Western Larch Research Articles

Population Density and Mating Pattern in Western Larch

Variation in the mating systems of western larch as affected by different stand density was investigated in two adjacent populations (natural and seed tree) in two locations in the interior of British Columbia. Population multilocus outcrossing rates, individual tree multilocus outcrossing rates, and the correlation of outcrossed paternity were estimated from analysis of allozyme variation in embryonic and megagametophytic tissue of wind-pollinated seeds. All population outcrossing rate estimates were significantly different from t = 1. Positive association between population density and outcrossing rate was detected for one location (0.903 versus 0.876) and inverse association was obtained for the second (0.793 versus 0.912). In three populations, the distributions of individual tree outcrossing rates were skewed toward high outcrossing. In the fourth population, which produced a low multilocus estimate of outcrossing, individual tree outcrossing rates were widely distributed. High and significant correlated matings (6% and 10%) were detected in the populations with high densities, while low (0.1% and 2.0%) estimates were detected in populations with low density. It appears that the effects of population density observed in this study and reported in previous studies can be overridden by the presence of barriers that limit pollen movement.

Roost-site selection and roosting ecology of forest-dwelling bats in southern British Columbia

We used radiotelemetry to examine the roost-site preferences of four species of tree-roosting bats (Eptesicus fuscus, Lasionycteris noctivagans, Myotis evotis, and M. volans) in southern British Columbia, Canada, by radio-tracking bats to their day roosts. We found a total of 21 roost trees: 14 roosts were beneath loose bark, 5 were in cavities excavated by woodpeckers, and 2 were in natural cavities. Entrance height increased with tree height, but roost entrances tended to be situated below the level of the canopy. Of the 22 tree and site variables examined, only 3 significantly discriminated between roost trees and available trees: tree height, distance to the nearest available tree, and percent canopy closure. Bats preferred tall trees associated with low percent canopy closure and a short distance to the nearest available tree. Bats roosted in western white pine, and to a lesser extent ponderosa pine and western larch, in intermediate stages of decay more often than would be expected at random. Bats switched roosts frequently. The distance between subsequent roost trees was short, suggesting a degree of fidelity to a particular group of trees or area of forest. The number of days of rain during the roosting period significantly influenced the number of days spent in a particular roost, and thus ambient conditions may restrict the frequency with which bats can switch roosts.

Phenology-mediated effects of climatic change on some simulated British Columbia forests

We added certain aspects of species-specific phenology, and of local frost regimes to a standard invididual-based patch model of forest stand dynamics, which we used to explore the possible consequences of four climate-change scenarios in eight distinct forest regions in British Columbia, Canada. According to model projections, lowland temperate coastal forests will be severely stressed because forest tree species will no longer have their winter-chilling requirements met. High-elevation coastal forests may either remain stable or decrease in productivity, while interior subalpine forests may eventually resemble those now found in the coastal mountains. Southern interior forests are likely to persist relatively unchanged, while boreal and sub-boreal forests of the northern interior may become dominated by Douglas-fir and western larch, rather than by spruce and pine as at present. The rate of change in forest composition may be very high in some cases. Changes under the four climate-change scenarios generally vary in magnitude but not in direction. This exercise illustrates that different forest types might respond to a changing climate for different reasons, and at different rates.

Effects of air temperature, photoperiod and leaf age on foliar senescence of western larch (Larix occidentalis Nutt.) in environmentally controlled chambers

ABSTRACTWe induced foliar senescence in western larch (Larix occidentalis Nutt.) needles (100 to 400 d old) in chambers set to combinations of photoperiod (8 or 16 h) and air temperature (8 or 15°C). We used regression analysis to estimate the effects of air temperature, photoperiod, provenance and leaf age on the date of decline in chlorophyll, photosynthesis, and chlorophyll a/b ratio. Increased air temperature delayed the decline in chlorophyll and photosynthesis without affecting chlorophyll a/b: seedlings with 200‐d‐old needles placed under 8h days and 8°C lost chlorophyll, photosynthesis and chlorophyll a/b in 22, 37 and 63d, respectively, while those senescing under 15°C lost them in 54, 61 and 63d. Extended photoperiod delayed the decline in chlorophyll but not photosynthesis or chlorophyll a/b ratio: the 200‐d‐old needles placed in 8°C and 16 h photoperiod lost chlorophyll, photosynthesis, and chlorophyll a/b in 34, 37 and 63 d, compared with 22, 37 and 63 d for seedlings in 8 h days. Our analysis shows that it is possible to quantify the extent to which the timing and process of senescence vary with environmental conditions.

