• Ungulate herbivory of willows on Yellowstone's northern winter range

      Singer, F. J.; Mark, L. C.; Cates, R. C. (Society for Range Management, 1994-11-01)
      Effects of unmanaged populations of large mammalian herbivores, especially elk (Cervus elaphus on vegetation is a concern in Yellowstone National Park, since wolves (Canis Lupus) are extirpated, ungulate migrations are altered by human activities and the disruption of natural process is possible. Stands of low, hedged (height-suppressed) willows (Salix spp.) are observed throughout the greater Yellowstone National Park area where high densities of wintering elk or moose (Alces alces) exist. The height of 47% of the willow stands surveyed on Yellowstone's northern winter range has been suppressed. Mean leader use of willows of all heights was (P < 0.05 in the winter of 1987-88, increased to 60% in winter 1988-89, following the drought and fires of 1988, then declined to 44% in 1989-90 and winter 1990-96. Height-suppressed willows (43 +/- 2 cm, mean +/- SE) were about one-half as tall as tall willows (83 +/- 4 cm). Percent twig use of suppressed willows in summer (25%) and winter (59%) was significantly more than for intermediate or tall stands (P < 0.05). Suppressed willows produced about one-fourth the aboveground annual biomass compared to taller willows; even after 27 or 31 years of protection, previously-suppressed willows produced only one-third the aboveground biomass of taller willows, suggesting suppressed willows grow on sites with lower growth potential. Growth conditions for willows on the northern winter range may have declined due to a warmer and drier climate this century, locally reduced water tables—because of the decline on beaver (Castor canadenis), or fire suppression may be responsible for the observed changes. Tall and intermediate-height willows contained higher concentrations of nitrogen and they exhibited more water stress than height-suppressed willows of the same species. More xeric growth conditions this century than last century, especially during the decades of the 1920's, 1930's, and 1980's, may explain the low growth rates and lower chemical defenses against ungulate herbivory for height-suppressed willows. We propose a more xeric climate and locally-reduced water tables likely contributed to the willow declines on the northern winter range, but that the proximate factor in the declines was herbivory by native ungulates.
    • Technical Note: Measuring post-germination growth

      Booth, D. T.; Griffith, L. W. (Society for Range Management, 1994-11-01)
      Measurement of heterotrophic plant growth is important for evaluating seed or seedling vigor. Hand measurement of large numbers of germinants and seedlings is tedious, can injure young plants, and is often inexact when curved roots are involved. Using the Cobb-Jones germination method with a digitizing tablet, a personal computer, apparatus, and methods we developed, reduces the time, tedium, injury, and guesswork often associated with hand measurements. Evaluation of measurement precision using our methods indicates that repeated measurements of individual germinants/seedlings will have average differences that are less than 1.0 mm.
    • Sheep grazing efficiency and selectivity on Oregon hill pasture

      Ali, E.; Sharrow, S. H. (Society for Range Management, 1994-11-01)
      Grazing trials were conducted during early and late spring of 1988 and 1989 to evaluate the impact of sheep grazing duration and stocking density on grazing efficiency and forage selectivity in tall fescue (Festuca arundinacea Schreb.)-subclover (Trifolium subterranum L.) hill pastures near Corvallis, Ore. Grazing treatments were 2, 6, and 10 days duration with corresponding stocking densities 380,130, 78, and 1,390, 460, and 280 ewes/ha during early and late spring trials each year, respectively. Grazing efficiency was generally greater (P < 0.05) for the low density/longer duration (10-day) than for higher density/shorter duration (2-day) treatments. Greater grazing efficiency as duration increased largely reflected higher rates of intake rather than lower levels of non-consumptive forage destruction. Stocking density within a constant grazing duration (2 days) had little effect on grazing efficiency. Within the 10 day grazing treatment, grazing efficiency was highest during the last 4 days and lowest during the first 2 days (P < 0.05). Although short duration/high density grazing is considered to be non-selective, sheep were equally or more selective under very short duration/very high density compared to longer duration/lower density treatments in this study. These results suggest that the very short duration with very high stocking density was not an attractive management option since grazing efficiency was low and sheep were more selective.
    • Selective-placement burial of drilling fluids: Effects on soil properties, buffalograss and fourwing saltbush after 4 years

