The effects of long-term vegetation cover changes on the carbon fractions in soil aggregates of Mollisols
Zhang Yihe Han Xiaozeng You Mengyang Hao Xiangxiang
Chin J Plant Ecol. 2019, 43 (7):
Related Articles |
Aims Soil aggregate is the main habitat for decomposition and transformation of soil organic carbon (SOC). It’s the key to regulate SOC sequestration. The stability mechanisms of SOC fractions may vary among different aggregate sizes. The aims of this study are to explore the SOC “fractionation” characteristics of aggregates, and to reveal the C sequestration mechanisms within soil aggregates after 31-year different vegetation cover in Mollisols.
Methods A long-term field vegetation cover experiment (grassland, farmland and bare land) was established in Hailun Station of Chinese Academy of Sciences. Soil aggregate fractionation, further density and humus fractionation within different aggregate sizes were carried out.
Important findings The results showed that after 31 years of grassland (GL), farmland (FL) and bareland (BL) treatments, the surface SOC and total nitrogen (TN) contents in GL with higher C inputs increased significantly, while the SOC and TN contents decreased in FL and BL, and significance were found in BL. The 2–0.25 mm aggregates was the excellent fraction in all three treatments. The stability of soil aggregate fell in the order of: GL > FL > BL. The mass proportion of soil aggregate and its associated content significantly improved in GL, and the proportion of microaggregate and its carbon allocation rate decreased. However, due to the lower C inputs in FL and BL, the distribution of aggregates was microaggregate > macroaggregate > silt-clay fraction, and OC content was higher in microaggregates. Different vegetation cover caused the C “fractionation” of density and humus fractions in aggregates. Compared with FL and BL soils, OC contents in light fractions in >2 mm and 2–0.25 mm aggregates were higher in GL, and the OC contents in FA, HA and HU were highest in 2–0.25 mm aggregates, while the humus OC in microaggregates were accumulated in FL and BL. Our results indicated that the plant-derived C entered into macroaggregates firstly, long-term grassland enhanced free and light C fractions in macroaggregate, which consequently improved the stability of soil aggregates and enhanced the “fractionation” effects of large aggregates on the humus fractions. Our results revealed that the carbon sequestration characteristics of soil aggregates under different vegetation cover in mollisol. The C “fractionation” characteristics in aggregates can provide theoretical basis and significant guidance for the study of soil carbon sequestration mechanism and optimization of black soil utilization.