Pseudotsuga menziesii invasion in native forests of Patagonia: what about mycorrhizas?

SALGADO SALOMÓN M.E., BARROETAVEÑA C, RAJCHENBERG M.

MAr del Plata

Conferencia; 2nd World Conference on Biological Invasions and Ecosystem Functioning; 2011

Exposición oral Pseudotsuga menziesii is one of the most widely planted conifers in the Patagonian Andes of Argentina, with invading characteristics widely reported. Nevertheless, little is known about the role of its obligate mycorrhizal associations in limiting or helping the establishment of invading seedlings. We studied the morphology, richness and abundance of endo- (AM), ectendo- (ECM) and ectomycorrhizae (EM) present in P. menziesii seedlings growing in 6 Nothofagus+P. menziesii matrices. One transect including Nothofagus forest without invasion, the effective recruitment area (ERA) and P. menziesii plantation was established at each site in order to sample soil. Seedlings wrenched in the ERA (from spring 2008 to summer 2010) and  trap-seedlings from a 18 months soil-bioassay were analyzed. Pseudotsuga menziesii showed effective associations with a wide range of mycorrhizal symbionts from different fungal groups such as zygomycetes, ascomycetes and basidiomycetes. Noticeably, AM mycorrhizae of Arum- and Paris- types were found in the same plant; at least 2 EM were found shared by P. menziesii and Nothofagus spp.  Dark Septate Endophytes were registered for the first time in both hosts. Pseudotsuga menziesii mycorrhizal richness and abundance varied according to site conditions, but seedlings morphometric features remained constant in all cases except their stem dry weight. Seedlings’ mycorrhization percentages were always high, suggesting a good nursery effect provided by the neighboring plantations. Pseudotsuga menziesii showed a possible alelopatic effect on Nothofagus seedlings as the latter were never found in the ERA and the low perfomance shown by seedlings in the bioassays.