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Increasing attention, resources and efforts are being focused on the conversion of weedy dominated rangelands back to perennial plant communities that resemble predisturbance communities in form, function and composition. A study was conducted in 1998 and replicated again in 1999 to determine whether native plants could be established through “assisted succession” manipulating a cheatgrass-dominated area to perennial plant domination, then to native or near-native diversity. Cheatgrass dominated rangeland that had been successfully revegetated with crested wheatgrass (Agropyron cristatum [L.] Gaertner) was seeded with native species. Another area dominated by cheatgrass, but without crested wheatgrass, was also seeded. Four seedbed preparation methods were investigated: tilling, harrowing, application of a herbicide, and no treatment. Four different seeding methods were used in the 2 areas and 4 seedbed preparation techniques: drilling, broadcasting, a broadcast-cover method, and no seed. Seeding was done in February, and data were collected in mid-summer each year. Native grasses and shrubs emerged in greater numbers on treatments established on the crested wheatgrass matrix than on those established on the cheatgrass matrix. Perhaps in general, but especially in years with normal or below average precipitation, the assisted succession approach proved successful for restoration of native sagebrush-grassland steppe from cheatgrass range.

Repeatedly during the late 19th and early 20 th century, exotic weeds were introduced to the sagebrush (Artemisia)/bunchgrass rangelands of the Great Basin. Once established these weeds became invasive, spreading without the conscious efforts of humans. Brassica elongata ssp. integrifolia (Boiss.) Breistr. offers evidence this process of introduction still continues. Brassica elongata ssp. integrifolia is native to southeastern Europe and Asia. It was first collected in North America near Portland, Ore. in 1911. This initial infestation apparently did not persist. The next collection was near Eureka, Nev. in 1968. Currently, Brassica elongata ssp. integrifolia has spread about 200 km east and west along U S Highway 50 and 100 km north and south of the highway along secondary roads. As a first step in understanding the seed and seedbed ecology of this new invasive weed we investigated the germination of seeds at a wide range of constant and alternating temperatures. This plant produces abundant seeds that germinate over a wide range of constant and alternating temperatures. Maximum germination ranged from 84 to 94% depending on the year of seed production. Germination was extremely limited at very cold seedbed temperatures and low at the cold category of seedbed temperatures. Germination at these temperature is a competitive advantage for other exotic species on Great Basin rangelands. DOI:10.2458/azu_jrm_v56i6_young

Robust needlegrass (Achnatherum robustum [Vasey] Barkw.) is a native perennial that has great promise for use in erosion control, restoration, and ornamental plantings. Seed dormancy can be a problem in developing new native grass cultivars, especially in species of Achnatherum and related genera. Germination response to a wide range of constant and alternating incubation temperatures is also a key parameter in interpreting seedbed ecology of potential planting material. Our purpose was to investigate the germination of robust needlegrass at 55 constant or alternating incubation temperatures from 0 through 40 C. Seeds of robust needlegrass germinate over a wide range of incubation temperatures with maximum observed germination over 75%. In terms of restoration ecology, this means that in contrast to many related grass species, severe seed dormancy is not a limiting factor in seeding technology. Optimum germination occurred with 15 to 20 C warm periods alternating with 0 to 20 C cool periods. The only constant temperature to produce optimum germination was 20 C. The highest germination occurred at what we consider moderate seedbed temperatures, but some germination occurred at 76 to 89% of the temperature regimes tested. DOI:10.2458/azu_jrm_v56i3_young

Bottlebrush squirreltail [Elymus elymoides (Raf.) Swezey] and big squirreltail [E. multisetus (J. G. Smith) Burtt Davy] are short-lived perennial bunchgrasses found on rangelands from the Pacific Coast to the Great Plains and from Canada to Mexico. They are highly variable species with several subspecies described for bottlebrush squirreltail. In many rangeland communities, bottlebrush squirreltail is the transitional dominant native grass in secondary successional communities. There is considerable interest in using squirreltail species in rangeland restoration seedings, but problems with seed collection (disarticulating rachis) have kept seed prices very high. Recently, grass geneticists have begun to develop lines of squirreltail for release as pre-varietal germplasm. Our purpose was to compare the germination at a wide range of constant or alternating temperatures of squirreltail seeds from developmental lines and material collected from native stands. Big and bottlebrush squirreltail seeds (caryopses) germinated over a wide range of temperatures. Seeds of bottlebrush squirreltail produced from the same stand in 3 different years had remarkably similar germination temperature profiles. The greatest variation in germination among accessions occurred at very cold and cold categories of seedbed temperatures. These differences may be very significant in the establishment of seedlings in the field. There was no one temperature regime that always supported optimum germination for all of the squirreltail accessions tested. The regimes most frequently supporting optimum germination were 15/20 and 15/25 C. The seeds of big and bottlebrush squirreltail tested do not have the ecological amplitude of seeds of the competitive exotic weed cheatgrass (Bromus tectorum L.), but they come close. DOI:10.2458/azu_jrm_v56i3_young2

Interest has been expressed in using silver sagebrush (Artemisia cana Pursh ssp. cana) in restoring the Northern Mixed Prairie in Saskatchewan. The objectives of this study were to determine the effects of seedbed manipulation treatments and autumn or spring sowing on establishment of silver sagebrush on sites previously seeded to native, perennial grasses. Seeds (achenes) were sown by broadcasting at 20 pure live seeds m(-2). Seedling emergence ranged from 5 to 6% of seeds sown. Most seedlings emerged in May and June; no seedlings emerged after July or in the second year after planting. Seventy-four to 84% of emerging seedlings survived the first growing season with 96 to 98% of these seedlings establishing. On upland sites, seedling emergence (1.1 seedlings m(-2) SE +/- 0.1) and establishment (0.9 seedlings m(-2) SE +/- 0.1) were similar between autumn and spring sowing and among seedbed manipulation treatments. On lowland sites, seedling emergence (1.4 seedlings m(-2) SE+0.2) and establishment (0.8 seedlings m(-2) SE +/- 0.2) were similar between autumn and spring seeding. Density of seedlings establishing was greatest when the seedbed was tilled. Establishment of silver sagebrush appears primarily limited by low numbers of seedlings emerging, indicating very specific safe site requirements for this shrub. Drastic disturbance of the seedbed is not required to establish silver sagebrush in established stands of perennial grasses. Sowing silver sagebrush in late autumn when temperatures are consistently below 0 degrees C or in early spring immediately after snowmelt is recommended. DOI:10.2458/azu_jrm_v55i3_romo

Placing basins in rangeland seedbeds to capture rainfall has enhanced seeded grass establishment, but it has not been practical on debris-littered land following rootplowing for brush control. A disk chain tested previously will traverse land littered with debris or shrubs while tilling the soil for seedbed preparation. A chain diker is an implement designed to form 10-cm deep basins with a volume of 3.9 +/- 0.9 liters on tilled land. Combining the 2 implements provided tillage, land smoothing and basin formation in the soil with a single pass on debris littered land. Our 4-year study compared established grass densities on disk-chained seedbeds with and without chain diking at 5 locations in west Texas where land was rootplowed for honey mesquite (Prosopis glandulosa Torr. var. glandulosa) control. At 4 locations seedbeds were aerially seeded with 2 kg ha(-1) pure live seed (PLS) of WW Spar bluestem (Bothriochloa ischaemum (L.) Keng). At 1 location a mixture of 6 grasses, including Spar bluestem, was aerially seeded at 2.8 kg ha(-1) PLS. Evaluations were based on established grass densities at the end of the first growing season. At 3 locations, a seeding-before-diking treatment was included to simulate seed dropping from a seedbox mounted over the disk-chain's roller. In the Rolling Plains region of northwest Texas (4 sites), when growing-season rainfall was less than 400 mm, chain-diked seedbeds increased grass densities 2.6 times (P = 0.05) compared to non-diked seedbeds. When growing-season rainfall was greater than 500 mm, grass densities on diked seedbeds were similar to non-diked seedbeds. In the Trans-Pecos region of far-west Texas (1 site), where average growing-season rainfall is 337 mm, diked seedbeds produced 33% greater grass densities (P = 0.05) than non-diked seedbeds with rainfall of 552 mm. Densities of kleingrass (Panicum coloratum L.) and Spar bluestem were significantly greater in the diked seedbeds compared to non-diked seedbeds, and the other 4 grasses were not significantly influenced by seedbed methods. Grass densities were similar whether seeding after diking or before diking. Since long-term, growing-season rainfall has averaged below 500 mm between 65% to 87% of the time at these locations, our data suggests that it would be advantageous to include chain diking in combination with disk chaining for grass establishment on rootplowed land littered with brush debris. DOI:10.2458/azu_jrm_v54i2_wiedemann

In Argentina, Paspalum quadrifarium Lam. (paja colorada) forms tall dense grassland communities in the flooding pampas. Referred to locally as "pajonales", these grasslands generally have very low nutritional value for cattle, except at the post-burn regrowth stage. To improve forage quality and consumption by breeding cattle, Lotus tenuis Walst et Kit. is over seeded immediately after burning of paja colorada pajonales. The objectives of this experiment were to follow the after seeding cover of lotus, evaluate weed control, and assess disease incidence and severity. The experiment was carried out in Azul, Buenos Aires province of Argentina, between September 1993 to September 1996. The postburn seedbed was very favorable for lotus germination and establishment. The most effective chemical weed control was obtained with 2,4-DB used alone or in combination with dicamba. Lotus increased markedly the quality of the pasture forage due to its high crude protein content. Four fungus diseases were found: Botrytis cinerea Pers., Stemphylium sp. Wallroth, Uromyces loti Blytt. and Fusarium spp. Link ex Fr. However, these caused only light foliar damage and did not impair lotus germination or establishment. The overseeding of lotus after burning of P. quadrifarium pajonales, is a very effective technique to improve carrying capacity and animal performance.

