Development of the mixed conifer forest in northern New Mexico and its relationship to Holocene environmental change

Chihuahueños Bog (2925 m) in the Jemez Mountains of northern New Mexico contains one of the few records of late-glacial and postglacial development of the mixed conifer forest in southwestern North America. The Chihuahueños Bog record extends to over 15,000 cal yr BP. AnArtemisiasteppe, then an openPiceawoodland grew around a small pond until ca. 11,700 cal yr BP whenPinus ponderosabecame established. C/N ratios,δ13C andδ15N values indicate both terrestrial and aquatic organic matter was incorporated into the sediment. Higher percentages of aquatic algae and elevated C/N ratios indicate higher lake levels at the opening of the Holocene, but a wetland developed subsequently as climate warmed. From ca. 8500 to 6400 cal yr BP the pond desiccated in what must have been the driest period of the Holocene there. C/N ratios declined to their lowest Holocene levels, indicating intense decomposition in the sediment. Wetter conditions returned after 6400 cal yr BP, with conversion of the site to a sedge bog as groundwater levels rose. Higher charcoal influx rates after 6400 cal yr BP probably result from greater biomass production rates. Only minor shifts in the overstory species occurred during the Holocene, suggesting that mixed conifer forest dominated throughout the record.

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Historical dominance of low-severity fire in dry and wet mixed-conifer forest habitats of the endangered terrestrial Jemez Mountains salamander (Plethodon neomexicanus)

Forest Ecology and Management ◽

10.1016/j.foreco.2016.05.011 ◽

2016 ◽

Vol 375 ◽

pp. 12-26 ◽

Cited By ~ 14

Author(s):

Ellis Q. Margolis ◽

Steven B. Malevich

Keyword(s):

Conifer Forest ◽

Mixed Conifer ◽

Mixed Conifer Forest ◽

Jemez Mountains ◽

Forest Habitats

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Holocene vegetation and fire regimes in subalpine and mixed conifer forests, southern Rocky Mountains, USA

International Journal of Wildland Fire ◽

10.1071/wf07028 ◽

2008 ◽

Vol 17 (1) ◽

pp. 96 ◽

Cited By ~ 46

Author(s):

R. S. Anderson ◽

C. D. Allen ◽

J. L. Toney ◽

R. B. Jass ◽

A. N. Bair

Keyword(s):

Rocky Mountains ◽

High Elevation ◽

Picea Engelmannii ◽

Abies Lasiocarpa ◽

Conifer Forest ◽

Mixed Conifer ◽

The Holocene ◽

Southern Rocky Mountains ◽

Sedimentary Records ◽

Mixed Conifer Forest

Our understanding of the present forest structure of western North America hinges on our ability to determine antecedent forest conditions. Sedimentary records from lakes and bogs in the southern Rocky Mountains of Colorado and New Mexico provide information on the relationships between climate and vegetation change, and fire history since deglaciation. We present a new pollen record from Hunters Lake (Colorado) as an example of a high-elevation vegetation history from the southern Rockies. We then present a series of six sedimentary records from ~2600 to 3500-m elevation, including sites presently at the alpine–subalpine boundary, within the Picea engelmannii–Abies lasiocarpa forest and within the mixed conifer forest, to determine the history of fire in high-elevation forests there. High Artemisia and low but increasing percentages of Picea and Pinus suggest vegetation prior to 13 500 calendar years before present (cal yr BP) was tundra or steppe, with open spruce woodland to ~11 900 cal yr BP. Subalpine forest (Picea engelmannii, Abies lasiocarpa) existed around the lake for the remainder of the Holocene. At lower elevations, Pinus ponderosa and/or contorta expanded 11 900 to 10 200 cal yr BP; mixed conifer forest expanded ~8600 to 4700 cal yr BP; and Pinus edulis expanded after ~4700 cal yr BP. Sediments from lake sites near the alpine–subalpine transition contained five times less charcoal than those entirely within subalpine forests, and 40 times less than bog sites within mixed conifer forest. Higher fire episode frequencies occurred between ~12 000 and 9000 cal yr BP (associated with the initiation or expansion of south-west monsoon and abundant lightning, and significant biomass during vegetation turnover) and at ~2000–1000 cal yr BP (related to periodic droughts during the long-term trend towards wetter conditions and greater biomass). Fire episode frequencies for subalpine–alpine transition and subalpine sites were on average 5 to 10 fire events/1000 years over the Holocene, corresponding to one fire event every ~100 to 200 years. (5) Our Holocene-length sedimentary charcoal records provide additional evidence for the anomalous nature of the 20th-century fire regime, where fires were largely suppressed as a national policy.

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Mechanical fuel treatment effects on fuel loads and indices of crown fire potential in a south central New Mexico dry mixed conifer forest

Forest Ecology and Management ◽

10.1016/j.foreco.2007.06.006 ◽

2007 ◽

Vol 251 (3) ◽

pp. 195-204 ◽

Cited By ~ 14

Author(s):

Glenn J. Mason ◽

Terrell T. Baker ◽

Douglas S. Cram ◽

Jon C. Boren ◽

Alexander G. Fernald ◽

...

Keyword(s):

New Mexico ◽

Treatment Effects ◽

Crown Fire ◽

Conifer Forest ◽

Mixed Conifer ◽

Fuel Treatment ◽

Fuel Loads ◽

South Central ◽

Mixed Conifer Forest

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Using light to predict fuels-reduction and group-selection effects on succession in Sierran mixed-conifer forest

Canadian Journal of Forest Research ◽

10.1139/x11-120 ◽

2011 ◽

Vol 41 (10) ◽

pp. 2051-2063 ◽

Cited By ~ 21

Author(s):

Seth W. Bigelow ◽

Malcolm P. North ◽

Carl F. Salk

Keyword(s):

Sierra Nevada ◽

Pinus Ponderosa ◽

Ponderosa Pine ◽

Group Selection ◽

Wildlife Habitat ◽

Conifer Forest ◽

Mixed Conifer ◽

Fuels Reduction ◽

Mixed Conifer Forest ◽

Large Trees

Many semi-arid coniferous forests in western North America have reached historically unprecedented densities over the past 150 years and are dominated by shade-tolerant trees. Silvicultural treatments generally open the canopy but may not restore shade-intolerant species. We determined crossover-point irradiance (CPI) (light at which the height growth rank of pairs of species changes) for seedlings in Sierra Nevada mixed-conifer forest and used these to interpret light environments produced by fuels-reduction thinning and group selection with reserved large trees. Nine of 21 species pairs had well-defined CPIs. The CPI of the most common shade-tolerant and intolerant species (white fir ( Abies concolor (Gordon & Glendl.) Lindl. ex Hildebr.) and ponderosa pine ( Pinus ponderosa Douglas ex P. Lawson & C. Lawson)) was 22.5 mol·m–2·day–1 or 41% of full sun. Median understory irradiance increased from 9.2 mol·m–2·day–1 (17% full sun) in pretreatment forest to 13 mol·m–2·day–1 (24% full sun) in lightly and 15.5 mol·m–2·day–1 (28% full sun) in moderately thinned stands and 37 mol·m–2·day–1 (67% full sun) in group-selection openings. We estimate that 5%–20% of ground area in lightly to moderately thinned stands would have enough light to favor shade-intolerant over shade-tolerant growth compared with 89% of ground area in group-selection openings. The CPI provides a tool to assess regeneration implications of treatment modification such as increasing heterogeneity of thinning to enhance regeneration or reserving large trees in group-selection openings to maintain wildlife habitat.

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