Does past contact reduce the degree of mutualism in the Alnus rubra - Frankia symbiosis?

1999 ◽  
Vol 77 (3) ◽  
pp. 434-441 ◽  
Author(s):  
John H Markham ◽  
Chris P Chanway
Keyword(s):  
Soil Nitrogen ◽  
Vascular Plants ◽  
Nitrogen Isotopes ◽  
High Elevation ◽  
Plant Performance ◽  
Alnus Rubra ◽  
Fixed Nitrogen ◽  
Symbiotic Relationships ◽  
Microbial Symbionts ◽  
Whole Plants

Although most vascular plants have symbiotic relationships with soil microbes, and there is an extensive theoretical literature on the evolution of mutualism, there has been little experimental examination of the evolution of mutualism between plants and their microbial symbionts. We inoculated red alder (Alnus rubra Bong.) seedlings from three high- and three low-elevation populations with crushed nodule suspensions containing the nitrogen fixing bacterium Frankia from either the parent trees (familiar strains) or the other plant population sampled within the parent watershed (unfamiliar strains). The inoculated seedlings were planted on three high- and three low-elevation sites. Growth was monitored over the second and third year following planting, after which the whole plants were harvested. The proportion of nitrogen derived from fixation was estimated from the ratio of stable nitrogen isotopes in the harvested leaves. On low-elevation sites, which had high soil nitrogen, plants with familiar Frankia strains were half the size and derived less fixed nitrogen from their symbionts compared with plants inoculated with unfamiliar Frankia strains. On high-elevation sites, which had low soil nitrogen, the type of inoculum had little effect on plant performance, although plants with familiar inoculum were consistently larger than plants with unfamiliar inoculum. These results suggest that the degree of mutualism in this symbiosis depends on environmental conditions and may decrease with time.Key words: coevolution, Frankia, Alnus rubra, mutualism, nitrogen fixation, symbiosis.

scholarly journals Response of psychrophilic plant endosymbionts to experimental temperature increase

2020 ◽  
Vol 7 (12) ◽  
pp. 201405
Author(s):  
Carolina Seas ◽  
Priscila Chaverri
Keyword(s):  
Global Warming ◽  
Temperature Increase ◽  
Fungal Endophytes ◽  
Growth Curves ◽  
High Elevation ◽  
Trophic Levels ◽  
Initial Growth ◽  
Endemic Plant ◽  
Symbiotic Relationships ◽  
Microbial Symbionts

Countless uncertainties remain regarding the effects of global warming on biodiversity, including the ability of organisms to adapt and how that will affect obligate symbiotic relationships. The present study aimed to determine the consequences of temperature increase in the adaptation of plant endosymbionts (endophytes) that grow better at low temperatures (psychrophilic). We isolated fungal endophytes from a high-elevation (paramo) endemic plant, Chusquea subtessellata . Initial growth curves were constructed at different temperatures (4–25°C). Next, experiments were carried out in which only the psychrophilic isolates were subjected to repeated increments in temperature. After the experiments, the final growth curves showed significantly slower growth than the initial curves, and some isolates even ceased to grow. While most studies suggest that the distribution of microorganisms will expand as temperatures increase because most of these organisms grow better at 25°C, the results from our experiments demonstrate that psychrophilic fungi were negatively affected by temperature increases. These outcomes raise questions concerning the potential adaptation of beneficial endosymbiotic fungi in the already threatened high-elevation ecosystems. Assessing the consequences of global warming at all trophic levels is urgent because many species on Earth depend on their microbial symbionts for survival.

scholarly journals Stable carbon and nitrogen isotopic composition of leaves, litter, and soils of various ecosystems along an elevational and land-use gradient at Mount Kilimanjaro, Tanzania

2019 ◽  
Vol 16 (2) ◽  
pp. 409-424 ◽  
Author(s):  
Friederike Gerschlauer ◽  
Gustavo Saiz ◽  
David Schellenberger Costa ◽  
Michael Kleyer ◽  
Michael Dannenmann ◽  
...  
Keyword(s):  
Land Use ◽  
Soil Nitrogen ◽  
Forest Ecosystems ◽  
Enrichment Factors ◽  
High Elevation ◽  
Mean Annual Temperature ◽  
Carbon And Nitrogen ◽  
Mount Kilimanjaro ◽  
Intensively Managed ◽  
Soil Δ15n

