Restoration of Semi-Desert Grasslands Invaded by Exotic Lovegrasses

Project Number:

01R-07

Project Duration:

30 months

Dates:

May 1, 2001 to October 31, 2003

Institution of Principle Investigator while on this project:

University of Arizona

Investigators (most current known information)

Kupfer, John A. (PI)

Assistant Professor, Department of Geography, The University of Arizona, Harvill Building, Box 2, Tucson AZ 85721

TEL: +1-520-621-1887, FAX: +1-520-621-2889, Email: kupfer@email.arizona.edu

Proposal Abstract

Definition of research problem: While the most apparent consequence of the spread and establishment of non-native species is their replacement of native species, a more serious threat may be that exotics can irreversibly alter key ecosystem processes such as nutrient cycling. In the 1930's, two nonnative lovegrasses, Lehmann lovegrass (Eragrostis lehmanniana) and Boer lovegrass (Eragrostis chloromelas), were introduced into Arizona and have since been naturalized over a larger area. Because the widespread establishment of these species runs counter to management goals such as the restoration of native grasslands, the preservation of high-quality habitat for wildlife, and the maintenance of livestock grazing values, land managers are interested in implementing restoration efforts to remove exotic lovegrasses from these ecosystems. However, while the success of many non-native eradication program is judged solely on reducing or eliminating the exotic population, the specific effects on ecosystem processes of both the exotic species itself and the eradication treatments are often imperfectly understood.

Specific objectives of the research: The goals of the research are to: 1) provide background data on differences in species composition, soil characteristics and plant tissue chemistry in areas dominated by Boer lovegrass, Lehmann lovegrass, and native grassland species; 2) document various effects of restoration treatments (burning, herbiciding, and combined burning and herbiciding) on the three community types mentioned above, and 3) implement a biogeochemical process model (Century) to examine plan soil interactions over a range of treatments and climate scenarios.

Expected contribution: The results of this study will provide an improved understanding of ecosystem processes in desert and semi-desert grasslands that should facilitate their restoration. Through a rigorous application of the scientific method, this study will clarify the relationships among exotic species presence, restoration treatments and ecosystem function by focusing not only on how exotic species respond to treatments but also how ecosystem processes, in this case soil dynamics, are affected. Such insights will be directly useful for land mangers to enhance the sustainable management of southwestern desert grassland ecosystems.

Methodology: For this research, I propose a combined field and modeling approach to examine the effects of restoration efforts in semi-desert grasslands dominated by nonnative lovegrasses at the Appleton-Whittell Research Ranch in southeastern Arizona. The field-based portion of this study will employ a randomized block design experiment to examine the effects of different treatments on plant composition and plant-soil interactions. Composition of permanent plots will be recorded prior to and at specified times following the treatments to examine the effects on lovegrass persistence. Soil properties(organic matter, macronutrient status) will be sampled throughout the course of the proposed study to examine the effects of treatments on the soil-plant continuum and to facilitate modeling of soil dynamics. Finally, productivity and chemical constitution of both native and introduced species as well interactions between the plant community and the soil will be examined by coupling results of the field study with a biogeochemical process model, Century.