Journal list menu

Volume 72, Issue 4 p. 939-948
Soil Biology & Biochemistry

Grazing Impacts on Soil Carbon and Microbial Communities in a Mixed-Grass Ecosystem

L. J. Ingram

Corresponding Author

L. J. Ingram

Dep. of Renewable Resources, Univ. of Wyoming, Laramie, WY, 82071

Corresponding author ([email protected]).Search for more papers by this author
P. D. Stahl

P. D. Stahl

Dep. of Renewable Resources, Univ. of Wyoming, Laramie, WY, 82071

Search for more papers by this author
G. E. Schuman

G. E. Schuman

USDA-ARS, High Plains Grasslands Research Station, 8408 Hildreth Rd., Cheyenne, WY, 82009

Search for more papers by this author
J. S. Buyer

J. S. Buyer

USDA-ARS, Sustainable Agricultural Systems Lab., 10300 Baltimore Ave., Bldg. 001 BARC-West, Beltsville, MD, 20705

Search for more papers by this author
G. F. Vance

G. F. Vance

Dep. of Renewable Resources, Univ. of Wyoming, Laramie, WY, 82071

Search for more papers by this author
G. K. Ganjegunte

G. K. Ganjegunte

Dep. of Soil and Crop Sci., Texas AgriLife Res. and Ext. Ctr. at El Paso, Texas A&M System, El Paso, TX, 79927

Search for more papers by this author
J. M. Welker

J. M. Welker

Environ. and Natural Resources Institute and Biological Sciences Dep., Univ. of Alaska, Anchorage, AK, 99501

Search for more papers by this author
J. D. Derner

J. D. Derner

USDA-ARS, High Plains Grasslands Research Station, 8408 Hildreth Rd., Cheyenne, WY, 82009

Search for more papers by this author
First published: 01 July 2008
Citations: 134

All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.

Abstract

Good management of rangelands promotes C sequestration and reduces the likelihood of these ecosystems becoming net sources of CO2 As part of an ongoing study, soil was sampled in 2003 to investigate the long-term effects of different livestock grazing treatments on soil organic carbon (SOC), total nitrogen (TN), and microbial communities. The three treatments studied (no grazing, EX; continuously, lightly grazed [10% utilization], CL; and continuously, heavily grazed [50% utilization], CH) have been imposed on a northern mixed-grass prairie near Cheyenne, WY, for 21 yr. In the 10 yr since treatments were last sampled in 1993, the study area has been subject to several years of drought. In the 0 to 60 cm depth there was little change in SOC in the EX or CL treatments between 1993 and 2003, whereas there was a 30% loss of SOC in the CH treatment. This loss is attributed to plant community changes (from a cool-season [C3] to a warm-season [C4] plant dominated community) resulting in organic C accumulating nearer the soil surface, making it more vulnerable to loss. Soil TN increased in the EX and CL treatments between 1993 and 2003, but declined in the CH treatment. Differences in plant community composition and subsequent changes in SOC and TN may have contributed to microbial biomass, respiration, and N-mineralization rates generally being greatest in CL and least in the CH treatment. Although no significant differences were observed in any specific microbial group based on concentrations of phospholipid fatty acid (PLFA) biomarkers, multivariate analysis of PLFA data revealed that microbial community structure differed among treatments. The CH grazing rate during a drought period altered plant community and microbial composition which subsequently impacted biogeochemical C and N cycles.