Anuradha Prakashan, New Delhi

Ecosystem

and

Invasive PlantsA Continuous Dynamics

Dr. Parveen Garg

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Author

Dr. Parveen Garg

ISBN No.: 978-93-82339-76-2

First Impression, May, 2014

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Ecosystem and Invasive PlantsA Continuous Dynamics

INDEX

CHAPTER I 5

CHAPTER II 13

CHAPTER III 33

CHAPTER IV 77

CONCLUSIONS 104

LITERATURE CITED 111

INTRODUCTION

SPREAD OF INVASIVE SPECIES

IMPACT OF INVASIVEALIEN PLANT ON

ECOSYSTEMAND SOCI-ECONOMICS FACTORS

CONTROL OF INVASIVE PLANTS

CHAPTER 1INTRODUCTION

An "invasive species" is defined as a species that isnonnative (or alien) to the ecosystem underconsideration and whose introduction causes or is likelyto cause economic or environmental, such as bacteriaand virus.Aplant is regarded as if it :

In simple terms, an invader has to:

The plant must find a vector that will bring it to a newenvironment. This new habitat must be a close enoughmatch to its native range that it is able to survive andreproduce here without human cultivation. To actuallybecome invasive, the introduced plant has to be able toout-compete native species, to reproduce effectivelyenough to start spreading geographically through itsnew habitat and to negatively impact the ecosystems inits introduced range.

Invasive plants are usually those that were introduced,either intentionally or unintentionally, into a localitywhere they previously did not grow. Introduced plants,

invasive

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Has been introduced by human action to alocation where it did not previously occurnaturally,

Becomes capable of establishing a breedingpopulation in the new location withoutfurther intervention by humans, and

Spreads widely throughout the new location.

Arrive,

Survive, and

Thrive,

Ecosystem and Invasive Plants......5

also called exotics or alien species, form an importantpart of our environment, contributing immensely toagriculture, horticulture, landscaping, and soilstabilization. But among the thousands of plant speciesintroduced to different parts of the world, approximately10 percent display the aggressive growth tendencies ofinvasive species. Although the terms and

are sometimes used interchangeably, not allexotic plants are invasive. In addition, some nativespecies i.e. those plants that grew in an area prior ofsettlement, can be invasive, especially as naturallandscapes are altered.

An invasive plant has the ability to thrive and spreadaggressively outside its natural range therefore anaturally aggressive plant may be especially invasivewhen it is introduced to a new habitat. An invasivespecies that colonizes a new area may gain anecological edge since the insects, diseases, andforaging animals that naturally keep its growth in checkin its native range are not present in its new habitat.

Some invasive plants are worse than others. Manyinvasive plants continue to be admired by gardenerswho may not be aware of their weedy nature. Others arerecognized as weeds but property owners fail to do theirpart in preventing their spread. Some do not evenbecome invasive until they are neglected for a long time.Invasive plants are not all equally invasive. Some onlycolonize small areas and do not do so aggressively.Others may spread and come to dominate large areasin just a few years.

Historically, there have always been migrating planttaxa, some expanding into areas distant from regions oftheir origin, others reclaiming areas which they hadbeen temporarily excluded due to adverseenvironmental conditions. Now, however, the rate of

exotic, alien,invasive

Ecosystem and Invasive Plants......6

human-assisted migrations (i.e. Pyseket al., 2005) of plants is several orders of magnitudehigher. In California, for example, more than 1000 alienplant species introduced either intentionally oraccidentally, have established viable populations overthe last 250 years. In the Galapagos Islands, throughouttheir three million year history, only one new plantspecies arrived with birds or sea currents approximatelyevery 10,000 years (Porter, 1983). Over the last 20years, however, the human-assisted introduction ratehas been about 10 species per year or some 100,000times the natural arrival rate (Tye, 2001). In Indiaintentionally planted and accidentallyarrived Sp. is causing havoc to theecosystem as well as to the human health. At least inlight of these numbers, current plant invasions aredifferent from natural migrations.

Invasive species are not a separate biological category,it includes all types of plants, including vines, trees,shrubs, ferns and herbs, can become invasive. They do,however, share certain characteristics that help themrapidly grow and invade new areas. Invasive plantstypically exhibit at least some of the following :

invasions sunsu

Lantana sp.Parthenium

Characteristics of Invasive Species

Production of many seeds

Highly successful seed dispersal

No special seed germination requirements

Grow in disturbed ground

High photosynthetic rates

Thrive in high-nutrient conditions

Rapid growth and maturity

Early maturation

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Ecosystem and Invasive Plants......7

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Reproduction by both seeds and vegetativemeans

Long flowering and fruiting periods

Most exotic plants do not pose an obvious threat tonative plants when they are first introduced, but we donot fully understand the dynamics of what makes plantsinvasive. The same plant species can be invasive in onehabitat or area and not aggressive in another.Sometimes many ears separate the first introduction ofa plant and its later spread as an invasive species. Forexample, Atlantic cord grass ( ) waspresent in small areas on the Pacific coast for more thanfifty years before it became invasive.

