Diploxylon Pines Research Articles

Allocation to tree bark in pine and oak species in fire affected mixed forests across the Northern Hemisphere

Pines (Pinus, with 120 species) and oaks (Quercus, with at least 400 species), the two principal forest forming genera of the Northern Hemisphere occur in fire affected landscapes over a large geographical area from 120°W to 150°E long, and from 10° to 60°N lat. We compiled studies of 116 such sites of which 75 sites had data of bark thickness. Taking a meta-analysis approach, here we have compared the absolute and relative bark thickness (bark thickness per unit stem diameter) of oak species sharing mixed stands to generalize adaptational significance of bark in relation to fire. For the meta-analysis we considered only natural forests with adequate evidences of fire history. We gave importance to relative bark thickness, which is less sensitive to tree size than absolute thickness while comparing species. At 100 cm girth the average absolute bark thickness was significantly higher for Diploxylon pines (3.65 cm) than for oaks (2.2 cm) and Haploxylon pines (1.65 cm). On an average, the relative bark thickness was higher for the fire adapted Diploxylon pines (6.3%) than for Quercus species, (4.4%). The resource allocation efficiency was higher in pine species than for oak species, emphasizing the importance of bark characters in their persistence and range expansion. The difference between species of two principal forest genera in relative bark thickness and hence success in fire affected landscapes across a wide geographical range strongly testifies its adaptational significance to fire.

Two fossil conifer species from the Neogene of Alonissos Island (Iliodroma, Greece)

Alonissos (Iliodroma) Island is really famous to palaeobotanists because of the type locality of Glyptostrobus europaeus (Brongniart) Unger only. Since the first report of the latter holotype no palaeobotanical work has taken place in Alonissos. This is the first research of the fossiliferous locality, along with new palaeobotanical, palynological and gastropod findings, revealed after 200 years. Among the collected material, a xylitic specimen was studied and identified as Pinuxylon alonissianum Mantzouka & Sakala, sp. nov. The presence of this species points to botanical affinities with sections of Diploxylon Pines (Pinus leiophylla var. chihuahuana (Engelm.) Shaw, P. arizonica Engelm., P. arizonica var. cooperi (C.E.Blanco) Farjon, P. engelmannii Carrière and P. jeffreyi Balf.) especially from Central America (Sierra Madre Occidental and Oriental of Mexico, Arizona, California, Oregon and Sierra Nevada). This is the first research of this kind revealing as the Nearest Relative bioprovince of the studied Greek fossil pine wood Central America and not Himalayas or Asia. Moreover, a palynological study and an analysis of fossil molluscs were carried out for the first time, giving more data regarding the palaeovegetation and palaeoclimate of the area. Finally, the holotype of Glyptostrobus europaeus (Brongniart) Unger, housed in the collections of the Muséum national d'Histoire naturelle, Paris (MNHN), is found, photographed and presented for the first time.

Comparative mapping among subsectionAustrales(genusPinus, family Pinaceae)

Comparative mapping in conifers has not yet been used to test for small-scale genomic disruptions such as inversions, duplications, and deletions occurring between closely related taxa. Using comparative mapping to probe this smaller scale of inquiry may provide clues about speciation in a phylogenetically problematic taxon, the diploxylon pine subsection Australes (genus Pinus, family Pinaceae). Genetic maps were constructed for two allopatric species of Australes, P. elliottii var. elliottii and P. caribaea var. hondurensis, using microsatellites and an F1 hybrid. A third map was generated directly from the meiotic products of an adult F1 hybrid, eliminating the need for an F2 generation. Numerous small-scale disruptions were detected in addition to synteny and collinearity, and these included (1) map shrinkage, (2) a paracentric inversion, (3) transmission ratio distortion, and (4) mild selection against a parental haplotype. Such cryptic signatures of genomic divergence between closely related interfertile species are useful in elucidating this problematic evolutionary history.

