PARENT SESSION
Wednesday, August 9, 5:00-6:30 pm
Poster Session 18 - Forest ecology and management
Exhibit Hall, Ballroom Level, Cook Convention Center
Pastures to plantations: afforestation, soil microbes, and biogeochemistry in temperate South America.
Berthrong, Sean*,1, Jackson, Robert1, 1 Duke University, Durham, NC
ABSTRACT- Active conversion of grasslands to forests, or afforestation, has accelerated in the past several decades and represents a major global change factor. Afforested plantations provide a valuable economic resource (producing 35% of the world's wood products), and represent an important carbon sink to mitigate global climate change. However, there is considerable uncertainty about the sustainability of short rotation plantations and soil carbon storage as global afforested area rapidly expands. One of the biggest uncertainties in sustainability and soil carbon storage is the interaction of vegetation change and microbial dynamics. Combining novel molecular techniques, such as tRFLPs, qPCR, and microarrays, with ecological and biogeochemical analyses provides a new opportunity to link microbial and soil function to vegetation change. We hypothesize that the shift from grass to forest will cause a shift in the microbial community increasing the fungal biomass versus bacterial. Molecular techniques will be used to evaluate if the functional capacity of microbial community also changes. Afforestation will also potentially cause an increase in nitrogen leaching and increased soil respiration. Afforestation of temperate South American grasslands provides an excellent opportunity to study vegetation-microbe interaction. These regions are historically treeless, but 30-45 thousand ha per year was afforested through the 1990s. Our results show that afforestation of grassland soils leads to a significant shift in microbial community composition, a significant increase in ammonium and nitrate, and a net loss of soil carbon and nitrogen. These results suggest that the vegetation change has signicantly altered the microbial community and biogeochemistry. These results suggest that soils must be carefully considered in evaluating the value and sustainability of afforestation in temperate grasslands.
Key words: Afforestation, Temperate Forest, Biogeochemistry