Number Of Ectomycorrhizal Root Tips Research Articles

Assessing the dual-mycorrhizal status of a widespread tree species as a model for studies on stand biogeochemistry.

Viewing plant species by their mycorrhizal type has explained a range of ecosystem processes. However, mycorrhizal type is confounded with plant phylogeny and the environments in which mycorrhizal partners occur. To circumvent these confounding effects, "dual-mycorrhizal" plant species may be potential models for testing the influence of mycorrhizal type on stand biogeochemistry. To assess their use as models, duality in mycorrhizas within a single host species must be confirmed and factors underlying their variation understood. We surveyed roots, soils, and leaves of mature aspen (Populus tremuloides) across 27 stands in western Canada spanning two biomes: boreal forest and parklands. Aspen roots were mostly ectomycorrhizal with sporadic and rare occurrences of arbuscular mycorrhizas. We further tested whether a climate moisture index predicted abundance of ectomycorrhizal roots (number of ectomycorrhizal root tips m-1 root length) surveyed at two depths (0-20cm and 20-40cm) and found that ectomycorrhizal root abundance in subsoils (20-40cm) was positively related to the index. We subsequently examined the relationships between ectomycorrhizal root abundance, leaf traits, and slow and fast pools of soil organic carbon and nitrogen. The ratio of leaf lignin:N, but not its components, increased along with ectomycorrhizal root abundance in subsoils. Soil carbon and nitrogen pools were independent of ectomycorrhizal root abundance. Our results suggest that (1) categorizing aspen as dual-mycorrhizal may overstate the functional importance of arbuscular mycorrhizas in this species and life stage, (2) water availability influences ectomycorrhizal root abundance, and (3) ectomycorrhizal root abundance coincides with leaf quality.

Long-term experimental warming and fertilization have opposing effects on ectomycorrhizal root enzyme activity and fungal community composition in Arctic tundra

As the Arctic rapidly warms, deciduous ectomycorrhizal (EcM) shrubs are expanding across the tundra. While we know how EcM host plants respond to warming and the associated nutrient release predicted for a future Arctic, considerably less is known about how EcM function will respond, despite their important role in plant nutrient acquisition in the nutrient-limited tundra. To explore how EcM-associated nutrient cycling may change, we characterized EcM-associated root enzyme activity and community in a 28-year full factorial warming and fertilization experiment in Arctic tundra. We measured activity at the individual root tip-level (pmol⋅min−1⋅mm−2 root) and used EcM root tip abundance to scale to community-level activity (pmol⋅min−1⋅cm−3 soil). We then Sanger sequenced fungi on the same root tips to pair identity with function. Linear mixed effects models and multivariate analysis showed warming and fertilization generally had opposing, and sometimes interacting, effects on EcM root-associated activity. Responses also differed depending on the scale. Fertilization decreased activity on both scales while warming dampened the effect of fertilization. Additionally, warming increased EcM root tip abundance, and therefore community-level enzyme activity. Ectomycorrhizal root tip communities changed with fertilization, but not with warming. Changes in enzyme activity were moderately correlated with both changes in fungal community and soil inorganic nitrogen concentrations. The contrast in responses of root tip-level activity and community-level activity point to a potential shift in allocation to EcM function: whereas the production of degradative enzymes may become less important for nutrient acquisition, the exploration of the soil environment through increased number of EcM root tips may become more important. Furthermore, the future role of EcM in a warmer Arctic likely depends on the magnitude of nutrient release that comes with warming. While warming may increase the importance of EcM-associated nutrient cycling if nutrient availability remains low, it has the potential to decrease their importance if nutrient availability greatly increases.

Reclamation of an abandoned burned forest using ectomycorrhizal inoculated Quercus rubra

It is recognized that inoculation with ectomycorrhizal (ECM) fungi can have a positive effect on the establishment of nursery grown seedlings and influence their survival during the first years. However, an increased effort is needed to understand their role and behavior in abandoned burned areas. We investigated tree performance of pre-inoculated Quercus rubra seedlings on a site with fire history and monitored fungal persistence and succession dynamics of the ectomycorrhizal community established. Nursery grown Q. rubra seedlings inoculated with a mixture of 6 ECM fungi (Cenococcum geophilum, Hebeloma crustuliniforme, H. mesophaeum, H. velutipes, Paxillus involutus and Scleroderma citrinum) were transplanted to Serra da Cabreira, Northern Portugal. Non-inoculated control oak seedlings were also transplanted. Two years after planting, biometric and mycorrhizal parameters were determined. The presence of the inoculated ECM fungi and the dominant ECM fungal community established was assessed by DGGE-cloning. Results showed that the bioinoculants improved the growth performance of outplanted oak seedlings, promoting a c.a. 1.6-fold increase in height and a 2.9-fold increase in the number of ECM root tips. After two years, H. mesophaeum, H. velutipes, P. involutus and S. citrinum persisted in the root system of inoculated plants. Ordination analysis demonstrated that ECM fungal communities of inoculated and non-inoculated samples were significantly different. The present work reinforces the benefits of using nursery inoculated plants in forest reclamation processes.