      McFarland, M. L.; Ueckert, D. N.; Hons, F. M.; Hartmann, S. (Society for Range Management, 1994-11-01)
      A field study was established in 1986 to evaluate selective-placement burial as an alternative technique for on-site disposal of drilling fluids in arid and semiarid areas. Soluble salt and heavy metal migration in the soil, and establishment, yield and chemical composition of fourwing saltbush (Atriplex canescens (Pursh) Nutt.) and buffalograss (Buchloe dactyloides (Nutt.) Engelm.) were determined 44 months after simulated reserve pits were constructed to provide burial depths of 30, 90 (with and without a 30-cm thick, coarse limestone capillary barrier), and 150 cm, with sequential replacement of stockpiled subsoil and topsoil. Soluble salt concentrations increased most significantly in the 30-cm zone immediately above buried drilling fluids, regardless of treatment. Upward salt movement was greatest in the 90- and 150-cm treatments, with significant increases in Electrical Conductivity (EC) and Exchangeable Sodium Percentage (ESP) values observed as much as 60 and 30 cm above buried drilling fluid, respectively. Capillary barriers reduced the extent of upward salt migration, but had little effect in soil zones immediately overlying the drilling fluid. There was no evidence of upward migration of Ba, Cr, Cu, Ni, or Zn from buried drilling fluids into overlying soil, but concentrations of Cu and Zn were greater in saltbush stems grown on plots with buried drilling fluids on 1 site. Fourwing saltbush survival averaged 92 to 100% and was not affected by depth of drilling fluid burial. Significant reductions in saltbush canopy cover and yield on the 30-cm burial treatment were observed on 1 study site. Elevated Na concentrations in aboveground tissue of both species in the 30-cm burial treatment on 1 site did not adversely affect survival or plant growth. Differences between study sites in the extent of upward salt movement in the soil and in plant response were attributed to differences in soil clay type and content.
    • Relationship of tarbush leaf surface secondary chemistry to livestock herbivory

      Estell, R. E.; Fredrickson, E. L.; Anderson, D. M.; Mueller, W. F.; Remmenga, M. D. (Society for Range Management, 1994-11-01)
      Tarbush (Flourensia cernua DC.) is an abundant but generally unpalatable shrub native to the Chihuahuan Desert. The objective of this study was to examine the leaf surface chemistry of tarbush in relation to degree of use by ruminants. Mature tarbush leaves were collected on 2 sites during 2 periods approximately 2 weeks apart from plants exhibiting either high (> 45%) or low (< 10%) use when browsed by cattle, sheep, and goats confined to a small area (5 plants per use category for each site/period combination). A greater (P < 0.05) concentration of epicuticular wax was detected on the leaf surface of plants that were used to a lower degree (82 and 10.3% of the leaf dry matter for high- and low-use plants, respectively). Several leaf surface compounds were related to period, while site and degree of use were seldom related to individual mono- and sesquiterpenes measured in this study. Camphene and 10 unidentified compounds differed between periods (P < 0.10). Two unidentified compounds were related to site (P < 0.10) and 2 others were related to use (P < 0.10). In summary, individual leaf surface compounds on tarbush do not appear to greatly affect degree of use of tarbush by livestock, but collectively (based on epicuticular wax data), these compounds may influence the diet selected by browsing ruminants.
    • Range assessment using remote sensing in Northwest Patagonia (Argentina)

      Paruelo, J. M.; Golluscio, R. A. (Society for Range Management, 1994-11-01)
      A methodology based on remotely sensed data (LANDSAT MSS) was used for rapid assessment of rangelands in the grass and shrub steppes of NW Patagonia (Argentina). We calibrated Normalized Difference Vegetation Index (NDVI) data using total plant cover, grass cover, shrub cover, and floristic data. Total vegetation cover and grass cover was predicted with high accuracy from Normalized Difference Vegetation Index data. The correlation between observed and estimated cover was 0.87 and 0.82 (P < 0.01) for total cover and grass cover respectively. The correlation was lower for shrub cover than for grass (r = 0.45, p < 0 .01). Normalized Difference Vegetation Index data was used to accurately predict cover of Festuca pallescens (St. Yves) Parodi (coiron blanco) and Nassau via glomerulosa (Lag.) Don (colapiche), 2 species with contrasting response to grazing in the Occidental district of Patagonia, and typical of vegetation with very different grazing values. The correlation between observed and estimated from the Normalized Difference Vegetation Index cover was 0.67 and 0.53 (P < 0.01) for Festuca pallescens (coiron blanco) and Nassauvia glomerulosa (colapiche) respectively.
    • Production and nutritional quality of western ragweed seed in response to fertilization