Preparing a seedbed and seeding rangeland littered with brush debris normally requires extensive land cleanup before conventional equipment can be used. Our 3-year study compared grass densities on seedbeds prepared with an anchor chain, a disk-chain implement, and the disk chain followed by an anchor chain on land rootplowed for mesquite (Prosopis glandulosa Torr. var. glandulosa) control. Seedbeds were aerially seeded with 1 or 2 kg/ha pure live seed of kleingrass (Panicum coloratum L.). Treatments were applied to a clay loam and sandy loam site each year. Evaluations were based on established grass densities at the end of the first growing season. A heavy-duty, offset disk was included in the seedbed preparation methods during the third year. The chain, disk-chain, and disk-chain+chain implements traversed the log-littered sites without difficulty. Seedbeds prepared by disk-chaining+chaining significantly (p

Winterfat [Krascheninnikovia lanata (Gueldenstaedt) syn. Ceratoides lanata (Pursh) J.T. Howell, syn. Eurotia lanata (Pursh) Moq.] is a native shrub of mixed prairie of North America. A large portion of hydrated seeds and seedlings can be killed when exposed to seedbed desiccation. Winterfat seeds and young seedlings subjected to varying levels of desiccation were studied to measure the influence of this stress. Germination was unaffected (P > 0.05) when seeds were exposed for 0 to 10 hydration-desiccation cycles (2 hours hydration and 22 hours desiccation cycle(-1) at 20 to 30% relative humidity and 20 degrees C). Linear increases in germination rate (0.6% day(-1) hydration-desiccation cycle(-1)), seedling length (0.1 mm hydration-desiccation cycle(-1)), and seed decay (1.5% hydration-desiccation cycle(-1) occurred with an increasing number of hydration-desiccation cycles. Seedling survival following desiccation decreased 10.4% mm(-1) as seedling length increased from < 2 mm to 10-15 mm. Seedling survival was positively correlated with relative humidity and negatively correlated with duration of desiccation. The difference (P < or = 0.05) in survival between 0 and 90% relative humidity was 62% for seedlings 4-6-mm in length and 70% for seedlings 9-11-mm in length. Seedlings from seeds that germinated rapidly were more tolerant of desiccation than those from seeds germinating slowly. After desiccation in 30% relative humidity, survival of seedlings from seeds germinating on the first day of incubation was 40% greater than those from seeds germinating on the third day of incubation. Electrolyte leakage indicated that desiccation damaged cells. Establishment of winterfat seedlings will be favored by seedbed conditions that protect seedlings from severe and prolonged desiccation and allow fast entry of the radicle into soil.

The objective of many laboratory-germination experiments is to develop insight into the process of field establishment. It is relatively difficult, however, to infer potential field response from laboratory data given the enormous spatial and temporal variability in seedbed microclimate. Previous studies have attempted to survey large numbers of alternating day/night temperature regimes in order to estimate germination response to potential conditions of field microclimate. The objectives of this study were to estimate the errors associated with prediction of variable-temperature germination response from fewer, constant-temperature germination data. Non-dormant seeds of thickspike wheatgrass [Elymus lanceolatus (Scribn. and J.G. Smith) Gould], bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) Love], Sandberg bluegrass (Poa sandbergii Vasey), and bottlebrush squirreltail [Elymus elymoides (Raf.) Swezey] were germinated under constant, alternating-constant and sine-wave temperature regimes. Predicted and measured cumulative-germination response generally coincided to within a day for most temperature treatments except for the most slowly germinating subpopulations of seeds. Thermal response models can be parameterized from relatively few experimental data but provide predictive inferences relevant to a wide number of variable-temperature conditions.

Seedbed requirements for the establishment of grasses and legumes were studied in 3 experiments conducted over 3 years (1981-83) on the sandy ( 20 mg kg-1 Bray P) ultisol soils found in the dry tropical rangelands of western Hainan Island, China. Density at the end of the wet season and production accumulated over the growing season (May-October) were the discriminative parameters used. Experiment 1 measured the effect of seedbed preparation (cultivated and uncultivated but heavily grass pasture) on the establishment of 2 grasses, buffel (Cenchrus ciliaris L. cv. Biloela) and sabi (Urochloa mosambicensis (Hack.) Dandy cv. Nixon), sown alone or mixed with 3 stylos (Stylosanthes guianensis (Aubl.) Sw. var. guianensis cv. Graham, S. hamata (L.) Taub. cv. Verano and S. scabra Vog. cv. Seca) on the 2 soil types. Biloela buffel established better and produced more in subsequent years than Nixon sabi grass when sown on a cultivated seedbed, but neither grass established when sown into undisturbed grassland. Companion stylos established on both seedbeds, but initial density and yield was lower on the uncultivated seedbed. However, in 3-year-old swards, stylo yield on uncultivated seedbeds equalled or exceeded yield on cultivated seedbeds. Seca was the most productive stylo, but Graham yielded more consistently between years. Soil type had no effect on sown grass production, but legumes grew better on the sandy soil. Experiment 2 measured the effect of 4 seedbeds (heavily grazed, 1 disking, sprayed with herbicide, and cultivated to fine tilth) on establishment on Verano and Seca stylos on sandy soil. Density of both stylos was highest where grass competition was minimized with herbicide and lowest where heavy grazing was imposed prior to seeding. Compared to herbicide, disking resulted in lower density and yield in the establishment year, but the difference disappeared with time. Burial of seed too deeply and subsequent competition from native species account for the poor performance of both stylos when drilled into a cultivated seedbed which was still evident in 3-year-old swards. Experiment 3 examined the interaction between seedbed type (heavily grazed, burnt, 1 disking, sprayed with herbicide) and superphosphate application. Superior establishment was measured on herbicide and disked treatments and production was still higher in 3-year-old swards than heavy grazing. Burning was more effective than heavy grazing. Increasing fertilizer input improved legume production on all seedbeds, but did not affect density. Reduction in legume yield between 2- and 3-year-old swards in the burnt and disked treatment due to grass competition highlights the need for appropriate grazing to maintain legume content of augmented grasslands. Overall we recommend rough disking as the most practical and cost-effective means to augment native grasslands with stylos. A fine seedbed is recommended to provide the disturbance required to establish grasses. There is no advantage gained by including grasses with legumes oversown into living grassland.

Tolerance to freezing temperatures may be an important factor in the regeneration ecology of winterfat (Ceratoides lanata (Pursh) J.T. Howell). Therefore, growth and freezing tolerance of winterfat seedlings were determined after being grown under different controlled temperatures for 7, 14, 21, or 28 days. Growth of seedlings was greater under day temperatures of 15 and 20 degrees C relative to 5 and 10 degrees C. Freezing tolerance of seedlings was dependent on seedling age and growth conditions. Younger seedlings were more freezing tolerant than older ones grown under the same environmental conditions. Seedlings grown under lower temperatures were more freezing tolerant than those grown under higher temperatures. The lowest observed lethal temperature for 50% mortality (LT50) was -11.8 degrees C for 7-day old seedlings grown under 10/0 degrees C alternating temperatures, and the highest LT50 was about -5 degrees C for seedlings 28 days of age when grown under 29/1 degrees C. Based on seedbed temperatures in the field, the results suggest that freezing temperatures may indeed limit the establishment of winterfat seedlings on Northern Mixed Prairie. Seedbeds with litter accumulations or standing dead plant material may ameliorate low temperature extremes and reduce mortality of winterfat seedlings.

Results from 6 years of seeding trials in the Chihuahuan Desert indicated that establishment of introduced and native grass species responded directly to soil moisture at the 1.22 cm (0.5 in) depth, soil temperature at the 5.08 cm (2 in) depth, and seedbed preparations of mulching and pits. The economic analysis indicated that seeding is not an advisable financial investment in the region under general circumstances. It also showed that when seeding is deemed necessary the best native species economic alternatives are blue grama [Bouteloma gracilis (H.B.K.) Griffiths] with either no seedbed preparation or with post seedbed preparation of mulch. The best introduced species economic alternative is Lehmann lovegrass (Eragrostis lehmanniana Nees.), with no seedbed preparation.

Seedbeds of graze-out wheatland and herbicide-killed wheat (Triticum aestivum L.) were evaluated as were use of a grass drill and the Woodward chaffy grass seeder for Old World bluestem (Bothriochloa ischaemum (L.) Keng) establishment. Seedings were made in 3 consecutive years in western Oklahoma. Steer grazing days on the seedbed treatments, seedling establishment, and second year grass herbage production were measured. Adequate stands were established in either seedbed. Economics favor the graze-out wheat seedbed treatment which produced an average of 189 steer grazing days ha-1 year-1. Adequate stands were established with either the grass drill or the Woodward seeder. Denser stands were usually established with the Woodward seeder--this was unexpected since it is a broadcast seeder. Results with the Woodward seeder are attributed to a requirement for very shallow planting of Old World bluestem and the protected environment of wheat drill furrows and wheat residue. Seedbeds of graze-out wheatland are recommended for Old World bluestem establishment in the Southern Plains.

Environmental conditions in the seedbed are much more variable than have historically been simulated in laboratory germination experiments. This paper describes a laboratory control system for real-time simulation of seedbed temperature regimes. The system is composed of a set of small refrigerators that have been enhanced with incandescent and fluorescent lights, fans and electrical-resistance heaters. The germination chambers are regulated by an electronic data acquisition/control system that allows each chamber to vary internal temperature on a continuous basis. Field temperatures can be transmitted to the laboratory and the germination chambers programmed in near-real-time for simultaneous laboratory germination/field emergence studies.

OSWALD, B. P. (Department of Plant and Soil Science, Alabama A&M University, Normal, AL 35762) AND L. F. NEUENSCHWANDER (College of Forestry, Wildlife and Range Sciences, University of Idaho, Moscow, ID 83843). Mortality of westem larch seedlings in relation to seedbed characteristics at the dry end of its ecological range. Bull. Torr. Bot. Club 122: 101-108. 1995.-The effects of different seedbeds on westem larch (Larix occidentalis Nutt.) germination and seedling mortality were assessed in a grand fir/ninebark (Abies grandis ((Dougl. ex. D.Don) Lindl.))/(Physocarpus malvaceus((Greene) Kuntze)) habitat type in northem Idaho, U.S.A. Two plots were established on each of four sites, and 150 westem larch seeds (66% viable) were distributed on each of 16 randomly applied seedbed modification combinations (bumed or mechanical scarified, mineral soil or duff, shaded or non-shaded, caged or non-caged for protection from predation). Germination percentages and seedling development were significantly greater (4-10 times) on caged units than on uncaged units by midJuly. Shading did not significantly affect germination percentage or initial seedling establishment. No significant differences occurred in germination or initial seedling establishment between bumed and unbumed treatments. Mortality of seedlings, most likely caused by a month-long dry period with high temperatures, resulted in no significant differences in seedling numbers among treatments by mid-August the first year after seed dispersal. On the dry end of this species' range, there does not appear to be any difference in seedling survival from seedbed modification.

