THE REINTEGRATION OF THE SURFACES AFFECTED BY THE PHENOMENON OF SUBSIDENCE THROUGH THE CULTIVATION OF TREES WITH HIGH ENERGY VALUE

Objective: The objective of this study is to investigate the subsidence phenomena resulting from coal mining activities in Romania's Jiu Valley region, along with the environmental and socio-economic impact issues arising from subsidence in the Jiu Valley. Theoretical Framework: The theoretical framework provides a comprehensive understanding of subsidence challenges in the Jiu Valley, Romania, and highlights the importance of proactive measures such as afforestation for addressing these challenges while promoting environmental sustainability and economic prosperity. Method: The methodology adopted for this research involves a multidisciplinary approach integrating field surveys, geospatial analysis, environmental assessment, and stakeholder engagement. Results and Discussion: The results of the paper underscore the effectiveness of afforestation as a sustainable solution for addressing subsidence challenges in the Jiu Valley, offering environmental, economic, and societal benefits for the region's long-term development and resilience. The work effectively highlights the concept of subsidence, both as a natural process and as a result of human activities such as mining. By emphasizing the negative effects of subsidence on land stability, infrastructure, and community safety, the introduction underscores the urgency of addressing this issue in regions such as the Jiu Valley.


INTRODUCTION
Subsidence is the process by which soil naturally sinks, either due to natural causes or human activities such as excessive exploitation of underground resources or underground construction.This phenomenon can lead to land deformation, building collapse, and other adverse effects on the environment and communities.Subsidence can be caused by various factors such as soil erosion, groundwater depletion, melting glaciers, or mining activities.
Measures to manage or prevent subsidence include continuous monitoring of groundwater levels, reducing the overexploitation of underground resources, soil consolidation, and rehabilitating affected lands.Planting trees with high energy value can be an effective means to rehabilitate subsidence-affected land and prevent further damage.3 The Jiu Valley is a significant industrial and mining region in Romania, situated at the base of the Parang Mountains.Its climate is characterized by temperate mountain conditions, featuring cool summers and cold winters.Temperatures typically range between 0°C and 20°C, with the highest temperatures occurring during summer and the lowest during winter.
Precipitation is evenly distributed across the year, with elevated levels in summer and autumn.During spring, melting snow and rain can lead to flooding.Summers are mild, while autumn witnesses gradual temperature declines accompanied by rainfall.Frigid temperatures, heavy snowfall, and freezing conditions mark winter.These climatic factors significantly impact activities in the area and may result in natural hazards such as landslides and floods.
The predominant soil types in the area are brown, clay, and forest soils, influenced by both natural vegetation and local climatic conditions.Brown soils are characterized by a rich organic matter content, making them suitable for crops, while clay soils are abundant in minerals and plant nutrients.Forest soils, distinguished by their high organic matter content, also play a significant role [Apostu et all.].Furthermore, depending on altitude, sun exposure, and specific vegetation, other soil types such as ash, alluvial, or clay soils may be present, each offering unique characteristics suited for various agricultural or industrial activities.

Figure 1
The Jiu Valley area (Romania) Source: https://ro.wikipedia.org The vegetation in the Jiu Valley is diverse and well-adapted to the region's specific conditions, showcasing a variety of types influenced by altitude and sun exposure.Deciduous forests thrive in lower areas, while coniferous forests dominate higher elevations.Alpine 4 meadows adorn the high mountain regions, with subarctic vegetation gracing the mountain tops.
Additionally, the valley boasts various species of grasses, wildflowers, shrubs, and rare protected plants [Blaikie et all].
Renowned for its abundant coal resources and integral role in Romania's mining and steel industry, the region has historically served as a vital hub for mining activities.However, the Jiu Valley now faces challenges stemming from the decline of the mining industry, alongside economic and social shifts, necessitating solutions for economic restructuring, job creation, and infrastructure revitalization.
Coal mining in the Jiu Valley involves the extraction and processing of solid fossil fuel from underground for various industrial and sectoral applications.This process entails identifying coal deposits, excavating and transporting the coal to the surface, and processing it into a usable form for power generation and other purposes.
However, coal mining can impose significant environmental and societal impacts, including air, soil, and water pollution, land degradation, and adverse effects on human health.

