Location: Forage and Range ResearchTitle: Non-growing season soil CO2 efflux patterns in five land-use types in northern China Author
|Pan, Zhanlei - China Agricultural University|
|Liu, Hongfei - China Agricultural University|
|Ma, Lei - China Agricultural University|
|Rong, Yuping - China Agricultural University|
Submitted to: Atmospheric Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2016
Publication Date: N/A
Interpretive Summary: Carbon loss from the soil increases greenhouse gases in the Earth's atmosphere, which is suspected to be a leading cause of global change. Overgrazing and unsuitable farming practices have led to grassland degradation in northern China, which may lead to increased soil carbon loss. Soil carbon loss was measured in five land-use types during the non-growing season (Oct. to April) in northern China. The land-use types included three native grasslands with differing sheep stocking rates (ungrazed, moderately grazed and heavily grazed grassland), a fertilized annual cropland and a perennial pasture used for haying and winter grazing. Loss of carbon from the soil was greatest during the autumn and spring freeze-thaw periods compared to the winter permanently frozen period. Cabon loss was greatest in the perennial pasture, followed by cropland, ungrazed grassland, moderately grazed grassland and heavily grazed grassland. Air temperature during the non-growing season was the main factor that controlled soil carbon loss, although soil water content also played a role. Annual weather variation, however, overshadowed the influence of land-use types on soil carbon loss.
Technical Abstract: Overgrazing and unsuitable farming practices have led to grassland degradation in northern China. This studhy examined soil CO2 efflux (Fc) from five land-use types during the non-growing season on the southeastern edge of the Mongolian Plateau in China. The land-use types included three native vegetation steppes differing in stocking rate [ungrazed (UG), moderately grazed (MG) and heavily grazed (HG)], a fertilized annual cropland (CL) and a perennial pasture (PP) used for haying and winter grazing. Values of Fc were measured at 3-day to 2-week intervals during the non-growing season in two contrasting hydrological years (2012-13 and 2013-14) using closed chambers. The Fc during 1 Oct. 2013 to 30 April 2014 averaged 475 mg C m-2 for all sites compared to a significantly (P<0.05) lower Fc (102 mg C m-2) during 1 Oct 2012 to 30 April 2013. The seasonal Fc patterns followed the same trend during the two non-growing seasons with greater Fc observed in the autumn and spring freeze-thaw periods compared to the winter permanently frozen period, which accounted for 4.8% of accumulated total non-growing season Fc. Grazing reduced Fc by 23% for MG and 32% for HG compared to UG. Soil CO2 efflux from the PP land-use type, which was grazed during the non-growing season, was 22% greater than that from the UG land-use type. Air temperature during the non-growing season was the main factor controlling soil CO2 efflux (R2=0.40, P<0.001), although soil water content also played a role. Precipitation received during the growing season had a large legacy effect on Fc. Annual weather variation overshadowed the influence of land-use types on Fc.