wielkością korony a przyrostem drzew w drzewostanach sosnowych. Prace Komisji Nauk Rolniczych i Komisji Nauk Leśnych PTPN , 25: 43-90. Lemke J. 1972. Retrospektywna analiza wzrostu i przyrostu drzew w 50-letnim drzewostanie sosnowym. Folia Forestalia Polonica, Seria A , 19: 5-23. Skrzyszewski J. 1995. Charakterystyka przyrostowa oraz kształtowanie się zależności pomiędzy wybranymi cechami drzew a przyrostem promienia na pierśnicy świerka i modrzewia. Acta Agraria et Silvestria, Series Silvestris , 33: 141-158. Svensson S.A. 1998. Estimation of annual stem volume
Annual height increments are a very important characteristic of Scots pine. They have a direct effect on the determination of the dendrometric properties of a stand, such as volume increment. In the present study the data concern height increments of the main shoot in selected age classes of trees (age 72 to 92 years). A relationship is determined between the values of the increments and meteorological conditions such as temperature, precipitation and sunshine. On the basis of lasso regression analysis, precipitation in the year preceding the incremental season was shown to have the greatest effect on height increments of Scots pine.
The MODIS (The Moderate Resolution Imaging Spectroradiometer) yearly NPP (Net Primary Production) 1 km resolution products were collected over Estonia for years 2000-2010. The MODIS NPP product for forest pixels showed a clear West-East decreasing trend over the Estonian territory. At the same time the trunk volume increment estimates extracted from the Estonian national statistics averaged over the same period showed the opposite trend. The MODIS NPP algorithm seems to overestimate the contribution of meteorological variables and to ignore the role of soil fertility differences. To improve the predictive power of MODIS algorithm to describe local NPP differences, the local meteorological data with higher spatial resolution should be used as an input in the NPP calculations, whereas the algorithm should be modified by optimizing the input parameters and including parameters of soil fertility into the calculation scheme.
Forest growth is commonly used to explore tree vitality and ability to resist to environmental changes or climatic fluctuations. This paper illustrates and examines how regional climatic conditions can be related to the decline of tree growth, which were found to be more distinct in Quercus frainetto Ten. (Hungarian oak) and Fagus sylvatica L. (European beech) and less pronounced in Abies borissi-regis Matt f. (Bulgarian fir) on three long-term intensive monitoring plots (ICP Forests-Level II) in Greece during the period 1996–2009. Relative basal area increment and volume increment were calculated, expressing tree growth in terms of mean relative annual periodic increment. A decline in the growth of basal area and volume was observed after hot and dry periods, where annual temperatures and precipitation were far from the mean of the analyzed period. This observation was statistically confirmed in oak and beech plots regarding summer precipitation only and are in agreement with the findings of previous studies in Europe. The representativeness of the results at a national scale needs further investigation, although our results provide a good basis for further and more intensive monitoring programs to address various forest management scenarios against the background of potential climatic changes in the Mediterranean area.
Scheduling and regulation of the forest use are of much importance in forest management. Decisions regarding the manner, timing, and intensity of tree felling result in long-term effects, as these affect the species and age structure of forests, along with the direction and dynamics of changes in forest resources. Above all, serious doubts concern the way of determining and accounting for the prescribed forest utilization, and in particular, the possibilities of the pre-final cuttings. In recent times, the precise determination of the pre-final cuttings by volume has been given up. According to the law, the area of pre-final cuttings is now obligatory taken into account. Consequently, it is not possible to determine the total volume limiting the amount of timber to be harvested, thus, there is decreased the value of the forest management plan as the document approved by the minister responsible for forestry as well as the basis for forest management. For practical reasons, the specified pre-final cuttings by volume are considered as indicative.
