Comparison of Spatially and Nonspatially Explicit Nonlinear Mixed Effects Models for Norway Spruce Individual Tree Growth under Single-Tree Selection

Background and Objectives: Continuous cover forestry is of increasing importance, but operational forest growth models are still lacking. The debate is especially open if more complex spatial approaches would provide a worthwhile increase in accuracy. Our objective was to compare a nonspatial versus a spatial approach for individual Norway spruce tree growth models under single-tree selection cutting. Materials and Methods: We calibrated nonlinear mixed models using data from a long-term experiment in Finland (20 stands with 3538 individual trees for 10,238 growth measurements). We compared the use of nonspatial versus spatial predictors to describe the competitive pressure and its release after cutting. The models were compared in terms of Akaike Information Criteria (AIC), root mean square error (RMSE), and mean absolute bias (MAB), both with the training data and after cross-validation with a leave-one-out method at stand level. Results: Even though the spatial model had a lower AIC than the nonspatial model, RMSE and MAB of the two models were similar. Both models tended to underpredict growth for the highest observed values when the tree-level random effects were not used. After cross-validation, the aggregated predictions at stand level well represented the observations in both models. For most of the predictors, the use of values based on trees’ height rather than trees’ diameter improved the fit. After single-tree selection cutting, trees had a growth boost both in the first and second five-year period after cutting, however, with different predicted intensity in the two models. Conclusions: Under the research framework here considered, the spatial modeling approach was not more accurate than the nonspatial one. Regarding the single-tree selection cutting, an intervention regime spaced no more than 15 years apart seems necessary to sustain the individual tree growth. However, the model’s fixed effect parts were not able to capture the high growth of the few fastest-growing trees, and a proper estimation of site potential is needed for uneven-aged stands.

Scots pine (Pinus sylvestris L.) cultivation in Republic of Tatarstan

The state of coniferous-deciduous forests in the region of the subtaiga forests in Tatarstan directly depends on the prospects for preserving pines in the composition of these forests that is why the artificial forest regeneration and increasing the sustainability of Scots pine (Pinus sylvestris L.) becomes relevant. It is proposed to take measures for the formation of nominally primary forests, including those of artificial origin, based on pine forests, planted over a large area for several decades. Attention is drawn to the massive decrease in the density of stands in pine forests of artificial origin after they reach the age of 40...60 years. There is a complete death of pine crops or their degradation with a significant decrease in the density of forest stands. Analysis of the course of growth of pine crops reveals a sharp drop in volume growth rates at 20...30 years of age. A decrease in volume growth rates is recorded not only in Tatarstan, but also in a number of other regions located mainly in the zone of coniferous-deciduous forests. It is proposed to consider a sharp drop in volume growth rates as a sign of weakening of these stands, which may be associated not only with the onset of the age of natural maturity, but also with the aggravation of competitive relationships within forest communities. It is recommended to practice intensive artificial selection in pine plantations, for this purpose selection cutting of forests "according to state" in order to reproduce and preserve forests.

How the Virtual Thinning Can Help to Control the Changing of Genetic Structure in Scots Pine Stands?

The work detailed here in the context of the above project sought to determine changes in the gene pool (at the DNA level) in a stand of Scots pine (Pinus sylvestris L.), under the influence of various kinds of forest-tending cuts. The experimental area on which the research was focused is located in Poland’s Ostrów Mazowiecka Forest District. Genetic structure was specified using five nuclear SSR sequences and six chloroplast SSR loci, while the five thinning variants trialled were sanitation cutting, low thinning of 30% intensity, schematic thinning, selective thinning and destructive lumbering. The control variant was left untreated. It was virtual rather than real-life thinning that was pursued, using the ForestSimulator BWINPro program. Changes in the structure of the stand after a further 10 years were also simulated. The different thinning variants were shown to cause change in the gene pool and level of genetic diversity of trees in the study area. In terms of maintaining genetic variability in the stand, the least-favourable method proved to be thinning from below. Destructive selection cutting was in turn most beneficial in terms of the preservation of genetic structure, with the reduction in rare alleles being more limited than in any other analysed variant. It was with the selective thinning variant that the final number of trees, stand structure and level of genetic variation resembled the situation in the control most closely. This suggests that selective thinning provides for a rather accurate replication of processes occurring in nature.

