Site index is the most commonly used measure of potential site productivity, providing key information for forest management practices. It is determined using species-specific site index models that take into account climatic and edaphic factors. To reliably estimate the site index, appropriate models are necessary. In Poland, however, outdated guidelines, i.e., yield tables, are used to determine site classes, which result in the inappropriate estimation of height growth and increments of stands. Therefore, the aim of this study is to develop new site index models for the main forest forming tree species in Poland, in a total of eight species. For the development of site index models, we used growth trajectories of 3052 sample trees, representing the whole range of geographic locations and site conditions. Five dynamic models were selected and parametrized to develop the site index models. The models were evaluated using quantitative measures of goodness of fit (MAE, R2, and AIC), the analysis of residuals, and the assessment of how the model reflects the biological phenomena of height growth. Results showed that depending on the species, different models have the highest predictive ability. There are significant differences in results using traditional yield tables and developed site index models. For most of the species, the largest differences characterized either the youngest or the oldest age classes. These differences can be attributed to the changes in growth conditions from the time when yield tables were developed. Growth dynamics of forest stands may also show spatial variability, thus, in future research additional site variables and, regional variability should be taken into account.

Knowledge of the potential productivity of forest sites is fundamental for making strategic decisions in forest management. Site productivity is usually evaluated using the site index, and therefore the development of site index models is one of the crucial tasks in forest research and forest management. This research aims to develop an effective method for building top-growth and site index models using data from temporary sample plots (TSP). Exploiting the advantages of the generalised algebraic difference approach (GADA), the proposed method overcomes the limitations of the guide curve method that has been to date used in site index modelling using TSPs data and allows to obtain only a set of anamorphic site index curves. The proposed approach enables the construction of dynamic site index models with polymorphism and variable asymptotes. Such models better reflect local, site-specific height growth trajectories and therefore allow more appropriate site index estimation. We tested the proposed method using data collected from 5105 temporary sample plots in Poland. Our results indicate that growth trend estimates using height–age measurements of TSPs may be valuable data for modelling top height growth. For these reasons, the proposed method can be very useful in forest management.

In recent decades, forest fragmentation has been shown to directly increase forest mortality by increasing stress, damaging habitats, and heightening vulnerability to disturbances. It also disrupts local climates and ecological processes across various regions. Therefore, we aim to summarize the literature on forest fragmentation and forest mortality. The Web of Science Core Collection (WoSCC) database was searched using the PRISMA 2020 framework. We searched for publications from 1990 to 2023 and included research articles that reported on fragmentation and mortality. Out of the 159 articles found, we selected 119 research articles for systematic review. Our review documents that most studies on forest fragmentation and forest mortality tend to be relatively short-term, focused on a local or regional scale, and based on ground survey data. We identified articles from 35 countries and major hotspots for research on forest fragmentation and mortality. The results identified that the most underrepresented biomes are Mediterranean forests, woodlands and shrubs, boreal forests, and tropical and subtropical dry broadleaf forests. The longer the time horizon of the studies, the more neutral and positive effects of forest fragmentation are reported. These positive effects are more likely to be reported for temperate biomes and studies using field measurements. The study highlighted the importance of adopting a global perspective and integrating diverse methodologies to advance our understanding of forest fragmentation and mortality. Based on our findings, we recommend that future research on forest fragmentation and mortality should have a consistent geographic distribution, use varied methodologies, and perform the efficient integration of existing data types to improve the comparability and reliability of the results.

The site index (SI) is the most commonly used and representative measure of the phytocentric approach; it evaluates the site productivity based on the stand height and age. In the case of mixed stands with complex structures, phytocentric methods are very limited, while in non-forest areas, they are not ap­plicable. In situations where the applicability of phytocentric methods is limited, the site productivity is de­termined by geocentric methods. Geocentric methods allow direct modelling of site productivity, expressed by SI predicted from various environmental variables. The aim of this study was to develop a geocentric model for oak. Site productivity expressed by SI was described by the environmental variables and stand characteristics. To develop the SI model, we used the data from 2490 NFI plots with dominant oak species (Quercus sessilis and Quercus robur). A generalized additive model was used in modelling site productivity. We documented a significant relationship between SI and the environmental variables, age of stands and stand density. Furthermore, the site productivity for oak is shaped by climate factors, soil type, geology, and altitude. The model developed based on the geocentric method, explained 55.1% of the variation of SI