ABSTRACT Industrial, automotive, and agricultural emissions release nitrogen into the atmosphere ... more ABSTRACT Industrial, automotive, and agricultural emissions release nitrogen into the atmosphere which is subsequently deposited to the surrounding terrestrial ecosystem. The Colorado Desert is impacted by nitrogen deposition from the west due to inputs from the Los Angeles air basin as well as nearby sources from agriculture in the Coachella Valley (CV). Current research within the Colorado Desert has demonstrated that anthropogenic N deposition contributes to the increased biomass of exotic invasive grasses, which compete with native species and can create enough biomass to carry fire in areas of high deposition. To measure the anthropogenic nitrogen within the CV, an array of passive air samplers was erected spanning the valley from west to east. Each sampler contained filters to passively collect both nitric acid and ammonia ions. To evaluate the degree to which the local ecosystem is supplemented by atmospheric N and determine how nitrogen pools are transformed, surface soil and leaf tissue of the dominant shrub, Larrea tridentata, were collected at each site. Only nitrate data from the samplers has currently been analyzed. delta15N, delta17O, and delta18O were obtained from atmospheric and 1M KCl soil extracts using dual isotopic analysis of NO3-. delta15N of vegetation was obtained through combustion of dried leaf tissue. The highest concentrations of atmospheric nitrate are located on the western edge of the desert in the direction toward Los Angeles, and there is also high nitrate near the Salton Sea. The isoscape produced by the isotopic analysis provides a map further describing how NO3- molecules are moving through the desert. This map shows which sources are influencing deposition sinks across the valley. Soil concentrations of nitrogen increase along the same gradient and have an inverse relationship with delta15N. Plant tissue is also less enriched in delta15N at high deposition sites, which correlates with soil values and may be caused by increased fractionation of nitrogen isotopes at high concentrations of soil N. These results advance our understanding of how nitrogen deposition is affecting the desert ecosystem. Establishing where atmospheric nitrogen originates and where it is eventually deposited will assist policymakers in regulating local emission sources.
Four experiments were conducted to examine the competitive effects of introduced annual weeds on ... more Four experiments were conducted to examine the competitive effects of introduced annual weeds on certain native and reclamation species. The first experiment was initiated by discing three sites in the Powder River Basin, Wyoming, at three distances from introduced weed seed sources. Introduced weed colonization was greatest when a seed source was located nearby. Higher weed cover resulted in reductions of percent cover, density, and richness of the native species. The second experiment was conducted in the greenhouse and was designed to determine if there are changes in response of S. kali and the native grasses Agropyron smithii and Bouteloua gracilis to competition and water regime. Both grass species had lower biomass and higher stomatal resistance when growing in mixed culture with S. kali than in pure culture in the dry regime, but there were no significant differences in the wet regime. In general, the difference in plant response between mixed and pure cultures was more pronounced in the dry than in the wet regime. The third study was a greenhouse experiment on germination and competition of S. kali (a C/sub 4/ species) with native species Lepidium densiflorum (C/sub 3/), Chenopodium pratericola (C/sub 3/), A. smithii (C/sub 3/), and B.more » gracilis (C/sub 4/) under May, June, and July temperature regimes. Salsola kali germinated equally well in all three regimes, but the other C/sub 4/ species had highest germination in the July regime and the C/sub 3/ species in the May and June regimes. The fourth study was designed to examine the effect of weed colonization on the success of mine reclamation. Little effect was observed, but colonization by introduced annuals was very low. (ERB)« less
Shifts in vegetation composition due to invasion are an aspect of global change that alters ecosy... more Shifts in vegetation composition due to invasion are an aspect of global change that alters ecosystem processes and function across the world (D' Antonio and Vitousek, 1992; Walther et al., 2002; Gonzalez et al., 2010). Terrestrial plant invasion often leads to vegetation community type conversion, such as from native shrubland to invasive grassland, which can be accompanied by changes in soil resource availability. Globally, Mediterranean ecosystems may face the greatest losses of biodiversity because of their susceptibility to multiple global change drivers, such as precipitation variability and biotic introductions (Sala et al., 2000; Stocker et al., 2013). Invasive grasses are establishing and persisting postdisturbance in the dominant Mediterranean-type shrubland in
Journal of environmental horticulture, Jun 1, 2005
To direct, fund, promote and communicate horticultural research, which increases the quality and ... more To direct, fund, promote and communicate horticultural research, which increases the quality and value of ornamental plants, improves the productivity and profitability of the nursery and landscape industry, and protects and enhances the environment. The use of any trade name in this article does not imply an endorsement of the equipment, product or process named, nor any criticism of any similar products that are not mentioned.