This research was designed to identify relationships between T4464 buffelgrass (Cenchrus ciliaris L.) survival and climatic and soil characteristics. At 167 buffelgrass seeding sites in North America we collected climatic and soils data where the grass: 1) persisted over time and increased in area covered (spreads), 2) persisted over time but does not increase in area covered (persists), and 3) declined over time and all plants eventually died (dies). At 30 sites in Kenya we collected climatic and soils data in the area where T4464 seed was originally collected. Only total soil nitrogen and organic carbon differed among survival regimes. Total soil nitrogen and organic carbon concentrations were least where buffelgrass spreads, intermediate where the grass persists and greatest where the grass dies. To predict buffelgrass survival among the 3 survival regimes, and between areas where the grass spreads or dies, we used discriminant function analyses. A model including organic carbon, total soil nitrogen, sand, clay, potassium and cation exchange capacity correctly classified 78% (r2=0.8) of the seeding sites in the 3 survival regimes. A model including sand, total soil nitrogen, calcium, mean minimum temperature in the coldest month, annual precipitation and winter precipitation correctly classified 88% (r2 = 0.8) of the seedling sites between spreads and dies. Survival regime selection prior to brush control, seedbed preparation and sowing will reduce planting failure probabilities, soil erosion and economic losses, and enhance long-term beef production.

Reestablishment of spiny hopsage (Grayia spinosa [Hook.] Moq.) in the shrub steppe requires development of appropriate seeding technology. We examined the effect of planting date and seedbed environment on germination and seedling establishment of 2 seed sources at 2 southwestern Idaho sites. Seedbeds were prepared by rototilling. In 1987-88, seeds collected in 1986 were drilled at 66 viable seeds m-1 of row at Birds of Prey in late fall, winter, and early spring and at Reynolds Creek in late fall, early spring, and late spring. Seeds collected in 1986 and 1988 were broadcast at 400 viable seeds m(-2) at both sites in late fall, early spring, and late spring 1988-89. Seeds in nylon bags were also planted at each site in late fall, winter, and early spring in 1987-88 and in late fall, winter, early spring, and late spring in 1988-89. On each succeeding planting date and in early summer, 5 bags of each seed source from each of the earlier planting dates were recovered. Water content, viability, and germination were compared among seeds from previous plantings and control seeds stored in the laboratory. Each year, first-year seedling establishment at both sites was favored by late fall compared to other planting dates. In 1988, seedlings established only from late fall plantings at a density of 1 m(-2) st each site. In 1989, late fall planting at the 2 sites increased seedling establishment 6 (51 vs 8 m(-2)) and 20 (41 vs 2 m(-2)) times compared to early spring planting. Germination was generally greater for seeds incubated at field sites compared to controls. Germination total and rate increased 6-11 times and 13 days from late fall 1987 to early spring 1988, 1-6 times and 4 and 9 days from winter 1988 to early spring 1988, 17 times and 10-11 days from late fall 1988 to winter 1989, and 4-7 times and 11 days from winter 1989 to early spring 1989. Late fall or early winter planting is essential to permit early spring germination when surface soils are moist.

Heat-induced changes in the soil-solution and post-wildfire erosion can create chemically and texturally diverse seedbed microsites. We quantified organic carbon, extractable NH4+ after incubation (aerobic and anaerobic), and emergence of cheatgrass (Bromus tectorum L.), by particle size fractions, in unburned and simulated burned sagebrush (Artemisia tridentata spp. tridentata Nutt.) subcanopy soil. For all particle size fractions, significantly (P less than or equal to -O.05) more extractable NH4+ and significantly less extractable N03- were measured in heated material as compared to unheated material. Heated treatments had significantly more NH4+ and significantly less N03- mineralized after 11 days aerobic incubation than after unheated treatments; net N mineralized tended to be higher for all particle fractions in heated treatments than in unheated treatments. Emergence of cheatgrass under aerobic conditions was significantly retarded in all heated treatments. Elevated NH4+ to N03- ratios in the soil-solution following heating does not explain suppression of cheatgrass emergence. Nitrogen mineralization, before and after simulated burning, is adequate in all particle size fractions to support the needs of germinating seeds. Nitrogen mineralization was not enhanced by the presence of growing cheatgrass plants.

Kochia scoparia (L.) Schrad. invades disturbed soils and serves as a pioneer species on saline rangelands and sodic mine spoils. The percent germination of kochia seeds declined with increasing salinity, averaging -3.3%/dS/m between 12 and 30 dS/m. The emergence and early survival of kochia seeded into 2 media whose respective saturated-paste extracts averaged 1 and 18 dS/m in electrical conductivity (ECe) were investigated in a greenhouse under simulated rainfall regimes. Water was applied according to 3 average rates: 0.6 mm/day (low); 1.2 mm/day (medium); 2.5 mm/day (high). These rates were administered in 2 phases. Phase I (14 days) involved low and medium on the nonsaline seedbeds, and medium and high on the saline seedbeds. Phase II (42 days) followed sequentially on only the saline soil in Phase-I:II combinations of high-high, high-medium, medium-medium, and medium-high. Kochia seedlings did not emerge under the low rate. Seedlings did emerge from the nonsaline seedbeds when watered at the medium rate, but failed to emerge from the saline seedbeds treated only at this rate. Seedlings emerged from the saline soil under all regimes that included the high rainfall rate. About 30 plants successfully emerged from every 100 seeds sown in the seedbeds where ECe decreased to 15.7 dS/m or less. Despite the severely saline seedbed, kochia emerged within 3 days at a rate of 8 plants/day under the Phase I high regime because the water apparently diluted saline seedbed-solutions sufficiently for germination to occur. Phase II of the medium-high regime stimulated a similar response but only after 13 days under the wetter rate. Kochia's germination and emergence favor its addition to seed mixtures designed to establish forages in saline soils.

The germination ecology of antelope bitterbrush [Purshia tridentata (Pursh) Nutt.] seed has probably been investigated more than any other range shrub. Seeds of this valuable browse species are known to require moist prechilling before they will germinate. Our purpose was to investigate the nature of this dormancy breaking by placing packages (2 X 2-mm mesh screen) of seeds on the surface and buried in the seedbed at several locations in Idaho and Nevada and to recover the seeds monthly through the winter. The seeds were categorized based on their being: (a) capable of germinating; (b) dormant; or (c) dead at each recovery. The seedbeds of the 2 sites in Nevada, during 2 years of drought, were not sufficiently wet to bring large amounts of the antelope bitterbrush seeds out of dormancy. The seeds did not rot in the field, and being protected from predation, they remained dormant in the seedbed. The highest elevation site in Idaho had as high as 80% of the seeds lose dormancy. If seedbed microenvironmental conditions were satisfactory, the inherent seed dormancy was lost by midwinter. Snow cover, as it influences seedbed moisture and temperatures, apparently is an important factor in the prechilling of antelope bitterbrush seeds.

OSWALD, B. P. (Department of Plant and Soil Science, Alabama AM shading, moss, and large vegetation were not significantly effected by treatment. Seven western larch (Larix occidentalis) seeds were distributed after burning treatment on each sample point, and the number of germinations, germinants and seedlings were tracked over two growing seasons. Germinations (741) and germinants (656) from 17,500 seeds occurred on a wide variety of burned and unburned microsite types. Microsite types with successful germination, germinants, and seedling establishment are the "safe sites" (seedbed with proper conditions) for these stages of seedling development. Safe site requirements became more specific as the seedling developed, with only 47 seedlings surviving to the end of the first growing season. Seedlings survived on safe sites which represented 1.5% of the -total area. The eight physical characteristics used to describe microsite types were evaluated with discriminant analysis for significance at each seedling stage. Significant variables and interactions were identified for regression. Analysis produced high (R2 = 0.75) predictability at the end of the first growing season for initial seedling establishment. Safe sites are described for seedling establishment, with site, seedbed treatment, shading and moss as significant variables. The safe site concept appears useful in evaluating germination and initial establishment of western larch.

Patterns of past fire incursions and tree falls were documented in a tropical riparian forest. Fire-scarred trees were concentrated on gentler slopes near the savanna:forest boundary, while tree fall sites were of highest frequency on convex upper valley slopes. Most tree falls were in a down-slope direction while the remainder were concentrated in directions that suggested an origin in extreme winds of atypical orientation. Tree species response to these two forms of disturbance was evaluated by assuming that the zones identified were inherently more disturbanceprone, and comparing the tree populations within and beyond the areas identified. Fire incursions had a larger measurable effect in augmenting species richness: 19% of species evaluated were significantly more abundant in burned zones, while only 8% of those evaluated were more abundant in tree fall zones. This difference is tentatively attributed to fire having a larger proximal effect on tree species recruitment as well as a spatially more persistent pattern of occurrence. Observations made at sites of recent fire incursion indicated that this caused little tree death or canopy opening but eliminated seedlings, saplings, litter and root mats: it thus created new seedbed conditions without the high light levels that would promote herbaceous establishment. Both disturbances play an augmentative, rather than exclusive, role in promoting species coexistence in these forests: they provide a varied micro-environment for seedling establishment but their patchy distribution ensures that disturbance-sensitive species can persist elsewhere in the forest patch.

Bur buttercup (Ranunculus testiculatus Crantz) is an alien annual species that has spread rapidly through range and croplands in the western United States. This species is potentially poisonous and is currently a weed in cereal grain fields. We investigated the germination of the achenes (seeds). About 30% of the seeds of bur buttercup germinated without pretreatment, but only at cool to cold temperatures (maximum germination 28% at 5 degrees C). Germination was not enhanced by light, washing, or prechilling of seeds. Acid scarification for 25 minutes increased germination. Enrichment of the germination substrate with 0.289 mmol L-1 gibberellic acid (GA(3)) and 0.01 mol L-1 potassium nitrate (KNO3) synergistically enhanced the germination of acid scarified seeds. Incubation of seeds pretreated in this manner at 55 constant or alternating temperatures resulted in maximum germination of 70%. All temperature regimes with optimum germination (defined as not lower than the maximum observed and one-half its confidence interval at 0.01 level of probability) occurred at relatively cool temperatures. Temperatures above 30 degrees C greatly suppressed or inhibited germination. Embryonic plants dissected from the achene costs had 60% germination without additional pretreatment, but only at cool to cold incubation temperatures. The germination-dormancy requirements of bur buttercup seeds are obviously complex, but about 30% of the seeds appear adapted for germination at cold seedbed temperatures, which fits with the extreme ephemeral growth habit of the species.

