Download or read book Physiological Responses of Loblolly Pine and Douglas fir Seedlings from Various Provenances to Timing and Frequency of Drought Stress written by Jamie E. Mosel and published by . This book was released on 2017 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: Drought is expected to increase in many parts of the world and has been shown to affect tree physiology and growth, with seedlings being particularly vulnerable. Seedling drought responses are often species dependent, and even within species different populations may demonstrate a spectrum of responses to drought, from susceptibility to resistance. As both loblolly pine (Pinus taeda) and Douglas-fir (Pseudotsuga menziesii) have broad geographic ranges, they provide an opportunity to assess drought resistances of provenances associated with a variety of site climate conditions across their ranges. Furthermore, while studies of singular drought events have revealed important information about seedling stress responses, it has been shown that drought may impart effects even following the release from drought. In some cases, effects of drought exposure can be detrimental or lethal; however, exposure to non-lethal drought may also lead to drought acclimation, which could potentially enhance seedling functioning under subsequent droughts. This potential phenotypic plasticity, i.e. the extent to which a seedling can acclimate to drought conditions, may vary across species and across provenances within a species. This study used physiological (electron transport rate, fluorescence, and water potentials) and growth (biomass accumulation and height increment) responses for two goals: 1) to assess the drought resistances of three provenances of loblolly pine and three provenances of Douglas-fir associated with varying site climate conditions, and 2) to investigate whether previous exposure to a drought results in acclimation to a second drought. We hypothesized that: 1) drought responses would differ among the provenances in accordance with associated site climate conditions (i.e., provenances associated with mesic site climates as characterized by low climatic moisture deficit and high mean annual precipitation would be drought susceptible, and more xeric site climates as characterized by high climatic moisture deficit and low mean annual precipitation would be more drought resistant) as evidenced by physiological measures of electron transport rate, fluorescence, water potentials and growth; and 2) previous exposure to drought would result in acclimation to drought as evidenced by maintenance of physiological function (i.e., higher levels of electron transport and fluorescence) in previously drought exposed seedlings compared to previously unexposed seedlings. We also hypothesized that levels of acclimation would vary among provenances. The study yielded some evidence to support the first hypothesis regarding provenance differences in drought resistances in both species. Provenance drought resistances conformed largely to expectations, though differences were less than expected. In loblolly pine, although not statistically significant, during the second drought there was a pattern of lower maximum electron transport rates, which appeared sooner in the more mesic provenance than in the other two provenances. There were also provenance differences in seedling heights, with the most xeric of the three provenances being shorter at the beginning and the end of the study. In Douglas-fir, there were significant differences in provenance and in the interaction of treatment and provenance for maximum electron rates and fluorescence. Dark-adapted fluorescence was lower in the Coos Bay (mesic site climate) provenance during drought than in the Cascades (mesic site climate) and New Mexico (xeric site climate) provenances. The New Mexico provenance showed the least differences in fluorescence between droughted and watered treatments. The study also yielded some evidence to support the second hypothesis regarding drought acclimation in both species and among provenances. During the second drought, there was a pattern of higher maximum electron transport rates and fluorescence in previously drought exposed seedlings as compared to seedlings previously unexposed to drought. This difference was significant in the mesic provenance (North Carolina) of loblolly pine, with maximum electron transport rates significantly higher in the previously drought exposed treatment compared to the newly exposed treatment during and following the second drought. Patterns of lower electron transport rates in seedlings previously unexposed to drought compared to seedlings previously exposed to drought also appeared in Douglas-fir during the second drought, though not with statistical significance. However, the most xeric provenance showed the reverse pattern during and following the second drought, with lower maximum electron transport rates in the previously drought exposed treatment compared to the treatment previously unexposed to drought. Chlorophyll fluorescence values were significantly higher during the second drought in the previously droughted treatments compared to newly drought-exposed treatments in some provenances of loblolly pine and Douglas-fir. Lastly, seedlings exposed to an early drought had significantly lower final heights than seedlings unexposed to an early drought in both species, although the differences were greater in loblolly pine than Douglas-fir. It may be that growth acclimation, especially in the form of height reductions, influenced physiological responses during a second drought. Further studies are necessary to provide more conclusive evidence in support or against the two hypotheses. Nonetheless, this study provides valuable information on the drought responses of young, greenhouse-grown seedlings of two species that are widespread in North America and that are economically important throughout the world. Further studies in a wider range of age classes, incorporating field studies or more natural settings, may help better predict plant responses in the face of changing climate.

