Core Ideas
Topsoil SIC storage decreased with restoration age, but subsoils were unchanged.
SOC was the main driving force of SIC storage in the topsoil.
Sand and silt contents were the controlling factors of SIC storage in subsoils.
Soil total C storage remained stable across the restoration sequence.
Soil inorganic C (SIC) comprises approximately a third of the global soil C pool, which plays an important role in global C cycling. However, there is still considerable disagreement on the direction and magnitude of changes in SIC stocks following vegetation restoration. We conducted a study comparing SIC at different succession stages along a 150‐yr natural vegetation restoration chronosequence to examine the effect of long‐term natural vegetation restoration on the distribution of SIC and to identify the factors that control changes in SIC. The results showed that SIC storage in the top 10 cm gradually decreased (0.092 Mg ha−1 yr−1) along the vegetation restoration chronosequence but was basically unchanged in the subsoil (10–100 cm). The soil total C storages remained stable across the restoration sequence, with the redistribution of the total soil C pool from SIC to soil organic C (SOC) the dominant forms. The controlling factors of SIC were different in the top‐ and subsoils along the chronosequence. In the top 30‐cm soil layers, SOC was a good predictor of SIC; however, for soils below 30 cm, soil sand and silt contents and pH were better predictors of SIC. Therefore, we can conclude that the variations in SOC induced by vegetation restoration were the main driving force for SIC changes in the topsoil, while the genetic soil features (i.e., sand and silt contents) were the controlling factors that determined the amount of SIC in the subsoil.
The capacity of soil and water conservation measures, defined as the maximum quantity of suitable soil and water conservation measures contained in a region, were determined for the Loess Plateau based on zones suitable for establishing terraced fields, forestland and grassland with the support of geographic information system (GIS) software. The minimum possible soil erosion modulus and actual soil erosion modulus in 2010 were calculated using the revised universal soil loss equation (RUSLE), and the ratio of the minimum possible soil erosion modulus under the capacity of soil and water conservation measures to the actual soil erosion modulus was defined as the soil erosion control degree. The control potential of soil erosion and water loss in the Loess Plateau was studied using this concept. Results showed that the actual soil erosion modulus was 3355 tkm -2 a -1 , the minimum possible soil erosion modulus was 1921 tkm -2 a -1 , and the soil erosion control degree was 0.57 (medium level) in the Loess Plateau in 2010. In terms of zoning, the control degree was relatively high in the river valley-plain area, soil-rocky mountainous area, and windy-sandy area, but relatively low in the soil-rocky hilly-forested area, hilly-gully area and plateau-gully area. The rate of erosion areas with a soil erosion modulus of less than 1000 tkm -2 a -1 increased from 50.48% to 57.71%, forest and grass coverage rose from 56.74% to 69.15%, rate of terraced fields increased from 4.36% to 19.03%, and per capita grain available rose from 418 kga -1 to 459 kga -1 under the capacity of soil and water conservation measures compared with actual conditions. These research results are of some guiding significance for soil and water loss control in the Loess Plateau.
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