Statement of problem
Climate change is a pressing global issue that transcends national borders, defined as a significant alteration in climate patterns lasting for decades or more According to the United Nations Framework Convention on Climate Change, it results from human activities that modify the composition of the atmosphere, contributing to both natural and anthropogenic climate variations Key consequences include global warming, rising sea levels due to ice melt, and shifts in atmospheric conditions, all exacerbated by human actions such as urbanization, increased food demand, and deforestation This disruption of ecosystems has led to severe environmental consequences, including natural disasters and health crises, as evidenced by the melting polar ice caps and frequent tsunamis affecting numerous countries.
As climate change impacts various sectors, it is crucial to identify effective coping strategies Recent global research has revealed that soil possesses a significant yet often overlooked characteristic that plays a vital role in addressing these environmental challenges.
"The ability to sequester carbon, reduce greenhouse gas emissions" [75]
With approximately 830 billion tons of carbon currently in the atmosphere and an additional 10 billion tons released annually by human activities, the role of soil in carbon storage becomes crucial, as it can hold 4,800 billion tons—six times more than the air According to Cornell University co-author Johannes Lehmann, effective land management technologies can significantly reduce atmospheric carbon levels Therefore, understanding the relationship between carbon and agricultural land use is vital, particularly in Vietnam, as it informs strategies for carbon accumulation and helps optimize land use planning to protect the environment and combat climate change.
Land, with carbon reserves of approximately 1,500 billion tons, serves as the world's second-largest carbon sink, holding twice the atmospheric carbon and three times the carbon found in global ecosystems It plays a crucial role in the global carbon cycle In our country, participation in the REDD+ program has led scientists to conduct extensive research on carbon accumulation in various ecosystems and land use types, aiming to secure financing through carbon sequestration environmental services Despite numerous studies, guidelines for assessing national carbon stocks have primarily focused on forest soil, leaving a gap in understanding carbon stocks in other agricultural land uses.
The global strategy for addressing climate change now emphasizes adaptation measures that operate at both regional and global levels This approach focuses on implementing land management technologies to effectively reduce greenhouse gas emissions and significantly lower atmospheric carbon levels.
Bo Trach district, located in Quang Binh province, is an emerging area characterized by a diverse land use structure It is home to the Phong Nha - Ke Bang National Forest, which boasts a rich ecosystem and serves as a vital green lung for the region, playing a crucial role in climate regulation and mitigation As of December 31, 2019, the district encompasses a total natural area of 211,549.10 hectares, featuring various types of land use.
In recent years, the conversion of agricultural land use types in Bo Trach district has significantly impacted carbon accumulation and exacerbated climate change effects This research aims to assess the carbon accumulation capacity of various agricultural land use types while examining recent changes in land use Understanding these dynamics is crucial for effective land use planning and enhancing soil carbon storage, ultimately contributing to climate change mitigation efforts.
Research Objectives
The study evaluated the carbon accumulation potential of various agricultural land uses in Bo Trach district, Quang Binh province, aiming to enhance land use efficiency, reduce CO2 emissions, and mitigate climate change.
Scientific and practical significance
The research findings enhance the theoretical framework for climate change mitigation and adaptation, serving as a valuable resource for policymakers They aim to improve technical capacity, manage land resources effectively, and develop predictive models for land use processes Additionally, the study deepens the understanding of the interplay between carbon accumulation and land use change, further elucidating the connections among carbon dynamics, land use alterations, and climate change.
The study of carbon accumulation capacity across various land use types in Bo Trach district, Quang Binh province, aims to accurately evaluate the carbon sequestration potential of each land use category By identifying which land use practices are most effective in carbon accumulation, the findings will assist local authorities in formulating a comprehensive land use plan for 2030 This plan will not only facilitate socio-economic development but also contribute to climate change mitigation efforts.
New contribution
The thesis presents a comprehensive analysis of carbon accumulation capabilities across various agricultural land uses, utilizing fieldwork alongside GIS and remote sensing technologies It culminates in a detailed map depicting the distribution of carbon stocks, allowing for an evaluation of which soil types exhibit the highest potential for carbon sequestration.
- Forecasting the change of agricultural land use by Markov chain to
2030 to assess the potential for carbon accumulation in the future in Bo Trach district, Quang Binh province.
