Soils and flower color

Fri, 15 May 2015 08:49:03 PDT

>By observation, as well as my understanding however, clay does retain more
moisture, and for longer, than sand does, when wet and in a drying

"The curve shift from sand to clay, causing [the soil water modifier] to fall earlier in clay, but not as rapidly as in the sand, reflects the differences in the hydraulic characteristics of soils with different proportions of clay. At a given soil water content the water potential of clay is significantly lower than in sandier soils ...."…

In arid and semi-arid climates, evaporation exceeds percolation in clay soils. Deep penetration of water in clay is caused by gravity: the weight of water on top of more water. So a couple of cm of rain falling on clay doesn’t go much of anywhere unless it is followed by more rain. 

“The term “inverse texture effect” has been proposed to indicate that in arid regions, coarse-textured soils have more useable soil moisture than fine-textured soils. Coarse-textured soils hold less water per unit depth, but much of the water in arid regions is sufficiently deep to avoid evaporation, whereas in fine-textured soils most of the water from small infiltration events is easily lost to evaporation (this concept and supporting information presented by I. Noy-Meir, 1973, Desert Ecosystems: Environment and Producers. Annual Review of Ecology and Systematics 4:25-51).”

So, in a habitat where the soil is clay, a bulb would only get water from repeated “infiltration events” over a relatively short period of time. When the rain or snow melt stops, the soil dries out to the consistency of concrete. 

Bob Nold
Denver, Colorado, USA
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