A vegetation chronosequence has developed on an outwash plain formed as Exit Glacier (Kenai Fjord... more A vegetation chronosequence has developed on an outwash plain formed as Exit Glacier (Kenai Fjords National Park, Alaska, U.S.A.) retreated, beginning in the late 1700s. However, much of the area deglaciated since 1950 is partly flooded most years; this has slowed succession compared to other chronosequences on glacial till. Vegetation cover, diversity, density, and plant sizes in several stands of each of seven successional stages (Barren, Isolated Plant, Patchy, Alder, Cottonwood, Spruce-Cottonwood, Spruce-Hemlock) were sampled by systematic points along line transects and belt transects. All major species were found in the Barren stage, but they differed in timing of importance in the remainder of the chronosequence. Populus balsamifera ssp. trichocarpa (black cottonwood) was the most abundant colonizer and dominated many sites up to 150 yr after deglaciation. Picea sitchensis (Sitka spruce) was present throughout the chronosequence, but not in significant numbers until the Cottonwood stage. Tsuga mertensiana (mountain hemlock) was not common until it colonized dead logs and organic soils in the Spruce-Cottonwood stage. Forested sites on hillslopes above the outwash plain were dominated by P. sitchensis and T. mertensiana. Cover of Alnus sinuata (Sitka alder) and Populus balsamifera separated the three youngest stages from the middle two while Picea sitchensis cover distinguished the oldest two stages from the others.
Seasonal tropical forests are currently experiencing rapid deforestation and changing land manage... more Seasonal tropical forests are currently experiencing rapid deforestation and changing land management practices, which in turn may permanently transform mature forests into more shrub-herbaceous dominated plant communities and planted pastures. Effective restoration efforts are therefore essential for maintaining the biodiversity and ecosystem functioning in seasonal tropical forests, yet before implementing restoration efforts we need to better understand mechanisms influencing secondary plant succession. The main objective of this study was to investigate the ecological significance mycorrhizae, the symbiotic association between plant roots and specific fungi, may have during secondary plant succession. In 2004, we selected a chronosequence of five distinct stages of secondary succession ranging from recently disturbed areas to more mature forest at El Eden Ecological Reserve in northeastern Yucatan. We determined the plant community composition, as well as, the percent vesicular-arbuscular mycorrhizae (VAM) colonization and VAM spore diversity for each of the distinct stages of succession. Based on preliminary data we found a relatively low Sorenson index for plant species composition among the different stages (0.24-0.430) compared to within specific stages (0.50- 0.789), suggesting that plant communities are changing during secondary succession. On the other hand, we detected no significant difference in vesicular-arbuscular mycorrhizal (VAM) infection among the chronosequence, with an overall average infection of 16.94%. Nevertheless, we did observe a change in VAM species from small-spored Glomus species in earlier stages of succession to larger-spored Gigaspora and Acaulospora species as the forest matures. It therefore appears that in order to maintain the biodiversity and ecosystem functioning of seasonal tropical forest attention must also be give to below ground processes such as mycorrhizal fungi
Mycorrhizal fungi consume a large sink of carbon fixed by plants and supply a large fraction of n... more Mycorrhizal fungi consume a large sink of carbon fixed by plants and supply a large fraction of nutrients. But there are a number of complex mechanisms for acquisition and transport that can vary in space and time. Global change is resulting in a general warming process caused by an anthropogenic elevated carbon dioxide (CO2) and increasing deposition of nitrogen oxide (NOx) from human activities. These directional changes alter the uptake and exchange mechanisms in novel ways. Specifically, both CO2 and nitrogen (N) availability are increasing. How mycorrhizas will respond to this novel environment is unpredictable. We present a dynamic stoichiometric conceptual approach to understand how mycorrhizal functioning might impact future soil-plant nutrition. C:N:phosphorus (P) ratios provide useful insights into processes such as photosynthesis, nutrient uptake, weathering, and mineralization. Based on this approach, we can develop predictive models for understanding mediation of soil fertility and plant production.
