Nitrogen and phosphorus additions impact arbuscular mycorrhizal abundance and molecular diversity in a tropical montane forest.
Increased nitrogen (N) depositions expected in the future endanger the diversity and stability of ecosystems primarily limited by N, but also often co-limited by other nutrients like phosphorus (P). In this context a nutrient manipulation experiment (NUMEX) was set up in a tropical montane rainforest in southern Ecuador, an area identified as biodiversity hotspot. We examined impacts of elevated N and P availability on arbuscular mycorrhizal fungi (AMF), a group of obligate biotrophic plant symbionts with an important role in soil nutrient cycles. We tested the hypothesis that increased nutrient availability will reduce AMF abundance, reduce species richness and shift the AMF community toward lineages previously shown to be favored by fertilized conditions. NUMEX was designed as a full factorial randomized block design. Soil cores were taken after 2 years of nutrient additions in plots located at 2000 m above sea level. Roots were extracted and intraradical AMF abundance determined microscopically; the AMF community was analyzed by 454-pyrosequencing targeting the large subunit rDNA. We identified 74 operational taxonomic units (OTUs) with a large proportion of Diversisporales. N additions provoked a significant decrease in intraradical abundance, whereas AMF richness was reduced significantly by N and P additions, with the strongest effect in the combined treatment (39% fewer OTUs), mainly influencing rare species. We identified a differential effect on phylogenetic groups, with Diversisporales richness mainly reduced by N additions in contrast to Glomerales highly significantly affected solely by P. Regarding AMF community structure, we observed a compositional shift when analyzing presence/absence data following P additions. In conclusion, N and P additions in this ecosystem affect AMF abundance, but especially AMF species richness; these changes might influence plant community composition and productivity and by that various ecosystem processes.
['Camenzind|Tessa|T|', 'Hempel|Stefan|S|', 'Homeier|Jürgen|J|', 'Horn|Sebastian|S|', 'Velescu|Andre|A|', 'Wilcke|Wolfgang|W|', 'Rillig|Matthias C|MC|']
D001483:Base Sequence D044822:Biodiversity D057231:Climate Change D004484:Ecuador D005544:Forecasting D008954:Models, Biological D008969:Molecular Sequence Data D038821:Mycorrhizae D009584:Nitrogen D010758:Phosphorus D018517:Plant Roots D012335:RNA, Ribosomal D017422:Sequence Analysis, DNA D012987:Soil D013045:Species Specificity
tropical montane forest NUMEX Ecuador biodiversity arbuscular mycorrhizal fungi community fertilization pyrosequencing