Comparative Study of Photosynthesis Rates between Native Red Maple and Invasive Norway Maple in the Eastern Deciduous Forest

Invasive species, such as the Norway Maple, are often able to outcompete native species, such as the Red Maple by performing more efficiently in the environment compared to the native species. In this study, we examined if the Norway maple was able to outcompete the Red Maple in the Eastern Deciduous Forest because the Norway Maple had a higher rate of photosynthesis. The study found that the Norway Maple leaves had a slightly higher rate of carbon dioxide consumption than Red Maple leaves and that the Red Maple leaves had a higher rate of oxygen production compared to the Norway Maples. Since these differences were not statistically significant, the data suggested that the differences in the rate of photosynthesis between the two tree species is most likely very small. This suggests that the rate of photosynthesis is most likely not the advantage Norway Maples have over Red Maples that allows this invader to better compete for space in a forest

Effects of flooding on photosynthesis and root respiration in Salt cedar (tamarix ramosissima), an invasive riparian shrub

The introduced shrub Tamarix ramosissima Lebed. invades riparian zones, but loses competitiveness under flooding. This was tested in Tamarix ramosissima by examining responses to flooding by soil type in a greenhouse setting. A field study examined responses of Tamarix ramosissima and other species to natural flooding. Leaf level photosynthesis rates, stomatal conductance, transpiration, and root alcohol dehydrogenase (ADH) activity were measured weekly to assess oxygen stress. In the field, stomatal conductance, leaf water potential, transpiration, canopy cover, and δ13C were measured as responses to soil water potential, soil moisture, Julian date, relative humidity, and water depth. In the greenhouse study, flooding affected Tamarix ramosissima initially. Photosynthesis rates within flooded plants ranged from 7.5 to 14 μmol CO2 m-2 s-1 during the first two weeks, but increased to 26.9 to 27 μmol CO2 m-2 s-1 by the fourth week. As flooding progressed, photosynthesis rates increased as plants became acclimated. Lower photosynthesis rates at the onset of flooding could account for the susceptibility of Tamarix ramosissima to flooding. Soil type had no effect on photosynthesis rates or on root ADH activity. Root ADH activity was higher in flooded plants compared to drained plants, indicating oxygen stress in flooded plants. The ability of Tamarix ramosissima to acclimate to flooding within four weeks indicated metabolic acclimation. In the field study, Tamarix ramosissima had lower stomatal conductance and leaf water potential compared to Populus deltoides Bartr. and Phragmites australis (Cav.) Trin. ex Steud at -1.4 MPa and 1.5 mol H2O m-2 s-1. Lower leaf water potential and stomatal conductance in the field can also account for loss of competitiveness of Tamarix ramosissima under flooding. Typha angustifolia L. had the highest canopy cover compared to Tamarix ramosissima, Melilotus officinalis (L.) Lam., Baccharis salicina Torr. & A. Gray, and Saccharum ravennae (L.) L. Differences in canopy cover indicated Typha angustifolia was more tolerant of flooding compared to Tamarix ramosissima. Nonetheless, T. ramosissima is more flooding tolerant than previously realized. Differences in physiological responses for Tamarix ramosissima could become important for ecological or management concerns with this species

Growth Response of White Spruce [Picea glauca (Moench) Voss] in Denali National Park under Warming Climate

In subarctic mountains such as Denali National Park and Preserve(DNP), vegetation shifts from alpine tundra to boreal forests caused by recent climate change are a potential threat to plant conservation and indirectly to animal habits and diversity, which could affect the experience of visitors who wish to see wildlife. The growth rate of Picea glauca (white spruce) could decrease by climate change due to drought stress, which might lead to species elimination. The shift of P. glauca towards a higher elevation would require its seedlings not only to adapt to new abiotic harsh conditions, but also to compete with other plant species that are already present

Sensitivity of a high‐elevation rocky mountain watershed to altered climate and CO2

We explored the hydrologic and ecological responses of a headwater mountain catchment, Loch Vale watershed, to climate change and doubling of atmospheric CO2 scenarios using the Regional Hydro‐Ecological Simulation System (RHESSys). A slight (2°C) cooling, comparable to conditions observed over the past 40 years, led to greater snowpack and slightly less runoff, evaporation, transpiration, and plant productivity. An increase of 2°C yielded the opposite response, but model output for an increase of 4°C showed dramatic changes in timing of hydrologic responses. The snowpack was reduced by 50%, and runoff and soil water increased and occurred 4–5 weeks earlier with 4°C warming. Alpine tundra photosynthetic rates responded more to warmer and wetter conditions than subalpine forest, but subalpine forest showed a greater response to doubling of atmospheric CO2 than tundra. Even though water use efficiency increased with the double CO2 scenario, this had little effect on basin‐wide runoff because the catchment is largely unvegetated. Changes in winter and spring climate conditions were more important to hydrologic and vegetation dynamics than changes that occurred during summer

Analysis of field measurements of carbon dioxide and water vapor fluxes

Analysis of the field measurements of carbon dioxide and water vapor fluxes is discussed. These data were examined in conjunction with reflectance obtained from helicopter mounted Modular Multiband Radiometer. These measurements are representative of the canopy scale (10 to 100 m)(exp 2) and provide a good basis for investigating the hypotheses/relationship potentially useful in remote sensing applications. All the micrometeorological data collected during FIFE-89 were processed and fluxes of CO2, water vapor, and sensible heat were calculated. Soil CO2 fluxes were also estimated. Employing these soil CO2 flux values, in conjunction with micrometeorological measurements, canopy photosynthesis is being estimated. A biochemical model of leaf photosynthesis was adapted to the prairie vegetation. The modeled leaf photosynthesis rates were scaled up to the canopy level. This model and a multiplicative stomatal conductance model are also used to calculate canopy conductance