Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: Desert Grassland Canopy Arthropod Species Richness: Temporal Patterns and Effects of Intense, Short-Duration Livestock Grazing

Authors
item Forbes, G - NEW MEXICO STATE UNIV
item Van Zee, Justin
item Smith, W - NEW MEXICO STATE UNIV
item Whitford, Walter - NEW MEXICO STATE UNIV

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 26, 2004
Publication Date: March 1, 2005
Citation: Forbes, G.S., Van Zee, J.W., Smith, W., Whitford, W.G. 2005. Desert grassland canopy arthropod species richness: temporal patterns and effects of intense, short-duration livestock grazing. Journal of Arid Environments. 60:627-646.

Interpretive Summary: Arthropods living in the canopies of two woody shrub species (a sub-shrub [Gutierrezia sarothrae] and a large shrub [Prosopis glandulosa]) and perennial grasses, plus associated herbaceous species, were sampled on 18 0.5-hectare plots in a Chihuahuan Desert grassland for 5 consecutive years. Mesquite shrubs were removed from nine plots, six plots were grazed by yearling cattle in August, and six plots were grazed in February for the last 3 years of the 5-year study. Arthropod species richness ranged between 154 and 353 on grasses, from 120 to 266 on G. sarothrae, and from 69 to 116 on P. glandulosa. There was a significant relationship between the number of families of insects on grass and G. sarothrae and growing season rainfall but species richness was not a function of growing season rainfall on any of the plants. Several of the arthropod families that were the most species rich in this grassland were found on all of the plants sampled, i.e. Salticid spiders, Bruchid and Curculionid beetles, Cicadellid and Psyllid homopterans, and ants (Formicidae). There were more species rich families that were shared by grasses and the sub-shrub G. sarothrae than with mesquite. The absence of a relationship between growing season rainfall and species richness was attributed to variation in life history characteristics of arthropods and to the nonlinear responses of annual and perennial desert grassland plants to rainfall. There were no significant differences in insect family or species richness on any of the plant types as a result of removal of mesquite (P. glandulosa) from selected plots. Intense, short duration (24 h) grazing by livestock during late summer resulted in reduced species richness in the grass-herb vegetation layer but had no effect on insect species richness on snakeweed or mesquite shrubs. Livestock grazing in winter had no effect on insect species richness on any of the vegetation sampled.

Technical Abstract: Arthropods living in the canopies of two woody shrub species (a sub-shrub [Gutierrezia sarothrae] and a large shrub [Prosopis glandulosa]) and perennial grasses, plus associated herbaceous species, were sampled on 18 0.5-hectare plots in a Chihuahuan Desert grassland for 5 consecutive years. Mesquite shrubs were removed from nine plots, six plots were grazed by yearling cattle in August, and six plots were grazed in February for the last 3 years of the 5-year study. Arthropod species richness ranged between 154 and 353 on grasses, from 120 to 266 on G. sarothrae, and from 69 to 116 on P. glandulosa. There was a significant relationship between the number of families of insects on grass and G. sarothrae and growing season rainfall but species richness was not a function of growing season rainfall on any of the plants. Several of the arthropod families that were the most species rich in this grassland were found on all of the plants sampled, i.e. Salticid spiders, Bruchid and Curculionid beetles, Cicadellid and Psyllid homopterans, and ants (Formicidae). There were more species rich families that were shared by grasses and the sub-shrub G. sarothrae than with mesquite. The absence of a relationship between growing season rainfall and species richness was attributed to variation in life history characteristics of arthropods and to the nonlinear responses of annual and perennial desert grassland plants to rainfall. There were no significant differences in insect family or species richness on any of the plant types as a result of removal of mesquite (P. glandulosa) from selected plots. Intense, short duration (24 h) grazing by livestock during late summer resulted in reduced species richness in the grass-herb vegetation layer but had no effect on insect species richness on snakeweed or mesquite shrubs. Livestock grazing in winter had no effect on insect species richness on any of the vegetation sampled.

Last Modified: 11/27/2014
Footer Content Back to Top of Page