Defoliation-induced enhancement of total aboveground nitrogen yield of grasses

• Published in: Oikos Vol. 91; no. 2; pp. 280 - 284
• Main Authors: Green, Ronald A., Detling, James K.
• Format: Journal Article
• Language: English
• Published: Copenhagen Munksgaard International Publishers 01-11-2000; Munksgaard International Publishers, Ltd; Blackwell
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Bison; Defoliation; Fundamental and applied biological sciences. Psychology; Grasses; Grazing; Herbivores; Mixed grass prairies; National parks; Nitrogen; Plants; Poaceae; Prairies; Synecology; Terrestrial ecosystems; USA, South Dakota; South Dakota; United States; North America; America; Grassland; Monocotyledones; Primary productivity; Browsing; Nitrogen; Experimental study; Medium enrichment; Nitrogen balance; Defoliation; Gramineae; Angiospermae; Spermatophyta; Chemical composition; Herbaceous plant
• ISSN: 0030-1299; 1600-0706
• DOI: 10.1034/j.1600-0706.2000.910208.x

We conducted an experiment in a northern mixed-grass prairie at Wind Cave National Park, South Dakota, USA to evaluate the effect of defoliation frequency on aboveground net primary production (ANPP), shoot nitrogen concentration, and aboveground N yield of graminoids. ANPP was significantly reduced at weekly and biweekly defoliation frequencies, but unaffected relative to unclipped controls at monthly and bimonthly frequencies. By contrast, clipping at all frequencies increased shoot N concentration above that of controls, and this increase was greatest at monthly or more frequent defoliations. Total aboveground N yield and potential N yield to grazers were greatest at intermediate (bimonthly to biweekly) frequencies. We suggest that grazers may maximize their nutritional status in this system by periodically regrazing areas at frequencies near the approximately monthly optimum that we observed.