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United States Department of Agriculture

Agricultural Research Service

Title: Fragmentation Effects on Soil Aggregate Stability in a Patchy Arid Grassland

Authors
item Bestelmeyer, Brandon
item Ward, Judy - NEW MEXICO STATE UNIV
item Herrick, Jeffrey
item Tugel, Arlene - NRCS

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 8, 2006
Publication Date: July 1, 2006
Repository URL: http://www.srmjournals.org/archive/1551-5028/59/4/pdf/i1551-5028-59-4-406.pdf
Citation: Bestelmeyer, B.T., Ward, J.P., Herrick, J.E., Tugel, A.J. 2006. Fragmentation effects on soil aggregate stability in a patchy arid grassland. Rangeland Ecology and Management. 59:506-415.

Interpretive Summary: Soil aggregate stability (AS) has been promoted as a primary indicator of soil-surface function and a key metric in state-and-transition models. There are few studies, however, that relate AS to grassland degradation. In a Chihuahuan Desert rangeland, we measured variation in AS across a hypothesized fragmentation/transition sequence. We also examined wetting front depth and pH along this sequence. We found that AS exhibited consistent and interpretable variation across the patch boundaries of the different plot types. Wetting depth after a large storm decreased and pH increased along the fragmentation sequence. The results suggest that AS has interpretable relationships with grassland fragmentation and transitions among states.

Technical Abstract: Soil aggregate stability (AS) has been promoted as a primary indicator of soil-surface function and a key metric in state-and-transition models. There are few studies, however, that relate indices of AS to the process of grassland degradation. In a Chihuahuan Desert rangeland, we measured variation in AS across vegetated-bare patch boundaries within six plot types reflecting a hypothesized fragmentation/transition sequence. We also examined wetting front depth and pH along this sequence. We found that AS exhibited consistent and interpretable variation across the patch boundaries of the different plot types. Average AS was highest in grass patches adjacent to small to medium-sized (0.5-1.5 m) bare patches and was low in grass patches adjacent to large (> 3 m) bare patches. AS of bare ground was also lowest when bare patches in continuous grassland were large and when bare ground formed an interconnected matrix. Wetting depth after a large storm decreased and pH increased along the fragmentation sequence. The results suggest that AS has interpretable relationships with grassland fragmentation and transitions among states. Careful attention to patchiness within states and stratification, however, is important and simple classifications of strata, such as “bare interspace” and “plant”, may not be sufficient to document variation in soil function.

Last Modified: 8/1/2014