      Peoples, A. D.; Lochmiller, R. L.; Leslie, D. M.; Engle, D. M. (Society for Range Management, 1994-11-01)
      The importance of western ragweed (Ambrosia psilostachya) DC.) in the diet of bobwhites (Colinus virginianus Merr.) and their high dietary requirement for essential amino acids prompted us to explore the use of disking and fertilization (nitrogen and phosphorus) to improve its nutritional quality on deep, unfertile, sandy-soil rangelands in western Oklahoma. Fertilization (55 kg N ha-1, 56 kg P ha-1 as diammonium phosphate) of disk strips did not readily increase seed production of western ragweed. Fertilizer had no detectable effect on nutritional quality of seeds, which contained an average of 13% crude protein and 21% fat. Conflicting results reported on the effect of fertilizer on the quality of plant proteins within the literature could be attributable to differences of climate and soils, growth habits of different plant species, type and rates of fertilizers, and stages of maturity when plants are harvested for analysis.
    • Physiological comparisons of crested wheatgrass and western wheatgrass to water

      Frank, A. B. (Society for Range Management, 1994-11-01)
      Knowledge about mechanisms of water stress tolerance, growth, and development of forages are important in development of management practices and in germplasm improvement. Plants of crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes] and western wheatgrass [Pascopyrum smithii (Rydb.) Gould] were field grown at 3 soil water levels (50, 100, and 150% of average rainfall and 2 N levels (10 and 110 kg N ha-1) and sampled to determine proline, water soluble carbohydrate, and abscisic acid concentration from about the 4-leaf through heading stages of development. Proline concentration increased in both species as wabr stress increased. Proline decreased in crested wheatgrass but increased in western wheatgrass as plant development advanced. Abscisic acid concentrations increased in both species as water stress increased. Western wheatgrass contained about 1.7 times higher abscisic acid concentration than crested wheatgrass. Carbohydrate concentrations increased with water stress and were higher in crested than western wheatgrass. Increasing proline and abscisic acid concentrations in western wheatgrass and the decreasing concentrations in crested wheatgrass at later stages of development suggest that the stress response mechanisms that enhance proline and abscisic acid may be more operative in western than crested wheatgrass. These results suggesting that western wheatgrass is more tolerant of water stress under field conditions than crested wheatgrass should be useful in developing sustainable management practices. Also, proline concentration changes with plant development suggesting that germplasm sampling should be performed over time.
    • Observation: Comparative live-history of cheatgrass and yellow starthistle

      Sheley, R. L.; Larson, L. L. (Society for Range Management, 1994-11-01)
      The objective of this research was to characterize the life-histories of cheatgrass (Bromus tectorum L.) and yellow starthistle (Centaurea solstitialis L.) growing in association. Biweekly demographic attributes were monitored during 1991 (moist spring) and 1992 (dry spring). Data were arranged into life-history tables, and sensitivity analysis was performed to determine key transition phases. The entire cheatgrass seed crop reached the soil surface, 41% of yellow starthistle's seed output was lost during seed rain. Frost heaving reduced winter seedling populations of cheatgrass (53%) more than yellow starthistle (40%). All cheatgrass seedlings surviving the frost heaving period became adults. Yellow starthistle density was reduced by 75% during the juvenile phase. Cheatgrass adults appeared about 6 weeks before yellow starthistle adults. Cheatgrass seed output remained about 7,000 m2 with moist and dry spring conditions. Yellow starthistle seed output was about 21,600 m2 and 5,200 m2 with moist and dry spring conditions, respectively. Reduction of yellow starthistle seed output with dry spring conditions suggest oscillatory community dynamics. Key processes associated with life-history transitions were interference (competition), resource acquisition rates and duration, and reproductive allocation.
    • Long-term effects of brush management on vegetation diversity in ephemeral drainages

