George W. Koch

Carbon dioxide and terrestrial ecosystems.

Tree Responses to Elevated CO2 and the Implications for Forests. Effects of CO2 and Nitrogen on Growth and Nitrogen Dynamics in Ponderosa Pine: Results from the First Two Growing Seasons. Linking Above and Belowground Responses to Rising CO2 in Northern Deciduous Forest Species. The Effects of Tree Maturity on Some Responses to Elevated CO2 in Sitka Spruce. Growth Strategy and Tree Response to Elevated CO2: A Comparision of Beech and Sweet Chestnut. Litter Quality and Decomposition Rates of Foliar Litter Produced Under CO2 Enrichment. CO2 Mediated Changes in Tree Chemistry and Tree-Lepidoptera Interactions. The Jasper Ridge CO2 Experiment: Design and Motivation. Ecosystem-Level Responses of Tallgrass Prairie to Elevated CO2. Direct Effects of Elevated CO2 on Arctic Plant and Ecosystem Function. The Response of Alpine Vegetation to Elevated CO2. Long Term Elevated CO2 Exposure in a Chesapeake Bay Wetland: Ecosystem Gas Exchange, Primary Production, And Tissue Nitrogen. Free-Air CO2 Enrichment: Responses of Cotton and Wheat Crops. Response of Growth and CO2 Uptake of Spring Wheat and Faba Bean to CO2 Concentration Under Semi-Field Conditions: Comparing Results of Field Experiments and Simulations. Assessment of Rice Responses to Global Climate Change: CO2 and Temperature. Interactions Between CO2 and Nitrogen in Forests: Can We Extrapolate from the Seedling to the Stand Level? Protection from Oxidative Stress in Trees as Affected By Elevated CO2 and Temperature with Mechanistic Simulation Models: Model Components and Research Needs. Progress, Limitations, And Challenges in Modeling the Effects of Elevated CO2 on Plants and Ecosystems. Stimulation of Global Photosynthetic Carbon Influx By and Increase in Atmospheric Carbon Dioxide Concentration. Biota Growth Factor: Stimulation of Terrestrial Ecosystem Net Primary Production By Elevated Atmospheric CO2.

Compensating effects to growth of carbon partitioning changes in response to SO2-induced photosynthetic reduction in radish

SummaryExposure of plants to SO2 reduced their photosynthetic performance due tio reductions in carboxylating capacity. Although the reduced carbon gain resulted in a lower growth rate of SO2-exposed plants over that of controls, their loss of potential growth was minimized because of proportional increases in allocation to new leaf material.

Ecology of SO2 resistance - IV. Predicting metabolic responses of fumigated shrubs and trees

Summary10 broadleafed trees and shrubs native to the mediterranean climactic zone in California were surveyed for their photosynthetic and stomatal responses to SO2. These species ranged from drought deciduous to evergreen and had diverse responses to SO2. These results suggest an approach for predicting SO2 resistances of plants.We found that conductance values of plants in SO2-free air can be used to estimate the quantity of SO2 which plants absorb. These estimates are based on conductance values for plants in non-limiting environmental conditions. SO2 absorption quantities are then used to predict relative photosynthesis following the fumigation. Thus, relative photosynthesis of plants following fumigation can be predicted on the basis of conductance in SO2-free air. This approach to predicting SO2 resistances of plants includes analysis of their stomatal responses to fumigation, their characteristics of SO2 adsorption and absorption, and their change in photosynthesis resulting from SO2 stress.

The carbon balance of flowers of Diplacus aurantiacus (Scrophulariaceae)

SummaryMeasurements and modeling of photosynthesis, respiration and growth in flowers of Diplacus aurantiacus, a semidrought-deciduous shrub, indicate that they can provide 18%–25% of their total carbon requirements through photosynthesis of flower parts. Daily photosynthetic carbon fixation exceeds daily respiratory CO2 loss during most non-fruiting stages of development. However, this carbon gain fails to meet the requirements for new biomass construction during bud growth and corolla expansion. During fruiting stages, insufficient carbon is fixed to fully supply either respiration or growth.The calyx performs most of the flowers photosynthesis throughout the life of the flower. However, during stages of fruit development, the contribution of the ovary to flower photosynthesis may equal that of the calyx.

