Treeless Environment Research Articles

Drivers of functional and phylogenetic structures of mountain bird assemblages along an altitudinal gradient from the montane to alpine zones

Understanding the process underlying the spatial gradients in biodiversity is a fundamental issue in ecology. Altitudinal gradients are ideal systems for examining the community assembly process because they represent rapid changes in environmental conditions over relatively short distances. The functional and phylogenetic approaches allow a deeper mechanistic understanding of the underlying assembly process. However, whether community assembly from montane to alpine zones is driven more by ecological constraints or human settlement patterns is not fully resolved and may vary by system. Here, we examined the phylogenetic and trait-based functional structures from the montane to alpine zones and clarified the effects of natural environmental factors and human-induced landscape transformation on the breeding bird assemblage on Mount Norikura, central Japan. Breeding birds from 700 to 3026 m a.s.l. were surveyed in 2016–2017. Bird community structures were examined based on species richness, functional and phylogenetic structures. A null modelling approach was performed to examine functional and phylogenetic cluster/overdispersion structures; clustering and overdispersion imply species elimination by environmental filters and limiting similarity as a corollary of competitive exclusion of species, respectively. Furthermore, we examined the relative effect of natural environments and human disturbance. Bird species richness was high in the mountain base to mid-elevation, then decreased with elevation. We found a contrasting pattern in the phylogenetic and functional structures in the alpine zone: phylogenetic overdispersion and functional clustering. In contrast, the functional and phylogenetic structures were clustered in the upper parts of the subalpine zone. The functional and phylogenetic clusterings in the lower parts of the subalpine and montane zones were negligible with the weak effects of the environmental filtering. Single-trait analysis showed that the high abiotic tolerance and foraging or nesting capabilities in treeless environments were clustered in the alpine zone, and mobility was clustered in the subalpine zones. Natural environments strongly affected bird community structures, but human disturbance added species to assemblages in the mountain base to mid-elevation and changed the functional and phylogenetic structures. Our findings highlight that filtering by severe natural environments is a fundamental community assembly process in high mountain regions, whereas filtering effects can be weaker at lower elevations. Furthermore, the filtering effect should differ between the alpine and the upper parts of the subalpine zones because of different combinations of clustered traits. Climate change and landscape transformation pressures may strongly impact biodiversity in the alpine and subalpine zones, respectively.

Pinus contorta Alters Microenvironmental Conditions and Reduces Plant Diversity in Patagonian Ecosystems

Pinus contorta is considered one of the most invasive tree species worldwide, generating significant impacts on biodiversity and ecosystems. In several Patagonian ecosystems in southern Chile, it has escaped from plantations established mainly in the 1970s, and is now invading both forests and treeless environments. In this study, we evaluated the impact of the invasion of P. contorta on microenvironmental conditions in Araucaria araucana forest and Patagonian steppe ecosystems, and assessed how these changes related to the richness and abundance of native and non-native plant species. In each ecosystem, 24 plots of 100 m2 were established along a gradient of P. contorta biomass, where 18 environmental variables and the composition of native and non-native vegetation were measured at a local scale. Our results indicated that increased pine biomass was associated with differences in microclimatic conditions (soil and air temperature, photosynthetically active radiation (PAR), and soil moisture) and soil properties (potassium, nitrate, pH, and litter accumulation). These changes were ecosystem dependent, however, as well as associated with the level of invasion. Finally, the reduction in the richness and abundance of native plants was associated with the changes in soil properties (accumulation of leaf litter, pH, and organic matter) as well as in the microclimate (minimum air temperature, PAR) generated by the invasion of P. contorta. Overall, our results confirm that the invasion of P. contorta impacts microenvironmental conditions (i.e., canopy cover, litter accumulation, minimum air temperature, and maximum soil temperature) and reduces native plant diversity. For future restoration plans, more emphasis should be given to how environmental changes can influence the recovery of invaded ecosystems even after the removal of the living pine biomass (i.e., legacy of the invasion).

