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| | 1. |
2007 Sep 11 |
Carbon dioxide enrichment alters plant community structure and accelerates shrub growth in the shortgrass steppe
Morgan, Milchunas, LeCain, West, Mosier
Proc Natl Acad Sci U S A 2007 Sep 11;104(37):14724-14729.
Abstract
A hypothesis has been advanced that the incursion of woody plants into world grasslands over the past two centuries has been driven in part by increasing carbon dioxide concentration, [CO2], in Earth's atmosphere. Unlike the warm season forage grasses they are displacing, woody plants have a photosynthetic metabolism and carbon allocation patterns that are responsive to CO2, and many have tap roots that are more effective than grasses for reaching deep soil water stores that can be enhanced under elevated CO2. However, this commonly cited hypothesis has little direct support from manipulative experimentation and competes with more traditional theories of shrub encroachment involving climate change, management, and fire. Here, we show that, although doubling [CO2] over the Colorado shortgrass steppe had little impact on plant species diversity, it resulted in an increasingly dissimilar plant community over the 5-year experiment compared with plots maintained at present-day [CO2]. Growth at the doubled [CO2] resulted in an ≈40-fold increase in aboveground biomass and a 20-fold increase in plant cover of Artemisia frigida Willd, a common subshrub of some North American and Asian grasslands. This CO2-induced enhancement of plant growth, among the highest yet reported, provides evidence from a native grassland suggesting that rising atmospheric [CO2] may be contributing to the shrubland expansions of the past 200 years. Encroachment of shrubs into grasslands is an important problem facing rangeland managers and ranchers; this process replaces grasses, the preferred forage of domestic livestock, with species that are unsuitable for domestic livestock grazing.
[Pubmed: 17785422]
| | 2. |
1922 Apr 07 |
Weekly Reports for APRIL 7, 1922
Public Health Rep 1922 Apr 07;37(14):801-860.
[Pubmed: 19314820]
| | 3. |
1942 Feb 20 |
Weekly Reports for FEBRUARY 20, 1942
Public Health Rep 1942 Feb 20;57(8):249-284.
[Pubmed: 19315857]
| | 4. |
2009 Mar 13 |
Infection of Melanoplus sanguinipes grasshoppers following ingestion of rangeland plant species harboring vesicular stomatitis virus.
Drolet BS, Stuart MA, Derner JD
Appl. Environ. Microbiol. 2009 May;75(10):3029-33. Epub 2009 Mar 13.
Abstract
Knowledge of the many mechanisms of vesicular stomatitis virus (VSV) transmission is critical for understanding of the epidemiology of sporadic disease outbreaks in the western United States. Migratory grasshoppers [Melanoplus sanguinipes (Fabricius)] have been implicated as reservoirs and mechanical vectors of VSV. The grasshopper-cattle-grasshopper transmission cycle is based on the assumptions that (i) virus shed from clinically infected animals would contaminate pasture plants and remain infectious on plant surfaces and (ii) grasshoppers would become infected by eating the virus-contaminated plants. Our objectives were to determine the stability of VSV on common plant species of U.S. Northern Plains rangelands and to assess the potential of these plant species as a source of virus for grasshoppers. Fourteen plant species were exposed to VSV and assayed for infectious virus over time (0 to 24 h). The frequency of viable virus recovery at 24 h postexposure was as high as 73%. The two most common plant species in Northern Plains rangelands (western wheatgrass [Pascopyrum smithii] and needle and thread [Hesperostipa comata]) were fed to groups of grasshoppers. At 3 weeks postfeeding, the grasshopper infection rate was 44 to 50%. Exposure of VSV to a commonly used grasshopper pesticide resulted in complete viral inactivation. This is the first report demonstrating the stability of VSV on rangeland plant surfaces, and it suggests that a significant window of opportunity exists for grasshoppers to ingest VSV from contaminated plants. The use of grasshopper pesticides on pastures would decrease the incidence of a virus-amplifying mechanical vector and might also decontaminate pastures, thereby decreasing the inter- and intraherd spread of VSV.
[Pubmed: 19286779]
| | 5. |
2007 Jan |
The Role of Reproductive Phenology, Seedling Emergence and Establishment of Perennial Salix gordejevii in Active Sand Dune Fields
Yan, Liu, Ma, Jiang
Ann Bot 2007 Jan;99(1):19-28.
Abstract
The function of sexual reproduction of perennials in restoration of vegetation of active dune fields frequently has been underestimated. The objective of this study was to evaluate the role of sexual reproduction of the perennial Salix gordejevii in the revegetation of active dunes.
