Chemical Reactions, CR 4: Driving Reactions (HS), Earth Science, Earth's System, ES 1: Materials/Energy Flow (MS), ES 4: Carbon Cycling (HS), Life Science, M&E 4: Biogeochemical Cycles (MS), M&E 5: Matter/Energy Cycles (HS), M&E 6: Biogeochemical Cycles (HS), Matter & Energy in Organisms/Ecosystems, Physical Science, S&F 1: Cells (MS), S&F 2: Cell Function (MS), Structure and Function

Field and lab conditions alter microbial enzyme and biomass dynamics

Field and lab conditions alter microbial enzyme and biomass dynamics driving decomposition of the same leaf litter

SUMMARY: This study looked at the rate of decay between litter in lab conditions and natural conditions. They used fallen leaves from dogwood trees, oak trees, maple trees, and maple-oak tree mix. Results showed quite a difference in the way the bags of litter decomposed, see Figure 2, 3 and 4. Temperature was the biggest reason why the natural litter didn’t start decomposing right away in the early stages. During the mid and late stages, it was found that nitrogen availability was necessary for microbial activity. In the lab setting, because the microbes were isolated, there was a greater need for N. In the natural setting, fungi played a role in degrading lignin and secreting enzymes that freed up available nitrogen for microbes to continue to decompose the litter; this is why you see an increase in decomposition towards the end stages in the natural litter versus the lab litter.

LESSON COMMENTS: Students should get a better sense of how organic and inorganic material is cycled during decomposition. For younger students, this would be a good lab to replicate in the classroom. If the school had access to outdoor areas to compare the two types of decomposition, that would be even better! For more advanced students, topics that can be covered include: nitrogen cycle, carbon cycle, protein synthesis, enzyme function, enzyme specificity, temperature and metabolism rates, cellular respiration, and ecosystem relationships/roles.

NGSS Standards:

Life Science: Matter and Energy in Organisms and Ecosystems Life Science: Interdependent Relationships in Ecosystems

Earth & Space Science: Earth’s Systems

Physical Science: Chemical Reactions

Rinkes, Z. L., Sinsabaugh, R. L., Moorhead, D. L., Grandy, A. S., & Weintraub, M. N. (2013). Field and lab conditions alter microbial enzyme and biomass dynamics driving decomposition of the same leaf litter. Frontiers in microbiology, 4, 260. doi:10.3389/fmicb.2013.00260