Often by the time a plant is recognized as being a majorproblem it has become so well established thateradication is difficult or impossible. Even when plantsare recognized as a potential problem, finding themoney and manpower needed to eliminate them maynot be easy. For example, leafy spurge (

), which forms dense stands that cattle refuse tograze, was seen as a potential problem in Ward County,North Dakota, in the 1950s. By the time funding wasavailable to deal with the problem on both public andprivate lands; leafy spurge was present in all townshipsin the country and had increased from one small patchto about 12,000 acres.

Alien species are non-native or exotic organisms thatoccur outside their natural adapted ranges anddispersal potential. Many alien species support ourfarming and forestry systems in a big way. However,some of the alien species become invasive when theyare introduced deliberately or unintentionally outsidetheir natural habits into new areas where they expressthe capability to establish, invade and out competenative species.

Spartina alterniflora

Euphorbiaesula

Ecosystem and Invasive Plants......8

International Union for conversion of Nature andNatural Resources (IUCN) defines Alien InvasiveSpecies as an alien species which becomesestablished in natural or semi natural ecosystem orhabitat, an agent of change, and threatens nativebiological diversity. These invasives are widelydistributed in all kinds of ecosystems throughout theworld, and include all categories of living organisms.Neverthless, plants, mammals and insects comprisethe most common types of invasive alien species interrestrial environments. The threat to biodiversity dueto invasive alien species is considered second only tothat of habitat destruction. Invasive species cause lossof biodiversity including species extinctions, andchanges in hydrology and ecosystem function.Differences between native and exotic plant species intheir requirements and modes of resource acquisitionand consumption may cause a change in soil structure,its profile, decomposition, nutrient content of soil,moisture availability, etc. Invasive species are thus aserious hindrance to conservation and sustainable useof biodiversity, with significant undesirable impacts onthe goods and services provided by ecosystems.Biological invasions now operate on a global scale andwill undergo rapid increase in this century due tointeraction with other changes such as increasingglobalization of markets, rise in global trade, travel andtourism. For effective management of invasive species,knowledge about their ecology, morphology,phenology, reproductive biology, physiology andphotochemistry is essential.

The present Review work focuses on themes relatedwith the ecology of alien invasive species such as

Biology of invasive species,

Reasons behind invasiveness

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Ecosystem and Invasive Plants......9

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Predication of invasive potential of non-nativespecies.

Susceptibility of ecosystems to invasions,

Impact of invasions on native plant species andbiodiversity,

Possibility of enhancing the capacity of ecosystemsto resist or recover from alien

Species invasion,

Possible control measures, and

Development of a reporting system for alien invasivespecies.

Present work also attempted to review the ecology ofinvasion which requires information on the

Rate and mechanism of transport and movement oforganism,

On characteristics allowing a species to becomesuccessful invader and

Also on the properties of the ecosystems that makethem susceptible to the invaders

Probable traits favouring invasivness in terrestrialplants include high tolerance against environmentalextremes and greater adaptability in wide range ofenvironmental conditions; high water, light and nutrientuse efficiencies; zero or very short dormancy period,high productivity; and high reproductive potential.

Emerging mechanisms of plant invasion such asenemy release hypothesis and novel weaponhypothesis (allelopathy) is also a part of this work.However a single theory does not account for thesuccess of invaders in naturalized areas. About 40% ofthe species in the Indian flora are alien, of which 25%

Ecosystem and Invasive Plants......10

are invasive India is very rich in adventives weedswhich included Asteraceae weeds such as

In the 19th century, Alphonse De Candolle, CharlesDarwin, and Joseph Hooker already paid a substantialattention to plant invasions. However, only after thepublication of Charles Elton's (1958) classic

didinvasion ecology emerge as a new discipline, firstslowly (Salisbury, 1961; Baker and Stebbins; 1965) andlater explosively (e.g., Drake et al. 1989; Williamson,1996; Sandlund et al., 1999; Child et al., 2003). Thescope of contemporary invasion biology is broad,ranging from essentially theoretical studies (Shigesadaand Kawasaki, 1997), through studies dealing withparticular regions (Kowarik, 2003; Tellman, 2002), topractical recommendations of how to deal withparticular invasive pest species (Sheley and Petroff1999; Bossard et al., 2000). Nevertheless, what hadbeen missing is a real summary, a synthesizing volumeputting plant invasion biology into a broader context ofcontemporary ecology.