[Pubmed: 17085475]
| | 6. |
2011 May 6 |
Trace element uptake by Eleocharis equisetina (spike rush) in an abandoned acid mine tailings pond, northeastern Australia: Implications for land and water reclamation in tropical regions.
Lottermoser BG, Ashley PM
Environ Pollut. 2011 May 6; [Epub ahead of print]
Abstract
This study was conducted to determine the uptake of trace elements by the emergent wetland plant species Eleocharis equisetina at the historic Jumna tin processing plant, tropical Australia. The perennial emergent sedge was found growing in acid waters (pH 2.45) and metal-rich tailings (SnAsCuPbZn). E. equisetina displayed a pronounced acid tolerance and tendency to exclude environmentally significant elements (Al, As, Cd, Ce, Co, Cu, Fe, La, Ni, Pb, Se, Th, U, Y, Zn) from its above-substrate biomass. This study demonstrates that geobotanical and biogeochemical examinations of wetland plants at abandoned mined lands of tropical areas can reveal pioneering, metal-excluding macrophytes. Such aquatic macrophytes are of potential use in the remediation of acid mine waters and sulfidic tailings and the reclamation of disturbed acid sulfate soils in subtropical and tropical regions.
[Pubmed: 21550704]
| | 7. |
2011 Nov 11 |
The Effects of Warming and Nitrogen Addition on Soil Nitrogen Cycling in a Temperate Grassland, Northeastern China
Ma, Lü, Liu, Guo, Zhang, Yang, Wang
PLoS One 2011 Nov 11;6(11). published online before print
Abstract
Both climate warming and atmospheric nitrogen (N) deposition are predicted to affect soil N cycling in terrestrial biomes over the next century. However, the interactive effects of warming and N deposition on soil N mineralization in temperate grasslands are poorly understood.
[Pubmed: 22096609]
| | 8. |
2012 Feb 12 |
Analyzing the Impacts of Off-Road Vehicle (ORV) Trails on Watershed Processes in Wrangell-St. Elias National Park and Preserve, Alaska.
Arp CD, Simmons T
Environ Manage. 2012 Feb 12; [Epub ahead of print]
Abstract
Trails created by off-road vehicles (ORV) in boreal lowlands are known to cause local impacts, such as denuded vegetation, soil erosion, and permafrost thaw, but impacts on stream and watershed processes are less certain. In Wrangell-St. Elias National Park and Preserve (WRST), Alaska, ORV trails have caused local resource damage in intermountain lowlands with permafrost soils and abundant wetlands and there is a need to know whether these impacts are more extensive. Comparison of aerial photography from 1957, 1981, and 2004 coupled with ground surveys in 2009 reveal an increase in trail length and number and show an upslope expansion of a trail system around points of stream channel initiation. We hypothesized that these impacts could also cause premature initiation and headward expansion of channels because of lowered soil resistance and greater runoff accumulation as trails migrate upslope. Soil monitoring showed earlier and deeper thaw of the active layer in and adjacent to trails compared to reference sites. Several rainfall-runoff events during the summer of 2009 showed increased and sustained flow accumulation below trail crossings and channel shear forces sufficient to cause headward erosion of silt and peat soils. These observations of trail evolution relative to stream and wetland crossings together with process studies suggest that ORV trails are altering watershed processes. These changes in watershed processes appear to result in increasing drainage density and may also alter downstream flow regimes, water quality, and aquatic habitat. Addressing local land-use disturbances in boreal and arctic parklands with permafrost soils, such as WRST, where responses to climate change may be causing concurrent shifts in watershed processes, represents an important challenge facing resource managers.
[Pubmed: 22327506]
| | 9. |
2006 Aug |
[Growth patterns of Leymus chinensis clones under different habitat conditions in Songnen Plain of China].
Yang Y, Zhang B
Ying Yong Sheng Tai Xue Bao. 2006 Aug;17(8):1419-23.
Abstract
A tracking investigation was conducted in the Songnen Plain of China on the experimental clones of Leymus chinensis under cultivation, and the natural clones of this grass in the succession process of vegetation restoration after meadow flooding. The results showed that on aeolian sandy soil where existed enough growth space but no interspecific competition, there was a month interval between the transplanting of two experimental clones, and the sizes of these clones had a one-fold difference by the end of next growth season. During the whole growth season, the vegetative reproduction of the two experimental clones followed the same exponential pattern. After 6 years restoration succession on flooded meadow, the vegetative reproduction of clonal populations in L. chinensis + Carex duriuscula and L. chinensis + weed communities were all accorded with power function. On flooded alkaline meadow where existed interspecific competition, the natural clones could still increase their offspring numbers exponentially, and quickly expand their niche space at the same time.
[Pubmed: 17066695]
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