Related Experiment Video
Updated: Nov 18, 2025
08:38
Combined Size and Density Fractionation of Soils for Investigations of Organo-Mineral Interactions
Published on: February 15, 2019
15.3K
A unified theory for organic matter accumulation
Emily J Zakem1, B B Cael2, Naomi M Levine3
1Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089; zakem@usc.edu.
Summary
Organic matter accumulation in global elemental cycles is explained by a new model integrating biochemical, ecological, and environmental factors. This framework unifies previous hypotheses and predicts nonlinear responses to environmental changes.
Area of Science:
- Biogeochemistry
- Microbial Ecology
- Environmental Science
Background:
- Organic matter is crucial for global elemental cycles, but its accumulation dynamics are not fully understood.
- Existing hypotheses for organic matter accumulation include substrate recalcitrance, microbial consumption inhibition, and microbial community capabilities.
- A unified theoretical framework is needed to explain organic matter accumulation comprehensively.
Purpose of the Study:
- To develop a mechanistic model and theoretical framework explaining organic matter accumulation in natural environments.
- To integrate biochemical, ecological, and environmental factors influencing organic matter dynamics.
- To reconcile disparate hypotheses on organic matter accumulation.
Main Methods:
- Development of a mechanistic model.
- Theoretical framework construction.
- Analysis of factors influencing organic matter turnover and accumulation.
Main Results:
- The model provides a unified framework that subsumes previous hypotheses on organic matter accumulation.
- Changes in microbial communities or environment can shift organic matter from recalcitrant to depleted states.
- The model explains oceanic dissolved organic carbon profiles and links microbial activity to long-term organic matter turnover.
Conclusions:
- Organic matter accumulation is predictably governed by biochemical, ecological, and environmental factors.
- The model's threshold behavior suggests nonlinear responses of organic carbon reservoirs to environmental changes like temperature.
- This framework offers insights into past climate-carbon cycle correlations and future predictions.
More Related Videos
Related Concept Videos
01:14The Carbon Cycle
42.4K
Carbon is the basis of all organic matter on Earth, and is recycled through the ecosystem in two primary processes: one in which carbon is exchanged among living organisms, and one in which carbon is cycled over long periods of time through fossilized organic remains, weathering of rocks, and volcanic activity. Human activities, including increased agricultural practices and the burning of fossil fuels, has greatly affected the balance of the natural carbon cycle.
42.4K
02:23The Soil Ecosystem
23.8K
Plants obtain inorganic minerals and water from the soil, which acts as a natural medium for land plants. The composition and quality of soil depend not only on the chemical constituents but also on the presence of living organisms. In general, soils contain three major components:
23.8K
00:49Gravimetry: Inorganic And Organic Precipitating Agents
3.6K
In gravimetry, the precipitant is chosen carefully to obtain a pure solid that can be easily filtered. Common inorganic precipitants can be used to determine several cations and anions. In some cases, the formation of the same precipitate can be used to determine the cation and the anion. For example, the reaction of barium and chromate ions to give barium chromate is used to determine both barium and chromate. However, precipitates such as hydroxides, oxalates, and metal ammonium phosphates...
3.6K
01:22Inorganic Nitrogen Assimilation
268
Nitrogen is an essential element in biological systems, forming a crucial component of proteins, nucleic acids, and other cellular constituents. Many bacteria and archaea acquire nitrogen in the form of nitrate (NO₃⁻) or ammonia (NH₃), which are then assimilated into biomolecules through specific enzymatic pathways.Assimilatory Nitrate ReductionWhen nitrate enters the cell, it undergoes a two-step reduction process known as assimilatory nitrate reduction. Initially, the enzyme...
268
00:54What are Biogeochemical Cycles?
38.6K
The most common elements in organic molecules, carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus, are only available in the ecosystem in limited amounts. Therefore, these nutrients must be recycled through both biotic and abiotic components of the ecosystem, in processes generally called biogeochemical cycles.
38.6K
02:06Conditions on Early Earth
99.1K
Around 4 billion years ago, oceans began to condense on earth while volcanic eruptions released nitrogen, carbon dioxide, methane, ammonia, and hydrogen into the primordial atmosphere. However, organisms with the characteristics of life were not initially present on earth. Scientists have used experimentation to determine how organisms evolved that could grow, reproduce, and maintain an internal environment.
99.1K