Rearrangement and duplication as main forces in chloroplast genome evolution in Pines

The entire nucleotide sequence of the chloroplast genome (117,190bp) of Korean pine (Pinus koraiensis) was determined and compared with the already published genome of Japanese black pine. As in the case of Japanese black pine, it retains 475 bp inverted repeats containing 3' portion of psbA gene but lacking rRNA genes. The translated amino acid sequences of respective potential coding genes showed 77% to 100% sequence similarity to those of corresponding genes of P. thunbergii. When compared with Japanese black pine, the order of the genes is fairly conserved except for the psaM gene and ndh pseudo genes. Thirteen indels that are larger than 100 bp were identified from the alignment of the two pine genomes. Except for the region containing ndh pseudo genes and that between psaI and accD, all the large indels occur near the potential rearrangement breakpoints involving several tRNA genes and their neighboring sequences as repeat units. Multiple rearrangement events appeared to be responsible for the loss of a copy of psaM gene and rps4 and ycf12 pseudo genes found in Japanese black pine. In addition, the further proceeded truncation of ndhK pseudo gene in Korean pine and ndhB pseudo gene in Japanese black pine indicate that these genes are functionally redundant in pines. Surprisingly, the loss of the gene and pseudo genes are conserved among haploxylon pines and not in diploxylon pines, suggesting that they occurred simultaneously at the time of divergence or within a short period of time after divergence of the two pine subgenera and that since then little change has occurred. There also appeared many indels that are less than 50 bps. Many of these indels appeared to be the tandem duplication products of the adjacent sequences. These tandem repeats are also very well conserved among haploxylon and among diploxylon pines.

Evolution of a triplet repeat in a conifer

The opportunity to trace the evolution of a triplet repeat is rare, especially for seed-plant lineages with a well-defined fossil record. Microsatellite PtTX2133 sequences from 18 species in 2 conifer genera were used to calibrate the birth of a CAGn repeat, from its protomicrosatellite origins to its repeat expansion. Birth occurred in the hard-pine genome ~ 136 million years ago, or 14 million generations ago, then expanded as a polymorphic triplet repeat 136-100 million years before a major North American vicariance event. Calibration of the triplet-repeat birth and expansion is supported by the shared allelic lineages among Old and New World hard pines and the shared alleles solely among North American diploxylon or hard pines. Five CAGn repeat units appeared to be the expansion threshold for Old and New World diploxylon pines. Haploxylon pine species worldwide did not undergo birth and repeat expansion, remaining monomorphic, with a single imperfect 198-bp allele. A sister genus, Picea, had only a region of cryptic simplicity, preceding a proto-microsatellite region. The polymorphic triplet repeat in hard pines is older than some long-lived microsatellites reported for reptiles, yet younger than those reported for insects. Some cautionary points are raised about phylogenetic applications for this long-lived microsatellite.

Intragenomic and interspecific 5S rDNA sequence variation in five Asian pines

Patterns of intragenomic and interspecific variation of 5S rDNA in Pinus (Pinaceae) were studied by cloning and sequencing multiple 5S rDNA repeats from individual trees. Five pines, from both subgenera, Pinus and Strobus, were selected. The 5S rDNA repeat in pines has a conserved 120-base pair (bp) transcribed region and an intergenic spacer region of variable length (382-608 bp). The evolutionary rate in the spacer region is three- to sevenfold higher than in the genic region. We found substantial sequence divergence between the two subgenera. Intragenomic sequence heterogeneity was high for all species, and more than 86% of the clones within each individual were unique. The 5S gene tree revealed that different 5S repeats within individuals are polyphyletic, indicating that their ancestral divergence preceded the speciation events. The degrees of interspecific and intragenomic divergence among diploxylon pines are similar. The observed sequence patterns suggest that concerted evolution has been acting after the diversification of the two subgenera but very weak after the speciation of the four diploxylon pines. Sequence patterns in P. densata are consistent with hybrid origin. It had higher intragenomic diversity and maintained polymorphic copies of the parental types in addition to new and recombinant types unique to the hybrid.

RESPONSES OF CONOPHTHORUS SPP. (COLEOPTERA: SCOLYTIDAE) TO BEHAVIORAL CHEMICALS IN FIELD TRIALS: A TRANSCONTINENTAL PERSPECTIVE