Water Relations Parameters and Tissue Development in Somatic and Zygotic Embryos of Three Pinaceous Conifers

There is increasing interest in using somatic embryogenesis to meet the demand for high quality seedlings. However, in vitro production of propagules on a large scale depends on the optimization of the maturation and germination steps promoted by desiccation and subsequent imbibition of the embryo, respectively. It is therefore important to characterize zygotic and somatic embryos in terms of their water relations. Bound water, elastic modulus, osmotic potential at full turgor, and relative water content at turgor loss point were determined for somatic and zygotic embryos of western larch and loblolly pine and somatic embryos of white spruce at two developmental stages. These water relations parameters were derived from water-release curves obtained by suspending tissue samples in sealed vials over unsaturated NaCl solutions of known water potential. There was little difference in water relations parameters among species but marked stage dependency for bound water and elastic modulus. The amount of bound water was lowest in western larch somatic embryos (0.02-0.07) and highest in zygotic loblolly pine embryos (0.10-0.18). Elastic modulus ranged from 2.5 to 6.2 MPa in somatic embryos but varied between 1.4 and 1.8 MPa in zygotic embryos. The osmotic potential was lower in somatic embryos than in their zygotic counterparts. Our results show that water relations parameters are remarkably conservative across species but that, within a given species, these parameters are stage specific. It would seem, therefore, that desiccation protocols might be developed for a given developmental stage and applied across a range of species without the confounding effects of differences in water relations parameters.

Growth and form of western larch stecklings: plagiotropism and reiteration

Western larch (Larixoccidentalis Nutt.) in the interior northwestern United States produces small and infrequent cone crops resulting in recurrent seed shortages throughout much of its range. Vegetatively propagated planting stock could potentially alleviate shortages of seedlings for artificial regeneration. In a greenhouse study to evaluate suitability of rooted cuttings for forestry, morphology and growth of container-grown stecklings from 1- and 3-year-old ortets were compared with seedlings for up to 6 years after rooting. Newly rooted stecklings produced an average 50% orthotropic, 32% plagiotropic, and 18% suppressed leaders. One-year-old steckling leaders elongated 46% as long as 1-year-old orthotropic steckling leaders after fertilization with 20:20:20 N–P–K at 120 ppm N (p = 0.0001). In subsequent years, orthotropic stecklings elongated more than seedlings. Plagiotropic leaders (average deflection of 24°) developed upright form within 2 years. Competing axillary shoots delayed development of dominant leaders for up to 3 years. Vestiges of atypical habit included small basal stem crooks and sparse branching. Although staking and pruning promoted excurrent habit, poor quality of container-grown stecklings can limit indoor nursery production. Effects of ortet and environment on quality should be examined before stecklings are field tested for use in reforestation.

Correlated Population Differences in Dry Matter Accumulation, Allocation, and Water-Use Efficiency in Three Sympatric Conifer Species

