Gary A. Ritchie

The Pressure Chamber as an Instrument for Ecological Research

Publisher Summary This chapter discusses the pressure chamber as an instrument for ecological research. It provides the workers with a thorough and useful discussion of the effective use of the pressure chamber technique. It offers a uniform terminology. To assemble, interpret, and evaluate published ecological studies the pressure chamber has been employed. And suggest areas of research where the technique is potentially useful. The chapter discusses some unknowns and problems associated with the pressure chamber. Assembly of the device and its associated components is briefly discussed. The chapter reviews the status of the pressure chamber technique in current ecological and eco-physiological research and suggests what appear to be promising new directions and applications. Four strategies for expressing and interpreting P data were explored. The pressure chamber may also be used effectively in studies of plant pathology, entomology, and pollution effects. Activities of pathogenic agents which disrupt vascular function or cause membrane damage can often be detected. Productive use of the pressure chamber technique in forestry, agriculture, and horticulture in such operations as irrigation, transplanting, and fertilization has proved successful.

Does RGP predict field performance? A debate

Root Growth Potential (RGP) has become the most commonly used and reported measure of seedling quality. It has also been used to predict field performance after planting, but not everyone agrees that this is an appropriate use. The authors were solicited by the “Making the Grade” Organizing Committee to engage in a debate on the topic “Does Root Growth Potential (RGP) predict Field Performance” with D. G. Simpson arguing the affirmative position and G. A. Ritchie the negative. Simpsons key debate points are: (1) RGP predicts actual field performance when trees are dead __ dead trees do not grow, (2) RGP predicts field performance potential when water uptake is dependent on new root growth, and (3) RGP is a practical tool to monitor and improve reforestation system performance. Ritchie, arguing against the proposition, maintains that: (1) the logic which underlies the dependence of Field Performance on rapid root growth after planting is flawed, i.e. root growth immediately following planting rarely occurs because soils during the planting season are generally below the threshold temperature for root growth, and (2) RGP does not provide enough information about the complex of interacting factors which control Field Performance to give reliable, consistent predictions. The authors conclude by proposing a conceptual model which accommodates both positions.

The commercial use of conifer rooted cuttings in forestry: a world overview

Conifer reforestation programs have traditionally been carried out using natural seeding, direct seeding or, more recently, planting with nursery-grown stock. Only within the past decade have rooted cuttings found use in large scale commercial operations. To assess the current status of this technology questionnaires were developed and mailed to 50 individuals and organizations around the world. The questionnaires were designed to collect information on: (1) annual production by region and species, (2) objectives of rooted cutting programs, (3) production procedures, (4) field performance of cuttings as compared to seedlings, and other topics.According to the 36 responses received more than 65 million conifer rooted cuttings are being produced around the world annually, with this number growing rapidly. Fully half the production is in Japan where valuable sugi (Cryptomeria japonica D. Don) cultivars have been vegetatively propagated for at least five centuries. Another 10 million or more cuttings of radiata pine (Pinus radiata D. Don) are being grown in Australia and New Zealand annually. Canada, Scandinavia, and the British Isles together produce about 21 million Norway Spruce (Picea abies [L.] Karst), Sitka spruce (P. sitchensis [Bong.] Carr) black spruce (P. mariana [Mill.] B.S.P.) and other species annually. Programs of one million or less exist in France, West Germany, Belgium, Eastern Europe, the United States and the USSR.Aside from the Japanese program and some European and Scandinavian programs, where cloning valuable genotypes is the main aim of vegetative propagation, the primary use of rooted cutting technology is for bulk production of genetically improved half or full-sib families. Other uses include production of air pollution-resistant clones in eastern Europe, and production of species which have high commercial value but are difficult to propagate from seed.Propagation methods have changed little during the past 15 years. Most cuttings are produced from hedges, stock plants, nursery seedlings or field grown trees, and rooted under mist in glass or plastic covered houses. Rooting hormones are often, but not always, used. Roughly half are grown in containers and half bareroot, generally reflecting the preferred method of seedling production in a given region. Although relatively few detailed studies have been reported, field performance of rooted cuttings appears similar to that of seedlings provided donor plants are juvenile. Key research needs are juvenility maintenance, stock plant culture, root system improvement, mechanization, and field testing.

Relationships among bud dormancy status, cold hardiness, and stress resistance in 2+0 Douglas-fir

An experiment was conducted to ascertain what relationships might exist among dormancy status, cold hardiness and stress resistance in 2+0 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), seedlings. Seedlings were lifted from a western Washington nursery on six dates spanning the 1980–81 lifting season. On each date samples of seedlings were subjected to the following treatment: (1) tumbling for 5 minutes, (2) desiccation of roots for 30 minutes at 30°C and 2.1 kPa vapor pressure deficit, (3) exposure of shoots to temperatures of −10°C, −15°C or −20°C for two hours and (4) unstressed control. On two lift dates sub-samples of seedlings were placed into −1°C storage and held for two months before the above stress treatments were administered. Bud dormancy status was determined, using a bud break test, on seedlings from each lift date before and after storage.After one growing season in the field percent survival, vigor, height growth and shoot and root weight were determined on stressed and unstressed seedlings. Survival and vigor were less affected by the stress treatments than were height and weight. Severity of stress was in the order −20°C > −15°C > desiccation > handling > −10°C. Degree of cold injury was directly related to seedling dormancy status whether dormancy status had been attained in the nursery from natural chilling or in frozen storage. Seedlings in a mid-range of dormancy release (between deep rest and quiescence) were most resistant to all imposed stresses.