Page 1. °:° COLUMBIAN QUINCENTENNIAL ISSUE o~° After years of irrigation, salt covers the Paloma ... more Page 1. °:° COLUMBIAN QUINCENTENNIAL ISSUE o~° After years of irrigation, salt covers the Paloma Ranch in southern Arizona like a hoarfrost, posing a major challenge to restoration of ecosystems in this arid area. Photo by Laura Jackson The Arid West ...
Major ecosystem services provided by this system FOOD AND FOR AGE Historically, coastal sage scru... more Major ecosystem services provided by this system FOOD AND FOR AGE Historically, coastal sage scrub and interspersed forblands provided food for indigenous native Californians as docu-t went y-t wO Coastal sage scrub elsa e. Clel and, JennIFer l. Funk , and edItH b. allen UC-Mooney_text_FirstHalf.indd 429 8/29/15 5:23 PM UC-Mooney_text_FirstHalf.indd 430 8/29/15 5:23 PM UC-Mooney_text_FirstHalf.indd 431 8/29/15 5:23 PM Brassica nigra Black mustard Exotic Annual forb Generally positive Centaurea melitensis Maltese star-thistle Exotic Annual forb Generally positive Erodium cicutarium redstem filaree Exotic Annual forb Generally positive Avena fatua Wild oat Exotic Annual grass Generally positive Bromus hordeaceus Soft brome Exotic Annual grass Generally positive Bromus madritensus spp rubens red brome Exotic Annual grass Generally positive Vulpia myuros rat tail fescue Exotic Annual grass Generally positive Medicago polymorpha Bur clover Exotic Annual n-fixing forb Generally positive Cynara cardunculus Artichoke thistle Exotic Perennial forb Generally positive Hirschfeldia incana Short-podded mustard Exotic Perennial forb (short-lived) Generally positive source: Malanson and o'Leary 1982. note: reseeders may be weak resprouters if not burned to ground level; strong resprouters can also reseed.
The physiological and morphological responses of 6 wheatgrass (Agropyron) cultivars to vesicular-... more The physiological and morphological responses of 6 wheatgrass (Agropyron) cultivars to vesicular-arbusculu mycorrhizal inocu-I&ion were measured in the greenhouse. These included diploid, tetraploid, and hexaploid cultivars. Phmts had up to 94Yo infection after 4 months. The 2 diploid cultivrrs (A. cristolum cv. 'Fairway' and A. cristatum ssp. puberuhm) formed infection most rapidly, and they also had significantly reduced root biomass and higher water use effkiency with infection. A hexaploid cultivar (A. cristabun from U.S.S.R.) produced significantly more tillers with inoculation, while the tetraploid A. desertorum cv. 'Nordan' had fewer tillers and wider leaves. Inoculation increased leaf phosphorus concentration in 4 of the 6 cultivars. Carbon dioxide gas exchange rate, transpiration rate, stomata1 resistance, and N concentration were not significantly affected by mycorrhizal inoculation for any of the cultivars. The cultivar Nordrn had the greatest number of physiological and morphological increases in response to mycorrhizal infection, while A. cristatum from Iran (hexaploid) performed most poorly in that it had reduced WUE and no apparent beneficial responses to infection. There was no relationship between ploidy level and mychorrhizal response. the ability of an individual genotype to form infection, to take up P, and form acid phosphatases. Our objectives were to test the effects of mycorrhizal inoculum on several commonly used cultivar as well as wild populations of Agropyron. Methods and Materials Six cultivars with known ploidy levels (Asay and Knowles 1985, Dewey 1983) were studied for effects of mycorrhizae (Table 1). Table I. Names and ploidy levels of 6 cultivars of Agropyron used for studies on response to mycorrhiue. Name Agropyron cristatum cv. 'Fainvay' A. cristatum ssp. puberulum A. desertorum cv. 'Nordan' A. cristatum X desertorum cv. ' Hycrest' A. cristatum (Iran) A. cristatum (USSR)
... thinning in a tropical seasonal forest}, journal={Ecology in an Era of Globalization: Challen... more ... thinning in a tropical seasonal forest}, journal={Ecology in an Era of Globalization: Challenges and Opportunities for Environmental Scientists in the Americas}, year={2006}, month={January 8-12}, address={Merida, Yucatan, Mexico}, author={Vargas R, Allen MF, Allen EB} }. ...
