Soil organic carbon losses due to land use change in a semiarid grassland

• Published in: Plant and soil Vol. 355; no. 1/2; pp. 299 - 309
• Main Authors: Qiu, Liping, Wei, Xiaorong, Zhang, Xingchang, Cheng, Jimin, Gale, William, Guo, Chao, Long, Tao
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01.06.2012; Springer Netherlands; Springer Nature B.V
• Subjects: Agricultural land; Agricultural soils; Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Biological and medical sciences; Biomass; Biomedical and Life Sciences; Carbon; Carbon content; Carbon dioxide; Carbon sequestration; Chemical, physicochemical, biochemical and biological properties; China; Desert soils; Ecology; ecosystems; Environment; Environmental aspects; Farmlands; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Geochemistry; Grassland soils; Grasslands; Land use; Land use change; Life Sciences; microbial biomass; Organic carbon; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Plant Physiology; Plant Sciences; Plant-soil relationships; Regular Article; Roots; Semiarid grasslands; Shrublands; Size distribution; Soil; soil aggregates; Soil aggregation; Soil depth; soil organic carbon; soil sampling; Soil science; Soil Science & Conservation; Soil-plant relationships. Soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Soils; Soils (organic); China; Aggregates; Cultivation; Soil organic carbon; Semiarid grassland; Shrub establishment; Grassland; Organic carbon; Organic matter; Arid environment; Loss; Shrub; Woody plant; Climatic zone; Land use; Soils; Semi arid zone; Aggregate; Soil plant relation
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-011-1099-x

Background and Aims Knowledge about the effect of land use change on soil organic carbon (OC) in semiarid grassland is essential for understanding C cycles and for forecasting ecosystem C sequestration. Our objectives were (1) to study the effect of land use change on aggregate size distribution, aggregate-associated OC concentrations, and aggregate-associated stocks in a semiarid grassland area and (2) to relate changes in the aggregate fractions to changes in total soil OC. Methods Cropland and shrubland plots were established in a semiarid grassland area in 1982. We collected soil samples from adjacent grassland, cropland, and shrubland plots 27 years later and measured OC concentrations in the macroaggregate (>0.25 mm), microaggregate (0.25–0.053 mm) and silt+clay (<0.053 mm) fractions. Results Total soil OC concentrations and stocks decreased significantly after the grassland was converted to cropland or shrubland. Soil microbial biomass C, root biomass, and root C also declined. The proportion of soil in the macroaggregate fraction decreased after conversion to cropland or shrubland. Decreases in macroaggregate-associated OC stocks accounted for more than half of the OC losses that occurred when grassland was converted to cropland. The decreases in macroaggregate-associated OC stocks were due to declines in both macroaggregation and macroaggregate-associated OC concentrations after conversion to cropland. In contrast, decreases in microaggregate-associated OC stocks accounted for more than half of the OC losses when grassland was converted to shrubland. The declines in microaggregate-associated OC stocks were primarily due to a decrease in microaggregate-associated OC concentrations after conversion to shrubland. Conclusions Land use changed caused significant decreases in soil OC stocks. Conversion to cropland soil resulted in large decreases in macroaggregate-associated OC stocks whereas conversion to shrubland resulted in large decreases in microaggregate-associated OC stocks. Any changes in land use in semiarid grasslands could cause the grassland soil to become a source of atmospheric CO2; therefore extreme caution should be taken to avoid this hazard.