Laboratory tests are often conducted to determine seed germination responses to temperatures for seedbed ecology interpretations and revegetation seeding rate calculations. To determine the utility of laboratory germination tests for indicating seedbank germinability of lovegrasses we measured seedbed temperatures and soil water on 2 semidesert grassland sites in the Southwest. We also tested germination of Lehmann lovegrass (Eragrostis lehmanniana Nees), 'Cochise' lovegrass (E. lehmanniana Nees X E. trichophora Coss & Dur.), and plains lovegrass (E. intermedia Hitch.) seed collections associated with natural or artificial revegetation studies on these 2 sites in relation to an array of constant and alternating temperatures. Germination responses to different temperatures varied with the year and source of collection and seed age and differed compared to those reported in the literature. Lehmann and Cochise lovegrass had high germination at temperature alternations similar to wet seedbed temperature extremes in December (0,2/15 degrees C) and these species and plains lovegrass were germinable at moderate temperature alternations representative of wet seedbeds in April (10/30 degrees C). Ability to germinate in laboratory tests at these temperatures is not necessarily indicative of germinability in the field for Lehmann lovegrass, which has been observed to germinate in April, not December, in wet seedbeds. All species had maximum or near maximum germination at a temperature alternation of 20/40 degrees C, which is similar to wet seedbed temperature extremes during the summer rainy period when these species usually emerge. Because of the variability in germinability of different seed collections of lovegrass over time, specific collections should be tested at specific ages relevant to seedbed ecology and revegetation studies or projects. Laboratory germination tests which mimic actual wet seedbed temperature curves might be more predictive of seedbed germinability than the usual tests which expose the seeds to abrupt temperature alternations.

Seed imbibition is a critical first step in the awakening of an embryo plant. To determine if imbibitional conditions influenced post-germination growth, seeds of 3 winterfat (Eurotia lanata) ecotypes were imbibed at 5 temperatures from 0 to 20 degrees C, and at 5 oxygen concentrations from 0 to 40%. After a 4-day imbibition period the seeds were either dried and weighed or they were cultured in the dark at 20 degrees C. Seedling axial length was measured 5 times between 5 and 14 days post-germination to assure that maximum growth was measured. The study was repeated 3 times for each ecotype. Oxygen concentration had little effect except at 0%. As imbibition temperature increased both post-imbibition dried seed weight and seedling axil length decreased. This indicates the probability for successful termination, establishment, and survival of winterfat decreases when seeds are imbibed at 15-20 degrees C as compared to 5 degrees C. Therefore winterfat should be sown during those parts of the year when diaspores will imbibe at cool temperatures. Winterfat should be imbibed and held at 5 degrees C for 4 days, then germinated at 15 degrees C when testing germination.

Lebmann lovegrass (Eragrostis lehmanniana Nees.) is a perennial, warm-season bunchgrass that is native to South Africa and has been seeded and spread naturally in the southwestern United States. Germination of 4 seed lots of varying age was tested in relation to darkness and irradiance with red (R) and far-red (FR) light. Germination was low in continual darkness, but greatly increased after exposure to R. Irradiation with FR after exposure to R reduced germination, confirming phytochrome involvement. Exposure to R after prolonged imbibition in FR did not increase germination of 1-2-year-old seeds and only slightly increased germination of older seeds. An alternating temperature of 16 hours at 15 degrees C and 8 hours at 38 degrees C greatly increased germination of seeds exposed to fluorescent light and slightly increased germination of seeds in darkness compared to a constant temperature of 25 degrees C. Greater seedling emergence of Lehmann lovegrass when the canopy is opened by burning, mowing, or grazing is likely a function of red light stimulation of biologically active phytochrome and increased seedbed temperature fluctuations.

Low vigor of seedlings and stand failures plague many revegetation efforts in semiarid and arid rangelands. Phototoxicity, sandbur (Cenchrus incertus M.A. Curtis) competition, seedbed preparation (plowing vs. disking), and nitrogen (N) fertilization were studied as reasons for low vigor of Ermelo weeping lovegrass [Eragrostis curvula Schrad.) Nees] seedlings on sand shinnery oak (Quercus havardii Rydb.) range in west Texas. Oak leaf residue and sandbur-dominated grass residue extracts did not affect seed germination and initial shoot growth of lovegrass seedlings. However, these residue extracts reduced root length 92% and 21%, respectively. Survival of weeping lovegrass seedlings was not affected by even 65 sandbur plants/m2. But, herbage yield was reduced 65, 72, and 79% with 30, 45, and 65 sandbur plants/m2. Early in the growing season, unfertilized plowed (P) plots had 5.6 ppm N in the 10-20 cm soil layer compared to a maximum of 3.9 ppm on other seedbed treatments. In the surface 10 cm, the P plots had less N than the disked plots. Surface-applied N fertilizer accumulated in the upper 10 cm of soil and promoted weed growth without improving weeping lovegrass stands or seedling vigor. Weeping lovegrass seedling vigor was greatest on P and least on disked plots. Thus, plowing buried weed seeds better, put resident N more deeply into the soil for better root uptake, removed allelopathic residues from seedling contact better, and provided for much higher seedling vigor than the disked seedbeds.

Successful germination and establishment of grass seedlings from surface-sown seeds requires a microsite which provides adequate soil water and temperature conditions, among other species-specific requirements. The microsite where these requirements are met has been termed a "safesite". Safesites may occur naturally as cracks and depressions in the soil surface, gravel, and plant litter, or be prepared by seedbed equipment and livestock trampling. A greenhouse study was conducted to determine the influence of seedbed microsite characteristics and soil water treatments on seedling emergence of 'Vaughn' sideoats grama (Bouteloua curtipendula (Michx.) Torr.), 'A-130' blue panic (Panicum antidotale Retz.), and 'Cochise' Atherstone lovegrass (Eragrostis lehmanniana Nees X E. tricophera Coss and Dur.). Although there were several interactions, in general, emergence of all 3 species was highest from gravel, followed by litter, cracks, and finally the bare soil surface. Bare surface sites decreased in water content more quickly than the other sites. Cochise lovegrass had high emergence in gravel under all water treatments. Small-seeded species such as Cochise lovegrass broadcast on coarse-textured surface soils may establish with minimal seedbed preparation, provided summer precipitation is adequate.

Under usual range conditions, the time between blue grama (Bouteloua gracilis) germination and adventitious roots development is such that it is rare that both of these events occur with moist soil conditions, and seedling survival is infrequent. Establishment could be enhanced if the time between germination and adventitious root development were reduced. Dehulling followed by pretreatment of seeds with selected hormones such as indoleacetic acid reduced the time between these 2 events, and may increase the probability of successful seeding. These treatments also increased the length and number of adventitious roots during early stages of development. Water injection into the planting rows at seeding time added to the beneficial effects of seed treatment, while chemical mulching detracted from these responses.

Location of seeds in the seedbed may affect germination and seedling establishment of range grasses. Our objective was to determine the effects of trampling by livestock and mechanical seedbed preparation on burial of grass seed on a sandy loam seedbed. Plots were root plowed or ripped then broadcast seeded, or broadcast seeded then lightly or heavily trampled by cattle or land imprinted before summer rains. Seedbeds were sampled by extracting soil plugs with plastic vials, splitting the plugs, and determining seed location with a dissecting scope. Sampling occurred after treatment, after summer thunderstorms, and after seedling emergence. An average of 75, 42, 17, and 7% of seeds found were buried immediately after heavy trampling, land imprinting, light trampling, and no disturbance, respectively. After summer thunderstorms an average of 78, 72, 63, 40, and 29% of seeds found were buried on plots root plowed or ripped, heavily trampled, imprinted, lightly trampled, and undisturbed, respectively. Although high percentages of seeds were buried on plots heavily trampled, imprinted, and root plowed or ripped, many of these seeds were too deep for seedling emergence. Smaller-seeded blue panic (Panicum antidotale) and the lovegrasses (Eragrostis lehmanniana Nees and Eragrostis lehmanniana Nees XE. trichophera) were buried by treatment and rain better than sideoats grama [Bouteloua curtipendula (Michx) Torr.].

Cattle trampling has been recommended to bury seeds and encourage seedling establishment but has not been compared with traditional seedbed preparation techniques. We compared seedling emergence of broadcast-seeded 'Vaughn' sideoats grams [Bouteloua curtipendula (Michx.) Torr], 'A-130' blue panic (Panicum antidotale Retz.), 'A-68' Lehmann lovegrass (Eragrostis lehmanniana Nees), and 'Cochise' atherstone lovegrass (Eragrostis lehmanniana Nees X E. tricophera Coss and Dur.) on lightly and heavily trampled seedbeds with that on undisturbed, land imprinted, and root-plowed or ripped seedbeds. We seeded and applied the treatments prior to summer rains on a sandy loam soil in southern Arizona for 3 years. In a wet year (1987) when surface soil water was estimated to be available for at least 24 consecutive days, heavy trampling and land imprinting increased emergence of blue panic and land imprinting increased emergence of Cochise lovegrass. In that year, lovegrass emergence was high even on undisturbed plots. In a moderately wet year (1988), surface soil water was available for periods of 6-9 days during seedling emergence and greater disturbance, either by heavy trampling, land imprinting and/or root plowing or ripping produced higher emergence than light trampling and nondisturbance. In a dry year (1989), surface soil water was available for periods of 2-3 days and seedling emergence was low and generally similar for all treatments. Sideoats grama emergence was low all 3 years, but was highest in 1988 when initial thunderstorms were followed closely by subsequent storms. Seedbed disturbance by cattle and mechanical methods may enhance revegetation in the Southwest in years of moderate precipitation but may be unnecessary in wet years or futile in dry years, depending on species and soils.

