10
NON-NATIVE PLANTS if different approaches: Clifford W. Smith A weed is generally defined as a plant growing out of place. Using this definition, all plants introduced to Hawai'i by humans could he considered weeds. HoweGer. a~ricultural crom. such asuineaoole (Ananas co~nosus) and . ,, , btlgar c m e IS~~:~&I&U q,i~%ium~n), md h i~~~ic~~l~ur~l p1:tnti. w,.h :ih ' [~l~nieria (f'1101ioi~ O/~II~.UI) and row, tf<osu qq~.), \wuId r:mly lhe cun~iJ~~rcd \vccds. Other p1a111s hrottght III for ilgiiultural or Ii~rrti~~uI~u~itl purImse\ ;,re les\ resddy c;degorizd. Gusu (f'riliu~n spp.), for e\;tmplc, nia! he :t wmc- \shut \aIu3hlc iruit for juice and purer.>,hut i%e~ts:itin~ on rdnchlanJ5 ;ml n;~tural areas ;,re undeiirshlr.. 'llie recornition of rh? undc\irsbilit\ or s weed can therefore be a matter of persoial opinion. Land manage& have developed their own ideas of introduced problem plants. The Federal and State governments have gone one step further by developing a listpf~~ox~ous weeds which areserious threats to economic interests. Management and r~<eaxhaonnnoxious weeds receive high priority funding, and managers of natural areas have recently begun to develop ranked lists of significant weeds. At the outset, we should define several terms which are generally used to mean species not native to an area. The term &, while literally correct, is inappropriate because it also implies something excitingly different. m- a is appropriate, except that it implies a deliberate action--not always the case with weeds. Adventive generally refers to accidental introductions that persist for a while and then disappear-sadly, not the case with many plants we are discussing. The word alien has a connotation of not belonging; it is the term preferred by many who are concerned with management of natural areas. When Cd~tain James Cook arrived in the Hawaiian Islands in 1778. it i, emmt~,d th;;t thcrc iwrc ;iht~ut 0.10ntlli\e \peci~,> of pl:mt.; present (N'agner t.1 ul.. in prc,i). S:n.x then, o w r 4,OUu sliccics hwr been tntr~du,~:,l. According I<r icienti>ts a1 the 13ih1o Jluseum. a~~rox~matelv h70 of 1he.e vative because new invasions are beine discovered everv vear. Ninetv-one weeds now present significant manag~ment,prohlems in natural are& Hawai'i's lowlands are the principal points of entry for most of the intro- ductions to the Islands, so it is obvious that the lowland ecosystems (see Cuddihy, this volume) have suffered the most disruption from alien plants. Indeed, unless introduced plants survive in the tropical lowlands, they rarely 60

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Page 1: Untitled Page 002 [manoa.hawaii.edu]manoa.hawaii.edu/hpicesu/book/1988_chap/18.pdf · challenge to their survival. Most alien plants evolved in continental ecosys- tems where competition

NON-NATIVE PLANTS

if different approaches:

Clifford W. Smith

A weed is generally defined as a plant growing out of place. Using this definition, all plants introduced to Hawai'i by humans could he considered weeds. HoweGer. a~ricultural crom. such asuineaoole (Ananas co~nosus) and . , , , btlgar c m e IS~~:~&I&U q, i~%ium~n), m d h i ~ ~ ~ i c ~ ~ l ~ u r ~ l p1:tnti. w,.h :ih

'

[ ~ l ~ n i e r i a (f'1101ioi~ O/~II~.UI) and row, tf<osu qq~ . ) , \wuId r : m l y lhe c u n ~ i J ~ ~ r c d \vccds. Other p1a111s hrottght I I I for ilgiiultural or I i ~ r r t i ~ ~ u I ~ u ~ i t l purImse\ ;,re les\ resddy c;degorizd. G u s u (f'riliu~n spp.), for e\;tmplc, nia! he :t wmc- \shut \aIu3hlc iruit for juice and purer.>, hut i%e~ts:i t in~ on rdnchlanJ5 ;ml n;~tural areas ;,re undeiirshlr.. 'llie recornition of rh? undc\irsbilit\ or s weed can therefore be a matter of persoial opinion. Land manage& have developed their own ideas of introduced problem plants. The Federal and State governments have gone one step further by developing a l i s t p f ~ ~ o x ~ o u s weeds which areserious threats to economic interests. Management and