Figure 2
Coal mining in the Jiu Valley (Romania) Source: https://www.zvj.ro In our region, subsidence has occurred as a consequence of underground coal extraction, resulting in the collapse and lowering of land levels.This phenomenon has adversely affected local infrastructure, the environment, and community safety, resulting in structural damage to buildings, environmental harm, and endangerment of residents [Itu et all].5 To address the repercussions of subsidence measures such as land monitoring, landscape restoration, adoption of sustainable mining practices, and adherence to safety protocols are imperative.
Furthermore, the mining industry has contributed to soil surface degradation through the creation of tailings dumps, primarily composed of unprocessed mineral materials or residues from mining operations.
These dumps adversely affect soil quality through erosion, chemical contamination, loss of biodiversity, drainage obstruction, and alterations in temperature regimes.Monitoring soil and groundwater quality is essential to mitigate the environmental impact of waste dumps.
One method to mitigate the collapse of tailings dumps is to establish dump slopes with a maximum inclination of 30%, followed by afforestation with trees.Trees possess the ability to thrive on steep slopes and low-fertility land without extensive intervention.Afforestation initiatives are generally implemented to control erosion and enhance land quality.
Afforestation plays a crucial role in mitigating landslide risks by facilitating the retention and gradual release of precipitation, thus averting erosion and landslide initiation.This afforestation initiative aims to cultivate trees with high energy value, with the potential to supplant the mining industry in the region in the future.
This paper endeavors to propose solutions for the reintegration of surfaces impacted by subsidence by advocating for the cultivation of high-energy value trees.This approach not only addresses environmental and societal concerns associated with coal mining but also offers a sustainable alternative for the region's economic development.

THEORETICAL FRAMEWORK
The theoretical framework for this paper is about the subsidence challenges in the Jiu Valley region of Romania and encompasses several key components.So is very important to understand subsidence as a process characterized by the sinking or settling of the Earth's surface, often attributed to natural geological phenomena or human activities such as mining.
This framework delineates subsidence as a significant environmental hazard, leading to land deformation, infrastructure damage, and socio-economic repercussions in affected areas.
Another Given the adverse effects of subsidence, the framework underscores the importance of implementing proactive mitigation strategies to address this issue.Afforestation emerges as a promising solution for mitigating subsidence impacts, stabilizing soil, restoring vegetation cover, and enhancing ecosystem resilience in subsidence-affected areas.
Afforestation initiatives not only mitigate the immediate impacts of subsidence but also contribute to the long-term environmental rehabilitation of affected lands.This framework emphasizes the role of afforestation in improving soil quality, promoting biodiversity, and restoring ecosystem functions crucial for sustainable land management.
Overall, this theoretical framework provides a comprehensive understanding of subsidence challenges, their environmental and socio-economic impacts, and the role of afforestation as a sustainable solution for mitigating subsidence impacts and promoting environmental rehabilitation in the Jiu Valley region of Romania.

METHODOLOGY
Land revegetation is the process of regenerating forests and restoring vegetation on lands affected by deforestation or various industries.It aims to restore biodiversity, conserve the environment, and ensure the sustainability of forest resources.This situation will improve only with the accumulation of humus and the formation of an edaphon (the totality of the organisms that live in the soil, linked to certain specific life conditions).It is also very important that the material from the tailings dumps has large variations from a lithological, structural, or granulometric point of view, even over short distances or depths.
Knowing the physical, chemical, and pedological characteristics of the soil is crucial for selecting the appropriate tree species.Additionally, when choosing species, the microclimate specifics must be considered, influenced by extreme weather events such as wind effects, direct sunlight, significant temperature fluctuations, and soil aeration [Itu et all].
Therefore, for the initial forest generation, selecting pioneer species like birch, hazel, and acacia is essential.These species not only thrive in challenging conditions but also contribute to desired microclimate alterations.Due to their unique characteristics, the first The afforestation plan for the Jiu Valley area is implemented in stages and by tree groups.In the initial stage, birch trees will be planted in areas with higher humidity, while acacia will be planted in the flat platform areas of the tailings dumps.
The proposal includes drought-resistant species suitable for the high temperatures prevalent in the landfill area.
The primary species will be birch, accounting for 70% of the planting, supplemented by acacia at a proportion of 30%.Shrubs will be planted starting from the first 10 meters in front of the slope base and along the drainage channels of the landfill.
Acacia thrives in well-drained, sandy, or loamy soil with ample sunlight exposure.It can tolerate nutrient-poor soil and less favorable environmental conditions, but optimal growth occurs in moderately moist and temperate conditions.Acacia typically does not require regular fertilization, as it can adapt to poor soil conditions.
Birch known for its medicinal properties and fine-grained, silky-textured wood with high energy value, is a prominent choice.It flourishes in well-drained, moist soil and requires ample sunlight exposure to grow and thrive.9

