Lesley S. Rigg

Authorship, Collaboration, and Gender: Fifteen Years of Publication Productivity in Selected Geography Journals

In academia, publication productivity, defined as the number of peer-reviewed articles published and the frequency of citations, is a primary factor in the assessment of tenure and promotion. One of the most cited gender differences in academia is the “productivity puzzle,” which suggests that women publish less than men, thereby affecting every aspect of a womans academic career. Peer-reviewed articles published in the Annals of the Association of American Geographers (Annals) and The Professional Geographer (PG) between 1995 and 2006, and in four subdisciplinary journals between 2005 and 2009, as well as citation reports, were used to explore whether gender differences are present in publication productivity. Gender differences were evident in the proportion of women authors, the frequency of collaboration, and the number of citations across a broad range of prestigious geographic journals. For all journals studied, women were underrepresented, especially in the authorship positions that equate to notions of respect and merit. Although the number of collaborative articles increased during the study period, single-authored papers are the dominant mode of publication for both men and women for most geographic journals. The authorship patterns for frequently cited articles generally mirror those for all articles. Because the frequency of collaborative publication was high for women, the dual trends of a general increase in publication collaboration and increasing participation of women in academic geography bodes well for increased female productivity as it relates to publishing. Nevertheless, it is important to note that, currently, males as lead or single authors represent the predominant voice of geography within the journals examined in this study.

Age Structure and Regeneration Dynamics of Sugar Maple at the Deciduous/Boreal Forest Ecotone, Ontario, Canada

Sugar maple reaches its northern limit along the eastern shore of Lake Superior marking the transition from the deciduous forest of eastern North America to a predominantly boreal forest community. In light of regional warming trends over the past 100 years and projections for even warmer conditions in the future, we sought to characterize the current age structure and regeneration status of both sugar maple and boreal tree species within this ecotone zone. Within Lake Superior Provincial Park (Ontario, Canada), a series of east-west trending hills create numerous deciduous-boreal transition zones as sugar maple occupies uplands and boreal species occupy valley bottoms; then, once north of the sugar maple limit, boreal species dominate all topographic positions. Unlogged forest stands were sampled in the transition zone on ridges and slopes both north and south of the sugar maple limit. Overall tree density and basal area in sugar maple and boreal stands were similar across the ecotone, but seedling density was significantly higher in plots dominated by sugar maple. Moreover, sugar maple seedlings, but not saplings, were found slightly beyond the adult sugar maple tree hillside limit, indicating that the potential for range expansion may be limited by microclimatic variables, namely cold air drainage.

Sugar maple seedling carbon assimilation at the northern limit of its range: the importance of seasonal light

Using in situ light curves and understory seasonal light measurements the importance of canopy avoidance was evaluated for a population of sugar maple (Acer saccharum Marsh.) seedlings living at th...

Geographic Variation of Germination, Growth, and Mortality in Sugar Maple (Acer saccharum): Common Garden and Reciprocal Dispersal Experiments

If current temperature trends continue and increase as predicted by general circulation models, the persistence and migration of sugar maple (Acer saccharum) at its northern limit will become crucial to its continued existence in North America. Specifically, anthropogenic warming may affect germination success and growth of sugar maple. To evaluate this potential limitation, our study addresses two questions. The first involves a growth chamber: Do temperatures at and above (1°, 7°, and 14° C) sugar maples optimal germination temperature affect its germination? The second involves a common garden: Do sugar maple germination and subsequent growth and mortality rates show evidence of geographic variation under current climatic conditions? While sugar maple germinated successfully at 7° C in the lab, field results suggest that other environmental variables may limit its future establishment as climate changes. Germination of seeds from sugar maples northern range limit was significantly reduced under warmer conditions, and subsequent seedling mortality rates were significantly increased when grown at a more southerly latitude. Local adaptation was evident with respect to germination, survival, and growth in the field. Ultimately, results from this study further the understanding of how predicted anthropogenic climate change may affect the regeneration of sugar maple in the future.

The Impact of Seed Mix Weight on Diversity and Species Composition in a Tallgrass Prairie Restoration Planting, Nachusa Grasslands, Illinois, USA

We evaluated the effects of varying bulk seed mix weight (kg/ha) applications on species diversity and species composition of a tallgrass prairie planting established at Nachusa Grasslands (north-central Illinois). Following the application of five seed sowing weights (0, 11.2, 33.6, 56.0, and 78.5 kg/ha) containing seeds from 128 species, we censused plot species richness, stem density, and percent cover of each species in the treatment and control plots (0 kg/ha). Overall there were significant differences in vegetation composition between seed weight treatments. Low seed density plots had low species evenness, while densities of 56.0 and 78.5 kg/ha showed significantly greater evenness. Based on germination and growth, the floristic quality index (FQI) was significantly lower in the control and lighter seed weight treatments. Detrended Correspondence Analysis (DCA) ordination suggests that 56.0 kg/ha yields compositionally similar results to 78.5 kg/ha. Considering all ecological metrics analyzed, there were few differences between the 56.0 and 78.5 kg/ha treatments. The applications of 33.6 kg/ha and below led to outcomes such as greater weed abundance and lower overall vegetation cover, potentially creating future management concerns. Our findings, two years post-planting, suggest that seed weights of at least 56.0 kg/ha should be used whenever possible to maximize diversity and increase presence of species with high conservation value.