Abstract Populations of three sympatric conifer species, Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco), ponderosa pine (Pinus ponderosa Laws.), and western larch (Larix occidentalis Nutt.), were studied for growth, water-use efficiency, and dry matter allocation. Seedlings from seed collected from across the respective natural distributions were grown under two watering regimes. In addition, trees at age 12 for western larch and 20 for ponderosa pine were sampled from experimental plantings. Seedling growth was measured in terms of total dry matter, aboveground dry matter, height, diameter, and relative growth rate; tree growth in the field was measured in terms of height. Dry matter allocation was measured in terms of leaf weight ratio and root weight ratio. Water-use efficiency was measured in terms of biomass production per unit water loss and stable carbon isotope discrimination. Douglas-fir populations differed in all measured variables under both watering regimes (all P ≤ 0.04); correlations between measurements under well-watered and water-stressed conditions were high (0.69 ≤ r ≤ 0.99). Ponderosa pine populations differed consistently in leaf weight ratio and root weight ratio (all P ≤ 0.02), less consistently in growth (0.00 < P ≤ 0.35); and only leaf weight ratio and height were significantly correlated between watering regimes (0.82 ≤ r ≤ 0.85). Western larch populations differed inconsistently in dry matter allocation (0.01 ≤ P ≤ 0.15) and growth (0.00 < P ≤ 0.82); however, population differences in total dry matter, aboveground dry matter, relative growth rate, and leaf weight ratio were significantly correlated between watering regimes (0.56 ≤ r ≤ 0.75). Generally speaking, total dry matter was correlated with water-use efficiency (WUE) but not allocation in western larch, with allocation but not WUE in ponderosa pine, and with both allocation and WUE in Douglas-fir. Similarly, tree height was significantly correlated with carbon isotope discrimination (Δ) in Douglas-fir and in 12-yr-old trees of western larch, but not ponderosa pine. These results suggest that water-use efficiency correlated with growth much more consistently than dry matter allocation. The simplicity of measuring Δ and its stability in this and other studies lead us to suggest that carbon isotope discrimination may be used as a marker for selection and breeding programs to improve growth for Douglas-fir and western larch For. Sci. 42(2):242-249.

Larch arabinogalactan for hepatic drug delivery: isolation and characterization of a 9 kDa arabinogalactan fragment

Purified arabinogalactan [AG(37 kDa)] from Larix occidentalis is composed of repeating units of similar molecular weight and composition. A 9 kDa arabinogalactan [AG(9 kDa)] has been obtained in high yield from AG(37 kDa) either by autoclaving at 121°C or by exposure to alkaline solution in the presence of sodium borohydride. The weight average molecular weight of AG(37 kDa) was determined to be 37 and 38 kDa by intensity light scattering and sedimentation equilibrium, respectively. The weight average molecular weight of AG(9 kDa) was determined to be 9.1 and 9.5 kDa by intensity light scattering and sedimentation equilibrium, respectively. MALDI-TOF mass spectrometry yielded a molecular weight at the peak of the distribution of 8.3 kDa for AG(9 kDa). Both AG(37 kDa) and AG(9 kDa) exhibited narrow molecular-weight distributions ( M w / M n ∼ 1.2). AG(37 kDa) and AG(9 kDa) exhibit nearly identical 13C-NMR spectra, monosaccharide composition, and sugar linkages. It is proposed that AG(37 kDa) is composed of covalently bound subunits of AG(9 kDa), AG(37 kDa) and AG(9 kDa) bind isolated hepatocyte asialoglycoprotein receptor equally well. As a result AG(9 kDa) is a candidate for use in hepatocyte directed drug delivery and may be more desirable for such use than is AG(37 kDa).

Genetic variation, climate models and the ecological genetics of Larix occidentalis

Provenance tests of 143 populations of Larix occidentalis revealed genetic differentiation for eight variables describing growth, phenology, tolerance to spring frosts, effects of Meria laricis needle cast, and survival. Geographic variables accounted for as much as 34% of the variance among Rocky Mountain populations. Patterns of genetic variation were dominated by the effects of latitude and elevation, with populations from the north and from high elevations having the lowest growth potential, the least tolerance to the needle cast, and the lowest survival. However, the slope of the geographic clines was relatively flat. Populations in the same geographic area, for instance, need to be separated by about 500 m in elevation before genetic differentiation can be expected.Regression models using geographic predictors were developed to describe variation in ten climatic variables from 192 weather stations that best represented the Rocky Mountain distribution of L. occidentalis. Values of R2 ranged from 0.42 to 0.92 and were higher for temperature than for precipitation variables.Using climatic effects predicted for each provenance to describe genetic variation produced values of R2 between 0.15 and 0.27 which accounted for nearly as much (68–100%) of the genetic variance as had geographic variables. The analyses suggested that genetic differentiation was controlled primarily by the relative mildness of the climate. Secondary effects of precipitation were implicated for variables measuring the impact of Meria needle cast and survival.

