PARENT SESSION
Contributed Oral Session 107: Soil Biota and Communities
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 524 B, Level 5, Palais des congrès de Montréal
Bacterial diversity in soil associated with ectomycorrhizal root tips of loblolly pine: effects of long-term fertilization.
Burke, David*,1, Topa, Mary2, Kretzer, Annette1, 1 State University of New York-Environmental Science and Forestry, Syracuse, New York, USA2 The Holden Arboretum, Kirtland, Ohio, USA
ABSTRACT- Fertilization is often used in forestry to compensate for losses in soil fertility; however, fertilization can alter the taxonomic diversity of soil microbial communities that regulate carbon and nutrient cycling. A greater understanding of fertilization effects on soil microbial communities is necessary for better long-term management of forest ecosystems. We investigated the effect of long-term fertilization on the diversity of soil bacteria associated with roots of 10-year-old loblolly pine (Pinus taeda L.) at a plantation in North Carolina, USA. Since bacterial communities may be affected by ectomycorrhizal (ECM) colonization of pine root tips, we also examined the effects of active and inactive ECM roots on soil bacterial diversity. Soil samples were collected to a depth of 20-cm from fertilized and non-fertilized plots and ECM root tips and adhering soil were sorted according to whether ECM tips were active or inactive (senescent). Terminal restriction fragment length polymorphisms were generated for both ectomycorrhizal fungi and soil microbial communities using environmental DNA extracts. The distribution of ectomycorrhizas was highly variable; but correspondence analyses indicated an effect of fertilization on the most commonly encountered ectomycorrhizas. Cluster analysis indicated that soil samples with active ECM tips contained a different bacterial community than soil samples with inactive ECM tips. Bacterial richness declined from a mean of 18.2 ± 1.3 operational taxonomic units (OTU) in soil with inactive ECM tips to 15.0 ±1.2 in soil with active ECM tips (P=0.075). Soil with inactive ECM tips also had significantly greater bacterial evenness than soil with active ECM tips (0.89 ±0.01 and 0.82 ±0.02 respectively, P=0.03). Fertilization significantly reduced evenness of the bacterial community but richness was unaffected. These results suggest that both fertilization and the presence of active ECM tips can affect soil bacterial communities in the root zone of mature trees.
Key words: bacterial diversity, ectomycorrhiza, fertilization, loblolly pine