Monday, October 15, 2007

Reduction of exotic grasses in serpentine

Lolium multiflorum has become a dominant plant in portions of Jasper Ridge's serpentine prairie over the past three decades. A variety of discussions in April 2007 led to a suggested experiment in area H of the serpentine grassland (see map) to try and reduce exotic grasses. Based on the experience of Stu Weiss at Edgewood Park, and others elsewhere, there is evidence that mowing of grasses can help increase population densities of the food plants of the Bay checkerspot butterfly in the year following mowing.

Proposal: mowing at 6" height without followup raking because raking had no additional effect in Weiss' studies; mowing closer to the ground, and perhaps raking as well, would likely impact arthropods and herps. Based on Richard Hobbs' observation that late summer rain appears to trigger germination of grasses much more than forbs, and, if followed by a month of dry weather, cause a false start to the growing season, we are suggesting a watering treatment in August. The water would be applied via some type of soaker hose from a water truck (to deliver 1cm of water would take a couple of trips with the water truck).

These two treatments should be compared with controls and replicated 4 times in an area near a fire road. Each plot will be 3m x 10 or 15m, with 12 plots total, and buffers between plots.

Area H Mow Area Plant List; choose Area H work sheet. This plant list was compiled by the Herbarium crew walking through the proposed site on May 2, 2007.