The Relative Sensitivity of Two Bunchgrass Species to Fire

1995 ◽  
Vol 5 (3) ◽  
pp. 127 ◽  
Author(s):  
R Robberecht ◽  
GE Defosse
Keyword(s):  
Fire Severity ◽  
Biomass Productivity ◽  
Relative Sensitivity ◽  
Fire Exposure ◽  
Quantitative Index ◽  
Above Ground Biomass ◽  
Plant Mortality ◽  
Precise Control ◽  
Festuca Idahoensis ◽  
Agropyron Spicatum

The response of two bunchgrass species, Festuca idahoensis and Agropyron spicatum, to fire was examined under three levels of fire severity. The fire treatment was applied with an instrument system that allowed precise control over the intensity and duration of fire, and full documentation of the temperatures experienced in various regions of each plant during the fire and postfire cooling phases. A quantitative index of fire exposure, or severity, for each plant was obtained by integrating the temperature curve for the meristematic crown region over the fire and postfire cooling periods. No significant plant mortality was observed at any fire severity level. Although tissue damage in newly initiated culms was observed for Festuca, this did not significantly affect culm or biomass productivity. Culm production was initiated earlier and more rapidly in Festuca than Agropyron, and within 60 days after fire exposure the total number of culms produced in Festuca was nearly that of unburned plants. Above ground biomass for both species was significantly less than that of unburned plants at the end of this 60-day period. Agropyron exhibited significantly less culm and biomass production at a moderate fire severity, whereas high fire severity was required for this reduction in Festuca. Contrary to previous studies, Festuca thus appears less sensitive to fire injury than Agropyron.

Length and Timing of Grazing on Postburn Productivity of Two Bunchgrasses in an Idaho Experimental Range

1998 ◽  
Vol 8 (1) ◽  
pp. 15 ◽  
Author(s):  
SC Bunting ◽  
R Robberecht ◽  
GE Defosse
Keyword(s):  
Growing Season ◽  
Grazing Management ◽  
Plant Mortality ◽  
Grazing Tolerance ◽  
Regeneration Period ◽  
Postfire Regeneration ◽  
Defoliation Treatment ◽  
Management Policies ◽  
Festuca Idahoensis ◽  
Agropyron Spicatum

Plant mortality and productivity in semiarid grasslands may be affected by the length of time grazing is excluded during the postfire regeneration period. The degree of grazing tolerance for the semiarid bunchgrass species, Festuca idahoensis and Agropyron spicatum, exposed to fire, and how the variation in grazing tolerance was affected by the length of time allowed for undisturbed plant regeneration after fire, were central questions addressed in this study. We examined the degree of plant mortality and productivity that resulted from the interaction of fire and grazing. Plants exposed to fire alone, i.e., without subsequent defoliation, exhibited low plant mortality, although culm production was reduced relative to unburned plants. An early-season-defoliation treatment after fire resulted in the plant mortality as high as 50% for Festuca and 70% for Agropyron bunchgrasses. Plant height and the number of vegetative and reproductive culms were also most affected by this defoliation treatment. These detrimental effects were lessened when defoliation was delayed by one growing season after the fire. Although our results suggest that one growing season seems to be enough for both species to recover after the fire, more studies will be necessary to confirm these trends, and induce changes in current grazing management policies.

scholarly journals First vs. second rotation of a poplar short rotation coppice: Above-ground biomass productivity and shoot dynamics

2015 ◽  
Vol 73 ◽  
pp. 174-185 ◽  
Author(s):  
M.S. Verlinden ◽  
L.S. Broeckx ◽  
R. Ceulemans
Keyword(s):  
Biomass Productivity ◽  
Short Rotation Coppice ◽  
Above Ground Biomass ◽  
Ground Biomass ◽  
Short Rotation ◽  
Shoot Dynamics

Effects of fire severity and season of burn on Betula glandulosa growth dynamics

2004 ◽  
Vol 13 (3) ◽  
pp. 287 ◽  
Author(s):  
William J. de Groot ◽  
Ross W. Wein
Keyword(s):  
Field Experiments ◽  
Fire Severity ◽  
Growth Dynamics ◽  
Fire Regimes ◽  
Height Growth ◽  
Above Ground Biomass ◽  
Ground Biomass ◽  
High Soil Moisture ◽  
Wide Range ◽  
Betula Glandulosa

