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Esteban Suarez - One of the best experts on this subject based on the ideXlab platform.
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Earthworms reduce biotic 15 nitrogen retention in northern hardwood forests
2015Co-Authors: Holly A Ewing, Patrick J. Bohlen, Melany C Fisk, Timothy J Fahey, Peter M Groffman, Amy R Tuininga, Kathleen C Weathers, Esteban SuarezAbstract:Invasive exotic Earthworms are significantly influencing understory community composition, soil, and ecosystem processes in northern hardwood forests in North America, but their effect on the retention of nitrogen (N) has been inconclusive. We examined this in two northern hardwood forest sites in New York state, USA through a tracer study. In both spring and fall, we added tracer amounts of 15N as nitrate—to simulate atmospheric deposition—with the biologically less active tracer bromide (Br−) to areas both with and without large populations of invasive Earthworms. Total recovery of 15N was lower in earthworm-invaded plots, largely due to less retention in litter and upper soil horizons. Although the strong relationship between retention in the upper soil horizons and total 15N recovery suggests that earthworm destruction of the forest floor may be one mechanism reducing the capacity for N retention, in some cases the mineral soil in earthworm-invaded plots retained substantial N. Biotic pools, particularly litter and microbial biomass, retained significantly less 15N in earthworm-invaded plots than in their uninvaded counterparts. In plots invaded by Earthworms, negative effects of Earthworms on trees were revealed through root-uptake assays suggesting somewhat greater plant demand for ammonium in the spring and in lower 15N recovery in maple seedlings the year following tracer addition. Although similar patterns of Br− movement across treatments suggested that Earthworms had smaller effects on hydrologic tracer movement than expected, they appear to have significant effects on the biological processes that underlie N retention.
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influence of nonnative Earthworms on mycorrhizal colonization of sugar maple acer saccharum
2003Co-Authors: Beth A Lawrence, Melany C Fisk, Timothy J Fahey, Esteban SuarezAbstract:Summary • Exotic Earthworms can modify or eliminate surface organic (Oe/Oa) horizons in cold-temperate forest ecosystems and have profound effects on the forest soil environment, especially the rooting zone. • We examined the effects of earthworm colonization of northern hardwood forest soils on the abundance and morphology of mycorrhizal fungi associated with sugar maple ( Acer saccharum ). We compared mycorrhizal associations of areas of earthworm invasion with those of reference (no-worm) areas in Arnot Forest, central New York, USA. • The organic horizon in reference areas had higher mycorrhizal colonization rates and higher colonized root length than did surface layers in areas with active earthworm populations. Hyphal coils were more abundant and also formed a greater proportion of total fungal colonization in reference plots. Vesicles were more abundant and were a higher contribution to total colonization in earthworm plots, indicating a possible stress response to the presence of Earthworms. • By affecting mycorrhizal colonization and morphology, Earthworms may influence nutrient uptake capacity of dominant forest species. Our results suggest that a profound change in the mycorrhizal system will be one component of the potential ecosystem effects of invasion of new forest habitat by nonnative Earthworms.
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influence of nonnative Earthworms on mycorrhizal colonization of sugar maple acer saccharum
2003Co-Authors: Beth A Lawrence, Melany C Fisk, Timothy J Fahey, Esteban SuarezAbstract:Summary • Exotic Earthworms can modify or eliminate surface organic (Oe/Oa) horizons in cold-temperate forest ecosystems and have profound effects on the forest soil environment, especially the rooting zone. • We examined the effects of earthworm colonization of northern hardwood forest soils on the abundance and morphology of mycorrhizal fungi associated with sugar maple ( Acer saccharum ). We compared mycorrhizal associations of areas of earthworm invasion with those of reference (no-worm) areas in Arnot Forest, central New York, USA. • The organic horizon in reference areas had higher mycorrhizal colonization rates and higher colonized root length than did surface layers in areas with active earthworm populations. Hyphal coils were more abundant and also formed a greater proportion of total fungal colonization in reference plots. Vesicles were more abundant and were a higher contribution to total colonization in earthworm plots, indicating a possible stress response to the presence of Earthworms. • By affecting mycorrhizal colonization and morphology, Earthworms may influence nutrient uptake capacity of dominant forest species. Our results suggest that a profound change in the mycorrhizal system will be one component of the potential ecosystem effects of invasion of new forest habitat by nonnative Earthworms.