Figure 4
Birch plantation on the tailings dump Source: www.copacel.ro Acacia is esteemed for its high value as firewood and is renowned for its exceptional calorific energy and durability.It is a dense and weighty wood that burns slowly, emitting a substantial amount of heat.The calorific value of acacia wood varies based on species, growing conditions, and wood density, typically ranging from 4,500 to 4,800 kWh/ton.This implies that one ton of acacia wood generates approximately 4,500 to 4,800 kilowatt-hours of heat energy, positioning it among the hardwoods with the highest calorific values.Its slow burn rate and high heat output make it highly efficient for heating purposes.
Similarly, the calorific value of birch wood varies depending on species, growing conditions, and wood density, typically ranging from 4,000 to 4,300 kWh/ton.This means that one ton of birch wood produces approximately 4,000 to 4,300 kilowatt-hours of heat energy.
Birch wood is considered to have an average calorific value among hardwoods.It burns relatively quickly and emits a moderate amount of heat compared to other wood species with higher calorific values.
Acacia typically reaches a growth regime of 3-5 years after planting, with a maturity period of about 15-20 years.During the initial growth stages, acacia prioritizes the development of its root system and vegetative structure.12 Alternatively, during the initial growth phase of 3 to 5 years, a more immediate harvest of approximately 20 tons can be expected.Nonetheless, it is imperative to acknowledge that these estimations are subject to fluctuations contingent upon the interplay of the aforementioned factors.
Similarly, the yield of birch wood per hectare is subject to variability influenced by planting density, the age and vitality of the birch trees, forestry management methodologies, and prevailing growing conditions.
Generally, a hectare of birch plantation can generate an output ranging between 50 and 70 tons of wood throughout its full production cycle, spanning around 20 to 25 years.If harvested within the initial decade of growth, approximately 30 tons can be garnered.Yet again, it is crucial to recognize that these projections are susceptible to changes depending on the specific circumstances delineated above.

Figure 8
The amount of wood obtained per hectare Acacia wood and birch wood differ significantly in terms of appearance, density, workability, and applications.Acacia wood features a distinct grain pattern and rich color range, with exceptional hardness and durability suitable for heavy-duty applications.Birch wood, on the other hand, exhibits a finer grain pattern and lighter color palette, offering good strength and stability for various woodworking projects.The choice between the two depends on factors such as aesthetic preference, project requirements, and ease of working.
Considering the specific conditions of the Jiu Valley region, acacia emerges as a more suitable choice for planting compared to birch.Acacia is adaptable to various soil types and climate conditions, exhibiting faster growth rates and offering dense, durable wood suitable for a wide range of applications.Its resilience to drought and ability to thrive in poorer soils make it well-suited for the region's climate and economic considerations.Ultimately, acacia's adaptability and utility make it a practical choice for wood production in the Jiu Valley.

RESULTS AND DISCUSSIONS
The results of the study indicate that afforestation with trees with high energy value, such as acacia and birch, can effectively rehabilitate soil quality in the Jiu Valley tailings dumps.
Thus afforestation with acacia and birch contributes to improving the stability of the soil on tailings dumps, reducing the risk of erosion and landslides.Establishing tree root systems helps bind soil particles, preventing soil erosion and promoting slope stability.
Over time, afforestation leads to improved soil composition on tailings dumps.The accumulation of organic matter from tree litter and root exudates enriches the soil, increasing 14 its fertility and nutrient content.This process results in the gradual development of humus-rich soil, which is conducive to plant growth and ecosystem resilience.
The presence of trees with high energy value stimulates nutrient cycling in the soil, promoting the decomposition of organic matter and the release of essential nutrients.It improves soil fertility and supports vegetation growth, helping to restore ecosystem functions on degraded land.
Afforestation with acacia and birch stimulates microbial activity in the soil, leading to improved soil health and nutrient cycling.Microorganisms play a crucial role in breaking down organic matter, fixing nitrogen and promoting the availability of nutrients for plant uptake.The proliferation of beneficial soil microbes increases ecosystem resilience and contributes to the long-term sustainability of forested areas.
Restoring soil quality through afforestation has wider environmental benefits, including carbon sequestration, biodiversity enhancement and ecosystem restoration.High-energy trees such as acacia and birch contribute to carbon sequestration by absorbing carbon dioxide from the atmosphere and storing it in biomass and soil organic matter.In addition, afforestation creates habitat diversity, supporting a variety of plant and animal species and promoting ecosystem resilience to environmental stressors.
Overall, the results suggest that afforestation with trees with high energy value can be an effective strategy for soil quality rehabilitation on tailings dumps in the Jiu Valley.
By promoting soil stability, improving soil composition, improving nutrient cycling and stimulating microbial activity, afforestation contributes to the restoration of ecosystem functions and the sustainable management of degraded land.
The work effectively highlights the concept of subsidence, both as a natural process and as a result of human activities such as mining.By emphasizing the negative effects of subsidence on land stability, infrastructure, and community safety, the introduction underscores the urgency of addressing this issue in regions such as the Jiu Valley.
The environmental context of the Jiu Valley is essential for understanding the environmental challenges and opportunities of the region.The characterization of the valley's diverse vegetation and soil types underscores the importance of selecting appropriate tree species for afforestation initiatives.
Coal mining in the Jiu Valley elucidates the historical significance of the industry and its current challenges.15 By highlighting the environmental and societal impacts of coal mining, including subsidence and land degradation, the introduction sets the stage for proposing alternative solutions for economic development and environmental rehabilitation.
The work effectively positions afforestation with trees with high energy value such as acacia and birch as a viable solution for the rehabilitation of lands affected by subsidence in the Jiu Valley.By discussing the benefits of afforestation, including improved soil stability, enhanced nutrient cycling, and biodiversity conservation, the introduction makes a compelling case for this approach.
Finally, the paper points to the potential economic benefits of afforestation initiatives in the Jiu Valley, particularly through the use of acacia and birch wood for fuel and other purposes.
This sets the stage for further discussion in the conclusion on the long-term economic sustainability of afforestation projects.

