Download Pueraria montana (Kudzu) Impacts Information

Pueraria montana var. lobata (Kudzu Vine)
Impacts Information
Contents
1.0 Introduction………………………………………………………………….... Page 1
2.0 Ecosystem Change……………………………………………………………..Page 1
3.0 Reduction in Native Biodiversity…………………………………………….. Page 1
4.0 Competition…………………………………………………………………… Page 2
5.0 Disease Transmission…………………………………………………………. Page 2
6.0 Modification of Nutrient Regime ……………………………………………. Page 2
7.0 Economic/Livelihoods………………………………………………………… Page 2
8.0 References……………………………………………………………………... Page 3
1.0 Introduction
Kudzu is widely believed to drastically reduce biodiversity because of its ability to
smother other vegetation and develop large-scale monocultures, although quantitative
investigations are lacking (Alderman 1998, Forseth and Innis 2004, in Sun et al. 2006).
Kudzu is an aggressive vine that currently dominates an estimated 810 000 hectares of
mesic forest communities in the eastern United States (Harrington Rader-Dixon & Taylor
2003). It can climb overtop and subsequently kill new seedlings or mature trees
(Berisford Bush & Taylor 2006). Forestry problems associated with aggressive vines
such as kudzu include mortality of edge trees, exclusion of native plant species, and
potential to increase fire hazard during winter (Putz 1991, in Harrington Rader-Dixon &
Taylor 2003). It can cover ponds, shallow lakes, and river margins, displace native
vegetation and cause great concerns for survival of native species (Kiviat 1993, in Ding
et al. 2006). Kudzu dominates other plants by climbing over and shading everything in its
path, killing native herbaceous and woody species. Because of this, the USA Congress
listed kudzu as a federal noxious weed in July 1997, Harrington Rader-Dixon & Taylor
2003).
2.0 Ecosystem Change
Few plants can survive once smothered by kudzu and small ecosystems could be
radically altered. The plant quickly develops, rapidly covering the soil, affecting
indigenous plants and completely modifying the structure of the ecosystem (Clabassi et
al. 2003, in EPPO 2007). Kudzu may have a disproportionate effect on animals with
specific mutualisms or feeding relationships with trees or shrubs suppressed by its growth
(Forseth & Innis 2004).
3.0 Reduction in Native Biodiversity
Kudzu is invading National Parks in the USA and when it does encroach on natural areas
it kills trees and plants by growing over them (EPPO 2007). Pron (2006, in EPPO 2007)
found that there was a reduction in the number of species in invaded places: while 20 to
25 species grew in 4 m² of non-invaded meadow or forest, only 6 to 9 species grew in 4
m² invaded by kudzu. Moreover, light indicators were lower under the cover of kudzu,
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while temperature indicator values were higher. A reduction in the number and diversity
of arthropods has also been identified in invaded sites (EPPO 2007). Near Magliaso
(Switzerland) a total of 262 arthropods (17 taxa) were found in uninvaded forests, while
only 187 arthropods (12 taxa) were found in invaded sites (EPPO 2007). The number of
mites, beetles, ants and springtails decreased in invaded sites, while the number of
Glomerida and Myriapoda feeding on litter augmented (EPPO 2007).
The lack of quantitative data on the effects of Pueraria Montana on community
biodiversity is especially critical because of the high native biodiversity of the
southeastern United States (Blaustein 2001, in Forseth & Innis 2004). The high level of
endemism and regional diversity could be permanently endangered by the spread of P.
montana.
4.0 Competition
Key traits of kudzu that contribute to its ability to spread rapidly and dominate natural
communities are its high allocation to extension growth and leaf area instead of support
structures; frequent rooting of stems at nodes in contact with the soil, rapid leaf
movements, high leaf level photosynthetic rates accompanied by high leaf area indices,
large hydraulic capacitance in roots and rhizomes, and the ability to fix atmospheric N2
(Forseth & Innis 2004). This unique combination of traits makes P. montana an
extremely aggressive competitor in the eastern deciduous and southeastern USA mixed
pine forest biomes, as well as making it a challenging plant to eradicate once established
(Forseth & Innis 2004).
5.0 Disease Transmission
Soybean rust (Phakopsora pachyrhizi) is common on kudzu in areas close to soybean
fields in Brazil and Paraguay (Poolpol & Pupipat 1985, Morel 2003, in EPPO 2007). A
Phytophthora species was also isolated from infected root and foliar parts of kudzu in the
Republic of Korea (YW Lee Pers. Comm. 2003, in EPPO 2007). The pest could therefore
be a reservoir for soybean rust and Phytophthora species (EPPO 2007).
6.0 Modification of Nutrient Regime
Pueraria montana forms a dense root mat and annually produces a thick leaf litter layer
with high leaf nitrogen due to its nitrogen-fixing properties (Forseth & Innis, 2004).
Kudzu has a symbiotic relationship with nitrogen-fixing bacteria (Rhizobium spp.) in
root nodules and can almost double the concentration of nitrogen compounds in the
topsoil (1 to 6 cm deep) (Pron 2006, in EPPO 2007). Due to the nitrogen-fixing
properties of kudzu there is considerable potential for large stands of P. Montana to alter
the nitrogen cycles of small streams and watersheds in the southeastern USA (Forseth &
Innis 2004). Due to its intentional planting on steep hillsides and slopes, the probability
of leaching of nitrates into nearby streams is enhanced; this has implications not only for
terrestrial nutrient cycles and biodiversity but also for aquatic biodiversity and
eutrophication (Forseth & Innis 2004).
7.0 Economic/Livelihoods
As a rapidly growing vine, kudzu can cover and smother orchard and plantation crops,
including young forest plantations. Where productive forest land has been overtaken, lost
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productivity is estimated at about 120 USD per hectare per year (EPPO 2007). The
monetary losses from kudzu result mainly from reduced land productivity, primarily in
forested areas. There are a variety of estimates for the economic impact of P. montana,
covering lost income from forestry, control costs for utilities and agriculture, and control
efforts in national and state parks. Lost productivity in forests has been estimated at
anywhere between $100 to 500 million per year (Blaustein 2001, Quimby et al. 2003, in
Forseth & Innis 2004).
Kudzu periodically interrupts power throughout the southern U.S., especially in rural
areas where it can topple power lines with its weight (Blaustein 2001, in Forseth & Innis
2004). Railroad companies have to devote resources to controlling kudzu growth over
rails, which can result in wheel slippage and derailments. National and state parks devote
considerable resources to control of alien species, including kudzu, which causes losses
in biodiversity and reduced aesthetic values in recreational areas (Boyette Walker &
Abbas 2002). Blaustein (2001) reports that P. Montana infestations at parks such as
Vicksburg National Military Park can decrease the park’s historical and tourist value; on
the high bluffs of Vicksburg National Military Park, natural grasses have been covered by
P. Montana, altering the historical landscape.
8.0 References
For references please see the GISD Species Profile for Pueraria montana var.
lobata(References Section).
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