ena-STUDY-GEORGIA INSTITUTE OF TECHNOLOGY-07-11-2017-00:38:23:543-230
Phosphate addition increases tropical forest soil respiration primarily by deconstraining microbial population growth. see doi: 10.1016/j.soilbio.2018.11.026.  Soil samples were collected from four locations in the El Yunque National Forest in Puerto Rico. Short-term laboratory incubation experiments were employed to relate soil respiration to phosphorus and oxygen and also to changes in microbial community structure and activity. Sequenced metagenomes and metatranscriptomes will be submitted under this project ID.
Tropical ecosystems are an important sink for atmospheric CO2; however, plant growth is restricted by phosphorus (P) availability. Although soil microbiota facilitate organic P turnover and inorganic P mobilization, their role in coupling carbon-phosphorus processes remains poorly understood. To advance this topic, soils collected from four sites representing highly weathered tropical soils in the El Yunque National Forest, Puerto Rico were incubated with exogenous PO43- under controlled laboratory conditions. P amendment increased CO2 respiration by 14-23% relative to control incubations for soils sampled from all but the site with the greatest total and bioavailable soil P. Metatranscriptomics revealed an increase in the relative transcription of genes involved in cell growth and uptake of other nutrients in response to P amendment. A methodology to normalize gene expression by population-level relative (DNA) abundance revealed community-wide increased gene transcription with P amendment. Soil communities that responded to P additions possessed a greater relative abundance of a-glucosyl polysaccharide biosynthesis genes, suggestive of enhanced P storage. Phosphorylase genes governing the degradation of a-glucosyl polysaccharides were also more abundant, and increased in relative transcription with P amendments, indicating a shift from energy storage towards growth. Conversely, microbial communities in soils that did not respond to P addition were found to have metabolisms tuned for the phosphorolysis of labile, plant-derived substrates, such as ß-glucosyl polysaccharides. Collectively, our results provided quantitative estimates of increased soil respiration upon alleviation of P constraints and demonstrated mechanisms associated with carbon biosynthesis to enhance P storage and growth.
Tropical ecosystems are an important sink for atmospheric CO2; however, plant growth is restricted by phosphorus (P) availability. Although soil microbiota facilitate organic P turnover and inorganic P mobilization, their role in coupling carbon-phosphorus processes remains poorly understood. To advance this topic, soils collected from four sites representing highly weathered tropical soils in the El Yunque National Forest, Puerto Rico were incubated with exogenous PO43- under controlled laboratory conditions. P amendment increased CO2 respiration by 14-23% relative to control incubations for soils sampled from all but the site with the greatest total and bioavailable soil P. Metatranscriptomics revealed an increase in the relative transcription of genes involved in cell growth and uptake of other nutrients in response to P amendment. A methodology to normalize gene expression by population-level relative (DNA) abundance revealed community-wide increased gene transcription with P amendment. Soil communities that responded to P additions possessed a greater relative abundance of a-glucosyl polysaccharide biosynthesis genes, suggestive of enhanced P storage. Phosphorylase genes governing the degradation of a-glucosyl polysaccharides were also more abundant, and increased in relative transcription with P amendments, indicating a shift from energy storage towards growth. Conversely, microbial communities in soils that did not respond to P addition were found to have metabolisms tuned for the phosphorolysis of labile, plant-derived substrates, such as ß-glucosyl polysaccharides. Collectively, our results provided quantitative estimates of increased soil respiration upon alleviation of P constraints and demonstrated mechanisms associated with carbon biosynthesis to enhance P storage and growth.