11- Plant growth, phenology and Soils (2)

Plant Growth, Phenology and Soils

Quote by Hope Jahren: "All the sugar you have ever eaten was made first within a leaf."

Announcements:
- Exam 1 will be released by Friday.
- Lectures included on Exam 2 cover content up to and including February 21 (Protists).
- Conservation Career Panel scheduled for Thursday in person.
- Students are required to read the lab manual before lab.
Lecture Topics:
- Plant Phenology-Science News
- Dendrochronology and tree rings
- Soils and plant nutrition

Definition: The study of periodic plant and animal life cycle events.
Flower development involves a phase change from vegetative to reproductive growth, driven by:
- Meristem identity genes: These genes promote the differentiation of plant cells.
- Environmental cues: Light and temperature act as triggers.
- Internal signals: Hormones regulate growth.
Determinacy: Flower development is determinate, concluding once the flower is formed.

Data Observation:
- Peak Bloom Dates for Cherry Trees in Washington D.C. have shifted earlier.
  - Peak blooms have been occurring earlier over the years (1921-2024).
  - Example: Peak bloom predicted in March, continuing to trend earlier.
Leaf Out Dates:
- Environmental and genetic factors in leaf-out dates are also changing due to climate change.
- Leaf out dates in major national parks have shifted:
  - Olympic National Park: 23 days earlier.
  - Grand Canyon: 11 days earlier.

Earlier blooming may lead to a decoupling of significant life cycle events, such as:
- Pollination
- Animal migration
Importance of understanding cues organisms rely on.

Heartwood and Sapwood:
- Heartwood: Older xylem layers cease to transport water and nutrients.
- Sapwood: Outer layers still actively transport materials and form tree rings as a result of secondary growth.

Significance of tree rings:
- Used for understanding past climates and environmental conditions.
- Ring width indicates growth conditions; wider rings correlate with better growth conditions (e.g., warmer, wetter climates).
Questions for consideration: What other conditions may affect tree ring growth?

Defined as:
- Unconsolidated mineral material that serves as a growth medium for plants.
- Influence of genetic and environmental factors on soil formation over time.

Climate: Influences weathering and soil breakdown.
Organisms (Biota): Contribute to soil through biological processes (eating and excreting).
Relief (Topography): Affects soil movement and weathering processes.
Parent Material: Determines soil composition and properties.
Time: Length of time soil has been weathered influences nutrient availability.

Includes:
- Rock fragments and organic material (humus).
- Effects of particle size on soil texture and moisture dynamics.
Water retention: Smaller soil particles (like clay) retain water better than larger particles (like sand).

After heavy rainfall:
- Larger pores drain faster, while smaller pores retain water due to adhesion between water and soil particles.
Sandy soils vs. clay soils:
- Sandy soils drain quickly and do not retain water well.
- Clay soils can hold more water due to smaller particle sizes.

Roots secrete acids that aid in mineral uptake:
- H+ ions displace mineral cations from clay, facilitating cation exchange.

O Horizon: Organic matter at various decomposition stages.
A Horizon: Topsoil - mix of organic and mineral material.
B Horizon: Subsoil - area of metal and nutrient accumulation.
C Horizon: Weathered parent material - least weathered section of the profile.

Low nutrient levels can alter root structures:
- Phosphorus concentrated in topsoil; nitrate moves deeper.
- Understanding nutrient mobility is crucial for plant health.

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