Roman P Lanno - One of the best experts on this subject based on the ideXlab platform.
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lethal critical body residues as measures of cd pb and zn bioavailability and toxicity in the earthwormeisenia fetida
2003Co-Authors: Jason M Conder, Roman P LannoAbstract:Earthworm heavy metal concentrations (critical body residues, CBRs) may be the most relevant measures of heavy metal bioavailability in soils and may be linkable to toxic effects in order to better assess soil ecotoxicity. However, as Earthworms possess physiological mechanisms to secrete and/or sequester absorbed metals as toxicologically inactive forms, total earthworm metal concentrations may not relate well with toxicity. The objectives of this research were to: i) develop LD50s (total earthworm metal concentration associated with 50% mortality) for Cd, Pb, and Zn; ii) evaluate the LD50 for Zn in a lethal Zn-smelter soil; iii) evaluate the lethal mixture toxicity of Cd, Pb, and Zn using earthworm metal concentrations and the toxic unit (TU) approach; and iv) evaluate total and fractionated earthworm concentrations as indicators of sublethal exposure. Earthworms (Eisenia fetida (Savigny)) were exposed to artificial soils spiked with Cd, Pb, Zn, and a Cd−Pb−Zn equitoxic mixture to estimate lethal CBRs and mixture toxicity. To evaluate the CBR developed for Zn, Earthworms were also exposed to Zn-contaminated field soils receiving three different remediation treatments. Earthworm metal concentrations were measured using a procedure devised to isolate toxicologically active metal burdens via separation into cytosolic and pellet fractions. Lethal CBRs inducing 50% mortality (LD50, 95% CI) were calculated to be 5.72 (3.54–7.91), 3.33 (2.97–3.69), and 8.19 (4.78–11.6) mmol/kg for Cd, Pb, and Zn, respectively. Zn concentrations of dead Earthworms exposed to a lethal remediated Zn-smelter soil were 3-fold above the LD50 for Zn and comparable to earthworm concentrations in lethal Zn-spiked artificial soils, despite a 14-fold difference in total soil Zn concentration between lethal field and artificial soils. An evaluation of the acute mixture toxicity of Cd, Pb, and Zn in artificial soils using the Toxic Unit (TU) approach revealed an LD50 (95% CI) of 0.99 (0.57–1.41) TU, indicating additive toxicity. Total Cd, Pb, and Zn concentrations in Earthworms were good indicators of lethal metal exposure, and enabled the calculation of LD50s for lethality. The Zn-LD50 developed in artificial soil was applicable to Earthworms exposed to remediated Zn-smelter soil, despite a 14-fold difference in total soil Zn concentrations. Mixture toxicity evaluated using LD50s from each single metal test indicated additive mixture toxicity among Cd, Pb, and Zn. Fractionation of earthworm tissues into cytosolic and pellet digesis yielded mixed results for detecting differences in exposure at the sublethal level. CBRs are useful in describing acute Cd, Pb, and Zn toxicity in Earthworms, but linking sublethal exposure to total and/or fractionated residues may be more difficult. More research on detoxification, regulation, and tissue and subcellular partitioning of heavy metals in Earthworms and other invertebrates is needed to establish the link between body residue and sublethal exposure and toxicity.