LITERATURE REVIEW
THEORICAL BASIS OF THE RESEARCH
This thesis explores key aspects of agricultural land use, focusing on biomass and carbon accumulation, as well as the application of GIS and remote sensing techniques in analyzing land use changes Additionally, it models land use change to predict future patterns, thereby enhancing the theoretical framework for related research topics.
PRACTICAL BASIS OF THE RESEARCH
The study examines land use changes and carbon accumulation across various land use types globally and in Vietnam over recent years Its objective is to clarify these issues and offer substantial insights for practical applications.
This article synthesizes and analyzes research related to the thesis from esteemed scientists worldwide, with a particular emphasis on Asia and neighboring countries It presents global research findings across various continents while also detailing studies conducted in different regions of Vietnam.
Research on carbon accumulation in various land uses has primarily focused on specific tree species and localized studies, revealing a gap in comprehensive evaluations of land use's overall capacity to mitigate and adapt to climate change Notably, there is a lack of studies pertaining to Bo Trach district in Quang Binh province This thesis aims to investigate the carbon accumulation potential of different agricultural land uses, addressing an essential research gap By emphasizing sustainable practices, this study aligns with the growing need to balance economic efficiency with environmental preservation, ultimately influencing land use planning to enhance both carbon sequestration and climate change resilience.
RESEARCH SITES, CONTENTS AND
RESEARCH SITES AND SUBJECTS
This study was conducted at Bo Trach district, Quang Binh province by collecting secondary and socio-economic data during the period 2005-2018
Research focuses on assessing the ability to accumulate carbon in 3 main groups of agricultural land, including: (1) Land for annual crops;
The study examines land designated for perennial crops and production forests in Bo Trach district, where the predominant tree species are similar, prompting their evaluation as a combined category Additionally, it investigates natural forest land and employs the Markov model to forecast changes in agricultural land use by 2030 This analysis aims to assess the potential for future carbon accumulation in the region.
RESEARCH CONTENTS
- Characteristics of natural, socio-economic conditions and land use structure of Bo Trach district, Quang Binh province
- Changes in agricultural land use area during the period 2005-2018 in Bo Trach district, Quang Binh province
- Evaluation of carbon accumulation capacity of some types of agricultural land use in Bo Trach district
- Forecast of changes in agricultural land use to 2030 in Bo Trach district
- Proposing solutions to use land to increase carbon carbonity in Bo Trach district, Quang Binh province.
RESEARCH METHODOLOGY
The study involves gathering essential documents and data regarding natural and socio-economic conditions, including a current land use map at a 1:50,000 scale, along with relevant statistics and land inventory from the provincial Department of Natural Resources and Environment and the Bo Trach District's Department Additionally, remote sensing images from SPOT captured in 2005 and 2010, as well as Sentinel images, will be collected to support the analysis of the study area.
In 2018, two images were captured in the research area, complemented by Landsat images for thorough inspection and comparison The accuracy of these results was assessed, with the photographs taken during the dry season in May and June, characterized by sunny weather and minimal cloud cover, facilitating effective image interpretation.
This study utilized sampling data for image interpretation and accuracy evaluation, focusing on the Bo Trach district Samples were systematically selected across the entire territory through observation methods and expert interviews to ascertain the type and scale of samples The Garmin eTrex 10 GPS device was employed to accurately locate the investigation sites, which were crucial for assessing biomass and carbon reserves associated with different land use types during the survey Additionally, photographs of the survey locations were taken to provide reliable references for refining the interpretation method In total, 166 standard plots were established to represent various agricultural land use types within the study area.
To effectively interpret satellite images using eCognition software, it is essential to determine the threshold for each class by calculating the brightness values across four spectrum channels: Red, Green, Blue, and Near Infrared Additionally, the analysis incorporates other classification categories such as Brightness, NDVI (Normalized Difference Vegetation Index), and RIV (Ratio Vegetation Index) to enhance image classification accuracy.