Indian ricegrass (Oryzopsis hymenoides (Roem. & Schult.) Ricker) is adapted to sandy arid areas of much of the western USA and is a highly desirable species on winter range sites. Seed is typically highly dormant. Mechanical dormancy has been reduced by mechanical and sulfuric acid scarification, and physiological dormancy has been reduced with stratification, giberellic acid, and kinetin. A better understanding of the relationship between mechanical and physiological dormancy may lead to a practical procedure for breaking dormancy in harvested seed. Alternatively, a better understanding of environmental factors on seed production may lead to production of already low dormancy seed. Establishment success will also depend on development of appropriate seedbed management practices for various soils. Reduction of the currently large shattering losses would have a favorable impact on the economics of Indian ricegrass seed production. An interdisciplinary approach including seed physiology, seedbed ecology, seed technology, and plant breeding can potentially solve these problems. The potential of seeding Indian ricegrass for improving rangelands can only be realized after low dormancy seed becomes available, appropriate seedbed management practices are developed, and seed shattering losses are reduced.

The emergence of big sagebrush (Artemtricr frkfeufotcr) seedlings from 5 gardens where both the seed source and the soils were reciprocated was investigated over a g-year period in western Nevada. The sites where the study was conducted were located at the arid extremes for mountain (A. rrGfenturu subsp. vareyuna) and basin big sagebrush (A. tridentata subsp. tridentata) in the transSierra Nevada area. Soils, sites, and seed sources differed significantly (FO.01) in seedling emergence. The driest site, where it was difficult to obtain seedling emergence even on a year of above average precipitation, had a soil surface that was very conducive to the germination of seeds of big sagebrush when the seedbed was moved to garden locations with greater environmental potential. Seedbed quality differed markedly among sites with soil derived from decomposing granite versus metavolcanic sources. Big sagebrush seeds were buried in soils derived from granite through a winnowing action. Seeds from a non-granltlc soil site were also adapted, apparently through size and shape, to this winnowing self-burial. The dominant microenvironmental factors contributing to seedling emergence tended to be site and seed source specific. Microtopography in the fall, when seeds were dispersed, and seasonal precipitation were dominant factors controlling the emergence of big sagebrush seedlings.

Altai wildrye (Leymus angustus (Trin.)Pilger) is recommended for late season forage and stabilization or improvement of salt affected land in the northern Great Plains. Establishment from seeding is erratic, perhaps due to environmental extremes that occur in the seedbed. Objectives of this study were to evaluate the effect of temperature and moisture variation on germination, solute leakage from seeds, and etiolated growth of seedlings of this perennial grass. Seeds were subjected to 5 preincubation treatments: stratification (5 degrees C) (STR); stratification plus drying (30 degrees C) (STR-D); stratification plus freezing (-10 degrees C) (STR-FR); cool-dry storage (5 degrees C) (COOL); and laboratory storage (LAB). After pretreatment, seeds were incubated at 10 and 20 degrees C in a gradient of osmotic potentials ranging from 0.0 to -1.59 MPa. Solute leakage from seeds and seedling growth were also assessed following pretreatment. Germination was higher and more rapid over the range of osmotic potentials at 20 degrees C than at 10 degrees C with germination poorest in STR-FR. In the absence of water stress, leakage of solutes was 21% lower from stratified seeds than unstratified seeds; leakage at -0.48 MPa was similar across pretreatments. Compared to the other pretreatments, root and shoot growth of seedlings following STR-FR were reduced 34 and 76% at -0.48 MPa. Negative effects of STR-FR were reflected in restricted germination and growth, but not in solute leakage. Results of this study and others suggest that efforts to minimize temperature extremes in the seedbed could improve germination and seedling growth of Altai wildrye.

AbStlWt The upward movement of &orbed salts within plant ia innuaced by the transpiration stream. This study tested the hypothesis that transpiration by winterfat mother plants effects seedling vigor. Mature plants, growing in a greenhouse, were exposed to forced air and measurements were made on water loss from the plants, concentrations of Ca*, MI’+, Na+, and K+ in the diaspores, 8nd on offepring growth par8meters. The dixsporee produced by the plants were germinated and grown under 2 identical temperature regimes, except that 1 regime included 1 hour of dark-period freezing strew. The forced-air treatment had no detectable effect on mother plants, including no significant (pIO.05) effect on water loss or on cxtion concentrations in the diespore. However, it did signlflcantly decrease offspring vigor. Analysis of the total test-plant population revealed significant, linear relationships between water loss and: diespore yield, Ca* and K+ concentrations in the &pore, seedUng dry weight, and seedling hypocotyl length. Liacu relationships between seedling variables and covariables provided evidence that Ca*, K+ and Na+ influence seedling weight, moisture, and hypocotyl length. It is concluded that mother-plant transpiration, windstress, and nutrition affect offspring vigor.

Seed of Texas persimmon germinated in excess of 90% at constant temperatures from 20 to 300 C, and in an alternating temperature regime of 20-30? C. Seeds germinated equally well in light and dark. No seed dormancy mechanisms were observed, and viability was not reduced after storage at room conditions for 2 years. Germination percentages of seeds collected from 2 contrasting range sites did not differ. Germination did not differ over a broad range of pH values (4 to 11), but radicle elongation was inhibited at pH 11. Germination and radicle length were sensitive to osmotic potentials of 0.2 MPa or more, and no seed germinated at 1.2 MPa. Germination was restricted in a 5 g/l NaCI solution and nearly ceased at 10 g/l NaCl. Radicle length was more sensitive to NaCl solutions than was germination. Ion toxicity of salt solutions appeared to be more detrimental to germination and radicle growth than the osmotic potential of salt solutions. Seeds were not dependent on soil cover for seedling establishment, but the highest emergence occurred when seeds were covered with 1 cm of soil. Percent of germination was not reduced by passage through the digestive tracts of coyotes. Texas persimmon (Diospyros texana), also called "black" and "Mexican" persimmon is a native shrub or small tree found in rocky open woodlands, open slopes, arroyos, and other such places throughout the western two-thirds of Texas (Correll and Johnston 1970). Highest densities occur in a group of 13 counties in southcentral Texas from the southern edge of the Edwards Plateau into the northern South Texas Plains (Scifres 1975). It is usually 2 to 3 m tall, but may attain a height in excess of 6 m. Texas persimmon fruits are an important wildlife food (Vines 1960, Arnold and Drawe 1979), but this species is often a deterrent to effective range management. Although usually considered a minor component of range vegetation, Texas persimmon may become one of the primary problems following use of mechanical brush control methods such as chaining and root plowing (Scifres 1975, 1980). Moreover, it is a hard-to-kill species that is essentially resistant to conventional herbicides applied as broadcast sprays. Because its roots extend laterally a great distance from the parent plant, it is also resistant to most mechanical control methods (Scifres 1980). Little is known of the life history or biology of Texas persimmon. The major objective of this study was to determine the germination response of Texas persimmon seeds in the laboratory to certain environmental factors encountered in the seedbed. The effect on seed germination after passing through a coyote digestive tract was also studied. Materials and Methods Texas persimmon seeds were collected in August 1980 from several plant populations growing on a gray sandy loam range site (Aridic Ustochrepts) near La Joya in Hidalgo County, Texas. Only fully developed, undamaged seeds were used for germination experiments. Prior to use in experiments, seeds were stored at room conditions (20 to 270C, and 50 to 75% relative humidity). Author is range scientist, Agricultural Research Service, U.S. Department of Agriculture. This study is a contribution from Remote Sensing Research, Southern Region, Agricultural Research Service, USDA, Weslaco, Texas 78596. The author wishes to thank Mario Alaniz for his assistance in both the field and laboratory. Manuscript received February 14, 1983. With the exception of periodic determination of germination over a 2-year period, the various experiments were conducted when the seeds were less than I year old. All experiments were conducted in small growth chambers with automatic temperature and fluorescent light (200 MAE/m2/s) controls. Unless otherwise stated, experiments were conducted at a constant temperature of 25?C (optimum) with an 8-hr light period. An experimental unit was 10 seeds in a 15-cm petri dish that had 2 filter papers wetted with 20 ml of distilled water or an appropriate test solution. Experiments were designed as randomized complete blocks unless otherwise stated. Treatments were replicated 10 times, and each experiment was conducted twice. Seeds with 2-mm long radicles were considered as germinated. Germination was recorded 14 days after the initiation of each experiment. Radicle lengths were recorded in selected experiments. Seeds were germinated under continuous temperatures of 15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5, 35, and 40?C (8-hr light period, 16-hr darkness) and alternating temperatures of 10-20, 15-25, 20-30, and 25-35? C (16-hr low temperature in darkness, 8-hr high temperature with light) (Mayeux and Scifres 1978, Mayeux 1982, Everitt 1983a). The effects of simulated moisture stress on seed germination were evaluated by adding polyethylene glycol (PEG-6000) to distilled water for the substrata-PEG-6000 concentrations required to give osmotic potentials over a wide range of temperatures are given by Michel and Kaufman (1973). Their results were used to prepare solutions ranging from 0 to 1.2 MPa at 25?C (1 MPa = 10 bars). The pH of these PEG solutions was 6.7. Tolerance to salinity during germination was evaluated with aqueous solutions of NaCl at concentrations of 0, .25, .5, .75, 1,2.5, 5, and 10 g/l. The influence of substrate pH on germination was investigated by adjusting the pH of distilled water with HCI and KOH (Mayeux and Scifres 1978). Percent germination was evaluated at pH values of 2, 3, 4, 5, 6, 7, 8, 9, 11, and 12. Light requirements for seed germination was investigated by comparing germination in petri dishes covered with aluminum foil with germination in uncovered dishes. The effect of age on germination was investigated by comparing germination at 1, 6, 12, 15, 18, 21, and 24 months after seed collection. The influence of planting depth on seed germination was studied in the greenhouse. Temperatures in the greenhouse ranged from 21 to 28?C. Ten seeds were planted in soil in large pots (16 cm diameter X 16 cm height). A potting mixture of 3 parts sandy loam :1 part peat moss: 1 part perlite was used to prevent crusting. Seeds were placed on the soil surface and also covered to depths of 1, 2,4, 5, and 7 cm. Seedling emergence and height were recorded after 60 days. Seeds were also collected from several plant populations growing on a shallow sandy loam range site (Ustollic Paleorthids) in northern Hidalgo County in August 1980, and their germination was compared with that of plants from the gray loam site. During August 1979, seeds were recovered from fresh coyote feces from the gray sandy loam site near La Joya and their germination was compared with that of control groups of seeds from this same site. Seeds were taken from approximately 50 fecal samples. Three-hundred seeds from fecal samples and 300 control seeds JOURNAL OF RANGE MANAGEMENT 37(2), March 1984 189 This content downloaded from 157.55.39.17 on Fri, 02 Sep 2016 04:46:44 UTC All use subject to http://about.jstor.org/terms were placed in a growth chamber at 300 C. Each experimental unit consisted of 10 seeds in a 15-cm petri dish containing 2 filter papers wetted with 20 ml of distilled water. Treatments were replicated 10 times and each experiment was conducted 3 times. Percentage germination and emergence data were transformed (Arcsin) before statistical analyses. Data from 2 or 3 experiments were pooled prior to analyses. Data were subjected to analysis of variance and Student's t-test. An LSD was calculated in selected experiments (Steel and Torrie 1960). All statistical comparisons were made at P>0.05. Results and Discussion Germination of Texas persimmon seed appears to be restricted to a relatively narrow temperature range (Fig. 1). Germination was >93% at constant temperatures of 20-30? C, but decreased abruptly

