**1. Introduction**

The basis and essence of life on earth depends on soil health, and its main indicator is soil organic carbon (SOC) content [1, 2]. Soil health has been defined as the capacity of a soil to support ecosystem functions and sustain environmental quality and biological productivity, while promoting plant and animal health [3]. Through plant growth, soil health is connected with the health of humans, animals, and ecosystems within its domain [4]. The SOC is an indicator of soil health and is an important component of the soil ecosystem [5, 6]. Deb et al. [7] indicate that the presence of organic carbon (OC) in soil is a key determinant for soil quality and productivity. In addition, organic matter is a key influencer on physical, chemical, and biological soil attributes [8]. The SOC stock exhibit the long-term balance between additions of OC from different sources and its losses through different pathways [9].

The term SOC is defined as C in soil derived from organic origins and soil organic matter (SOM) is generally considered to contain approximately 58% SOC. Soil organic matter is a mixture of materials including particulate organics, humus, fine plant roots, living microbial biomass as well as charcoal [10]. Two words have commonly been used in reference to SOC; C sequestration and C storage. Carbon sequestration is the process of transferring carbon dioxide (CO2) from the atmosphere into the soil which can be achieved through plants, plant residues and other organic amendments which are retained in the soil as part of SOM [10, 11]. Carbon sequestration in soil can range from short-term to long-term [12]. However, carbon storage in soil is defined as increase in SOC stocks over time, but it is not necessarily associated with a net removal of CO2 from the atmosphere [12]. Soil storage of OC for longer time periods is preferable in terms of greenhouse gases mitigation, however, mineralization of SOC is important in terms of soil fertility [12, 13]. Soil health reflects the capacity of a soil to support both the agricultural production and provision of other ecosystem services [14]. Therefore, evaluation of soil health is essential because soil is a critically important component of the earth's biosphere whose, functionality is critical in the production of food and fiber as well as maintenance of environmental quality [15, 16].

In the soil profile, approximately 615 Gt of OC is stored in the top 20 cm, 1500 Gt of OC stored in the first meter, and 2344 Gt of OC is stored in the top three meters of soil [17, 18]. However, approximately 9 Gt C is anthropogenically released to the atmosphere annually from fossil fuel sources and ecosystem degradation [10]. Previous studies have illustrated that conversion of forest or natural vegetation to agriculture leads to an overall loss of SOC [5, 6, 19]. Through soil supply of plant macro and micronutrients, soil health, mediated by SOC dynamics is a major determinant of global food and nutritional security [4]. The projected increase of human population by 2050 will double food demand and put immense pressure on natural resources [20]. Therefore, one of the greatest challenges will be to increase food production by maintaining ecosystem services [21].

#### **2. Importance of soil organic carbon**

Soil organic C provides ecosystem services that are essential to human wellbeing for example climate regulation, water supplies and regulation, nutrient cycling, erosion protection and enhancement of biodiversity [2, 22–24]. In addition, SOC exerts an influence on many soil properties, for example water holding capacity, aggregate stability, total nitrogen, pH and cation exchange capacity [5, 6]. Increasing SOC can mitigate GHG emissions, benefit agricultural productivity through improvements in soil health, and improve environmental quality [25].

Under long-term management practices SOC pools influence soil quality, C sequestration pathways, and crop productivity [9]. It has been demonstrated that high SOC levels can enhance soil fertility and health, improve water infiltration, improve soil structure, enhance moisture retention and increased crop yield [26, 27]. A positive relationship has been reported between SOC content and soil nutrient status and crop yield [28, 29]. Since SOC content influences almost all soil functions and it is easily measurable, it can be a suitable indicator of the soil capacity to supply ecosystem services [22, 23].

#### **3. Effects of climatic conditions on soil organic carbon**

Generally, SOC stocks increase with decreasing mean annual temperature [30], whereby, cold, humid climatic regions exhibit C rich soils [31]. Decomposition

*Land Use Change Affects Soil Organic Carbon: An Indicator of Soil Health DOI: http://dx.doi.org/10.5772/intechopen.95764*

releases to the atmosphere most of the C added to the soil through litter deposition, only a limited fraction becomes humus [10]. Both moisture and temperature influence the rate of litter decomposition through their effects on microbial activity [32]. In addition, both moisture and temperature also exhibit strong control of humus decomposition [10].