Environmental Determinants of Tree Species Distributions in Central Ontario, Canada

The ability to model forest distributions in light of anthropogenic disturbance requires a thorough understanding of how trees respond to their physical and climatic environment. The primary objective of this study is to determine how four environmental variables (elevation, latitude, slope angle, and slope aspect) affect the distribution of seven common tree species (Acer saccharum, Betula alleghaniensis, Betula papyifera, Abies balsamea, Picea glauca, Thuja occidentalis, and Acer spicatum) using both regression tree analysis (RTA) and canonical correspondence analysis (CCA) techniques. In general, within the study area, Acer saccharum, Abies balsamea, and Thuja occidentalis abundance was controlled by elevation and latitude, whereas the other species showed limited response to the measured environmental variables. While CCA and RTA showed similar patterns, RTA allows for a more nuanced evaluation of species-environment interactions. Given that the study area encompasses Acer saccharums northern limit, there were differences in the response of Abies balsamea to environmental conditions in the absence of Acer saccharum.

Regeneration Dynamics and Genetic Variability of Sugar Maple (Acer Saccharum [Marsh.]) Seedlings at the Species' Northern Growth Limit, Lake Superior Provincial Park, Canada

The transition from deciduous to boreal forest is abrupt regionally and topographically in Lake Superior Provincial Park, Ontario, Canada. The northern range limit of Acer saccharum is coincident with the forest transition to boreal forest. The goal of our study was to characterize the distribution of A. saccharum seedlings at the transition zone to determine variability in seedling demographics and genetics with topographic position and along a short north-south gradient. Seedling density, size, age, and growth were evaluated in permanent plots across the regional transition zone, and at the south-facing, ridge top and north-facing limits across the topographic transition. Growth over 5 yrs. was determined by measuring the distance between terminal bud scars, and compared with regional climate data. Genetic material was collected and analyzed from two of these sites. No significant differences were detected in density or growth of Acer saccharum across the regional transition but mean age increased and height decreased as the limit was approached. Across the topographic transition, ridge top seeding densities were greater than the south-facing or north-facing limits. Genetic variability is great with no cohort preference for topographic position detected.

Genetic Applications in Biogeography

The study of the distribution of life, of the biosphere and its respective processes, both past and present, is known as biogeography (see texts by Brown and Lomolino, 1998; Cox and Moore, 2000; MacDonald, 2003). Current biogeographical processes, biotic and abiotic, are often evaluated using ecological research methods. However, there are also historical events and evolutionary processes at play, shaping the biosphere over long time periods. Thus, it is not surprising that biogeographers draw upon methodologies from geography and the Earth sciences, including paleoclimatology, geology, and geomorphology, plus biological approaches such as paleontology and other evolutionary disciplines. A recent additional trend is the recognition that distribution data of organisms and an understanding of biogeographical processes are basic inputs needed to make biodiversity conservation decisions (Young et al., 2004). The apparent simplicity of the definition of biogeography masks the complexity of the discipline (Crisci et al., 2003). Many recent authors (e.g., Avise, 2000; Crisci et al., 2003; Price, 2003) have stressed the need for more interaction and integration among the various biogeographical approaches. This issue of Physical Geography is intended to highlight some of the work being done by biogeographers that integrate traditional methods and genetic analysis. This is particularly timely as the last two decades have seen major advances in the knowledge of how organismal molecular biology functions to create the physiological and reproductive characteristics of species and their respective populations (Stearns and Magwene, 2003; Zhang and Hewitt, 2003). The theme issue begins with several research papers that combine both ecological biogeography and genetic analysis. The first paper by Enright et al. examines the role of climate and geomorphic history in shaping the present pattern of distribution of Banksia hookeriana in southwestern Australia. The paper by Parker and Jorgensen provides an overview of the use of selected molecular markers, utilizing examples from their own genetically based biogeographic research. They stress the importance of studying genetic variation at different spatial scales, drawing on work completed on genetic variation in sand pine (Pinus clausa), an endemic species virtually restricted to Florida. As in the Enright et al. paper, Parker and Jorgensen also show how a combination of genetic analysis and additional evidence of past environments can enrich our understanding of the paleoecology of a region.