We investigated germination of seeds (achenes) of curlleaf cercocarpus (Cercocarpus ledifolius Nutt.) by applying a series of treatments to determine the nature of dormancy. Germination was enhanced when seeds were soaked for 3 weeks in an aerated solution of 1.0 mmole KNO3 and 0.035 mmole potassium gibberellin (GAs) maintained at 5 C. Once dormancy was broken, seeds germinated over a wide range of constant and alternating temperatures. Germination was best at 10 C. Soaked seeds could be dried for delayed planting, but once the seeds were dried and remoistened, enhanced germination was restricted to a very narrow range of temperatures. J. WILDL. MANAGE. 42(3):614-620 On many winter ranges for big game in the western United States, there is a vital need to reestablish browse species. Curlleaf cercocarpus would be an excellent species for revegetation either by sowing or through encouragement of natural regeneration. The evergreen foliage of this species is highly preferred by mule deer (Odocoileus hemionus) on winter ranges (Smith 1950). Seeds of curlleaf cercocarpus can be collected from the occasionally abundant crops in old growth stands (Plummer et al. 1950). Most attempts to establish this species by direct seeding have failed, probably because dormancy has impaired germination (Liacos and Nord 1961). In the single detailed study that has been published, the germination of curlleaf cercocarpus was increased from 17 percent for untreated seeds to 75 percent for seeds treated with sulfuric acid and thiourea (Liacos and Nord 1961). We observed no natural regeneration in hundreds of old growth stands of curlleaf cercocarpus in the Great Basin, despite periodically abundant seed crops. Much of the production in these stands is out of reach of browsing animals. Germinating seedlings are rarely seen in the field. Thompson (1970) reported that in the second growing season after pruning, curlleaf cercocarpus plants produced an abundant crop of seeds that germinated naturally, but establishment was limited. What factors in the seedbed ecology of this species interact to limit germination? We undertook the study reported herein as a first step toward answering this question and to develop a means of providing wildlife-habitat managers with germinable seeds. MATERIALS AND METHODS Seeds (achenes) were collected from native stands of curlleaf cercocarpus growing near Verdi, Nevada, in 1971, 1972, 1974, and 1975. After harvest we allowed the seeds to reach moisture equilibrium in paper bags before screening to remove trash and leaves. Unless otherwise specified, we did not rub the seeds free of the dried, plumose style that forms the outer covering. I Cooperative investigations of the Science and Education Administration-Federal Research, U.S. Dept. of Agr., Renewable Resources Center, Univ. of Nev., 920 Valley Road, Reno, Nev. 89512; The Pacific Southwest For. and Range Expt. Sta., For. Serv., U.S. Dept. of Agr.; and the Agr. Expt. Sta., Univ. of Nev., Reno. Journal Series No. 355. 614 J. Wildl. Manage. 42(3):1978 This content downloaded from 157.55.39.196 on Sat, 24 Sep 2016 04:34:38 UTC All use subject to http://about.jstor.org/terms GERMINATION OF CURLLEAF CERCOCARPUS? Young et al. 615 Table 1. Preliminary tests to determine effect of various preincubation treatments on dormancy of curlleaf cercocarpus seeds.a Test Variable tested Preincubation treatment No. 1. Dissection Seeds dissected from plumose covering, or pericarp ruptured. 2. Heat a) Seeds dipped in boiling water; b) seeds dropped into boiling water and steeped while water cooled; c) feathery styles burned; or d) seeds dry heated at 60, 70, 80, or 90 C for 5, 10, 15, or 30 min. 3. Washing Seeds placed in running tap water for 1, 2, 3, or 4 weeks. 4. Stratification Seeds stratified on moist blotter paper or in vermiculite at 0, 2, or 5 C for 2, 4, 6, 8, or 12 weeks. 5. Potassium nitrate (KNO3) Addition of 0.01, 0.1, 1.0, or 100 mmole of KNO3 to germination substrate. 6. Gibberellin (GA3) Addition of 0.001, 0.035, 0.07, 0.14, or 0.28 mmole of GA3 to germination substrate. 7. GA3 + KNO, Addition of 1.0 mmole KN03 plus 0.035 mmole GA3 to substrate. 8. Concentrate sulfuric acid Seeds soaked for 1, 5, 10, 15, 20, or 30 min in (H2SO4) concentrated H2SO4, then washed and neutralized. 9. Thiourea Control seeds and seeds soaked in H2SO4 for 5 min were soaked in a 3 percent aqueous solution of thiourea for 1, 2, 3, or 4 h. 10. Organic solvents Seeds soaked for 1, 5, 10, 15, or 30 min in acetone, methyl chloride, or 1 percent hydrogen peroxide solution, and then washed. 11. Light Germination in dark (in light proof containers) compared with that in white light and in white light after 24-h exposure to filtered red light. a Seeds were incubated at 10 or 15 C for 4 weeks after each pretreatment except in Tests 3, 8, and 9 (see Table 2). In all germination tests we placed 4 replicates of 100 seeds each on nontoxic germination toweling in petri dishes. The seeds were moistened with tap water and incubated in dark germinators for 4 weeks, with germination counts after 1, 2, and 4 weeks. Seeds were considered germinated when the radicle had emerged 1 cm. We allowed some seedlings to continue development to be certain that radicle and plumule development proceeded. In 1971, using 6-month-old seeds, we began screening tests to determine the causes of dormancy in seeds of curlleaf cer ocarpus. Seeds were incubated at 2, 5, 10, 15, 20, 25, 30, 35, or 40 C without pretreatment. Other seeds were pretreated as shown in Table 1 and incubated at 10 or 15 C (Tests 1, 2, 4-7, 10, and 11) or at 2, 5, 10, 15, 20, 25, or 30 C (Tests 3, 8, and 9). We also conducted germination tests 2, 6, and 12 months after harvest to check for afterripening requirements. All trials were conducted with seeds from each location and each annual collection. In later tests we soaked seeds for 3 weeks in aerated and nonaerated water baths maintained at 5 C. For aeration, compressed air was rapidly bubbled J. Wildl. Manage. 42(3):1978 This content downloaded from 157.55.39.196 on Sat, 24 Sep 2016 04:34:38 UTC All use subject to http://about.jstor.org/terms 616 GERMINATION OF CURLLEAF CERCOCARPUS? Young et al. through the soak water. In some tests we replaced the soak water with solutions of potassium nitrate (KNO3) (1.0 mmole), potassium gibberellin (GA3) (0.035 mmole), or both. After the soaking treatment we incubated the seeds at constant or alternating temperatures. The constant temperatures were 2 C and (at 5-degree increments) 5 C through 40 C. The alternating-temperature regimes were daily cycles of 16 h at each given temperature and 8 h at each higher temperature. Some presoaked seeds were saved and dried at 30 C until moisture equilibrium was attained. These dried seeds were then remoistened and incubated at all constant temperatures. The data were subjected to analysis of variance, and significant differences were identified with Duncan's multiple

Plant succession on Picea (spruce), Pseudotsuga (Douglas fir) and Tsuga (hemlock) logs in the Hoh Rain Forest, Washington, was examined using the chronosequence method. Bark fragmentation patterns differed among these species; Picea and Tsuga logs lost their bark in 60 years and Pseudotsuga in 190 years. Bark of logs of all species was 85-90% covered by bryophytes within 11-19 years after tree fall. Live and dead bryophytes reached steady-state masses on bark of 324 and 684 g/m2 within 91 and 150 years, respectively. Humus mass on bark of logs of all three species increased slowly the first decade and rapidly after 20 years; a steady-state humus mass of 4400 g/m2 was predicted after 190 years. Tree density on bark peaked at 140/M2 at 15-25 years and then thinned at a rate of 8%/yr. Bark fragmentation influenced succession by removing plants and reinitiated the sere. Modeling indicates differences in succession patterns among species of logs were caused by differences in bark fragmentation patterns. Although logs are a major seedbed in Picea-Tsuga forests, self-thinning, bark fragmentation and toppling of trees greatly reduced long-term survival on logs.

