TY - JOUR
T1 - Arbuscular mycorrhizal fungi in the tree seedlings of two Australian rain forests
T2 - Occurrence, colonization, and relationships with plant performance
AU - Gehring, Catherine A.
AU - Connell, Joseph H.
N1 - Funding Information:
Acknowledgements We thank J.G. Tracey, L.J. Webb, P.T. Green, and the numerous volunteers who assisted with the seedling surveys that established the long-term seedling database; the Wet Tropics Management Authority and Queensland Department of Environment and Heritage for access to field sites; P.T. Green and M.D. Lowman for help with seedling identification; B. Hewett, A. Graham, and B. Bayly for assistance in the laboratory; the CSIRO Tropical Forest Research Centre in Atherton, Queensland for generous access to laboratory and library facilities; and the Australian National University for logistical support. T.C. Theimer, R. Kobe, and the Gehring lab group provided helpful comments on the manuscript. Funding for this project was provided by NSF grants DEB95-03217 and DEB98-06310.
PY - 2006/3
Y1 - 2006/3
N2 - The roots of rain forest plants are frequently colonized by arbuscular mycorrhizal fungi (AMF) that can promote plant growth in the nutrient poor soils characteristic of these forests. However, recent studies suggest that both the occurrence of AMF on rain forest plants and the dependence of rain forest plants on AMF can be highly variable. We examined the occurrence and levels of AMF colonization of some common seedling species in a tropical and a subtropical rain forest site in Queensland, Australia. We also used a long-term database to compare the growth and mortality rates of seedling species that rarely formed AMF with those that regularly formed AMF. In both forests, more than one-third of the seedling species rarely formed AMF associations, while 40% of species consistently formed AMF in the tropical site compared to 27% in the subtropical site. Consistent patterns of AMF occurrence were observed among plant families at the two sites. Variation among seedling species in AMF occurrence or colonization was not associated with differences in seed mass among species, variation in seedling size and putative age within a species, or lack of AMF inoculum in the soil. Comparisons of four seedling species growing both in the shaded understory and in small canopy gaps revealed an increase in AMF colonization in two of the four species in gaps, suggesting that light limitation partially explains the low occurrence of AMF. Seedling survival was significantly positively associated with seed biomass but not with AMF colonization. Furthermore, seedling species that regularly formed AMF and those that did not had similar rates of growth and survival, suggesting that mycorrhizal and nonmycorrhizal strategies were equivalent in these forests. Furthermore, the high numbers of seedlings that lacked AMF and the overall low rate of seedling growth (the average seedling required 6 years to double its height) suggest that most seedlings did not receive significant indirect benefits from AMF through connection to canopy trees via a common mycorrhizal network.
AB - The roots of rain forest plants are frequently colonized by arbuscular mycorrhizal fungi (AMF) that can promote plant growth in the nutrient poor soils characteristic of these forests. However, recent studies suggest that both the occurrence of AMF on rain forest plants and the dependence of rain forest plants on AMF can be highly variable. We examined the occurrence and levels of AMF colonization of some common seedling species in a tropical and a subtropical rain forest site in Queensland, Australia. We also used a long-term database to compare the growth and mortality rates of seedling species that rarely formed AMF with those that regularly formed AMF. In both forests, more than one-third of the seedling species rarely formed AMF associations, while 40% of species consistently formed AMF in the tropical site compared to 27% in the subtropical site. Consistent patterns of AMF occurrence were observed among plant families at the two sites. Variation among seedling species in AMF occurrence or colonization was not associated with differences in seed mass among species, variation in seedling size and putative age within a species, or lack of AMF inoculum in the soil. Comparisons of four seedling species growing both in the shaded understory and in small canopy gaps revealed an increase in AMF colonization in two of the four species in gaps, suggesting that light limitation partially explains the low occurrence of AMF. Seedling survival was significantly positively associated with seed biomass but not with AMF colonization. Furthermore, seedling species that regularly formed AMF and those that did not had similar rates of growth and survival, suggesting that mycorrhizal and nonmycorrhizal strategies were equivalent in these forests. Furthermore, the high numbers of seedlings that lacked AMF and the overall low rate of seedling growth (the average seedling required 6 years to double its height) suggest that most seedlings did not receive significant indirect benefits from AMF through connection to canopy trees via a common mycorrhizal network.
KW - Arbuscular mycorrhizal fungi
KW - Canopy gap
KW - Common mycorrhizal network
KW - Rain forest
KW - Seedlings
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U2 - 10.1007/s00572-005-0018-5
DO - 10.1007/s00572-005-0018-5
M3 - Article
C2 - 16133252
AN - SCOPUS:33644628350
SN - 0940-6360
VL - 16
SP - 89
EP - 98
JO - Mycorrhiza
JF - Mycorrhiza
IS - 2
ER -