NDVI = (NIR - Red) / (NIR + Red)
In which: NIR is the radiation value of near infrared, Red is the radiation value of the visible wavelength
From the statistics of image samples, mathematical methods were applied to find threshold values to classify of image objects
Figure 2.4 The process of interpreting remote sensing images in the study area
Figure 2.5 Logical framework for calculating forest canopy surface biomass from remote sensing images 2.3.4 GIS application method
Using ArcGIS 10.3, we created various maps, including the current map, NDVI map, LAI index map, biomass map, and carbon map, based on analyzed data from the study area GIS tools were employed to analyze and calculate canopy cover from standard plots derived from photographs taken during field trips, supporting the research process effectively.
Figure 2.7 The process of applying GIS to create a map of land use change 2.3.5 Method of forecasting land use change using Markov chain
It is a modeling process that uses spatial information as input data
Utilizing data types, we can generalize and simulate real-world scenarios through specific mathematical functions The spatial information simulation provides visual representations and insights into the movement and change patterns of real objects This study employs the Markov and CA-Markov modules in IDRISI software to model land use changes in Bo Trach district, using standardized input data for both attributes and spatial dimensions.
Some methods of collecting original data have either not been processed or failed to meet research requirements Consequently, these data types will be analyzed and processed using SPSS statistical software and Microsoft Excel Specifically, SPSS 20 will be employed to examine the relationship between the NDVI index from the imagery and the actual LAI index, with NDVI serving as the independent variable and LAI as the dependent variable.
RESULTS AND DISCUSSION
CHARACTERISTICS OF SOCIO-ECONOMIC, NATURE AND
3.1.3 Assessment of natural and socio-economic characteristics
3.1.4 Land use structure in Bo Trach district
3.1.4.1 The current status of agricultural land use
Bo Trach district's land use statistics reveal that agricultural land covers 196,673.24 hectares, making up 92.97% of the total area This includes 28,206.64 hectares of agricultural land (13.33%), 167,035.24 hectares of forestry land (78.96%), and 1,338.59 hectares for aquaculture (0.63%) Non-agricultural land comprises 11,398.26 hectares, or 5.39% of the area, which includes residential land (1,418.44 ha), specialized land (6,444.62 ha), religious land (14.36 ha), belief land (11.43 ha), and land for cemeteries and crematoriums (736.13 ha) Additionally, waterways account for 2,459.48 hectares (1.16%), while specialized water surface land covers 313.80 hectares (0.15%) Unused land totals 3,477.38 hectares (1.64%), including unused flat land (1,878.30 ha), unused hilly land (227.61 ha), and rock mountains without forests (1,371.47 ha).
Figure 3.2 Land use structure in 2018 of Bo Trach district
3.1.4.2 Changes in land use structure in the district
Table 3.3 Structure and land area of Bo Trach district in the period 2005-
Thus, it can be seen that in a period of 13 years, Bo Trach district from
Between 2005 and 2018, urbanization in Bo Trach district significantly altered land use patterns, resulting in a notable decrease in agricultural and unused land This transformation facilitated the conversion of these areas into non-agricultural land to meet the district's growing urban development needs.
CHANGES IN LAND USE AREAS DURING THE PERIOD 2005-
Figure 3.3 Samples collected for interpretation
The land use cover maps of Bo Trach district for the years 2005, 2010, and 2018, created using eCognition software, are illustrated in Figures 3.4, 3.5, and 3.6 Additionally, Table 3.5 provides statistical data on the total area of land use changes observed during this period.
Types of land use 2005 (ha) 2010 (ha) Increase (+) Decrease (-)
ASSESSMENT OF CARBON CARBONITY OF SOME TYPES
Types of land use 2010 (ha) 2018 (ha) Increase (+) Decrease (-)
Between 2005 and 2018, the analysis of land use changes in Bo Trach district revealed a significant increase in the area dedicated to perennial crops and production forests, while natural forest areas experienced the largest decline This trend was particularly pronounced during the 2005-2010 period However, from 2010 to 2018, there was a notable shift, with agricultural land groups undergoing internal conversions and a sharp increase in conversions to other land types The purpose of this analysis was to identify which land groups have undergone the most significant changes in recent years and to assess their potential impact on soil carbon accumulation capacity, highlighting the differences among these groups.
