Yosemite National Park has lost many of its large trees during the last century, possibly due to a warmer climate, a new study finds. Scientists analyzed data from the earliest records of large tree density in the park from 1932 to 1936, and compared them to the most recent records from 1988 to 1999. They found that the number of large-diameter trees - defined as those with diameters more than about 36 inches (92 cm) - in the park declined by 24 percent over that period. ‘Although this study did not investigate the causes of decline, climate change is a likely contributor to these events and should be taken into consideration,’ said USGS scientist emeritus Jan van Wagtendonk, lead author of a paper describing the results in the latest issue of the journal Forest Ecology and Management. ‘Warmer conditions increase the length of the summer dry season and decrease the snowpack that provides much of the water for the growing season,’ van Wagtendonk said. ‘A longer summer dry season can also reduce tree growth and vigor, and can reduce trees’ ability to resist insects and pathogens.’ Large trees are usually older than smaller trees, and serve […]