Outdoor Nursery Research Articles

Early growth rate and nitrogen fixation potential in forty-four legume species grown in an acid and a neutral soil from central Chile

Forty legume species, of which most were tree species of potential multipurpose value, were grown for 120 days in individual containers in an outdoor nursery, in a slightly acidic soil (pH 6.0) taken from a subhumid field site where test plantings were planned. Twenty-four species were also grown in a neutral soil (pH 7.2), taken from an arid zone field site. Dry weight of shoots, roots and nodules, as well as N 2 content (DW) and nodule types were compared for all species and four provenances of the locally dominant Acacia caven. A nitrogen fixation and uptake (NFU) ratio was calculated as N 2/nodules (DW). In both soil types, members of sub-family Mimosoideae nodulated more and grew faster than the Caesalpinioideae or Papilionoideae tested. Within the Mimosoideae, Acacia species, especially of sub-genus Acacia (= series Gummiferae Benth.), grew faster and accumulated more nitrogen than several Prosopis species or any other genus. In acidic soil, the local provenance of Acacia caven performed as well or better than three introduced provenances. Weedy species nodulated more consistently than non-weedy ones. Within the range tested, soil pH did not appear to affect relative performance of species and provenances tested. NFU ratios did, however, vary in the different soils. On the basis of these nursery tests, several weedy candidate species were excluded from field trials, in favor of similarly performing candidates with less potential of becoming invasive weeds.

Germination of stratified and non-stratified seeds of red alder at two germination temperatures

Two- to four-week stratification of red alder seeds slightly increased the speed of germination but did not improve total germination under alternating warm temperatures (30°C/20°C), yet significantly improved speed and total germination under cool temperatures (15°C/5°C) that simulated early spring outdoor nursery bed conditions. Only seeds that received four-week stratification achieved complete germination at the cooler temperatures. Strong seed source variation in response to seed treatments was observed at the cool regime. The Yacolt source germinated well regardless of seed treatments, even without stratification, while five other sources needed two to four weeks of stratification to achieve above 50% germination. Possible reasons for this variation are discussed.

RESEARCH TO PRODUCTION: LABORATORY SCALE-UP WITH MICROPROPAGATED ACER SACCHARINUM L.

During the research phase, a system was developed to clonally micropropagate silver maple. Explant performance was best on DKW medium with 10 nM thidiazuron, and explants commonly developed 1 7 shoots after three months and over 60 shoots that could be rooted after four months in vitro. Plants were rooted (>90%) and acclimatized under intermittent mist and transplanted to an outdoor nursery bed. However, results were different during the production phase when 90 clones were propagated. Shoot proliferation rates were lower, differences in clonal response and worker efficiency were apparent, mass rooting under mist was inconsistent and acclimatization problems arose. The mean rooting was 46% under mist because of uneven coverage. Only 56% of rooted plantlets acclimatized which resulted in an overall efficiency of 26%. Partial solutions included root initiation in vitro, and use of fog for acclimatization.

Nursery Rooting of Cuttings from Seedlings of Slash and Loblolly Pine

Abstract Methods used to root slash (Pinus elliottii var. elliottii Englem.) and loblolly (Pinus taeda L.) pine cuttings from 1-0 seedlings in outdoor nursery beds are described. The species, the date of setting (February or March) and the type of shoot collected (succulent, top-pruned or bud-set)influenced rooting success. A February rather than March setting date is recommended. The succulent shoot type rooted best for slash pine while nonsucculent shoot types rooted best for loblolly pine. When considering all types of shoots set in February, slash and loblolly pine cuttings rootedat 77 and 69%, respectively. After lifting, approximately 70% of the cuttings that rooted (or 52% of all cuttings set in February) were judged acceptable for planting. Current costs of producing rooted cuttings exceed that of barefoot seedlings. However, as technology is developed to rootcuttings on a larger scale in the nursery, the superior genetic quality of plantations derived from rooted cuttings may offset their extra cost, relative to seedlings, enough to economically justify their operational use. If so, these procedures will offer forest managers an additional andmore effective option than seedling propagation for exploiting genetic variation in order to enhance forest productivity. South. Appl. For. 13(3):127-132.