3.3 ASSESSMENT OF CARBON ACCUMULATION OF SOME TYPES OF AGRICULTURAL LAND USE IN BO TRACH DISTRICT
3.3.1 Characteristics of types of agricultural land use
3.3.2 Determination of biomass of actual land use types
Table 3.8 LAI ratio of land group for perennial crops and production forests
Land for perennial crops & Production forests
Table 3.9 LAI ratio of annual crops land
Table 3.10 LAI ratio of natural forest land
Field results indicate that the difference in LAI values between natural forest land types is minimal This is attributed to the natural forest's extended development period and its growth across diverse areas, which are largely untouched by human activity, resulting in high vegetation coverage.
3.3.3 Determination of biomass of some land use types from remote sensing images
3.3.3.2 Calculating indexes from remote sensing images for biomass calculation
Figure 3.12 A thumbnail image of the NDVI vegetation difference index map
Table 3.12 NDVI index information in standard cells
In Bo Trach district, the NDVI values range from a minimum of 0.311 for perennial crops and production forests in standard plot 10 to a maximum of 0.877 for natural forest land in standard plot 62 The average NDVI value is 0.69, with a standard deviation of 0.12, indicating variability in vegetation health across different land types.
The LAI index map, derived from Sentinel satellite images, illustrates the leaf area index in Bo Trach district, highlighting the ratio of tree canopy leaf surface area to the land surface area occupied by annual plants This data is crucial for understanding vegetation dynamics and land use in the region.
Min 40,00 44,74 -15,63 -17,36 Land for planting perennial crops and production forests
Table 3.14 Ratio of leaf surface area of tree canopy to land surface area of perennial crops and production forests developed in Bo Trach district
Percent = Actual difference / LAI Type
Table 3.15 Ratio of leaf surface area of tree canopy to land surface area of natural forest type developed in Bo Trach district
Table 3.15 reveals that the average Leaf Area Index (LAI) from field surveys is closely aligned with the LAI derived from images, measuring 89.12% and 88.29%, respectively The calculation of actual LAI against image LAI shows a standard deviation error of approximately 2.42%, indicating that biomass calculations can achieve an impressive accuracy of 97.58%.
Figure 3.14 Thumbnail image of the fAPAR distribution map of Bo Trach district Table 3.16 Table of fAPAR indicators at standard plot points
Value NDVI T on photo FAPAR
The average absorbed radiation for photosynthetic activity (FAPAR) across the study area is 0.665, indicating that 66.5% of solar radiation in the visible light spectrum is utilized for biomass generation Additionally, there is a positive correlation between the NDVI index and FAPAR, with an R² value of 0.5185, suggesting that higher NDVI values correspond to higher FAPAR values.
Figure 3.15 Correlation chart between NDVI index and fAPAR
3.3.4 Mapping biomass and carbon reserves of agricultural land use types in Bo Trach district
3.3.4.1 Determination of biomass value of different types of agricultural land use
Figure 3.16 Thumbnails of biomass hierarchical maps of agricultural land use types in Bo Trach district
The analysis of the biomass value map across various land use types reveals that annual cropland has the lowest biomass value, while natural forest land exhibits the highest Additionally, certain areas, such as coastal white sand dunes and urban zones with concrete structures, show no biomass presence, indicated by negative values.
3.3.4.2 Evaluation of the results of calculating the biomass of different types of agricultural land use in Bo Trach district
The study reveals that the mean square error between calculated biomass values and those determined through remote sensing images is approximately 41.67 tons/ha, primarily due to the significant biomass present in natural forests, which can lead to greater discrepancies The standard error for biomass calculations based on remote sensing images is around 10.35%, indicating an accuracy rate of 89.65% This level of accuracy is deemed acceptable, suggesting that remote sensing methods can effectively be utilized for the rapid assessment of biomass and carbon reserves, aiding in environmental planning and conservation efforts.
3.3.4.3 Establishing carbon maps in Bo Trach district, Quang Binh province
Figure 3.17 Miniature image of Carbon maps in Bo Trach district Table 3.20 Carbon value of perennial crops and production forests
Table 3.21 Carbon value of annual crops land
Table 3.22 Carbon value of natural forest land
The final outcome of the study is a carbon value map tailored to various agricultural land use types in Bo Trach district, achieved by aligning each carbon map with the respective land use boundaries This significant finding is illustrated in Figure 3.18.