Connecting the planned pre-final cutting volume with the expected volume increment of the stand has not been relinquished. In the present paper, the authors called attention to a necessity for further improvement of the medium-term planning of pre-final cutting volume. A need to change the definition of the incidental cutting was emphasized. As said by the authors, the term “incidental cutting” should denote harvesting wood from diseased and dying or dead trees, along with eliminating the effects of tree damage caused by fortuitous events. Accordingly, the incidental cuttings that are inherently unpredictable, should not be directly attributed to pre-final cutting products. Keeping in mind the incidental cuttings, the authors proposed the method of reckoning the forest use, which would allow for correct accounting with regard to the prescribed pre-final cuttings.
Pruning requires significant investment, therefore, the aim of the study was to characterize occlusion of branch wounds and changes in radial increment as well as frequency of browsing damages after pruning of Norway spruce (Picea abies (L.) Karst.) in order to provide data for financial calculations and recommendations for practical forestry. Altogether 1,614 pruned and 4,368 unpruned trees from 45 Norway spruce stands were measured and cored. Degree of wound occlusion and browsing damages were assessed, and additional volume increment estimated in each stand. Pruning resulted in significant increase of length of branch-free section: for unpruned trees it was 0.3 ± 0.07 m, but for pruned 3.4 ± 0.10 m. Branch wounds for most of the trees (68%) were filled with resin (occluded), for lower share of trees (31%) – still open, but for some trees (1%) completely occluded. Branch wound occlusion rate was not affected by differences in stand density, but was significantly affected by stand age: proportion of trees with occluded branch scars increased with age. Trees with occluded branch wounds had a significantly higher increase in tree ring width after the pruning in comparison to the period before pruning than trees with open branch wounds, emphasizing the importance of radial increment in development of branch-free layer of wood. Pruning resulted in minor (−7% or −0.28 ± 0.05 m3 ha−1) reduction of annual increment that was statistically significant only up to 3 years after this forest management activity for stands younger than 17 years and with mean height up to 10.5 m. Pruned trees were significantly more browsed than unpruned (6.1% and 2.7%, respectively).
Optical remote sensing data-based estimates of terrestrial net primary production (NPP) are released by different projects using light use efficiency-type models. Although spatial resolution of the NPP data sets is still too coarse (500–1000 m) for single forest stands, regional monitoring of forest management and growth with 25–100 ha sampling units is feasible if the NPPSAT estimates are sensitive to forest growth differences depending on soil fertility in the area of interest. In this study, NPP estimates for 2,914 mixed forest class pixels (according to the MODIS land cover map) located in Estonia were (1) obtained from three different NPPSAT products, (2) calculated using an empirical soil potential phytoproductivity (SPP) model applied to a 1:10,000 soil map (NPPSPP), and (3) calculated using stem volume increment estimates given in a forest management inventory data base (NPPFIDB). A linear multiple regression model was then used to explore the relationships of NPPSAT with the proportion of coniferous forests, the NPPSPP and distance of the pixels from the Baltic Sea coast – the variables that have been found informative in previous studies. We found a positive moderate correlation (0.57, p < 0.001) between NPPSPP and NPPFIDB. The local or downscaled meteorological data-based NPPSAT estimates were more consistent with the NPPSPP and NPPFIDB, but the correlation with NPPSAT was weak and sometimes even negative. The range of NPP estimates in NPPSAT data sets was much narrower than the range of NPPSPP or NPPFIDB. Errors in land cover maps and in estimates of absorbed photosynthetically active radiation were identified as the main reasons for NPPSAT inconsistencies.
Thirteen Nordic stand growth models have been validated by use of a test data set from long-term research plots in Norway. The evaluated data was from time-series of even-aged, pure stands of Norway spruce, Scots pine and birch (silver birch and downy birch). In selected models from Finland, Norway and Sweden measures of site productivity, mean tree size and various stand characteristics are represented. Different models display both strengths and weaknesses in their predicting ability. Several measures of precision and bias have been calculated and the models are ranked due to their performance. We observed site quality, stand density and average tree size as the three main components in the models. Basal area increment model for spruce from Sweden had the lowest standard deviation with 23%. The mean R2 between residuals and stand characteristics from this model was also low (1.3%), which indicates that independent variables are well included. For Scots pine and birch, Finnish volume increment models showed the best fit to the Norwegian test data, with a R2 between residuals and stand characteristics of 2.8 and 6.7%, respectively. Several of the models from Sweden and Finland predicted the growth as well as stand models frequently in use in Norway. The results indicated that similar forest conditions and traditional even-aged forest management practice in the Nordic countries could be seen as a suitable basis for developing a joint family of growth models. By careful recalibration of existing models, a reasonable accuracy could be achieved and the prediction bias could be reduced.
