Understanding Desert Plant Migration
August 30, 2013

Understanding Plant Movement In Dry Climates

Michael Harper for redOrbit.com - Your Universe Online

New research shows that greater plant density allows more water to seep into the ground. This means that people living in dry climates where water is a limited resource could do well to plant dense patches of vegetation to allow more water into the ground. This research also explains why plants in semiarid and dry climates often grow in tight clusters and long bands across the soil.

In his paper, which was published last month in the SIAM Journal on Applied Mathematics, lead author Jonathan A. Sherrat borrowed from a popular mathematical model to explain this banded vegetation and to add to our understanding of both how and why plants migrate along these bands.

“Vegetation patterns are a common feature in semi-arid environments, occurring in Africa, Australia and North America,” said Sherrat in a statement.

“Field studies of these ecosystems are extremely difficult because of their remoteness and physical harshness; moreover there are no laboratory replicates. Therefore mathematical modeling has the potential to be an extremely valuable tool, enabling prediction of how pattern vegetation will respond to changes in external conditions.”

Sherrat called upon the Klausmeier model to conduct his research. This model is a system of partial differential equations and is the oldest and most established way to understand why vegetation naturally lumps itself in bands in dry climates. According to the Klausmeier model, rain water only slightly infiltrates the ground as it falls from the sky. It doesn't really penetrate the dry soil until it runs downhill in the direction of a band of vegetation.

Using this hypothesis, many believe the highest levels of moisture can be found on higher bands. This, says Sherrat, is why vegetation bands naturally migrate higher uphill with every generation. As the new generation moves upward towards water, the older generation receives less water and therefore dies on the downslope edge.

Using his mathematical models, Sherrat says he can determine the amount of rain needed to move the vegetation and how well the vegetation will survive given certain ecological factors as well as how fast this migration will take place.

“My research focuses on the way in which patterns change as annual rainfall varies. In particular, I predict an abrupt shift in pattern formation as rainfall is decreased, which dramatically affects ecosystems,” says Sherrat.

“The mathematical analysis enables me to derive a formula for the minimum level of annual rainfall for which banded vegetation is viable; below this, there is a transition to complete desert.”

Since semiarid areas rely so heavily on these bands of vegetation, Sherrat says his research will help those managing the land know where the vegetation will move next and what kind of plant life will thrive in the area.

A group of German scientists have also studied the ways dry climates can benefit from plant life. According to a research team led by Klaus Becker of the University of Hohenheim in Stuttgart, planting trees in dry climates like deserts could mitigate climate change and act as a natural respirator to filter the world’s carbon emissions.