      Nolte, K. R.; Gabor, T. M.; Hehman, M. W.; Asleson, M. A.; Fulbright, T. E.; Rutledge, J. C. (Society for Range Management, 1994-11-01)
      There has been recent concern regarding the effects of range management practices on biodiversity. Our objective was to determine the long-term (> 30 years) effects of chaining, and chaining followed by root plowing, on vegetation diversity in an ephemeral drainage system. Plant species richness and diversity were estimated in 2 chained (ca. 1950) areas, 2 chained (ca. 1950) and root-plowed (ca. 1960) areas, and 2 untreated areas during April 1993. Beta diversity within treatments was estimated with mean dissimilarity (l-mean similarity). Mean similarity was quantified with Jaccard's index. Spatial gradient analysis in which pairwise similarities were regressed against the distance between each pair of samples within a site was used to describe similarity within a site. Species richness and diversity were similar among treatments for both herbaceous and woody species. Similarity (Jaccard's index) among transects within a site increased with increasing degree of disturbance. Chained and root plowed sites had lower beta diversity than chained or untreated sites. Similarity in the chained and root plowed sites varied randomly, not spatially, while the control (untreated) and chained sites had negative spatial gradients, indicating spatial heterogeneity within these sites. Although root plowing did not reduce species richness and diversity as reported on upland sites in previous studies, beta diversity and habitat heterogeneity were lower on chained and root plowed sites than on chained or untreated sites.
    • Grazing intensity effects on litter decomposition and soil nitrogen mineralization

      Shariff, A. R.; Biondini, M. E.; Grygiel, C. E. (Society for Range Management, 1994-11-01)
      A 2 year study in south central North Dakota determined the responses of (1) litter and root decomposition and nitrogen (N) release, and (2) soil N mineralization to grazing intensity. The treatments were: long term not grazed, moderate grazing, and heavy grazing. The moderate grazing and the heavy grazing treatments removed 45% and 77% of annual above-ground growth respectively. The moderate grazing treatment resulted in higher decomposition and soil N mineralization rates, and lower N releases via decomposition than the long term not grazed and heavy grazing treatments. No consistent differences were found between the long term not grazed and heavy grazing treatments. Annual litter and root decomposition rates in the moderate grazing treatment averaged 55% for 1989-1990 and 63% for 1990-1991 while the long term not grazed and heavy grazing treatments had rates for the same periods of 13% and 19%. The moderate grazing treatment had a net soil N mineralization of 60 micrograms.g-1 and 269 micrograms.g-1 during the 1989 and 1990 growing seasons whereas the long term not grazed and heavy grazing treatments had net soil immobilization for the same periods of -59 micrograms.g-1 and -115 micrograms.g-1. Annual N release from litter and root decomposition in the heavy grazing and long term not grazed treatments averaged 70% and 38% respectively during the 1989-1990 incubation period, and 51 % and 23% during 1990-1991. The equivalent values for the moderate grazing treatment were 47% and -6% (net N immobilization) for 1989-1990 and 41% and 23% for 1990-1991. Results from this study seem to indicate that the standard grazing rule of "take half leave half" may have a significant impact in N conservation and the supply of mineral N for plant growth.
    • Effects of defoliation and competition on total non-structural carbohydrates of spotted knapweed

      Lacey, J. R.; Olson-Rutz, K. M.; Haferkamp, M. R.; Kennett, G. A. (Society for Range Management, 1994-11-01)
      Spotted knapweed (Centaurea maculosa Lam.) is replacing native bunchgrasses and interfering with resource management objectives on many ranges in the northern Intermountain Region. Herbicides, biological control agents, and fire have not successfully contained spotted knapweed. Since knapweed is grazed in some situations, effects of defoliation and competition on total nonstructural carbohydrates (TNC) of spotted knapweed plants were determined in this study. Transplanted knapweed plants were grown for 6 months in a greenhouse under 3 levels of competition with bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] Love) and 3 levels of defoliation. Total nonstructural carbohydrates (pool and concentration) were determined at the end of the experiment. Concentration and pools of carbohydrates generally varied among stems, roots, crowns, and with monthly defoliations. Importance of stems for carbohydrate storage was more evident in analyses of pools rather than concentrations. Monthly defoliations decreased carbohydrate concentrations by about 50%, and pools by about 80% respectively within stems, roots, and crowns. While competition from bluebunch wheatgrass influenced total nonstructural carbohydrates concentrations, it did not influence pools. Although frequent defoliations of spotted knapweed reduced carbohydrates, other factors probably limit the feasibility of using grazing animals to control spotted knapweed on native bunchgrass ranges in western North America.
    • Controlled release chromic oxide and alkaline peroxide lignin marker methods