Hybridization among several North American firs. II. Hybrid verification

Seedlings resulting from 1980 controlled pollinations involving Vermont and Minnesota balsam fir (Abiesbalsamea (L.) Mill.), bracted balsam fir (A. balsamea var. phanerolepis Fern.), Fraser fir (A. fraseri (Pursh) Poir.), and white fir (A. concolor (Gord. and Glend.) Lindl.) were evaluated to verify hybridity and to describe the expression of parental characteristics in the hybrids. Putative hybrid and parental seedlings were grown indoors in replicated tests for 7 months and subsequently transplanted into an outdoor nursery. Hybrids from all combinations were verified using growth, morphological, and phenological characteristics. Hybrid seedlings were not characteristically intermediate between parents. Most hybrid combinations resembled their paternal parent in a majority of the characteristics that distinguished them from parental seedlings. The tendency for paternal or maternal resemblance in certain characteristics was responsible for considerable differences among reciprocal crosses. After 2 years in the nursery, Fraser × white fir and Fraser × balsam (Vermont) fir were fastest growing and exhibited a desirable combination of morphological and phenological characteristics.

Dormancy in Abiesfraseri seedlings at the end of the first growth cycle

Two experiments were conducted to examine the effect of chilling duration and postchilling photoperiod on breaking dormancy in Fraser fir (Abiesfraseri (Pursh) Poir.) seedlings. Chilling durations were 0, 2, 4, 6, 8, 10, or 12 weeks at 4 °C. Five postchilling photoperiods were used: 9, 12, 15, and 18 h, or a9-h natural day plus a3-h night light break with incandescent light.Rest in Fraser fir seedlings is shallow at the end of the first growth cycle. Dormant containerized plants outplanted in the spring grew abnormally, and resumed normal growth only after experiencing a winter. Those chilled 2 or more weeks broke dormancy rapidly under controlled-environment conditions and grew well under photoperiods > 15 h. Shoot elongation increased with day length, but not linearly. One-year-old seedlings taken from an outdoor nursery in early October broke dormancy under 9-h days in a greenhouse only after 4 weeks of chilling. A night light break resulted in 100% budbreak, even in nonchilled plants. Time to budbreak decreased with increasing duration of chilling. Dry matter increased linearly with chilling duration and was greatest under long days. Less chilling was required for budbreak than for maximum shoot elongation or dry matter production. Four to 6 weeks of chilling was sufficient to overcome rest.

Early genetic differentiation of sugar maple by accelerating seedling growth

A method is described for accelerating growth of sugar maple (Acersaccharum Marsh.) seedlings for early progeny and provenance evaluation and plantation establishment. Outdoor nursery production methods produced relatively small seedlings, few seed-lot differences, and no provenance differences in seedlings 4 and 16 months of age. In contrast, accelerated seedlings exhibited pronounced seed-lot and provenance differences at both ages and had a 29 and 80% height superiority at 4 and 16 months, respectively. Provenance differences in height, budbreak, nodes, and growth flushes revealed by the accelerated treatment and supplemented by seed characteristics indicate existence of Upper and Lower Peninsula races in Michigan. Accelerated growth techniques may have considerable potential for reducing the time required for genotypic evaluation of sugar maple and possibly other tree species, but results must be substantiated by subsequent field observations.

Effect of light intensity during extended photoperiod on growth of amabilis fir, mountain hemlock, and white and Engelmann spruce seedlings

Abiesamabilis (Dougl.) Forbes, Tsugamertensiana (Bong.) Carr., Piceaglauca (Moench) Voss, and Piceaengelmannii Parry seedlings were grown in an outdoor container nursery using one high-pressure sodium vapor lamp to provide a 24-h photoperiod. Eight intensities of lighting were arranged, viz., 220, 80, 40, 20, 12, 8, 5, and 0 lx.Extending the photoperiod and increasing the light intensity had a significant positive effect on the length and weight of seedling shoots and delayed terminal bud set. Root growth response to these treatments was negative, although the differences were rarely significant. Seedlings grown under a light intensity of 220 lx were the largest. The minimum intensity required to produce seedling shoot lengths which were significantly larger than the controls was in the range 20–80 lx.