Perennial grasses were seeded by drilling or broadcasting on 4 mechanical and 3 herbicidal weed control and/or seedbed preparation treatments at 4 semidesert grassland sites invaded by creosotebush (Zarrea tridcnutu) in the Chfuahuan and Sonoran Deserts. The cultivars ‘Cochise’ Atherstone lovegrass (Eragrostis lehmanniana X Eragrostis trichophera) and ‘Catalina’ Boer lovegrass (Effrgrostis curvuIo var. coqferta) lovegrasses were initially established and persisted in 6 of the 8 plantings on disk plowed and disk plowed plus contour furrowed seedbeds. These grasses were established and persisted in 2 of the 5 plantings made in creosotebush stands treated with tebuthiuron [JV-(S-(l,l-dimethylethyl)1,3,4-thiadizol-2-yl)imethylurea] at 0.5, 1.0, and 1.5 kg a.i/ha rates. Grasses established initially on two-way railed and land imprinted areas usually died within 3 or 4 years. Creosotebush (Larrea tridentata), a woody perennial shrub, has invaded the semidesert grasslands within the Chihuahuan and Sonoran Deserts of North America (Humphrey 1958, Buffington and Herbel 1965, Hastings and Turner 1965). As creosotebush densities increase, perennial grass densities decline (Anderson et al. 1957). Therefore, it is desirable to replace creosotebush with perennial grasses to reduce soil erosion, increase infiltration, and provide forage for domestic livestock. Jerry COY. and Howard Morton are range scientist and supervisory plant physiologist, respectively; USDA, Agricultural Research Services Aridland Watershed Management Research Unit, 2000 E. Allen Road, Tucson, Artz. 85719, Martha Martin-R. and Fernando Ibarra-F. are head of the Department of Range Management and Technical Director, respectively, CIPES, Periferico OTS S/N, Conjunto UGRS, Postal 1754, Hermosillo, Sonora, Mexico. When this study was initiated Martha Martin-R. and Fernando Ibarra-F. were graduate students, School of Renewable Natural Resources, University of Arizona, Tucson. Appreciation is extended to Consejo National de Ciencia y Tecnologia (Mexico) for financial support; Elanco Products Company for the herbicide and fencing materials at the Mexican sites; Drs. Luis Carlos Fierro, Thomas N. Johnsen, Jr., and Gilbert L. Jordan for technical assistance; personnel at Rancho Experimental La Campana, Chihuahua, Mexico, and Aridland Watershed Management Research Unit, Tucson, Aria., for setting up plots, applying treatments, and collecting data; and ranchers Eloy Morales, Sergio Mendora, and Gilbert0 Valdez for permission to use their land and housing facilities. The Rocky Mountain Forest and Range Experiment Station gave permission to use land at the Santa Rita Experimental Range. Lovegrass seeds were provided by U.S. Dep. Agr., Soil Conservation Service, Plant Materials Center, Tucson, Arizona. Kleingrass and sideoats grama seeds were provided by Rancho Experimental La Campana. Buffelgrass seeds were provided by Centro de Investigations Pecuarias de1 Estado Sonora, Garbo, Sonora, Mexico. Manuscript accepted 5 May 1986. 540 For the past 90 years creosotebush management has consisted of mechanical tillage to reduce creosotebush competition and prepare a seedbed for seeding perennial grasses (Cox et al. 1982). Mechanical tillage disturbs surface soils and aids in rainwater infiltration (Jordan 1981), but seedings at creosotebush site were seldom successful and the treated area is usually reinvaded by creosotebush or annual forbs and grasses (Cox et al. 1984a). Pelleted tebuthiuron [N-(5-(1,ldimethylethyl)-1,3,4-thiadiazol2-yl)-WWdimethylurea] effectively controls creosotebush (Jacoby et al. 1982) and perennial grasses can be established if grass seeds and pellets are applied at the same time (Baur et al. 1977). Grass seedlings, however, may not survive if pellets are applied after seeds germinate because seedling roots encounter the herbicide as it moves through the upper soil profile (Baur 1979). The semidesert grasslands of the southwestern U.S.A. and northern Mexico are of great importance to the livestock industry, but the chances of reestablishing forage grasses are low because of erratic precipitation in summer. Therefore, it is important to address the effects of precipitation on plant establishment, persistence, and forage production. More than 300 forb, grass, and shrub species have been sown at 400 locations in the southwestern U.S.A. and northern Mexico during the past 90 years (Cox et al. 1982). A successful seeding was more likely to occur if seed of the following species were sown prior to the summer rains: (1) ‘A-68’ Lehmann lovegrass (Eragrostis lehmanniana), (2) ‘A-84’ and (3) ‘Catalina’ Boer lovegrass (E. curvula var. conferta), (4) ‘Cochise’ Atherstone lovegrass (E. lehmanniana X E. trichophera), (5) ‘S-75’ Kleingrass (Panicum coloratum), (6) ‘Premier’sideoats grama (Bouteloua curtipendula), and (7) ‘common’ buffelgrass (Cenchrus ciliaris). Researchers have evaluated either the relationships between mechanical seedbed preparation and grass establishment or chemical seedbed preparations and grass establishment, but have not attempted to directly compare both seedbed preparations. The purpose of this study was to compare establishment potential and persistence of 7 perennial grasses sown in mechanically and chemically prepared seedbeds.

The establishment and growth of six coniferous species, Abies amabilis Dougl. ex Forbes (Pacific silver fir), A. procera Rehd. (noble fir), Pinus monticola ex D. Don (western white pine), P contorta ex Loud. (lodgepole pine), Pseudotsuga menzieszz (Mirb.) Franco (Douglas-fir) and Tsuga heterophylla (Raf.) Sarg. (western hemlock) were related to: (1) depth of tephra deposit, (2) condition of tephra surface crust, and (3) availability of shade on seedbed. In October 1980, seeds were planted on four sites 20 km NE of Mount St. Helens, Washington, in a split-split plot design that incorporated plantings both on tephra deposited 18 May 1980 and on pre-eruption soil. All six species established from seed on tephra deposits less than 20 cm deep. Cultivation of the tephra surface crust yielded more seedlings than either total tephra removal or untreated tephra. Seedlings grown on tephra were generally shorter than those grown on underlying soil, regardless of surface treatment. The principal factors affecting establishment in this study were: (1) loss of seed prior to germination, (2) failure of germinating seeds to penetrate the surface crust of the tephra, and (3) the occurrence of extended drought and/or extreme surface temperatures.

Eight nlfnlfa populations were seeded in a dryland pasture in northern Utah. Densities of mature plants, seeds, seedlings, and l-year-old plants were measured in each of 3 years. The populations did not differ for mature plant stands or seed production. There was a higher rate of seedling survival for populations that primarily originated from Medicago sativu rather than M.falcata. All populations had some one-year-old plants persisting to replace mature plants killed by disease or rodents. Alfalfa (Medicago satin and A4. falcata) is a valued component of pastures in subhumid environments. Its contribution to livestock production in dryland pastures and modified rangelands of semiarid areas is less well documented, although Townsend et al. (1975) regarded alfalfa as one of the most promising forage legumes for dryland seedings in the Great Plains. Hervey (1960) reported that lamb gains increased after alfalfa and crested wheatgrass (Agropyron desertorum) were interseeded into native sod in Wyoming. The introduction of the dryland alfalfa cultivar ‘Nomad’was one of the most successful techniques used to improve antelope (Antilocapra americana) ranges in southeastern Oregon (Yoakum 1979). After 36 separate aerial seedings on more than 26,000 ha, alfalfa constituted 10% of the vegetation present for 6 years or longer. Lee and Rothwell (1966) and Norman (1968) successfully used alfalfa pasture to supplement native pasture for sheep and cattle in Australia. Vallentine et al. (1963) recommended the use of alfalfa in sagebrush zone range sites in Utah where annual precipitation averaged 30 cm or more. The merit of using alfalfa for supplementing native pasture or for interseeding will depend on the longevity of plants and the ability of the species to reseed in a droughty environment while subjected to grazing. Kilcher and Heinrichs (1965), Pearse (1965), and Rumbaugh and Pedersen (1979) presented evidence that alfalfa lived up to 23 years in environments that received 20 to 30 cm average annual precipitation. Gomm (1974) reviewed results from more than 50 seeding experiments on 1 I vegetation types in dryland areas of Montana. Annual precipitation at the study locations ranged from an average of 20 to more than 50 cm. Alfalfa either failed to become established or the stands declined rapidly in more than half of these plantings. The causes of the declining stands were not stated. Author is research geneticist, U.S. Dep. Agr., Agr. Res. Serv., Crops Research Laboratory, Utah State University, UMC 63, Logan, Utah 84322. This study is a contribution from the U.S. Dep. Agr., Agr. Res. Serv., in coopcration with the Utah Agricultural Experimental Station, Logan, Utah. Journal Paper No. 2525. Manuscript received May 2, 1980. 84 Gomm (1964) did find that ‘Ladak’ alfalfa and ‘Madrid’ sweetclover (Melilotus officinalis) established equally well in a dryland experiment where the seedbed was prepared with a moldboard plow. Nichols and Johnson (1969)concluded that biennial sweetclover was well adapted as a legume for rangelands with heavy clay soils in western South Dakota whereannual precipitationaveraged 39 cm. Natural reseeding was successful every 2 years and sufficient hard seed remained in the soil to safeguard against elimination of the species in a season when drought killed the seedlings. They believed that periodic seedset would provide sweetclover stands whenever growing conditions were suitable. Similar data and observations with alfalfa have not been reported. A mature stand of alfalfa in northern Utah was available as a study site to provide such information.

To determine the effect of the transient increase in nutrient availability which follows prescribed burning in the New Jersey Pine Barrens, we monitored growth and foliar nutrient dynamics of white oak (Quercus alba) and chestnut oak (Q. prinus) in neighboring burned and unburned plots. Growth rates of oak trees in the burned plot were significantly higher in 1985 (the postburn year) than in the 4 years prior to the fire. Growth increases in the burned site averaged 55 % for white oak and 38% for chestnut oak. In contrast, relative growth rates of reference site Quercus trees did not differ between preburn and postburn years. Phosphorus resorption and calcium deposition in chestnut oak were greater in the burned site, though growth efficiencies did not differ between chestnut oak trees in the burned and reference sites. Calcium deposition and phosphorus growth efficiency of white oak were greater in the burned site; no differences in white oak N or P resorption were noted. These oaks showed rapid growth responses to the transient increases in nutrient supply produced by prescribed burning. Pinus rigida growth also increased slightly, though the increase was less than those of the oaks. These results contradict earlier assertions of the efficacy of sporadic prescribed burning as a management tool in these oak-pine forests and suggest that sporadic prescribed burning may accelerate, not retard, succession toward oak dominance. INTRODUCTION Since the early 1930s the use of prescribed burning as a forest management tool in the New Jersey Pine Barrens has been justified on the basis of four postulated benefits: (1) improvement of the seedbed for Pinus establishment; (2) preventing the exdusion of Pinus by oaks (Quercus spp.) by slowing or stopping oak growth, and killing oak saplings; (3) reduction of the fuel mass and therefore wildfire probability, and (4) improvement of soil fertility by the release of nutrients bound in the litter and humus (Little and Moore, 1945; Burns, 1952). Though we have demonstrated that prescribed burning on a 3-yr rotation does not mineralize a significantly greater mass of mineral nutrients than occurs through litter decay (Boerner and Lord, 1984), significant transient increases in nutrient availability may occur immediately after a prescribed burn. Current knowledge of the relationship between nutrient availability, nutrient use efficiency, and growth of oaks (Ostman and Weaver, 1982; Boerner, 1984) and the response of stress-tolerating trees to transient increases in nutrient availability (Grime, 1979) suggests that periodic prescribed burning would increase, not decrease, oak growth rate, though possibly at the expense of decreased nutrient use efficiency. If true, the effect of prescribed burning would be to ac'All correspondence should be forwarded to this author.

