Table 3 Burn date, weather, soil and fuel moisture, and fire behavior during prescribed burning for the burn treatments at the Fescue site, Steens Mountain, Oregon, USA. All juniper trees (>1.5 m) were cut in July 2006 in the JAN, MAR, and APR treatments. The SEP treatment was a partial cut (one third of trees >1.5 m tall were cut), fire killing the remaining live trees. Treatment means with different lower case letters are significantly different within rows (P < 0.05).

Weather

Temperature (°C)

20 to 25.5

0 to 3

12.5 to 15.5

4.5 to 9.5

Relative humidity (%)

15 to 18

45 to 55

45 to 55

25 to 33

Wind speed (km hr⁻¹),

3 to 6, SW

Calm to 2, SW

1 to 4, NE

6 to 13, SW

Sky

Clear

Clear

Clear

Clear

Soil water content (%) ¹

Slash

14.8 ± 0.7a

32.3 ± 0.6b

33.7 ± 0.9b

32.0 ± 3.4b

Canopy

15.9 ± 0.9a

31.6 ± 0.4b

30.9 ± 0.7b

31.2 ± 0.9b

Interspace

13.5 ± 1.1a

32.2 ± 0.5b

31.7 ± 1.0b

26.9 ± 1.4b

Fuel moisture (%)

Herbaceous

13.5 ± 0.6a

15.4 ± 0.5a

73.1 ± 8.7c

45.1 ± 3.2b

Juniper needles

Suspended ²

22.4 ± 1.4c

11.5 ± 0.4b

9.6 ± 0.7ab

8.8 ± 0.5a

Ground surface ³

37.6 ± 2.5b

48.7 ± 1.0c

44.1 ± 6.3c

30.1 ± 2.7a

Canopy mat

24.7 ± 2.4a

47.0 ± 6.1b

71.0 ± 4.9d

58.0 ± 8.7c

Cut juniper roundwood ⁴

1-hour

29.0 ± 3.3c

17.2 ± 0.7b

13.1 ± 1.0a

12.1 ± 0.7a

10-hour

29.2 ± 4.6b

16.1 ± 0.5a

15.0 ± 0.5a

17.1 ± 2.8a

100-hour

30.5 ± 4.3c

23.0 ± 1.2b

17.5 ± 1.3a

20.1 ± 3.8ab

1000-hour

26.3 ± 1.0b

25.8 ± 1.1b

20.7 ± 0.9a

21.7 ± 2.0a

Shrub mortality (%)

72 %

<10 %

<10 %

35 %

Fire behavior

Flame length (m)

5 to 10

3 to 5

5 to 6

4 to 7

Burn duration (minutes)

6 to 12

3 to 4

3 to 5

7 to 13

Surface soil temp. (°C)

878 ± 48

Not detected

652 ± 81

704 ± 75

2 cm deep soil temp. (°C)

111 ± 10

Not detected

138 ± 42

178 ± 45

Plot area burned (%)

95 to 100

18 to 22

17 to 23

20 to 27

Max. juniper fuel consumed

100-hr

1-hr

1-hr

100-hr