David R. Clements

David R. Clements
Trinity Western University · Department of Biology

Ph.D.

About

100
Publications
32,022
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2,477
Citations
Additional affiliations
August 1994 - present
Trinity Western University
Position
  • Professor
August 1994 - present
Trinity Western University
Position
  • Professor
August 1994 - present
Trinity Western University
Position
  • Professor

Publications

Publications (100)
Chapter
Undesirable plants continue their presence in agricultural and managed ecosystems despite a wide variety of management techniques developed to eliminate them. We definerefer to weed persistence as “the ability of undesirable plant species to continually evolve, survive, thrive, and reproduce under a variety of natural and anthropogenic selection pr...
Chapter
Signs that weeds are exploiting climate change include shifts in distribution due to latitudinal temperature shifts, changes in precipitation patterns, and increased frequency of extreme climate events. Poleward shifts in weed distribution have been well documented in North America, Europe, and Oceania in response to temperature changes. Physiologi...
Chapter
Humans and weeds share a long history over which various technologies have been employed to manage weeds. Because weeds are still a very serious issue in the twenty‐first century, it is clear that the persistence of weeds represents a daunting combination of challenges. The invention of synthetic herbicides, which diminished the labor component of...
Preprint
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Background: Littleseed canarygrass (Phalaris minor Retz.) is one of the most troublesome invasive weeds infesting winter crops in Yunnan Province, China. Our previous study found that rapeseed (Bassica napus L.) was a logical candidate crop to control littleseed canarygrass in agroecosystems. Nitrogen (N) could impact plant community composition by...
Article
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Because cropping systems can greatly affect the establishment and spread of alien species populations, the design of cropping systems to control invasive weeds is an important approach for invasive species management in agro-ecosystems to avoid excessive increases in other control measures such as herbicides. The annual weed Phalaris minor Retz. (P...
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Sweet potato (Ipomoea batatas (L.) Lam.) is a logical candidate crop to suppress invasive plants, but additional information is needed to support its potential application as a suppressive ground cover. The current study utilized a de Wit replacement series incorporating five ratios of sweet potato grown in the field in combination with one of thre...
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The decline of the northern red-legged frog, Rana aurora, in the Pacific Northwest has been attributed to invasive species, habitat loss, and climate change. Rana aurora lay eggs on emergent vegetation, and larval development occurs in shallow, often ephemeral wetlands. In 2015 and 2016 we investigated how habitat and water quality parameters influ...
Article
The hybrid knotweed Reynoutria × bohemica Chrtek & Chrtková exhibits greater genetic variation than its parents. We developed methodology for and tested for glyphosate resistance in two Bohemian knotweed populations using rhizome fragments. There was no difference in LD50 (p = 0.3030; F = 1.067) between the populations and no evidence of resistance...
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Background and objectives: The biocontrol agent Aphidius gifuensis has widely been released and applied since 1997 to control Myzus persicae in tobacco fields of Yunnan Province, southwestern China, but its ecological effects on the local insect community and diversity have not been described. Biological control agents may effect a diversity of or...
Article
Two related species of Hedera spp. exist throughout Canada: English Ivy (Hedera helix L.) and Irish Ivy [Hedera hibernica (G. Kirchn.) Bean]. These species are difficult to distinguish taxonomically and clear distinctions are not always made in the literature, so we largely discuss them as a single taxon in this account. Ivy is an evergreen perenni...
Article
Daphne (Daphne laureola L.) is a perennial evergreen shrub native to Eurasia and northern Africa. Introduced to North America as an ornamental shrub, the plant has readily absconded gardens and can now be found throughout suitable habitats on both the east and west coasts of the continent. In Canada, daphne has naturalized in southwestern British C...
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A laboratory bioassay was conducted to determine the allelopathic potentials of aqueous extracts from either roots or leaves of seventeen sweet potato [Ipomoea batatas L. (Lam)] cultivars (SP0, SP1, SP2, SP3, SP4, SP5, SP6, SP7, SP9, SP10, SP11, SP13, SP14, SP15, SP16, SP18, and SP19). Most inhibitory rates on Lactuca sativa calculated for leaf or...
