Date of Award

5-1997

Degree Type

Thesis

Degree Name

Departmental Honors

Department

Plants, Soils, and Climate

Abstract

In the arid subalpine zone of the intermountain west it is common to see patchy forests interspersed with open meadows containing scattered clusters of trees referred to as tree islands. These tree islands are often composed of subalpine fir [Abies lasiocarpa (Hook) Nutt.] and Englemann spruce [Picea englemannii (Parry)]. In desert ecosystems, where lack of water is the most important factor limiting growth and nutrient dynamics, it is not unusual to see individual plants (especially in the shrub community) creating "islands of fertility", in which the plants collect nutrients by pumping them from deeper in the soil profile and redepositing those nutrients as litter, stemflow or throughfall (Charley and West 1975; Garner and Steinberger, 1989). Work by Richards and Caldwell (1987), Caldwell and Richards (1989), and Caldwell et al. (1991) has further shown that the root system of sagebrush (Artemisia sp.) communities induce hydraulic lift, a phenomenon whereby water is taken up by deep roots during the day and then released by shallow roots at night resulting in a greater amount of water available to other plants in the community. West (1991) showed that this hydraulic lift, combined with shade produced by the plant and buildup of litter underneath the plant, results in environmental conditions that are more advantageous for decomposition and nutrient release. These direct and indirect plant influences in arid environments result in a localized area around the plant that is higher in nutrient and water availability and is more conducive to plant growth and reproduction. Studies on Krummholz tree islands in the alpine zone of the Rocky Mountains in Colorado also showed that tree islands have a significant effect upon snow accumulation and redistribution (Benedict 1984) which may affect litter decomposition as well as other soil processes.

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Faculty Mentor

V. W.