Whitebark Pine (Pinus albicaulis Engelm.) Invasion of a Subalpine Meadow


Category:  Ecology
Linked Publication
Language: English
Author(s): Karen LeAnn Snethen
Description: A study was made of the invasion by whitebark pine (Pinus albicaulis Engelm.) of a subalpine meadow at Squaw Basin in the Absaroka Mountains, Wyoming. At Squaw Basin, ridges overlooking the meadow are the primary sites of tree invasion by whitebark pine. Eleven ridge plots in different stages of succession were sampled. Diameter-class distributions and ages of the pine were studied and compared with data collected for associated tree species. Size class and age studies of the trees in each of the plots indicate that whitebark pine is the first tree species to invade the ridges and that it has been successfully invading the meadow for a period of at least 250 years. Gradual Engelmann spruce and subalpine fir invasion occurs after whitebark pine is established. The successional status of whitebark pine was also determined on the north and the south slopes of a forested ridge at nearby Wind River Lake. Diameter-class distributions of the pine were compared with data collected for associated tree species. The whitebark pine populations on both slopes exhibit characteristics attributed to climax species. Evidence indicates the Clark's Nutcracker (Nucifraga columbiana) to be the major if not the only means of whitebark pine seed dispersal to the meadow ridges. The seed harvesting and caching behavior of the nutcracker was observed and compared with other studies involving nutcracker-stone pine relationships. Other possible modes of seed dispersal were also investigated. It was concluded that the nutcracker should be credited as the initiator of forest succession on the Squaw Basin meadows.