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In this study, effects of temperature, light and their interactions on allelopathic effects and the functional traits specific leaf area (SLA) and stem mass fraction (SMF) of different allelopathic potential rice accessions at different growth stages were analyzed. The main results were as follows: Allelopathic responses to temperature and light va...
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Background and objectives: Sweet potato [Ipomoea batatas (L.) Lam] is an important locally grown cash crop in China; it was demonstrated to suppress the invasive plant Mikania micrantha (M. micrantha) H.B.K through strong competitiveness, but its allelopathic effects on this weed were unknown. The present study aimed to explore the allelopathic po...
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As researchers and land managers increasingly seek to understand plant invasions and the external (climate) and internal (plant genetics) conditions that govern the process, new insight is helping to answer the elusive question of what makes some invasions successful and others not. Plant invasion success or failure is based on a combination of evo...
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Alien invasive plants are a serious threat to natural and agricultural systems, especially in areas with sensitive habitats and high value crops. Dehong Prefecture, western Yunnan Province, China is vulnerable to invasive plants and its current status of invasive alien plants is assessed in this article. We compiled a comprehensive list of invasive...
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Background Xishuangbanna of Yunnan Province, southwest of China belongs to a global biodiversity and cultural hotspot. Agrobiodiversity plays an essential role in local livelihoods and traditional culture in the region. However, preliminary studies suggest that diversity of crop plants and livestock species is declining. We hypothesized that agrobi...
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Pigs (Sus scrofa) have played an important cultural role in Hawaii since Polynesians first introduced them in approximately AD 1200. Additional varieties of pigs were introduced following Captain Cook's arrival in Hawaii in 1778 and it has been suggested that the current pig population may descend primarily, or even exclusively, from European pigs....
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Part of the challenge in dealing with invasive plant species is that they seldom represent a uniform, static entity. Often, an accurate understanding of the history of plant introduction and knowledge of the real levels of genetic diversity present in species and populations of importance is lacking. Currently, the role of genetic diversity in prom...
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Mikania micrantha Kunth, commonly known as bitter vine, American rope, or mile-A-minute, is a rapidly growing vine, native to tropical America. Mikania micrantha is present in 20 Pacific island countries and territories, including Australia, the Cook Islands, Fiji, French Polynesia, Micronesia, Papua New Guinea, Samoa, Solomon Islands, and Vanuatu....
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Background As a means of biologically controlling Mikania micrantha H.B.K. in Yunnan, China, the influence of sweet potato [Ipomoea batatas (L.) Lam.] on its reproductive characteristics was studied. The trial utilized a de Wit replacement series incorporating six ratios of sweet potato and M. micrantha plants in 25 m2 plots over 2 years. Results...
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The competitive and allelopathic effects of wild rice (Oryza longistaminata) accessions on barnyard grass at different growth stages determined by days after sowing (0, 30, 60 and 90 days) were studied in greenhouse pot experiments. Wild rice accession RL159 exhibited the greatest height and tillering. The weed suppression rates of wild rice access...
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More than 100 years ago, Japanese knotweed was introduced to North America. Given its vigorous rhizome system and capability to grow from rhizome and stem fragments, it persists and spreads locally, forming monotypic stands. The Japanese knotweed clone originally introduced was a male sterile female clone; thus, early in the invasion, reproduction...
Article
Invasive species with distributions that encompass much of the North American environment often demand a range of management approaches, for several key reasons. Firstly, the North American environment includes a large number of highly variable habitats in terms of climatic, edaphic, and landscape features. Secondly, these regional habitat differen...
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Himalayan blackberry, an invasive weed in Canada, is particularly problematic in southwestern British Columbia. Isolated occurrences have also been recorded in Ontario. The nomenclature of this species has been under review recently; Rubus armeniacus Focke, R. discolor Weihe & Nees, and R. bifrons Vest have been frequently applied, as well as R. pr...
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Although Plantago major and Plantago asiatica have similar life-history characteristics, P. major populations expand much more rapidly than P. asiatica in habitats where both species occur. One potential factor contributing to this disparity is the production of phytotoxic compounds. However, the phytotoxic characteristics of P. major and P. asiati...
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Background There are a variety of ways of increasing crop diversity to increase agricultural sustainability and in turn having a positive influence on nearby natural ecosystems. Competitive crops may provide potent management tools against invasive plants. To elucidate the competitive mechanisms between a sweet potato crop (Ipomoea batatas) and an...
