Rangeland Ecology & Management

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FIRE AND BROWSING EFFECTS ON WOODY ENCROACHED GRASSLANDS
Author
OConnor, Rory C.
Ensley-Field, Mira
Taylor, Jeff
Nippert, Jesse
Publisher
Society for Range Management
Publication Year
2018
Body

North American grasslands historically had a suite of large herbivores that not only grazed (i.e. bison) but also browsed (i.e. elk, pronghorn, deer). Elk in the tallgrass prairie were extirpated by the 1860�s and at the same time homesteading increased which decreased fire frequencies. The loss of these two drivers (browsing and fire) has coincided with the conversion of grassland to shrubland/woodland over the last 150 years in the tallgrass prairie. Woody expansion can be categorized in to two groups: non-resprouting species that can be killed with fire and resprouting species that cannot be killed with fire. Resprouting species require additional active management strategies to remove them from encroached grasslands. In this study we investigate community, stem density and physiological effects of continuous simulated browsing and prescribed fire on Cornus drummondii, a resprouting native woody species, in hopes to understand how a reintroduction of the historical drivers can potentially reverse woody expansion. After three years of continuous simulated browsing we found that browsing alone does not change rates photosynthesis but it does increase stomatal conductance and transpiration rates. But when browsing was coupled with a prescribed fire, photosynthetic rates decreased, stomatal conductance and transpiration rates did not differ among treatments. The physiological responses from multiple years of browsing and a prescribed fire show that the shrubs are trying to maintain carbon acquisition but are not. The combined browsing and fire effects are manifest in the shrubs through smaller leaf area, hedging and decreased stem densities that result in a decrease of shrub cover and an increase in herbaceous understory. The increase in herbaceous understory was mostly due to increases in the dominant warm season grasses. Browsing or fire alone is not enough to decrease woody encroachment but coupled together, in our results suggest an effective management strategy.

Language
English
Resource Type
Text
Document Type
Conference Proceedings
Conference Name
SRM Reno, NV