In this review I attempt to reveal the significance of life history and fractal organisation theory for retention forestry. The retention approach has emerged from the recognition that even intense natural disturbances leave biological legacies and spatial heterogeneity in the new forest which contrasts with the simple and homogeneous environment that is often the outcome of traditional harvesting practices. The review presents some insight into the understanding of a complex, self-organising dynamical system that supports organismal units being its branches and leaves in a tree, or a wide variety of flora and fauna in a forest. It seems that the formation of a scale-invariant structure of life cycle events may fit in the general terms of homeostasis, lifespan and fitness, so it could be argued that habitat quality and integrity of forest communities should be evaluated based on the assessment of organism-specific effects and responses in ecosystem functioning. Moreover, biological legacies defined as biologically created patterns that persist from the pre-disturbance ecosystem and influence recovery processes in the post-disturbance ecosystem should include organically derived measures of ecosystem integrity, such as habitat quality.

Keywords: life history, fractal organisation, retention forestry.

Planting is a preferred method for establishing Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.). The stock types for these species include bareroot and container plants. However, only a few long-term trials have been established to compare the performance of the different modern stock types within the large distribution range of these conifers. Our aim was to analyse how the growth and survival of P. sylvestris and P. abies was influenced by planting stock type up to eight years after planting in 12 experimental plantings established at prevailing sites for the test species in hemiboreal Estonia. Typically, container plants had better initial growth increment during the first two to three years but this difference disappeared during the latter years. The growth of P. sylvestris bareroot and container seedlings were similar while growth of P. abies container seedlings were slightly inferior compared to bareroot plants. Survival of both test species was independent of planting stock used. Overall, the similar growth performance of the two stock types suggests reforestation with container seedlings may be a preferable option, since they are produced more easily using intensive propagation methods, which will enable more convenient transportation and cause less planting stress.

Keywords: forest planting, planting stock type, Norway spruce, Scots pine.

   The current study compared disturbances caused by two types of log-skidding machines, namely a rubber-tired skidder and a crawler tractor, on clay loam soil in forest. An extensive fieldwork was carried out to find out the impact caused by the combination of both machine types, traffic intensity (5, 10, 15, and 20 skidding cycles) and skid trail slope (0-15 % and >15 %) on soil compaction and forest floor after logging. The results showed that regardless of skidder type, bulk density of soil raised as traffic intensity and slope increased while the coverage of forest floor decreased. Within each traffic treatment soil compaction intensified with increasing skid trail slope, therefore significant differences in bulk density were observed between slope 0-15 % and > 15 %. Litter mass measured on the skid trail reached 2,012 kg ha-1 at the maximum (five passes on slope with inclination of 0-15 %) and 54 kg ha^-1 at the minimum (20 passes on slope > 15 %) for rubber-tired skidder, and 2,489 kg ha^-1 at the maximum (five passes on slope 0-15 %) to 470 kg ha^-1 at the minimum (20 passes on slope > 15 %) for crawler tractor. The results showed that the number of passes and slope and skidder type had strong effects on the intensity of soil disturbance. The results suggest that the rubber-tired skidder causes soil disturbance with lower traffic intensity than the crawler tractor. The dramatic increase of soil disturbance caused by the rubber-tired skidder may be associated with higher static ground pressures.

Keywords: bulk density, forest floor, skidder type, skid trail slope, soil disturbance.

   The exposure of a tractor operator to noise does not depend solely on the noise produced by the machine, but also on the working conditions, which are constantly changing in forestry. This research was conducted with an adapted IMT 565 DV agricultural tractor in a mixed stand of beech and fir in southwestern Serbia. The results show that the structure of working time changes with increased skidding distance. When the skidding distance is increased from 150 m to 450 m, the share of empty and loaded travel grows from 38% to 50%, resulting in higher noise exposure of a tractor operator. In addition, it was estimated that an increase in the skidding distance from 50 m to 1,000 m results in a noise exposure increase of 2 dB(A). The contribution of the operations of empty and loaded travel and landing work to the total noise level exceeds 90% at 450 meters long skidding distances. However, when assessing worker exposure to noise, it is possible to disregard the major impact factors and inadequately plan the study, which can result in an underestimation or overestimation of exposure to noise. Finally, the results of this study are important for a) a broader understanding of the relationship between the level of noise and exposure time and b) proper planning and performance of measurements characterized by essential and active involvement of forestry professionals.

Keywords: Ergonomics, Forest Operations, Exposure to Noise, Skidding Distance, Time Study.