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lethal critical body residues as measures of cd pb and zn bioavailability and toxicity in the earthworm eisenia fetida
2003Co-Authors: Jason M Conder, Roman P LannoAbstract:Background. Earthworm heavy metal concentrations (critical body residues, CBRs) may be the most relevant measures of heavy metal bioavailability in soils and may be linkable to toxic effects in order to better assess soil ecotoxicity. However, as Earthworms possess physiological mechanisms to secrete and/or sequester absorbed metals as toxicologically inactive forms, total earthworm metal concentrations may not relate well with toxicity. The objectives of this research were to: i) develop LD50s (total earthworm metal concentration associated with 50% mortality) for Cd, Pb, and Zn; ii) evaluate the LD50 for Zn in a lethal Zn-smelter soil; iii) evaluate the lethal mixture toxicity of Cd, Pb, and Zn using earthworm metal concentrations and the toxic unit (TU) approach; and iv) evaluate total and fractionated earthworm concentrations as indicators of sublethal exposure. Earthworms (Eisenia fetida (Savigny)) were exposed to artificial soils spiked with Cd, Pb, Zn, and a Cd-Pb-Zn equitoxic mixture to estimate lethal CBRs and mixture toxicity. To evaluate the CBR developed for Zn, Earthworms were also exposed to Zn-contaminated field soils receiving three different remediation treatments. Earthworm metal concentrations were measured using a procedure devised to isolate toxicologically active metal burdens via separation into cytosolic and pellet fractions. Lethal CBRs inducing 50% mortality (LD50, 95% CI) were calculated to be 5.72 (3.54-7.31), 3.33 (2.97-3.69), and 8.19 (4.78-11.6) mmol/kg for Cd, Pb, and Zn, respectively. Zn concentrations of dead Earthworms exposed to a lethal remediated Zn-smelter soil were 3-fold above the LD50 for Zn and comparable to earthworm concentrations in lethal Zn-spiked artificial soils, despite a 14-fold difference in total soil Zn concentration between lethal field and artificial soils. An evaluation of the acute mixture toxicity of Cd, Pb, and Zn in artificial soils using the Toxic Unit (TU) approach revealed an LD50 (95% CI) of 0.99 (0.57-1.41) TU, indicating additive toxicity. Total Cd, Pb, and Zn concentrations in Earthworms were good indicators of lethal metal exposure, and enabled the calculation at LD50s for lethality. The Zn-LD50 developed in artificial soil was applicable to Earthworms exposed to remediated Zn-smelter soil, despite a 14-fold difference in total soil Zn concentrations. Mixture toxicity evaluated using LD50s from each single metal test indicated additive mixture toxicity among Cd, Pb, and Zn. Fractionation of earth worm tissues into cytosolic and pellet digests yielded mixed results for detecting differences in exposure at the sublethal level CBRs are useful in describing acute Cd, Pb, and Zn toxicity in Earthworms, but linking sublethal exposure to total and/or fractionated residues may be more difficult. More research on detoxification, regulation, and tissue and subcellular partitioning of heavy metals in Earthworms and other invertebrates is needed to establish the link between body residue and sublethal exposure and toxicity. Keywords: Bioavailability; Cd; critical body residues; Earthworms; metals; Pb; soil; Zn
Xiaoming Zou - One of the best experts on this subject based on the ideXlab platform.
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earthworm abundance and functional group diversity regulate plant litter decay and soil organic carbon level a global meta analysis
2020Co-Authors: Xiaoming Zou, Wei Huang, Grizelle GonzalezAbstract:Abstract A previous review of earthworm impacts on greenhouse-gas emissions concluded that Earthworms elevated soil CO2 emissions with no apparent influence on soil organic carbon (SOC), especially in laboratory incubations and in agroecosystems. This conclusion suggests that the elevated soil CO2 emissions may come from enhanced plant litter decomposition. Despite the known important role of Earthworms on regulating ecosystem processes, a quantitative analysis of the relationship between Earthworms and decomposition in global terrestrial ecosystems is still missing. Here, we present a quantitative synthesis of earthworm effects on plant litter decomposition and SOC based on 340 observations from 69 independent studies. We found a positive correlation between earthworm density and the rate of plant litter decay, and that the presence of Earthworms doubled the amount of litter mass loss on average. The presence of all three (anecic, epigeic and endogeic) earthworm functional groups was associated with higher litter mass loss than when either one or two functional groups were present. Anecic Earthworms caused the strongest effect on litter mass loss, followed by epigeic Earthworms, and there was no apparent influence by endogeic worms. Although the effect of Earthworms on SOC was not significant based on all observations, the presence of any two of the three functional groups alone or two (epigeic and endogeic, or anecic and endogeic) and three (anecic, epigeic and endogeic) functional groups together decreased SOC concentrations. Our results indicate that the effect of Earthworms on litter and SOC decay depends strongly on earthworm functional groups and diversity, and that a high diversity of earthworm functional groups accelerates litter mass loss and SOC decay. We anticipate that changes in land management practices are likely to alter ecosystem carbon cycling through alteration of earthworm abundance and diversity.
