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Results for “Environmental and Experimental Botany”

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9 recordsLinked to original sources
USGS1994

Interactive effects of CO2 enrichment and temperature on the growth of dioecious Hydrilla verticillata

Experiments of plant growth responses to different CO 2 concentrations and temperatures were conducted in growth chambers to explore the interactive effects of atmospheric CO 2 enrichment and temperature on the growth and dry matter allocation of dioecious Hydrilla [Hydrilla verticillata (L.f.) Royle]. Hydrilla plants were exposed to two atmospheric CO 2 concentrations (350 and 700 ppm) and three temperatures (15, 25 and 32°C) under a 12-hr photoperiod for about 2 months. The plant growth analysis showed that elevated CO 2 appeared to enhance the growth of Hydrilla , and that the percentage of the enhancement is strongly temperature-dependent. Maximum biomass production was achieved at 700 ppm CO 2 and 32°C. At 15°C, the total dry matter production was increased about 27% by doubling CO 2 , due to a 26% enhancement of leaf biomass, a 34% enhancement of stem biomass and 16% enhancement of root biomass. At 25°C, the dry matter production was increased about 46% by doubling CO 2 , due to a 29% enhancement of leaf biomass, a 27% enhancement of stem biomass and 40% enhancement of root biomass. At 32°C, however, the percentage of the enhancement of total dry matter production by doubling CO 2 was only about 7%. The dry matter allocation among different plant parts was influenced by temperature but not by elevated CO 2 concentration.

Environmental and Experimental Botany↗
USGS1995

Abnormal chemical element concentrations in lichens of Isle Royale National Park

Lichens have been used for many years to monitor changes in deposited airborne chemical elements in many areas, but few studies have focused on areas suspected of experiencing slightly elevated pollution. Detection of subtle patterns of slightly elevated pollutants calls for developing several lines of evidence as opposed to single line studies used in heavily polluted areas. This study of two lichen species, Hypogymnia physodes and Evernia mesomorpha , in Isle Royale National Park, Michigan compares the concentrations and ranks of elements with the concentrations and ranks of the elements in the earth's crust, changes in element concentrations over a nine year period, and the geography of element concentrations in the park. S, Zn, Pb, Cd and Se were elevated in both species and higher in rank compared to the concentrations and ranks in the earth's crust. Toxic elements increased 123% in Hypogymnia and 62% in Evernia over 9 years, compared to increases of 45% and 59% for non-toxic elements in each species, respectively. Geographically, the lichens at certain localities with higher exposures experienced higher than average element concentrations. Finally, tissue concentrations of Mn, S and Se at some localities were above levels known to be either toxic or similar to those found in polluted areas. These four lines of evidence suggest that Isle Royale National Park is experiencing the onset of chronic air pollution stress from a number of sources.

Michigan↗
USGS2006

Interactive effects of substrate, hydroperiod, and nutrients on seedling growth of Salix nigra and Taxodium distichum

The large river swamps of Louisiana have complex topography and hydrology, characterized by black willow ( Salix nigra ) dominance on accreting alluvial sediments and vast areas of baldcypress ( Taxodium distichum ) deepwater swamps with highly organic substrates. Seedling survival of these two wetland tree species is influenced by their growth rate in relation to the height and duration of annual flooding in riverine environments. This study examines the interactive effects of substrate, hydroperiod, and nutrients on growth rates of black willow and baldcypress seedlings. In a greenhouse experiment with a split-split-plot design, 1-year seedlings of black willow and baldcypress were subjected to two nutrient treatments (unfertilized versus fertilized), two hydroperiods (continuously flooded versus twice daily flooding/draining), and two substrates (sand versus commercial peat mix). Response variables included height, diameter, lateral branch count, biomass, and root:stem ratio. Black willow growth in height and diameter, as well as all biomass components, were significantly greater in peat substrate than in sand. Black willow showed a significant hydroperiod-nutrient interaction wherein fertilizer increased stem and root biomass under drained conditions, but flooded plants did not respond to fertilization. Baldcypress diameter and root biomass were higher in peat than in sand, and the same two variables increased with fertilization in flooded as well as drained treatments. These results can be used in Louisiana wetland forest models as inputs of seedling growth and survival, regeneration potential, and biomass accumulation rates of black willow and baldcypress.

Environmental and Experimental Botany↗
USGS2009

Is there evidence of adaptation to tidal flooding in saplings of baldcypress subjected to different salinity regimes?