A Theoretical Model for Calculation of Xylem Sap Pressure from Climatological Data

A theoretical model is presented for the calculation of stem-xylem sap pressure from climatological data in an open-grown stand of Abies procera and A. amabilis located at 1206 m elevation in the Washington Cascades. Stem-xylem sap pressure is divided into two components: (1) a base level which is a function of soil moisture, and (2) a diurnal depression in sap pressure from this base level which is a function of current atmospheric evaporative demand. Predicted values of stem-xylem sap pressure were compared to observed values and no sig- nificant difference was observed. Other plant processes such as stomatal aperture were predicted from the model. Specific deficiencies in the model were observed and are discussed. Substantial apparent nighttime transpiration occurred within these two species under laboratory and field conditions, leading to a discrepancy between base level sap pressure and soil moisture. I NTRODUCTION The integrated abiotic and biotic factors affecting plants contribute to their water status (Fritts, 1966). Since growth frequently is limited by even mild foliar desiccation (Slatyer, 1967), the understanding of plant water status is essential to evaluating plant-environment inter- actions and the resulting ecological distribution of plants. Our effort to understand plant water status has led to the formulation of a model which predicts water status of forest trees from climatological data.

Eight hundred years of clonal forestry in China: I. traditional afforestation with Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.)

In China, traditional afforestation and reforestation systems using Chinese fir (Cunninghamia lanceolata) stump cuttings and stecklings (plantable rooted cuttings) have been implemented on a large scale for at least 800 years. These systems employ: extensive site preparation, wide spacing, interplanting with agricultural crops, planting in mosaics of small-family or clonal blocks, small-block clearcut harvesting, and regenerating with cuttings, stecklings, and stump sprouts (coppicing). Clones have been selected to be well adapted to forest sites, and problems with disease and insect infestations have been rare. Traditional methods of producing, storing and planting cuttings, stecklings and stump sprouts are described.

Evidence for Error in Pressure-Bomb Estimates of Stem Xylem Potentials

The hydrostatic component of water potential was measured concurrently in stems and needles of five species of conifers (Pinus contorta, P. jeffreyi, Pseudotsuga menziesii, Abies amabilis, and A. procera). In Douglas—fir and the true firs pressure—chamber measurements of potentials were up to 4 bars more negative in stems than in needles. The difference appears to be due to filling of non—vascular xylem tissue with fluid during measurement. This tissue seems to function as a water reservoir, enabling needles to maintain relatively high turgor levels during periods of rapid transpiration. See full-text article at JSTOR

Commercial Application of Adventitious Rooting to Forestry

Zhu Xi’s lyrical and evocative lines were penned over 800 years ago. The cuttings referred to are of the Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.), China’s major timber producing conifer. A scrutiny of ancient Chinese literature led Li (1992a) to conclude that this species has been propagated by cuttings in China for over 1,000 years. Interestingly, the propagation techniques used today in China have changed little from those of ancient times.

Field survival and early height growth of Douglas-fir rooted cuttings: relationship to stem diameter and root system quality

Abstract In 1990, three studies involving 11 half-sib families of Douglas-fir rooted cuttings were established at three sites in western Washington State (USA): two with low regeneration difficulty (RD) and one with high RD. Grading and cull studies were installed on each site and a root number study on one site. The grading study compared the performance of nine classes of rooted cuttings based on stem diameter and root system quality. The cull study evaluated five different types of putative culls. The root number study determined the correlation between the number of initial roots and field performance. In the grading study survival and height growth reflected stem diameter and relative root quality on all three sites. Mean survival by treatment was in the range 92–100%, 82–97% and 66–87% across the three sites. First year height growth varied from approximately 10 cm to 20 cm and was greatest on the low RD sites. Second year height growth was from three to four times greater than first year height growth on the low RD sites and two to three times greater on the high RD site. Plants with larger diameter had higher survival and better growth than those with smaller diameter. Within each diameter class, plants with good or fair root systems outperformed those with poor root systems. Performance of seedlings and transplants was nearly identical to that of rooted cuttings with corresponding diameter and root system quality. In the cull study only trees with stem diameter

Age- and position-of-origin and rootstock effects in Douglas-fir plantlet growth and plagiotropism

Plagiotropic angle of seedling-derived Douglas-fir plantlets varied with position of adventitious bud origin on the explanted cotyledon rosette, being least at its center (18°) and greatest (45°) along the basal third of the cotyledon. When the tops of plagiotropic plantlets (55°) were grafted to seedling rootstock, they assumed a near-vertical orientation (10°), with pectinate changed to radial leaf arrangement, within 5 months. Conversely, seedling tops grafted to plagiotropic plantlet rootstock grew plagiotropically (56°). These, and other observations lead to a hypothesis that plagiotropism in cotyledon-derived plantlets results in part from an incomplete vascular connection of the root system to the shoot.In contrast, the greater plagiotropic angle in plantlets from a 12 year-old tree, decreased by only half (from 72° to 34°) after grafting to seedling rootstock. First-season height increment of these plantlets was only 60 percent of seedling or juvenile plantlet height increment, and was unaffected by rootstock type. The adult-origin plantlets exhibited mature shoot morphology, and unchanged plagiotropism after 2 years growth in large pots. Thus it appears that the culture-induced juvenile appearance and behaviour noted for this material when maintained in vitro, is dependent on the continued presence of the culture conditions.