Sunday, June 13, 2010

Rain in a Xeric Environment

The shallow, well drained soils of Blue Jay Barrens create Xeric, meaning really dry, conditions. So how is this dry environment maintained when we have so much rain? The type of conditions found in an area are more influenced by what happens to the rain after it falls than by how much rain we get. The key to the type of plants found on a site is the amount of water that the soil can hold onto and make available for plant use. At Blue Jay Barrens, the soil can only hold a limited amount of water, so after the rain ends, the soil soon returns to its dry conditions.

Rain reaching the ground does basically one of three things; remain as free water in the soil profile, flow down through the soil to recharge the groundwater, or run across the top of the ground until it reaches a stream. Plants have an amazing ability to take in water from the soil, so if the plant is at all stressed for moisture, it will begin hydrating as soon as the rain begins to fall.

Most people have demonstrated this phenomenon in their own homes using a flower pot. When you water a potted plant, the water is absorbed by the soil in the pot. If the plant is wilted, it soon revives. If you continue to water, the water begins to come out the bottom of the pot. This is the water that would be going to the ground water in a natural system. Water too fast and the water overtops the side of the pot. This is the runoff that would hurry to a creek to create flooding. I must point out that potting soil is an artificial rooting substrate and bears no resemblance to healthy natural soil.

The first of the falling rain is absorbed by the soil. The rate at which water is absorbed is based on soil composition and structure. Structure is built through biological activity of the soil ecosystem and is in a continual state of improvement. Soil disturbance destroys structure, so the longer the soil is left undisturbed, the better the structure. Twenty-six years ago, when this field was growing its last grain crop, it took very little rain to cause massive runoff. Each year, more water enters the soil and less runs off. It took two inches of rain in 90 minutes to cause this little stream.

The runoff water quickly moves down small tributaries towards the main creek. Watersheds in a healthy condition produce runoff water that is clear. Most people don’t realize this because it is such a rare phenomenon to observe. Muddy water is a sign of erosion and if there is erosion enough to cloud the water, there is a problem in the watershed. Ninety-nine percent of this watershed is contained within Blue Jay Barrens and I love to walk out and watch the clear water flow away.

Unfortunately, I don’t control nearly enough of the watershed to keep the main creek flowing clear. The watershed feeding the tributary on the right is about 80 percent within Blue Jay Barrens, so it still looks fairly clean. The tributary on the left flows mostly from adjacent properties and looks like chocolate milk after each rain. The fast moving runoff water serves to remove debris from the stream channel, so the clean rock bottom and gravel bars can be maintained. Soon, the runoff water will be gone and the stream flow will be maintained by groundwater that flows into stream channel.


  1. Again, a very informative post. Boy, I'm learning quite a lot! Not only about the nature of things, but about how difficult it can be to successfully manage a property as you are doing. ~karen

  2. Fascinating. I enjoy coming here for my nature lessons. :)

  3. Thanks, Karen. I hope I'm being successful. Of course, if I find myself off the mark, all I have to do is redefine success.

    Hi, Lois. I'm glad you're enjoying the lessons. I'll try not to turn it into summer school.