Plant populations may adapt to environmental conditions over time by developing genetically based morphological or physiological characteristics. For tidal freshwater forested wetlands, we hypothesized that the conditions under which trees developed led to ecotypic difference in response of progeny to hydroperiod. Specifically, we looked for evidence of ecotypic adaptation for tidal flooding at different salinity regimes using growth and ecophysiological characteristics of two tidal and two non-tidal source collections of baldcypress (Taxodium distichum (L.) L.C. Rich) from the southeastern United States. Saplings were subjected to treatments of hydrology (permanent versus tidal flooding) and salinity (0 versus ???2 g l -1 ) for two and a half growing seasons in a greenhouse environment. Saplings from tidal sources maintained 21-41% lower overall growth and biomass accumulation than saplings from non-tidal sources, while saplings from non-tidal sources maintained 14-19% lower overall rates of net photosynthetic assimilation, leaf transpiration, and stomatal conductance than saplings from tidal sources. However, we found no evidence for growth or physiological enhancement of saplings from tidal sources to tide, or of saplings from non-tidal sources to no tide. All saplings growing under permanent flooding exhibited reduced growth and leaf gas exchange regardless of source, with little evidence for consistent salinity effects across hydroperiods. While we reject our original hypothesis, we suggest that adaptations of coastal baldcypress to broad (rather than narrow) environmental conditions may promote ecophysiological and growth enhancements under a range of global-change-induced stressors, perhaps reflecting a natural resilience to environmental change while precluding adaptations for specific flood regimes.

Environmental and Experimental Botany↗
USGS2018

Growth stress response to sea level rise in species with contrasting functional traits: A case study in tidal freshwater forested wetlands

With rising sea levels, mortality of glycophytes can be caused by water and nutrient stress under increasing salinity. However, the relative effects of these two stressors may vary by species-specific functional traits. For example, deciduous species, with leaves typically emerging during low salinity periods of the year, may suffer less from water stress than evergreen species. We sampled two woody species with contrasting functional traits: the evergreen and N 2 -fixing waxmyrtle ( Morella cerifera ), and the deciduous and non-N 2 fixing baldcypress ( Taxodium distichum ) along a coastal river (South Carolina, USA) showing an increasing pattern of plant mortality along a salinity gradient. We first analyzed oxygen and hydrogen isotope ratios of plant stem water and river water to determine changes in plant source water at different sites. Then we analyzed foliar carbon and nitrogen isotope ratios (δ 13 C and δ 15 N) along with nitrogen and phosphorous content (%N and %P) as proxies for the water and nutrient stress. Results showed that: (1) the two species had different water sources at the higher salinity sites; (2) foliar δ 15 N values of baldcypress decreased with higher salinity while retaining a constant δ 13 C value, and both of these isotope values were positively related with foliar %P, suggesting greater nutrient stress but minor water stress under high salinity; and (3) foliar δ 13 C values of waxmyrtle increased with higher salinity while retaining a constant foliar δ 15 N value, and neither of the values was significantly related to foliar nutrients, suggesting greater water stress but minor nutrient stress under high salinity. The different responses of the two species to high salinity may be related to their differences in leaf phenology and N 2 -fixation. Our results suggest that nutrient stress, particularly of P, can contribute to stress and eventual high mortality of baldcypress exposed to salt water intrusion.

South Carolina↗
USGS2020

Projected climate and land use changes drive plant community composition in agricultural wetlands

Playa wetlands in the Great Plains, USA support a wide variety of plant species not found elsewhere in this agriculturally-dominated region due to the ephemeral presence of standing water and hydric soils within playas. If longer dry periods occur due to climate change or if changes in surrounding land use alter sediment accumulation rates and water storage capacity in playas, plant communities could experience decreased diversity, with lasting effects on ecosystem services provided by playas in the Great Plains and at a continental-level in North America. We quantified potential changes in playa wetland plant community composition associated with predicted changes in precipitation and land use in the Great Plains through the end of the 21 st century. We conducted two six-month greenhouse experiments mimicking field conditions using intact mesocosms collected from playas in Nebraska and Texas. In the precipitation experiment, treatments derived from historical precipitation observations and three future moderate emissions (CMIP5 RCP4.5) downscaled climate projections were applied to mesocosms. For the land use experiment, treatments were simulated by nitrogen (N) applications to soil ranging from 0 to 100 mg-N L -1 with each precipitation event under historical rainfall patterns, representing increasing and decreasing area in agricultural use in playa watersheds. Plant communities tended to shift toward more native species under projected future climate conditions, but as N runoff increased, native species richness decreased. Agricultural land-use surrounding playas may have a greater effect on wetland plant communities than future alterations to hydrology based on climate change in the Great Plains; thus, efforts to reduce nutrient runoff into playas would likely mitigate loss in ecosystem function in the coming decades.

