• Influence of Plant Material Handling Protocols on Terpenoid Profiles of One-Seed Juniper Saplings

      Utsumi, Santiago A.; Cibils, Andrés F.; Estell, Rick E.; Wang, Yuan-Feng (Society for Range Management, 2006-11-01)
      Accurate estimation of one-seed juniper (Juniperus monosperma [Engelm.] Sarg.) intake by herbivores often requires harvesting, transporting, and storing plant material that is later used in pen experiments. Such manipulation could alter terpenoid profiles and modify herbivory levels significantly. We used gas chromatography mass spectrometry (GC/MS) to analyze the terpenoid profile of leaves from 10 short (0.5 m +/- 0.05, mean +/- SE) and 10 tall (1.14 m +/- 0.06) one-seed juniper saplings subjected to 3 handling protocols: a) placed on dry ice after clipping and stored after 5 hours at –80 degreesC for 3 weeks (Control); b) kept at ambient temperature for the first 24 hours and then frozen at –80 degreesC for 3 weeks; or c) kept at ambient temperature for the first 24 hours, and then stored at 8 degreesC for 3 weeks. Juniper saplings contained 51 terpenoids, 3 of which were unknown compounds. Fourteen terpenoids accounted for 95% of the total amount of volatiles. The most abundant compound was a-pinene, which accounted for 65% of total terpenoids present. Handling protocols were not associated with detectable differences in total terpenoid content (Means +/- SE, Control: 21.68 +/- 1.42 mg g-1 dry matter [DM]; Frozen after 24 hours: 19.55 +/- 1.08 mg g-1 DM; Refrigerated after 24 hours: 18.80 +/- 1.13 mg g-1 DM). However, total terpenoid amount and concentration of a few major compounds tended to decrease with increasing storage temperature. Handling protocols induced detectable variations in a small number of minor terpenoids. We observed large among-plant variation in terpenoid profiles that was not fully explained on the basis of sapling size. This study suggests that the length of storage period of one-seed juniper branches should not exceed 3 weeks and that storage refrigeration temperatures should be kept below 8 degreesC to prevent significant alterations in terpenoid profiles. 
    • One-Seed Juniper Sapling Use by Goats in Relation to Stocking Density and Mixed Grazing With Sheep

      Utsumi, Santiago A.; Cibils, Andres F.; Estell, Richard E.; Baker, Terrell T.; Walker, John W. (Society for Range Management, 2010-05-01)
      Suppression of one-seed juniper (Juniper monosperma [Englem.] Sarg.) reinvasion with goats requires achieving levels of defoliation of newly established saplings that eventually kill or suppress plant growth. We tested the effects of stocking density and mixed grazing with sheep on the level of use of one-seed juniper saplings by goats. In summer and spring, groups of 10 does (goats alone, GA) or 5 does and 4 ewes (mixed grazing, MG), grazed 20 X 30 m cells infested with saplings (500-533 ha-1; mean: 0.8 m tall), either continuously for 6 d (low stocking density, LD) or with daily rotation through 10 X 10 m cells during the 6-d period (high stocking density, HD) in a block design. Feeding activity; juniper in feces; utilization of herbaceous vegetation; frequency of saplings with light, moderate, and heavy foliage and bark use; and branch utilization were determined. Goats in HD spent more time feeding on saplings, less time feeding on herbaceous forages, and tended to consume more juniper than goats in LD. Utilization of herbaceous vegetation ranged from 52% to 73% and was higher for MG than GA and for LD than HD. The MG-HD treatment resulted in the highest frequency of short saplings (< 0.5 m) with heavy defoliation in summer and spring, and lowest frequency of saplings with light debarking in spring. Heavy defoliation was more frequent in short saplings, whereas heavy debarking was more frequent in tall (> 1 m) saplings. Sapling mortality was not affected by treatments (P > 0.05) and averaged 5% across treatments. Branch debarking was greater in spring (P = 0.02) and explained approximately 80% of branch mortality and 62% and 52% of the reduction in sapling live crown height and volume. Branch utilization (percent length) was not affected by grazing treatments (range: 45-48%), but was influenced by the length and diameter of branches. This study suggests that high stocking density and mixed grazing stimulate feeding behaviors that increase utilization of juniper saplings by goats. Susceptibility of saplings to defoliation and debarking varies with sapling size, branch structure, and season. Targeted grazing in spring appears to have a greater impact on sapling suppression and branch mortality due to higher debarking frequency.