Generally, lahar is not good for plants, especially in the short term. While it can contain minerals, the immediate effects of a lahar flow are overwhelmingly detrimental to plant life.
Here's a breakdown:
- Suffocation: Lahar buries existing plants, cutting off sunlight and preventing gas exchange, effectively suffocating them.
- Physical Damage: The force of the flow can uproot, break, and crush plants.
- Nutrient Imbalance: While lahar contains minerals, the initial composition may not be balanced for plant growth. The rapid deposition also prevents plants from accessing these nutrients.
- Decreased Nutrient Concentration with Depth: As the depth of lahar covering the soil increases, the availability of plant nutrients generally decreases. This necessitates higher fertilizer application rates than typically recommended as lahar depth increases.
- Altered Soil Properties: Lahar changes the soil's texture, drainage, and water-holding capacity, which can be detrimental to plant growth. The new soil structure may not be conducive to root development.
- Acidity: Some lahar deposits can be acidic, hindering plant growth.
Long-Term Considerations:
- Potential for Soil Formation: Over very long periods (decades to centuries), lahar deposits can weather and break down, eventually forming fertile soil. The volcanic minerals can contribute to soil fertility in the long run.
- Succession: Over time, plants can colonize lahar deposits through ecological succession. Pioneer species adapted to harsh conditions are the first to establish, gradually improving the soil for other plants.
In Summary:
While lahar contains minerals that could contribute to soil fertility in the very long term, the immediate effects of a lahar are harmful to plants. The deep burial, physical damage, and potential nutrient imbalances mean lahar-covered areas are typically not suitable for plant growth until significant time has passed and appropriate management strategies are implemented (like fertilization and improving soil drainage).