Nebraska, Texas↗
USGS2001

A comparison of physiological indicators of sublethal cadmium stress in wetland plants

Physiological indices, including photosynthesis, chlorophyll fluorescence, adenylate energy charge (AEC) ratio, and leaf reflectance, were determined for Typha domingensis and Spartina alterniflora in response to increasing concentrations of Cd and compared with the growth responses of these species. Leaf expansion, the live/total ratio of plant aboveground biomass, and the aboveground regrowth rate after the initial harvests were significantly reduced with increasing Cd concentration in the growth medium. Of the four physiological responses measured, only photosynthesis and AEC responded to the Cd treatment before damage was visually apparent. Also, these indices were significantly correlated with leaf expansion rate and live/total ratio in most instances. Except at the end of the experiment, when the most stressed plants began to die, the Fv/Fm ratio was not significantly affected by the Cd treatment. The leaf spectral reflectance parameters showed no significant change during the entire treatment period. The significant correlation between the stress indicators and plant growth supported the findings that photosynthesis and AEC were the most responsive of the indicators tested, however, further research investigating other chlorophyll fluorescence and leaf reflectance parameters may demonstrate as well the value of these indicators in quantifying sublethal stress. ?? 2001 Elsevier Science B.V. All rights reserved.

Environmental and Experimental Botany↗
USGS1997

Chemical element concentrations in four lichens on a transect entering Voyageurs National Park

A three factor transect study was conducted to test the hypothesis that chemical elements from air emissions in the vicinity of International Falls, Minnesota could not be detected in lichens along a 24 km transect reaching into Voyageurs National Park. It was hypothesized that element concentrations in lichens would decline exponentially downwind and would reach background values at a distance before the park boundary. Four species ( Cladina rangiferina, Evernia mesomorpha, Hypogymnia physodes , and Parmelia sulcata ) were sampled at ten sites for 3 years and 17 chemical elements were measured. The most notable result was a curvilinear geographic trend for many elements, which decreased from International Falls and then increased towards the park. This trend was significant for many anthropogenic elements, including S, Hg, Cd, and Cr, and for all four species. This type of distribution pattern has been observed in Hypogymnia physodes in other studies downwind of a steel mill and an oil refinery. Cladina , a ground-dwelling lichen, generally had lower tissue concentrations of the elements than the three epiphytic species. Tissue concentrations over the 3 years of sampling declined an average of 12%. Sufficient evidence exists to conclude that lichen tissue element concentrations in the vicinity of International Falls may be related to local air emissions, and that an exponential decline of element concentrations downwind of the sources does not apply to this situation.

Minnesota↗
USGS1999

Geothermal elements in lichens of Yellowstone National Park, USA

Geothermal features (e.g. geysers, fumaroles, vents, and springs) emit gaseous mercury, sulfur and heavy metals and therefore, are natural sources of these elements in the atmosphere. Field studies of heavy metals in lichens in Italy have detected elevated concentrations near geothermal power plants, and have determined that the origin of mercury is from soil degassing, not soil particles. We studied this phenomenon in a geothermal area without power plants to determine the natural levels of mercury and other elements. Two common and abundant species of epiphytic lichens, Bryoria fremontii and Letharia vulpina , were collected at six localities in Yellowstone National Park, USA in 1998 and analyzed for 22 chemical elements. Thirteen elements differed significantly between species. Some elements were significantly higher in the southern part of the park, while others were higher in the north. Levels of most elements were comparable with those in other national parks and wilderness areas in the region, except Hg, which was unusually high. The most likely sources of this element are the geothermal features, which are known emitters of Hg. Multivariate analyses revealed strong positive associations of Hg with S, and negative associations with soil elements, providing strong evidence that the Hg in the lichens is the result of soil degassing of elemental Hg rather than particulate Hg directly from soils. Average Hg levels in the lichens were 140 p.p.b. in Bryoria and 110 p.p.b. in Letharia , but maxima were 291 and 243 p.p.b., respectively. In spite of this, both species were healthy and abundant throughout the park.

Idaho, Montana, Wyoming↗