AbstractWe tested six behavioral chemicals, pityol, conophthorin, 4-allylanisole, verbenone, 2-hexenol, and α-pinene, in a series of field trials directed at six combinations of Conophthorus Hopkins – Pinus L. spp. (Pinaceae) in sites distributed across North America. Beetle – host tree combinations included Conophthorus ponderosae Hopkins on Pinus ponderosa Laws., C. ponderosae on Pinus monticola Dougl., Conophthorus conicolens Wood on Pinus pseudostrobus Lindl., Conophthorus teocotum Wood on Pinus teocote Schl. & Cham., Conophthorus coniperda (Schwarz) on Pinus strobus L., and Conophthorus resinosae Hopkins on Pinus resinosa Ait. trans-Verbenol was tested only on C. resinosae on P. resinosa. Traps baited with pityol caught more beetles than unbaited traps in nearly all of the assays, and conophthorin consistently inhibited male beetle response to pityol for all species tested. Behavioral responses of species of Conophthorus to α-pinene appeared to parallel host phylogeny, inasmuch as beetles using Haploxylon pines as hosts utilized α-pinene as a synergist for the beetle-produced pityol, whereas beetles using Diploxylon pines as hosts did not. α-Pinene was a synergist for pityol in C. ponderosae on P. monticola and C. coniperda on P. strobus, but not for species of Conophthorus on any other pines tested. Conophthorus ponderosae on P. ponderosa was the only beetle–host combination tested where verbenone was a synergist for pityol, but this effect was not consistent in all years of testing. It was also the only beetle–host combination in which 4-allylanisole was a repellent. For all other beetle–host combinations, verbenone was neutral to slightly repellent and 4-allylanisole was either synergistic or neutral in pityol-baited traps. Promising synergists and interruptants/repellents were identified for implementation in pest-management regimes, including conophthorin as an interruptant for all species of Conophthorus tested, 4-allylanisole as an interruptant for C. ponderosae on P. ponderosa, α-pinene as a synergist for pityol in all species tested on Haploxylon pines, and 4-allylanisole as a synergist for pityol in C. conicolens and C. coniperda.

Susceptibility of cones and seeds to fungal infection in a pine (Pinus spp.) collection

Summary Thirty‐one fungi, members of Ascomycota and Deuteromycota, were isolated from cones/seeds of 28 hosts (Pinus spp.) originating from East Asia, Europe and North America, and growing at the Montreal Botanical Garden, Canada. A total of 21 taxa of these isolated fungi are considered pathogens. The damage severity was most prevalent on Diploxylon pines of European provenance (Pinus nigra, Pinus mugo and Pinus sylvestris), and one indigenous North American species (Pinus albicaulis). Twelve fungi occurred on different hosts, i.e. Sphaeropsis sapinea (12), Herpotrichia juniperi (8), Truncatella hartigii (7), Ceuthospora sp. (5), Fusarium, spp. (5), Pestalotiopsis funerea (3), Phomopsis sp. (3), Valsa spp. (anamorph. Cytospora) (3), Diaporthe sp. (3), Fusicoccum sp. (2) and Sirococcus strobilinus (2). Sphaeropsis sapinea, Herpotrichia juniperi, Phomopsis conorum, Truncatella hartigii, Tubercularia sp. and Valsa spp. were related to high cone and seed damage. For the most frequently observed Sphaeropsis sapinea damage, the subgenus Haploxylon was less susceptible than Diploxylon, and P. sylvestris less than P. nigra and P. mugo. Pinus resinosa showed more tolerance to S. sapinea. Truncatella hartigii was more frequently associated with necrotic lesions on cones/seeds in comparison with Pestalotiopsis funerea. The results are discussed in the context of arboretum, seed orchard, nursery and quarantine management.

Late quaternary vegetation history of Wilcox Pass, Jasper National Park, Alberta

Five pollen zones are recognized in a radiocarbon and tephra dated core from an alpine site at an elevation of ca. 2355 masl in Wilcox Pass, Jasper National Park, and record Late Quaternary vegetation history. The two lower zones underlie material dated at 9600 ± 305 yr B.P. (GX-8785) and record early postglacial vegetation. The basal zone, WP1, containing an Artemisia dominated assemblage, represents tundra vegetation after deglaciation. In Zone WP2, arboreal pollen, mainly diploxylon pine, becomes dominant, and represents a lodgepole pine forest. The pollen assemblage of Zone WP3, which initially contains large amounts of haploxylon pine as well as Picea and Abies pollen, shows a transition from a forest with large amounts of whitebarkpine to vegetation resembling present-day subalpine forest. During this phase, temperatures were probably warmer than present. Zone WP4, beginning after the influx of Mazama tephra (6800 yr B.P.) to the site, records an expansion of the subalpine forest to higher elevations with a warmer climate. In Zone WP5, beginning about 2800 yr B.P., values of the main arboreal components fluctuate, indicating cooler temperatures and less favourable environmental conditions, probably associated with Neoglacial ice advances. The environmental trends observed from this record accord with those from other vegetation records in the Canadian Rockies.

