Explanation of Mulch Decomposition and 'Oreo Effect'

What happens here

The video explains that mulch naturally decomposes into soil over time. When a weed barrier fabric is placed underneath, the decomposing mulch forms a new layer of organic soil on top of the fabric. This creates a sandwich effect (likened to an 'Oreo' with fabric as the cream filling), where new weeds can easily establish roots in the upper soil layer, rendering the fabric ineffective. The fabric also prevents the healthy integration of organic matter from the mulch into the native soil.

Goal: Understand the underlying reason why weed barrier fabric fails over time.