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Water shortage rarely affects alpine plants directly, even in regions with very little precipitation (but see specialists). However, this does not mean that periodic soil moisture depletion is insignificant. While roots will almost always reach the required moisture in deeper soil horizons or rock crevices, top soils may dry out periodically. Why should this matter, when deep roots still reach water?
Think of other functions of soil water than just balancing leaf water losses.
1 - When the upper few centimetres of the soil profile desiccate, fine roots are unable to absorb nutrients.
Help?
Alpine plants need soil nutrients as any other plants do. These nutrients are only available in solution. If top soil desiccates this has two consequences:
- Microbial activity ceases and the mineralisation process is interrupted.
- Already mineralised nutrients are immobilized, cannot diffuse and be taken up. To some extent mycorrhiza (below ground fungal mycelia) can assist plants at moderate desiccation, but once the top 5 cm of soil are dry, plants starve, despite adequate deep moisture and good leaf turgor.
Remember:
- The key effect of low soil moisture in the alpine belt is periodic plant nutrient shortage which can restrict productivity.
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