Uneven-aged Norway Spruce Research Articles

Evaluating thinning strategies using a tree distance dependent growth model: some examples based on the CAPSIS software “uneven-aged spruce forests” module

This work evaluated thinning strategies in uneven-aged Norway spruce forest stands using a tree distance dependant growth model. The model is based on competition for light between trees demonstrated through interception of light rays by individual crowns. It was adapted to mountain settings by analyzing the effect of slope and aspect on light distribution. Growth functions were built by empirically comparing height and diameter increments with age and light availability. A maximum number of new trees set by the user was added each year and mortality, i.e. disappearance of trees not receiving enough light to survive was also included. The model is part of the CAPSIS software package which provides a user-friendly interface for silvicultural simulations. First, thinning typical of current practices in uneven-aged Norway spruce stands in the northern French Alps was simulated. This thinning appeared to be neutral in terms of wood production and beneficial but not dynamic enough in terms of stand renewal. In a second experiment, we compared group selection to individual selection in a virtual two-layered stand organized into clumps. This showed that individual selection favors the growth of the largest trees in the stand while group selection favors the growth of the smaller ones as well as regeneration. In a third simulation, we generated a strategy to convert an even-aged stand into an uneven one. Success appeared to be linked to a flexible approach alternating high and low intensity cuttings, group and individual selection.

Spatial autocorrelation of allozyme traits in a Norway spruce (Piceaabies) population

Using isoenzymes as gene markers and spatial autocorrelation analysis as a tool to detect spatial patterns, we studied the spatial distribution of genotypes in a naturally regenerated uneven-aged Norway spruce (Piceaabies (L.) Karst.) stand on the eastern Italian Alps. In most cases we found a random distribution of genotypes in space; in the whole data set less than 11% of genotype pairs showed positive associations for the first (10 m) distance class. Extensive gene flow, due to long distance dispersal of pollen and seeds in P. abies, may account for the observed spatial patterns. A few genotypes (GotB-22, LapB-23, LapB-24, SkdB-12, and MnrB-12) showed a significant clumped distribution over a small spatial scale. We suggested that selection processes driven by environmental variability might have produced significant clumping of these genotypes. However, the role of factors linked to the breeding system, and of chance events, in determining the population spatial structure cannot be excluded in our study.

Simulation of Sapling Population Dynamics in Uneven-aged Picea abies Forests

A series of mathematical equations describing the interrelationships between sapling recruitment, growth and mortality, and the density and ingrowth of saplings into the tree layer are presented. Assuming that average annual sapling recruitment, growth and mortality are constant over time, sapling density in a specified size class as well as ingrowth into the tree layer can be described as a geometric series of sapling recruitment. Sapling density and growth are readily measured, but not sapling recruitment and mortality. These processes can be estimated though. With no mortality the sum of the annual height increments in two adjacent size classes should be equal. With mortality among saplings, the sum should decrease over the size range. An equation for theoretical estimation of sapling mortality from the slope of decrease is suggested. With mortality known, sapling recruitment can also be estimated. To see how temporal changes in recruitment, growth and mortality affect sapling density and ingrowth into the tree layer over time, simulations were performed. For this a hypothetical sapling stand was constructed, based on data from permanent plots in central Sweden managed with single-tree selection. The simulations clearly demonstrated that sapling density by itself renders little information about the regeneration dynamics and cannot by itself be used to estimate ingrowth into the tree stratum. With annual mortality rates below 5% sapling growth had a large influence on both sapling density and ingrowth into the tree stratum. The equations suggested for estimating mortality and ingrowth gave reasonably accurate estimates. Results of the simulations are discussed with reference to recent studies of the stand dynamics of uneven-aged Norway spruce forests.

Alpine-forest selection - an alternative to clear-cutting in uneven-aged Norway spruce (Picea abies (L.) Karst) forest?

Alpine-forest selection - an alternative to clear-cutting in uneven-aged Norway spruce (Picea abies (L.) Karst) forest?