Article
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To explore the effects of invasive plant Mikania micrantha H.B.K invasion on plant community and diversity in farming systems, the composition, density, importance value, species richness, diversity indices and evenness index were analyzed under five different M. micrantha cover classes (0, 1-25, 26-50, 51-75 and 76-100%). The study took place in f...
Chapter
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Weeds cost hundreds of billions of dollars annually through crop losses, management costs, and many other types of deleterious economic impacts. Many of these impacts are rapidly increasing due to the spread of invasive plants into new regions. That such changes in weed distributions could be exacerbated by climate change is fairly obvious, and dis...
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Preventing the reinvasion and spread of invasive alien plants after chemical herbicide applications is a common challenge. A set of field experiments to examine the combined effect of competition with a local crop, sweet potato and the herbicide bentazon were conducted in Longchuan County of Yunnan Province, China. The results showed that the prefe...
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Climate change may lead to extensive shifts in invasive weed distributions by impacting their colonization and persistence in new habitats. Th ese alterations will require an enhanced capacity to predict the future range of these species and the implementation of effective management strategies. Th is is particularly critical for agroecosystems whe...
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This book is part of the "CABI Invasive Series", which addresses all topics relating to invasive species, including biosecurity surveillance, mapping and modelling, economics of invasive species and species interactions in plant invasions. Aimed at researchers, upper-level students and policy makers, titles in the series provide international cover...
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On land holdings of a few to thousands of acres, Christian colleges are preparing the next generation of leaders. We examined the importance of institutional land policies in conveying a sense of place and stewardship to students and campus communities. A survey of forty-three Council for Christian Colleges and Universities (CCCU) colleges found co...
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Covering just 2000 ha, Garry oak ecosystems (GOEs) in western Canada contain about 10% of the Species at Risk Act listed species at risk in Canada, including 30 plants listed by Committee on the Status of Endangered Wildlife in Canada as endangered. Since European settlement ca. 1840, GOE sites have been largely degraded by human disturbance, habit...
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Many weed species have already advanced northward from the United States into Canada, and their number threatens to increase with warming trends under climate change. For many weed species, this range expansion can be attributed to evolutionary adaptation by northern populations occurring in areas experiencing warmer climates and longer growing sea...
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Darbyshire, S. J., Francis, A., DiTommaso, A. and Clements, D. R. 2012. The Biology of Canadian weeds. 150 Erechtites hieraciifolius (L.) Raf. ex DC. Can. J. Plant Sci. 92: 729-746. Erechtites hieraciifolius, American burnweed, is a herbaceous annual in the Asteraceae native to forest zones of eastern North America, but introduced to parts of Europ...
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Rumex acetosella L., sheep sorrel, is a perennial herb originating from Europe and southwestern Asia, now found in at least 70 countries worldwide. A common weed, it appears in grasslands, pastures, rangelands, waste areas, and along roadsides across North America. It frequently occurs as a weed in lowbush blueberry fields in Atlantic Canada, parti...
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Invasion by non-native plant species is one of the greatest threats to prairie, savanna, and oak woodland habitats of the Willamette Valley-Puget Trough-Georgia Basin (WPG) ecoregion. Invasive plants can modify the diversity, structure, and function of natural habitats. Effects from non-native invasions have contributed to the decline of many nativ...
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Though regeneration of Garry oak (Quercus garryana) seedlings within Garry oak ecosystems is important to maintain this threatened habitat, seedling regeneration is often poor. Two independent studies were initiated in the early 2000s to examine questions surrounding Garry oak recruitment: one at the Crow's Nest Ecological Research Area (CNERA) on...
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Francis, A., Darbyshire, S. J., Clements, D. R. and DiTommaso, A. 2011. The Biology of Canadian Weeds. 146. Lapsana communis L. Can. J. Plant Sci. 91: 553-569. Nipplewort, Lapsana communis, is an annual weed of the Asteraceae native to Europe and western Asia, first detected in northeastern and Pacific northwestern regions of North America in the 1...
