Montana forest

Beaverhead-Deerlodge National Forest near Helena.


Most would agree that after some 280 million years, when conifer trees started showing up in our fossil record, the processes of nature have created some pretty complex and marvelous ecosystems. Their complexity of life forms and individual species adaptations to cope with other plant competition, drought, fires and pests boggles the mind. And yet, bipedal humanoids that first appeared 4 million years ago, and eventually transformed into what we call modern humans some 100,000 years ago, are threatening all of this within just the last 200 years of agri-industrial development.

By harnessing fossil fuels, humans for the first time were not limited by famine, predators, disease and isolation, and our population has been growing exponentially ever since. The new threat, aside from mutual annihilation from weapons of mass destruction, is the byproduct of our industrial success: greenhouse gases. Thus carbon dioxide, the very gas that fuels plant life and the formation of the oxygen we breathe, is considered threat No. 1, and curbing its production by absorbing and sequestering it has become an international goal, as well as a political football.

Forests and other plants within them absorb carbon dioxide as the primary building block for stems, roots, flowers and fruits. Trees are considered champions of carbon sequestration because they build woody stems that can store carbon for centuries, and thus growing more forests is touted as the fix for our atmospheric carbon dioxide problem.

However, most studies of trees and forests shows that all the carbon stored in trees eventually ends up back in the atmosphere when the trees die and the wood either burns or decomposes. Thus forest ecosystems are in the long term considered carbon neutral, releasing fixed carbon as disturbance pulses kill trees. In a functional forest such disturbances create new growing sites where young trees once again establish and may again grow into big old trees. Forest harvesting is one such disturbance, and from a carbon perspective acts very much in the same manner as other “natural” disturbances, though with a few additional nuances that change the details, but not the overall process. How a forest may best be used to sequester carbon is highly site specific, and complicated.

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For example, although trees store carbon above ground for centuries, soils can sometimes store carbon for thousands of years. Range scientists estimate that grass and forb lands sequester more carbon and for a longer time than forests. Forbs and grasslands grow new roots into the soil, that then die and become part of the soil organic pool, and they can do this at a much faster rate than trees. Some actually suggest that tree harvesting increases the rate of forest soil carbon storage by speeding up the rate by which tree root growth is converted into soil carbon, as well as promoting pulses of fine root production from the forbs and grasses that take advantage of the light in forest clearings.

Decisions about land management are complex. Scientific studies about plant-soil-animal cycles within our ecosystems are also complex, and often conflicting. Citing individual select studies to support a specific agenda is a common practice. Information is essential to making good decisions, however, the approach of selecting only the science that supports a particular agenda does not lead to better management, but rather egocentric solutions to complex problems.

Want to know more about how forests function? Please check out the 26-minute Montana State University Extension Forestry educational video at: www.youtube.com/watch?v=nvbSM7ZBmiw.

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Peter Kolb is a professor of forest ecology and management at the College of Forestry and Conservation at the University of Montana, and the Montana State University Extension Forestry Specialist.


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