Pines can therefore outcompete angiosperms in sandy soils. Sandy soils pass water through very quickly. Soils with a very high clay content, with fewer and smaller pore spaces, can hold more water, and retain it for longer periods of time. We call this property of soils their field capacity. Field capacity is the amount of water the soil can hold after being completely saturated.
Clay soils have a very high field capacity, but sandy soils have a very low field capacity.
So pines and other gymnosperms do much better in areas where there is often little or no water in the soil, in habitats that are very dry. From the standpoint of plant physiology, cold is the equivalent of dry, because getting enough water is a problem in both environments. Forest in the far North, or at higher elevations, are also dominated by gymnosperms because water in the soil may be mostly frozen most of the year. Sandy soils are also poor in nutrients. Sand passes water quickly, and the water leaches out the nutrients from the sand as it filters through.