~ ~

r~<eaxhaonnnoxious weeds receive high priority funding, and managers of natural areas have recently begun to develop ranked lists of significant weeds.

At the outset, we should define several terms which are generally used to mean species not native to an area. The term &, while literally correct, is inappropriate because it also implies something excitingly different. m- a is appropriate, except that it implies a deliberate action--not always the case with weeds. Adventive generally refers to accidental introductions that persist for a while and then disappear-sadly, not the case with many plants we are discussing. The word alien has a connotation of not belonging; it is the term preferred by many who are concerned with management of natural areas.

When C d ~ t a i n James Cook arrived in the Hawaiian Islands in 1778. it i , e m m t ~ , d th;;t thcrc iwrc ;iht~ut 0.10 ntlli\e \peci~,> of pl:mt.; present (N'agner t.1 ul.. in prc,i). S:n.x then, o w r 4,OUu sliccics hwr been tntr~du,~:,l. According I<r icienti>ts a1 the 13ih1o Jluseum. a ~ ~ r o x ~ m a t e l v h70 of 1he.e

vative because new invasions are beine discovered everv vear. Ninetv-one weeds now present significant manag~ment,prohlems in natural are&

Hawai'i's lowlands are the principal points of entry for most of the intro- ductions to the Islands, so it is obvious that the lowland ecosystems (see Cuddihy, this volume) have suffered the most disruption from alien plants. Indeed, unless introduced plants survive in the tropical lowlands, they rarely

60

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become established at higher elevations, although plants originally cultivated ornamentals at lower elevations occasionallv escaue and become weeds in

h l r ~ A.D. U ~ v e r elevations now face increased oreisure from introduced

(in'the mountains). and Kohala (Hawai'i). Ornamental nlants such as ,.-~ ~ . .

nasturt~um ( T ~ o / i o t d r ~ ~ ~ i rrurjurj). Isntms r/.rr~rmtru n~~mbrr ) , glo~ybu\h ( ~ / ~ m ~ ~ / u r i ~ ~ u~i~i//v~rrru), :xnC vxriou, ~ingcr% (/f~~d!di;ru~t spp,) are ewnples of n1:111t\: ~ h ~ i h . whcn thcv csa11c front contr01lr.d i:~nd>c:m cultiv;~rion. can

?soil, rocks, cinders). It 1s not surprising that Hawai'i's native ecosystems face a very serious

challenge to their survival. Most alien plants evolved in continental ecosys- tems where competition has produced plants with highly successful survival strategies. Hawaiian plants are equally well adapted to survive in their own environment, but they did not evolve in the presence of disturbances caused by man, including two highly disruptive alien factors--feral animals and fire. Native s ~ e c i e s have not ex~erienced either the freaueocv or the intensitv of

- . of these Tactors.

IMPACT OF WEEDS ON HAWAIIAN ECOSYSTEMS

When weeds establish in an area they can have a number of different effects on the other olants erowine in thesame area. Phvsical disolacement ... . - ...- - - af other species, eit6er diF&tly o r - ind i rec t~~ is the m o m u e n t disruption, but weeds~can alsodeprive associated plants of water_sautrients, particularly nitroeen. bv absorbine their "fair share" of a EiniiTiV limited resource. ~ d d i h k i l i ~ , weeds G t as primary or alternaie hostsfor invertebrate pests and diseases.

Other effects of weeds are particularly disruptive in natural ecosystems These are more completely discussed elsewhere (Smith 1985) but will be mentioned here.

