Soru

Recent ecological research has fundamentally altered the traditional view of forests as arenas of strict competition, highlighting instead the profound cooperativity facilitated by mycorrhizal networks. These underground fungal networks colonize the roots of most tree species, creating a symbiotic web that pervades the forest floor. In this symbiosis, trees, which possess the photosynthetic capacity to produce carbohydrates, supply the fungi with essential carbon. In return, the extensive mycelial webs forage for water and soil nutrients—such as phosphorus and nitrogen—and deliver them to the host trees.

Crucially, these networks do not merely connect a single tree to its fungal partner; they link multiple trees, often of different species, into a complex system of resource exchange. Isotope tracing has demonstrated, for instance, that Douglas firs and paper birches transfer carbon back and forth depending on seasonal variations in sunlight. Furthermore, these networks serve as conduits for biochemical communication. When a tree is subjected to environmental stress, such as a drought or an aphid infestation, it can release defense-inducing chemical signals through the network, prompting neighboring trees to upregulate their own defensive enzyme production before the threat directly reaches them. Older, established trees, often termed 'hub trees,' play a particularly vital role by subsidizing shaded seedlings with surplus nutrients, thereby significantly enhancing the survival rates of the next generation.

According to the passage, the functions or benefits of mycorrhizal networks include all of the following EXCEPT which one?