Robin Rose

Effects of shade on morphology, chlorophyll concentration, and chlorophyll fluorescence of four Pacific Northwest conifer species

Four species of Pacific Northwestconifer seedlings (ponderosa pine [Pinusponderosa Dougl. ex Laws.], Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco], westernredcedar [Thuja plicata Donn ex D. Donn], andwestern hemlock [Tsuga heterophylla (Raf.)Sarg.]) were planted in individual pots and grownunder shade-cloth shelters that provided four levelsof shade (0% [full sunlight], 35%, 55%, and 75%)for approximately 30 weeks. Height growth wasrecorded every 2 weeks. Initial and final seedlingmorphology and chlorophyll concentrations weremeasured. Chlorophyll fluorescence was measuredmonthly. All species responded similarly to shade. Although height growth was greatest under 75% shadeand least in 0% shade, total biomass production wassignificantly lower and shoot:root ratio significantlyhigher in 75% shade than in 0% shade. As thetreatment shade level increased from 0% to 75%,Fv/Fm was significantly lower whilechlorophyll concentrations were significantly higher. These results indicate that photochemical efficiencyof all four species was lower under higher shade. Morphological and physiological responses differedgreatly among species and corresponded with theirdegree of shade tolerance.

Morphological and water-stress characteristics of three Douglas-fir stocktypes in relation to seedling performance under different soil moisture conditions

This one-time greenhouse study examined the phenology, morphology, frost hardiness and response to moisture stress of three Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stocktypes from the same seed lot. The types were mini-plugTM transplants (MPT), 1+1 bareroot transplants (1+1), and 2+0 bareroot seedlings (2+0). In late summer and fall before lifting, 2+0 seedling set bud before 1+1 seedlings, 1+1 seedlings before MPT seedlings. The 2+0 seedlings appeared slowest to acquire frost hardiness in fall and seemed to deharden most rapidly in spring. Although the 2+0 seedlings were taller than the MPT stocktype, MPT and 2+0 seedlings were relatively similar in other morphological respects, but 1+1 seedlings were much larger. All stocktypes were potted on January 20, 1989, placed in a greenhouse, and subjected to 39%, 18%, 16%, or 6% soil water content (% dry weight) until the end of the experiment in mid-July 1990. The largest decrease in pre-dawn xylem water potential occurred with 16% and 6% soil water content; pre-dawn xylem water potential averaged over the three stocktypes generally declined 219% from low to high soil moisture stress. The 1+1 seedlings used more water than the other two stocktypes, and at maximum soil moisture stress, plant moisture stress increased in the order: MPT <2+0<1+1. During the 6-month greenhouse experiment, the larger 1+1 stocktype showed the most absolute growth, but the smaller stocktypes grew more on a relative scale. Growth of the stocktypes appeared to be related to differences in morphology and water-use patterns as the seedlings competed for available water within each pot. The results show that MPT seedlings, a new stocktype, performed as well as the more traditionally used 2+0 and 1+1 seedlings and that stocktype selection is important in reforestation efforts.

Field Performance of Three Stock Sizes of Douglas-fir Container Seedlings Grown with Slow-release Fertilizer in the Nursery Growing Medium

Containerized coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were grown with conventional soluble fertilizer and supplemented with one of four slow-release fertilizers (SRF treatments) or unsupplemented (control treatment). Seedlings were outplanted to two sites in 1998. At the time of outplanting, SRF incorporated into the growing medium resulted in larger seedlings with higher foliar nutrient concentrations as compared to conventionally fertilized seedlings. After four growing seasons, SRF-amended seedlings at both sites had significantly greater height, basal stem diameter, and stem volume, with increases up to 19, 21, and 73%, respectively, as compared to conventionally fertilized seedlings. Additionally, three stock sizes were compared at one of the sites. Increasing stock size resulted in increased growth during the first two seasons, enabling larger stock to maintain their size advantage. Seedling responses to SRF are attributed to larger initial size, increased internal nutrient reserves at planting, and continued fertilization after planting.

Root volume as a grading criterion to improve field performance of Douglas-fir seedlings

Three seed sources of 2+0 Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seedlings were graded into three root-volume categories (<9, 9–13, and >13 cm3) and outplanted to determine (i) differences in survival and growth after one and two growing seasons in the field, (ii) relationship(s) of seedling height after one and two seasons to preplanting nursery root volume, total fresh weight, root-collar diameter, and height, and (iii) differences in field performance due to fertilization at planting. Field survival was >90% among all root-volume categories. Seedlings in the largest category grew significantly better than those in the smaller two categories over two seasons. Apparently, a population of seedlings having a large proportion of high root volumes will outperform a population having a large proportion of low root volumes in the field. Fertilization at the time of planting had no effect on survival or growth because of shallow placement of the fertilizer pellet. The results suggest that targeting root volume, as well as height and diameter, is worthwhile where morphological quality must be maximized to improve field performance. Thus, root volume has potential for use as a criterion for grading seedlings.

Soil water stress: Its effects on phenology, physiology, and morphology of containerized Douglas-fir seedlings

Containerized Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) seedlings were subjected to six moisture-stress treatments (ranging from 7 to 65% soil water content by volume) for 12 weeks. At the end of this period, there were significant differences in phenological, physiological, and morphological responses among the seedlings in the various moisture-stress treatments. In general, seedlings grown under very high or very low soil moisture conditions were adversely affected, while those grown under moderate conditions (29 to 53% soil water content) exhibited optimum growth, bud development, and nutrient and starch reserves. The use of vector analysis was found to be helpful in data interpretation. The results indicate the importance of closely monitoring nursery moisture regimes in order to achieve the best seedling quality.