Abstract. Variations in the stable isotopic composition of carbon (δ13C) and nitrogen (δ15N) of fresh leaves, litter, and topsoils were used to characterize soil organic matter dynamics of 12 tropical ecosystems in the Mount Kilimanjaro region, Tanzania. We studied a total of 60 sites distributed along five individual elevational transects (860–4550 m a.s.l.), which define a strong climatic and land-use gradient encompassing semi-natural and managed ecosystems. The combined effects of contrasting environmental conditions, vegetation, soil, and management practices had a strong impact on the δ13C and δ15N values observed in the different ecosystems. The relative abundance of C3 and C4 plants greatly determined the δ13C of a given ecosystem. In contrast, δ15N values were largely controlled by land-use intensification and climatic conditions. The large δ13C enrichment factors (δ13Clitter − δ13Csoil) and low soil C∕N ratios observed in managed and disturbed systems agree well with the notion of altered SOM dynamics. Besides the systematic removal of the plant biomass characteristic of agricultural systems, annual litterfall patterns may also explain the comparatively lower contents of C and N observed in the topsoils of these intensively managed sites. Both δ15N values and calculated δ15N-based enrichment factors (δ15Nlitter − δ15Nsoil) suggest the tightest nitrogen cycling at high-elevation (> 3000 m a.s.l.) ecosystems and more open nitrogen cycling both in grass-dominated and intensively managed cropping systems. However, claims about the nature of the N cycle (i.e. open or closed) should not be made solely on the basis of soil δ15N as other processes that barely discriminate against 15N (i.e. soil nitrate leaching) have been shown to be quite significant in Mount Kilimanjaro's forest ecosystems. The negative correlation of δ15N values with soil nitrogen content and the positive correlation with mean annual temperature suggest reduced mineralization rates and thus limited nitrogen availability, at least in high-elevation ecosystems. By contrast, intensively managed systems are characterized by lower soil nitrogen contents and warmer conditions, leading together with nitrogen fertilizer inputs to lower nitrogen retention and thus significantly higher soil δ15N values. A simple function driven by soil nitrogen content and mean annual temperature explained 68 % of the variability in soil δ15N values across all sites. Based on our results, we suggest that in addition to land-use intensification, increasing temperatures in a changing climate may promote soil carbon and nitrogen losses, thus altering the otherwise stable soil organic matter dynamics of Mount Kilimanjaro's forest ecosystems.

scholarly journals Unique genome evolution in an intracellular N2-fixing symbiont of a rhopalodiacean diatom

2014 ◽  
Vol 83 (4) ◽  
pp. 409-413 ◽  
Author(s):  
Takuro Nakayama ◽  
Yuji Inagaki
Keyword(s):  
Nitrogen Fixation ◽  
Genome Evolution ◽  
Nitrogen Compounds ◽  
Diatom Species ◽  
Comparative Genome Analysis ◽  
Fixed Nitrogen ◽  
Metabolic Capacity ◽  
Symbiotic Relationships ◽  
The Family ◽  
Spheroid Body

Cyanobacteria, the major photosynthetic prokaryotic lineage, are also known as a major nitrogen fixer in nature. N<sub>2</sub>-fixing cyanobacteria are frequently found in symbioses with various types of eukaryotes and supply fixed nitrogen compounds to their eukaryotic hosts, which congenitally lack N<sub>2</sub>-fixing abilities. Diatom species belonging to the family Rhopalodiaceae also possess cyanobacterial symbionts called spheroid bodies. Unlike other cyanobacterial N<sub>2</sub>-fixing symbionts, the spheroid bodies reside in the cytoplasm of the diatoms and are inseparable from their hosts. Recently, the first spheroid body genome from a rhopalodiacean diatom has been completely sequenced. Overall features of the genome sequence showed significant reductive genome evolution resulting in a diminution of metabolic capacity. Notably, despite its cyanobacterial origin, the spheroid body was shown to be truly incapable of photosynthesis implying that the symbiont energetically depends on the host diatom. The comparative genome analysis between the spheroid body and another N<sub>2</sub>-fixing symbiotic cyanobacterial group corresponding to the UCYN-A phylotypes – both were derived from cyanobacteria closely related to genus <em>Cyanothece</em> – revealed that the two symbionts are on similar, but explicitly distinct tracks of reductive evolution. Intimate symbiotic relationships linked by nitrogen fixation as seen in rhopalodiacean diatoms may help us better understand the evolution and mechanisms of bacterium-eukaryote endosymbioses.

Response of red alder (Alnus rubra) seedlings to a woolly alder sawfly (Eriocampa ovata) outbreak

1998 ◽  
Vol 28 (4) ◽  
pp. 591-595 ◽  
Author(s):  
John H Markham ◽  
C P Chanway
Keyword(s):  
Growth Rate ◽  
Positive Relationship ◽  
Negative Relationship ◽  
Growing Season ◽  
High Elevation ◽  
Alnus Rubra ◽  
Herbivore Damage ◽  
Red Alder ◽  
Relative Growth ◽  
High Degree

We monitored the effect of an outbreak of Eriocampa ovata L.on experimental Alnus rubra Bong. seedlings during the year of the outbreak (1993) and the following growing season. Seedlings planted on low-elevation sites had significantly more of their leaves damaged (>50% per tree) than plants on high-elevation sites (<25% per tree), with significant differences between low-elevation sites during the year of the outbreak. There was a positive relationship between the amount of herbivore damage and plant relative growth rate early in the growing season and a negative relationship by August. This suggests that the sawflies attacked the largest and fastest growing plants, reducing their growth by midsummer. Plants with the highest degree of herbivore damage were the largest by the end of the growing season with no effects on plant growth the following year. Leaves from plants that had previously been defoliated were less palatable to E. ovata in 1994, but plants with a high degree of herbivore damage in 1994 were likely plants that had a high degree of damage in 1993.

