Distribution and Potential Spread of Japanese Knotweed (Polygonum cuspidatum) in Canada Relative to Climatic Thresholds

Abstract

Japanese knotweed (JK) is one of the most aggressive invasive plants known in the U.K., where its biology has been well-studied. It was introduced into Canada around 1900, but only recently has it become a serious concern in the province of British Columbia (BC). Climatic conditions, including annual degree days and mean-annual minimum temperatures at knotweed sites in British Columbia were modeled in BioSIM, using weather normals and long-term daily weather data, and compared to published thresholds (degree day = 2,505 DD, minimum temperature = −30.2 C, base temperature 0 C). The degree-day threshold was more limiting to JK in British Columbia than mean-minimum temperature (12.3% of province habitat was suitable for JK based on degree days compared with 26% for mean-minimum temperature). A new annual-precipitation threshold of 735 mm/year based on 95% of known knotweed sites in BC was identified. The best-fit logistic regression model included degree days and annual precipitation and predicted knotweed presence/absence with over 97% efficiency. Existing knotweed sites occupy just over half of the suitable habitat in BC, indicating there are still significant areas to be invaded. The limiting threshold for knotweed was reversed in Southern Ontario with between 35 to 53% of the habitat suitable based on minimum temperatures, whereas degree-day accumulations and annual precipitation were not limiting. Warmer temperatures from 2000 to 2008 resulted in an increase to 53% of the habitat in Southern Ontario being suitable for knotweed, compared to 35% when 1971 to 2000 weather normals were used. Different climatic thresholds among provinces might result in selection for different invasive knotweed genotypes. This could influence the success of biological control agents because of differential host suitability of knotweed genotypes. Habitat suitability maps generated will enable better targeting of knotweed surveys based on the risk of knotweed establishment.

Mapping of alien species of Asclepias syriaca and Fallopia japonica populations in the agricultural landscape

“…japonica is one of the most aggressive invasive species in Czech Republic (Mandák, Pyšek, Bímová, 2004), Belgium (Tiébré, Saad, Mahy, 2008), Great Britain and represents a serious problem also in Canada (Bourchier, Van Hezewijk, 2010;Gaskin, et al, 2014) and western USA (Gaskin, et al, 2014).…”

Ecology and Management of Weeds in a Changing Climate

“…The developed world has historically been centered in Europe and North America, and, by extension, these regions have featured the most intensive weed management efforts, including the monitoring of potential expansion of weed distributions [5,21,[24][25][26][27]. Parts of Oceana, particularly Australia and New Zealand, have also received considerable attention in this regard [28,29].…”

“…As shown in Table 2.1 [21,[35][36][37][38][39][40][41][42][43][44][45], relatively recent northward expansion of weed ranges has been well documented for numerous weed species in North America, and doubtless, there are many more examples of this phenomenon [46]. This northward weed migration is of particular concern in areas where traditionally many weeds have been unable to establish because of severe winter conditions, such as in the northeastern USA [47] or Canada [48].…”

“…As indicated in Table 2.1, Fallopia japonica has recently shown rapid range expansion in both Ontario and British Columbia, Canada [21]. Fallopia japonica is one of the most aggressive invasive plants in Europe, having invaded large areas of the UK and other countries after its introduction from Asia [53].…”

“…Bourchier Warwick et al [45] by Fallopia japonica, there is much more potential for future expansion. Costs of Fallopia japonica control in both Europe and North America are considerable (e.g., between £ 1 and 8 m −2 in the UK), and thus climate change scenarios threaten to increase these costs [21]. There are also indications that Fallopia japonica could develop increased frost tolerance [54] and genetic diversity through hybridization with Fallopia sachalinense (F. Schmidt) Ronse Decraene (giant knotweed), as has been documented in Washington State [55] and British Columbia [56].…”