Figure 3.18 Miniature image of the carbon map of agricultural land use types in Bo Trach district
The carbon value analysis reveals that natural forest land has the highest carbon accumulation, ranging from 152.45 tons/ha to 306.22 tons/ha, with an average of 239.30 tons/ha Following this, perennial crops and production forests exhibit a significant carbon value, with figures between 14.45 tons/ha and 36.95 tons/ha, averaging 28.79 tons/ha In contrast, land designated for annual crop cultivation shows the lowest carbon value, ranging from 7.02 tons/ha to 9.45 tons/ha, with an average of just 8.44 tons/ha.
T able 3.23 Statistics on the area of agricultural land use types and carbon value in Bo Trach district
Types of land use 2010 (ha) 2018 (ha)
Average value of Carbon (Ton/ha)
Natural forest land exhibits the highest average carbon value among the studied soil groups, with 239.30 tons per hectare However, this area has experienced a significant decline of over 6,184.09 hectares from 2010 to 2018 Key regions with substantial carbon reserves in natural forest land include Hung Trach, Thuong Trach, Son Trach, and Tan Trach communes Forests act as vital carbon reservoirs, absorbing atmospheric carbon, with some carbon cycling back into the atmosphere while others enter the food chain or remain in the soil Soil carbon tends to be stable over extended periods, highlighting the importance of forest protection and cover in enhancing carbon accumulation and combating climate change.
FORECAST FOR THE CHANGE OF AGRICULTURAL LAND
3.4.4.1 Application of automatic network and Markov chain to model land use change in Bo Trach district
3.4.4.2 Modeling land use change in Bo Trach district to 2030 a Forecast of land use change to 2018
Based on the input data of Spot 5 satellite images in 2005 and 2010, the
The CA-Markov model effectively forecasts land use changes in Bo Trach district up to 2018 By utilizing four hierarchical maps and a development zoning restriction map as constraints, the project successfully generated modeling results, illustrated in Figure 3.22.
In 2018, a land use forecast map for Bo Trach district was created, as illustrated in Figure 3.22 Additionally, Table 3.30 presents a comparison of the model's prediction results alongside the actual numerical data of the classification and land use system, measured in hectares (ha).
Types of land use Forecast results 2018
& Production forests 41.086,1 40.818,64 39.265,96 Natural forest land 137.078,1 137.739,6 139.348,12
Other lands 14.766,9 15.821,49 15.787,58 b Forecast of land use change to 2030
Figure 3.27 Thumbnail image of the map of land use change forecast in Bo
Table 3.33 Statistics on total area of land use types in 2005 and forecast in 2030
3.4.5 Comparing forecast results with results of land use planning and socio-economic development orientation of Bo Trach district
3.4.5.1 Socio-economic development plan of Bo Trach district
The land use forecast for 2030 aligns closely with the district's 5-year development plan (2021-2025), indicating a decline in agricultural land as the goal is to reduce agricultural labor to below 50% Concurrently, the area designated for production forests is expected to rise, supporting the district's aim to increase forest cover to nearly 70%, particularly through planted forests Additionally, there is a projected growth in the service and industrial sectors, reflecting the shift towards non-agricultural land use This forecast model demonstrates that the district's development strategy is progressing in harmony with anticipated trends, affirming the alignment of the 5-year plan with the 2030 vision.
3.4.5.2 Land use planning in 2030 in Bo Trach district
Table 3.34 Comparison of forecast results and land use planning of
No Types of land use
Table 3.35 The relationship between the forecast results and the mean carbon value of agricultural land uses in Bo Trach district
Average value of carbon in
Annual crop land 18.617,78 16.801,08 -1.816,7 8,44 Land for perennial crops & Production forests
Natural forest land 137.078,10 137.012,6 -65,5 239,30 Through the results of the forecast of land use change in Bo Trach district, the group of perennial crops & production forests to have is forecasted to
By 2030, significant reductions in land area are anticipated, particularly affecting perennial crops and production forests, which currently rank second in carbon accumulation capacity after natural forests This decline in land resources is likely to impact the carbon sequestration potential of these ecosystems Additionally, research indicates that annual crops also possess a notable ability to accumulate carbon; however, similar to perennial crops, the area designated for annual crops is expected to decrease substantially in the future.