Holocene vegetational history of the Kootenai River Valley, Montana

Pollen records in the Kootenai and Fisher River drainages in western Montana reveal a fivezone sequence of Holocene vegetation change. Deposition of Glacier Peak Ash-Layer G (ca. 10,540 ± 660 yr B.P.) in the lowermost sediments (clay intermixed with pebbles) at Tepee Lake gives a minimum date for the initiation of sedimentation. Initial vegetation on the newly deglaciated terrain was dominated by Pinus (probably white bark pine) with small amounts of Gramineae, Picea and Abies, reflecting a relatively cool, moist macroclimate. Two vegetation units appear to contribute to Pollen Zone II (ca. 11,000–7100 yr B.P.): arboreal communities with pines, along with Pseudotsuga or Larix, or both, and treeless vegetation dominated by Artemisia. Pollen Zone II represents an overall warmer macroclimate than occurred upon ice withdrawal. After ca. 7100 yr B.P. (Pollen Zone III) diploxylon pines became a major pollen contributor near both Tepee Lake and McKillop Creek Pond, indicating an expansion of xerophytic forest ( P. contorta and P. ponderosa) along with an increase in the prominence of Pseudotsuga menziesii or Larix occidentalis, or both. Artemisia briefly expanded coverage near Tepee Lake concomitant with the Mazama ashfall ca. 6700 yr B.P. A short-term climatic trend with more available water began after ca. 4000 yr B.P. as Abies (probably A. grandis) along with Picea engelmannii became a more regular component of the forest surrounding both sites. Emergence of the modern macroclimate is indicated primarily with the first regular appearance of Tsuga heterophylla in the pollen record by ca. 2700 yr B.P., synchronous with the development of western hemlock forest within the same latitudes in northern Idaho and northeastern Washington.

Holocene vegetation history of the Okanogan Valley, Washington

Haploxylon pine(s) and Artemisia dominated the initial vegetation in front of the receding Okanogan Lobe until ca. 10,000 yr B.P., as revealed by two pollen records in north-central Washington. After 10,000 yr B.P. the macroclimate became warmer throughout the Okanogan drainage as diploxylon pines and Artemisia increased. The Mount Mazama eruption at ca. 6700 yr B.P. is recorded as two stratigraphically separate and petrographically distinct tephra units at Bonaparte Meadows. While there are apparent short-term changes in the vegetation coincident with the ashfall(s), Artemisia continues to dominate the Okanogan Valley until ca. 5000 yr B.P. By 4700 yr B.P. the modern vegetation, dominated by Pseudotsuga menziesii, had become established around Bonaparte Meadows.

Late Quaternary Vegetation History of the Eastern Highland Rim and Adjacent Cumberland Plateau of Tennessee

Vegetation change during the past 25 000 years in and near the present Mixed Mesophytic Forest Region is inferred from pollen and plant macrofossil analyses of sediment cores from two sites on the eastern Highland Rim of Middle Tennessee, USA. Anderson Pond, in White County, dates from 25 000 radiocarbon years BP to present. During the Farmdalian Interstadial, 25 000 yr BP, northern Diploxylon pines, spruce, and deciduous trees were present at Anderson Pond, indicating a cool, moist climate. From 19 000 to 16 300 yr BP, during the Late Wisconsin glacial maximum, boreal taxa of jack pine, spruce, and fir were dominant. Late—glacial climatic amelioration began in Middle Tennessee at about 16 300 yr BP, with replacement of jack pine—spruce—fir forest by deciduous forest. Ash, ironwood, hickory, birch, butternut, willow, and elm increased in importance first, followed by beech and sugar maple. Mixed mesophytic forest taxa were most abundant during the early Holocene, between 12 500 and 8000 yr BP. A warming and drying trend between 8000 and 5000 yr BP is reflected by high influx values for pollen of oak, ash, hickory, swamp alder, and buttonbush, and by diminishing importance of mixed mesophytic forest taxa. Mingo Pond, Franklin County, Tennessee, contains a pollen record estimated to extend back to 14 000 yr BP. Mixed mesophytic forest taxa were abundantly represented at Mingo Pond during the late glacial and early Holocene, along with pollen representing prairie vegetation. Oak and sweetgum dominated the mid— and late Holocene record from Mingo Pond. Stratigraphic sites from the Missouri Ozarks to the Atlantic Coastal Plain date the full glacial in the southeastern United States between 23 000 and 16 500 yr BP. During the glacial maximum, boreal—like coniferous forests of spruce, jack pine, and fir extended southward to 34°N latitude. Mesic deciduous forest persisted through the full glacial at 35°N at Nonconnah Creek near Memphis. Full—glacial refuges for deciduous forest species may have also existed in south—facing gorges of the Cumberland Plateau and southern Appalachian Mountains in addition to bluffs along major streams in the southeastern United States. During the late glacial, beginning about 16 500 yr BP, boreal—like coniferous forest was replaced in midlatitudes (34° to 37°N) by cool—temperate coniferous—deciduous forest. In the early Holocene, between 12 500 and 8000 yr BP, cool—temperate mixed mesophytic forest prevailed between 34° and 37°N. The Mixed Mesophytic Forest Region assumed its present distribution in the mid—Holocene.

