Decomposition and Its Processes

Decomposition

Decomposition Rates

  • Concept of Decomposition

    • There is no life without death.

    • Death provides essential nutrients to living organisms through the process of decomposition.

    • Definition of Decomposition:

      • The process by which organic matter is broken down by living organisms.

  • Measurement of Decomposition

    • A simple and effective way to measure decomposition involves the use of litter bags.

    • Example: Tulip poplar litter bags were used to assess decomposition rates.

    • Observations indicate that decomposition occurs more rapidly during the early stages of the decomposition process.

Body Clocks

  • Importance of Decomposition in Forensics

    • Decomposition plays a crucial role in forensic science.

    • The field is complex yet offers surprisingly consistent values for ammonia buildup:

    • R-squared value = 0.99

    • P-value = 0.0002

    • Context:

    • R-squared evaluates the goodness of fit for the model, ranging from 0 to 1, where:

      • 0 indicates no relationship.

      • 1 indicates a perfect relationship.

    • P-value analysis designates significance levels, with a common threshold at P < 0.05.

Decomposition Triangle

Sections 2-4 Overview

  • The decomposition triangle consists of three critical elements affecting decomposition rates:

    1. Physical Environment (Temperature & Moisture)

    2. Litter Quality

    • Quality of the organic matter influences how easily it breaks down.

    1. Decomposer Organisms

Physical Environment

  • Process Involvement:

    • Complex organic molecules are broken down into simpler chemical compounds, releasing energy in the process.

    • The rate of decomposition is heavily dependent on the physical environment, including:

    • Critical Variables:

      • Temperature: Crucial for controlling microbial and enzymatic activity.

      • Moisture: Essential for microbial growth and necessary chemical reactions during decomposition.

LTER Analysis (Long-Term Ecological Research Network)

  • The LTER network includes 28 sites with standardized data collected over extended periods.

    • Key focuses:

    • Temperature's role in controlling microbial/enzymatic activity.

    • The necessity of moisture for growth and reactions.

Decomposition Rates Across Climates

Comparative Analysis of Locations

  • Jornada Range (NM)

  • Everglades (FL)

  • McMurdo (Antarctica)

  • Rate of Decomposition Across Sites:

    • Everglades, FL: Fastest decomposition due to the combination of warm temperatures and high moisture levels which contributes to heightened microbial activity.

    • Jornada Range, NM: Moderate decomposition rate; while the temperature is high, limited moisture negatively impacts the process.

    • McMurdo, Antarctica: Slowest decomposition rate; very cold conditions yield low microbial and enzymatic activity.

  • Order of Decomposition Rates (Fast to Slow):

    • Everglades > Jornada > McMurdo

LIDET Analysis (Long-Term Decomposition Experiment Team)

  • The LIDET program involves 27 network sites with standardized data collected over a decade.

    • Species studied include:

    • Sugar Maple

    • Bluestem Roots

    • Red Pine

  • Findings:

    • Sugar Maple exhibits sensitivity to both temperature and precipitation factors.

    • Red Pine shows no significant sensitivity to temperature or precipitation.

    • Explanation:

    • Interactions among variables and the presence of local conditions complicate the results of decomposition rates.

Aerobic vs. Anaerobic Decomposition

Comparison of Efficiency

  • Oxygen Levels vs. Methane Production

    • Question posed: Which process is more efficient?

    • Microbial Specialization:

    • Aerobic Respiration

      • Requires oxygen; fully breaks down glucose into carbon dioxide and water, producing approximately 36-38 ATP per glucose molecule.

    • Anaerobic Respiration

      • Occurs without oxygen; results in partial breakdown of glucose into byproducts such as lactic acid or ethanol, yielding only about 2 ATP per glucose molecule.

Decomposition in Different Environments

Land vs. Water

  • Decomposition rates differ significantly between land and aquatic environments.

    • Why is decomposition faster in water?

    • Presence of constant moisture; essential for microbial metabolism.

    • Aquatic environments typically maintain more stable temperatures compared to terrestrial environments.

    • Organic matter is generally more accessible to decomposers such as bacteria, fungi, and invertebrates in water.

    • Nutrients released during decomposition dissolve and spread easily in water, facilitating further microbial activity.

Litter Quality

Poplar vs. Rhododendron Decomposition

  • Comparison of Decomposition Rates of Plant Litter:

    • Poplar Leaves (Decompose Faster):

    • Softer tissue, lower lignin content, fewer defensive compounds reduce resistance to microbial attack.

    • Rhododendron Leaves (Decompose Slower):

    • Tougher tissue, higher presence of lignin and tannins (defensive chemicals) increases resistance to decomposition.

    • Key Difference:

    • Leaf chemistry and toughness are the central factors influencing decomposition rates.

  • Litter Quality Definition:

    • Describes the overall quality of dead plant material; high-quality litter is easier to digest and is often rich in essential nutrients and energy.

    • Experimental Insights:

    • Roots with high carbohydrate content decompose more quickly, while those loaded with tannins and phenolics decompose at a slower rate.

Hemlock Woolly Adelgid Impact

Forest Dynamics and Decomposition Changes

  • When hemlock trees die off due to infestations of Hemlock Woolly Adelgid, they are usually replaced by hardwood species such as:

    • Red Maple

    • Birches

    • Other conifers like White Pine

  • Consequences for Decomposition:

    • Increased litterfall (needles, branches, dead trees) from the die-off can temporarily enhance decomposer activity due to a sudden influx of organic material into the ecosystem.

    • Shifting Forests and Decomposers:

    • As hemlocks give way to hardwoods, the type and quality of litter change.

    • Hardwoods generally have leaves that decompose faster than hemlock needles, which leads to shifts in decomposer communities and nutrient cycling rates.

    • Biodiversity Implications:

    • The removal of hemlocks alters habitat structure and microclimates, often diminishing populations of specialist species while favoring more generalist species.

    • Overall, biodiversity in affected forests can decline in complexity and balance.

Body Bugs and Forensics

Insect Colonization in Forensic Science

  • Forensic scientists gather information on the order of insect colonization on human remains, which can be utilized to estimate the postmortem interval (PMI).

    • Various insect species arrive at and develop on the body following a predictable sequence, allowing investigators to approximate the time since death based on insect activity.

Fossil Fuels and Decomposition

Organic Matter Persistence

  • Not all organic matter decomposes efficiently.

    • Coal Formation:

    • Coal forms from peat, which originates from bogs characterized by deep, poorly-drained, acidic conditions.

    • Anaerobic conditions here lead to extraordinarily slow decomposition rates.

Climate Change Influence on Peat Bogs

  1. Ecosystem Significance:

    • Peat bogs illustrate an ecosystem where climate shifts can significantly affect decomposition and nutrient cycling processes.

  2. Implications of Increased Temperature:

    • Rising temperatures are potentially creating conditions that shift decomposition rates and Net Primary Production (NPP), increasing the possibility of peatlands acting as carbon sources and exacerbating climate change.

    • Notably, peatlands cover approximately 3-5% of the Earth’s surface, while containing around 30% of the planet’s carbon.