Snag Fall Data from Long Term Forest Dynamics Plots in the Sierra Nevada of California through 2021

These snag (dead tree) fall data were collected as part of long term forest dynamics data. Tree fall data were collected non-systematically as text comments until 2013, after which explicit snag fall data were collected on an annual basis. This particular dataset includes data from 23 plots in old-growth mixed conifer and montane conifer forests in Sequoia-Kings Canyon and Yosemite National Parks. The plots range in size from 0.9 ha to 2.5 ha and were established from 1982 to 2001. We used demography plot data through 2021 (collected before the extensive KNP Complex wildfire burned many of the plots). Before 2021, four of the 23 plots had experienced relatively recent prescribed burns or wildfires. When established, all live trees taller than 1.37 m in height in the plots were mapped, tagged, identified to species, and measured for diameter. Crews survey plots annually to document tree mortality, to note the status of snags, and to tag and measure new (ingrowth) trees. Prior to 2013, crews did not explicitly document when snags fell. However, they noted when snags were not found or were found fallen onto the ground. In 2013, researchers combed through the annual plot notes to document the year snags fell. Beginning in 2013, field crews explicitly recorded the year when snags fell. Snags were considered fallen if their main stem, or bole, broke at a height less than or equal to 1.37 m off the ground or if they were leaning at more than a 45-degree angle. This dataset is limited to snags greater than 12.7 cm in diameter.