Late Quaternary Vegetation History at Waits Lake, Colville River Valley, Washington

A 10.6-m section of mostly calcareous sediments at Waits Lake, Washington, reveals a multizoned history of vegetation change since recession of Pinedale (P-2) glacial ice from the Colville River Valley. The oldest unit with high percentages of Artemisia, Gramineae, and Shepherdia canadensis-type pollen characterizes vegetation in which trees were not major components and the climate was cooler and moister than today. Pollen Zone II (ca. 10,000-6,700 yr before present [BP]) records a warmer period in which diploxylon pine was prominent. Concomitant with the Mazama ash fall (6,700 yr BP), Artemisia became particularly prominent (Pollen Zone II); but by about 5,000 yr BP, diploxylon pine was conspicuous. This comparatively short-term vegetation change probably indicates the advance of drought-tolerant Artemisia-dominated steppe northward in the Colville River Valley. The modern climax vegetation in the vicinity of Waits Lake (Pseudotsuga-dominated forest) appears to have emerged around 2,300 yr BP, although more detailed documentation of this event is hampered by the low pollen production of Pseudotsuga menziesii. The 14C dates from these calcareous sediments were corrected through use of the Mazama and Glacier Peak ash layers as time-stratigraphic marker horizons.

Lophodermium pinastri . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Lophodermium pinastri . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Pinus spp. ; a very wide range of Diploxylon (two-three needle) pines; has been recorded occasionally on Haploxylon (five needle) pines. DISEASE: Needle cast of pines. Lophodermium pinastri inhabits green needles on the tree producing no symptoms. When the needles senesce and fall to the litter, the fungus fruits. It causes no significant damage to the tree. GEOGRAPHICAL DISTRIBUTION: Widespread in Europe, western USA including Washington, Australia, New Zealand, Japan. TRANSMISSION: By air-borne ascospores in wet weather/humid conditions.

Lophodermium conigenum . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Lophodermium conigenum . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Mainly Diploxylon (two-three needle) pines, including Pinus brutia, P. densiflora, P. montana, P. mugo, P. nigra , P. resinosa, P. sylvestris, P. tabuliformis, P. contorta, P. halepensis, P. pinea and P. radiata . Has also been recorded from Haploxylon (five needle) pines. DISEASE: Needle cast of pines. Lophodermium conigenum inhabits green needles on the tree, producing no symptoms. When a branch bearing such needles is killed by an agent other than the fungus, L. conigenum fruits seprophytically on the needles. It causes no significant damage to the tree. GEOGRAPHICAL DISTRIBUTION: Widespread in Europe, a couple of records from the USA (east coast and Michigan) where it is apparently not common, New Zealand. TRANSMISSION: By air-borne ascospores in wet weather/humid conditions.

Lophodermium canberrianum . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Lophodermium canberrianum . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Diploxylon (two-three needled) pines of the ponderosa group, including Pinus ponderosa and P. engelmannii . DISEASE: Needle-cast of pines. GEOGRAPHICAL DISTRIBUTION: So far reported only from Australia (Australian Capital Territory and Victoria). TRANSMISSION: By air-borne ascospores in wet weather/humid conditions, or even exceptionally in dry conditions (Stahl, 1966).

Reexamination of postglacial vegetation history in northern Idaho: Hager Pond, Bonner Co.

Hager Pond, a mire in northern Idaho, reveals at least five pollen zones since sediments formed after the last recession of continental ice (>9500 yr BP). Zone I (>9500-8300 yr BP) consists mainly of diploxylon pine, plus low percentages of Abies, Artemisia, and Picea. SEM examination of conifer pollen at selected levels in the zone reveals that Pinus albicaulis, P. monticola, and P. contorta are present in unknown proportions. The zone resembles modern pollen spectra from the Abies lasiocarpa-P. albicaulis association found locally today only at high elevation. Presence of whitebark pine indicates a cooler, moister climate than at present, but one which was rapidly replaced in Zone II (8300-7600 yr BP) by warmer, drier conditions as inferred by prominence of grass with diploxylon pine. Zone III (7600-3000 yr BP) was probably dominated by Pseudotsuga menziesii, plus diploxylon pine and prominent Artemisia and denotes a change in vegetation but continuation of the warmer drier conditions. Beginning at approximately 3000 yr BP Picea engelmannii, Abies lasiocarpa, and/or A. grandis and diploxylon pine were dominants and the inferred climate became cooler and moister concomitant with Neoglaciation. The modern climatic climax (Zone V), with Tsuga heterophylla as dominant, has emerged in approximately the last 1500 yr.