Modeling cloud-to-ground lightning probability in Alaskan tundra through the integration of Weather Research and Forecast (WRF) model and machine learning method

Wildland fires exert substantial impacts on tundra ecosystems of the high northern latitudes (HNL), ranging from biogeochemical impact on climate system to habitat suitability for various species. Cloud-to-ground (CG) lightning is the primary ignition source of wildfires. It is critical to understand mechanisms and factors driving lightning strikes in this cold, treeless environment to support operational modeling and forecasting of fire activity. Existing studies on lightning strikes primarily focus on Alaskan and Canadian boreal forests where land-atmospheric interactions are different and, thus, not likely to represent tundra conditions. In this study, we designed an empirical-dynamical method integrating Weather Research and Forecast (WRF) simulation and machine learning algorithm to model the probability of lightning strikes across Alaskan tundra between 2001 and 2017. We recommended using Thompson 2-moment and Mellor–Yamada–Janjic schemes as microphysics and planetary boundary layer parameterizations for WRF simulations in the tundra. Our modeling and forecasting test results have shown a strong capability to predict CG lightning probability in Alaskan tundra, with the values of area under the receiver operator characteristics curves above 0.9. We found that parcel lifted index and vertical profiles of atmospheric variables, including geopotential height, dew point temperature, relative humidity, and velocity speed, important in predicting lightning occurrence, suggesting the key role of convection in lightning formation in the tundra. Our method can be applied to data-scarce regions and support future studies of fire potential in the HNL.

Late Quaternary history of Lammefjorden, north-west Sjælland, Denmark

Lammefjorden is a reclaimed fjord in north-west Sjælland, Denmark. Sediment cores from the area were collected to study its development after the last deglaciation, in particular the sea-level history. Late glacial and Early Holocene lake and bog deposits occur below marine deposits. Sparse late glacial fossil assemblages indicate tree-less environments with dwarf-shrub heaths. Early Holocene deposits contain remains of Betula sec. Albae sp. and Pinus sylvestris, which indicate open forests. The wetland flora comprised the calciphilous reed plant Cladium mariscus and the water plant Najas marina. Marine gyttja from basins is characterised by sparse benthic faunas, probably due to high sedimentation rates. In some areas, shell-rich deposits were found, with large shells of Ostrea edulis, indicative of high summer temperatures, high salinity and strong tidal currents. A marine shell dated to 6.7 cal. ka provides a minimum age for the marine transgression of Lammefjorden.

Autonomous in situ measurement of daily courses of the net CO2 exchange rate in a moss from alpine environment ( Short Communication )

Moss-dominated vegetation type is considered one of the the most productive community type in treeless alpine environments in European mountains. In this study, net carbon exchange rate (NCER) of alpine moss Polytrichum commune was measured by automatic CO2 exchange station unit. Samples of mosses were collected in a mountains from the site located above tree line (1420 m a.s.l.), and transferred to Brno, Czech Republic. Then the cluster of moss (23 cm in diameter, 30 cm in depth) including dead parts was placed into open measuring chamber end exposed to local climate for two weeks in autumn 2019. The chamber closed by a transparent lid repeatedly each 20 min and NCER measured by the system. Data on photosynthetically active radiation (PAR), relative air humidity (RH), and moss temperature (T) were recorded as well. Maximum/ minimum dark respiration reached 1.0 and 0.2 mmol (CO2) m-2 s-1. The highest NCER was found - 0.6 mmol (CO2) m-2 s-1 was caused by photosynthesis of moss clump at the temperature within the range of 14.5-17.5°C and 100% of relative air humidity.

Keep your feet warm? A cryptic refugium of trees linked to a geothermal spring in an ocean of glaciers.

