# A Review on Carbon Source and Sink in Arabic Land Ecosystems
###### Abstract  
Arable land ecosystems are among the most important terrestrial systems. The issues of carbon sequestration and emission reductions in arable land ecosystems have received extensive attention. Countries around the world have actively issued policies to manage arable land ecosystems. At present, more than 100 countries have made carbon neutralization target commitments. Various arable land management measures and arable land planting strategies have important impacts on the carbon storage of arable land ecosystems. Research on arable land carbon is of great significance to global climate change. This study attempts to investigate the problems and deficiencies in the current research by summarizing a number of studies, including the main methods for the quantitative research of carbon sources and sinks as well as the influencing factors in these ecosystems. In this study, it is found that due to the differences of climate patterns, soil properties and management practices in arable land ecosystems, the factors affecting carbon sources and sinks are of great heterogeneity and complexity. Generally, variations in natural factors affect the carbon balance in different regions, while human management measures, such as irrigation, fertilization and the degree of agricultural mechanization, are the leading factors causing changes to carbon sources and sinks in these ecosystems. In addition, there are still great uncertainties in the evaluation of carbon sources and sinks in these ecosystems caused by different estimation models and methods. Therefore, emphasis should be placed on model parameter acquisition and method optimization in the future. This review provides a scientific basis for understanding carbon sources and sinks in arable land ecosystems, enhancing their carbon sink capacity and guiding low-carbon agriculture on arable land. a 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 20222 2022 20222 study showed that CO\({}_{2}\), N\({}_{2}\)O and CH\({}_{4}\) contribute 60%, 5% and 15% to global warming, respectively, and about 5%-20% of CO\({}_{2}\) comes from soil every year [7]. Therefore, global warming has become the main focus of global climate change research [8; 9]. Forests contain 2-4 times more carbon per unit area than arable lands [8], and thus many scholars have paid more attention to the carbon sequestration capacity of forest ecosystems [10; 11]. It has been generally believed that compared with forest and grassland ecosystems, arable land ecosystems were a weaker carbon source or carbon sink and less valuable to the global carbon cycle, and therefore there has been less research on arable land ecosystem carbon-source and sink activities. However, a study of terrestrial ecosystems in the Northern Hemisphere found that forest and arable land ecosystems had significantly higher gross primary production (GPP) and net ecosystem productivity (NEP) than grassland and wetland ecosystems [12], indicating an important role for arable land ecosystems in climate-change mitigation. Arable land accounts for 37% of the earth's land area and is a main source of agricultural greenhouse-gas emissions [13], accounting for 30% of global emissions (direct and indirect), and has become an important part of any climate change adaptation and mitigation agenda [14]. Arable land ecosystems play a dual role in climate change. Large-scale farming and excessive use of chemical fertilizers and pesticides lead to a large amount of carbon loss and accelerate climate warming [15; 16]. It is estimated that overall soil organic carbon (SOC) has decreased by 3% since the beginning of large-scale planting in the 19 th century [17]. In Brazil, land-use changes caused by agriculture accounts for more than 2/3 of the country's total carbon emissions [18]. In Australia's agroecosystems, tillage has led to carbon loss for more than 40 years, and the total carbon loss on 10 cm topsoil is about 51% [19].