Ectomycorrhizal Fungal Communities of Red Pine (Pinus densiflora) Seedlings in Disturbed Sites and Undisturbed Old Forest Sites

This study aimed to investigate differences in ectomycorrhizal (ECM) fungal communities between disturbed sites and undisturbed old forest sites. ECM root tips of Pinus densiflora were collected from 4 sites disturbed by human activities and 3 undisturbed old forest sites adjacent to the disturbed sites. Results in this study showed that the number of ECM root tips, species diversity, and number of species were significantly higher in the disturbed sites than in the undisturbed sites, suggesting that the ECM fungal community structure was affected by the degree of disturbance.

Studies on the ectomycorrhizal community in a declining Quercus suber L. stand

This survey was carried out in a Quercus suber L. stand with many trees affected by the disease "oak decline". Its aim was to obtain information about both the belowground ectomycorrhizal fungal community in a declining Q. suber stand as a whole, and the ectomycorrhizal fungal community of individual tree (EFT) detected in healthy and diseased plants. To this end, we first categorized the trees into four different decline classes (one for healthy plants and three for diseased plants) and then, by using morphological and molecular tools, we identified the ectomycorrhizas isolated from samples collected near the trees with different declining classes. The ectomycorrhizal community as a whole was seen to be composed of numerous ectomycorrhizal fungal species, only some of which appeared to be dominant (Cenococcum geophilum, Lactarius chrysorrheus, and some species of Tomentella genus), while most occurred sporadically. Results show that all root tips observed are mycorrhized and that decline class does not influence the number of ectomycorrhizal root tips found in the EFTs, thus oak decline does not impact the investment in ectomycorrhizal symbiosis. However, some statistical differences can be observed in the values of evenness and taxonomic distinctness in the EFT associated with trees with different states of health. Finally, both the analysis of similarity test and the ordination technique highlight a compositional difference between the EFT associated with trees in different health conditions, but also suggest that other factors may play a role in causing these differences.

Effects of long-term temperature and nutrient manipulation on Norway spruce fine roots and mycelia production

The effects of changing climate on ectomycorrhizal (EcM) fine roots were studied in northern Sweden by manipulating soil temperature for 14 years and/or by fertilizing for 22 years. Fine root biomass, necromass, EcM root tip biomass, morphology and number as well as mycelia production were determined from soil cores and mesh bags. The fine root biomass and necromass were highest in the fertilized plots, following similar trends in the above-ground biomass, whereas the EcM root tip biomass per basal area decreased by 22 % in the fertilized plots compared to the control. Warming increased the fine root biomass, live/dead-ratio and the number of EcM root tips in the mineral soil and tended to increase the production of EcM mycelia. Greater fine root biomass meant more EcM root tips, although the tip frequency was not affected by fertilization or warming. Significantly higher specific root length of EcM root tips indicated an increased need for nutrients in warmed and in unfertilized plots. Better nutrient supply and warmer soil temperature provide a potential to increase the flow of carbon into the soil via increased fine root biomass, but the carbon balance also depends on root turnover.

Mycorrhizal symbiosis affected by different genotypes of Pinus pinaster

Higher growth rate and morphological traits have been the major criteria for selecting trees in breeding programs. The symbiotic associations between P. pinaster and ectomycorrhizal fungi can be an effective approach to enhance plant development. The aim of this work was to assess whether the establishment of mycorrhizal symbiosis at nursery stage was affected by tree breeding. Seeds of P. pinaster from a clonal population, designed to select for various traits, and from neighboring wild plants were inoculated with compatible ectomycorrhizal fungi: Suillus bovinus, Pisolithus tinctorius or Rhizopogon roseolus, and grown in individual cells containing forest soil, in a commercial forest nursery. Growth and nutritional traits, colonisation parameters and the fungal community established were assessed. R. roseolus and P. tinctorius were the most efficient isolates in promoting plant development. Inoculated selected saplings had an overall superior development than their wild counterparts, with up to a 4.9-fold in root dry weight and a 13.6-fold increase in the total number of ectomycorrhizal root tips. Differences in fungal community were revealed through the denaturing gradient gel electrophoresis profile of each treatment. The results from our study suggest that the selected genotype benefits more from the mycorrhizal association and therefore this could be a valuable biotechnological tool for the nursery production of P. pinaster.

