Patchiness and Nutrient Cycling in Arid Lands (USA and Israel)

Project Number:

94R-15

Project Duration:

24 months

Dates:

May 1, 1994 to April 30, 1996

Institution of Principle Investigator while on this project:

Ben-Gurion University of the Negev

Investigators (most current known information)

Shachak, Moshe (PI)

Professor, Ben-Gurion University of the Negev, Mitrani Center for Desert Ecology, Institute for Desert Research, Sede Boqer 84990, ISRAEL

TEL: +972-8-659-6786, FAX: +972-8-659-6772, Email: shachak@bgumail.bgu.ac.il

Klopatek, Carole

USDA Forest Service, c/o Department of Microbiology, Arizona State University, Tempe AZ 85287-2701, USA

Lovett, Gary

Scientist, Institute of Ecosystem Studies, Box AB Route 44A, Millbrook NY 12545

TEL: +1-914-677-5343, FAX: +1-914-677-5976, Email: Lovettg@ecostudies.org

Offer, Zvi

Ben-Gurion University of the Negev, Jacob Blaustein Institute for Desert Research, Sede Boqer 84993, ISRAEL

Proposal Abstract

The Negev desert in Israel is a mosaic of macrophytic patches (consisting of shrubs and annual plants growing in a soil mound) and microphytic patches (consisting of algae, cyanobacteria, bacteria, mosses and lichens growing on a soil crust). Accumulation of soil is often a limiting resource in this ecosystem, so the loose soil mound in the macrophytic patch permits relatively high production of annual plants. To determine whether atomospheric particle deposition was responsible for soil mound formation, we measured deposition in macrophytic and microphytic patches. Our results show that fine particles, consisting mostly of mineral dust, are deposited at similar rates in macrophytic and microphytic patches. However, coarse particles, which are primarily organic material from plant detritus, are deposited at greater rates in macrophytic than in microphytic patches. The coarse particles have higher concentrations of carbon and nitrogen than the fine particles. Calculations based on the measured deposition rates suggest that a typical soil mound would require at least 100-150 years to develop. Since the presence of the soil mound is crucial for annual plant germination and growth, and the annual plants are the major source of productivity in the system, these results imply that the system will be slow to recover from disturbances that reduce the abundance of macrophytic patches, such as livestock grazing and firewood cutting.