STRUCTURAL AND DYNAMIC CHANGES IN MIXED FORESTS OF BEECH AND FIR ON MT. GOČ

The primary goal of this research was to analyze the structural, production and dynamic changes of theforests of beech and fir in permanent sample plots of Mt. Goč, excluded from regular management fora period of 35 years (1977–2011). The established principles of spontaneous development and selfregulatoryprocesses could have implications on the regular management in these forests located in thearea of Mt. Goč and other areas.The results of this research in the permanent sample plots indicate that the mixed forests of beech andfir have suffered a number of changes in terms of structure and production in the investigated period.Structural disruptions have been the result of a decrease in the share of small and medium-diametertrees, as well as an increase in the share of trees of large dimensions in the total number of trees. Thecurves of distribution have been moved to the right and in terms of shape they differ from the lines thatare typical of selection forests. A relatively large number of trees per hectare and the described distributionby diameter classes have resulted in the high values of basal area and stand volume. In addition,a high volume increment has also been recorded. The quality and incremental capacity of the standshave been reduced due to a significant share of old beech and fir trees. The accumulation of volumeslowed down the dynamics of stand development and hindered rejuvenation and recruitment, as thenecessary prerequisites for structural stability and functionality in selection forests.The observed trends of development in these forests in the sample plots clearly indicate that a structurallystable, socio-economically and ecologically valuable selection forest is possible to achieve only withan active and continuous implementation of a set of management procedures, which primarily refersto selection cutting. Self-regulatory processes that are allowed over time, as in the case of the analyzedsample plots, are increasingly distancing us from this goal.

Logging damage to residual trees during sustainable harvesting of uneven-age stands in the Hyrcanian forests of Iran

Background: The frequency of wounded trees and intensity of wounds during logging operations can have serious impacts on stand growth and forest sustainability. The aims of the study were to evaluate and compare stand (tree and regeneration) damage level, wound characteristics, and damage types occurring when using a cable skidder in salvage logging and selection cutting. Methods: This study was conducted on four sites of mixed uneven-aged hardwood stands in the Hyrcanian forests of Iran. At two sites, salvage logging was applied (SL1 and SL2), and low-intensity selection cutting (SC1 and SC2) was applied at the other two. A systematic plot sampling design was used on the study area for damage assessment. Results: The percentage of regenerating trees damaged was 2.8, 2.1, 4.3, 1.4 %, in SL1, SL2, SC1, and SC2, respectively. The corresponding percentage of damaged trees was 4.3, 3.7, 4.9, 1.7 %. Most of the damage (48–79%) to the stand occurred during the winching stage at all the sites. Most of the wounds were located on the bole (51–78%). The average wound height and wound size at selection cutting sites were significantly higher than at the salvage logging sites. The incidence of high-intensity wounds at the salvage logging sites (55% at SL1 and 57% at SL2) was higher than at the selection cutting sites (24% in SC1 and 30% in SC2). Regenerating beech (Fagus orienalis Lipsky) and alder (Alnus subcordata C.A.Mey) had the highest incidence of damage. The number of damaged trees increased with increasing winching distance. Conclusion: Damage levels in stands during salvage logging and low-intensity selection cutting are lower (about a quarter) than the damage level to residual trees (12–23%) and regeneration (5–11%) from conventional selection cutting in uneven-aged mixed hardwood stands in the Hyrcanian forests. Because of the ecological and conservation value of deadwood, if the incidence of wind-fallen trees is low, the wood should be left in forest stands due to the high cost of salvage logging and the damage caused to residual and regenerating trees.

Harvesting System Suitability as Decision Support in Selection Cutting Forest Management in Northwest Bosnia and Herzegovina

Planning of forest harvesting operations is one of the key elements of successful forest management. The integration of modern tools and traditional forestry procedures is something that must be done in contemporary forestry. This research investigated the use of multicriteria decision support (AHP) and GIS in choosing the optimal harvesting system for predominantly selection cutting forest management on the example of two Forest Management Units (FMU). Results showed that AHP could be easily integrated into GIS using the extAHP tool and its results could be of help, along with other input data, in choosing the optimal harvesting system. Spatial analysis of raster data in GIS gives a comprehensive insight into the stand and terrain characteristics and shows the relative share of the area proposed for each system. In FMU »Kozara–Mlječanica«, the harvesting system chainsaw-skidder had the highest relative share with 44% of the area, meaning that it is almost the only harvesting system in current use, followed by chainsaw-forwarder (36%), chainsaw-cable yarder (19%), and chainsaw-adapted agriculture tractor (AAT) (1%). The system harvester-forwarder was not used at all, which is understandable considering that FMU »Kozara–Mlječanica« has a higher average slope and higher diameter of trees to be cut than FMU »Prosara«, where harvester-forwarder system accounts for a significant 36% of the area. The dominant system in FMU »Prosara« was chainsaw-forwarder (42%), followed by chainsaw-cable yarder (17%), chainsaw-skidder (4%) and chainsaw-AAT (1%). It should be noted that the presence of chainsaw-skidder system is insignificant. It is replaced by the system chainsaw-forwarder. Traditional harvesting system chainsaw-skidder, which prevails in Bosnia and Herzegovina, should be upgraded with the new technologies and methods. Using tools like multicriteria decision support and GIS could be of great help in that process.