Ectomycorrhizal root tips in relation to site and stand characteristics in Norway spruce and Scots pine stands in boreal forests

Variations in ectomycorrhizal (EcM) short root tips of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) in 16 stands throughout Finland were studied, and their relationships with latitude, organic layer C:N ratio, temperature sum and foliage biomass were determined. There were no significant differences in EcM root tip frequency (number per milligram of fine roots) or root tip mass between tree species or between northern and southern sites. The EcM root tip number per unit area of the organic layer plus the 0-30 cm mineral soil layer varied between 0.8 and 2.4 million per m(2) for Norway spruce and between 0.7 and 2.9 million per m(2) for Scots pine, and it was higher in the northern Scots pine stands than in the southern Scots pine stands. Over 80% of the EcM root tips of both species were in the organic layer and the upper 0-10 cm mineral soil layer. We related EcM root tips to foliage mass because these two components are the most important functional units in boreal tree physiology. Both species, especially the Scots pine trees, had more EcM root tips in relation to foliage mass in northern Finland than in southern Finland. Scots pine trees had more EcM root tips in relation to foliage mass than Norway spruce in the same climatic region. The EcM root tip:foliage biomass ratio of Norway spruce was positively related to the C:N ratio in the organic layer, whereas that of Scots pine was negatively related to the temperature sum. The number of EcM root tips per milligram of fine root biomass was constant, implying that trees of both species increase nutrient uptake by increasing fine root production and hence their total number of EcM tips and the area of soil occupied by mycelia. Both tree species responded to nitrogen (N) deficiency by maintaining more EcM tips per foliage unit, and this may be related to a higher proportion of N uptake in an organic form.

Effects of slash retention and wood ash addition on fine root biomass and production and fungal mycelium in a Norway spruce stand in SW Sweden

In the study reported here we examined the short-term effects (1–3 years) of slash retention (SR) and the long-term effects (13–15 years) of wood-ash application (A) on fine roots and mycorrhizae in a 40-year-old Norway spruce forest in southwest Sweden. Soil cores were used to obtain estimates of the biomass (g m −2) of roots in three diameter classes (<0.5, 0.5–1 and 1–2 mm), root length density (RLD), specific root length (SRL) and mycorrhizal root tip density (RTD). Fine root (<1 mm) length production and mortality, and mycelium production, were estimated using minirhizotron and mesh bag techniques, respectively. Compared with the control plots (C), the biomass of fine roots in diameter classes <0.5 mm and 0.5–1 mm was significantly higher in A plots, but lower in SR plots. In addition, RLD was significantly lower in the humus layer of SR plots than in the humus layers of C and A plots, but not in the other layers. None of the treatments affected the SRL. In all soil layers, the SR treatment resulted in significant reductions in the number of ectomycorrhizal root tips, and the mycelia production of fungi in mesh bags, relative to the C treatment, but the C and A treatments induced no significant changes in these variables. Fine root length production in the C, A and SR plots amounted to 94, 87 and 70 mm tube −1 during the 2003 growing season, respectively. Fine root mortality in treated plots did not change over the course of the study. We suggest that leaving logging residues on fertile sites may result in nitrogen mineralisation, which may in turn induce reductions in root biomass, and both root and mycelium production, and consequently affect nutrient uptake and the accumulation of organic carbon in soil derived from roots and mycorrhizae.

Belowground ectomycorrhizal community structure of mature lodgepole pine and mixed conifer stands in Yellowstone National Park

