Article Figures & Data
Figures
- Figure 1.
Diagram of a 500-kV electric transmission line, showing wire and border zones. A combination of a low-growing forb–grass–shrub cover type develops in wire zones, and a tall shrub cover type occurs in border zones. Adjacent to the border zone is mature forest.
Tables
- Table 1.
Number of target trees/ha (≥ 0.3 m [1 ft] tall) in wire zones and border zones of ten treatment units at the Green Lane Research and Demonstration Area in 2003 and 2004 (number of target trees per acre are given in parentheses). A second handcut unit (HC-1) was established in 2001 beneath the tower from a portion of a mowing unit (M-2); this portion could not be mowed because of rocky terrain.
Treatment unit (replicate) Wire zone Border zone 2003 2004 2003 2004 Mechanical units Handcut HC-1 4,199 (1,700) 3,211 (1,300) 1,482 (600) 3,952 (1,600) HC-2 3,582 (1,450) 3,705 (1,500) 4,940 (2,000) 2,964 (1,200) Average 3,891 (1,575) 3,458 (1,400) 3,211 (1,300) 3,458 (1,400) Mowing M-1 988 (400) 1,235 (500) 1,729 (700) 741 (300) M-2 2,347 (950) 3,829 (1,550) 494 (200) 741 (300) Average 1,668 (675) 2,532 (1,025) 1,112 (450) 741 (300) Herbicidal units Mowing plus herbicide MH-1 371 (150) 371 (150) 247 (100) 1,235 (500) MH-2 1,153 (467) 1,235 (500) 2,638 (1,068) 3,293 (1,333) Average 762 (309) 803 (325) 1,443 (584) 2,264 (917) Foliage spray F-1 988 (400) 865 (350) 1,729 (700) 3,458 (1,400) F-2 371 (150) 618 (250) 988 (400) 494 (200) Average 680 (275) 742 (300) 1,359 (550) 1,976 (800) Stem–foliage spray SF-1 247 (100) 412 (167) 494 (200) 825 (334) SF-2 988 (400) 865 (350) 247 (100) 1,235 (500) Average 618 (250) 639 (259) 371 (150) 1,030 (417) All units Average 1,524 (617) 1,635 (662) 1,499 (607) 1,894 (767) Mechanical units combined Average 2,780 (1,125) 2,995 (1,213) 2,162 (875) 2,100 (850) Herbicidal units combined Average 687 (278) 728 (295) 1,058 (428) 1,757 (711) - Table 2.
Cover type in wire zones and border zones of ten treatment units at the Green Lane Research and Demonstration Area in June 2003 and June 2004. F = forb, G = grass, S = shrub, and T = tree. The symbol “>” implies a greater proportion of this cover type; the symbol “=” implies relatively similar amounts of this cover type.
Treatment/replicate unit Cover type Wire zone Border zone 2003 2004 2003 2004 Mechanical units Handcut HC-1 S>F>T S>T S>t S > F HC-2 S>T=F S>T=F S=F S=F Mowing M-1 F>S S>F S>F>T S>F>G M-2 S=F F>S>G S>F S>F Herbicidal units Mowing plus herbicide MH-1 G>F>S G>S=F S=F S>F=G MH-2 F=G>S S>G>F S>F S>F>G Foliage spray F-1 F>G>S F>G>S S>G>F S=G=F F-2 S>F>G F=G>S S>F S>F Stem–foliage spray SF-1 F>S F>S S>F S>F SF-2 F>G>S S=F F>S>G S=F
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