Up to now, the most widely accepted idea of the periglacial environment is that of treeless ecosystems such as the arctic or the alpine tundra, also called the tabula rasa paradigm. However, several palaeoecological studies have recently challenged this idea, that is, treeless environments in periglacial areas where all organisms would have been exterminated near the glacier formed during the Last Glacial Maximum, notably in the Scandinavian mountains. In the Alps, the issue of glacial refugia of trees remains unanswered. Advances in glacier reconstructions show that ice domes did not cover all upper massifs, but glaciers filled valleys. Here, we used fossils of plant and malacofauna from a travertine formation located in a high mountain region to demonstrate that trees (Pinus, Betula) grew with grasses during the Lateglacial-Holocene transition, while the glacier fronts were 200-300m lower. The geothermal travertine started to accumulate more than 14,500years ago, but became progressively more meteogene about 11,500years ago due to a change in groundwater circulation. With trees, land snails (gastropods) associated to woody or open habitats and aquatic mollusc were also present at the onset of the current interglacial, namely the Holocene. The geothermal spring, due to warm water and soil, probably favoured woody glacial ecosystems. This new finding of early tree growth, combined with other scattered proofs of the tree presence before 11,000years ago in the western Alps, changes our view of the tree distribution in periglacial environments, supporting the notion of tree refugia on nunataks in an ocean of glaciers. Therefore, the tabula rasa paradigm must be revisited because it has important consequences on the global changes, including postglacial plant migrations and biogeochemical cycles.

Wind Distortion in Alpine and Subantarctic Plants is Constant among Life Forms but does not Necessarily Reflect Prevailing Wind Direction

ABSTRACTWoody plants in windy environments have been used as indicators of prevailing wind direction, because wind can influence plant growth form. We investigated whether non-woody plants also display consistent prevailing wind deformation by observing the direction of asymmetry in growth form of cushion plants, graminoids, and prostrate shrubs growing in highly wind-exposed treeless environments in alpine Tasmania and subantarctic Macquarie Island. Wind distortion of individual plants was inferred from vertical photographs of feldmark and alpine heath vegetation. High correspondence in growth direction between plants of different types suggests a uniform wind influence on plants at the local scale (within <2 m). Dominant wind direction inferred from plant distortion was not consistent with the strongest and most frequent winds. On a relatively dry mountain with shallow soils the plants responded to strong northwest winds in an apparent desiccation response. Elsewhere, they responded to strong southwest winds in an apparent ice abrasion response. We conclude that, in maritime alpine and subantarctic environments, the direction of wind distortion can be measured using any of shrubs, graminoids, or cushion plants, but that this direction is not necessarily a response to the prevailing strongest winds, but rather winds that most damage foliage, the cause of damage varying with environmental context.

Pine invasion impacts on plant diversity in Patagonia: invader size and invaded habitat matter

Conifers, which are widely planted as fast growing tree crops, are invading forested and treeless environments across the globe, causing important changes in biodiversity. However, how small-scale impacts on plant diversity differ according to pine size and habitat context remains unclear. We assessed the effects of different stages of pine invasion on plant communities in forest and steppe sites located in southern Chile. In each site, we sampled plant diversity under and outside the canopy of Pinus contorta individuals, using paired plots. We assessed the relative impact of pine invasion on plant species richness and cover. In both sites, richness and cover beneath pine canopy decreased with increasing pine size (i.e. height and canopy area). A significant negative impact of pines on species richness and plant cover was detected for pines over 4 m in height. The impact of pines on plant richness and cover depended on pine size (i.e. canopy area) and habitat type. Larger pines had more negative impacts than smaller pines in both sites, with a greater impact for a given pine size in the Patagonian steppe compared to the A. araucaria forest. Species composition changed between under and outside canopy plots when pines were 4 m or taller. Pine presence reduced cover of most species. The impacts of pine invasions are becoming evident in forested and treeless ecosystems of southern Chile. Our results suggest that the magnitude of pine invasion impacts could be related to how adapted the invaded community is to tree cover, with the treeless environment more impacted by the invasion.

Pine invasions in treeless environments: dispersal overruns microsite heterogeneity.