Betula glandulosa survives over a wide range of North American fire regimes by resprouting from the rhizome. Over-winter root carbohydrate reserves are important to sprout production and growth in the following spring. Nursery and field experiments were conducted to examine the effects of seasonal clipping and fire severity (lethal heat applied to different soil depths) on B. glandulosa sprouting and growth, and seasonal burning and clipping on over-winter root carbohydrate storage. Low fire severity increased sprout numbers, and low fire severity in spring caused a large increase in height growth and above-ground biomass production over a 2-year period. Mortality rates increased sharply with higher levels of fire severity. Over-winter total non-structural carbohydrate (TNC) concentrations in roots were significantly higher in plants burned immediately after leaf-flush than in mid-summer burned plants. None of the other seasonal burning or clipping treatments significantly influenced over-winter root TNC. Post-disturbance sprout growth reflected over-winter root TNC levels. B. glandulosa survives a wide range of fire frequencies by growing in plant communities that are most likely to burn in spring or autumn, and seldom burn in summer. This provides the greatest opportunity for maximum over-winter TNC storage. As well, high soil moisture after snowmelt ensures spring fires are almost always of low severity, which promotes increased sprout production, height growth and above-ground biomass.

scholarly journals Biomass and dominance of conservative species drive above-ground biomass productivity in a mediterranean-type forest of Chile

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Ariel Isaías Ayma-Romay ◽  
Horacio E. Bown
Keyword(s):  
Biomass Productivity ◽  
Well Being ◽  
Mediterranean Forests ◽  
Mass Ratio ◽  
Above Ground Biomass ◽  
Niche Complementarity ◽  
Soil Resources ◽  
Ground Biomass ◽  
Wide Range ◽  
Chilean Matorral

Abstract Background Forest productivity has a pivotal role in human well-being. Vegetation quantity, niche complementarity, mass-ratio, and soil resources are alternative/complementary ecological mechanisms driving productivity. One challenge in current forest management depends on identifying and manipulating these mechanisms to enhance productivity. This study assessed the extent to which these mechanisms control above-ground biomass productivity (AGBP) of a Chilean mediterranean-type matorral. AGBP measured as tree above-ground biomass changes over a 7-years period, was estimated for twelve 25 m × 25 m plots across a wide range of matorral compositions and structures. Variables related to canopy structure, species and functional diversity, species and functional dominance, soil texture, soil water and soil nitrogen content were measured as surrogates of the four mechanisms proposed. Linear regression models were used to test the hypotheses. A multimodel inference based on the Akaike’s information criterion was used to select the best models explaining AGBP and for identifying the relative importance of each mechanism. Results Vegetation quantity (tree density) and mass-ratio (relative biomass of Cryptocarya alba, a conservative species) were the strongest drivers increasing AGBP, while niche complementarity (richness species) and soil resources (sand, %) had a smaller effect either decreasing or increasing AGBP, respectively. This study provides the first assessment of alternative mechanisms driving AGBP in mediterranean forests of Chile. There is strong evidence suggesting that the vegetation quantity and mass-ratio mechanisms are key drivers of AGBP, such as in other tropical and temperate forests. However, in contrast with other studies from mediterranean-type forests, our results show a negative effect of species diversity and a small effect of soil resources on AGBP. Conclusion AGBP in the Chilean matorral depends mainly on the vegetation quantity and mass-ratio mechanisms. The findings of this study have implications for matorral restoration and management for the production of timber and non-timber products and carbon sequestration.

Effects of Summer Weather Modification (Irrigation) in Festuca Idahoensis-Agropyron spicatum Grasslands

1978 ◽  
Vol 31 (4) ◽  
pp. 264 ◽  
Author(s):  
D. Collins ◽  
T. Weaver
Keyword(s):  
Weather Modification ◽  
Festuca Idahoensis ◽  
Agropyron Spicatum

scholarly journals Responses of Nematodes to Ungulate Herbivory on Bluebunch Wheatgrass and Idaho Fescue in Yellowstone National Park

1994 ◽  
Vol 18 ◽  
pp. 126-130
Author(s):  
Evelyn Merrill ◽  
Jon Hak ◽  
Nancy Stanton
Keyword(s):  
Root Growth ◽  
Yellowstone National Park ◽  
Root Biomass ◽  
National Park ◽  
Growing Season ◽  
Belowground Biomass ◽  
Winter Range ◽  
Bluebunch Wheatgrass ◽  
Festuca Idahoensis ◽  
Agropyron Spicatum

