The Sierra Nevada Files

Lakes can accumulate sediments and protect them from disturbance for thousands of years, making them excellent repositories of environmental information. Samples of lake sediment retrieved during coring expeditions can be analyzed to reconstruct critical characteristics of past environments, such as local vegetation communities, fire frequency, and temperature. Illustration of a coring rig installed on a raft. The casing (essentially an empty tube) is pushed into the sediment. Credit: http://www.museum.state.il.us/muslink/behind/htmls/cr_bot_pal3.html Coring lake sediment. This is an example of a sediment core. Different layers, often associated with seasonal changes, can be seen in the sediment. Photo credit: Jamie Howarth To investigate whether changes associated with global warming could be detected in sediment that has accumulated in lakes in the Sierra Nevada, Laura Streib and her colleagues collected sediment from June Lake, which is in the eastern Sierras and about 20 km south o

Fire exclusion (i.e., trying to eliminate fires from the landscape) was, for much of the 20th century, the prevailing policy in the management of forests in the Sierra Nevada. Much has been written on the effects of this management strategy on creating landscapes vulnerable to destructive fires, but there's been little research on how fire exclusion might affect the resilience of forests to other potentially damaging events. A recent paper by van Mantgem and colleagues in forests   helps to fill that gap by examining how fire may affect the ability of forests to withstand droughts. Mechanical thinning and prescribed fires are common strategies for reducing fuel load and they may also benefit the remaining trees by reducing the competition for sunlight, water, and nutrients. The authors of this paper were interested to know whether the removal of small trees by prescribed fires, alone, could confer advantages to the remaining trees, without the added benefits derived from mechanical