      Momont, P. A.; Pruitt, R. J.; Emerick, R. J.; Pritchard, R. H. (Society for Range Management, 1994-11-01)
      Two digestion trials, using 20 ram lambs (Experiment 1) and 8 cows (Experiment 2) provided ad libitum access to mature prairie grass hay, were conducted to evaluate controlled release intraruminal chromic oxide boluses and alkaline hydrogen peroxide lignin as markers for estimating forage intake by the fecal output/indigestibility ratio. A soybean meal and 3 urea based supplements were fed to lambs in Experiment 1. For both experiments, daily fecal output was weighed and sampled for 6 days (Experiment 1) and 5 days (Experiment 2) beginning 7 days after oral administration of controlled release boluses. Rectal fecal grab samples were also collected at 1000 daily and at 4-hour intervals on day 4 of collections for Experiment 2. For both experiments Cr2O3 excretion rates based on total collections were used to evaluate Cr2O3 controlled release boluses and alkaline hydrogen peroxide lignin predictive value in place of manufacturer's stated release rate. In experiment 1, fecal Cr2O3 output was 224 mg/day +/- 3.9 compared to the manufacturer's stated release rate of 201 mg Cr2O3/day. Fecal alkaline hydrogen peroxide lignin recovery was 97.8% +/- 1.9. Samples composited over the 6-day collection period predicted fecal output, apparent dry matter digestibility, and dry matter intake similar (P = .44, .15 and .55; respectively) to actual values. Supplemental treatment and dry matter intake had no effect (P > .38) on daily fecal Cr2O3 output or alkaline hydrogen peroxide lignin recovery. In Experiment 2, fecal Cr2O3 was 1,662 mg/day +/- 63 compared to the manufacturer's stated release rate of 1,505 mg Cr2O3/day. Fecal alkaline hydrogen peroxide lignin recovery was 95.9% +/- 7. Using 5-day composited samples, predicted fecal output, dry matter digestibility, and dry matter intake were similar (P = .49, .21 and .49; respectively) to actual values. Increasing the number of daily grab samples increased R2 values between actual and predicted fecal output and dry matter digestibility. Fecal grab samples and total fecal collection samples provided a similar relationship (R2=.71) between actual and predicted dry matter intake when each were composited over 5 days. Time of day did not affect fecal Cr2O3 or alkaline hydrogen peroxide lignin concentrations. These results suggest that grab samples collected once daily on 5 consecutive days can be used to predict fecal output when Cr2O3 controlled release boluses are used. Although recoveries of fecal alkaline hydrogen peroxide lignin were near 100% in these experiments, digestibility estimates using this internal marker were variable and adversely influenced predictions of dry matter intake.
    • Comparison of sheep and goat preferences for leafy spurge

      Walker, J. W.; Kronberg, S. L.; Al-Rowaily, S. L.; West, N. E. (Society for Range Management, 1994-11-01)
      The objective of these studies was to compare preference for leafy spurge (Euphorbia esula L.) by sheep and goats. Study 1 was a choice test that paired leafy spurge with either arrowleaf balsamroot (Balsamorhiza sagittata (Pursh) Nutt.) or crested wheatgrass (Agropyron cristatum (L.)Gaertn.) for a 30 minute feeding period. Study 2 consisted of 3 grazing trials on spurge-infested pastures. Differences between sheep and goat grazing were measured using capacitance meter estimates of standing crop and ocular estimates of composition; counts of grazed and ungrazed leafy spurge stems; and bite counts to estimate botanical composition of diets. The paired choice study showed that selection for leafy spurge was affected by the interaction (P < 0.0001) of animal species and the choice alternative. Goats preferred leafy spurge (80% of consumption) compared to arrowleaf balsamroot, but demonstrated a relative avoidance (33% of consumption) of leafy spurge when paired with crested wheatgrass. Sheep always avoided leafy spurge compared to the alternative forage and consumed an average of only 28% of their intake from leafy spurge during the 30 minute test. In the grazing trials goats took 64% of their bites from leafy spurge compared to 20% for sheep. This represented a relative preference for spurge by goats compared to a strong relative avoidance by sheep. Sheep avoided areas in the pasture that had high densities of flowering spurge stems while goats were relatively unresponsive to stem densities. Goat grazing reduced the number of flowering stems. Stem numbers were 90 vs. 23 flowering stems m2 (P = .04) in sheep- and goat-grazed pastures, respectively. Goats appear to have a greater potential for biological control of leafy spurge than sheep. This advantage may be particularly important in areas where leafy spurge is relatively unpalatable, which the present study site represented.
    • Comparative growth and interference between cheatgrass and yellow starthistle seedlings