Pruning Costs for Four Northern Rocky Mountain Species with Three Equipment Combinations

Abstract A time and motion study was conducted to determine the cost to prune ponderosa pine (Pinus ponderosa), interior Douglas-fir (Pseudotsuga menziesii var. glauca), western larch (Larix occidentalis), and lodgepole pine (Pinus contorta) with loppers, pole saws, and Power Pruners. Costs to prune up to 8 ft ranged from $0.61 to $2.35/tree, and from $2.34 to $6.42/tree to prune to 18 ft depending upon species, equipment, and wage assumptions. Pole saws were the recommended equipment based on cost, ease of use, and damage to trees. Multivariate models were unable to explain much variation in pruning time because of the confounding effects of so many variables. Results suggest more than three trees could be pruned to a height of 9 ft for the same cost as pruning one tree to 18 ft. Pruning more trees to a 9 ft height would therefore increase clearwood production overpruning fewer trees to 18 ft, but may necessitate some modification of current log grading standards. West. J. Appl. For. 10(2):59-65.

Mortality of Western Larch Seedlings in Relation to Seedbed Characteristics at the Dry end of Its Ecological Range

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.

Early height development and species stratification across five climax series in the eastern Washington Cascade range

Reconstruction in twenty single-cohort stands across five climax series on the eastern slope of the Washington Cascade Range found a variety of species combinations and development patterns. Western larch (Larix occidentalis Nutt.) and lodgepole pine (Pinus contorta Dougl. ex Loud) were found to be very competitive species that usually occupied a dominant position in stands in the Abies grandis, Abies lasiocarpa, and Tsuga mertensiana climax series. Interior Douglas-fir (Pseudotsuga menziesii var. glauca (Mirb.) Franco) was found in all five climax series and, although its height growth was less than that of western larch or the lodgepole pine, it was usually found in the upper stratum. These results suggest that site classification based on climax potential should be used cautiously when applied to young stand management decisions regarding seral species. For example, the difference between an Abies grandis, and a Tsuga mertensiana climax series is quite large in terms of potential productivity but in either case western larch, if present, will likely dominate these stands.

Black Bear Damage to Lodgepole Pine in Central Oregon

Black bear (Ursus amerlcanus) damage to 108 lodgepole pine (Pinus contorta) trees was found in a mixed conifer habitat in central Oregon. No trees of three other conifer species were injured. Eighty-nine percent of the damage occurred in the same year. Nearly 20% of the freshly damaged trees had bark removed from more than 75% of the circumference and, judging from the fate of trees damaged in prior years, probably succumbed. Black bears (Ursus americanus) feed on the sapwood of a number of species of coniferous trees and, in some habitats, have shown a def- inite preference for certain species. In western Washington and Oregon, Douglas-fir (Pseudo- tsuga menziesii) is reported to be selected more frequently than other species (Levin 1954, Childs and Worthington 1955, Hartwell 1973). In northwest California, extensive damage has been observed on redwood (Sequoia sempervi- rens) (Glover 1955). Additional reports indicate a preference for white spruce (Picea glauca) on the Kenai Peninsula in Alaska (Lutz 1951), western white pine (Pinus monticola) in interior British Columbia (Molnar and McMinn 1960), balsam fir (Abies balsamea) in Maine (Zeedyk 1957), Engelmann spruce (Picea engelmannii) in Yellowstone Park (Contor 1957), and subalpine fir (A. lasiocarpa) and whitebark pine (Pinus al- bicaulis) in Montana (Tisch 1961). Elsewhere in Montana U. americanus selected for western larch (Larix occidentalis), lodgepole pine (Pinus contorta) and P engelmannii (Mason and Adams 1989). Damaged trees located in the course of other stud- ies served as centers for intensive searches for ad- ditional trees damaged by bears. A search was con- ducted from each damaged tree, or patch of trees, in each of the cardinal directions up to 500 m. Each newly identified damage site served as a center for (~~~k~l and cowan 1971, M~~~~ and ~d~~~ further searches in the same fashion. Species, diam- eter at breast height (d.b.h.), and maximum height of 19891, and in eastern Washington (Poelker and stripped bark from ground line were recorded for Hartwe'' 1973). we describe evidence each damaged tree. To classify degree of injury, the exclusive feeding on F! contorta by U. americanus a,erage extent of bark removal around the circum- in a mixed conifer habitat in central Oregon. ference of the main stem was estimated and assigned