Anthropogenic nitrogen (N) deposition is exposing plants and their arbuscular mycorrhizal fungi (... more Anthropogenic nitrogen (N) deposition is exposing plants and their arbuscular mycorrhizal fungi (AMFs) to elevated N availability, often leading to shifts in communities of AMF. However, physiological trade‐offs among AMF taxa in their response to N enrichment vs the ability to acquire other soil nutrients could have negative effects on plant and ecosystem productivity. It follows that information on the functional traits of AMF taxa can be used to generate predictions of their potential role in mediating ecosystem responses to N enrichment. Arbuscular mycorrhizal fungi taxa that produce extensive networks of external hyphae should forage for N and phosphorus (P) more effectively, but these services incur greater carbon (C) costs to the plant. If N enrichment ameliorates plant nutrient limitation, then plants may reduce C available for AMF, which in turn could eliminate AMF taxa with large extensive external hyphae from the soil community. As a result, the remaining AMF taxa may con...
ABSTRACT Industrial, automotive, and agricultural emissions release nitrogen into the atmosphere ... more ABSTRACT Industrial, automotive, and agricultural emissions release nitrogen into the atmosphere which is subsequently deposited to the surrounding terrestrial ecosystem. The Colorado Desert is impacted by nitrogen deposition from the west due to inputs from the Los Angeles air basin as well as nearby sources from agriculture in the Coachella Valley (CV). Current research within the Colorado Desert has demonstrated that anthropogenic N deposition contributes to the increased biomass of exotic invasive grasses, which compete with native species and can create enough biomass to carry fire in areas of high deposition. To measure the anthropogenic nitrogen within the CV, an array of passive air samplers was erected spanning the valley from west to east. Each sampler contained filters to passively collect both nitric acid and ammonia ions. To evaluate the degree to which the local ecosystem is supplemented by atmospheric N and determine how nitrogen pools are transformed, surface soil and leaf tissue of the dominant shrub, Larrea tridentata, were collected at each site. Only nitrate data from the samplers has currently been analyzed. delta15N, delta17O, and delta18O were obtained from atmospheric and 1M KCl soil extracts using dual isotopic analysis of NO3-. delta15N of vegetation was obtained through combustion of dried leaf tissue. The highest concentrations of atmospheric nitrate are located on the western edge of the desert in the direction toward Los Angeles, and there is also high nitrate near the Salton Sea. The isoscape produced by the isotopic analysis provides a map further describing how NO3- molecules are moving through the desert. This map shows which sources are influencing deposition sinks across the valley. Soil concentrations of nitrogen increase along the same gradient and have an inverse relationship with delta15N. Plant tissue is also less enriched in delta15N at high deposition sites, which correlates with soil values and may be caused by increased fractionation of nitrogen isotopes at high concentrations of soil N. These results advance our understanding of how nitrogen deposition is affecting the desert ecosystem. Establishing where atmospheric nitrogen originates and where it is eventually deposited will assist policymakers in regulating local emission sources.
