This post was written by Ben Hand, 2012 Mono Lake Intern.
On Wednesday, August 29th, the Mono Lake Committee hosted PRBO Conservation Science’s Eastern Sierra Project leader Ken Etzel for our last Refreshments with Refreshing ‘Ologists talk of the year. Ken came to talk to us about ongoing research in the Eastern Sierra on aspen regeneration and its effect on native bird populations. As a researcher for PRBO, Ken has partnered with the Bureau of Land Management (BLM) in the Eastern Sierra in a study to look into what effects different kinds of management techniques have on aspen regeneration in the Eastern Sierra—and the ways in which these different techniques lead to different outcomes for bird density and variety in aspen groves.
Ken began his talk with a discussion of aspen trees; in particular the unique characteristics that make them both extremely important to bird populations, but also susceptible to endangerment. He first shared with us the reasons that aspen groves make such vital bird habitats: their densely packed populations of anthropoids that make abundant bird food, as well as the soft composition of aspen wood that make the trees good habitats for birds that build a nest by digging out a cavern in the tree.
However, aspen groves in the Eastern Sierra have become increasingly threatened by environmental and management factors. One of the most pressing threats to aspen health in the Sierra is fire suppression, according to Ken, since aspen stems (i.e. new plants) are quickly covered and killed by accumulating leaves and brush on the forest floor. This kind of accumulation is naturally thinned by forest fires if there is no fire suppression, which gives new aspens a chance to grow above the accumulation level every few years. Since fire suppression has been practiced in the Sierra Nevada for several decades, far fewer new aspens have been able to grow. Aspens also do poorly in shade, so natural forest fires help thin the shade canopy and therefore promote aspen growth.
PRBO has therefore developed a research partnership with the BLM to study how new land management techniques might affect aspen growth, and thereby affect bird populations that inhabit aspen groves. The BLM, in conjunction with PRBO, has chosen a series of locations around the Eastern Sierra to test differing land management techniques, which range from controlled burns to reduced grazing. PRBO is then studying how these different management techniques affect bird populations in aspen groves—concentrating in particular on how density and richness of particular aspen-dependent bird species are altered by these management practices.
Early results seem to indicate that well thought-out management techniques can have a meaningful effect on bird populations, at least in terms of density—particularly controlled burns. However, the research project is ongoing, and we look forward to hearing what kind of conclusions PRBO is able to draw from several more years of data on this project.