62 research outputs found
Recommended from our members
Seasonal and intraspecific variability of chlorophyll fluorescence, pigmentation and growth of Pinus ponderosa subjected to elevated CO{sub 2}
Atmospheric CO{sub 2}2 is expected to double in the next century, and these increases will have substantial impact on forest ecosystems. However, the database on the effects of elevated CO{sub 2} on forests is limited, and the extent of intraspecific variability remains unknown. We are investigating the effects of elevated CO{sub 2} on the intraspecific variability of quantum yield (as measured through chlorophyll fluorescence Fv/Fm ratio) and pigmentation, and how these are correlated to variability in growth. Four-year-old Pinus ponderosa seedlings were obtained from nine different sources across California. These seedlings were grown in standard outdoor exposure chambers for sixteen months at either ambient levels of CO{sub 2}, ambient+175ppm CO{sub 2}, or ambient+350ppm CO{sub 2}. The seedlings were periodically measured for growth, pigmentation, and chlorophyll fluorescence. The results showed a variable growth response of the nine sources during all measurement periods. Increasing CO{sub 2} resulted in a decrease in Fv/Fm among sources ranging from {minus}2.1% to {minus}23.2% in February, and 3.1% to {minus}12.5% in June. The source that had the best growth throughout the study, also had a minimal reduction in quantum yield (Fv/Fm) in the presence of elevated CO{sub 2}. For the seedlings of fastest growing sources, the correspondence between total growth and chlorophyll fluorescence was strongest during the February measurement period. Our results also showed a significant reduction in pigmentation due to increased CO{sub 2}. There are at least three explanations for the different responses during each measurement periods. First, the trees could be adapting favorably to increasing CO{sub 2}. Secondly, 1993 needles could be under less physiological stress than the current year needles. Third, there is a seasonal effect dependent upon temperature or light which is influencing the Fv/Fm ratio and pigmentation
Recommended from our members
The effect of elevated carbon dioxide on a Sierra-Nevadan dominant species: Pinus ponderosa
The impact of increasing atmospheric C0{sub 2} has not been fully evaluated on western coniferous forest species. Two year old seedlings of Pinusponderosa were grown in environmentally controlled chambers under increased C0{sub 2} conditions for 6 months. These trees exhibit morphological, physiological, and biochemical alterations when compared to our controls. Analysis of whole plant biomass distribution has shown no significant effect to the root to shoot ratios, however needles subjected to elevated C0{sub 2} exhibited an increased overall specific needle mass and a decreased total needle area. Morphological changes at the needle level included decreased mesophyll to vascular tissue 91 ratio and variations in starch storage in chloroplasts. The elevated CO{sub 2} increased internal CO{sub 2} concentrations and assimilation of carbon. Biochemical assays revealed that ribulose-bisphosphate carboxylase specific activities increased on per unit area basis with C0{sub 2} treatment levels. Sucrose phosphate synthase (SPS) activities exhibited an increase of 55% in the 700 uL L{sup {minus}1} treatment. These results indicate that the sink-source relationships of these trees have shifted carbon allocation toward above ground growth, possibly due to transport limitations
The comet Halley dust and gas environment
Quantitative descriptions of environments near the nucleus of comet P /Halley have been developed to support spacecraft and mission design for the flyby encounters in March, 1986. To summarize these models as they exist just before the encounters, we review the relevant data from prior Halley apparitions and from recent cometary research. Orbital elements, visual magnitudes, and parameter values and analysis for the nucleus, gas and dust are combined to predict Halley's position, production rates, gas and dust distributions, and electromagnetic radiation field for the current perihelion passage. The predicted numerical results have been useful for estimating likely spacecraft effects, such as impact damage and attitude perturbation. Sample applications are cited, including design of a dust shield for spacecraft structure, and threshold and dynamic range selection for flight experiments. We expect that the comet's activity may be more irregular than these smoothly varying models predict, and that comparison with the flyby data will be instructive.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43774/1/11214_2004_Article_BF00175326.pd
Recommended from our members
Variability in the intraspecific response of Pinus ponderosa seedlings subjected to long-term exposure to elevated CO{sub 2}
The authors are investigating the effects of elevated CO{sub 2} and intraspecific variability on Pinus ponderosa. To analyze intraspecific variability, they included seedling source (family) as an additional treatment, using a split-plot experimental design. The three elevated CO{sub 2} treatments were ambient (approx. 350 ppm CO{sub 2}), ambient + 175 ppm CO{sub 2} and ambient +350 ppm CO{sub 2}. Their study uses the source/sink control framework at several key integrating steps, incorporating the long-term effects of elevated CO{sub 2} (insuring sufficient time for the expression of any long-term physiological and biochemical acclimation to occur) and genetics (using multiple species and multiple known genetic sources) in an attempt to ascertain the extent of overall regulation contributed by selected independent regulatory process at the physiological, biochemical and structural level. In order to assess intraspecific variability, this paper reports on the integration of measurements of photosynthesis, chlorophyll fluorescence, pigmentation, RuBPCase, SPSase to quantify the effects of elevated CO{sub 2} on the growth response of various families of the same species
Recommended from our members
Lawrence Livermore National Laboratory interests and capabilities for research on the ecological effects of global climatic and atmospheric change
The Lawrence Livermore National Laboratory (LLNL) has interests and capabilities in all three types of research that must be conducted in order to understand and predict effects of global atmospheric and climatic (i.e., environmental) changes on ecological systems and their functions (ecosystem function is perhaps most conveniently defined as mass and energy exchange and storage). These three types of research are: (1) manipulative experiments with plants and ecosystems; (2) monitoring of present ecosystem, landscape, and global exchanges and pools of energy, elements, and compounds that play important roles in ecosystem function or the physical climate system, and (3) mechanistic (i.e., hierarchic and explanatory) modeling of plant and ecosystem responses to global environmental change. Specific experimental programs, monitoring plans, and modeling activities related to evaluation of ecological effects of global environmental change that are of interest to, and that can be carried out by LLNL scientists are outlined. Several projects have the distinction of integrating modeling with empirical studies resulting in an Integrated Product (a model or set of models) that DOE or any federal policy maker could use to assess ecological effects. The authors note that any scheme for evaluating ecological effects of atmospheric and climatic change should take into account exceptional or sensitive species, in particular, rare, threatened, or endangered species
Recommended from our members
Progress report for the project: Comparison of the response of mature branches and seedlings of Pinus ponderosa to atmospheric pollution
This progress report details Lawrence Livermore National Laboratory's (LLNL) performance regarding the projects Comparison of the Response of Mature Branches and Seedlings of Pinus ponderosa to Atmospheric Pollution'' and Effects of Ozone, acid Precipitation, and Their Interactions on Mature Branches and Seedlings of Ponderosa Pine'' for the months of November 1989 to June 1990. During the last eight months, we have initiated ozone and acid precipitation exposures, and we began intensive growth, morphological, and physiological measurements. During these major physiological measurement periods, we measured photosynthesis, transpiration, stomatal conductance, respiration, antioxidant activity, pigmentation, and foliar nutrient concentration. We have also concluded the analysis of our branch autonomy experiment, which we conducted in the fall. We determined that virtually no carbon is exported among branches in close proximity to one another. This conclusion assists in validating the approach of using branches and branch exposure chambers as a means of assessing the effects of air pollution on mature trees of Ponderosa pine. 6 refs., 4 figs., 3 tabs
- …