Four experiments were conducted to examine the competitive effects of introduced annual weeds on ... more Four experiments were conducted to examine the competitive effects of introduced annual weeds on certain native and reclamation species. The first experiment was initiated by discing three sites in the Powder River Basin, Wyoming, at three distances from introduced weed seed sources. Introduced weed colonization was greatest when a seed source was located nearby. Higher weed cover resulted in reductions of percent cover, density, and richness of the native species. The second experiment was conducted in the greenhouse and was designed to determine if there are changes in response of S. kali and the native grasses Agropyron smithii and Bouteloua gracilis to competition and water regime. Both grass species had lower biomass and higher stomatal resistance when growing in mixed culture with S. kali than in pure culture in the dry regime, but there were no significant differences in the wet regime. In general, the difference in plant response between mixed and pure cultures was more pronounced in the dry than in the wet regime. The third study was a greenhouse experiment on germination and competition of S. kali (a C/sub 4/ species) with native species Lepidium densiflorum (C/sub 3/), Chenopodium pratericola (C/sub 3/), A. smithii (C/sub 3/), and B.more » gracilis (C/sub 4/) under May, June, and July temperature regimes. Salsola kali germinated equally well in all three regimes, but the other C/sub 4/ species had highest germination in the July regime and the C/sub 3/ species in the May and June regimes. The fourth study was designed to examine the effect of weed colonization on the success of mine reclamation. Little effect was observed, but colonization by introduced annuals was very low. (ERB)« less
Shifts in vegetation composition due to invasion are an aspect of global change that alters ecosy... more Shifts in vegetation composition due to invasion are an aspect of global change that alters ecosystem processes and function across the world (D' Antonio and Vitousek, 1992; Walther et al., 2002; Gonzalez et al., 2010). Terrestrial plant invasion often leads to vegetation community type conversion, such as from native shrubland to invasive grassland, which can be accompanied by changes in soil resource availability. Globally, Mediterranean ecosystems may face the greatest losses of biodiversity because of their susceptibility to multiple global change drivers, such as precipitation variability and biotic introductions (Sala et al., 2000; Stocker et al., 2013). Invasive grasses are establishing and persisting postdisturbance in the dominant Mediterranean-type shrubland in
Journal of environmental horticulture, Jun 1, 2005
To direct, fund, promote and communicate horticultural research, which increases the quality and ... more To direct, fund, promote and communicate horticultural research, which increases the quality and value of ornamental plants, improves the productivity and profitability of the nursery and landscape industry, and protects and enhances the environment. The use of any trade name in this article does not imply an endorsement of the equipment, product or process named, nor any criticism of any similar products that are not mentioned.
A vegetation chronosequence has developed on an outwash plain formed as Exit Glacier (Kenai Fjord... more A vegetation chronosequence has developed on an outwash plain formed as Exit Glacier (Kenai Fjords National Park, Alaska, U.S.A.) retreated, beginning in the late 1700s. However, much of the area deglaciated since 1950 is partly flooded most years; this has slowed succession compared to other chronosequences on glacial till. Vegetation cover, diversity, density, and plant sizes in several stands of each of seven successional stages (Barren, Isolated Plant, Patchy, Alder, Cottonwood, Spruce-Cottonwood, Spruce-Hemlock) were sampled by systematic points along line transects and belt transects. All major species were found in the Barren stage, but they differed in timing of importance in the remainder of the chronosequence. Populus balsamifera ssp. trichocarpa (black cottonwood) was the most abundant colonizer and dominated many sites up to 150 yr after deglaciation. Picea sitchensis (Sitka spruce) was present throughout the chronosequence, but not in significant numbers until the Cottonwood stage. Tsuga mertensiana (mountain hemlock) was not common until it colonized dead logs and organic soils in the Spruce-Cottonwood stage. Forested sites on hillslopes above the outwash plain were dominated by P. sitchensis and T. mertensiana. Cover of Alnus sinuata (Sitka alder) and Populus balsamifera separated the three youngest stages from the middle two while Picea sitchensis cover distinguished the oldest two stages from the others.
