in the area of Dinosaur National Monument, Colorado/Utah

Piñon-juniper covers 40 x 106 ha in Western U.S.

Expansion over past 100-150 years[1,2]

• 33% increase from 1966-1995[3]

• 150-625% increase since 1860[4]

Potential drivers[5]

Fire exclusion

Over-grazing

Climate change

Expansion in the Shoshone Mountains, Nevada [4]

Dynamics & drivers spatially variable

Reference conditions lacking in many areas of Western U.S.[5]

In contrast

Minimal expansion on Uncompahgre Plateau in western CO[6]

Severe drought in Southwest 2002-2003 resulted in mortality >90%[7]

Expansion actually recovery from Euro-American land uses[8]

Still, piñon-juniper is the subject of many supposed restoration treatments

“Increasingly complex interactions between fire and invasive species have

begun to present unprecedented

complications for park managers, leading to the need for a comprehensive

assessment of current landscape condition, analysis of historical

patterns of change, and an improved understanding of the past and future role of fire in Dinosaur’s unique

environment.”

Spatial extent of piñon-juniper in late 19th/early 20th century Dinosaur National Monument (DINO) unknown

Early aerial & landscape photographs not early or comprehensive enough

General Land Office (GLO) survey records provide necessary spatial and temporal scales[9]

GLO survey records

Detailed and comprehensive

Focus on line data, not point data (bearing trees)

General description of dominant over- and understory species at beginning/end of line

Entry and exit points of forested and non-forested areas to nearest link (.2 m)

Data entered into VBA entry form → MS Access database

Diagram from geology.isu.edu

Two study areas

Focus on DINO (52,936 ha)

Larger area outside DINO (245,027 ha)

Rugged terrain inside DINO not always surveyed

Compare trends inside DINO to those of the adjacent area

Hypotheses

H1A) Piñon-juniper woodlands expanded in range over the past 100 years into the adjoining

sagebrush shrublands.

H1B) Piñon-juniper expansion occurred proximal to the piñon-juniper woodland-sagebrush

shrubland ecotone (i.e., within 200 m of the ecotone).

H2A) The recent fire rotation in piñon-juniper woodlands is longer, due to fire exclusion, than the

historical rotation.

H2B) The recent fire rotation in sagebrush is longer, due to fire exclusion, than the historical

rotation.

H3A) Piñon-juniper expansion was influenced by biophysical environment, evidenced by sites that

were either conducive or resistant to tree establishment.

H3B) Piñon-juniper contraction was strongly correlated with the occurrence of fire.

H1A - Woodland expansion

Historical and modern (NPS and ReGAP) datasets intersected

H1B - Woodland expansion relative to ecotones

Distance measured from piñon-juniper expansions to historical piñon-juniper-sagebrush ecotones

One-tailed t-test (greater than 200 m)

H2A/H2B - Fire in piñon-juniper and sagebrush

Modern fire rotations (FR) calculated from GIS dataset compiled from multiple sources (1981-2000)

Compared to commonly reported measures of historical fire rotation

H3A - Piñon-juniper expansion and the biophysical environment

Chi-square tests to compare distribution of settings selected by expansion against distribution of settings found in study area

Elevation, slope, aspect, topographic position, soils

H3B - Piñon-juniper contraction and fire

% of piñon-juniper that converted to other ecosystems from fire from 1981-2000

Extrapolate to determine if fire could explain contraction since 1910

H1A - Woodland expansion

GLO/ReGAP intersection showed contraction of piñon-juniper (& montane shrubland), expansion of grassland/sagebrush – H1A rejected

H1A - Woodland expansion

GLO/NPS intersection showed net contraction of piñon-juniper, net expansion of sagebrush – H1A rejected

H1B - Woodland expansion relative to ecotones

Expansion not confined to 200 m (M = 339.40, SD = 712.60) – H1B rejected, though much expansion did occur close to ecotone

Expansion occurred over much of study area at a fine grain

Large patches north of Yampa River, northwestern and southeastern regions

H2A/2B inside DINO - Fire in piñon-juniper and sagebrush

Recent FR in piñon-juniper of 188 years < 400-600 years – H2A rejected

Recent FR in Wyoming/Basin big sagebrush of 53 years < 2,500-5,000 years – H2B rejected

