Articles
http://library2.smu.ca/xmlui/handle/01/21881
2024-03-28T18:09:17ZSpatial patterns of structural diversity across the boreal forest-tundra ecotone in Churchill, Canada
http://library2.smu.ca/xmlui/handle/01/31864
Spatial patterns of structural diversity across the boreal forest-tundra ecotone in Churchill, Canada
Vegetation structural diversity, also called structural complexity, has great effects on biodiversity and ecological processes, with higher biodiversity often observed in areas with higher structural diversity. As for other ecological variables, structural diversity is spatially heterogeneous. Thus, quantifying its spatial heterogeneity may provide clues to the spatial variation in ecological processes. We studied the spatial patterns of structural diversity in two different environments, tundra and forest-tundra ecotone, near Churchill, MB, Canada. We sampled vegetation and quantified five types of structural diversity (ground cover, herbaceous plants, woody plants, all live plants, and deadwood) along five transects, with lengths of 81-227 m, and used wavelet analysis to assess the scales of spatial pattern. We also assessed the effects of soil pH, microtopography, elevation, and distance from lakes on structural diversity. In general, structural diversity was spatially structured on a variety of scales, from 2 to 55 m, with larger scales being observed in the tundra than in the ecotone transects. In addition, structural diversity in the tundra was generally higher near lakes and in areas with a higher pH, whereas in the ecotone it increased mostly with increasing pH and microtopographic variation. Spatial heterogeneity is an important characteristic of the forest-tundra ecotone and even tundra areas that appear homogeneous are structurally diverse at a variety of scales.
Published version
2022-11-01T00:00:00ZPlant functional trait change across a warming tundra biome
http://library2.smu.ca/xmlui/handle/01/31856
Plant functional trait change across a warming tundra biome
The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature–trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.
Accepted version
2018-09-26T00:00:00ZReproduction as a bottleneck to treeline advance across the circumarctic forest tundra ecotone
http://library2.smu.ca/xmlui/handle/01/31855
Reproduction as a bottleneck to treeline advance across the circumarctic forest tundra ecotone
The fundamental niche of many species is shifting with climate change, especially in
sub-arctic ecosystems with pronounced recent warming. Ongoing warming in sub-arctic
regions should lessen environmental constraints on tree growth and reproduction, leading to increased success of trees colonizing tundra. Nevertheless, variable responses of treeline ecotones have been documented in association with warming temperatures. One explanation for time lags between increasingly favourable environmental conditions and treeline ecotone movement is reproductive limitations caused by low seed availability. Our objective was to assess the reproductive constraints of the dominant tree species at the treeline ecotone in the circumpolar north. We sampled reproductive structures of trees (cones and catkins) and stand attributes across circumarctic treeline ecotones. We used generalized linear mixed models to estimate the sensitivity of seed production and the availability of viable seed to regional climate, stand structure, and species-specific characteristics. Both seed production and viability of available seed were strongly driven by specific, sequential seasonal climatic conditions, but in different ways. Seed production was greatest when growing seasons with more growing degree days coincided with years with high precipitation. Two consecutive years with more growing degree days and low precipitation resulted in low seed production. Seasonal climate effects on the viability of available seed depended on the physical characteristics of the reproductive structures. Large-coned and -seeded species take more time to develop mature embryos and were therefore more sensitive to increases in growing
degree days in the year of flowering and embryo development. Our findings suggest that both moisture stress and abbreviated growing seasons can have a notable negative influence on the production and viability of available seed at treeline. Our synthesis revealed that constraints on pre-dispersal reproduction within the treeline ecotone might create a considerable time lag for range expansion of tree populations into tundra ecosystems.
Published version
2018-07-02T00:00:00ZUnderstanding patterns of biodiversity and ecosystem functioning of forested wetlands in Atlantic Canada: implications for conservation
http://library2.smu.ca/xmlui/handle/01/31854
Understanding patterns of biodiversity and ecosystem functioning of forested wetlands in Atlantic Canada: implications for conservation
Herein we present a selection of papers highlighting the importance of forested wetlands in Atlantic Canada. This special issue is a product of a research program on forested wetlands conducted from 2016 to 2019 and funded in part by the Atlantic Ecosystems Initiative of Environment and Climate Change Canada, Government of Canada. Although forested wetlands in Atlantic Canada have been relatively understudied, the little research available suggests these are bio-diverse ecosystems supporting rare species.