Responses of wild plants to nitrate availability - Relationships between growth rate and nitrate uptake parameters, a case study with two Bromus species, and a survey

SummaryTwo annual species of Bromus, an invader (B. hordeaceus, ex B. mollis) and a non-invader (B. intermedius), were grown for 28 days in growth chambers, at 5 and 100 μM NO3-in flowing nutrient solution. No differences between the two species were observed at either NO3-level, in terms of relative growth rate (RGR) or its components, dry matter partitioning, specific NO3-absorption rate, nitrogen concentration, and other characteristics of NO3-uptake and photosynthesis. The effects of decreasing NO3-concentration in the solution were mainly to decrease the NO3-concentration in the plants through decreased absorption rate, and to decrease the leaf area ratio through increased specific leaf mass and decreased leaf mass ratio. Organic nitrogen concentration varied little between the two treatments, which may be the reason why photosynthetic rates were not altered. Consequently, RGR was only slightly decreased in the 5-μM treatment compared to the 100-μM treatment. This is in contrast with other species, where growth is reduced at much higher NO3-concentrations. These discrepancies may be related to differences in RGR, since a log-linear relationship was found between RGR and the NO3-concentration at which growth is first reduced. In addition, a strong linear relationship was found between the RGR of these species and their maximum absorption rate for nitrate, suggesting that the growth of species with low maximum RGR may be partly regulated by nutrient uptake.

Seed weight and seed resources in relation to plant growth rate

SummaryRelative growth rate in radish is not influenced by initial seed weight.

A SYSTEM FOR CONTROLLING THE ROOT AND SHOOT ENVIRONMENT FOR PLANT GROWTH STUDIES

Abstract A growth chamber-based system was developed for controlling an array of shoot and root environmental factors for plant growth studies. A data acquisition and control system continuously monitors and regulates environmental conditions in each chamber as specified by a computer program. Shoot environmental factors which can be independently varied include air temperature, light intensity and photoperiod, relative humidity, and CO2 and SO2 gas concentrations. Root environment is controlled by regulating the temperature, pH and nitrate level of the hydroponic nutrient medium. Initial growth experiments have been conducted in which nitrate concentration in the hydroponic solution was held constant at levels from 5 mmol/m3 to 1000 mmol/m3, spanning a wide range of nitrogen limitation. Plants also have been raised either with or without SO2 (0–0.4 cm3/m3). Results of these studies show the degree of environmental control achieved, indicate the variation in plant growth response, and suggest the potential for experiments with combinations of controlled environmental stresses.

Effects of Atmospheric CO 2 Enrichment on Ecosystem CO 2 Exchange in a Nutrient and Water Limited Grassland

We have completed 3 years of a study aimed at understanding the impact of elevated atmospheric CO2 on ecosystem properties of annual grasslands at the Jasper Ridge Biological Preserve, Stanford, CA, U.S.A. Measurements of net ecosystem CO2 uptake were made on intact grassland (on serpentine and sandstone derived soils grown in open-top chambers since December 1991). We measured CO2 exchange in the field with transparent Teflon-lined acrylic chambers coupled to an open gas exchange system. Net ecosystem CO2 uptake for both the high productivity sandstone and the low productivity serpentine grassland communities ranged from 2 to 11 umol m-2 ground s 1 in 1992 and 1993, similar to rates obtained with eddy covariance techniques on the sandstone and serpentine grasslands at Jasper Ridge in a previous study. There was a significant effect of elevated CO2 on net ecosystem CO2 uptake rate (40-48% increase in 1992 and 17-117% increase in 1993: ANOVA P = 0.018). Although elevated CO2 consistently enhanced net ecosystem CO2 uptake at the growth CO2 concentrations, acclimation occurred such that elevated C02-grown ecosystems had reduced rates of CO2 uptake relative to ambient C02-grown ecosystems at either ambient or elevated CO2 measurement concentrations of CO2. The reduction in ecosystem level photosynthetic capacity in elevated CO2 treatments was accompanied by decreased foliar ribulose-bis-phosphate carboxylase (rubisco) activity on a weight basis in the species dominant in both grassland communities. Decreases in rubisco activity resulted largely from increases in leaf mass per area in elevated CO2 plants. In general, net ecosystem CO2 uptake was positively correlated with peak biomass. However, the data suggest that biomass yield for a given level of net ecosystem CO2 uptake may be lower in elevated CO2 chambers, especially in the higher productivity sandstone community.

Transport Challenges in Tall Trees

Publisher Summary Older physiological studies with tall trees tested predictions of the cohesion- tension model. In recent years, provocative proposals about the limits to tree height and size growth have sparked debate about the hydraulic and physiological constraints underlying vascular system design and function. Improved canopy access via cranes and rope-based techniques have extended the height range of trees in temperate and tropical forests suitable for well-replicated experiments. Studies of xylem transport in moderately tall trees now abound, but those of individuals close to historic maximum heights for a species, and of long distance transport in the phloem, are scarce. This chapter examines the constraints on transport imposed by extremes of height and path length, and synthesizes information on the mechanisms that may compensate for these constraints. It emphasizes issues of xylem transport, the scant relevant literature making ones treatment of phloem transport necessarily brief and speculative. Because stomatal regulation both affects, and is affected by, xylem transport and interacts with phloem transport via its influence on water potential and the production of photosynthate, the chapter also presents a new supply-loss model that links stomatal regulation to hydraulic conductivity of the xylem.