Published: 13.12.2024.

A biologically valuable tree is a mature or old, living or dead tree that provides a home for a variety of living organisms — fungi, mosses, lichens, invertebrates, mammals, and birds.

Koks. Dzīvs ozols

 

A biologically valuable tree is any species of:

  • a growing large-sized or biologically old tree;
  • a hollow tree;
  • a snag - a standing dead tree;
  • deadwood;
  • a mature tree damaged by lightning, fire or storm.

Biodiversity

Biologically valuable trees are habitats for various organisms. These organisms may inhabit the tree temporarily, but some may spend their entire life there. Trees provide extensive opportunities for interaction between different species and ensure the long-term survival of many species. Deadwood is also an important habitat for various groups of organisms.

The competition between species (for suitable nesting sites and food resources nearby) is much more intense when the availability of suitable habitats for a species is reduced.

  • Fungi form symbiotic relationships with living trees. This unique mutually beneficial partnership is called mycorrhiza, which helps both fungi and plants absorb nutrients.
  • Living and dead wood, tree leaves, branches, roots, and bark serve as substrates for fungi to grow and develop. In Latvia, both macroscopic and microscopic fungi can be found growing on trees.
  • Fungi feed on wood and change its structure, helping it break down. This process plays an important role in nature's recycling, as decaying wood creates new habitats.
  • Slime molds also grow on trees and their parts, and were once classified as part of the fungal kingdom.
  • A slime mold can move in search of food and a suitable environment. Like fungi, slime molds reproduce via spores.
  • A lichen is a symbiotic organism formed by fungi and algae.
  • Living trees, snags, and fallen trees provide surfaces for lichens to grow and develop.
  • Lichens do not use trees as a food source; they obtain all the necessary nutrients from the environment.
  • A high diversity of lichens on a tree indicates a clean environment, as lichens are highly sensitive to air pollution.
  • Lichens play an important role in the natural cycle, serving as microhabitats and food sources for other species. 
  • Mosses use the surfaces of trees, snags, and fallen wood to grow and develop.
  • Mosses can be found on the branches and trunks of living trees (referred to as epiphytic mosses) as well as on decaying wood (known as epixylic mosses).
  • Mosses play an important role in the natural cycle by providing a microhabitat for small creatures. Several invertebrates, such as snails, also feed on mosses.
  • Mosses on trees help retain moisture by slowing down the flow of rainwater and snowmelt.
  • In Latvia, mosses are represented by three classes: hornworts, liverworts, and leafy mosses, including those found on trees.
  • A small group of moss species, typically found in long-undisturbed forests, is rarely seen in areas with intensive forestry. These mosses are used as indicators of natural forests. 
  • Invertebrates use living trees, snags, and fallen trees as habitats, feeding grounds, and shelters.
  • Many invertebrate species occupy microhabitats on trees created by other organisms (e.g., fungi, lichens, mosses, etc.).
  • Deadwood, compared to living wood, provides habitat for three times more invertebrate species.
  • Invertebrates are a vital food source for many other species.
  • In Latvia, tree-associated invertebrates are insects, mites, spiders, pseudoscorpions, millipedes, centipedes, nematodes, and woodlice.
  • Birds use trees, snags, and fallen trees for shelter, nesting, resting, feeding or as "hunting perches."
  • Birds feed on tree shoots, flowers, fruits, seeds, and other living organisms on the tree.
  • Large, old trees are the only natural structures where large birds can build nests because the weight of these nests can reach several hundred kilograms.
  • Some owl species, such as the Ural owl, can only nest in large tree cavities; if these are unavailable, they use artificial nest sites created by humans.
  • Woodpeckers need trees of suitable size to excavate cavities, which later serve as homes for other animals.
  • Small rodents live near tree root systems and under fallen trees.
  • Small mammals, such as squirrels and dormice, nest in tree cavities, while bats use tree cavities, trunk crevices, and bark gaps for shelter during the day.
  • Larger mammals use trees for feeding, marking their territory, or creating den under tree roots or fallen trees.
  • Bats use tree lines and forest edges as navigation landmarks, providing natural cover from predators and wind.
  • Mammals feed on tree flowers, shoots, fruits, bark, roots, and seeds
Projekta LIFE OsmoBaltic logo rinda

The material prepared within the LIFE Environment Programme project No. LIFE22 NAT/LT/101113698 “Baltic wide web for Osmoderma eremita: the creation of an ecological network in the Baltic region” (LIFE Osmo Baltic). The project is co-financed by the EU LIFE Environment Programme and the State Digital Development Agency of the Republic of Latvia.