Abiotic factors impact on oak forest decline in Lorestan Province, Western Iran

www.nature.com/scientificreports OPEN Abiotic factors impact on oak forest decline in Lorestan Province, Western Iran Saeed Mehri 1, Ali Asghar Alesheikh 1* & Aynaz Lotfata 2 The Zagros oak forests in Iran are facing a concerning decline due to prolonged and severe drought conditions over several decades, compounded by the simultaneous impact of temperature on oak populations. This study in oak woodlands of central Zagros forests in Lorestan province analyzed abiotic factors such as climate properties, topographic features, land use, and soil properties from 1958 to 2022. We found that higher elevation areas with steeper slopes and diverse topography show significant potential for enhancing oak tree resilience in the face of climate change. Additionally, traditional land use practices like livestock keeping and dryland farming contribute to a widespread decline in oak populations. Preserving forest biodiversity and ensuring ecological sustainability requires immediate attention. Implementing effective land-use management strategies, such as protecting and regulating human-forest interaction, and considering meteorological factors to address this issue is crucial. Collaborative efforts from stakeholders, policymakers, and local communities are essential to oppose destructive suburban sprawl and other developments. Sustainable forestry practices should be implemented to improve the living standards of local communities that rely on forests and traditional livestock keeping, offer forestry-related jobs, and ensure social security. Such efforts are necessary to promote conservation awareness and sustainable practices, safeguarding this unique and vital ecosystem for future generations. Keywords Abiotic stressors, Meteorological factors, Ecosystem sustainability, Drought, Time series Forests are the most widely distributed terrestrial vegetation type, and as such, they play a significant role in providing the environmental context for regional and global ecosystems1,2. Tree mortality and forest degradation have increased globally during the last few decades. Forest trees are routinely exposed to a wide range of biotic, e.g., fungal i nfections3,4, borer b eetles5, and green oak t ortrix6 and abiotic, e.g., extreme climate c onditions7,8, soil 9 10 degradation , and topography . These stressors vary in intensity and duration and often occur concurrently or rapidly11,12, subjecting forest trees to a constant and diverse range of challenges. Abiotic factors have the potential to amplify the impact of concurrent biotic stress on forest trees, either through direct physiological interactions or by triggering disease outbreaks, ultimately leading to tree decline13. With rising temperatures and shifting weather patterns, forests face numerous challenges like deforestation, degradation, and stunted g rowth14–17. These factors, influenced by climate change, undermine the forests’ capacity to serve as crucial carbon s inks18. Droughts profoundly impact trees, leading to considerable stress and an increased risk of tree mortality17. During severe drought conditions, the normal functioning of plant cells may be compromised, disrupting the dynamics of both primary and secondary metabolism. Consequently, the trees may experience a reduction in their defense capacity, making them more susceptible to pests and pathogens. The impairment of plant cell functioning under severe drought can weaken the trees’ ability to effectively ward off diseases, further exacerbating their vulnerability to biotic stressors19–21. Oak decline is a multifactorial event influenced by several biotic and abiotic (e.g., climate changes and drought) acting in time and s pace22–25. López-Sánchez et al.14, Brown et al.26, Hernández-Lambraño et al.15, and Macháčová et al.27 indicated that climate extremes, e.g., summer drought, precipitation deficit, and high temperatures are the primary causes of oak mortality. Also, there is a complex interplay between climatic parameters and various biotic stressors, highlighting the multifaceted nature of oak decline and the need for targeted conservation efforts to mitigate its adverse effects26. Furthermore, Hernández-Lambraño et al.15 and Crocker et al.28 indicated the risk of oak 1 Department of Geospatial Information Systems, Faculty of Geodesy and Geomatics Engineering, K. N. Toosi University of Technology, Tehran, Iran. 2Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, USA. *email: Scientific Reports | (2024) 14:3973 | https://doi.org/10.1038/s41598-024-54551-6 1 Vol.:(0123456789) www.nature.com/scientificreports/ decline is exceptionally high in mid and upper slopes, south-facing aspects with high solar radiation, and steep convex slope segments with a dry soil moisture regime. Soil is considered the most important component of forests as it provides minerals and nutrients for plants, and its physical and chemical properties play a crucial role in oak growth29–32. Soil sand, silt, and density are important physical properties that affect soil fertility and p roductivity33. Soil physical properties determine the ease of root penetration, water availability and the ease of water absorption by plants, the amount of oxygen and other gases in the soil, and the degree to which water moves both laterally and vertically through the soil. Soil physical properties also influence the natural distribution of forest tree species, growth, and forest biomass production34. The chemical properties of forest soils are also important for oak forest g rowth35. Important indices of the chemical behavior of all soils are pH, cation-exchange capacity (CEC), Nitrogen, Calcium, Magnesium, Sodium, Soil Organic Carbon (SOC), anion-exchange capacity (AEC), base saturation (BS) percentage, exchangeable sodium percentage (ESP), electrical conductivity, and redox potential33,35. Like other oak-dominated woodlands worldwide10,23–25,36,37, the Zagros oak forests of Iran have one of the most alarming decline trends4,37,38. The Zagros forests cover a large area of the Zagros Mountains ranges, stretching from the northwest to the south of Iran (Fig. 1). Oak, with a diverse range of species, is the dominant genus in this r egion38–41. With an average length and width of 1300 and 200 km, respectively42. The Zagros forests cover approximately six million hectares, representing almost 44% of the Iranian forest c over43. This is the most significant forest habitat of Iran, distributed across ten provinces of the country, including West Azerbaijan, Kurdistan, Kermanshah, Lorestan, Chaharmahal and Bakhtyari, Kohgiluyeh, and Boyerahmad, Ilam, Khuzestan, Esfahan, and F ars38,44. These forests have a Mediterranean climate characterized by warm to hot, dry summers and cold or mild moist winters16. The Zagros forests are dominated by various oak species, creating a diverse ecosystem across the region39,46. These oaks are typically class (...truncated)