Confirmed Sandhill Crane Nesting in Yakima County, Washington

The sandhill crane (Grus canadensis) is a Washington State endangered species, and a U.S. Fish and Wildlife Service and Yakama Indian Nation sensitive species (Yakama Indian Reservation Forest Management Plan 1993-2002). In Washington, the only recent (since 1979) confirmed nesting by sandhill cranes has occurred at Conboy Lake National Wildlife Refuge (NWR), Klickitat Co. (T6N R12E). The refuge is located within the exterior boundary of the Yakama Indian Reservation (YIR), in an area that is open to the public. However, I have observed either pairs or single sandhill cranes each year since 1991 at a wet meadow in the forested portion of the YIR in Yakima Co. that is closed to the public. This meadow is 35 km northeast from the nests at Conboy Lake. The meadow (T9N R13E) covers approximately 79 ha. Vegetation consists of willows (Salix spp.), sedges (Carex spp.), tufted hairgrass (Deschampsia cespitosa) and timber oatgrass (Danthonia intermedia) located in stringers between stands of lodgepole pine (Pinus contorta) cover type or mixed conifer cover type (predominantly Douglas-fir [Pseudotsuga menziesii] or grand fir [Abies grandis] with some ponderosa pine [Pinus ponderosa] and western larch [Larix occidentalis]). Portions of the meadow have standing water. This meadow is probably the same area that Jewett et al. (1953. Birds of Washington State. Seattle: Univ Washington Pr) listed for a 1941 nest: 2 adults and a nest with 2 eggs were in a swamp near Signal Peak, at 1372 m. This nest was on a small island covered with low shrubs. To my knowledge, this was the last confirmed nesting record for sandhill cranes in the forested area of the YIR. Each spring and summer since 1991 I have scanned this meadow for sandhill cranes. Before 1994, the earliest date I observed a pair was 5 April 1993, the latest, 23 June 1993. On 17 June 1994, I found a pair of sandhill cranes with 1 young at this meadow. I returned daily from 20 to 24 June, but saw no cranes. On 5 July, I flew over the meadow in a helicopter and observed 2 adults but no young nor nest. During the flight I surveyed other suitable meadow habitat, but saw no cranes. The latest I saw 2 adults (but no young) at the original meadow was 20 July. From 24 July to 15 August, this portion of the YIR was closed for fire suppression; field work was not possible. I did not attempt to locate birds after 15 August. Littlefield (1994. Draft Pacific Flyway management plan for the Central Valley population of greater sandhill cranes. Princeton OR: USDI Fish and Wildlife Service) reported a 6% mean recruitment of sandhill cranes from 1970 to 1985 at Malheur NWR. Poor recruitment was attributed to predation by coyotes (Canis Intrans), starvation of young because food may be limited by low water levels, and livestock grazing. The summer of 1994 was exceptionally dry on the YIR, although the meadow in which I observed the cranes had standing water on 20 July. Coyotes are also numerous here. This meadow is located within a grazing unit, but cattle generally reach it after 15 July. The major land-use practice nearby is timber harvest, but there is a 20 m no-entry buffer around this meadow. There is logging traffic nearby, however. During May through July 1994 there were approximately 4 log truck trips per day past the site. Since 1984, young sandhill cranes have survived to the flight stage at Conboy Lake NWR every year except 1994 (H. Cole, pers. comm.). I suspect that during 1994 the young sandhill crane that I observed perished. Tribal biologists will continue to monitor this meadow and other suitable habitat for sandhill crane occurrence.