Formation of Monotypic Stands The formation of monotypic (single-species) stands of alien plants can

replace relatively diverse native ecosystems, In Hawai'i, the !ass of biological diversity in small areas can have a devastating effect on surv~val of endemic species with limited distributions and small population slzes. For example, strawberry guava or waiawi (Psidiurn cattleianum), an ahen thicket- forming tree, creates shade so deep that few natye plant seedlin s can sur- vive. It probably releases chemicals which mhtb~t pther species (%lelopathy) when fallen leaves decompose. Strawberry guava 1s spread by feral pigs (Sus scrofa) and introduced birds which eat its fmlt. For all of these reasons, the continuation or reestablishment of native plant communities where straw- berry guava occurs is unlikely.

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Changing Fire Characteristics Fires ignited by lava flows and lightning have always been a natural

occurrence in Hawai'i. But such fires were infreauent and small in area h;&se of natural firebrcakc and the infrequent hccurrence of lightning strike. at ground level. ('lcaring oi iclrests b\ humans md the introduction of fire-adioted erases. toeethef with fires caused bv human activities. haw chnnied th'is l~attern.';\lien grass stalks do noidisinlegrate rapidly after thcy die and thus provide excellent fuel for fires. Burning stimulates resorouthe of the erasies and. with increased fuel. allows natiGe venetation to be more-compleiely burned. Some native vegeiation simply doesnot re- cover at all after fire.

Changing Soil-Water Regimes The phennlogy (fruiting and flowering times) of many introduced species

is not svnchronized with Hawaiian climatic conditions: the result is sometimes that ecosystems dominated by alien plants are in a dormant stage during the wettest months in the Islands. Where this occurs, rain is retained in the soil instead of being removed by plants through evapotranspiration; increased surface runoff results, and erosion becomes a problem. Broomsedge (Andropogon vieinicus) is an example of a weed which has affected native ecosystems in this way.

Changing Nutrient Sta tus Volcanically active areas do not have mature soils; instead, they have

either lava or ash substrates characterized bv low levels of nitrates (see Street, this volume). Plantc which grow in sGch areas are adapted th s u ~ v r : under these cond~tlons. I luwever, n n n y alien plsnta are nitrogen-fiwrs, and, since fixed nitrogen is essential for growth, these s~ecies have faster growth rates than n a h e species, which. p a r t from enden~ic legumes such a5 koa (Acacia kon) and mamane (Sopltora cl~rysoplrylla), lack the nitrogen- fixinr ;ihil~ty. Nitropen-fivers will also enrich the soil as thcir l~trcr dec~mpos&, the ouicome being a medium in which other alien plants may grow. The original plants of the area are often replaced. Koa haole Leucaena leucoceplaala), kiawe or mes uite (Prosopispnllida), and fire tree

[Myricafaya) are examples of nitrogen-?iiing aliens.

Mutually Beneficial Interaction between Alien Plants a n d Animals

Alien anlrnalq such 3s feral ib \mall hdidn mongoo.;cs (H~rpmres aurop~rm.ratus), r.lls (Rarrrrs spp$, Ih lrirds (il l ; exampk. the Japanese white-eye. Zosrcn,lu japonirrr.<) act :I.; tl~stribut.~rs of al~cn plant seed.; in digestive tracts and on fur, feet, or feathers. Feral pigs are especial1 important agents in plant di.;triburion because thcy also dig up and irtilize considerable arels. which isvors establishment of alien wecies adanted to rich soils and luxuriant seedbed. ~ecause alien p1:uits are uied as food sources Ih!

the animals, alien animal populations may be maintained at higher densities and spread to new areas previously uninvaded. Alien plant seeds are then spread into morc and more new areas. Examples of this mutually beneficial situation are the rclationsh~ps of ferul oies and such olanh 3s strawherw guava banana, oka (Pas~~jlom rnollr~s;,&), and ha16 cath-ear ( ~ ~ ~ o t - l t & r i s P . radrcda). e ahen plants and animals benefit from the mutualism, natural areas deteriorate.