Recent FR in mountain big sagebrush of 166 years < 458-729 years – H2B rejected

Most fire in sagebrush from resource-management burning, natural FR also short

Vegetation Types

Total line length or area

Human-caused: resource management

Human-caused: unspecified

Human-caused: Total

Natural: lightning

Unknown cause Total fire

INSIDE DINOSAUR Piñon-juniper 329.79 km

9.21 km

27.4%

687 years

0.02 km

0.1%

9.23 km

27.5%

686 years

24.39 km

72.6%

259 years

0.00 km

0.0%

33.62 km

100.0%

188 years

Wyoming/Basin big sagebrush

43.15 km

9.35 km

59.4%

88 years

0.82 km

5.2%

10.17 km

64.7%

82 years

5.57 km

35.4%

149 years

0.00 km

0.0%

15.74 km

100.0%

53 years

Mountain big sagebrush 2.67 km

0.19 km

61.3%

270 years

0.00 km

0.0%

0.19 km

61.3%

270 years

0.12 km

38.7%

427 years

0.00 km

0.0%

0.31 km

100.0%

166 years Montane shrubland 2.29 km

0.17 km

54.8%

269 years

0.00 km

0.0%

0.17 km

54.8%

269 years

0.14 km

45.2%

327 years

0.00 km

0.0%

0.31 km

100.0%

148 years

Whole AOI 421.16 km

28.45 km

41.0%

284 years

1.93 km

2.8%

30.38 km

43.8%

266 years

38.95 km

56.2%

207 years

0.00 km

0.0%

69.33 km

100.0%

117 years

Introduced vegetation

878.93 ha

1.70 ha

0.6%

3404 years

90.80 ha

31.4%

92.50 ha

32.0%

190 years

196.80 ha

68.0%

89 years

0.00 ha

0.0%

289.30 ha

100.0%

61 years

H2A/2B outside DINO - Fire in piñon-juniper and sagebrush

Recent FR in piñon-juniper of 216 years < 400-600 years – H2A rejected

Recent FR in Wyoming/Basin big sagebrush of 182 years < 2,500-5,000 years – H2B rejected

Recent FR in mountain big sagebrush of years 976 years > 458-729 years – H2B supported

Significantly less resource management burning than inside, but short natural FR

Vegetation Types

Total line length or area

Human-caused: resource management

Human-caused: unspecified

Human-caused: Total

Natural: lightning

Unknown cause Total fire

Outside Dinosaur

Piñon-juniper 1352.00 km 1.13 km

1.0%

21225 years

7.24 km

6.5%

8.37 km

7.6%

2866 years

97.37 km

88.0%

247 years

4.88 km

4.4%

110.62 km

100.0%

216 years

Wyoming/Basin big sagebrush 335.18 km 0.05 km

0.2%

118922 years

7.21 km

22.0%

7.26 km

22.2%

819 years

24.98 km

76.3%

238 years

0.52 km

1.6%

32.76 km

100.0%

182 years

Mountain big sagebrush 20.36 km 0.00 km

0.0%

0.02 km

0.0%

0.02 km

5.4%

18059 years

0.35 km

94.6%

1032 years

0.00 km

0.0%

0.37 km

100.0%

976 years

Montane shrubland 31.03 km 0.00 km

0.0%

0.18 km

17.3%

0.18 km

17.3%

3448 years

0.77 km

74.0%

806 years

0.09 km

8.7%

1.04 km

100.0%

597 years

Whole AOI 2155.92 km 1.19 km

0.6%

32140 years

30.82 km

15.9%

32.01 km

16.6%

1195 years

154.84 km

80.1%

247 years

6.52 km

3.4%

193.37 km

100.0%

198 years

H3A - Piñon-juniper expansion and the biophysical environment

Preference for elevations of 2000-2400 m, intermediate slopes of 10-30%

H3B - Piñon-juniper contraction and fire

Contraction 1981-2000 was associated with fire, supporting H3B

If same rate of contraction from natural fire occurred 1910-1981, and was combined with contraction from all 1981-2000 fires (natural and resource management burning), ~86% contraction inside DINO and ~98% contraction outside explained by fire

H1A - Woodland expansion

Net decreases in woodland, increases in shrubland

Previous studies used small samples, & focused on changes in density, not historical/modern ecotones[11,12]

H1B - Woodland expansion relative to ecotones

Most expansion did occur close to the ecotone

Short-range and long-range dispersal agents

H2A/2B - Fire in piñon-juniper and sagebrush

Modern rotations in piñon-juniper and sagebrush (most) are short compared to historical

Inside DINO, resource-management burning causing much of the accelerated FR; both in and out, natural rotations are shorter (likely cheatgrass, possibly climate change)

H3A - Piñon-juniper expansion and the biophysical environment

Expansion showed preference with only two variables, elevation and slope, consistent with some studies

Expansion or simply post-fire recovery?