Published version
2021-08-20T00:00:00ZData on vegetation across forest edges from the FERN(Forest Edge Research Network)
http://library2.smu.ca/xmlui/handle/01/31794
Data on vegetation across forest edges from the FERN(Forest Edge Research Network)
Many studies have focused on vegetation across forest edges to study impacts of edges created by human activities on forest structure and composition, or patterns of vegetation at inherent natural edges. Our objective was to create a database of plant-related variables across different types of edges from various studies (mainly from across Canada, but also in Brazil and Belize) to facilitate edge research. We compiled data on vegetation along more than 300 transects perpendicular to forest edges adjacent to clear-cuts, burned areas, bogs, lakes, barrens, insect disturbances, and riparian areas from 24 studies conducted over the past three decades. Data were compiled for more than 400 plant species and forest structure variables (e.g., trees, logs, canopy cover). All data were collected with a similar sampling design of quadrats along transects perpendicular to forest edges, but with varying numbers of transects and quadrats, and distances from the edge. The purpose for most of the studies was either to determine the distance of edge influence (edge width) or to explore the pattern of vegetation along the edge to interior gradient. We provide data tables for the cover of plant species and functional groups, the species and size of live and dead trees, the density of saplings, maximum height of functional groups and shrub species, and the cover of functional groups at different heights (vertical distribution of vegetation). The Forest Edge Research Network (FERN) database provides extensive data on many variables that can be used for further study including meta-analyses and can assist in answering questions important to conservation efforts (e.g., how is distance of edge influence from created edges affected by different factors?). We plan to expand this database with subsequent studies from the authors and we invite others to contribute to make this a more global database. The data are released under a CC0 license. When using these data, we ask that you cite this data paper and any relevant publications listed in our metadata file. We also encourage you to contact the first author if you are planning to use or contribute to this database.
Published version
2023-05-11T00:00:00ZLandscape composition regulates the spillover of beneficial insects between forest remnants and adjacent coffee plantations
http://library2.smu.ca/xmlui/handle/01/31793
Landscape composition regulates the spillover of beneficial insects between forest remnants and adjacent coffee plantations
Cross-habitat movements are crucial for persistence of beneficial insects in agricultural landscapes; however, much remains unknown on how landscape structure affects the spillover of beneficial insects between crop and non-crop habitats. To estimate the effects of landscape structure on the spillover of beneficial insects we sampled predatory wasps in pairs of forest remnants and adjacent coffee plantations along a gradient of landscape composition and configuration. We used dissimilarity indices to estimate wasp spillover and we assumed that high dissimilarity means less flow (and thus less spillover) between forest and coffee habitats. We collected a total of 9847 wasps classified into 75 species and 23 genera. Wasp dissimilarity between habitats decreased with increasing forest cover in the surrounding landscape and did not respond to landscape diversity, edge density or pesticide usage. Our findings suggest that wasps forage in coffee plantations but seem to rely on forest remnants to find unmanaged nesting sites and a constant supply of resources that are not available in the agricultural matrix, and are neither in landscapes with high compositional diversity or edge density. Therefore, forest conservation and restoration should be incorporated in agro-environmental schemes designed to improve the spillover of beneficial insects and provision of ecosystem services within coffee farmlands.
Published version
2022-04-01T00:00:00ZApplication of DEI and MEI indices to evaluate the effect of fragmentation in oak habitats on species diversity and soil chemical characteristics
http://library2.smu.ca/xmlui/handle/01/31792
Application of DEI and MEI indices to evaluate the effect of fragmentation in oak habitats on species diversity and soil chemical characteristics
In order to introduce and application of DEI (Distance of Edge Influence) and MEI (Magnitude of Edge Influence) indices to determine the distance of edge effect and intensity of the edge effect on herbaceous species and soil chemical properties, Three forest fragments (under 10 hectares) from oak forests of Kermanshah province were selected with similar conditions in terms of slope, direction and altitude. In each fragment three transects were established from the edge to the forest interior. Measurements of vegetation and soil variables were collected at 0 (edge), 25, 50, 100, 150 m along each transect. The results showed that MEI index values were positive for soil variables (except nitrogen, organic carbon and pH). The values of this index were also positive for species richness, Shannon-Wiener diversity and Evenness. DEI index value was 25 m for soil variables except pH and 50 m for diversity indices. The influence of edge on species richness, Shannon-Wiener diversity and Evenness was significant. Soil variables (except phosphorus) did not show significant differences at different distances from edge. Also, changes in species richness and soil chemical properties were observed in 0-50 m from edge. Totally, in sparse oak forests, fragmentation and edge effect had influence on species richness and soil chemical properties.