Variation in Pathogenicity and Virulence of Isolates ofArmillaria ostoyaeon Eight Tree Species

Thirteen isolates representing 10 genotypes of Armillaria ostoyae, obtained in northern New Mexico from Pinus ponderosa, Abies concolor, Pseudotsuga menziesii, Pinus strobiformis, Picea pungens, and Populus tremuloides were used to inoculate seedlings of these hosts and Larix occidentalis and Pinus contorta var. latifolia. At 18 months there were no significant differences (P > 0.05) in mortality among the eight hosts, or in virulence across all isolates except for one isolated from P. pungens, which failed to infect any trees. After three growing seasons (30 months), significantly more (P < 0.05) P. contorta var. latifolia were infected than either A. concolor or P. menziesii. Pinus ponderosa, the dominant species in this region, did not differ significantly from either of the exotic species (L. occidentalis and P. contorta var. latifolia) in susceptibility to infection or mortality. Populus tremuloides was significantly (P < 0.05) more tolerant than conifers, being frequently infected but rarely killed. A fungal isolate's ability to incite disease was highly correlated with its production of rhizomorphs (r = 0.94, P < 0.01). Across all fungal isolates and hosts save P. tremuloides, the order of the isolate's ability to incite disease matched its order in killing hosts.

Construction and Installation of Acrylic Minirhizotron Tubes in Forest Ecosystems

AbstractGlass tubing has been the traditional material used when constructing minirhizotrons for studying fine root dynamics in managed and natural terrestrial ecosystems. However, we have found that rocky soils, swelling smectite clays, large structural roots, and freezing soils frequently have broken glass minirhizotrons. We have developed a system to construct and install durable acrylic minirhizotrons. Acrylic tubing costs 42% less than glass and requires only 13% of the preparation time, resulting in a 121% savings vs. glass. The major time‐saving device is a unique spring‐loaded etching trough that places accurate, evenly spaced circles along the length of the tube in minutes. The design can be easily modified for many applications. Preliminary results in a mixed western larch (Larix occidentalis Nutt.)‐lodgepole pine (Pinus contorta var. latifolia Engelm.) forest in western Montana indicate that the acrylic minirhizotrons are durable, the etching is visible, and the system can be used to examine fine root phenology.

Interactive effects of light and stratification on the germination of some British Columbia conifers

Pregermination stratification treatment was generally more important than the effects of light on seed germination by 14 conifer species and varieties native to British Columbia. Nevertheless, there were some strong species differences in the response of germination to light. Final germination percentage after 21 days (28 days for Abies spp.) for both stratified and unstratified seeds of Picea glauca, Picea sitchensis, and Tsuga heterophylla showed no response to light during germination. Seed germination by Abies grandis, Pinus contorta var. contorta, Pinus contorta var. latifolia, Pinus ponderosa, Pseudotsuga menziesii var. glauca, and Pseudotsuga menziesii var. menziesii responded positively to light if unstratified but was not significantly affected by light when stratified. For Thuja plicata seeds, germination responded positively to light regardless of stratification pretreatment. Light appeared to reduce germination of stratified seeds of Abies amabilis, Abies lasiocarpa, Larix occidentalis, and Pinus monticola, although stratification conditions for these species were suboptimal. The germination rate of stratified seeds of all species and unstratified seeds of most species was increased by light. Results showed no significant relationship between germination response to light and shade-tolerance ranking or mean seed weight of the species. In six seed lots of Pinus contorta var. latifolia, however, we detected a weak negative correlation between mean seed weight and unstratified light responsivity measured after 1 week but a significant positive correlation when measured after 3 weeks. Very low light levels in closed-canopy forests or in the forest floor may prolong tree seed germination but are unlikely to constrain final germination levels after most seeds have been naturally stratified by moist, cool winter conditions. The importance of differences in the rate and timing of tree seed germination under natural conditions remains to be demonstrated. Key words: conifer biology, forest regeneration, light response, lodgepole pine, Pinus contorta, seed germination, stratification.