Chlorophyll fluorescence and variations in tissue cold hardiness in response to freezing stress in Douglas-fir seedlings

Two-year-old coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings from two seed lots were exposed to controlled freezing temperatures every 4 weeks from October 1993 through April 1994. Freezing effects were assessed by measuring chlorophyll fluorescence emissions 1 day after freezing and by evaluating damage to the bud, cambium, and needle tissues 7 days after freezing. Differences between the seed lots as well as changes in cold hardiness among the bud, cambium, and needle tissues were evident throughout the duration of the study. Tissue damage was higher with increased freezing stress. Severity of damage to each of the tissues varied seasonally. Chlorophyll fluorescence emissions were lower with higher freezing stress (except during November and December, when test temperatures were not low enough to significantly damage the seedlings) and showed a strong relationship with morphological assessments of freezing stress. The slope of the slow kinetics phase of the chlorophyll fluorescence curve tended to be less steep (i.e., quenching was reduced) with higher freezing stress. Nonfrozen chlorophyll fluorescence measurements showed no obvious relationship with LT50 for either seed lot. However, chlorophyll fluorescence measurements are useful for determining cold hardiness and resistance to stress, because they provide a rapid assessment of seedling vigor following exposure to freezing.

Influence of nursery soil amendments on water relations, root architectural development, and field performance of Douglas-fir transplants

This experiment evaluated the influence of manure, peat, and vermiculite incorporated at low and high rates (0.0118 and 0.0236 m3/m2) and under two soil moisture regimes on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedling (1+0 for 1+1) xylem water potential (Ψxylem), whole-plant growth, root architectural development, and subsequent field performance under fertilized and non-fertilized conditions. Trends in soil moisture retention were observed (high manure > high peat > control) but there were no differences in Ψxylem. Root length in the wetter soil moisture experiment was initially (three months) greatest for seedlings in high vermiculite and least in high manure but there were no differences among treatments at lifting (eight months). Mean height was greatest for seedlings grown in vermiculite and peat (wetter nursery experiment) after two field seasons. Field fertilization (35 g/seedling) with controlled-release fertilizer in the planting hole stimulated height growth initially, but decreased height and diameter growth during the second growing season. Dramatic improvements associated with the use of nursery soil amendments were not realized, but the failure to identify negative effects, a potential reduction in disease incidence, and improvement of nursery soil physical and chemical properties may justify their use.

Fertilizantes de entrega controlada: potencial para mejorar la productividad de la reforestación

Los fertilizantes de entrega controlada (FEC) presentan un gran potencial para aumentar la competitividad de las plantas forestales para una variedad de sitios de reforestacion. Sin embargo, normalmente existe un pobre conocimiento sobre ellos. Con el fin de usar los FEC en forma exitosa se deben considerar su formulacion, el patron de entrega y sus interacciones ambientales. Este trabajo sintetiza los distintos tipos de FEC (organicos, productos con nitrogeno de lenta solubilidad y productos recubiertos) y diversas investigaciones asociadas a su utilizacion. Ademas, revisa las ventajas y desventajas asociadas a los FEC, se realizan ciertas recomendaciones sobre su utilizacion y menciona algunos de los desafios para futuras investigaciones destinadas a mejorar la comprension en las formas de aplicar los FEC en situaciones forestales.

Effects of soil water content and initial root volume on the nutrient status of 2+0 Douglas-fir seedlings

Two-year-old bareroot Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco.) seedlings were graded on the basis of four root-volume categories and transplanted to four moisture-stress treatments (6, 12, 18, and 24% soil water content) in pots. Macronutrient concentrations and contents of both old and new foliar tissue were determined. Decreasing soil water content resulted in higher concentrations of phosphorus, potassium, and particularly nitrogen in both old and new foliar tissue. This can be attributed to reduced growth, translocation, metabolic activity, and nutrient requirement in response to moisture stress. Seedlings with relatively higher root volumes exhibited higher nutrient concentrations and contents, as well as increased growth. Thus, increased total root biomass per unit of soil area with increasing seedling root volume may have resulted in greater nutrient use, supply, uptake, and storage.

Nutrient‐Release Rates of Controlled‐Release Fertilizers in Forest Soil

Abstract Nutrient‐release rates of controlled‐release fertilizer (CRF) with four different labeled release periods were evaluated. Samples (30 g) sealed with nylon mesh were buried at a clearcut forest site (Price soil series) in western Oregon, USA, in February 2000 and excavated every 7 weeks for 14 months to determine residual weight and composition. Cool, dry soil conditions apparently prolonged nutrient release beyond labeled rates; the fertilizer with the shortest release period (3–4 months) released approximately 72% of the fertilizer (by weight), whereas that with the longest release period (8–9 months) released 48%. Release varied among individual nutrients [nitrate (NO3)>ammonia (NH3)>potassium (K)>sulfur (S)>magnesium (Mg)>phosphorus (P)]. Minimal changes in micronutrient [iron (Fe), manganese (Mn), zinc (Zn), and molybdenum (Mo)] contents were attributed to the formation of insoluble compounds with P. Variable release among individual nutrients demonstrates a limitation toward delivering a full range of nutrients and suggests that further refinement of CRF technology is needed to optimize nutrient availability under realistic field conditions.