Published version
2021-12-01T00:00:00ZEdge influence on herbaceous plant species, diversity and soil properties in sparse oak forest fragments in Iran
http://library2.smu.ca/xmlui/handle/01/31791
Edge influence on herbaceous plant species, diversity and soil properties in sparse oak forest fragments in Iran
Forest edges have been well studied in temperate and tropical forests, but less so in open canopy forests. We investigated edge influence on plant species diversity and soil properties in sparse oak forest fragments. Data were collected along three transects from the edge to the interior of three small (under 10 ha) and three large (over 10 ha) oak forest fragments in Kermanshah Province, Iran. We measured herbaceous plants (<0.5 m in height) and soil attributes at 0 (forest edge), 25, 50, 100 and 150 m. We quantified species diversity using the Shannon index, used rarefaction to compare species richness between two different sizes of fragments and applied non-metric multidimensional scaling ordination to investigate the variation in species composition. We estimated the distance of edge influence using randomization tests. Generalized linear mixed models with post-hoc Tukey's HSD tests were used to assess the effects of distance from edge and fragment size on diversity and soil properties. We found greater species richness, diversity and evenness at the edge of both small and large fragments and lower nitrogen and organic carbon at the edge compared to the interior of large fragments, with most changes within 50 m of the edge. Species composition, organic carbon and total nitrogen were significantly different between small and large fragments. Our findings of significant edge influence on herbaceous plants and soil properties in these sparse forests provide a significant contribution to the literature on edges, especially in relation to herbaceous plants.
Published version
2021-09-04T00:00:00ZPhylogenetic analysis of two single-copy nuclear genes revealed origin and complex relationships of polyploid species of Hordeum in Triticeae (Poaceae)
http://library2.smu.ca/xmlui/handle/01/30985
Phylogenetic analysis of two single-copy nuclear genes revealed origin and complex relationships of polyploid species of Hordeum in Triticeae (Poaceae)
Two single-copy nuclear genes, the second largest subunit of RNA polymerase II (<i>RPB2</i>) and thioredoxin-like gene (<i>HTL</i>), were used to explore the phylogeny and origin of polyploid species in <i>Hordeum</i>. Our results were partly in accord with previous studies, but disclosed additional complexity. Both <i>RPB2</i> and <i>HTL</i> trees confirmed the presence of <b>Xa</b> genome in <i>H. capense</i> and <i>H. secalinum</i>, and that <i>H. depressum</i> originated from <i>H. californicum</i> together with other American diploids, either <i>H. intercedens</i> or <i>H. pusillum</i>. American diploids solely contributed to the origin of <i>H. depressum</i>. The Asian diploids, either <i>iH. bogdanii</i> or <i>H. brevisubulatum</i>, contributed to the formation of American polyploids except <i>H. depressum</i>. <i>RPB2</i> and <i>HTL</i> sequences showed that <i>H. roshevitzii</i> did not contribute to the origin of American tetraploids. Our data showed a close relationship between the hexaploids <i>H. procerum</i> and <i>H. parodii</i> and the tetraploids <i>H. brachyantherum</i>, <i>H. fuegianum</i>, <i>H. guatemalense</i>, <i>H. jubatum</i>, and <i>H. tetraploidum</i>. The involvement of the diploid <i>H. pusillum</i> and the tetraploid <i>H. jubatum</i> in the formation of <i>H. arizonicum</i> was also indicated in the <i>HTL</i> phylogeny. Our results suggested a possible gene introgression of <b>W-</b> and <b>P-</b>genome species into the tetraploid <i>H. jubatum</i> and the hexaploid <i>H. procerum</i>.
Accepted version
2017-01-17T00:00:00ZCommunity well-being: The impacts of inequality, racism and environment on a Brazilian coastal slum
http://library2.smu.ca/xmlui/handle/01/30932
Community well-being: The impacts of inequality, racism and environment on a Brazilian coastal slum
This article applies the 3-dimensional well-being lens (based on material, relational and subjective dimensions of well-being) to examine the factors that affect well-being in a slum community (Vila dos Pescadores, in the city of Cubatão, Southeast Brazil). This well-being framework proves useful in understanding how community well-being is impacted by several negative factors: the perceptions of slums, the presence of systemic racism and growing inequality, and a range of environmental impacts arising from industrial and urban pollution, and environmental disasters. Within this mix of environmental and social impacts are links between poverty and exposure to environmental hazards, and effects of environmental racism. On the positive side, these threats to community well-being are countered to some extent through targeted measures carried out by the community association and its partnerships, and through beneficial governmental policy measures. Together, these responses help to reduce the detrimental effects of an unhealthy and dangerous environment, and of social concerns such as exclusion, poverty, urbanization and inequality. Key to the success of response measures are the contributions of the community leadership to improve the well-being of slum-dwellers by counterbalancing the effects of racism and social inequality, and implementing social programs and community facilities, thereby filling the gaps created by a lack of state support to slums. These actions illustrate what impoverished communities can do to improve livelihoods and well-being, and to combat problems such as environmental degradation and racial discrimination. This article also draws lessons for improving well-being analysis, particularly in slum communities, through a greater focus on (1) collective well-being and a community-focused view of well-being, (2) impacts of racism and inequality, and (3) interactions between community well-being and community leadership.
Published version
2019-03-01T00:00:00Z