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Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/19/2007 Publication Date: 3/20/2008 Citation: Davies, K.W., Bates, J.D. 2008. The response of thurber's needlegrass to fall prescribed burning. Rangeland Ecology and Management. Rangeland Ecol Manage 61:188-193 Interpretive Summary: Thurber’s needlegrass (Achnatherum thurberianum (Piper) Barkworth) is an important component of the herbaceous understory in many sagebrush and dry forest communities in the Intermountain West. The response of Thurber’s needlegrass to prescribed fall burning is largely unexplored. Thurber’s needlegrass community foliar cover and density, vegetative and reproductive biomass, photosynthetic rates, tissue carbon (C) and nitrogen (N) content, and N (15N/14N) and C (13C/12C) isotope ratios were compared between prescribed fall burned and unburned Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh)-bunchgrass communities. Response variables were measured in the first and second post-burn years. Thurber’s needlegrass community density and cover generally did not differ between treatments. Nitrogen isotope ratios and photosynthetic rates suggested more resources were available to Thurber’s needlegrass in the burned than unburned treatment. However, carbon isotope ratios suggested that water was less available in the burn than unburned treatment in the first post-burn year. Our results suggest prescribed fall burning is not detrimental to Thurber’s needlegrass and can provide some limited benefits. This information can assist land managers planning prescribed fall burns. Technical Abstract: Thurber’s needlegrass (Achnatherum thurberianum (Piper) Barkworth) is an important component of many sagebrush communities in the Intermountain West. Prescribed fall burning is often implemented in sagebrush plant communities to mimic historic wildfires, improve wildlife habitat, and increase livestock forage production. Burning is used because it shifts dominance from sagebrush to herbaceous vegetation. The effects of prescribed fall burning on Thurber’s needlegrass are largely unexplored. The purpose of this study was to determine the response of Thurber’s needlegrass to prescribed fall burning. A randomized block design was used and each block consisted of a fall burned and unburned (control) Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh)-bunchgrass communities. Response variables measured in the first and second post-burn years were Thurber’s needlegrass community foliar cover and density, vegetative and reproductive biomass, photosynthetic rates, tissue carbon (C) and nitrogen (N) content, and N (15N/14N) and C (13C/12C) isotope ratios. Density of Thurber’s needlegrass in both post-burn years and cover in the second post-burn year were not different between treatments (P > 0.05), but cover was less in the burned than control treatment in the first post-burn year (P = 0.008). Carbon isotope ratios in Thurber’s needlegrass differed between the burn (-25.9 ± 0.1) and control (-26.3 ± 0.1) treatments in the first post-burn year (P = 0.019). Nitrogen isotope ratios indicated nitrogen was more available in the burned than control treatment in both years (P < 0.05). Photosynthetic rates of Thurber’s needlegrass were also generally greater in the burned than control treatment (P = 0.045). Our results suggest burning altered the availability of resources to Thurber’s needlegrass plants. Our results also suggest that prescribed fall burning is not detrimental to Thurber’s needlegrass and thus, can be used as a method to shift dominance from sagebrush to herbaceous vegetation. |