CONCLUSION
In conclusion, subsidence, a process characterized by soil sinking naturally or due to human activities such as mining, poses significant challenges to land stability, infrastructure, and community safety.The Jiu Valley region, with its rich coal resources and industrial heritage, has been particularly susceptible to subsidence, leading to environmental degradation and socioeconomic consequences.
To mitigate the adverse effects of subsidence and rehabilitate affected areas, it is crucial to implement proactive measures such as continuous monitoring of groundwater levels, sustainable mining practices, and soil rehabilitation efforts.Additionally, the afforestation of subsidence-affected lands with high-energy value trees like acacia and birch presents a promising solution.
The proposed afforestation plan for the Jiu Valley area, organized in stages and tree groups, aims to restore ecological balance, improve soil conditions, and prevent further subsidence-related damage.By strategically planting drought-resistant species like acacia and birch, the initiative not only contributes to environmental conservation but also offers economic opportunities for the region's future.
Furthermore, the utilization of acacia and birch wood for fuel, with their high calorific values, underscores the multifaceted benefits of afforestation efforts.While acacia is prized for its slow-burning and heat-producing properties, birch offers versatility and economic value in various industries.16 In conclusion, the rehabilitation of subsidence-affected lands through afforestation represents a sustainable approach to addressing environmental challenges, promoting economic development, and safeguarding the well-being of communities in the Jiu Valley region and beyond.

The
Reintegration of The Surfaces Affected by the Phenomenon of Subsidence through the Cultivation of Trees with High Energy Value ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-17 | e06506 | 2024.
component is environmental and socio-economic Impacts.The framework elucidates the multifaceted impacts of subsidence on the environment, infrastructure, and local communities.This includes soil degradation, vegetation loss, water resource depletion, The Reintegration of The Surfaces Affected by the Phenomenon of Subsidence through the Cultivation of Trees with High Energy Value ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-17 | e06506 | 2024.6 structural damage to buildings, and displacement of populations, emphasizing the urgent need for effective mitigation measures.Subsidence can result from various factors, including natural processes such as groundwater extraction, geological faults, and land subsidence, as well as anthropogenic activities like mining, construction, and groundwater pumping.This framework outlines the role of coal mining activities as a significant driver of subsidence in the Jiu Valley region.

Figure 3
Figure 3Image from a tailing dump

The
Reintegration of The Surfaces Affected by the Phenomenon of Subsidence through the Cultivation of Trees with High Energy Value ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-17 | e06506 | 2024.8 generation of pioneer species facilitates soil and microclimate improvement, while the subsequent forest generation, particularly on lands with average to better conditions, ensures long-term afforestation and stability.The establishment duration of a forest plantation varies depending on factors such as forest species, climate conditions, and soil quality.Considering the conditions presented by the lands on the tailings dumps-characterized by mixtures of infertile rocks, unstructured composition, sandy texture, and low water retention capacity-the proposed species for the Jiu Valley area are acacia (Robinia pseudoacacia) and birch (Betula).

TheFigure 5 Figure 6
Figure 5Accacia plantation on the tailings dump

Figure 7
Figure 7The amount of trees obtained per hectare in 10 years, in adverse conditions

Figure 9
Figure 9Difference between the calorific values of the wood The Reintegration of The Surfaces Affected by the Phenomenon of Subsidence through the Cultivation of Trees with High Energy Value ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-17 | e06506 | 2024.
The Reintegration of The Surfaces Affected by the Phenomenon of Subsidence through the Cultivation of Trees with High Energy Value ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-17 | e06506 | 2024.
The Reintegration of The Surfaces Affected by the Phenomenon of Subsidence through the Cultivation of Trees with High Energy Value ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-17 | e06506 | 2024.
The Reintegration of The Surfaces Affected by the Phenomenon of Subsidence through the Cultivation of Trees with High Energy Value ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-17 | e06506 | 2024.