A recently completed U.S. Forest Service study found “dramatic differences” in the density of forests today, compared to historic conditions prior to logging and fire suppression.
The graphic above illustrates increased forest density from 1929 (left) to 2008 (right). U.S. Forest Service / Courtesy graphic.
Eric Knapp, an ecologist from the Forest Service’s Pacific Southwest Research Station, led a team of scientists who looked at changes in tree and vegetation density on several historical stands in the Stanislaus-Tuolumne Experimental Forest, which encompasses about 1,700 acres near Pinecrest.
The team remeasured plots in 2008 to evaluate the effects of different logging methods over time. The plots were originally set aside in 1929 and logged that same year for experimental purposes, but haven’t been touched since.
Scientists counted trees and measured the diameters of trunks across entire stands and in neighboring unlogged plots that share the same fire history. Understory vegetation, which includes tree seedlings, shrubs and leafy plants, was quantified to determine how much has accumulated over the same amount of time.
They also collected fire-scar samples from nearby stumps and dead trees to determine the exact dates when previous forest fires swept through the area.
According to the Forest Service, the experimental plots measured in the study are among the oldest known to exist across all lands that the agency manages in California.
The study found that the previously logged plots currently contain about two-and-a-half times more trees than in 1929.
Additionally, the total density in each logged plot was nearly identical to those without a history of logging, suggesting that factors such as fire suppression may be of greater influence when it comes to forest density and severe fire danger.
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