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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #46915
Title: HERBAGE DYNAMICS ON 2 NORTHERN GREAT PLAINS RANGE SITES

Author
item HEITSCHMIDT R K - 5434-05-00
item GRINGS E E - 5434-05-00
item HAFERKAMP M R - 5434-05-00
item KARL M G - 5434-05-00

Submitted to: Journal of Range Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/1994
Publication Date: N/A
Citation: N/A

Interpretive Summary: Research was conducted to quantify the productivity, growth dynamics and quality of herbage growing on 2 Northern Great Plains range sites and to relate the species composition of these estimates to the ecological condition of the sites. Accurate estimates of potential herbage production is critical in the development of ecologically and economically sound livestock grazing strategies since livestock production is dependent firstly on herbage production. Results showed there was no difference between the 2 sites in annual herbage production which averaged 1950 lbs/ac. This estimate was quite near previous estimates for the silty range site and nearly 2-fold greater for the claypan site than previous estimates for the silty range site. There were only minor differences between sites in forage quality estimates. The results also showed a discrepancy between sites in assessed ecological condition in that the assigned condition of the silty site was good where as the condition of the clay pan site was fair. The reason the productivity of the clay pan site was higher than expected was because of an abundance of annual grasses. The reason the ecological condition of the clay pan site was only fair was because current ecological condition assessment tactics disregard the contributing role of annual grasses to productivity. This research provides land management personnel sound data to better estimate the potential forage production and ecological condition of these 2 important Northern Great Plains range sites.

Technical Abstract: The broad objective of this study was to quantify the productivity, growth dynamics, and quality of herbage growing on 2 Northern Great Plains range sites and to concurrently relate magnitude and composition of production to the ecological condition of the sites. Using frequent harvest techniques, the 2-year study showed herbage production on the highly productive silty range site averaged 219 g/m2 as compared to 218 g/m2 on the supposedly less productive clay pan range site. The primary reason the clay pan site proved to be as productive as the silty site was attributed to the greater amounts of introduced annual grasses on the clay pan (148 g/m2) than the silty site (104 g/m2). The annual grass component on the clay pan was a near equal mix (71 vs 51 g/m2) of Japanese brome (Bromus japonicus Thunb.) and cheatgrass (B. tectorum L.) whereas the over whelming dominant on the silty site was cheatgrass (73 g/m2). Western wheatgrass [Pascopyrum smithii Rydb. (Love)] was the dominant perennial grass on both sites averaging 49 g/m2 on the clay pan site and 57 g/m2 on the silty site. There were minimal differences between sites in terms of nutrient quality values (i.e., crude protein, acid detergent fiber, neutral detergent fiber) with results showing clearly that age of tissue was the major factor altering seasonal forage quality values. Range condition analyses revealed the clay pan site was in fair ecological condition and the silty site was in good condition. Study results demonstrate the need for land management agencies to continue to refine productivity estimates as well as adopt new techniques for assessing the ecological condition of rangelands.