Arabinogalactan for hepatic drug delivery.

Arabinogalactan, a polysaccharide from the tree Larix occidentalis, has been purified and its biological and physical properties described. Intravenous injection of radiolabeled arabinogalactan (4 mg/kg) in rats resulted in 52.5% of the dose being present in the liver, while prior injection of asialofetuin (100 mg/kg) reduced hepatic radioactivity to 3.54%. Gel chromatography indicates arabinogalactan is a single species of 19 kDa, while light scattering gave a molecular weight of 40 kDa. Glycosyl linkage analysis of arabinogalactan is consistent with a highly branched structure comprising a backbone of 1,3-linked galactopyranose connected by 1,3-glycosidic linkages, comprised of 3,4,6-,3,6-, and 3,4- as well as 3-linked residues. In the carbon-13 NMR spectra, the major resonances of arabinogalactan are assigned to beta-galactopyranose, beta-arabinofuranose, and beta-arabinopyranose. Arabinogalactan produced no adverse reactions in single intravenous dose (mouse, 5000 mg/kg) and repeat dose toxicity studies (rats, 500 mg/kg/day, 90 days). When tritiated arabinogalactan was injected, radioactivity cleared from the liver with a half-life of 3.42 days. Arabinogalactan has properties that make it suitable as a carrier for delivering diagnostic or therapeutic agents to hepatocytes via the asialoglycoprotein receptor.

Germination and early growth of western larch (Larixoccidentalis), alpine larch (Larixlyallii), and their reciprocal hybrids

Reciprocal cross pollinations between western larch (Larixoccidentalis Nutt.) and alpine larch (L. lyallii Parl.) were done in Spring, 1991. The cross to alpine larch females was highly successful; 63% of the seeds developed mature embryos and 79% germinated. However, the cross to western larch females resulted in only 4% filled seed of which 68% germinated. Open-pollinated western larch and alpine larch averaged 26 and 32% filled seed with 48 and 44% germination, respectively. Less than 1% of the alpine larch hypocotyls were reddish in color; most of them were green. About 15% of the western larch and about 17% of the hybrids from alpine larch females had reddish hypocotyls, whereas hybrids from western larch females were intermediate between western larch and alpine larch. Hybrid seed began germinating before the parental types and initial height growth exceeded that of the parental types. However, 4 months following germination, western larch seedlings were ca. four times taller than the hybrids and 10 times taller than alpine larch. Stems of hybrids were significantly thicker than those of either western larch or alpine larch. Hybrid seedlings are robust, stocky, and may be useful in revegetating cold, moist sites between the elevational ranges of alpine and western larch.

Stable carbon isotope discrimination, photosynthetic gas exchange, and growth differences among western larch families

Photosynthetic gas exchange, stable carbon isotope discrimination (Delta), height and diameter were compared among five open-pollinated families of 12-year-old western larch trees growing in a common garden in Moscow, Idaho, USA. Statistically significant variation was detected among the families in the two growth traits, Delta and stomatal conductance to water vapor (g) (P </= 0.013), but differences among families in photosynthetic rate (A) and water-use efficiency (W) were not significant (P >/= 0.203). Water-use efficiency was strongly correlated with Delta (r = -0.95, P < 0.01). Neither growth trait was correlated with A (r </= 0.05, P > 0.93) and height was not significantly correlated with Delta (r = -0.75, P = 0.15). Tree diameter and Delta were significantly correlated (r = -0.92, P = 0.03). These results were strongly influenced by a single family. Both the variation in Delta and correlation trends between Delta and the growth traits height and diameter suggest the possibility of selecting for high water-use efficiency with the potential for simultaneous gains in height and diameter growth.