Perennial grasses are difficult to establish from seed in the Southern Great Plains. The conventional planting practice is to plant grass seeds 1 to 2 cm deep in the soil; but that soil layer often dries quickly, thus preventing plant establishment. I investigated punch planting, which may avoid the problem of soil drying around grass seeds. Punch planting is defined as the placement of seeds in open, small-diameter holes, punched in the soil to a much greater depth than conventional planting. Under drying conditions, punch planting produced satisfactory stands for 5 grasses, but conventional planting produced failures. Where the soil was kept wet, both methods produced satisfactory grass stands. Optimum depth of punch planting was related to seed size and seedling vigor. Small-diameter holes (0.6 cm) produced best plant emergence, because soil at the bottom of these holes dried slower than at the bottom of large holes. Punch planting may offer a solution to the problem of seeding failures. Native grasses, legumes, and other forage plants are often difficult to establish in both pasture and range conditions. Seeding failures are costly because seedbed preparation, seed, and seeding costs are lost, and production is lost from the land for one ormore years. A 3-year study of grass seeding in the Great Plains (Great Plains Council 1966) showed that seeding failures were most common in the Southern Great Plains, and that more than 50% failures occurred even in humid areas. Weather conditions often determined the degree of success or failure, and fallowed seedbeds or planting in crop stubble improved the chances forsuccessful establishment. However, even the best treatments produced numerous failures. Germination and establishment of grasses or legumes require that several factors or conditions be within some adequate range in the seed zone. Soil and air temperatures and soil water content are among the most critical conditions. Temperature can be controlled partially by selecting planting date wisely. However, soil water is often a serious limiting factor in the Southern Plains because the top 2 cm of soil, where grass seeds are planted, dries very quickly. Dowling and Smith (1976) reported that plant establishment for two Australian pasture grasses and two legurhes was linearly related to available soil water during the first 6 weeks after sowing seeds on the soil surface. Army and Hudspeth (1960) found that, in summer on the Texas High Plains, the top 1.3 cm of Pullman silty clay loam soil dried from field capacity to wilting point within I day. Wiegand (1962) showed that during summer the top 2 crn of a sandy clay loam dried from field capacity to wilting point within 2 days in the Lower Rio Grande valley of Texas. Reginato (1975) reported that the top I cm of a loam soils at Phoenix, Arizona, dried from near field capacity to the wilting point within 4 hours in

Reseeding, with and without disc harrowing, building of water bars, and piling of slash on utility corridors (restoration), was studied on access roads and pylon sites following construction of the 500 kV Navajo Project Southern Transmission Line in 1973. Reseeding was not successful. Restoration either had no significant positive effect on revegetation or slowed plant succession in the following Qyear period, or had a deleterious effect on amount and quality of revegetation due to the destruction of climax vegetation which survived powerline construction. Reseeding rangeland has been shown to be both successful and economically feasible by many (e.g. Godfrey 1979, Kearl and Cordingly 1975). Successful seeding, however, has been shown to be dependent upon prevailing weather conditions; weed control (Herbel et al. 1973); seedbed preparation (Struth and Dahl 1974, Hull 1974); and sometimes, pretreatment of seeds to enhance germination (Voigt 1978). In previous papers (Hessing et al. 1981a,b) we described the secondary succession of plants after construction of the 500 kV Navajo Project Southern Transmission Line which connects the Navajo Generating Station at Page, Ariz., with Phoenix. In this paper we describe the effects of reseeding and restoration treatments on the initial course of secondary succession. We used an experimental design which allowed us to describe succession following restoration either separately or together with reseeding. The sequence of powerline construction was that a survey strip was bulldozed in 1972. The powerline was constructed in the spring and early summer of 1973 with part of the survey strip serving as an access road for construction. All restoration and reseeding was done after construction in the summer of 1973. Reseeding occurred at the beginning of the annual summer rainy season, thus providing the seeds with a moist seed-bed.

Desert saltgrass [Distichlis spicata var. strictu (Torr.) Beetle] is an important forage species of the saline-alkali basins of the western United States. Revegetation of disturbed sites using saltgrass currently involves the use of rhizomes, but seeding saltgrass with conventional equipment would be much more efftcient. The seed and seedbed ecology of desert saltgrass is important to land managers who wish to try new revegetation techniques. The germination of nine collections of saltgrass seed was determined at a wide range of constant and alternating temperatures. The effects of decreasing osmotic potentials on seed germination of one collection was determined using polyethylene glycol and sodium chloride solutions. Seedbed temperatures and moisture potentials were determined during the growing season in two saltgrassstands using thermocouple temperature probes and psychrometers. The temperature regime that produced the highest mean germination (58%) for all nine collections was 10°C for 16 hours alternating with 40°C for 8 hours (10/4oOC). Germination response varied significantly (eO.01) between collections. The best germination was 96% with one collection at the lO/SoOC regime, but most collections germinated best with the lo/400 C regime. For all collections, at least a 20°C diurnal fluctuation in temperature was needed for germination above 10%. Seeds did not germinate at temperatures as cold as -5O C or as hot as 60” C. Saltgrass germination was enhanced at osmotic potentials of -1 bar, but inhibited by potentials lower than -1 bar. No significant (eO.01) germination occurred at -15 bars. Field seedbed temperatures reached optimum levels for germination after moisture potentials were below that required for germination. This suggests that saltgrass seed germination is an episodic event in nature, occurring only when moisture events coincide with optimum seedbed temperatures and can leach sufficient salts to raise moisture potentials above -15 bars. Desert saltgrass [Distichlis spicurn var. stricta (Torr.) Beetle] is an important forage species that can grow vigorously on wet, saline soils where most others will not survive (Nielson 1956). In many of the salt marsh areas of the interior United States, saltgrass provides the sole forage for cattle during the summer portion of the grazing season. Saltgrass is relatively high in protein (Hansen et al. 1976) and highly resistant to excessive grazing. Desert saltgrass is a potential species for revegetating mine spoils and roadsides in the semiarid west (Pavlicek et al. 1977). Large, isolated areas of saltgrass occur in many places throughout the western United States, but seed is produced in very few of these areas. This may be because saltgrass is dioecious and mainly reproduces vegetatively through spreading rhizomes. Saltgrass produces seed only where the stands are most dense and vigorous. Consequently, revegetation using saltgrass has entailed the use of rhizomes (Pavlicek et al. 1977). However, seed sources do exist and The authors are C.J. Cluff, range agronomist, University of Nevada, Rena: R.A. Evans and J.A. Young, range scientists, USDA/AR& Renewable Resource Center, Rena, Nev. 895 12. This study is a contribution from USDA, Agricultural Research Service, and the Agriculture Experiment Station, University of Nevada, Rena. Journal Series No. 535. Manuscript received September 22, 1981. JOURNAL OF RANGE MANAGEMENT 36(4). July 1963 since revegetation using rhizomes is expensive and labor intensive, seeding desert saltgrass with readily available equipment would be much more efficient than planting rhizomes. In order for land managers to use saltgrass optimumly for revegetation of rangelands or disturbed sites, it is necessary to understand the seed and seedbed ecology of this species. Important to the ecology of this species are its seed germination characteristics. Neilson (1956) reported that scarification of saltgrass seeds with sandpaper enhanced germination, but under natural conditions germination of saltgrass seeds is very poor. Nielson’s work and our own preliminary investigations on saltgrass seed germination have shown that simple afterripening, cold stratification, and treatment with sulfuric acid, sodium hydroxide, potassium nitrate, sodium chloride, red light, hot water, or hydrogen peroxide does not greatly increase saltgrass seed germination. The purpose of this study was to determine the moisture and temperature conditions under which saltgrass seed would germinate and the variability in germination characteristics of different collections of saltgrass seed and to relate these data to field measurements of soil moisture potentials and temperature.

Winterfat [Eurorio lanatal (Pursh) Moq.; Ceratoides hata (Pursh) J.T. Howell] is a low, Chenopod shrub of western North America. Its diaspore is 2 united, subtending bracts enclosing a pubescentcovered utricle (Booth 1988). White haii, 2 to 8 mm long, cover the bracts. The seed has a thin testa and a welldeveloped embryo. The diaspore disarticulate9 below the bracts, and bracts and utricle function as a unit in dispersal (Hilton 1941) and in seedling establishment (Booth 1982, Booth and Schuman 1983). Seedlings from diaspores establish and survive better than those from threshed seed. This is partly due to the anchoring function of bract hairs (Strickler 1956, Booth and Schuman 1983); however, diaspore seedlings also have greater hypocotyl elongation than that of seedlings from threshed seed (Booth and Schuman 1983). The transfer of growth substances from bracts into embryos, during imbibition, was identified as a possible reason for this growth difference. Booth (1985) presented evidence that transferred substances are, at least partially, cationic. Therefore it was postulated that cations in diaspore bracts move into the embryo during imbibition and enhance germination and growth. Three questions were posed as a test of this postulation. First, is there a concentration gradient to indicate potential cation movement from bracts to seed? Second, are there significant increases of seed cations after diaspore imbibition? Third, is germination or seedling elongation improved if cations move into seeds during imbibition?

Highlight: Seeding success was evaluated on 62 ranches in Texas to compare relative success and costs of various treatments as affected by range site. Effects of precipitation and temperature were studied. Seeding during rootplow-rollerchop operations gave consistently better stands at a lower cost on all but the very shallow sites where seeding during treedozing treatments proved more economical. Relationships between site and factors affecting success differed distinctly between the wetter and drier portions of the study area, In the drier area, as soil depth decreased the amount of rainfall received close to the planting date aided seedling establishment more than did seedbed preparation. Cool temperatures favored seeding success on very shallow sites, but they were detrimental to seeding success on loamy bottomland sites. In the wetter area, degree of seedbed preparation was more important on all sites as long as sufficient rains for germination occurred within 90 days after planting. Mechanical brush control techniques that destroy most of the existing grass proved a hazardous undertaking, as half of the follow-up seedings were considered poor or total failures. This study separates those brush control practices and seeding techniques most likely to result in successful grassland restoration on west Texas brush-infested ranges from those less likely to provide successful seeded stands.