Above- and belowground biomass of Idaho fescue Festuca idahoensis and bluebunch wheatgrass Agropyron spicatum and nematode densities under these plant species were sampled during the growing season inside and outside a 2-year old exclosure on Crystal Bench in Yellowstone National Park. Early in the growing season, grazed plants of both species had lower shoot and root biomass than ungrazed plants. Standing biomass of grazed plants was equal to ungrazed plants at the end of the growing season. Densities/g root biomass of phytophagous and bacterial feeding nematodes were higher under grazed than ungrazed plants of both plant species only early in the growing season. Foliar concentrations of nitrogen in grazed plants were higher than ungrazed plants but there was no difference in root nitrogen between grazed and ungrazed plants. The effects of ungulate grazing on the Northern winter range of Yellowstone National Park has recently received considerable attention (Frank 1990, Coughenour 1991, Singer 1992, Wallace submitted). Early interest in this topic centered around the question to cull or not to cull elk in the Park. However, as the concepts of "maintaining ecological processes" (Houston 1982) and "ecosystem management" (Keiter 1991) have gained acceptance in Park management, understanding the dynamics and interactions of a broader array of herbivores inhabiting the Park have become increasingly important. In this paper, we describe the results of a study which focused on the effects of aboveground herbivory on nematode density and trophic structure. Root-feeding nematodes are major herbivores in other grassland systems and may consume twice as much biomass as aboveground consumers (Ingham and Detling 1984, Stanton 1988). Houston (1982) reported that nothing is known about the effects of nematodes on the native grasses of the northern range especially in combination with aboveground grazers. We hypothesized that if spring grazing is intense, grazed plants would initially show a decline in root growth and phytophagous nematodes. Cessation of root growth is a common response of plants to grazing and may occur within the first 2-24 hours (Hodgkinson and Baas Becking 1977). Evidence to date supports the idea that phytophagous nematode densities are highest under moderate levels of grazing and low under heavily grazed and ungrazed plants (Stanton 1983, Stanton et al. 1984, Seastedt 1985, Seastedt et al. 1988). Because senescing roots, subsequent to grazing, provide increased substrates for decomposers, we also hypothesized that microbial activity and nitrogen mineralization should increase (Stanton et al. 1984). As a result, we expected to detect an increase in microbial feeding nematodes. As root regrowth occurred, we expected phytophagous nematodes to increase. However, we predicted that populations would not reach levels found under ungrazed plants because plants in grazed areas experience higher levels of nitrogen mineralization (Holland and Detling 1990) than ungrazed plants and may produce proportionally fewer numbers of root hairs (nutrient absorption organs) which serve as feeding sites for nematodes. Because of reduced densities of phytophagous nematodes and increased mineralization rates under grazed plants, we expected grazed plants to recoup their losses rapidly. The net result we predicted would be no detectable differences in aboveground or belowground biomass during years of normal rainfall. Thus, our study addressed 3 null hypotheses. First, root and shoot biomass of grazed and ungrazed plants will be similar at the end of the growing season. Second, density of phytophagous and microbial feeding nematodes will not differ between grazed and ungrazed plants. Finally, nitrogen concentration of roots and aboveground foliage will not be higher in grazed than in ungrazed plants. We focused our attention on bluebunch wheatgrass Agropyron spicatum and Idaho fescue Festuca idahoensis because of their importance as winter range forages and because Mueggler (1975) reported that bluebunch wheatgrass was more sensitive and recovered more slowly to heavy clipping than Idaho fescue.

First Evaluation of the Structural Performance of Traditional Brickwork after Standard Fire Exposure

2015 ◽  
Vol 1119 ◽  
pp. 706-715 ◽  
Author(s):  
Francesca Sciarretta
Keyword(s):  
Mechanical Properties ◽  
Heat Flow ◽  
Fire Resistance ◽  
Fire Severity ◽  
Thermal Strain ◽  
Flow Analysis ◽  
Fire Behavior ◽  
Fem Analysis ◽  
Masonry Walls ◽  
Fire Exposure

The paper addresses the issues of fire behavior of masonry walls made of traditional/historical component materials (bricks and mortar). There are reasons for coupling investigations on the residual mechanical properties to fire resistance data, aiming at a more complete knowledge of the behavior of a masonry member during and after fire exposure. The paper is part of a research that aims at investigating the relationship between fire and post-fire (i.e. residual) mechanical behavior of masonry walls, paying attention to scale-related problems and to the possible exploitation of numerical tools to establish simplified approaches. The goal is to establish relationships between fire resistance ratings under exposure and decay in mechanical properties after exposure; the parameter of wall thickness is especially investigated, by choosing four different values (i.e. 12, 25, 38 and 51 cm). This is performed by means of FEM analysis with DIANA 9.4.4 software, simulating a standard ISO 834 fire resistance test followed by a mechanical compressive failure test on each investigated type of wall. The approach, successfully tested against experimental data already available, features a preliminary transient heat flow analysis which gives a numerical prediction of fire resistance after violation of I (Insulation) criterion; then, a staggered heat flow - stress analysis repeats the heating of the wall up to insulation failure and calculates the thermal strain accounting for cracking; finally, a ‘cold’ structural analysis in compression is performed on the thermally-deformed model after cooling. The paper also addresses a way for the extended application of the research outcomes, relying on a simple approach based on the concept of equivalent fire severity.

