Old-growth Forests: The Importance of Ancestral Ecology

An old forest is a biological treasure that has been formed over a millenary ecological succession.

September 19, 2020

FFungi Staff

FFungi Volunteer

Gabriel Orrego

Ecologist for Fungi Foundation

An old forest, or also called primary, is a biological treasure that has been formed throughout an ancient ecological succession. A state that is never static, but in a constant and chaotic homeostasis, with biodiversity, heterogeneity and structure aligned towards resilience. Furthermore, an interconnected living soil where mycorrhizal connections prevail and is a carbon reservoir of the biosphere. An old forest is an ecosystem where each leafy corner is the niche of a specific habitat for hundreds of organisms.

To evaluate and manage forests, legal definitions are used, such as that of the Food and Agriculture Organization of the United Nations (FAO), or CONAF in Chile. In general these definitions are based on the level of canopy coverage within a given area.

In Chile, for 15 years, the Law on the Recovery of the Native Forest and Forestry Promotion, Law No. 20,283, was processed in Congress, which was finally enacted in 2008. Without a doubt, a great leap that felt like a victory, but quickly, the law is limited and outdated in the face of the current urgency. The term primary forest is not mentioned. No distinction is made between an ancient forest thousands of years old and newly sprouted saplings. Our law is ecologically out of date, it does not represent the forest ecosystem, much less the ancient forest and its interconnected complexity.

Parque Katatalixar, Gabriel Orrego ©
Parque Katatalixar, Gabriel Orrego ©

Mother trees are interconnecting nodes in the soil that can transfer nutrients and information to younger trees, through the mycorrhizal fungus mycelium, a symbiotic union between fungi and plant roots. The mycorrhizal network is ubiquitous in the forest, connecting all plants to each other (Beiler, 2010).

Through the mycelium, the mature trees that emerge on the foliage, transfer a type of surplus of photosynthates (carbohydrates) towards the regeneration and the undergrowth of the shady strata, with less possibilities of light (Orrego et al., 2018). In this way, a seedling has 3 times greater survival and growth when receiving nutrients by being connected to the mycorrhizal network of the forest (teste et al, 2009).

Our cold and rainy forests sustain a condition in which more carbon is fixed than released, accumulating organic matter in the soil (Lehmann & Kleber, 2015). Nothofagus forests are particularly large carbon sinks, thanks to the fact that they form extensive networks of ectomycorrhizae. Fungi such as those of the genus Cortinarius explore long distances of soil in search of nitrogen and phosphorus for their hosts in exchange for huge volumes of photosynthates. This organic carbon is stored in distinctive, more durable subterranean tissues, which add significantly to the pools of stabilized carbon.

Old forests are a protection buffer against extreme weather events, since they prevent natural disasters such as floods and mudslides. The loss of this heritage can lead to serious local and regional negative effects, such as, for example: a water deficit. A primary forest sustains hydrological cycles, accumulating more water and regulating stream flows (Watson et al., 2018).

Primary ecosystems are the heritage of the biosphere and the future. They are ancestral relics, which cannot be restored on our time scale, their care is of local, regional and global relevance. Conserving our old forests is a priority and global security. The old forest is not an overly mature forest! It is the portrait of harmony and complexity in an ecosystem. They are the last ones left, let's take care of them.