2 research outputs found
Geochemical and ecological significance of soil lipids under Rhododendron ponticum stands
12 pages, 3 figures, 4 tables, 44 references.The bio-geographical significance of Rhododendron
ponticum spp. baeticum (Ericaceae) as a relict
species is well recognized. However, out of its native habitat
it is an invasive exotic considered a major threat to natural
ecosystems in areas of Atlantic Western Europe. The studies
on the impact of Rhododendron influence on soil organic
matter composition and associated ecological implications,
i.e. presence of bioactive compounds with ecological significance,
are limited. This work describes the soil lipid
assemblage in three sites under Rhododendron stands and
adjacent sites with deciduous oak (Quercus canariensis),
both in their native habitats in Southern Spain (Sierra de
Luna, Ca´diz). The results are discussed in terms of organic
matter dynamics and the presence of molecules that may be
associated with Rhododendron invasive success. The soils
are acid Xerochrepts formed on siliceous sands. Composite
soil samples were taken at two depths (0–10 cm and
10–20 cm) and soxhlet extracted with a dichloromethanemethanol
mixture (3:1). Soil lipid assemblage was studied by
GC/MS after fractionation and appropriate derivatization of
extracts. The qualitative chemical composition of soil
extractable lipids under Rhododendron is reported here for
the first time. Our results show that soil n-alkane and fatty
acid distributions are compatible with an input from plant epicuticular waxes, as well as with the occurrence of selective
preservation of long-chain fatty acids with depth. The
pattern of short-chain n-alkanes found in surface samples
indicates an anthropogenic contamination threat from
nearby industrialized areas of ‘‘Campo de Gibraltar’’. The
presence of branched iso and anteiso C15 and C17, b-hydroxy
fatty acids and the sterol brassicasterol points to high
microbial soil activity. Finally, the pentacyclic triterpenes
taraxerone and taraxerol were detected in soils with Rhododendron
but not with Quercus. These are known bioactive
plant compounds and could be related with the
effectiveness of Rhododendron as an invasive exotic species.Peer reviewe