**4. Land use change affect soil organic carbon and ecosystem services**

Globally, there has been increased land use change from natural vegetation to agricultural land and urban areas as well as intensification of agricultural practices [33, 34]. These changes results in large increases in energy, water, and fertilizer consumption, as well as considerable losses of biodiversity [33]. The growing human population has driven both the land use change and land use intensification in order to meet global demand for food, water and energy [35]. However, conversion of forest or natural vegetation to agriculture leads to an overall loss of SOC [2, 5, 6, 19] (**Figure 1**), resulting in efforts to restore SOC in agricultural soils [36, 37]. Once soil is cultivated for agricultural production, SOM is rapidly decomposed as a result of modifications in conditions such as aeration, water content and temperature [38]. Land use change could affect soil functions that directly or indirectly relate to SOM, as a result of its capacity to retain water and nutrients as well as provide other ecosystem services [39, 40]. For example, changes in the SOC stock could result in significant impacts on the atmospheric C concentration [10]. Carbon dioxide is the main greenhouse gas responsible for global warming [41]. Soil organic C balances

#### **Figure 1.**

*Averages concentrations of soil organic carbon in semiarid Chaco and Pampa's sub-regions. Full line indicates critical thresholds proposed for temperate regions, and dashed line is for topical regions. Modified from [2].*

are associated with CO2 sequestration [36]. As a result, SOC stock is considered an intermediate ecosystem service that contributes to climate regulation [10].

Agricultural production can be increased by increasing cropland area or increasing productivity per unit area. When agricultural production increases as a result of land use change from natural cover areas to crop production agriculture, overall SOC mediated ecosystem services supply decreases [2] (**Figure 2A**). It was indicated that land use change from native forest to pasture (+8%), crop to pasture (+19%), crop to plantation (+18%), and crop to secondary forest (+53%) increased total C stocks, as well as SOC mediated ecosystem services (**Figure 2B** and **C**) whereas changes from pasture to plantation (−10%), native forest to plantation (−13%), native forest to crop (−42%), and pasture to crop (−59%) reduced total C stocks [17]. Generally, land use change from all other uses to cropping or monocultures result in losses of SOC [10]. In addition, Montgomery [42] indicated that accelerated soil erosion associated with conventional agriculture could occur at rates up to 100 times greater than the rate at which natural soil formation takes place. Additionally, peatlands have been drained for agricultural purposes [43]. Peatland store much more organic C in form of different C functional groups compared to upland. For example; in Apalachicola National Forest, the wetlands dominated by cypress (**Figure 3A**) and spikerush and water lily (**Figure 3B**) contain more alkyl, methoxyl, O-alkyl, aromatic, phenolic and carboxyl C compared to upland (**Figure 3C**). However, globally, peatland drainage causes carbon-rich peat to disappear at a rate 20 times greater than the rate at which the peat accumulated [44]. As a result, SOC affect both climate change and crop production in agricultural soils [9].

Soil management practices that sustain and enhance carbon stocks are crucial if we are to overcome near-term challenges and conserve this valuable resource for future generations. As a result of soil C loss during the past 25 years, one-quarter of the global land area has suffered a decline in productivity and the ability to provide

#### **Figure 2.**

*Relations between ecosystem services mediated by SOC versus (A), agricultural production (B), natural cover (C), SOC and (D), relationship between agricultural production and natural cover. Modified from [2].*

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

ecosystem services [39]. However, it has been observed that land use change from cropland to pasture or cropland to permanent forest results in the greatest gains of SOC [10] (**Table 1**). For example, Conant et al. [45] indicated that land use conversion from cropland to grassland improve soil carbon stocks. However, over time grassland area has been shrinking and arable land area expanding, indicating continued conversion of grassland to croplands [46]. In some cases where natural land cover has increased in expense of agricultural land cover, agricultural production

#### **Figure 3.**

*Quantification of carbon functional groups in Apalachicola National Forest; which includes (A) cypress wetlands, (B) spikerush+water lily wetlands and (C) upland.* 


#### **Table 1.**

*Changes in soil carbon concentration presented by type of management change implemented. Modified from [45].*

has been reported to decrease (**Figure 2D**). With increasing human population, this trend highlights the importance of increasing agricultural production by increasing crop yields per unit land area rather than expanding cropland and/or pasture over natural areas [2].
