Vegetation Types in Yosemite Valley

2. Vegetation Types in Yosemite Valley Vegetation Type Hectares % Mixed Conifer 950 49 Meadow 147 8 Riparian 208 11 Black oak 98 5 Live oak 410 21 Other 128 6

3. Yosemite Valley 1899

4. Yosemite Valley 1961

5. 1899 1961 1866 1961

6. Early to mid-1900s Tree felling for buildings, campgrounds, and bark beetle control

7. Stump creation and subsequent infection by Heterobasidion annosum

8. Ponderosa pine Incense cedar

10. Yosemite Lodge complex 1972 cabin crushed by tree with rotted roots since 1973 7 fatalities 19 serious injuries Over $1M property damage

11. Yosemite Lodge 1975 Root disease centers outlined

12. Yosemite Lodge 1997 Root disease centers outlined

14. Public safety

16. Disturbance in Yosemite Valley

17. N = 70 Mean = 1007 m2 Median = 459 m2 Range = 81 - 8300 m2 20 15 Number of Gaps 10 5 0 0 600 6000 1200 1800 2400 7200 7800 3600 4800 5400 3000 4200 6600 8400 9000 Gap size (m2)

19. Heterobasidion annosum gaps all started at a stump or stumps They may continue to expand for about 30 years

20. Sentinel Beach Gap size = 4200 m2 10 meters

21. Armillaria mellea infection center Infects all tree species Gap started at an infected black oak.

22. Ponderosa Pine killed by western pine beetle, Dendroctonus brevicomis

23. Heterobasidion annosum + Armillaria mellea gap

24. Many gaps with very little regeneration and have not closed in

25. Change in gap area 1972-1999

26. El Capitan Picnic Area 1972

27. El Capitan Picnic Area 1997

29. Yosemite Valley as it used to be?

30. Prescribed burn Yosemite Valley

31. Opportunities for restoration?

32. Pollution regulations

33. Pollen records suggest that conifers may have dominated Yosemite Valley prior to the Miwok

35. Lake Tahoe Basin

36. Lake Tahoe Basin Old Growth Historic old growth area = 26,740 ha (estimated) Historic percent old growth = 55 % (estimated) Total coniferous forest = 48,620 ha 1998 area in old growth = ~2138 ha Percent in old growth = ~4 %

37. Changes in forest composition over 150 yrs White fir and incense cedar have doubled in importance Jeffrey pine has declined by 50 %

38. Lake Tahoe fires in the 20th Century No wildland fire > 800 ha has occurred since 1908 Between 1974 and 1996, there were only 9 fires > 4 ha Effective fire suppression and the high elevation environment (i.e., short fire season) have kept large fires to a minimum

39. Stand Characteristics Lake Tahoe Stems/ha  20 cm dbh Seral 536 n=14 Old growth 324 n=17

40. Sierra San Pedro Martir, Baja, Mexico

41. Lake Tahoe Basin Lat. 39o 2000-2600 m elevation 50-100 cm annual ppt. Sierra Nevada Sierra San Pedro Martir, Baja Lat. 31o 2200-2900 m elevation Peninsular and Baja Ranges 65 cm annual ppt.

42. Tree Species Lower Montane Pinus jeffreyi, Abies concolor, Calocedrus decurrens, P. lambertiana Upper Montane Abies magnifica, A. concolor, Pinus contorta, P. monticola Subalpine Pinus albicaulis, P. contorta, P. monticola, Tsuga mertensiana, Abies magnifica,

43. Fire Return Intervals Lake Tahoe and Baja Lake Tahoe 12-55 years SSPM 13-52 years

44. Stand Characteristics Lake Tahoe and Baja Stems/ha  20 cm dbh Seral 536 n=14 Old growth 324 n=17 SSPM, Baja 134 n=16

45. Distribution of live trees by size classI = 20-50 cm; II = 50.1-100 cm; III > 100.1 cm n=5009 n=3718 n=1528 Seral Old growth SSPM 90 80 70 60 50 % stems in each DBH size class 40 30 20 10 0

46. Fir engraver beetle, Scolytus ventralis Heterobasidion annosum in fir stump

47. Bark Beetles and Conifer Hosts

48. Pathogens and Conifer Hosts

49. Mortality curves for mixed-conifer species 600 500 Seral 400 Old growth 300 SSPM 200 100 0 # dead trees 60 64 68 72 76 80 84 88 92 96 Year

50. Lake Tahoe Basin 1996