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Difficulty: EasyEcological Functions, Nutrient Cycles and Ecological Succession

Which of the following statements regarding biogeochemical cycles and ecological succession are correct?

  1. Gaseous nutrient cycles have their primary reservoir pool located in the atmosphere or hydrosphere.Answer
  2. B
    Atmospheric nitrogen can be directly absorbed and assimilated by most higher green plants without prior biological or chemical fixation.
  3. Secondary succession generally proceeds much faster than primary succession because soil or organic debris is already present.Answer
  4. D
    Ecological succession initiating in open water bodies such as ponds or lakes is referred to as xerarch succession.

Answer

The correct statements are that gaseous nutrient cycles have their primary reservoir pool in the atmosphere or hydrosphere, and that secondary succession proceeds faster than primary succession because soil or organic matter is already present.
Gaseous cycles maintain their reservoir pools in gaseous or aquatic forms in the atmosphere and hydrosphere. Additionally, secondary succession advances at a faster rate than primary succession because a fertile soil bed and seed banks already exist.

Step-by-Step Solution

1
Analyze the nature of reservoir pools in gaseous biogeochemical cycles.
Gaseous cycles, including carbon and nitrogen, store their primary nutrient pool in the atmosphere or hydrosphere, enabling fast cycling.
This distinguishes gaseous cycles from sedimentary cycles whose reservoirs are in the Earth's crust.
2
Evaluate the mechanism of nitrogen assimilation by plants.
Atmospheric nitrogen gas (N2N_2) cannot be directly absorbed by green plants; it requires fixation by prokaryotes into nitrates or ammonium ions.
Plant root systems only take up inorganic nitrogen compounds soluble in soil water.
3
Compare the rates and conditions of primary versus secondary succession.
Secondary succession takes place on previously vegetated land with existing soil structure, making its progression faster than primary succession.
Primary succession requires a lengthy soil-building phase by pioneer organisms like lichens.
4
Differentiate hydrarch and xerarch ecological succession types.
Succession beginning in water bodies is hydrarch, while succession starting in dry environments is xerarch.
Hydrarch succession transitions wet environments toward mesic climax communities.

Key Concept

Classification of Biogeochemical Cycles and Dynamics of Primary vs. Secondary Ecological Succession
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Topics

Ecological Functions, Nutrient Cycles and Ecological Succession