Conifers possess a shallow, extensive, yet compact, network of roots. Birch intermixes with spruce in an open canopied Northern Coniferous forest. Filamitous fungi surrounding the root ball extend hairs into the needles lying at the surface, breaking them down into substances usable by the trees. Food for larger animals is sparse in such an ecosystem and they are likely found where wind throw or fire has created openings in the forest for deciduous shrubs such as birch, aspen and willow to invade colonize. Much of the northern coniferous forest of Europe and the eastern United States has suffered from the affects of acid deposition.
Acid deposition refers to the depositing of acids in both solid and and liquid form.
The most common form of acid deposition is acid rain. Much of the source of sulfur is from indutrial activities. Acid rain forms when sulfur compounds combine with water in the atmosphere to form sulfuric acid. Acid rain can severely damage the structure of pine needles making them vulnerable to invasion by other diseases and organisms. Soils in which the plants grow are acidified, mobilizing soluble metals in the soil water and proving toxic to plant roots.