H3B - Piñon-juniper contraction and fire

Contraction strongly associated with fire

Previous studies have only examined areas of expansion

Current public land management paradigms

Fire exclusion has led to unnatural shifts in vegetation → fire must be reintroduced[16]

Long-term spatially extensive data from the GLO surveys reveal otherwise

Century-scale dynamics involve spatially heterogeneous expansion and contraction of several ecosystems, mediated by natural fire and human land uses

Significant losses also occurred recently in Mesa Verde National Park, Colorado[19]

Losses in DINO and Mesa Verde give support to paradigm of woodlands in decline on the Colorado Plateau from excessive fire since Euro-American settlement

If the goal is to preserve natural vegetation of DINO

Piñon-juniper woodlands should become an ecosystem of conservation

Direct control of cheatgrass

Cessation of prescribed burning inside DINO

Aggressive suppression of human-set fires inside and outside DINO

Such measures may help increase the park’s resistance and resilience to increased future fire, and would help to restore the historical range of woodlands found nearly a century ago

National Park Service

Dr. William Baker

Dr. Steve Prager & Dr. Ken Driese

[1] Archer, S. (1989) Have southern Texas savannas been converted to woodlands in recent history? The American Naturalist, 134, 545-561.

[2] Van Auken, O.W. (2000) Shrub invasion of North American semiarid grasslands. Annual Review of Ecology and Systematics, 31, 197-215.

[3] Weisberg, P.J., Lingua, E., & Pillai, R.B. (2007) Spatial patterns of pinyon-juniper woodland expansion in central Nevada. Rangeland Ecology and Management, 60, 115-124.

[4] Miller, R.F., Tausch, R.J., McArthur, E.D., Johnson, D.D., & Sanderson, S.C. (2008) Age structure and expansion of piñon-juniper woodlands: a regional perspective in the Intermountain West. USDA Forest Service Research Paper RMRS-RP-69, Rocky Mountain Research Station, Fort Collins, CO.

[5] Romme, W.H., Allen, C.D., Bailey, J.D., Baker, W.L., Bestelmeyer, B.T., Brown, P.M., Eisenhart, K.S., Floyd, M.L., Huffman, D.W., Jacobs, B.F., Miller, R.F., Muldavin, E.H., Swetnam, T.W., Tausch, R.J., & Weisberg, P.J. (2009) Historical and modern disturbance regimes, stand structures, and landscape dynamics in piñon-juniper vegetation of the western United States. Rangeland Ecology and Management, 62, 203-222.

[6] Manier, D.J., Hobbs, N.T., Theobald, D.M., Reich, R.M., Kalkhan, M.A., & Campbell, M.R. (2005) Canopy dynamics and human caused disturbance on a semi-arid landscape in the Rocky Mountains, USA. Landscape Ecology, 20, 1-17.

[7] Breshears, D.D., Cobb, N.S., Rich, P.M., Price, K.P., Allen, C.D., Balice, R.G., Romme, W.H., Kastens, J.H., Floyd, M.L., Belnap, J., Anderson, J.J., Myers, O.B., & Meyer, C.W. (2005) Regional vegetation die-off in response to global-change-type drought. Proceedings of the National Academy of Sciences, 102, 15144-15148.

[8] Sallach, B.K. (1986) Vegetation changes in New Mexico documented by repeat photography. Thesis, New Mexico State University, Las Cruces.

[9] Galatowitsch, S.M. (1990) Using the original land survey notes to reconstruct presettlement landscapes in the American West. Great Basin Naturalist, 50, 181-191.

[11] Soulé, P.T., & Knapp, P.A. (1999) Western juniper expansion on adjacent disturbed and near-relict sites. Journal of Range Management, 52, 525-533.

[12] Miller, R.F., & Rose, J.A. (1999) Fire history and western juniper encroachment in sagebrush steppe. Journal of Range Management, 52, 550-559.

[16] U.S. Dept. of Interior and U.S. Dept. of Agriculture. (2010) A national cohesive wildland fire management strategy. http://www.forestsandrangelands.gov/