Understanding biological invasions patterns and mechanisms is highly needed for forecasting and managing these processes and their negative impacts. At small scales, ecological processes driving plant invasions are expected to produce a spatially explicit pattern driven by propagule pressure and local ground heterogeneity. Our aim was to determine the interplay between the intensity of seed rain, using distance to a mature plantation as a proxy, and microsite heterogeneity in the spreading of Pinus contorta in the treeless Patagonian steppe. Three one-hectare plots were located under different degrees of P.contorta invasion (Coyhaique Alto, 45° 30'S and 71° 42'W). We fitted three types of inhomogeneous Poisson models to each pine plot in an attempt for describing the observed pattern as accurately as possible: the "dispersal" models, "local ground heterogeneity" models, and "combined" models, using both types of covariates. To include the temporal axis in the invasion process, we analyzed both the pattern of young and old recruits and also of all recruits together. As hypothesized, the spatial patterns of recruited pines showed coarse scale heterogeneity. Early pine invasion spatial patterns in our Patagonian steppe site is not different from expectations of inhomogeneous Poisson processes taking into consideration a linear and negative dependency of pine recruit intensity on the distance to afforestations. Models including ground-cover predictors were able to describe the point pattern process only in a couple of cases but never better than dispersal models. This finding concurs with the idea that early invasions depend more on seed pressure than on the biotic and abiotic relationships seed and seedlings establish at the microsite scale. Our results show that without a timely and active management, P.contorta will invade the Patagonian steppe independently of the local ground-cover conditions.

Up to 400‐year‐old Rhododendron shrubs on the southeastern Tibetan Plateau: prospects for shrub‐based dendrochronology

In harsh and treeless environments, shrubs constitute the dominant growth form of woody plants, thus offering the opportunity to extend dendrochronological networks beyond the uppermost and northernmost distribution limits of trees. However, shrub‐based dendrochronology has so far resulted in only a few long and climate‐responsive ring‐width chronologies at such stressful sites, particularly above the alpine tree line. A previous study on an alpine Rhododendron shrub species resulted in &lt;80‐year‐long ring‐width chronologies. Here, we collected Rhododendron aganniphum var. schizopeplum stems from elevations between 4000 and 4500 m a.s.l. on the SE Tibetan Plateau and built six tree‐ring width chronologies. One of them is 401 years long and well replicated from AD 1670 to 2011 (EPS&gt;0.85), thus representing the longest shrub chronology available to date. A principal component analysis (PCA) converted the total variability of all six site chronologies into PCs. Then, the six site chronologies and the PC1, accounting for 65.9% of the total variance of the tree‐ring width, were correlated with time series of monthly climate data. Based on this, the year‐to‐year variability of the ring‐width indices was positively correlated with July temperature, which thus turned out to be the dominant factor controlling growth. Accordingly, such long shrub‐ring chronologies may act as climatic and ecological proxies in treeless environments of the Tibetan Plateau.

Destruction without extinction: long‐term impacts of an invasive tree species on Galápagos highland vegetation

Summary 1. A common belief in invasion ecology is that invasive species are a major threat to biodiversity, but there is little evidence yet that competition from an exotic plant species has led to the extinction of any native plant species at the landscape scale. However, effects of invasive species at community and ecosystem levels can severely compromise conservation goals. 2. Our model species, the red quinine tree (Cinchona pubescens), was introduced to the Galápagos Islands in the 1940s and today extends over at least 11 000 ha in the highlands of Santa Cruz Island. It is also invasive on other oceanic islands. 3. We adopted a long‐term approach, analysing permanent plots in the Fern‐Sedge vegetation zone over 7 years, to test for impacts of C. pubescens density on resident plant species composition and on microclimate variables. We also tested whether the C. pubescens invasion facilitated the invasion of other species. 4. The rapid pace of the C. pubescens invasion was indicated by a more than doubling of percentage cover, a 4.6‐fold increase in mean stand basal area and a 4‐fold increase in the number of stems ha−1 in 7 years. 5. Photosynthetically active radiation was reduced by 87% under the C. pubescens canopy while precipitation increased because of enhanced fog interception. 6. Cinchona pubescens significantly decreased species diversity and the cover of most species by at least 50%. Endemic herbaceous species were more adversely affected than non‐endemic native species. Stachys agraria, another invasive species, colonized bare ground that developed under the C. pubescens canopy. 7. The numbers of native, endemic and introduced species in the study area remained constant throughout the 7‐year period. 8. Synthesis. This study clearly established C. pubescens as a habitat transformer, although its average cover did not exceed 20%. Despite the fact that no plant species has been lost completely from the study area so far, the introduction of the novel tree life form to a formerly treeless environment led to significant changes in stand structure and environmental conditions and to decreases in species diversity and cover. Such changes clearly conflict with conservation goals as set by the Convention on Biological Diversity.

