Variable response of inorganic carbon and consistent increase of organic carbon as a consequence of afforestation in areas with semiarid soils

Abstract

Soil inorganic carbon (SIC) is the most common form of carbon in arid and semiarid regions, where afforestation is used to combat soil degradation. However, response of SIC to afforestation has been studied rarely, which hinders any prediction about soil carbon dynamics. To determine the response of SIC and soil organic carbon (SOC) to afforestation in semiarid soils and whether such responses vary with soil aggregates, soil texture, and climatic conditions, we measured SIC and SOC in bulk soils and aggregate fractions under paired afforested lands and farmlands at five sites across the Loess Plateau. The relationship of these responses to soils and climatic variables was analyzed. Afforestation increased SOC at all sites, with accumulation rates of 0.21, 0.23, 0.34, and 0.09 g kg −1 yr −1 in bulk soils, macroaggregates (>0.25 mm), microaggregates (0.25-0.053 mm), and silt + clay fraction, respectively, when averaged across sites and soil depths. However, the response of SIC to afforestation varied with site, with increased SIC in drier sites and decreased SIC in wetter sites. Change in SIC was negatively correlated with change in SOC either across or within bulk soils and aggregate fractions. The SIC decreased and SOC increased with increasing soil clay content, precipitation, temperature, and site aridity index. These results indicated consistent increase in SOC but variable response of SIC to afforestation among sites in the Loess Plateau. Such variable response of SIC should be incorporated into carbon cycle models to reduce uncertainties when predicting sequestration dynamics of soil carbon.

CO2 emission affected by moisture content and aggregate sizes in a calcareous soil of Comarca Lagunera, Mexico

“…Values obtained for BD, FC and PWP of the calcareous soils of the Comarca Lagunera (Table 2) are similar to those previously reported by Inzunza-Ibarra et al (2018). Distribution of soil aggregates shows that 60.4 % of total soil aggregates ≤0.25 mm (Table 3), which is associated with the low content of SOC that prevents the existence of organic binding agents (Qiu et al, 2015;Jia et al, 2019). This aggregates size (≤0.25 mm) is considered by Chepil (1953) as a highly wind-erodible fraction.…”

Contrasting Responses of Soil Inorganic Carbon to Afforestation in Acidic Versus Alkaline Soils

“…Fang & Chen, 2001;Laganière et al, 2010). However, it remains poorly understood how afforestation may influence SIC (Jia et al, 2019).…”

The Contribution of Biotic Factors in Explaining the Global Distribution of Inorganic Carbon in Surface Soils

“…The highly spatial variations in topsoil SIC found here are likely to be related to distinct climatic characteristics across continents. For example, Asia, Europe, and Australia surveyed are predominantly characterized by arid and temperate climatic conditions, which have been considered favorable for SIC accumulation (Jia et al., 2019; Tao et al., 2022; Wang et al., 2019). Warmer and drier arid and temperate areas typically favor the accumulation of base cations (e.g., Ca 2+ ), which can promote the formation of pedogenic carbonates (Naorem et al., 2022).…”