The aim of the study was to characterise changes in the natural forest of the Białowieża National Park (BNP) Strict Reserve during a 15-year period. To allow for a more precise determination of the time course, overall duration and intensity of the observed changes, the 15-year period was further divided into shorter 2-7-year intervals. Taken together, the Strict Reserve forest stands cover 4584 hectares and they constitute the oldest part of the Białowieża Forest placed under protection in 1921.
The measurements were carried out in 2000, 2002, 2004, 2011 and 2015 on 160 permanent sample plots, which are systematically distributed throughout the BNP Strict Reserve. During those 15 years, the volume of merchantable timber and the tree density fluctuated only slightly, because the reduction in standing volume due to a spruce and ash decline was compensated for by an increase in the standing volume of lime, hornbeam and alder. The volume increment and tree loss fluctuated slightly, but were nevertheless similar throughout the whole period between 2000 and 2015. The number of trees in the regeneration layer increased. The number of hornbeam trees in this layer increased continuously throughout the whole measurement period, while the number of maple trees started to increase in the second half. All together only five tree species growing in the BNP Strict Reserve progressed from the regeneration layer to the canopy layer in significant numbers. As a result, a gradual decrease in species diversity of forest stands may be expected.
The rather stable, average volume of merchantable timber in the BNP Strict Reserve may be due to the fact that, in a forest with diverse habitats and high species richness, only a few stands are subjected to strong disturbances in a given period of time. Repeated measurements during a relatively short period of time allowed the detecting some fairly quick changes occurring in natural lowland forests.
A light use efficiency (LUE) type model named EST_PP to simulate the yearly gross primary production (GPP) and net primary production (NPP) of Estonian land on a 1 km2 grid is described. The model is based on MERIS (MEdium Resolution Imaging Spectrometer) satellite images to describe the fraction of photosynthetically active radiation (fAPAR) and leaf area index (LAI) as well as meteorological reanalysis datasets on 11 km2 grid produced by Estonian Meteorological Institute (EMHI) and Tartu University (TU) by means of the HIRLAM (High Resolution Limited Area Model) numerical weather prediction model. The land cover map of Estonia needed for the model was derived using DMCii (Disaster Monitoring Constellation International Imaging) SLIM-6-22 (Surrey Linear Imager - 6 channel - 22 m resolution) images and ancillary information. The EST_PP model was run for the period from years 2003 to 2011. The results of GPP and NPP simulation are compared with the available global MODIS (Moderate Resolution Imaging Spectroradiometer) GPP/NPP product and with the Estonian statistical data on yearly volume increment in forests and on yield of agricultural crops. The NPP simulation results on coniferous and deciduous forests are compared with the data from tree ring analyses from different counties. These comparisons show us that the simulated country average yearly NPP values for Estonian forests agree reasonably well with the indirect estimates from other sources, taking into account the rather high uncertainty of the model predictions, uncertainty of forest inventory-based estimates and limited representativity of existing tree ring data. However, problems arise with the ability of present versions of EST_PP and MODIS NPP models to adequately simulate the regional differences of productivity and of variability of productivity in different years. The model needs some modification and the basic LUE principles to be tested in Estonia. Nevertheless, the MODIS NPP and EST_PP models offer additional possibilities to map yearly productivity and carbon sequestration by Estonian vegetation. There is a perspective to add the model-simulated NPP values into the national inventory datasets.