Download or read book Physiological Response of Loblolly Pine Seedlings to Moisture stress Conditioning and Their Subsequent Performance During Water Stress written by John R. Seiler and published by . This book was released on 1984 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Physiological Responses of Four Douglas fir Populations in Three Contrasting Field Environments written by William H. Emmingham and published by . This book was released on 1974 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: When trees from 16 populations of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco. var. menziesii) were grown at ten geographically diverse locations for seven years, those from a Vancouver Island source were among the top three for height growth on nine of the ten plantations (Rowe and Ching, 1974). In contrast, growth of a west central Oregon source consistently ranked only poor or fair in comparison to other sources. Although each population was planted with the others at its home site, seldom did it grow better there than most of the introduced populations. I hypothesized that observed differences in growth among Douglas-fir populations were due to inherent differences in stomatal behavior and/or allocation of growth resources. I also hypothesized that definition of seasonal contrasts between field environments would help identify periods of environmental stress which would, in turn, help determine the factors most important in limiting productivity on different sites. I attempted to link studies of genetics, physiology and land classification together to provide a better biological foundation for improving forest productivity. I observed moisture stress, stomatal aperture, leaf resistance, cambial and leader growth for four populations of Douglas-fir at a Coast Range, Willamette Valley and Cascade Mountain plantation. Climatic factors including radiation, humidity, rainfall, soil and air temperature were recorded at each location for the 1971 growing season. Stomatal behavior for the four populations at the three locations was similar. In the spring before soils had warmed, stomata were partly closed at night and nearly wide open during the day. In early summer, stomata were wide open day and night. Later, as drought stress increased, stomata were closed at night, and partly closed during the day. After fall rains, stomata were again open day and night. Leaf conductance at the peak of drought was variable during the day, suggesting cyclic opening and closing of stomata, The southern source appeared to have higher conductance during the day although this trend could not be confirmed by statistical test. Except for unusually high values in the spring, plant moisture stress followed the expected daily and seasonal pattern. There were characteristic differences between locations but all populations were similar at a given area. A simulation of photosynthesis was developed around a model which predicted daily CO2 fixation per square decimeter of foliage. Functions were included to reduce potential photosynthesis under conditions of high moisture stress, cold soils, and frost. Predicted photosynthesis for three areas revealed major differences in seasonal activity and yearly potential. The simulation was useful in defining seasonal contributions to total production, and the effect of drought and cold stress. It also provided an index to site productivity. At the dry interior Coast Range site, 31 percent of predicted CO2 uptake occurred in the dormant season, while at the Cascade site, less than 10 percent accumulated in the same period. Almost 60 percent of growing season photosynthetic potential was not realized due to moisture stress in the interior Coast Range. At a Willamette Valley site on deep soils, less than 40 percent of growing season potential was lost because of moisture stress. The photosynthesis index, along with indexes of moisture stress and temperature, helped define more clearly the environmental restrictions on forest productivity at different sites. These methods should be useful in matching the biological potential of seed sources to suitable forest environments. Although there were accumulated differences in size of individuals from certain sources, cambial and leader growth of 311 populations were similar for the 1971 growing season. This was true for actual growth and when growth increment was normalized for initial tree size or needle mass, Partitioning of biomass into needles, branches and bole differed by area, but not by population. Trees at the Coast Range site had more needle mass per unit bole volume and grew more per unit leaf area than those in the mountain plantation. The large differences in growth between areas were interpretable through the physiological indexes which were generated from environment3l observations at each site. Analysis of growth indicated that size differences among populations were either diminishing or remaining consistent, Variations in height which prompted this study were attributed to distinctive behavior effective during establishment. Allocation of carbohydrates, photosynthetic efficiency, hormone balance, or stomatal control may be involved in explaining contrasts in early growth. Future efforts to explain genetic differences in growth of co3st3l Douglas-fir should concentrate on times when individual trees are under environmental or competitive stress.

Download or read book Response of Douglas fir Seedlings to Nitrogen Sulfur and Phosphorus Fertilizers written by M. A. Radwan and published by . This book was released on 1985 with total page 710 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Soil Compaction and Loosening Treatments Affect Loblolly Pine Growth in Pots written by Glyndon E. Hatchell and published by . This book was released on 1970 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Physiological Responses of Loblolly Pine Pinus Taeda L to Silicon and Water Stress written by Seyed F. Emadian and published by . This book was released on 1988 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Some Physiological Responses of Tree Seedlings to Soil Moisture Depletion written by Matthew Asifo Ogigirigi and published by . This book was released on 1968 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Root Growth and Physiology on Drought Resistance in Douglas fir Lodgepole Pine and White Spruce Seedlings written by Smit Julie and published by . This book was released on 1993 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Leaf Reflectance and Physiological Responses of Loblolly Pine P i n u s T a e d a L on i e To Nitrogen written by Mei-Lei Tsay and published by . This book was released on 1981 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Water Relations and Associated Morphology of Conditioned Douglas fir and Jack Pine Seedlings Subjected to Periods of Drought Stress microform written by Keith M. McClain and published by Ann Arbor, Mich. : University Microfilms International. This book was released on 1986 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt: Significant post planting mortality of young conifer seedlings often occurs on drought prone sites because seedlings fail to either establish, or maintain favourable water relations. Survival is contingent upon growth which occurs when turgor pressure is above a threshold level. Since growth after planting is influenced by nursery cultural practices, it was hypothesized that survival may be enhanced by the effect of irrigation and nutrient conditioning on seedling water relations. Principal water relation parameters estimated by traditional and pressure-volume methods were evaluated in conditioned Douglas-fir and jack pine container seedlings during imposed drought stress in a growth room and outside in raised cold frames containing two soil types. Seedling morphology and ion concentrations in the roots were also determined. Initially, declines in plant water potential (psi) were paralleled by decreases in osmotic potential (psi pi), but as stress increased, differential declines resulted in turgor pressure (psi rho) being variously maintained depending upon irrigation and level of applied KCl. Estimates of tissue elasticity during drought stress suggested that turgor maintenance was the result of solute concentration through tissue dehydration, not osmotic adjustment. During a second drought stress, declines in (psi) and (psi pi) lead to marked increases in in some treatments. In jack pine, this continued to be the result of dehydration and concentration of solutes, but in Douglas-fir, osmotic adjustment was a factor in turgor maintenance. Variable water relations in either species could not he attributed to the accumulation of any particular ion. Only root area exhibited an increase during drought stress. Mortality during recovery was significantly higher in daily than weekly irrigated seedlings and was not influenced by the level of applied KCl. Post drought evaluation of growth potential of surviving seedlings revealed that neither conditioning treatment nor successive drought stress precluded growth. Under field conditions the progressions of water relation parameters were similar to those recorded in growth room conditions, but the rapidity of the responses were affected by soil type. Results suggested the occurrence of osmotic adjustment in Douglas-fir; restrained decline in turgor pressure in jack pine was clearly the result of concentration of salutes through dehydration. Mortality was confined entirely to Douglas-fir in the clay loam soil, but in the sandy soil both species, regardless of conditioning treatment, experienced mortality at low soil water availability.

