Terrestrial nitrogen cycling

Definition

Terrestrial nitrogen cycling refers to the movement and transformation of nitrogen compounds through various biological, chemical, and physical processes within terrestrial ecosystems. This cycle is essential for maintaining soil fertility, supporting plant growth, and influencing overall ecosystem health. It involves multiple stages, including nitrogen fixation, nitrification, assimilation, ammonification, and denitrification, each playing a critical role in the availability of nitrogen to plants and microorganisms.

5 Must Know Facts For Your Next Test

1. Nitrogen is a crucial nutrient for plants, and terrestrial nitrogen cycling ensures its availability in various forms for plant uptake.
2. Human activities, such as the use of fertilizers and fossil fuel combustion, have significantly altered natural nitrogen cycling, leading to environmental issues like eutrophication.
3. The majority of nitrogen fixation occurs through symbiotic relationships between legumes and certain bacteria, which convert atmospheric nitrogen into forms usable by plants.
4. Ammonification is the process where organic nitrogen from decomposed plant and animal matter is converted into ammonia, contributing to soil nutrient pools.
5. The balance of processes like nitrification and denitrification determines the overall availability of nitrogen in ecosystems, influencing plant productivity.

Review Questions

• How do human activities impact terrestrial nitrogen cycling and what are the ecological consequences of these impacts?
  • Human activities such as agricultural practices and industrial emissions significantly impact terrestrial nitrogen cycling by increasing the availability of reactive nitrogen through fertilizers and fossil fuel combustion. This can lead to excessive nutrient loading in ecosystems, resulting in problems like eutrophication in water bodies, loss of biodiversity, and alteration of soil chemistry. Additionally, these changes can disrupt the natural balance of nitrogen processes, affecting both plant health and ecosystem functioning.
• Discuss the role of microorganisms in the different stages of terrestrial nitrogen cycling and their importance for ecosystem health.
  • Microorganisms play vital roles in all stages of terrestrial nitrogen cycling. Nitrogen-fixing bacteria convert atmospheric nitrogen into ammonia, making it accessible for plants. Nitrifying bacteria then transform ammonia into nitrites and nitrates, enhancing soil fertility. Furthermore, denitrifying bacteria return nitrogen to the atmosphere, completing the cycle. The activities of these microorganisms are crucial for maintaining nutrient balance in soils, supporting plant growth, and contributing to overall ecosystem resilience.
• Evaluate the implications of disrupted terrestrial nitrogen cycling on global food security and environmental sustainability.
  • Disrupted terrestrial nitrogen cycling has serious implications for global food security and environmental sustainability. As human-induced changes lead to an imbalance in nitrogen processes, agricultural productivity may be compromised due to nutrient depletion or toxic buildup from excessive fertilizers. This can jeopardize food supply chains while also causing environmental degradation such as soil erosion and water quality issues. Ensuring sustainable practices that restore natural nitrogen cycling is essential for maintaining agricultural yields and protecting ecosystem integrity.

Related terms

Nitrogen Fixation: The process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) by certain bacteria, making nitrogen available to plants.

Nitrification: A two-step microbial process that converts ammonia (NH₃) into nitrites (NO₂⁻) and then into nitrates (NO₃⁻), which are more readily absorbed by plants.

Denitrification:

The microbial process that converts nitrates (NO₃⁻) back into nitrogen gas (N₂), returning it to the atmosphere and completing the nitrogen cycle.