Forest Investment Account (FIA) - Forest Science Program
FIA Project Y071047

    Impact of Cattle Foraging on Understory Plant Biodiversity (Range Health) Using Long-Term Exclosures
Project lead: Sullivan, Thomas
Author: Sullivan, Thomas P.
Imprint: Vancouver, BC : University of British Columbia, 2007
Subject: Forest Investment Account (FIA), Cattle, British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
There is no information on the long-term response of understory vegetation, at various densities and fertilization regimes, in young lodgepole pine stands at replicated real-world (operational) scales. In particular, the impact of continued annual grazing by cattle on vegetation has not been addressed in any meaningful way. The issue of 'range health' can only be evaluated by relatively long-term installations measuring the responses of vegetation to grazing compared with no grazing (exclosures). Abundance and structural diversity of vegetation can act as an indicator for sustainable forest management, in this case the impact of chronic grazing by cattle, and help to determine the state of 'range health'. Because cattle graze virtually all forest ecosystems in the southern interior of B.C., we desperately need 'control sites' where there has been no grazing for a relatively long period (e.g. 10 years). Field data on understory vegetation, in and outside of exclosures, have already been collected over the period 1993 to 2003 at all installations. Thus, this proposal is designed for analysis and synthesis of these data into two manuscripts for publication in scientific journals, and extension to practitioners. This project commenced in 1993 with pre-commercial thinning of stands (12-14 years old) to 4 densities: 250, 500, 1000, and 2000 stems/ha at three replicate study areas: Summerland (MSdm), Kelowna (MSdm), and Alex Fraser Research Forest in the Cariboo (SBSdw). These thinning treatments were applied at an operational scale. Optimum nutrition fertilization of one-half the area of each stand density was initiated in 1994, and continued at 2-year intervals in 1996, 1998, 2000, and 2002 at all 3 areas. An unthinned stand, a mature stand, and an old-growth stand are included in the design at each area. Experimental design The three study areas are regional replicates (blocks). Within each replicate, there are eleven experimental units which have lodgepole pine stands treated in the following randomized block design with stems/ha indicated (T=Thinned; T+F=Thinned and Fertilized): Stand Density and Treatment 250 500 1,000 2,000 Unthinned T T+F T T+F T T+F T T+F Replicate 1 A B C D E F G H I 2 A B C D E F G H I 3 A B C D E F G H I The experimental units range in area from 4.4 to 11.3 ha at Summerland (replicate 1); from 9.5 to 12.6 ha at Kelowna (replicate 2); and from 1.5 to 4.5 ha at the Cariboo (replicate 3). Stand treatments The initial treatment was pre-commercial thinning of young stands of pine at an appropriate time to maximize growth response potential before they experience repression. Thinning was done at an operational scale at all study areas in the late summer-early fall of 1993. The objective was to establish research installations at a real-world scale to provide reasonably rigorous measurements of the various response variables. This range of stand densities, after thinning, was considered large enough to allow detection of changes in abundance and structure of understory vegetation. This broad range of densities is clearly testing extremes beyond standard operational prescriptions, but is considered sufficient to cause measurable changes in these attributes of productivity and diversity.
Contact: Sullivan, Thomas P., (604) 822-6873,


Executive Summary (88Kb)

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Updated August 16, 2010 

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