TY - JOUR
T1 - Disrupting mycorrhizal mutualisms
T2 - A potential mechanism by which exotic tamarisk outcompetes native cottonwoods
AU - Meinhardt, Kelley A.
AU - Gehring, Catherine A.
PY - 2012/3
Y1 - 2012/3
N2 - The disruption of mutualisms between plants and mycorrhizal fungi is a potentially powerful mechanism by which invasives can negatively impact native species, yet our understanding of this mechanism's role in exotic species invasion is still in its infancy. Here, we provide several lines of evidence indicating that invasive tamarisk (Tamarix sp.) negatively affects native cottonwoods (Populus fremontii) by disrupting their associations with arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) fungi. At a field site in the early stages of tamarisk invasion, cottonwoods with tamarisk neighbors had reduced EM colonization and altered EM fungal community composition relative to cottonwoods with native neighbors, leading to reductions in EM propagule abundance in the soil beneath tamarisk. Similarly, AM colonization of cottonwoods was reduced with a tamarisk neighbor, but there were no significant changes in AM fungal spore communities or propagule abundance. Root colonization by nonmycorrhizal fungi, including potential pathogens, was higher in cottonwoods with tamarisk neighbors. A greenhouse experiment in which AM and EM inoculation and plant neighbor were manipulated in a fully factorial design showed that cottonwoods benefited from mycorrhizas, especially EM, in terms of shoot biomass when grown with a conspecific, but shoot biomass was similar to that of nonmycorrhizal controls when cottonwoods were grown with a tamarisk neighbor. These results are partially explained by a reduction in EM but not AM colonization of cottonwoods by a tamarisk neighbor. Tamarisk neighbors negatively affected cottonwood specific leaf area, but not chlorophyll content, in the field. To pinpoint a mechanism for these changes, we measured soil chemistry in the field and the growth response of an EM fungus (Hebeloma crustuliniforme) to saltamended media in the laboratory. Tamarisk increased both NO 3 - concentrations and electrical conductivity 2.5-fold beneath neighboring cottonwoods in the field. Salt-amended media did not affect the growth of H. crustuliniforme. Our findings demonstrate that a nonnative species, even in the early stages of invasion, can negatively affect a native species by disrupting its mycorrhizal symbioses. Some of these changes in mycorrhizal fungal communities may remain as legacy effects of invasives, even after their removal, and should be considered in management and restoration efforts.
AB - The disruption of mutualisms between plants and mycorrhizal fungi is a potentially powerful mechanism by which invasives can negatively impact native species, yet our understanding of this mechanism's role in exotic species invasion is still in its infancy. Here, we provide several lines of evidence indicating that invasive tamarisk (Tamarix sp.) negatively affects native cottonwoods (Populus fremontii) by disrupting their associations with arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) fungi. At a field site in the early stages of tamarisk invasion, cottonwoods with tamarisk neighbors had reduced EM colonization and altered EM fungal community composition relative to cottonwoods with native neighbors, leading to reductions in EM propagule abundance in the soil beneath tamarisk. Similarly, AM colonization of cottonwoods was reduced with a tamarisk neighbor, but there were no significant changes in AM fungal spore communities or propagule abundance. Root colonization by nonmycorrhizal fungi, including potential pathogens, was higher in cottonwoods with tamarisk neighbors. A greenhouse experiment in which AM and EM inoculation and plant neighbor were manipulated in a fully factorial design showed that cottonwoods benefited from mycorrhizas, especially EM, in terms of shoot biomass when grown with a conspecific, but shoot biomass was similar to that of nonmycorrhizal controls when cottonwoods were grown with a tamarisk neighbor. These results are partially explained by a reduction in EM but not AM colonization of cottonwoods by a tamarisk neighbor. Tamarisk neighbors negatively affected cottonwood specific leaf area, but not chlorophyll content, in the field. To pinpoint a mechanism for these changes, we measured soil chemistry in the field and the growth response of an EM fungus (Hebeloma crustuliniforme) to saltamended media in the laboratory. Tamarisk increased both NO 3 - concentrations and electrical conductivity 2.5-fold beneath neighboring cottonwoods in the field. Salt-amended media did not affect the growth of H. crustuliniforme. Our findings demonstrate that a nonnative species, even in the early stages of invasion, can negatively affect a native species by disrupting its mycorrhizal symbioses. Some of these changes in mycorrhizal fungal communities may remain as legacy effects of invasives, even after their removal, and should be considered in management and restoration efforts.
KW - AM and EM colonization
KW - Cottonwood
KW - Exotic species
KW - Hebeloma crustuliniforme
KW - Invasive species
KW - Mutualism disruption
KW - Mycorrhizal fungi
KW - Native
KW - Populus fremontii
KW - Tamarisk
KW - Tamarix sp
UR - http://www.scopus.com/inward/record.url?scp=84859521577&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84859521577&partnerID=8YFLogxK
U2 - 10.1890/11-1247.1
DO - 10.1890/11-1247.1
M3 - Article
C2 - 22611852
AN - SCOPUS:84859521577
SN - 1051-0761
VL - 22
SP - 532
EP - 549
JO - Ecological Applications
JF - Ecological Applications
IS - 2
ER -