Spruce forests connected by underground fungal networks. Isotope tracing shows trees share 40% of their photosynthate with neighbors via these fungi, a wood-wide web.
The Underground Partnership
In the northern Tien Shan mountains of Kazakhstan, the forests of Kolsai Lakes National Park are dominated by a single conifer species: the Schrenk's spruce, Picea schrenkiana. These trees, which grow on moist, north-facing slopes between 1,500 and 2,700 meters, participate in a common and ancient symbiosis. Their roots are interwoven with vast networks of mycorrhizal fungi, forming a biological marketplace beneath the forest floor.
This relationship is a mutualism. The spruce trees, through photosynthesis, produce carbon-based sugars and transfer a portion of them to the fungi. In return, the web-like body of the fungus, called a mycelium, extends far beyond the reach of the tree's own roots. These thin fungal threads, or hyphae, are exceptionally efficient at absorbing water and essential soil nutrients like phosphorus and nitrogen, which they transport back to the tree. This exchange allows the spruce to thrive in the montane environment. The fungi and trees are so interconnected that the forest effectively operates as a single, complex organism.
The Wood-Wide Web in Action
The mycelial connections link a fungus to a single tree. They form a sprawling, interlinked system known as a common mycorrhizal network (CMN) that connects many trees, including older "mother trees" and younger saplings. To understand how resources move through this "wood-wide web," scientists use a technique called isotope tracing.
In field experiments, a specific tree is exposed to carbon dioxide containing a rare, heavy isotope of carbon, such as Carbon-13 or Carbon-14. This labeled carbon is then incorporated into the sugars the tree produces. By testing neighboring trees and the fungal network itself, researchers can precisely track where that labeled carbon travels. Landmark studies using this method revealed that a significant amount of a tree's synthesized carbon is actively transferred below ground. The research on the 40% figure shows that trees shunt a substantial portion of their energy to their neighbors through these fungal conduits. This resource sharing can support the growth and survival of young seedlings that are shaded by the canopy of larger, established trees. The network also allows trees to send chemical defense signals, providing an early warning system against insect attacks.
💡Fun Facts
Mycorrhizal fungi are ancient; their symbiotic relationship with plants is estimated to have begun over 400 million years ago, facilitating the movement of plants from water to land.
A single mature tree in a forest can be connected to dozens of other trees through its associated fungal network, which can span hundreds of meters.
The total length of fungal mycelium in the top 10 centimeters of forest soil is typically between 100 and 500 kilometers per square meter.
Globally, mycorrhizal networks are responsible for drawing down an estimated 13 billion tons of CO2 from the atmosphere into the soil each year.
The park is accessible year-round, but weather in the Tien Shan mountains can be unpredictable. Trails may be closed or hazardous due to snow in winter.
Admission
An entrance fee is required for the national park, typically paid at a gate near the village of Saty. Prices are posted at the entrance.
Accessibility
The terrain around the lakes is mountainous with unpaved, often steep and uneven trails. It is not accessible for wheelchairs. Sturdy hiking footwear is recommended.