Forest development patterns following wildfire are known to influence the physical and chemical attributes of soils at different points in time, and are further thought to influence ectomycorrhizal (ECM) community structure. We used molecular methods to compare belowground ECM species richness, composition, and abundance between adjacent stands of homogenous lodgepole pine (established after a fire around 1867) and old growth mixed conifer (around 300 years old) in Yellowstone National Park (YNP). In each stand type, we collected soil cores to both identify mycorrhizae and assess soil chemistry. Although no statistical difference was observed in the mean number of ECM root tips per core between stand types, the total number of species identified (81 versus 35) and the mean number of species per core (8.7 ± 0.5 versus 2.5 ± 0.3) were significantly higher in lodgepole pine. Species compositions were widely disparate between stands where only four of 112 species were shared. Soil analysis revealed that mixed conifer was significantly lower in mean pH, but higher in mean organic matter, potassium, phosphorus, and ammonium when compared to lodgepole pine. Although analysis of covariance did not statistically demonstrate that soil chemistry is driving ECM community structure with certainty, our data are, nonetheless, consistent with this hypothesis. Our data further suggest that fungal richness declines and composition shifts some time after Engelmann spruce and subalpine fir colonize mature lodgepole pine stands, and that time since last wildfire influences soil chemistry in this system. Moreover, because of data limitations, future field experiments will be necessary to determine if soil chemistry, as well as other biotic and abiotic factors not examined in this study, is a primary influence on ECM community structure at our study site in YNP.

Ectomycorrhizal root development in wet Alder carr forests in response to desiccation and eutrophication.

Effects of desiccation and eutrophication on ectomycorrhizal (ECM) root development in wet Alder carr forests in The Netherlands were studied. In northwestern Europe, wet Alder carr forests are found mostly in peatlands and along streams, forming an important component of wetland ecosystems. The dominant tree species in wet Alder carr forests is Alnus glutinosa (L.) Gaertn. (Black alder), which associates with ectomycorrhizal fungi. During recent decades, wet Alder carr forests in Europe have declined because of desiccation and eutrophication, particularly in The Netherlands. In the present study, the number of root tips of A. glutinosa trees was highest in an undisturbed wet Alder carr forest in a peatland area. Eutrophication in the peatland area significantly inhibited ectomycorrhizal (ECM) root development of A. glutinosa. In the eutrophied forest, ECM root tips were observed only close to A. glutinosa trees growing on hummocks. The concentrations of nitrate and potassium in soil water of the eutrophied forest were significantly higher than in the undisturbed forest, while magnesium and iron concentrations and the pH were significantly lower. The number of ECM root tips of A. glutinosa in a desiccated forest along a stream was generally lower than in an undisturbed wet Alder carr forest on waterlogged soil in the same area. The sulphate concentration in soil water in the desiccated forest was significantly higher than in the forest on waterlogged soil. ECM root development of A. glutinosa may have been negatively affected by the chemical composition of the soil water.

Effects of repeated harvesting of forest residues on the ectomycorrhizal community in a Swedish spruce forest

The use of biofuels has been proposed as one possible substitute for fossil fuels, which contribute substantially to the increase in [CO2] in the atmosphere. However, increased harvesting of forest residues for biofuel might affect the availability of base cations, P and N, as well as the development, community dynamics and function of ectomycorrhizas. This in turn might influence nutrient uptake and tree growth. In this study we investigated the effects of repeated forest residue harvesting on ectomycorrhizal species colonizing spruce roots in the humus layer of a 35‐yr‐old forest. Harvesting significantly decreased the thickness of the humus layer as well as decreasing the numbers of ectomycorrhizal root tips both per metre root length and per unit humus volume. Changes in mycorrhizal community structure were studied by ITS typing with the use of PCR–RFLP analysis. In total, 19 different ITS types were found on two different sampling occasions (autumn and spring); 11 of these were common to both samplings. Nine of the ITS types were identified to at least the genus level by comparison with RFLP patterns of identified fruiting bodies or axenic cultures. Five species, Cortinarius sp. 2, Thelephora terrestris (Ehrenb.) Fr., Lactarius theiogalus (Bull.∶Fr.) S. F. Gray s.st. Neuhoff, Tylospora fibrillosa Donk and Tö‐96‐12, occurred on over 5% of the total sampled root tips. Together these five types colonized 63% of the mycorrhizas screened. A similarity index assessment showed no shift in mycorrhizal community structure as a result of harvesting. Our findings suggest that the repeated removal of forest residues might have a strong effect on the quantity and development of ectomycorrhizal roots in the organic horizon, but little effect on the species composition of the community.

