Not sure of getting your question, but here we go.
An ecosystem stocks matter and energy inside of living organisms.
As an ecosystem grows, the inorganic matter gets into the ecosystem and can become organic matter. This transformation is called primary production and is realised by vegetals using photosynthesis, some chimiosynthetic bacterias in deep-sea ecosystem etc ...
The productivity of an ecosystem is function of its stage. If an ecosystem is growing (like a field growing out to be a forest), the productivity would be high. A young forest is more productive than a mature one which doesn't grow anymore.
Hope it helps you :)