Biogeography of Pleistocene conifer species from the Ziegler Reservoir fossil site, Snowmass Village, Colorado

Abstract

Pleistocene biogeography of conifer species is poorly known in much of western North America. We conducted morphological studies on 201 conifer cones and cone fragments recovered from Pleistocene sediments at the Ziegler Reservoir fossil site (2705 m) near Snowmass Village, Colorado. The basin, formed ~155–130 ka, contains fossil-bearing lacustrine, palustrine, and colluvial sediments spanning approximately 85 ka. Using a suite of morphological characters, particularly cone-scale bracts, we differentiated species of Abies, Picea, and Pseudotsuga. All fossil Abies specimens were assignable based on bract morphology to Abies concolor, which is currently absent from central Colorado (nearest populations are 160 km southwest of the site). A. concolor occurs only in sediments of MIS 5d and 5c. Pseudotsuga menziesii and Picea engelmannii cones occurred in sediments corresponding to MIS 5e, 5d, 5c, and 5a. A fourth conifer species, occurring in sediments of MIS 5e, 5d, 5c, and 5a, is difficult to assign to any extant species. Bract morphology is similar to Picea pungens, which grows near the site today, but scale morphology is unlike P. pungens. These fossils may represent ancestral P. pungens, an extinct variant, or an extinct sister species.

The influence of orbital parameters on the North American Monsoon system during the Last Interglacial Period

“…Very few terrestrial LIG proxies exist in the southwestern US and none of them unambiguously project seasonal precipitation anomalies. Multiproxy data from wetland records in Colorado (Miller et al ., 2014) and pollen proxies from ancient lakes in California (Bradbury, 1997; Ku et al ., 1998; Menking et al ., 1997; Reheis et al ., 2012) suggest overall wetter conditions during the early LIG, but it is not clear whether these anomalies are related to summer or winter precipitation.…”

Wetter Summers Mitigated Temperature Stress on Rocky Mountain Forests During the Last Interglacial Warm Period

“…While the climate of the interglacial was not homogeneously warm, we note that the increased summer temperatures and precipitation that are the key climate features of the Eemian simulations were also present in 120 ka simulations (Insel & Berkelhammer, 2021;Scussolini et al, 2019). (Miller et al, 2014). The wood samples were preserved with sufficient integrity to identify ring boundaries and key anatomical features (Figures S1-S5).…”

“…(a and b) Downscaled climate model simulations of Eemian (125ka) temperature and precipitation relative to modern (Insel & Berkelhammer, 2021). (c and d) Maps indicating the broader and local context of the modern and subfossil wood samples(Miller et al, 2014).…”

“…To assess how the effects of warming and higher evaporation-demand influenced stress on common trees species in the western US, we analyzed a unique collection of exceptionally preserved interglacial subfossil wood samples from Snowmass, Colorado (Mahan et al, 2014;Miller et al, 2014). Earlier analyses on these samples showed the wood assemblage contained Abies and Picea (like today) and that growing conditions were similar, but more favorable in terms of moisture stress, relative to modern (Brown et al, 2014).…”

Caracterización morfológica y genética de las poblaciones de Abies en Hidalgo, México: importancia de la identidad taxonómica para el aprovechamiento forestal

“…No obstante, las características morfológicas siguen siendo la manera usual de delimitar a las especies de abetos (Fernández & Nepamuceno 1989, Strandby et al 2009, Vázquez-García et al 2014, Papageorgiou et al 2015, Jasińska et al 2017. Muchos autores han descrito especies de coníferas con base en características morfológicas como los caracteres sexuales, ya que limitan el intercambio de gametos, o atributos específicos de las hojas como los canales resiníferos (Martínez 1963, Debreczy & Rácz 1995, Miller et al 2014, Sekiewicz et al 2016, Orlova et al 2020. Adicionalmente, los análisis moleculares constituyen herramientas eficientes que esclarecen dudas taxonómicas generadas por la morfología, establecen relaciones genéticas y ayudan en la identificación de especies (Aguirre-Planter et al 2000, Shao & Xiang 2015, Xiang et al 2009.…”