Effects of pasture improvement with superphosphate on soil pH, nitrogen and carbon in a summer rainfall environment

1991 ◽  
Vol 31 (2) ◽  
pp. 221 ◽  
Author(s):  
GJ Crocker ◽  
ICR Holford
Keyword(s):  
Organic Carbon ◽  
Predominantly White ◽  
Soil Ph ◽  
Soil Nitrogen ◽  
New South ◽  
New South Wales ◽  
Summer Rainfall ◽  
Buffering Capacity ◽  
Fixed Nitrogen ◽  
South Wales

The effects of pasture improvement on soil pH, total nitrogen, organic carbon and extractable phosphorus (P) were determined by analysing adjacent soils from improved and unimproved pastures at 67 sites on the Northern Tablelands of New South Wales. Pasture improved sites contained at least 1 clover species, predominantly white clover, and had received at least 125 kg P/ha over periods of 15-45 years. The majority of pasture improved sites contained more soil nitrogen, carbon and phosphorus and were of lower soil pH than adjacent unimproved sites. However, the decreases in pH were not statistically significant and not usually related to the magnitude of the increases in other soil fertility parameters nor to the amounts of superphosphate applied or duration of fertiliser history. The largest decline in soil pH and largest increase in organic carbon were on granitic soils which had received more than 250 kg P/ha. The relatively small decreases in soil pH and lack of relationship with fertiliser history, compared with soils from southern New South Wales, were attributed to: (i) re-cycling of legume-fixed nitrogen by summer-growing grasses; (ii) the naturally lower pH, higher nitrogen content and higher buffering capacity of many northern soils. Soil acidification therefore seems to be much slower and less frequent in the perennial pasture systems of the Northern Tablelands of New South Wales.

Changes in nitrogen and organic carbon of wheat growing soils after various periods of grazed lucerne, extended fallowing and continuous wheat

Soil Research ◽  
1981 ◽  
Vol 19 (3) ◽  
pp. 239 ◽  
Author(s):  
ICR Holford
Keyword(s):  
Organic Carbon ◽  
Soil Nitrogen ◽  
New South ◽  
Mineral Nitrogen ◽  
Soil Types ◽  
First Year ◽  
Fixed Nitrogen ◽  
Total Soil ◽  
South Wales ◽  
Total Soil Nitrogen

Changes in total and mineral nitrogen and organic carbon were measured over a nine year period in two contrasting soils of northern New South Wales after various durations of grazed lucerne, extended fallowing and continuous wheat growing. At least 2 1/2 years of lucerne ley were required to raise the total soil nitrogen above the original level on both soil types. For each year of lucerne growth the average increase (above the control treatments) in total soil nitrogen (0-15 cm) was equivalent to about 140 kg nitrogen ha-1 in the black earth and about 110 kg nitrogen ha-1 in the red-brown earth. Significantly higher levels of soil nitrogen were maintained after the lucerne treatments throughout the 9 years of measurement on the black earth and for 5 years on the red-brown earth. Lucerne had a much larger effect on nitrogen than on organic carbon, which was significantly increased only in the black earth. There were very large increases in mineral nitrogen (0-15 cm) in the first year of measurement after lucerne. Levels remained greater than they were originally for the first 4 years, and they were greater for 7 years in the black earth and 4 years in the red-brown earth following lucerne than following continuous wheat or extended fallow. The decline in mineral nitrogen during wheat cropping after lucerne was greatly increased by excessive rainfall (574 mm or more) during the fallow. Leaching was greater in the red-brown earth than in the black earth, and this explained occasional differences in nitrogen uptake by wheat between the two soil types. Some evidence suggested that under moderately moist conditions nitrogen mineralization from lucerne-fixed nitrogen was greater in the red-brown earth than in the black earth but under drier conditions it was less.

SOIL NITROGEN AND PASTURE MANAGEMENT

1978 ◽  
pp. 44-50
Author(s):  
R.A. Carran
Keyword(s):  
Soil Nitrogen ◽  
Seasonal Pattern ◽  
Nitrogen Transformations ◽  
Fixed Nitrogen ◽  
Pasture Management ◽  
Short Period ◽  
Potential Demand ◽  
High Level ◽  
Grass Growth

The seasonal pattern of nitrogen mineralization is described and compared with the potential demand for nitrogen by grasses. Peak mineralization rates occur in spring but are quite inadequate for expression of potential grass growth. Nitrogen fixation by clovers provides a significant input into the system over a short period. Consideration of the fate of fixed nitrogen shows that losses largely o&et this input unless it is maintained at a high level. The role of pasture management and fertilizer practice in this maintenance is stressed. Seasonal differences in nitrogen transformations and their influences on nitrogen losses are discussed.

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