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exotic Earthworms accelerate plant litter decomposition in a puerto rican pasture and a wet forest
2002Co-Authors: Z G Liu, Xiaoming ZouAbstract:Tropical land-use changes can have profound influence on Earthworms that play important roles in regulating soil processes. Converting tropical forests to pastures often drastically increases the abundance of exotic earthworm populations such as Pontoscolex corethrurus. We initiated this study to examine the influence of exotic Earthworms on the decomposition of plant leaves and roots in a tropical pasture and a wet forest of Puerto Rico. We employed two treatments: control with natural earthworm population, and earthworm reduction using an electroshocking technique. Decomposition rates of plant leaves on the ground surface and root materials within the surface mineral soil were estimated using a litterbag technique. To understand the role that exotic Earthworms play in altering plant litter decomposition, we also compared soil CO2 evolution rates, soil microbial biomass, and physical and chemical soil properties between the controls and earthworm-reduced plots during a one-year period. Earthworm populati...
Joann K Whalen - One of the best experts on this subject based on the ideXlab platform.
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earthworm functional groups are related to denitrifier activity in riparian soils
2021Co-Authors: Chen Chen, Leanne Ejack, Martin R Chenier, Joann K WhalenAbstract:Abstract Riparian buffers, located in the transition zone between terrestrial and aquatic ecosystems, are a hotspot for nitrogen (N) removal through denitrification. Earthworms are abundant in riparian buffers and may enhance denitrification. This study investigated earthworm demographics of three earthworm functional groups (anecic, epigeic, and endogeic) and denitrifier activity in temporarily flooded and non-flooded riparian soils from April to October 2012 in southern Quebec, Canada. Nine earthworm species, mostly endogeic, were found in the temporarily flooded soil, while only six earthworm species were found in the non-flooded soil. On average, there were 11.7 times more Earthworms with 12.4 times greater biomass (P
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earthworm interactions with denitrifying bacteria are scale dependent evidence from physiological to riparian ecosystem scales
2016Co-Authors: Chen Chen, Joann K WhalenAbstract:Abstract Earthworms are implicated in denitrification, the microbially mediated reaction that results in gaseous nitrogen (N 2 O and N 2 ) loss from terrestrial ecosystems. At the physiological scale, the anaerobic earthworm gut is a favorable microsite for endemic and transient denitrifiers that produce up to 11 nmol N 2 O g −1 earthworm h −1 . Besides this direct earthworm–denitrifier interaction, the earthworm's ability to consume, fragment and mix organic residues with soil will accelerate N mineralization and create suitable conditions for opportunistic soil denitrifiers. At the drilosphere scale, earthworm biostructures (burrows, casts) and earthworm-worked soil create gradients of redox conditions and are enriched in inorganic N and soluble C substrates used by denitrifiers. Therefore, Earthworms indirectly stimulate soil N 2 O emissions by soil denitrifiers. Although these small-scale effects may imply that ecosystems with large earthworm populations are more likely to lose N through denitrification, there is scant experimental data to confirm this supposition. Evidence from simulated streams and agroecosystems suggests that Earthworms can stimulate N 2 O emissions at the ecosystem-scale, but environmental factors (temperature and moisture) may overwhelm earthworm-induced denitrification. A critical review of earthworm–denitrifier interactions in riparian buffers, a hotspot for both groups of organisms, indicated that hydrodynamics controls denitrification during flooding periods by profoundly changing soil moisture and substrate concentrations that favor denitrifier activity. Earthworm effects on denitrifiers may be detected during drier periods. Thus, earthworm–denitrifier interactions cannot be extrapolated from the physiological- and drilosphere-level to explain denitrification in riparian ecotones due to seasonal variation in hydrological processes occurring at this scale.