In 2018, it is projected that the reduction of natural forest land will be minimal compared to other soil types This is significant for mitigating climate change and safeguarding land resources, as natural forests possess a high capacity for carbon accumulation.
PROPOSING SOLUTIONS TO USE LAND TO INCREASE
Natural forests are the most effective at accumulating carbon biomass, yet from 2005 to 2018, their area significantly declined due to the conversion of poor forests into plantations for raw materials like rubber and fruit trees, aimed at enhancing economic efficiency and living standards for local communities Despite this reduction, Quang Binh province and Bo Trach district must focus on improving forest quality through policies that close off and allocate forests to organizations and individuals for proper zoning and protection This approach will enhance carbon accumulation while supporting the district's socio-economic development goals.
The group of soils designated for planting production forests and perennial crops demonstrates significant carbon accumulation capacity, second only to natural forest land While their carbon storage is not as extensive as that of natural forests, these soils cover a substantial area in mountainous regions State policies, particularly land lease regulations, have heightened land users' focus on the economic value per unit area, leading to increased investment in advanced science and biotechnology Key crops such as rubber, acacia, melaleuca, and various fruit trees are cultivated, all of which possess high carbon accumulation potential This approach not only enhances biomass accumulation but also fosters stable economic growth through commodity agriculture and the deep processing industry.
Implementing a diverse agroforestry system that integrates tree planting with annual crops and livestock can significantly enhance carbon sequestration compared to traditional farming methods By selecting appropriate land cover crops, practicing crop rotation, and utilizing organic fertilizers or manure, farmers can create a more sustainable agricultural environment This approach not only minimizes competition among plants through strategic spacing of timber or fruit trees alongside annual crops but also increases overall productivity When executed effectively, these systems can surpass the yields of monocultures, promoting greater food production while alleviating deforestation pressures, which are a major factor in reducing soil carbon accumulation.
CONCLUSIONS
The results were obtained from this research as follows:
1) The results show that there is a strong variation in land use types in
Between 2005 and 2010, Bo Trach district experienced significant growth in the area dedicated to perennial crops and production forests, increasing by approximately 10,763.91 hectares From 2010 to 2018, this trend continued, with an additional rise of about 4,970.85 hectares for these crops, while natural forests saw a sharp decline of around 6,184.09 hectares This shift underscores the region's economic development strategy, which prioritizes agricultural advancement and reflects the broader economic restructuring that has altered land use patterns in the area.
2) The results of the assessment of carbon accumulation capacity of agricultural land uses in Bo Trach district show that the carbon value of natural forest land is the largest, reaching from 152.45 tons/ha to 306.22 tons/ha, average 239.30 tons/ha Next, land for perennial crops & production forests has the second highest value of carbon accumulation with value from 14.45 tons/ha to 36.95 tons/ha, averaging 28.79 tons/ha The soil group with the lowest carbon value in the region is the land for growing annual crops, which is only 7.02 tons/ha - 9.45 tons/ha, with an average of 8.44 tons/ha The determination of biomass and carbon stocks of perennial crops not only contributes to reducing emissions and responding to climate change, but also provides a scientific basis and facilitates the adjustment of land use planning land use in the future to improve the ability to accumulate carbon in the soil towards limiting climate change
3) The results of forecasting the trend of land use change in the period 2005-2030 in Bo Trach district show that the type of natural forest land use tends to decrease sharply, the variation decreases by 12,977.31 hectares, in which land for planting perennial crops and production forests tends to increase sharply, with an increase of 11,530.12 ha The type of strong and relatively complicated fluctuations is other lands (including residential land, transportation, irrigation, trade, services, land of rivers, streams, canals, streams, unused land ) The results of the model have been verified with the results of the district's land statistics, with the classification results from the images, with the district's socio- economic development plan and compared with the results of the land use planning to the end of the year The year 2030 shows similarities and is consistent with the development orientation of the district
4) From the research results, groups of solutions to increase the capacity of carbon accumulation according to each type of land use and each specific region in Bo Trach district have been proposed With these solutions, Bo Trach District People's Committee will have a basis to use land effectively to increase the ability to accumulate carbon to cope with climate change.