Kobra Maleki
Forsker
(+47) 465 06 548
kobra.maleki@nibio.no
Sted
Steinkjer
Besøksadresse
Innocamp Steinkjer, Skolegata 22, Bygg P 1. etasje, 7713 Steinkjer
Sammendrag
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Sammendrag
Management of Scots pine (Pinus sylvestris L.) in Norway requires a forest growth and yield model suitable for describing stand dynamics of even-aged forests under contemporary climatic conditions with and without the effects of silvicultural thinning. A system of equations forming such a stand-level growth and yield model fitted to long-term experimental data is presented here. The growth and yield model consists of component equations for (i) dominant height, (ii) stem density (number of stems per hectare), (iii) total basal area, (iv) and total stem volume fitted simultaneously using seemingly unrelated regression. The component equations for stem density, basal area, and volume include a thinning modifier to forecast stand dynamics in thinned stands. It was shown that thinning significantly increased basal area and volume growth while reducing competition related mortality. No significant effect of thinning was found on dominant height. Model examination by means of various fit statistics indicated no obvious bias and improvement in prediction accuracy in comparison to existing models in general. An application of the developed stand-level model comparing different management scenarios exhibited plausible long-term behavior and we propose this is therefore suitable for national deployment.
Sammendrag
Stand-level growth and yield models are important tools that support forest managers and policymakers. We used recent data from the Norwegian National Forest Inventory to develop stand-level models, with components for dominant height, survival (number of survived trees), ingrowth (number of recruited trees), basal area, and total volume, that can predict long-term stand dynamics (i.e. 150 years) for the main species in Norway, namely Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.), and birch (Betula pubescens Ehrh. and Betula pendula Roth). The data used represent the structurally heterogeneous forests found throughout Norway with a wide range of ages, tree size mixtures, and management intensities. This represents an important alternative to the use of dedicated and closely monitored long-term experiments established in single species even-aged forests for the purpose of building these stand-level models. Model examination by means of various fit statistics indicated that the models were unbiased, performed well within the data range and extrapolated to biologically plausible patterns. The proposed models have great potential to form the foundation for more sophisticated models, in which the influence of other factors such as natural disturbances, stand structure including species mixtures, and management practices can be included.
Sammendrag
In the last century, local or individual-based forest management was introduced by various forest scientists including Schädelin, Abetz and Pollanschütz as an alternative to traditional global thinning methods. They suggested breaking large forest stands down into smaller neighbourhood-based units. The centre of each of these neighbourhood-based units is a frame tree (also referred to as final crop tree, elite tree or target tree) with clearly defined properties that depend on the management objectives. In each management intervention, trees in the neighbourhood of frame trees that in the next 5–10 years are likely to influence the frame trees negatively are removed selectively. In contrast to global methods, management is only carried out where there are frame trees. Local or individual-based forest management methods were first introduced in a commercial forestry context, but rather constitute generic methods that can be efficiently applied in management for conservation, carbon sequestration and recreation. They are also often applied in the context of continuous cover forestry (CCF). In this study, we analysed the behaviour of test persons selecting frame trees in 26 training sites, so-called marteloscopes, from all over Great Britain. Although the test persons were new to individual-based management, statistical performance indicators suggested that frame trees were selected in accordance with the theory of local or individual-based forest management. Unexpectedly the test persons even achieved a comparatively high degree of agreement. This result contrasts the low agreement and partly unsatisfying performance indicators incurred in the selection of frame-tree competitors, the second step of local forest management. The outcomes of this study highlight that training in individual-based forest management needs to put more emphasis on the identification of frame-tree competitors.