scholarly journals Responses of Nematodes to Ungulate Herbivory on Bluebunch Wheatgrass and Idaho Fescue in Yellowstone National Park

1991 ◽  
Vol 15 ◽  
pp. 231-234
Author(s):  
Evelyn Merrill ◽  
Nancy Stanton
Keyword(s):  
Yellowstone National Park ◽  
National Park ◽  
Ecological Processes ◽  
Winter Range ◽  
Ungulate Herbivory ◽  
Bluebunch Wheatgrass ◽  
Ungulate Grazing ◽  
Northern Winter ◽  
Festuca Idahoensis ◽  
Agropyron Spicatum

The effects of ungulate grazing on the Northern winter range of Yellowstone National Park has recently received considerable attention. Early interest in this topic centered around the question to cull or not to cull elk in the Park. However, as the concepts of "maintaining ecological processes" (Houston 1982) and "ecosystem management" (Keiter 1991) have gained acceptance in Park management, understanding the dynamics and interactions of a broader array of herbivores inhabiting the Park will become increasingly important. In 1990, we studied the responses of Idaho fescue (Festuca idahoensis) and bluebunch wheatgrass (Agropyron spicatum) and their associated nematode communities to ungulate herbivory.

A Novel Reconstitution Method for Inducing the Formation of Regular 2-Dimensional Arrays of Membrane Proteins and Lipids

1988 ◽  
Vol 46 ◽  
pp. 152-153 ◽  
Author(s):  
A. Engel ◽  
A. Holzenburg ◽  
K. Stauffer ◽  
J. Rosenbusch ◽  
U. Aebi
Keyword(s):  
Membrane Proteins ◽  
Flow Rate ◽  
Lipid Membranes ◽  
Functional Characterization ◽  
Dimensional Structure ◽  
Electron Crystallography ◽  
Peltier Element ◽  
Protein Ratio ◽  
Precise Control ◽  
3 Dimensional

Reconstitution of solubilized and purified membrane proteins in the presence of phospholipids into vesicles allows their functions to be studied by simple bulk measurements (e.g. diffusion of differently sized solutes) or by conductance measurements after transformation into planar membranes. On the other hand, reconstitution into regular protein-lipid arrays, usually forming at a specific lipid-to-protein ratio, provides the basis for determining the 3-dimensional structure of membrane proteins employing the tools of electron crystallography.To refine reconstitution conditions for reproducibly inducing formation of large and highly ordered protein-lipid membranes that are suitable for both electron crystallography and patch clamping experiments aimed at their functional characterization, we built a flow-dialysis device that allows precise control of temperature and flow-rate (Fig. 1). The flow rate is generated by a peristaltic pump and can be adjusted from 1 to 500 ml/h. The dialysis buffer is brought to a preselected temperature during its travel through a meandering path before it enters the dialysis reservoir. A Z-80 based computer controls a Peltier element allowing the temperature profile to be programmed as function of time.

Multiple-fracturing and viewing of the same frozen sample at different depths using a low temperature FESEM

1996 ◽  
Vol 54 ◽  
pp. 820-821
Author(s):  
M.V. Parthasarathy ◽  
C. Daugherty
Keyword(s):  
Temperature Field ◽  
Low Temperature ◽  
Field Emission ◽  
Multiple Fracture ◽  
Precise Control ◽  
Cold Stage ◽  
Different Depths ◽  
Transfer Device

The versatility of Low Temperature Field Emission SEM (LTFESEM) for viewing frozen-hydrated biological specimens, and the high resolutions that can be obtained with such instruments have been well documented. Studies done with LTFESEM have been usually limited to the viewing of small organisms, organs, cells, and organelles, or viewing such specimens after fracturing them.We use a Hitachi 4500 FESEM equipped with a recently developed BAL-TEC SCE 020 cryopreparation/transfer device for our LTFESEM studies. The SCE 020 is similar in design to the older SCU 020 except that instead of having a dedicated stage, the SCE 020 has a detachable cold stage that mounts on to the FESEM stage when needed. Since the SCE 020 has a precisely controlled lock manipulator for transferring the specimen table from the cryopreparation chamber to the cold stage in the FESEM, and also has a motor driven microtome for precise control of specimen fracture, we have explored the feasibility of using the LTFESEM for multiple-fracture studies of the same sample.

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