Ectomycorrhizal root growth in scots pine stands in response to manipulation of litter and humus layers

The effect on ectomycorrhizal root growth in a nitrogen-enriched planted stand of Scots pine (Pinus sylvestris L.) on podzolic sandy soil to manipulation of litter and humus layers (removal, doubling and control treatments) was examined, and compared to ectomycorrhizal root growth in an untreated naturally established Scots pine stand on nutrient-poor non-podzolic sandy soil. Half a year after manipulation of litter and humus layers in the planted stand, ingrowth-cores to a depth of 60 cm were installed in both stands. Scots pine roots were sampled four times during two growing seasons. Ectomycorrhizal roots were found at all sampled soil depths to 60 cm in all plots. Root growth and ectomycorrhizal development were greater in the naturally established stand than in all plots in the planted stand. Numbers of ectomycorrhizal root tips in the litter and humus removal plots were generally higher than in the control plots in the planted stand until May 1992. Doubling litter and humus did not significantly affect root length or the numbers of ectomycorrhizal root tips. The N dissolved , NH4 + and NO3 – concentrations and the organic matter content in the upper 5 cm of the mineral soil in the planted stand on podzolic sandy soil were generally higher and the pH significantly lower than in the naturally established stand on non-podzolic sandy soil. Root growth and ectomycorrhizal development in the secondary stand may have been negatively affected by the chemical composition of the podzolic sandy soil.

Distribution of Mycorrhiza on Competing Pines and Weeds in a Southern Pine Plantation

AbstractMycorrhiza are important in the uptake of nutrients by plants, yet little is known about the distribution and function of the diverse fungal symbionts associated with competing plant species. The objective of our research was to investigate effects of weed competition on mycorrhizal development in a slash pine (Pinus elliottii Engelm. var. elliottii) plantation in order to better understand the impact of arbuscular mycorrhizal (AM) weeds on ectomycorrhizal (EM) pines. Seedlings were planted in a typical Spodosol and samples were collected to a depth of 100 cm from weed‐free (herbicide‐treated) and weedy plots in the first and third growing seasons after outplanting. Pine roots were separated from weed roots before samples were assessed for fine root (&lt;3.0‐mm diam.) length, surface area, and mycorrhizal status. Fine root length and surface area, as well as EM surface area, of pine generally decreased with depth and increased between Years 1 and 3. In contrast, fine root length of weedy species was fairly constant during the 3‐yr period. The AM colonization of weeds followed a trend similar to that of fine root development. The depth distribution of EM pine roots and AM weedy roots exhibited complex interactions with treatment, time, and depth. There was generally greater mycorrhizal colonization of both AM on weedy species and EM on pine in the A soil horizon. Weed competition significantly affected the number of EM root tips and the distribution of EM morphotypes. Thelephora was generally the most abundant morphotype, followed by a white, rhizomorph‐producing type (White Rhiz) and Cenococcum. An exception to this pattern was found in the near‐surface soil (0–10 cm) of the weed‐free plots, where White Rhiz was the most frequent morphotype. A challenge for the future is to evaluate the functional significance of changing patterns of EM in the field.

Effects of different fertilizer treatments on ectomycorrhizal colonization potential in two Scots pine forests in Sweden

Ectomycorrhizal fungal colonization potential was studied in two low- productivity Scots pine ( Pinus sylvestris L.) forests in Sweden treated with different fertilizers. Young Pinus sylvestris seedlings were used as baits for ectomycorrhizal fungi for one growing season and the total ectomycorrhizal colonization level and frequencies of different types were recorded. One of the experimental sites had been fertilized once with 600 kg nitrogen (N) ha −1, either as ammonium nitrate or urea, 13 years previously. At this site no difference in the total number of ectomycorrhizal root tips was found between the different treatments and approximately 70% of all root tips were ectomycorrhizal. The other experimental site had been continuously fertilized for 15 years with a balanced nutrient mixture, applied either daily as a solution (IF treatment), or as solid fertilizers once a year (F treatment). The IF treatment had received 1700 kg N ha −1 and the F treatment 950 kg N ha −1 until our study was conducted. At this site a significant decrease in total ectomycorrhizal infection level was found as an effect of the fertilizer treatment. In the non-fertilized plots, 70% of all root tips were ectomycorrhizal and the corresponding figure for fertilized plots was 55%. At both sites the frequency of one of the eight classified ectomycorrhizal types decreased significantly in all fertilized plots except in the urea treatment.

Ectomycorrhizae Associated With Jarrah

Three major morphological types of ectomycorrhizae have been distinguished on roots of Eucalyptus marginara (jarrah). These were broadly classified as white, brown and black types. The variation in type of ectornycorrhizae and number of infected tips with season and depth in the soil were monitored at three forest sites. The sites had been burnt 1 , 6 and 45 years before sampling. Formation of ectomycorrhizae occurred in winter and spring. The black type was found predominantly in the soil whilst the white and brown types were associated with litter. The mean number of ectomycorrhizal root tips was highest in the 45 year unburnt and least in the 1 year unburnt site, suggesting that burning history influences their abundance.