Seasonal tropical forests are currently experiencing rapid deforestation and changing land manage... more Seasonal tropical forests are currently experiencing rapid deforestation and changing land management practices, which in turn may permanently transform mature forests into more shrub-herbaceous dominated plant communities and planted pastures. Effective restoration efforts are therefore essential for maintaining the biodiversity and ecosystem functioning in seasonal tropical forests, yet before implementing restoration efforts we need to better understand mechanisms influencing secondary plant succession. The main objective of this study was to investigate the ecological significance mycorrhizae, the symbiotic association between plant roots and specific fungi, may have during secondary plant succession. In 2004, we selected a chronosequence of five distinct stages of secondary succession ranging from recently disturbed areas to more mature forest at El Eden Ecological Reserve in northeastern Yucatan. We determined the plant community composition, as well as, the percent vesicular-arbuscular mycorrhizae (VAM) colonization and VAM spore diversity for each of the distinct stages of succession. Based on preliminary data we found a relatively low Sorenson index for plant species composition among the different stages (0.24-0.430) compared to within specific stages (0.50- 0.789), suggesting that plant communities are changing during secondary succession. On the other hand, we detected no significant difference in vesicular-arbuscular mycorrhizal (VAM) infection among the chronosequence, with an overall average infection of 16.94%. Nevertheless, we did observe a change in VAM species from small-spored Glomus species in earlier stages of succession to larger-spored Gigaspora and Acaulospora species as the forest matures. It therefore appears that in order to maintain the biodiversity and ecosystem functioning of seasonal tropical forest attention must also be give to below ground processes such as mycorrhizal fungi
Mycorrhizal fungi consume a large sink of carbon fixed by plants and supply a large fraction of n... more Mycorrhizal fungi consume a large sink of carbon fixed by plants and supply a large fraction of nutrients. But there are a number of complex mechanisms for acquisition and transport that can vary in space and time. Global change is resulting in a general warming process caused by an anthropogenic elevated carbon dioxide (CO2) and increasing deposition of nitrogen oxide (NOx) from human activities. These directional changes alter the uptake and exchange mechanisms in novel ways. Specifically, both CO2 and nitrogen (N) availability are increasing. How mycorrhizas will respond to this novel environment is unpredictable. We present a dynamic stoichiometric conceptual approach to understand how mycorrhizal functioning might impact future soil-plant nutrition. C:N:phosphorus (P) ratios provide useful insights into processes such as photosynthesis, nutrient uptake, weathering, and mineralization. Based on this approach, we can develop predictive models for understanding mediation of soil fertility and plant production.
Page 1. °:° COLUMBIAN QUINCENTENNIAL ISSUE o~° After years of irrigation, salt covers the Paloma ... more Page 1. °:° COLUMBIAN QUINCENTENNIAL ISSUE o~° After years of irrigation, salt covers the Paloma Ranch in southern Arizona like a hoarfrost, posing a major challenge to restoration of ecosystems in this arid area. Photo by Laura Jackson The Arid West ...
Major ecosystem services provided by this system FOOD AND FOR AGE Historically, coastal sage scru... more Major ecosystem services provided by this system FOOD AND FOR AGE Historically, coastal sage scrub and interspersed forblands provided food for indigenous native Californians as docu-t went y-t wO Coastal sage scrub elsa e. Clel and, JennIFer l. Funk , and edItH b. allen UC-Mooney_text_FirstHalf.indd 429 8/29/15 5:23 PM UC-Mooney_text_FirstHalf.indd 430 8/29/15 5:23 PM UC-Mooney_text_FirstHalf.indd 431 8/29/15 5:23 PM Brassica nigra Black mustard Exotic Annual forb Generally positive Centaurea melitensis Maltese star-thistle Exotic Annual forb Generally positive Erodium cicutarium redstem filaree Exotic Annual forb Generally positive Avena fatua Wild oat Exotic Annual grass Generally positive Bromus hordeaceus Soft brome Exotic Annual grass Generally positive Bromus madritensus spp rubens red brome Exotic Annual grass Generally positive Vulpia myuros rat tail fescue Exotic Annual grass Generally positive Medicago polymorpha Bur clover Exotic Annual n-fixing forb Generally positive Cynara cardunculus Artichoke thistle Exotic Perennial forb Generally positive Hirschfeldia incana Short-podded mustard Exotic Perennial forb (short-lived) Generally positive source: Malanson and o'Leary 1982. note: reseeders may be weak resprouters if not burned to ground level; strong resprouters can also reseed.