There are still serious gaps in our understanding ofinvasive plants. Many of them were identified in thisreview. Operational criteria for impact assessment ofalien plants is one of them. Invasive species are oftenblamed for extinction of rare species. Invasivepredators and pathogens provide several conclusiveexamples. As for plants, however, we still have to reacha more balanced view of what is really going on (Brookset al. 2004; Davis, 2003; Farnsworth, 2004; Houlahanand Findlay, 2004; Rejmanek et al., 2004). Even on

Partheniumhysterophorus, Eupatorium adenophorum, Eupatoriummoderato, Mikania micrantha, Ageratum conyzodies,Galinsoga parviflora, etc.

TheEcology of Invasions by Animals and Plants

History of Study of Invasive Species

Ecosystem and Invasive Plants......11

islands, where numbers of exotic plant species areoften increasing exponentially, extinctions of nativeplant species cannot be attributed to plant invasions perse (Sax et al., 2002). Plant invasions are very often justsymptoms of human-created changes in ourenvironment rather than causes of those changes. Asscientists, we should do our best to explain what we doknow and what we do not know.

Ecosystem and Invasive Plants......12

CHAPTER 2SPREAD OF INVASIVE SPECIES

The scientific study of invasions dates to 1958, with thepublication of

by the English ecologist Charles Elton. "We mustmake no mistake" he wrote. "We are seeing one of the greathistorical convulsions in the world's fauna and flora." Eltonand his followers sought to discern underlying patterns ofinvasion, to forge theories about the hidden structures ofecosystems, and so explain the apparent patterns ofinvasions.Are some organisms 'better invaders than others?Why do American gray squirrels seem to be everywhere?Why do certain environments, notably islands like Hawaii,seen especially vulnerable to invasion? Every invasion was apotential case study in why ecosystems do — and don't —remain intact.

People have been the major factor in the spread of invasivespecies. Humans have always carried plants with them forfood, medicine, fiber, ornament, or just curiosity. As humanpopulation has increased, so has the demand for food,housing, transportation and other necessities of life moreand more land is disturbed to provide people with what theyneed and want, and disturbed land is where invasive speciesget their footholds. Increased international travel and globalworld trade also contribute to the problem. Invasive specieshave arrived in their non native land in the cargo holds ofairplanes, as seeds in grain shipments, in the soil ofornamental plants, and as ship ballast. Improvements intransportation technology allow both people and plants totravel thousands of miles in just a few hours.

New environment provide an ideal place for invasive plants.These species leave behind the natural controls (usuallyinsects, bacterial, viral and fungal diseases) that kept themunder control in their native habitats and can often spreadunchecked. Some, such as the common dandelion

The Ecology of Invasions by Animals andPlants

Ecosystem and Invasive Plants......13

( ox-eye daisy (or tree-of-heaven ( )

congress grass ( ), have become integratedover time into the flora of urban areas and are the dominantand familiar vegetation (Titman 2004).

Most of the invasive species in Non native land are originallyfrom those areas, with very similar climate. Many of thesespecies were first introduced as ornamental plants. Anexcellent example is honeysuckle ( ), whichwas introduced in the late 1890s In North America ashorticultural shrubs and vines and for wildlife habitatimprovement. Honeysuckle often out-competes nativeplants due to earlier leaf expansion and later fall leafretention. Large thickets of honeysuckle interfere with the lifecycles of many native shrubs and herbs. These stands alterhabitats by decreasing light and depleting soil moisture andnutrients. Some honeysuckle species also releasechemicals into the soil that inhibit the growth of other plants.Fruits are consumed and passed by birds, which makeseffective control difficult.

Another ornamental that turned invasive is kudzu (), a wine with attractive purple flowers that was first

exhibited in the United States at the Philadelphia CentennialExposition in 1876. It is now listed as a noxious weed in manystates, especially in the South, where it smothers large treesas it clambers for light.

Accidental introduction is also a common way for invasivespecies to become established. Mile-a-minute weed( ), an Asian vine named for its fastgrowth rate, appeared in rhododendron nurseries inPennsylvania in 1946, presumably the result of seeds mixedwith imported plants. Since then it has spread to other areasin Pennsylvania as well as to surrounding states and israpidly becoming a major problem along roadsides and otherdisturbed areas.

Invasive plants are also a major threat to native plants andanimals, including rare and endangered species. In fact,alien species are considered by some experts to be second

Taraxacum officinale), Chrysanthemumleucanthemum) Ailanthus altissima

Parthenium sp

Lonicera spp.

Puerarialobata

Polygonum perfoliatum

Ecosystem and Invasive Plants......14

Ecosystem And Invasive Plants AContinous Dynamics

Publisher : Anuradha Prakashan ISBN : 9789382339762 Author : Dr. Parveen Garg

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