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Clements DR & Ditommaso A (2011). Climate change and weed adaptation: can evolution of invasive plants lead to greater range expansion than forecasted? Weed Research51, 227–240.SummaryInvasive plants are frequently viewed as harbingers of climate change owing to their potential to cause economic and ecological damage in the process of expanding the...
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Many herbaceous meadows are dominated by competitive non-native grasses and subject to ungulate herbivory, ecological processes that shift the proportional biomass of plant groups in the community. Predicting the outcome of restoration is complicated because herbivory and competition can interact. We examined the relationship between herbivory by n...
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1 Introducing a New Series: Biology and Impacts of Pacific Island Invasive Species Invasive species from across a broad taxonomic spectrum have affected the ecological integrity, human economies, and quality of life in the Pacific islands. In fact, to a large degree, problems caused by invasive species in the Pacific islands represent a stark warni...
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DiTommaso, A., Clements, D. R., Darbyshire, S. J. and Dauer, J. T. 2009. The Biology of Canadian Weeds. 143. Apocynumcannabinum L. Can. J. Plant Sci. 89: 977-992. Hemp dogbane, Apocynum cannabinum (Apocynaceae), is a perennial herb with white to greenish flowers in terminal clusters that produces pencil-like pods 12-20 cm long. A highly variable pl...
Article
A 9-yr (1990–1998) study was conducted at Woodstock, ON, Canada, to evaluate weed densities, crop yields, and gross returns in a modified no-tillage (no primary tillage) corn–soybean–winter wheat rotation under three weed management treatments: (1) minimum, preplant application of glyphosate followed by mechanical control; (2) integrated weed manag...
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European buckthorn, Rhamnus cathartica L., is an introduced shrub or small tree of forests, thickets, open pastures, hedgerows, roadsides, and riparian habitats. In Canada, it is found from Alberta east to the Maritimes, but is absent from Newfoundland. It is particularly abundant in southern Ontario. Problems arise from its status as an alternate...
Article
The demand for producers to farm in an environmentally sound, ethical, economically viable, and socially acceptable manner has driven cropping systems research beyond basic production agronomy. Cropping systems research today encompasses a broad range of topics ranging from agronomic to ecological, environmental, social, and economic dimensions of...
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Impatiens glandulifera Royle (Himalayan balsam) is an invasive alien annual up to 3 m in height with showy flowers that are generally pink or purplish. Native to the Himalayan region, I. glandulifera was first recorded in Canada in 1901 in Ottawa, and is now found in eight Canadian provinces: British Columbia, Manitoba, Ontario, Quebec, Nova Scotia...
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Invasive alien plants frequently possess greater seed banks than native species in disturbed areas, but native disturbance-adapted species may also possess large seed banks. We analyzed seed banks of ten sites with varying grazing histories in a shrub-steppe ecosystem dominated by antelope bitterbrush (Purshia tridentata) in the Okanagan valley in...
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The field of invasive species biology has been growing rapidly in the past decade, spurred on by the US Executive Order on invasive species in 1999. Despite calls to deal with invasive alien species under the International Convention on Biological Diversity in 1992, Canada has been slow to act. Part of the difficulty in managing alien invasive spec...
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In a 6-yr study on four farms (36 fields) in Ontario, Canada, we tested the effects of tillage (moldboard, chisel plow, no tillage) and crop rotations (continuous corn, corn-soybean, corn-soybean-winter wheat) on emerged and seedbank weed species diversity and density. Aside from the imposed experimental treatments, all other management was general...
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Full-text available
In a 6-yr study on four farms (36 fields) in Ontario, Canada, we tested the effects of tillage (moldboard, chisel plow, no tillage) and crop rotations (continuous corn, corn-soybean, corn-soybean-winter wheat) on emerged and seedbank weed species diversity and density. Aside from the imposed experimental treatments, all other management was general...
Article
Conservation tillage systems, such as no-tillage, are ecologically advantageous because they reduce soil erosion; however, they rely heavily on herbicide use. Our goal was to determine how weed communities of no-tillage systems are affected when the system is modified to reduce herbicide use through a combination of banded herbicides and interrow c...
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Invasive species have received considerable attention in recent years, but research has primarily focused on invasive species of natural habitats. Furthermore, cropland weeds have often been viewed as possessing a “general-purpose genotype” and therefore exhibiting relatively static genetics. However, a more current view is that weeds are capable o...