The physiological and morphological responses of 6 wheatgrass (Agropyron) cultivars to vesicular-... more The physiological and morphological responses of 6 wheatgrass (Agropyron) cultivars to vesicular-arbusculu mycorrhizal inocu-I&ion were measured in the greenhouse. These included diploid, tetraploid, and hexaploid cultivars. Phmts had up to 94Yo infection after 4 months. The 2 diploid cultivrrs (A. cristolum cv. 'Fairway' and A. cristatum ssp. puberuhm) formed infection most rapidly, and they also had significantly reduced root biomass and higher water use effkiency with infection. A hexaploid cultivar (A. cristabun from U.S.S.R.) produced significantly more tillers with inoculation, while the tetraploid A. desertorum cv. 'Nordan' had fewer tillers and wider leaves. Inoculation increased leaf phosphorus concentration in 4 of the 6 cultivars. Carbon dioxide gas exchange rate, transpiration rate, stomata1 resistance, and N concentration were not significantly affected by mycorrhizal inoculation for any of the cultivars. The cultivar Nordrn had the greatest number of physiological and morphological increases in response to mycorrhizal infection, while A. cristatum from Iran (hexaploid) performed most poorly in that it had reduced WUE and no apparent beneficial responses to infection. There was no relationship between ploidy level and mychorrhizal response. the ability of an individual genotype to form infection, to take up P, and form acid phosphatases. Our objectives were to test the effects of mycorrhizal inoculum on several commonly used cultivar as well as wild populations of Agropyron. Methods and Materials Six cultivars with known ploidy levels (Asay and Knowles 1985, Dewey 1983) were studied for effects of mycorrhizae (Table 1). Table I. Names and ploidy levels of 6 cultivars of Agropyron used for studies on response to mycorrhiue. Name Agropyron cristatum cv. 'Fainvay' A. cristatum ssp. puberulum A. desertorum cv. 'Nordan' A. cristatum X desertorum cv. ' Hycrest' A. cristatum (Iran) A. cristatum (USSR)
... thinning in a tropical seasonal forest}, journal={Ecology in an Era of Globalization: Challen... more ... thinning in a tropical seasonal forest}, journal={Ecology in an Era of Globalization: Challenges and Opportunities for Environmental Scientists in the Americas}, year={2006}, month={January 8-12}, address={Merida, Yucatan, Mexico}, author={Vargas R, Allen MF, Allen EB} }. ...
Anthropogenic nitrogen (N) deposition is exposing plants and their arbuscular mycorrhizal fungi (... more Anthropogenic nitrogen (N) deposition is exposing plants and their arbuscular mycorrhizal fungi (AMFs) to elevated N availability, often leading to shifts in communities of AMF. However, physiological trade‐offs among AMF taxa in their response to N enrichment vs the ability to acquire other soil nutrients could have negative effects on plant and ecosystem productivity. It follows that information on the functional traits of AMF taxa can be used to generate predictions of their potential role in mediating ecosystem responses to N enrichment. Arbuscular mycorrhizal fungi taxa that produce extensive networks of external hyphae should forage for N and phosphorus (P) more effectively, but these services incur greater carbon (C) costs to the plant. If N enrichment ameliorates plant nutrient limitation, then plants may reduce C available for AMF, which in turn could eliminate AMF taxa with large extensive external hyphae from the soil community. As a result, the remaining AMF taxa may con...
Uploads
Papers by Edith Allen