Towards an energy‐based runoff generation theory for tundra landscapes

AbstractRunoff hydrology has a large historical context concerned with the mechanisms and pathways of how water is transferred to the stream network. Despite this, there has been relatively little application of runoff generation theory to cold regions, particularly the expansive treeless environments where tundra vegetation, permafrost, and organic soils predominate. Here, the hydrological cycle is heavily influenced by 1) snow storage and release, 2) permafrost and frozen ground that restricts drainage, and 3) the water holding capacity of organic soils. While previous research has adapted temperate runoff generation concepts such as variable source area, transmissivity feedback, and fill‐and‐spill, there has been no runoff generation concept developed explicitly for tundra environments. Here, we propose an energy‐based framework for delineating runoff contributing areas for tundra environments. Aerodynamic energy and roughness height control the end‐of‐winter snow water equivalent, which varies orders of magnitude across the landscape. Radiant energy in turn controls snowmelt and ground thaw rates. The combined spatial pattern of aerodynamic and radiant energy control flow pathways and the runoff contributing areas of the catchment, which are persistent on a year‐to‐year basis. While ground surface topography obviously plays an important role in the assessment of contributing areas, the close coupling of energy to the hydrological cycles in arctic and alpine tundra environments dictates a new paradigm. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Plant and Insect Fossils from the Mayo Indian Village Section (Central Yukon): New Data on Middle Wisconsinan Environments and Glaciation

La coupe du village indien de Mayo renferme le Till de Mayo, témoin de la Glaciation de McConnell datant du Wisconsinien, sous lequel se trouvent des sédiments fluviatiles comprenant des matériaux organodétritiques rares. Les datations au 14C du till et des sédiments sous-jacents obtenues antérieurement n'avaient pas permis de dater avec précision l'âge de la Glaciation de McConnell. La nouvelle date de 29,6 ka obtenue par accélérateur sur des graines de Corispermum hyssopifolium provenant des dépôts sous-jacents au till indique que la Glaciation de McConnell date probablement du Wisconsinien supérieur et qu'elle correspond aux glaciations de Kluane (Kluane Lake) et de McCauley (région de Snag-Klutan) et à la glaciation représentée par le "Till D" dans la coupe de Tom Creek (Liard Plain). À partir de cette conclusion et grâce à une nouvelle datation sur le tephra de Old Crow, on peut croire que les glaciations de Reid, de Mirror Creek et probablement de Shakwak sont d'âge illinoien. Les fossiles de végétaux (pollen et graines) et d'insectes trouvés dans les sédiments organodétritiques associés à la date de 29.6 ka BP témoignent d'un milieu en grande partie dépourvu d'arbres. Même si les végétaux caractéristiques du bas Arctique comme les Éricacées, l'aulne et le bouleau arbustif sont rares ou absents, le pollen et les macrofossiles laissent entrevoir un climat qui n'était pas plus froid que le climat actuel de la toundra du bas Arctique, mais probablement plus sec. Les épinettes ont peut-être survécu dans la région mais seulement sous forme de bosquets et non de forêt riparienne.