      Sheley, R. L.; Larson, L. L. (Society for Range Management, 1994-11-01)
      Annual grasslands in the Pacific Northwest are being invaded by Eurasian weeds, such as yellow starthistle (Centaurea solstitialis L.). Plant-plant interactions influence community dynamics and plant establishment. The objectives of this study were to quantify the effects of interference between seedlings of cheatgrass (Bromus tectorum L.) and yellow starthistle and to compare growth of isolated individuals of these species. Isolated individuals and addition series mixtures with total stand densities ranging from 20-20,000 plants m-2 were grown in an environmental chamber (10 degrees C, 12-hour daylength). Individuals were harvested on 4-day intervals between 10 and 46 days, and mixtures were harvested 37 days after planting. Shoot weight, root weight, leaf area, and total root length of isolated individuals were similar. Yellow starthistle roots penetrated deeper into the soil than did cheatgrass roots 22 days after planting. Intraspecific interference was greater than interspecific interference for both species, and resource partitioning via rooting depth was evident. The yellow starthistle root:shoot ratio and the cheatgrass lower (below 200 mm): upper (above 200 mm) root ratio increased with increasing densities. Yellow starthistle and cheatgrass minimize interspecific interference as seedlings through differential growth and rooting depth. Invasion of cheatgrass rangelands by yellow starthistle increase resource partitioning and reduce our ability to revegetate rangelands by conventional means.
    • Cattle diet quality under short duration grazing on tallgrass prairie

      Mccollum, F. T.; Gillen, R. L.; Brummer, J. E. (Society for Range Management, 1994-11-01)
      Paddocks of tallgrass prairie were grazed at intervals similar to 8-paddock short duration grazing. Two replicates of a 2 X 3 factorial treatment design were evaluated to determine the influence of stocking rate and grazing schedule on crude protein and digestible organic matter content of cattle diets. Stocking rates were 1.3 or 1.8 multiples of the rates recommended by the Soil Conservation Service for the study site. Grazing schedules were 2, 3, or 4 complete cycles during a 152-day grazing season. Grazing and rest periods were lengthened as the season progressed and forage accumulation rate slowed. Masticate samples were collected from the experimental paddocks on alternate days during the grazing periods in 2 consecutive years. No stocking rate by grazing schedule interactions were observed (P > 0.10). Diet crude protein was depressed (P < 0.05) slightly at the higher stocking rate. Diets collected from the 4-cycle paddocks contained more (P < 0.05) protein than diets from the 2- and 3-cycle paddocks. Diets from the 2- and 3-cycle paddocks were not different (P > 0.20). In vitro digestibility was not influenced by stocking rate but tended (P < 0.13) to be higher for the 3- and 4-cycle grazing schedules. The balance of crude protein and digestible organic matter was most favorable (P < 0.05) for the 3-cycle diets. Based on diet composition, more frequent grazing periods appeared to maintain a higher, more stable plane of nutrition than the slower rotation schedules.
    • Cation concentration in post-imbibed winterfat seeds as influenced by imbibition temperature

      Booth, D. T.; McDonald, M. B. (Society for Range Management, 1994-11-01)
      Winterfat [Eurotia lanata (Pursh) Moq.] is a chenopod shrub often used in range seedings because of its palatability and nutritive value. Environmental conditions influence winterfat germination and seedling vigor and, therefore, seedling success. We tested the hypothesis that seed imbibition at warm temperatures damages seed membranes, resulting in lower post-imbibition concentrations of seed cations. Energy-dispersive x-ray microanalysis of Cl uptake and fresh weight increase over time gave evidence that winterfat seeds imbibe more rapidly at 25 than at 4 degrees C. However, imbibition of seeds at 20 degrees C did not result in consistently lower post-imbibition cation concentrations. Although imbibition is more rapid at warm temperatures, the post-imbibition concentration of cations in seeds imbibed at 20 degrees C does not justify the conclusion that warm imbibition damages winterfat seed membranes.