Silver fir (Abies alba Mill.) is one of the most valuable and productive tree species across European mountains, that accomplish multiple economic, protective and ecologic functions. Alongside spruce (Picea abies (L.) Karst) and beech (Fagus sylvatica L.), silver fir is a characteristic species for the Romanian Carpathians. Although silver fir tree is recommended for the diversification of forests in order to increase the resistance to climate change, it is very sensitive to climatic excesses, especially those that proceed rapidly. Therefore, the aim of this study is to investigate both the environmental conditions and stand characteristics of fir from five mountain ranges of the Romanian Carpathians. The study is based on data recorded over a period of 10 years (1990–2000). As such, a total of 77,251 stands that occupy 211,954 hectares have been investigated in regard to silver fir behaviour. MATLAB scripts were used for analysing consistent data volumes as well as the impact of eight factors on the silver fir productivity (altitude, field aspect, field slope, soil type, participation percentage, road distance, structure and consistency). Our analysis has revealed that higher silver fir productivity is found at altitudes of up to 1200 m, on mid and upper slopes, on NW field aspects, on eutric cambisols and dystric cambisols, with a 10–20% participation in stand composition and in relatively-even aged stands with a full consistency. This study offers valuable insights for forest managers that require comprehensive information in adopting effective strategies to enhance forest resilience under climate change.

Plant indicators are important in studies related to the environment, and mountain forests are rich in such plants. We conducted this study using the Web of Science Core Collection tools and the VOSviewer program combined with a classic review, based on the specialty literature. The topic of indicator plants in mountain forests has been (the first article published in a prestigious journal dates back to 1980) and remains relevant (after 2015, between 40 and 60 articles were published annually), with the total number of publications found being 665 articles and 22 review articles. These publications were authored by researchers from 96 countries, the most representative being the USA, China, and Germany (which also have large areas of mountain forests), and were published in 306 journals, with the most important being Ecological Indicators, Forest Ecology and Management, Forests, Journal of Vegetation Science, and Plant Ecology. They belong to the main scientific fields of Ecology, Forestry, Plant Sciences, and Environmental Sciences. The most frequently used keywords are vegetation, diversity, biodiversity, and forests. Their evolution over the past decade shows that the focus has shifted from keywords specific to this topic to those related to biodiversity and conservation, and more recently to climate change. Indicator plants in mountain forests are extremely varied but can be used successfully in the monitoring activity. Climatic conditions or human interventions lead to the dynamic of these indicator plants.

Water is the matrix of life and is indispensable on Earth. Water has a multitude of applications and all known life forms depend on it. Therefore, water quality is important for all of us. Water quality can be represented by a set of physical, chemical, biological and bacteriological characteristics. These parameters allow water to be classified in multiple categories leading to its use for a specific purpose. This chapter establishes the connections between external causes and their effect on water quality parameters. In order to provide information on water quality, different Water Quality Index (WQI) models can be used. In order to study the association between water quality parameters, several correlation coefficients have been developed. For a coherent statistical approach, we have used Pearson and Spearman correlations. In order to exemplify the manner in which WQI can be calculated and interpreted, we used a series of data from our previous work, consisting of 13 parameters measured for water samples taken from the Danube River, from Galati City area, Romania.

The present study analysed how growth of the Norway spruce (Picea abies (L.) H.Karst.) is influenced by site conditions throughout the Eastern and Southern Romanian Carpathians. In order to achieve the aim and the objectives stated in the present study, the volume of spruce stands was taken into account and grouped into six transects, both in the north–south direction in the Southern Carpathians and in the east–west direction in the Eastern Carpathians. We used data that were extracted from the forest management plans of the areas, carried out during the period of 1980–2005. For the Eastern Carpathians, the results revealed that at the same altitudes (700–1000 m), the volumes were higher on the eastern cline than on the western. In the case of the Southern Carpathians, for altitudes between 1300 and 1600 m, the volume of trees in the southern cline was greater than that of the trees in the northern cline. It was also found that the pure spruce stands had higher growth than the mixed ones for the same age and altitude; this was true in the cases of both the Eastern and Southern Carpathians.

Air pollution is a major but often under-integrated driver of forest dynamics at the global scale. This review combines a bibliometric analysis of 258 peer-reviewed studies with a synthesis of ecological, physiological, and biogeochemical evidence to clarify how multiple air pollutants influence forest structure, function, and regeneration. Research output is dominated by Europe, East Asia, and North America, with ozone, nitrogen deposition, particulate matter, and acidic precipitation receiving the greatest attention. Across forest biomes, air pollution affects growth, wood anatomy, nutrient cycling, photosynthesis, species composition, litter decomposition, and soil chemistry through interacting pathways. Regional patterns reveal strong context dependency, with heightened sensitivity in mountain and boreal forests, pronounced ozone exposure in Mediterranean and peri-urban systems, episodic oxidative stress in tropical forests, and long-term heavy-metal accumulation in industrial regions. Beyond being impacted, forests actively modify atmospheric chemistry through pollutant filtration, aerosol interactions, and deposition processes. The novelty of this review lies in explicitly framing air pollution as a dynamic driver of forest change, with direct implications for afforestation and restoration on degraded lands. Key knowledge gaps remain regarding combined pollution–climate effects, understudied forest biomes, and the scaling of physiological responses to ecosystem and regional levels, which must be addressed to support effective forest management under global change.

The climate has changed significantly over the past few decades around the globe. To make meaningful comparisons between changes occurring over time in the tree world, comprehensive databases on the most important species and their evolution must be created. It is essential to consider latitude, longitude, altitude and local relief when analyzing data. Given the extensive distribution of oak, hornbeam and ash, a sequence analysis was conducted to definitively examine the characteristics of these species in West Plain, West Hills, Apuseni Mountains and Transylvania's Tableland. The data for all the regions comprised a total of 708511 ha, which were subjected to rigorous analysis to determine characteristics such as yield class, volume, increment, structure and participation percentage. The data was analyzed using the most appropriate modern statistical programs, including correlation matrices, ANOVA, principal component analysis, matrix data analysis and the cluster method. In relation to the altitudinal variation, oak is present at average altitudes of 200–250 m in West Plain, 400–500 m in West Hills and Transylvania's Tableland, and 900–950 m in Apuseni Mountains. Hornbeam has a similar spreading with oak, but records its presence in slightly higher altitudes of West Hills (400–700 m) and lower in Apuseni Mountains (700–750 m). Volume is also an important indicator, as it is susceptible to climate change. Oak has the highest age-volume, over 95 years, while ash and hornbeam have it less than 90 years. The results are crucial for understanding the ecological requirements of oak, hornbeam and ash, as well as for effectively managing these forests.