Post-WWII displacements in the Polish Carpathians resulted in widespread land abandonment. Most of the pre-war agricultural areas are now covered with secondary forests, which will soon reach the felling age. Mapping their exact cover is crucial to investigate succession–regeneration processes and to determine their role in the landscape, before making management decisions. Our goal was to map post-agricultural forests in the Polish Eastern Carpathians using archival remote sensing data, and to assess their connectivity with pre-displacement forests. We used German Flown Aerial Photography from 1944 to map agricultural lands and forests from before displacements, and Corona satellite images to map agricultural lands which converted into the forest as a result of this event. We classified archival images using Object-Based Image Analysis (OBIA) and compared the output with the current forest cover derived from Sentinel-2. Our results showed that mature (60–70 years old) post-agricultural forests comprise 27.6% of the total forest area, while younger post-agricultural forests comprise 9%. We also demonstrated that the secondary forests fill forest gaps more often than form isolated patches: 77.5% of patches are connected with the old-woods (forests that most likely have never been cleared for agriculture). Orthorectification and OBIA classification of German Flown Aerial Photographs and Corona satellite images made it possible to accurately determine the spatial extent of post-agricultural forest. This, in turn, paves the way for the implementation of site-specific forest management practices to support the regeneration of secondary forests and their biodiversity.

Spatial accessibility is usually understood in relation to the possibility of a specific location being reached from another location (Guzik, 2014). It is one of the main factors affecting land use and land-use changes (Hansen, 1959; Prishchepov et al., 2013) in relation to which the greatest variation is to be observed in mountainous areas (Jobe & White, 2009). The aim of the study detailed here was thus to identify variation in the spatial accessibility of mountainous areas in terms of their being used in agriculture. The problem of agricultural accessibility is here exemplified by three mesoregions of the Polish Carpathians, i.e. the Bieszczady Mts., Low Beskid Mts. and Sanok-Turka Mts. These are all areas in which spatial accessibility and landscape structure have changed markedly over the last 70 years. Cost of access in these areas was calculated by assigning resistance values to each distance unit, in relation to land-cover type and slope. To generate an output raster, use was made of a cost-distance algorithm implemented in ArcGIS. The research described here gave rise to a figure presenting the agricultural accessibility of the study area. Very varied accessibility was demonstrated, both in the research area as a whole and between mesoregions. Results obtained were compared with values for currently used arable fields. Areas accessible to agriculture were also identified, and compared with the distribution of arable fields actually in existence.

North American goldenrods ( Solidago spp.) rank among the most ecologically impactful invasive plants in Europe, Asia, and other regions. Their spread is driven by high ecological plasticity, rapid growth, and allelopathic effects. While the number of publications on Solidago invasions has grown substantially in recent decades, existing reviews tend to be narrative and focus on single species or few mechanisms. In this systematic review, we analyze 180 peer-reviewed empirical studies to assess global trends, methodological approaches, and research biases in studies addressing interactions between invasive Solidago and the environment. Most studies applied a single methodological approach, with ex situ experiments dominating, while field observations and in situ manipulative experiments were less common. Long-term studies were rare, and research primarily addressed current conditions rather than future scenarios. The taxonomic focus was centered on S. canadensis L., with other species being much less studied. Geographically, research was concentrated in Europe and Asia, with field-based studies more common in Europe and ex situ experiments dominating in Asia. Solidago spp. served as either a response or an explanatory variable, reflecting both its response to environmental conditions and its impact on the invaded ecosystem.

The regeneration dynamics of understory vegetation in recent forests, arising from extensive agricultural land abandonment, is closely related to soil properties and proximity to ancient forests. However, the role of topography in shaping this regeneration process, especially in mountainous regions, remains unclear. This study addresses this gap by investigating the regeneration rate of understory vegetation in mountainous recent forests within the NE Carpathians, a region profoundly shaped by large-scale population displacements in the 1940s, leading to widespread agricultural land abandonment and the subsequent development of new forests. We quantified the understory regeneration rate of recent forests through extensive phytosociological relevé surveys conducted in one vegetation season. Data were collected from 194 randomly selected plots of recent forests and 100 plots of ancient forests, each exhibiting diverse topographic characteristics. By calculating the Forest Maturity Index based on ancient forest species and employing a parametrized multiple regression model, we identified key factors influencing the understory regeneration process. We further used the obtained regression formula to model the forest regeneration rate across the entire study area (40,975 ha). Proximity to ancient forests positively influenced understory regeneration. Elevation and slope also emerged as significant determinants, with the understory regeneration rate decreasing with elevation and increasing with slope steepness. Furthermore, a higher cover of pine in the tree stand had a suppressive effect. The above-mentioned dependencies resulted in substantial variations in the modeled understory regeneration of post-agricultural forests. The utilization of the Forest Maturity Index offers invaluable insights into identifying and subsequently safeguarding well-regenerated forests. Given the prevalence of forest secondary succession in various regions, this index emerges as a key indicator for future assessments and management strategies.