Tree invasion in naturally treeless environments: Impacts of quinine ( Cinchona pubescens) trees on native vegetation in Galápagos

Impacts of plant invasions are largely scale-dependent and responses to the same exotic species may vary among communities. Since impacts caused by individual trees could anticipate consequences of a closed canopy of an invader, we studied the response of Galápagos native plants to quinine ( Cinchona pubescens) trees in two vegetation zones. Quinine has invaded >11,000 ha of Santa Cruz Island, including the Miconia- and Fern-Sedge-Zones. We analysed species composition and abundance along transects radiating from the trunks of individual quinine trees. Species richness and percentage cover decreased significantly with proximity to individual trees, and these effects were more pronounced in the Fern-Sedge Zone than in the Miconia Zone. Cover of endemic and native herb species and grass species significantly declined by 57–88% in the Fern-Sedge Zone. This was not the case in the Miconia Zone, but here the dominant endemic Miconia robinsoniana decreased by 41%. Quinine is a major driver of plant community change in both vegetation zones. The greater susceptibility of species in the Fern-Sedge Zone was ascribed to the presence of a new growth form: quinine trees in a formerly treeless environment. Species of the Miconia Zone appeared to be better pre-adapted to higher shade levels created by the Miconia shrubs. Our results emphasize the need for future control of quinine to preserve the diversity of the native Galápagos flora.

A Middle Weichselian interstadial lake deposit on Sejerø, Denmark: macrofossil studies and dating

AbstractStudies of lake sediments on Sejerø in southern Kattegat indicate a treeless arctic environment with the dwarf shrub Salix polaris, herbs and wetland mosses. The mean July temperature was around 8 to 10°C. An AMS radiocarbon age determination of a Salix twig yielded an age of around 36 000 14C yr BP, which is in accordance with previous conventional dating of bulk sediment samples. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Mammoths

Mammoths

The visibility of past trees and woodland: testing the value of insect remains

The reconstruction of woodland history is important in relation to archaeological, ecological, biogeographical and evolutionary problems, and insect remains are a significant source of relevant information. Fully natural interglacial and Holocene ‘waterlogged’ deposits assumed to have formed in woodland generally contain abundant macrofossils of both plants and insects indicative of trees. In contrast, British archaeological deposits rich in macrofossil remains of trees often lack, or contain very few, tree-associated insects. To cast light on this contradiction, assemblages of insect (Coleoptera and Hemiptera) remains from a range of modern deposits with various spatial relationships to woodland and trees have been analysed. The proportions of tree-associated insects varied greatly. There was a general trend from higher values in woodland and near to isolated trees of species supporting a rich insect fauna, to low or zero values where there were no trees. However, low values sometimes occurred in woods or near trees, so that rarity of tree-associated insects in archaeological deposits does not always carry the implication of a treeless environment. Further investigation is suggested, with emphasis on the importance of identifying isolated trees, scrub and hedges as a resource for humans and wildlife in the past.

Influence of riparian buffer width on air temperature at Whangapoua Forest, Coromandel Peninsula, New Zealand

Air temperatures were measured mid-way within a 5- and a 30-m wide riparian forest buffer and in an adjacent open clear-felled riparian area over an 11-month period. Median reductions in maximum daily air temperatures were 3.2 °C in the 5-m wide and 3.4 °C in the 30-m wide riparian forests as compared to maximum daily air temperatures in an adjacent treeless riparian area. Both forested sites had slightly warmer minimum daily air temperatures than those in the open site (median differences of 0.5 °C for the 5-m and 0.7 °C for the 30-m wide riparian forests). The 30-m buffer was slightly cooler than the 5-m buffer during the day (median difference in maximum daily air temperature of 0.3 °C) and slightly warmer during the night (median difference in minimum daily air temperature of 0.4 °C). Buffer performance in reducing the daily maximum temperature was most effective as the air temperature increased at the open site, whereas performance in reducing the minimum temperature increased as the air temperature declined. These results suggest forested riparian buffers as narrow as 5-m wide can substantially moderate air temperatures as compared to a treeless environment.

