Final answer:
The leaf litter in forests helps maintain soil moisture by acting as an insulating layer which stores water and maintains the ecosystem's biodiversity.
Step-by-step explanation:
The moist soil layer under the leaves is a result of the forest's ability to hold and store water, which enhances the potential for life and biodiversity. The leaf litter on the forest floor acts as insulation, helping to maintain soil moisture levels even in the absence of recent rainfall. This capacity of soil to absorb and store water allows it to moderate the flow of water, reducing erosion and flood risks, and prolonging the availability of water to the local ecosystem, which includes the spotted lizard.