Document Detail

Impact of grazing intensity on seasonal variations in soil organic carbon and soil CO2 efflux in two semiarid grasslands in southern Botswana.
MedLine Citation:
PMID:  23045706     Owner:  NLM     Status:  MEDLINE    
Biological soil crusts (BSCs) are an important source of organic carbon, and affect a range of ecosystem functions in arid and semiarid environments. Yet the impact of grazing disturbance on crust properties and soil CO(2) efflux remain poorly studied, particularly in African ecosystems. The effects of burial under wind-blown sand, disaggregation and removal of BSCs on seasonal variations in soil CO(2) efflux, soil organic carbon, chlorophyll a and scytonemin were investigated at two sites in the Kalahari of southern Botswana. Field experiments were employed to isolate CO(2) efflux originating from BSCs in order to estimate the C exchange within the crust. Organic carbon was not evenly distributed through the soil profile but concentrated in the BSC. Soil CO(2) efflux was higher in Kalahari Sand than in calcrete soils, but rates varied significantly with seasonal changes in moisture and temperature. BSCs at both sites were a small net sink of C to the soil. Soil CO(2) efflux was significantly higher in sand soils where the BSC was removed, and on calcrete where the BSC was buried under sand. The BSC removal and burial under sand also significantly reduced chlorophyll a, organic carbon and scytonemin. Disaggregation of the soil crust, however, led to increases in chlorophyll a and organic carbon. The data confirm the importance of BSCs for C cycling in drylands and indicate intensive grazing, which destroys BSCs through trampling and burial, will adversely affect C sequestration and storage. Managed grazing, where soil surfaces are only lightly disturbed, would help maintain a positive carbon balance in African drylands.
Andrew D Thomas
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Philosophical transactions of the Royal Society of London. Series B, Biological sciences     Volume:  367     ISSN:  1471-2970     ISO Abbreviation:  Philos. Trans. R. Soc. Lond., B, Biol. Sci.     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-10-09     Completed Date:  2013-03-08     Revised Date:  2013-12-04    
Medline Journal Info:
Nlm Unique ID:  7503623     Medline TA:  Philos Trans R Soc Lond B Biol Sci     Country:  England    
Other Details:
Languages:  eng     Pagination:  3076-86     Citation Subset:  IM    
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MeSH Terms
Carbon / chemistry*
Carbon Cycle
Carbon Dioxide / chemistry*
Chlorophyll / chemistry
Conservation of Natural Resources
Desert Climate
Indoles / chemistry
Phenols / chemistry
Poaceae / chemistry
Soil / chemistry*
Soil Microbiology*
Water / chemistry
Reg. No./Substance:
0/Indoles; 0/Phenols; 0/Soil; 059QF0KO0R/Water; 1406-65-1/Chlorophyll; 142M471B3J/Carbon Dioxide; 152075-98-4/scytonemin; 7440-44-0/Carbon; YF5Q9EJC8Y/chlorophyll a

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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