Eastern range extension ofPseudomys hermannsburgensisin Queensland

[Extract] The Sandy Inland Mouse Pseudomys hermannsburgensis and the Delicate Mouse P. delicatulus are two closely allied members of the largest genus of Australian rodents (Watts and Aslin 1981). Currently 22 species are recognised in the genus Pseudomys (Cole and Woinarski in press), though the taxonomy of this large group has variably been considered repository for species hard to classify (Watts and Aslin 1981). Taxonomic reassessment of the group is ongoing (Breed and Aplin 1995; Breed 1996; F. Ford, pers. comm, 2002. James Cook University), Pseudomys hermannsburgensis and P. delicatulus occur widely in Australia in sparsely grassed open woodlands, shrublands. Triodia grasslands and sand-plains. with P. hermannsburgensis more typical in treeless environments. Both are small to intenmediate sized (6-18 g. 55-90 mm) burrowing rodents, P. hermannsburgensis being slightly larger (Cole and Woinarski in press), Pseudomys delicatulus is widely distributed in eastern Queensland. and though P. hermannsburgensis is widespread in central Australia, it has only recently been confirmed as occurring in Queensland, despite long-held expectations of its presence (Covacevich and Easton 1974). Specimens collected in 1936 near Longreach and identified as P. minnie f1avescens (P. australis) have been recently reassigned as P. hermannsburgensis (S. Van Dyck. pers, comm, 2001. Queensland Museum) and the species has been captured frequently in long-term studies in southwest Queensland (Murray et al. 1999; Dickman et al. 1999). The two species were considered to be mutually exclusive in distribution, with P. delicatulus noted to have an almost perfect Torresian occurrence (Braithwaite and Covacevich 1995). with P. hermannsburgensis Eyrean by default. They are morphologically similar. and considered difficult to distinguish on external characteristics (Cooper 1993). Some workers have suggested distribution alone as an appropriate surrogate for identification (Covacevich and Easton 1974; Watts and Aslin 1981), Both species derived from a common ancestral Pseudomys form entering from New Guinea between 5-lO million years ago, with the subsequent evolution of P. hermannsburgensis into an inland species during a period of Pleistocene aridity and divergence (Baverstock 1982). Pseudomys delicatulus, P. novachollandiac and P. hermannsburgensis are all closely related (Baverstock et al. 1981). Despite earlier contentions of the exclusive distribution patterns of these two species, evidence exists for sympatry between P. hermannsburgensis and P. delicatulus in Western Australia (How et al. 1991) and the Northern Territory (J. Cole pers. comm. 2002, Northern Territory Department of Infrastructure, Planning and Environment). In Western Australia, both were trapped together in three sites at the Abydos-Woodstock Reserve, in very low open Eucalyptus and Acacia woodland, with Triodia spp. ground cover and sandy soils (How et al. 1991). In the Northern Territory distributions overlap in a band about 180 km wide. They are sympatric in the Mitchell Grass Downs Bioregion (Astrebla pectinata grasslands), and within 5 km of each other in the Gulf Fall Uplands Bioregion (Eucalytus leucophloia low open woodland with Trioda sp.) and in the Tanami Bioregion (mixed Triodia/Plectrachne spp. grasslands) (J. Cole pers. comm. 2002, Northern Territory Department of Infrastructure, Planning and Environment). This note reports on the opportunistic capture of P. hermannsburgensis in Queensland, identifying an eastern range extension and possible areas of overlap with P. delicatulus.

Petaloid Organs Preserved in an Arctic Plant Macrofossil Assemblage from Full-Glacial Sediments in Southeastern Minnesota

A small suite of plant macrofossils indicates that southeastern Minnesota supported subarctic to arctic vegetation 18,700 yr B.P. Fossil tepals of Polygonum viviparum are exceptionally well preserved; they occur with more fragmentary remains of Dryas integrifolia, Vaccinium uliginosum var. alpinum, and probable species of arctic Salix, S. cf. herbacea, and S. cf. arctica. The pollen spectrum from this site is dominated by Picea, Pinus, and Cyperaceae, which are typical of midwestern full-glacial sequences. Tundra-like conditions with permafrost were present in southeastern Minnesota during full-glacial time. Local environments 18,700 yr B.P. reconstructed from both physical and paleobotanical evidence include wind-swept ridge tops with thin loess, outcrops of dolostone and sandstone on valley walls, colluvial slopes, sandy to gravelly floodplains, shallow floodplain pools, wet meadows, and peaty turfs, all in a treeless or nearly treeless environment.