiance
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ID Code:610
Department:(S) > Institutionen för skogsskötsel
Deposited By: Staff Epsilon
Deposited On:02 Sep 2004 00:00
Metadata Last Modified:02 Dec 2014 10:06

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