Download or read book A Regional Framework of Early Growth Response for Loblolly Pine Relative to Herbaceous Woody and Complete Competition Contol written by and published by . This book was released on 1977 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Tree Physiology and Yield Improvement written by Melvin G. R. Cannell and published by . This book was released on 1976 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon fixation efficiency. Shoot and cambial growth. Water stress and waterlogging. Frost hardiness. Mineral nutrition. Problems concerning the use of physiological selection criteria.

Download or read book Seasonal and Cumulative Loblolly Pine Development Under Two Stand Density and Fertility Levels Through Four Growing Seasons written by James D. Haywood and published by . This book was released on 1994 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Competition density effects in a loblolly pine seedling stand written by William R Harms and published by . This book was released on 1977 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Root Systems of Direct seeded and Variously Planted Loblolly Shortleaf and Pitch Pines written by Silas Little and published by . This book was released on 1964 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: S2The study was designed to compare direct seeding with several planting procedures in terms of tree performance through the period of a stand rotation. As part of the study, sample seedlings were excavated in 1962 to determine the early effects of the treatments on root systems. This paper describes and pictures the root systems, and the differences among them that related to the method of seedling establishment.S3.

Download or read book Water Relations Gas Exchange and Growth Responses of Douglas fir Seedlings to Stresses Associated with Transplanting written by Gladwin Joseph and published by . This book was released on 1996 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this thesis was to determine the physiological mechanisms that link adverse preplanting treatments of Douglas-fir, such as exposure and root pruning, to the phenomenon of transplanting shock. The objective of experiments 1 and 2 was to measure the effect of exposure and pruning on the physiology and growth of seedlings. The objective of experiment 3 was to understand the physiological mechanisms that affect shoot elongation. Two-year-old Douglas-fir seedlings were exposed or root pruned and transplanted on different dates from November through April. Water relations, gas exchange, phenology, and growth were measured during the first-year of establishment. Exposure reduced new root growth. Stomatal conductance decreased regardless of changes in water potential [psi] during the first 2 months. Time of transplanting significantly affected the stress response of seedlings. Exposed April transplants had reduced stem conducting area, probably due to cavitation. After budbreak, exposed April transplants showed reduced midday [psi] and gas exchange, whereas exposed winter transplants had recovered. Seedlings recovered a favorable [psi] and net photosynthesis before shoot elongation ceased. However, exposure caused a reduction in shoot growth and an increase in the root:shoot ratio. Removing 30-50% of the original root volume reduced shoot and root growth. Predawn [psi] remained unaffected by the root pruning treatments during the first 2 months after planting. After budbreak, midday [psi] and gas exchange of root pruned seedlings were low. Root exposure and root pruning decreased shoot [psi] and turgor during elongation of the leader. The reduced turgor did not affect the rate of cell wall hardening as measured by changes in the modulus of elasticity. Changes in cell wall elasticity closely corresponded to the ontogeny of the leader. Current shoots of stressed seedlings did not show osmotic adjustment during the period of low [psi] . Photosynthesis of stressed seedlings decreased during elongation as a result of non-stomatal mechanisms. Reduced terminal elongation induced by preplanting stresses may be caused by a reduction in cell wall extensibility rather than cell wall elasticity as a result of low turgor. Decreased photosynthesis and a higher allocation of resources to roots during establishment may also limit shoot elongation.

Download or read book Systemic Activity of Bidrin in Loblolly Pine Seedlings written by Richard Allen Werner and published by . This book was released on 1970 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: