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Exploring the Mid-Late Holocene interactions between ecological and climate variations in semi-arid areas such as Songnen grasslands (northeastern China) provide insights into how future vegetation changes and hydrological variations may have an impact on semi-arid ecosystems, in general. In this study, we present a high-resolution palaeoecological dataset covering the past 7300 years. For this purpose, a peat section has been sampled from the shore of Dabusu lake situated in the southwestern part of the Songnen grasslands. We use pollen analyses to reconstruct the regional and local vegetation dynamics, and measure TOC (total organic carbon) and the degree of peat humification to study changes in regional and local biomass. Diatom analysis, grain size analysis, and CaCO3 contents are used to assess the water-table fluctuations of the Dabusu peatlands. The results show that from 7300 to 6000 cal BP, Dabusu peatlands were characterized by grasslands, dominated by Poaceae plants and high-water level. From 6000 to 910 cal BP, forest-steppes and dry-steppes dominated in the region alternatively. The water level of Dabusu peatlands experienced relatively low levels following an earlier rapid decline around 6000–5100 cal BP. Then after a slight increase between 5100 and 4000 cal BP, it remained at a relatively low level until 910 cal BP. After 910 cal BP, steppe vegetation dominated in the region and the water level of Dabusu peatlands slightly rose. By comparing these features with regional climate change, we show that EASM circulations might be the main driving forces controlling the regional paleovegetation dynamics and hydrological variations. This outcome is critical for the understanding of the long-term interactions between vegetation, hydrology, and climate of mid-latitude semi-arid grasslands.

Ecological responses to past climate change as determined from palaeorecords offer insights into responses that may accompany future climate change. In arid and semi‐arid lands, the interactions between regional vegetation and climate change are not yet well understood, partly due to a lack of suitable palaeovegetation proxies that can provide accurate and continuous tracers for past vegetation dynamics. To gain a better understanding of long‐term vegetation dynamics, this study employs a multiproxy approach applied to sand‐palaeosol sediments of northeastern China's Songnen grasslands. Phytolith analyses and data on the stable carbon isotope composition (δ¹³C) of organic matter are used to reconstruct palaeovegetation composition, namely, the changing abundance of C₃ and C₄ species, whereas a geochemical weathering index (Fed/Fet ratios) tracks past East Asian summer monsoon (EASM) intensity. The phytolith assemblages and indices and δ¹³C of the soil indicate that C₄ species' abundance has been increasing in the Songnen grasslands since the mid‐Holocene, although C₃ vegetation is still dominant. Statistically significant negative correlations between the δ¹³C data and Fet/Fed ratios suggest that continuous weakening of the EASM since the mid‐Holocene may be responsible for the ¹³C‐enrichment of the sediments in the Songnen grasslands. Field vegetation surveys, modern topsoil phytoliths and δ¹³C calibration data indicate that the expansion of C₄ species since the mid‐Holocene is mainly due to their ability to cope with aridity when growing season temperature is not undergoing a significant decrease. Future precipitation decreases in arid and semi‐arid lands should make C₄ species more competitive in the grasslands of northeastern China. Highlights A continuous grassland landscape history is reconstructed from a sand‐palaeosol sequence via phytolith analysis. Multiple independent approaches were used to reconstruct past EASM intensity and palaeovegetation patterns. Phytolith and δ¹³C analyses indicate an increase in C₄ species since the mid‐Holocene. Aridification drives the increase in C₄ species within the grassland ecosystem.

The Songnen grasslands were traditionally thought to be dominated by Artemisia and Chenopodiaceae plants as early as the late Pleistocene. However, increasing evidence has called that interpretation into question. To shed new light on the paleovegetation evolution of the arid and semi-arid steppe in North China, phytolith assemblages preserved in the region’s sand-paleosol sequence (section Daike) are used as a proxy for paleovegetation structure. Results show that both the sand and paleosol layers in the Songnen grassland sections contain well-preserved phytoliths attributed to different families of grass. This is the first direct evidence of the nature of the vegetation that existed during the sandy layer episodes. Moreover, the phytolith evidence represented in the samples indicates that plant successions happened within the subfamilies of Poaceae through the time. Referring to phytoliths in modern plants and topsoils, and using statistical analyses, we propose that phytolith assemblages in the section Daike originated from Poaceae-dominant communities rather than an Artemisia-Chenopodiaceae ecosystem. The phytoliths, and evidence from the historical and modern pollen-vegetation relationships, lead to rejection of the hypothesis of a past widespread Artemisia-Chenopodiaceae ecosystem in the Songnen grasslands. Using published radiocarbon and thermoluminescence data, it is proposed that the present Poaceae-dominated grasslands developed as early as the early Holocene. This study also highlights the usefulness of phytolith analysis in paleovegetation reconstruction in arid and semi-arid lands.

Peatlands located at the northern edge of the East Asian monsoon (EAM) are well placed to provide a terrestrial record of past climate and hydrological changes for this globally sensitive region. Here we present a middle to late Holocene, diatom-derived water-table records from a peatland in the Greater Hinggan Mountains, northeastern China. An age-depth model was achieved through AMS14C dating and Bayesian piece-wise linear accumulation modelling. The diatom-based water-table reconstructions show that the peatland water-table rose from 5100 to 3500 cal. yr BP, but fell approximately 3500 cal. yr BP. From about 2800 to 1500 cal. yr BP, the peatland water-table stabilized. After about 1500 cal. yr BP, several rapid hydrological shifts, which correspond with global climate anomalies such as ice-rafted debris (IRD) events, were registered in the reconstructed water-tables. Compared with other paleoclimate records in East Asia, the general trend of peatland water-table fluctuations follows the variations in the East Asian summer monsoon (EASM) intensity. Spectrum analysis of the water-table profile yielded a statistically significant periodicity of 470-year that may be related to the “~500-year” inherent solar irradiation cycles. In addition, positive correlation between the peatland water-table levels and cosmic-isotope-reconstructed sunspot numbers underscores the role of the sun in regulating hydrological processes in the EASM margin area. The data suggest that the regional climate and hydrological variations at the EASM margin were first triggered by changes in solar output, but may have been amplified by interactions with oceanic and atmospheric circulations.

Total organic carbon (TOC) and inorganic carbon (carbonates) are important soil factors and paleoenvironmental proxies used worldwide. During past decades, several different methods have been proposed for determining these parameters from various sediment archives. Although the automatic elemental analyzer is gradually replacing the traditional quantification methods, it is critical to assess the reliability of all currently used methods to ensure accurate regional comparisons, carbon stock estimations and long-term carbon-cycle dynamics modelling. In this study, three most commonly used methods for determining TOC and carbonate content are compared using sediment samples from a sand-paleosol sequence located in northeastern China. Pearson's correlation between results of the different TOC and carbonate quantification methods produced high correlation coefficients, confirming substantial consistency among them. The automatic carbon analyzer yielded more accurate values with smaller uncertainties, while results of the general chemical method and loss-on-ignition (LOI) produced relatively reliable values with more data variability. Meanwhile, combustion at 500 °C to quantify the TOC content yielded significantly higher values than the automatic carbon analyzer and chemical methods, indicating that LOI method is not as reliable as previously thought. We attribute the overestimation to unsuitable SOM to TOC conversion factors and/or the presence of volatile minerals in the samples. In contrast with other studies, chemical wet oxidation of the sand-paleosol sediments did not significantly overestimate TOC, which commonly occurs in modern soils and lacustrine sediments. Our results suggest that the reliability of different methods for measuring carbon content could be affected by the sediment's origin and environment. Assessment of the results of the different TOC and carbonate quantification methods on additional types of sediment is needed so that researchers can use the most appropriate method for their study and make appropriate paleoenvironmental reconstructions given the sediments and methods used.

In their comment, Oviatt et al. (this issue) criticize and dismiss our recent paper (Nishizawa et al., 2013) by arguing that it contains misinterpretations and unreliable radiocarbon ages, and therefore that our findings will confuse many people trying to understand the lacustrine chronology of the Bonneville basin. Their comment, however, does not present evidence to substantiate their criticisms against our paper. Oviatt et al. attribute statements to the paper that are not found in it, and their attempt to re-graph the radiocarbon ages omits 13% of our data. Numeric ages that Oviatt et al. contend are conflicting either are not or are not as problematic as those commenters claim. Comparisons of our lake-interval interpretations with sediment-core data likewise do not show the contradictions that Oviatt et al. claim. In essence, Oviatt et al. seem to advocate complete dismissal of all of our numeric ages and lake-size interpretations regarding MIS 3 on the basis of one tufa age. The following sections identify the incorrect information presented in the comment by Oviatt et al., review the complete set of numeric ages for the contested intervals, and respond to the implication that our late colleague, mentor, and coauthor, Donald R. Currey, did not actively participate in this research.

Lacustrine shoreline depositional features in the Bonneville basin, western North America, were investigated to chronicle paleolake expansion and contraction in response to climate change. Based on stratigraphy, sedimentology, geomorphology, and radiocarbon dating, this study identifies multiple intermediate- to large-lake intervals during Marine Isotope Stage 3 and the Last Glacial Maximum. Timing and magnitude of the Bonneville basin lake size change are compared with those of hemispheric-scale climate-change events reported from the Greenland ice sheet, southwestern North America winter precipitation, and East Asian monsoon δ 18 O records. The amount of precipitation received by surface water systems in the Bonneville basin appears to have increased significantly during the Greenland stades throughout the last half of MIS 3 and early MIS 2. The lake also underwent rapid, large amplitude oscillations during the Last Glacial Maximum.

This paper reports on recent multiproxy research conducted to determine the chronology of lake-level fluctuations recorded in sediments from a natural exposure at a classic Bonneville basin site. Grain size, carbonate percentage, magnetic susceptibility, amount of charcoal, and diatom community composition data were collected from the 16 lacustrine units that compose the 122 cm stratigraphic column in Stansbury Gulch. Trends observed in the measured proxies reveal several significant changes in lake level, and thereby effective moisture, over the approximately 14,500 yr time span represented by the sediments. Results (1) verify the effectiveness of the multiproxy approach in Bonneville basin studies, which has been underutilized in this region, (2) reaffirm the double nature of Lake Bonneville's Stansbury oscillation, (3) suggest a previously undocumented post-Gilbert highstand of Great Salt Lake, and (4) identify possible teleconnections between climate events in the Bonneville basin and events in the North Atlantic at about 20,500 and 7500 14C yr BP.

In 1980, as a geomorphology graduate student, I wrote to five senior women geomorphologists in North America and Great Britain requesting information regarding their careers and career experiences. At that time, the number of professionally estab- lished women in geomorphology in those countries was very small. The sample consisted of three professors (Borowiecki, King, and Morisawa), one associate professor (Macpherson), and one research scholar (Mammerickx), who had received their doctoral degrees in geomorphology between 1949 and 1966. Each responded to the request for information with a letter and a curriculum vitae. The extent to which they discussed their views regarding, and their personal experiences as, women in geomorphology in the mid-20th century varied widely, as did the amount of biographical information that each provided. Nevertheless this archive reveals some commonalities in their backgrounds, experiences, and views about women in geomorphology. Three of the respondents reported experiencing discrimination early in their careers, while two made career adjustments because of family commitments. Overall the women generally credited their success as professional geomorphologists to a deep appreciation of nature or landscape and to considering themselves as geomorphologists who happened to be women. (Key words: geomorphology, women geomorphologists, history of geomorphology.)

This research investigates the impact of off-road vehicles (ORVs) on sediment dynamics and compaction in the forested hillslope terrain of southeastern Ohio. A dense network of ground-height change, penetrometer resistance, and penetrometer depth mea- surements was collected from trails and trail-adjacent forest land at four ORV and, for comparison, two non-ORV trail study sites (hiking, horse-riding). Repeat measurements were made at the height of the ORV season, at the end of the ORV season, and near the end of the off-season. Separate statistical comparisons of ground-height change and pen- etrometer observations for forest versus trail locations, ORV versus non-ORV study sites, and one time period versus another reveal compaction on all trails, significant surface compaction on the ORV trails, and considerable sediment flux on both the trails and the adjacent forest land at the ORV sites. This flux includes sediment transfer during the riding season from the ORV trails to the adjacent forest land by wash and tire throw. Net erosion that occurred on the ORV trails during the studied part of the riding season was quantita- tively offset by off-season aggradation, but the system is primarily one of sediment through-put. Considering the entire riding season, erosion rates on the ORV trails may be as high as 0.11 m 3 /m 2 /yr. (Key words: off-road vehicles (ORVs, ATVs, OHVs), landscape disturbance, recreational impacts, national forest, sediment flux, tire throw, erosion rates.)

The history of geomorphology can be a valuable tool for educating students of geomorphology. The largest and most available record of what geomorphologists thought and did in the past is their original published work. Also available are some fine papers on the history of geomorphology that review and analyze primary sources and past events in the discipline in order to generalize, explain trends, and reveal historical associations. Interest in the history of the discipline varies widely, of course, among geomorphologists. Nevertheless, several educational benefits, in addition to explaining the academic affiliation of geomorphology with two separate disciplines, can be derived from incorporating the history of geomorphology into university-level geomorphology courses. History is a popular subject,and presenting some geomorphic concepts using a historical approach can help to maintain or stimulate student interest. Because of the tendency for older literature to contain more qualitative description and methodological detail than more recent literature, undergraduate students may comprehend some concepts better from older papers. By reading the original literature, students determine for themselves what previous practitioners accomplished, rather than relying solely on the interpretations of others. Reading original literature also helps students realize that older does not mean less intelligent, and that like the critical reading of recent geomorphic literature, the critical reading of historic geomorphic papers can provide a wealth of new research ideas. A thematic set of the historic literature can be used to demonstrate to students the scientific method, the origin, testing, and evolution of hypotheses, how explanations develop in this field, and that science proceeds through individuals working in a sociological context. Including history of geomorphology in the curriculum helps to place contemporary research in the perspective of the past as well as the perspective of the future.

Deposits of a transgressive-phase Lake Bonneville stillstand or oscillation are found just below the elevation of the regressive-phase Provo shoreline at numerous exposures throughout the Bonneville basin. Existence of these subProvo shoreline deposits provides a new explanation for the massive size of Provo depositional and erosional landforms, which can no longer be explained by a long stillstand at the Provo shoreline. Provo coastal landforms are large because they are superimposed on subProvo landforms. Results also help to clarify divergent interpretations regarding the relative age of the Provo shoreline and the number of times it was occupied by the water plane. Occupation of approximately the same level during both the transgressive and the regressive phase of Lake Bonneville may be coincidental, or it may indicate that a bedrock sill controlled outflow at subProvo as well as Provo time. Rise to the Bonneville level could have occurred after massive slope failure plugged the outlet pass.

In 1983 and 1993 over 1,400 school children in San Marcos, Texas, were surveyed concerning their attitudes toward geography as a school subject and as one of the social studies. Although on average the children in both years considered geography their least favorite on a list of school subjects and gave it a mediocre ranking compared to other social studies, some statistically significant improvement in the popularity of geography occurred over the decade. This research tentatively associates this increased popularity with more active learning environments.

This paper evaluates the utility of the shoreline preservation index (s.p.i.) for estimating the age of late Pleistocene palaeolake shorelines, the relative influence of various factors on shoreline preservation, and whether shoreline preservation varies significantly with shoreline aspect. Sampled shorelines from the 3300 km2 study area, which includes the Skull, Tule and Puddle Valley portions of the Lake Bonneville basin, range in age from approximately 26 to 12 ka. Their total s.p.i. values range from 23 to 69 per cent, average 46 per cent, and do not vary significantly with shoreline aspect. The data from Skull and Tule Valleys, where studied shorelines are of known age, are analysed first in order to determine if there are statistically significant associations between variables representing shoreline preservation, age, degree of geomorphic development and duration of subaerial exposure. Pairwise correlation is then repeated using observations from all three valleys in order to determine how data from the Puddle Valley shorelines, whose hypothesized ages are not supported by radiocarbon analyses, affect the results. Results show that s.p.i. is useful as a relative-age dating tool, that the postulated ages of the Puddle Valley shorelines are ordinally correct, and that geomorphic development is not an important influence on the preservation of these late Pleistocene shorelines. The relative importance of shoreline age and the relative unimportance of duration of subaerial exposure with respect to shoreline preservation suggest that subaqueous processes play a more substantial role in shoreline obliteration than is generally suggested.

Lake Bonneville occupied a series of connected topographically-closed structural basins in the eastern Great Basin from about 30 ka to 12 ka. The following synthesis of Lake Bonneville history is based on a critical evaluation of the stratigraphic and geomorphic contexts of 83 radiocarbon ages of a variety of samples, including wood, charcoal, dispersed organic matter, mollusk shells, and tufa. The lake began to rise from levels close to average Holocene levels after about 28 ka. By 22 ka it had transgressed approximately 100 m; between 22 and 20 ka it regressed about 45 m in the Stansbury oscillation and the Stansbury shoreline was formed. Transgression after 20 ka proceeded in two phases—a rapid phase from 20 to 18 ka, and a slower phase from 18 to 15 ka. The lake overflowed intermittently at its highest level (the Bonneville shoreline) from about 15 to 14.5 ka, then catastrophically dropped 100 m during the Bonneville Flood to the level of the Provo shoreline, which it occupied until about 14 ka. Subsequent closed-basin regression was rapid and complete by 12 ka, and was followed by a modest transgression to form the Gilbert shoreline between 10.9 and 10.3 ka. The Lake Bonneville record is an accurate proxy of the changing water balance in the Bonneville basin during the late Pleistocene, although the nature of the climatic changes during this period are still uncertain.

This paper historiographically analyzes the enunciation of the American, systemic-process geomorphology paradigm in the mid-20th century, with particular focus on notions concerning Gilbert and systems. Selected contributions by Strahler, Hack, and Chorley are emphasized because of their influential roles in pronouncing and elaborating process geomorphology. Articulation of the emerging paradigm contributed to the installation of Gilbert as its figurehead and established systems analysis as a fundamental tool. Gilbert was an appropriate figurehead for the new paradigm because he had worked outside of the Davisian paradigm during the Davisian era, had done process geomorphology, had applied the method of systems analysis, and was very well respected. Identifying Gilbert as the archetypal process geomorphologist helped sanction the process paradigm, distance it from Davisian geomorphology, and ease the paradigm change. Strahler's portrayal of Gilbert, however, incorrectly implies that Gilbert had actively advocated process geomorphology in a competition with Davis and the Davisian geographical cycle. Gilbert, Strahler, and Hack each applied the thermodynamically based method of systems analysis to process geomorphology, but Chorley advocated von Bertalanffy's philosophically based general system theory instead. Gilbert, Strahler, and Hack did not apply general system theory to geomorphology, as Chorley suggested they had. Recognizing these and other notions as revisionist aids in recovering a truer understanding of the actual contributions of people important in the history of geomorphology.

Geomorphic and stratigraphic patterns, which in lacustrine geoscience differ more in etymology than substance, are the evidence by which hydrographic patterns and underlying hydroclimatic and tectonic patterns are reconstructed in hemiarid lake basins. Regional and local geomorphic patterns are equally important: regional geomorphic patterns are the predictive basis for making local geomorphic observations, and local patterns are the observational basis for building and testing regional models.

Lakes have long been recognized as being rich storehouses of environmental information. A lake basin collects water, but also sediment, much of which has been weathered and transported via fluvial processes from the near and far reaches of its drainage basin. The amount of water held in a lake is recorded on the landscape in coastal erosional and depositional landforms created at the water’s edge. The sediments deposited on the bottom of the lake can be clastic, geochemical, or biogenic, and include materials derived within the standing water body itself, such as through coastal erosion, chemical precipitation, or biogenic concentration, as well as those delivered to the lake from the surrounding drainage basin. In most cases only a small percentage of a lake’s sediment load is delivered from outside of the drainage basin as aeolian fallout. Because, under natural conditions, climate is the main determinant of the amount of water in a lake and because it influences some important characteristics of the lacustrine sediments and biota, changing climatic conditions are represented in the suites of abandoned shorelines and accumulations of sediments left by the lake over time (Fig. 25.1). This archival property makes the geomorphic and sedimentologic evidence of present and past lakes valuable as environmental and palaeoenvironmental indicators. Such evidence from late Quaternary palaeolakes, in fact, ranks among of the most complete and accessible sources of palaeoclimatic proxy

Lakes and other mappable bodies of standing water occur at the atmosphere-lithosphere interface. Over short time intervals, water body configurations (hydrography) are directly responsive to atmospheric (hydroclimatic) forcing. Over longer intervals, hydrography also reflects lithospheric (tectonic and volcanic) forcing. In turn, hydrographic patterns in lake basins strongly influence and even control many geomorphic and stratigraphic patterns (e.g. Mabbutt 1977, pp. 180–214). These linked patterns (hydro-climatic + tectonic → hydrographie → geomorphic + stratigraphie) make lakes and kindred water bodies superb instruments for gauging environmental change and recording palaeoenvironmental history.

Accounts of the paradigmatic history of twentieth century American geomorphology traditionally describe Gilbert and Davis in anthithetical terms. That characterization partially misrepresents Gilbert, who was a geographer and an educator as well as a geologist and an investigator. Viewing the Gilbertian paradigm as the antithesis of the outmoded Davisian paradigm may have facilitated the acceptance of Gilbert's approach, but extending the dichotomous generalization to other aspects of Gilbert and Davis impedes full appreciation of Gilbert's contributions.

Hydrographically closed basins are numerous in arid regions largely for reasons related to climate (Langbein 1961). Whether desert basins originally formed by structural, volcanic, meteoritic, aeolian, fluvial, biologic, or other processes (Hutchinson 1957, Reeves 1968), they can generally be maintained for long periods if accumulation of surface water is insufficient in volume and duration to establish permanent overflow to externally drained fluvial systems. Other factors that can extend desert-basin longevity include high basin relief, continuance of depression-forming processes, and slow rates of sedimentation. As a result, closed desert basins are especially well developed in arid regions of active extensional tectonics, such as the Great Basin section of the Basin and Range physiographic province in western North America.