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trophic transfer of fatty acids from gut microbiota to the earthworm lumbricus terrestris l
2006Co-Authors: Luis Sampedro, Richard Jeannotte, Joann K WhalenAbstract:The diet of Earthworms includes soil organic matter, soil microbes and other microfauna, but the relative contribution of these dietary components to earthworm nutrition is not well known. Analysis of fatty acid (FA) profiles can reveal trophic relationships in soil food webs, leading to a better understanding of the energy and nutrient flows from microbiota to Earthworms. The objective of this study was to determine the origin of FAs assimilated by the earthworm Lumbricus terrestris L. We analysed the pattern of FAs in: (i) the bulk soil, (ii) soil in the earthworm gut, (iii) the absorptive tissue of the earthworm gut wall, and (iv) the muscular layers of the earthworm body wall. Multivariate analyses performed on the FA profiles suggest that the microbial community in the earthworm gut differs from that in bulk soil. Diverse bacterial and fungal derived FAs, which Earthworms cannot synthesize, were found in the earthworm gut wall and body wall, and in the neutral lipids (storage lipids) of the gut wall. The major compounds isolated were 20:4o6, 20:5o3 and 18:2o6, followed by the monoenoic 18:1o7 and 18:1o9c, and the saturated 18:0. The microbial FA assemblage in the gut wall resembled the gut soil more than the bulk soil, and the body wall of L. terrestris showed the same microbial derived FA pattern as the gut wall, although at reduced concentrations. We propose the existence of a specific microbial community in the earthworm gut that provides FAs to the earthworm. It appears that L. terrestris may derive more of its energy and nutrients from gut specific microbiota than from microbiota already present in the ingested soil, based on the trophic relationships revealed through FA analysis. r 2006 Elsevier Ltd. All rights reserved.
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labeling Earthworms uniformly with 13c and 15n implications for monitoring nutrient fluxes
2002Co-Authors: Joann K Whalen, H H JanzenAbstract:Stable isotopes hold promise for improving our ability to quantify energy and N released from earthworm populations through metabolic processes and mortality. However, the isotopic labels 13 C and 15 N must be incorporated uniformly into the structural and labile tissues of Earthworms to trace C and N fluxes accurately. We examined the distribution of 13 C and 15 N in the tissue and mucus of newly hatched, juvenile and adult Aporrectodea tuberculata (Eisen) fed double-labeled ( 13 C and 15 N) wheat for 4, 8, 12 and 16 weeks. After 4 weeks, earthworm tissue and mucus contained up to 1.273 at.% 13 C and 0.389 at.% 15 N. The 13 C and 15 N enrichment in hatchlings increased significantly (P , 0.05) between 4 and 16 weeks, but did not change in juvenile and adult Earthworms. The 13 C enrichment of earthworm tissue and mucus was not uniform because some of the 13 C in earthworm tissue was respired, but 15 N was uniformly distributed in earthworm tissue and mucus. We show that Earthworms can be uniformly labeled with 15 N, but not 13 C, as soon as 4 weeks after Earthworms begin feeding on double-labeled litter. Our findings indicate N turnover and excretion rates can be calculated accurately from 15 N tracer studies,
Melany C Fisk - One of the best experts on this subject based on the ideXlab platform.
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Earthworms reduce biotic 15 nitrogen retention in northern hardwood forests
2015Co-Authors: Holly A Ewing, Patrick J. Bohlen, Melany C Fisk, Timothy J Fahey, Peter M Groffman, Amy R Tuininga, Kathleen C Weathers, Esteban SuarezAbstract:Invasive exotic Earthworms are significantly influencing understory community composition, soil, and ecosystem processes in northern hardwood forests in North America, but their effect on the retention of nitrogen (N) has been inconclusive. We examined this in two northern hardwood forest sites in New York state, USA through a tracer study. In both spring and fall, we added tracer amounts of 15N as nitrate—to simulate atmospheric deposition—with the biologically less active tracer bromide (Br−) to areas both with and without large populations of invasive Earthworms. Total recovery of 15N was lower in earthworm-invaded plots, largely due to less retention in litter and upper soil horizons. Although the strong relationship between retention in the upper soil horizons and total 15N recovery suggests that earthworm destruction of the forest floor may be one mechanism reducing the capacity for N retention, in some cases the mineral soil in earthworm-invaded plots retained substantial N. Biotic pools, particularly litter and microbial biomass, retained significantly less 15N in earthworm-invaded plots than in their uninvaded counterparts. In plots invaded by Earthworms, negative effects of Earthworms on trees were revealed through root-uptake assays suggesting somewhat greater plant demand for ammonium in the spring and in lower 15N recovery in maple seedlings the year following tracer addition. Although similar patterns of Br− movement across treatments suggested that Earthworms had smaller effects on hydrologic tracer movement than expected, they appear to have significant effects on the biological processes that underlie N retention.