North American goldenrod species Solidago gigantea and S. canadensis were introduced to Poland in the second half of the 19th century as ornamental plants and nectar sources for honey production. However, only in recent decades – mainly as a result of land-use changes and the abandonment of agricultural land – have they begun to spread on a large scale. Nowadays, they are considered highly invasive, as they are rapidly expanding and outcompeting native species, and pose a serious threat to the proper functioning of entire ecosystems. One of the objectives of the SolidES project ( Countrywide mapping of goldenrod invasion and assessing its impact on ecosystems and human well-being ) is to assess the impact of goldenrod invasion on habitat conditions, biodiversity and ecosystem functioning across trophic levels. In 2025, we carried out a multi-faceted assessment of ecosystem condition in 20 randomly selected, at least one-hectare patches of abandoned arable land affected by goldenrod invasion in the Masovian voivodeship, Poland. We investigated soil properties, plant biomass production, and the diversity of plants and animals (i.e., insects and earthworms). Comparative studies were carried out in adjacent, similar ecosystems not affected by the invasion. Fieldwork was conducted twice during the growing season: before flowering (June) and during goldenrod flowering (August), to take into account seasonal differences. The research included: collection of phytosociological relevés, direct extraction of plant biomass separated into above- and below-ground fractions, collection of mixed soil samples to examine their physical and chemical properties, and soil enzymatic activity, measurement of soil CO ₂ flux, sampling of soil fauna (earthworms) – abundance and biomass measurement and functional group identification, sampling of plant-related invertebrates by sweep-netting – counting and functional group identification, monitoring of flying pollinators (bumblebees by the route method) – counting and species identification, sampling of epigeic fauna using pitfall traps. collection of phytosociological relevés, direct extraction of plant biomass separated into above- and below-ground fractions, collection of mixed soil samples to examine their physical and chemical properties, and soil enzymatic activity, measurement of soil CO ₂ flux, sampling of soil fauna (earthworms) – abundance and biomass measurement and functional group identification, sampling of plant-related invertebrates by sweep-netting – counting and functional group identification, monitoring of flying pollinators (bumblebees by the route method) – counting and species identification, sampling of epigeic fauna using pitfall traps. We observed significant differences in plant species richness and diversity as well as in the plant biomass between invaded by goldenrods and non-invaded plots. Results of soil properties were more ambiguous. For instance, actual moisture, capillary porosity and soil air capacity varied significantly, while organic matter content, CO ₂ flux and several chemical properties show no significant differences between plot types. No clear trends were observed for invertebrates either. Earthworms’ abundance and biomass do not differ between invaded by goldenrods and non-invaded plots. In turn, wild pollinators’ abundance was significantly higher in June in the reference plots than in the plots with goldenrods, while in August this difference was not statistically significant. Our results identify drivers of goldenrod invasion success, and highlight the ecosystem components and functions most strongly affected by its spread.

Biological invasions are complex processes involving multiple interacting factors rather than simple cause–effect relationships. In this study, we present a synthetic framework linking three key components of invasion ecology: drivers of invasion, ecological impacts, and feedback mechanisms. Our synthesis of ecological studies on invasive Solidago species, reflects current empirical knowledge across diverse ecosystems. Based on a systematic review of over 200 empirical studies, we analyse how invasion success depends on the interaction among species traits (e.g. dispersal ability, phenotypic plasticity), environmental conditions (e.g. resource availability, disturbance), and propagule pressure. We synthesise the ecological impacts of Solidago , including changes in plant community composition, reductions in native biodiversity, alterations in soil properties and nutrient cycling. These effects often extend across trophic levels and may lead to long-term changes in ecosystem structure and functioning. We show that disturbances and human-mediated pathways play a major role in facilitating the spread of Solidago , while biotic resistance of ecosystem can limit invasion under certain conditions. We highlight the role of feedback mechanisms, especially plant–soil interactions, which can reinforce invasive species dominance. By modifying soil conditions, microbial communities, and resource availability, Solidago can create conditions that favour its own persistence and further spread. Our synthesis shows that drivers, impacts, and feedbacks are strongly interconnected and context-dependent. Considering these components together provides a more complete understanding of Solidago invasion dynamics than analysing them separately. We also identify key knowledge gaps, particularly regarding causal relationships and the role of environmental context. This integrative perspective may improve predictions of invasion outcomes and support more effective management strategies for invasive species.