Browsing Journal of Range Management, Volume 40, Number 1 (January 1987) by Subjects
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C3/C4 Production Shift on Seasonal Burns: Northern Mixed PrairieThis study investigates the potential of fire to manipulate the balance of C3 (cool-season) and C4 (warm-season) herbage in 2 northern Mixed Prairie communities. The xeric high prairie community and mesic low prairie community were chosen to represent regional moisture extremes. Treatments included dormant spring burn, mid-summer burn, dormant fall burn, and untreated. The high prairie community appears to be a C3-dominant type. All 3 burn treatments increased the C3 herbage fraction relative to untreated sites. Total production, however, was unaffected by treatment. The C3/ C4 ratio of high prairie communities appears to be the result of long-term adaptation rather than short-term adjustments to fire or weather effects. Spring burning shifted low prairie communities towards C4 herbage relative to other treatments. This was due to an increase in C4 herbage (and total) rather than to a decrease in C3 herbage. The C3/C4 ratio of low prairie communities did appear to respond to short-term adjustments in moisture, temperature, and light caused by the spring burn. The response of low prairie C3/C4 ratios to mid-summer and dormant fall burns appeared to be related to phenological and indirect weather effects rather than to changes in site microclimate caused by the fires.
Yield and Digestibility of Old World Bluestem Grasses as Affected by Cultivar, Plant Part, and MaturityOld World bluestems (Bothriochloa spp.) have been used in the U.S. for over 60 years but few data are available on effects of management or cultivar differences for forage yield and quality. Field experiments were conducted on a Kirkland silt loam (Uderic Paleustoll) soil for 2 years (1982-83), in order to assess the yield and quality of 4 such cultivars as affected by maturation and plant part. The experimental design was a split-split plot, in a randomized complete block, with 4 replications, 4 cultivars ('Caucasian', 'Ganada', 'Plains', 'WW Spar'), 10 harvest dates, and 3 plant parts (whole plant, stem, and leaf). Cultivars were main plots; harvest dates and plant parts were sub and sub-sub plots, respectively. Response variables were dry matter yield (DMY), in vitro dry matter disappearance (IVDMD), leaf to stem ratio (L/S), and in vitro digestible dry matter yield (IVDDMY). Ganada consistently had the lowest leaf, stem, and whole plant DMY and IVDDMY. Caucasian had higher leaf, stem, and whole plant DMY and IVDDMY than Plains and WW-Spar in 1983, but the DMY and IVDDMY of these cultivars were similar in 1982. Quadratic and linear equations were satisfactorily fit to the DMY and IVDDMY data in 1982 and 1983, respectively. The IVDMD in whole plant samples decreased at average rates of 4.2 and $5.5 g kg ha-1 daily in 1982 and 1983, respectively, during harvest week one. Among cultivars, Caucasian had the highest rate of decline and Ganada the lowest. The decline was quadratic in nature and faster in stem fractions. Cultivar IVDMD differences were consistent over plant parts. Ganada and Caucasian had the highest and lowest IVDMD concentrations, respectively. Plains and WW-Spar had IVDMD values of similar magnitude and intermediate to those of Ganada and Caucasian. Cultivar leaf to stem ratios were similar in 1982 but different in 1983 with Plains and Caucasian having higher L/S ratios than Ganada and WW-Spar. For these cultivars leafiness was a poor indicator of digestibility.