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exotic Earthworms alter soil microbial community composition and function
2013Co-Authors: Mark A Dempsey, Melany C Fisk, Timothy J Fahey, Joseph B Yavitt, Teri C BalserAbstract:Abstract Exotic Earthworms can profoundly alter soil carbon (C) and nitrogen (N) dynamics in northern temperate forests, but the mechanisms explaining these responses are not well understood. We compared the soil microbial community (SMC) composition (measured as PLFAs) and enzyme activity between paired earthworm-invaded and earthworm-free plots in northern hardwood forests of New York, USA. We hypothesized that differences in SMCs and enzyme activity between plots would correspond with differences in soil C content and C:N ratios. Relative abundance of several bacterial (mostly gram-positive) PLFAs was higher and that of two fungal PLFAs was lower in earthworm compared to reference plots, largely because of earthworm incorporation of the organic horizon into mineral soil. In surface mineral soil Earthworms increased arbuscular mycorrhizal fungi (AMF) and gram-positive bacterial PLFAs, and decreased fungal (mostly saprotrophic) and several bacterial (gram-negative and non-specific) PLFAs. Earthworms also increased the activities of cellulolytic relative to lignolytic enzymes in surface mineral soil, and the relationships between enzyme activities and components of the SMC suggest a substrate-mediated effect on the SMC and its metabolism of C. A highly significant relationship between components of the SMC and soil C:N also suggests that Earthworms reduce soil C:N through functional and compositional shifts in the SMC. Finally, changes in AMF abundances were linked to phosphatase activity, suggesting that Earthworms do not necessarily inhibit P-acquisition by AMF-associated plants in our study system. We conclude that the combined influence of earthworm-related changes in physical structure, accessibility and chemistry of organic matter, and relative abundance of certain groups of fungi and bacteria promote C metabolism, in particular by increasing the activities of cellulolytic vs. lignolytic enzymes.
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influence of nonnative Earthworms on mycorrhizal colonization of sugar maple acer saccharum
2003Co-Authors: Beth A Lawrence, Melany C Fisk, Timothy J Fahey, Esteban SuarezAbstract:Summary • Exotic Earthworms can modify or eliminate surface organic (Oe/Oa) horizons in cold-temperate forest ecosystems and have profound effects on the forest soil environment, especially the rooting zone. • We examined the effects of earthworm colonization of northern hardwood forest soils on the abundance and morphology of mycorrhizal fungi associated with sugar maple ( Acer saccharum ). We compared mycorrhizal associations of areas of earthworm invasion with those of reference (no-worm) areas in Arnot Forest, central New York, USA. • The organic horizon in reference areas had higher mycorrhizal colonization rates and higher colonized root length than did surface layers in areas with active earthworm populations. Hyphal coils were more abundant and also formed a greater proportion of total fungal colonization in reference plots. Vesicles were more abundant and were a higher contribution to total colonization in earthworm plots, indicating a possible stress response to the presence of Earthworms. • By affecting mycorrhizal colonization and morphology, Earthworms may influence nutrient uptake capacity of dominant forest species. Our results suggest that a profound change in the mycorrhizal system will be one component of the potential ecosystem effects of invasion of new forest habitat by nonnative Earthworms.
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influence of nonnative Earthworms on mycorrhizal colonization of sugar maple acer saccharum
2003Co-Authors: Beth A Lawrence, Melany C Fisk, Timothy J Fahey, Esteban SuarezAbstract:Summary • Exotic Earthworms can modify or eliminate surface organic (Oe/Oa) horizons in cold-temperate forest ecosystems and have profound effects on the forest soil environment, especially the rooting zone. • We examined the effects of earthworm colonization of northern hardwood forest soils on the abundance and morphology of mycorrhizal fungi associated with sugar maple ( Acer saccharum ). We compared mycorrhizal associations of areas of earthworm invasion with those of reference (no-worm) areas in Arnot Forest, central New York, USA. • The organic horizon in reference areas had higher mycorrhizal colonization rates and higher colonized root length than did surface layers in areas with active earthworm populations. Hyphal coils were more abundant and also formed a greater proportion of total fungal colonization in reference plots. Vesicles were more abundant and were a higher contribution to total colonization in earthworm plots, indicating a possible stress response to the presence of Earthworms. • By affecting mycorrhizal colonization and morphology, Earthworms may influence nutrient uptake capacity of dominant forest species. Our results suggest that a profound change in the mycorrhizal system will be one component of the potential ecosystem effects of invasion of new forest habitat by nonnative Earthworms.
