Summary Sites should be assessed for factors that could limit plant growth or restrict the particular species. There are four principle factors that influence the survival and growth of trees and shrubs in Western Australian landscapes. The availability of moisture is a crucial element in seedling survival and further growth. Soil type and depth The critical features for soil moisture availability are depth and texture. Deep loams generally have the best seedling survival and productivity due to good moisture storage and availability, and good conditions for root growth.
Sands have good conditions for root penetration, but have poor nutrition and water holding capacity.
Clays, especially sodic or dispersive clays, prevent rapid root growth, and limit the availability of soil moisture to trees and shrubs, even though moisture storage is good. Both drought and waterlogging deaths are common on these soils. Soil depth can be assessed using a post hole auger. Poor storage capacity means trees and shrubs generally use less than the annual rainfall, unless the watertable is accessible. Rooting depth The depth of root penetration is very important to a plant's survival because it determines how much water the plant can gain access to.