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Accession Number 5004265

Title Vegetation monitoring at Balcones Canyonlands National Wildlife Refuge

Project Description The objective of this project is to monitor 32 vegetation plots established at the Balcones

Canyonlands National Wildlife Refuge (BCNWR) in 1998. The BCNWR, currently at about 6,500

ha in area out of a proposed 18,600 ha reserve, was established in 1992 by buying parcels of

existing cattle ranches to provide habitat for the golden-cheeked warbler (GCW), black- capped

vireo (BCV), and other species. The GCW breeds in late-successional oak-cedar woodlands while

the BCV breeds in early-successional habitat, and the refuge recently began controlled burning as

a habitat restoration technique for the BCV. During 16-18 September 1998, we set-up and

quantified the vegetation on these 32 vegetation plots, before any burning of BCV habitat occurred,

with this initial work funded by the U.S. Geological Survey. The methods are described below,

and these plots were remeasured again using the same methods during 15-16 September 2000,

funded by the U.S. Fish and Wildlife Service (USFWS). Plots 1-16 were placed in currently

occupied BCV habitat (n=6 plots) or vireo management areas (n=10 plots) in which BCNWR plans

to restore the habitat via periodic burning. Each of these circular plots is 0.01 hectares in area

(radius=5.64 m). Plots 17-32 were placed in currently occupied GCW habitat (n=10 plots) or

transitional areas (n=6 plots) in which BCNWR plans to allow the habitat to regenerate naturally.

Each of these circular plots is 0.02 hectares in area (radius=7.98 m). The larger plot size was

used for the GCW plots because the trees and shrubs on these plots tended to be larger in

stature, warranting a larger plot size (D. Mueller-Dombois and H. Ellenberg, 1974, Aims and

Methods of Vegetation Ecology, John Wiley & Sons, pg 48). Approximate plot locations were

chosen with the assistance of the Refuge Biologist, Dr. Chuck Sexton, to sample a variety of

refuge tracts of all 4 habitat types within BCNWR. A partial randomization was then performed by

choosing a random number for the number of meters to place each plot perpendicular to each

main access road. This was done for logistical considerations to save time. Because we are

interested in testing for change over time between the BCW occupied and management areas,

and between the GCW occupied and transitional areas, this partial randomization (vs. plot

locations chosen entirely at random) is not expected to greatly affect conclusions. Once each plot

location was chosen, we marked the center of each plot with a rebar stake (1.2 m height, 0.95

cm diameter), painted orange at the top. We collected geographic positioning system (GPS)

measurements using a military-grade GPS unit, both at the nearest location on each access road,

and at the center of each plot. We used a rope of the appropriate radius to mark 8-10 locations

around the perimeter of each plot, using orange flagging tape. This flagging tape is not expected to

remain permanent and each plot perimeter will have to be reflagged during each visit. After the

perimeter was flagged, a species list was constructed for each plot, separate for herbaceous and

woody plants. William Carr, a botanist with The Nature Conservancy of Texas, was contracted for

this work. We also estimated percent cover for each species using the relevT method

(Mueller-Dombois and Ellenberg, 1974, pages 45-66), separate for herbaceous and woody plants,

and in separate categories 2 m and > 2 m in height. We used a modified Braun- Blanquet

cover-abundance scale for each species in each category: 5 (>75% cover); 4 (50-75% cover); 3

(25-50% cover); 2 (5-25% cover); 1 (<5% cover); and t (trace; a few or solitary number of

individuals with very small cover value). After the plot establishment and relevTs were finished, we

tagged up to 10 trees, saplings, or seedlings per plot in or near 12 of the GCW plots (plots 19-30)

during 20-22 September 1998, to compare growth rates between GCW transitional and occupied

areas. These trees were remeasured during 17-18 September 2000. Diamet

Keywords ashe juniper, black-capped vireo, controlled burn, dendroica chrysoparia, golden-cheeked warbler,

juniperus ashei, quercus, vegetation monitoring, vireo atricapillus,

Principal Jeff S Hatfield, USGS Patuxent Wildlife Research Center: jeff_hatfield@usgs.gov; David D

Investigators Diamond, volunteer: david_diamond@usgs.gov; William Carr, The Nature Conservancy of Texas: ;

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