Late Quaternary Pollen Record from Big Meadow, Pend Oreille County, Washington

The pollen record at Big Meadow in northeastern Washington contains at least 5 pollen zones spanning ca. the last 12,500 yr. Initial vegetation after Pinedale deglaciation was nonarboreal. Estimates of the pollen influx and the dominance of Artemisia and Gramineae plus comparatively little pine pollen suggest a tundra—like landscape from the time of deglaciation until ca. 9,700 BP. Zone II probably lies disconformably atop this earliest zone and reveals a community dominated first by grasses plus diploxylon pines and later by diploxylon pines without prominent grasses (Zone III) between 9,700 and 3,300 BP. zone IV demarcates a short reversal of climatic conditions in which Picea and Abies are relatively prominent. Tsuga heterophylla, the present day climatic climax dominant of the area, rapidly emerged in the pollen record at ca. 2,400 BP.

Late Quaternary pollen record from the Sanpoil River Valley, Washington

An 8.5-m core from Simpsons Flats, Ferry Co., Washington, includes at least four pollen zones spanning the last 10 000 years. With retreat of the Sanpoil lobe of Pinedale continental ice in the river valley, vegetation with low pollen influx (zone I) and dominated by Artemisia, Gramineae, and Pinus became prominent. Owing to the narrowness of the valley near Simpsons Flats, it is not clear whether pines were in the valley or on the adjacent upland sites.Mazama ash (ca. 6700 years before present (B.P.)) probably lies disconformably atop zone I and is included within a long-term warmer drier period (zone II) characterized by diploxylon pine pollen. Evidence for an effect of the Mazama ashfall on the vegetation is inconclusive. Zone III (4050–2700 years B.P.) marks a comparatively short period in which climatic conditions were slightly moister (although not necessarily cooler) than today, and the vegetation was dominated by diploxylon pine but with increased influx and frequency of Picea, Abies, and some haploxylon pine. The modern vegetation in the vicinity of the mire is dominated by Pinus ponderosa and Gramineae (including Festuca idahoensis) and seems to have emerged within the last 2700 years (zone IV).

Pollen Sequence from the Columbia Basin, Washington: Reappraisal of Postglacial Vegetation

During the early postglacial time of eastern Washington (10,000 to 18,000 years B.P.) treeless vegetation dominated by Artemisia may have occupied extensive areas of stony patterned ground, while conifers (haploxylon pine with Abies and Picea) were restricted to nearby loess hills. Decrease in Artemisia, Abies and Picea, suggesting a warming trend, began over 9000 14C years ago and coincided with a marked increase in diploxylon pine. INTRODUCTION The sequence of vegetation since the last recession of the Cordilleran ice sheet in eastern Washington (Richmond et al., 1965) (see Fig. 1) long has been inferred to show three stages. Most recently, Heusser (1965) has outlined these stages as follows: III. Pinus ponderosa dominant 4000-0 years B.P. II. Grasses, chenopods and composites dominant 8000-4000 years B.P. I. Pinus contorta parkland 13,000-8000 years B.P. This sequence is based on the numerous pollen diagrams constructed by Hansen (1947) in his pioneering work concerning the Quaternary vegetation history of the Pacific Northwest. Dates used by Hansen in the interpretation of his data were of necessity only relative orders of magnitude, being based on estimated rates of peat accumulation before the advent of radiocarbon dating. Pine pollen is omnipresent in these diagrams. Hansen reported that at least three species (P. ponderosa, P. monticola and P. contorta) could be distinguished in the fossil pollen record based on their different corpus breadths. Fossil pine pollen having a corpus breadth within the size range thought to represent modern species was assigned to that taxon in the pollen diagrams (Hansen, 1947). Re-evaluation of this technique as applied to pines in the Pacific Northwest suggests the method has low reliability (Mack, 1 Present address: Department of Botany, Washington State University, Pullman 99163.