The most likely resource found in large amounts in a forest ecosystem is biomass.

Here's why:

* Biomass refers to the total mass of living organisms in a given area. Forests are known for their high density of trees, plants, and other living organisms, contributing to a large amount of biomass.

* Other resources like timber, water, and soil are also present in forests, but their abundance may vary depending on the specific forest type and location.

While other resources are important, the sheer amount of living matter in a forest makes biomass the most abundant resource.