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THE PRINCIPAL WEEDS

The most aggressive weeds in Hawai'i today are not confined to any particular growth form. Some are herbs, others vines, shrubs, or trees. Weeds are not restricted to any particular habitat, being found in all disturbed ecosystems. Even in the alpine zone (see Cuddihy, this volume), some temperate grasses and other weeds occur, especially after disturbance.

From the standpoint of invasiveness and disruption of natural areas, the following are among the worst weeds in Hawai'i.

Banana poka (Passiflora mollissima) This weed is a vine that smothers even the largest trees. Almost cer.

in small areas, but natural enemies'(for example insects,.diseases) from it's native Colombian forests are being evaluated in Hawai'i, and one potential biological control agent, a moth, has been released (see Markin, this volume).

Blackberry (Rubus argutus) Blackberrv is a s~rawling. thornv shrub that forms imoenetrable thickets.

insects and diseases are known to affect blackberrv. hut others are being iought to control i t ciieai~el!. Chemical control (uw oi herh~cidesj i h "

alui heinp in\,c,n&ited i n a rcwsrch yriqc.r.r ar 1 l;wa:i \'olcsnoc\ Sntion;~l Park (Santos et a1 1986).

Broomsedge (Andropo on virginicus) # , and Fountain grass ( ennrsetum setaceum) Both species are highly invasive, fire-adapted, bunchgrasses. Broom-

sedge, now well established on Hawai'i and O'ahu, was probably inadvertently introduced in the early 1920s; fountain grass, principally a problem on the island of Hawai'i. was. and still is. available as an ornamental grass in seed

kent fountain e r a s from s o r e a d h to uuland areas. Natural enemies from the native habytats of these grasseiare known, but their introduction to the Islands might be o o ~ o s e d by the sugar tndustry because fountain grass is closely related to Ggar can& ~lso,~successfulbiological control f5r grasses has not yet been developed elsewhere.

Christmasberry (Schinus terebinthifolius) This rapidly growing, thicket-forming shrub shades out almost all other

plants. It was introduced as an ornamental around the turn of the century and has since become a favorite with bee-keepers: It 1s found on all of the Islands, being very effective1 distributed by blrds. Some natural pests have been introduced but are ine4ective.

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Fire t ree (Myrica fqa) This tree grows rap~dly, fixes nitrogen, and can form stands which shade

out most native plants. Introduced around the,tnrn of the century as a reforestation plant, it was soon realized that thls tree was a serious pest. Managers are worried about its impact because of the potential to change the nitrogen cycle of native Hawaiian ecosystems. It!s found on all of the rin cipal Hawaiian islands, but its greatest impact is in the forest around 41- '

cano on Hawai'i Island. Research on natural enemies from the Azores 1s under wa Research and management programs for herbicidal and manual control ohhe species are also in progress.

Kikuvu rnss (Penl~isefrmm ~lan~/es t@im and lblo k asses grass (Melmfi mmut~tlorn 1

These are hiFhlv invasive. mat-formhz erases that smother herbs and . ~~~

woody I)lants. ~%l&ses &ass is fire-adapiez. and kikuyu grass is well adapted to eraz:ng hv livestock. Both grasses were introduccd by the ranching industry easy in th i scen tu~~ and are <ell distributed on all Islands. p e r e is Tittle likelihood for biological control because of the commercial importance of these grasses, but chemical control (herbicides) of kikuyu vass in some natural areas is possible. Positive results include regeneration of natlve trees once the grass is removed.

Koa haole (Leucaena IeucoceDhala~ A thickei-forming, shrub that s t d e s out most o!her plant^.

this specles was deliberately introduccd for forage soon after 1864; 11 is used extensively for erosion conirol in dry areas. Th&Univer\ity of Hawaii is now developingstrains for biomass and firewood use in Third World countries.

This species is widely distributed throughout the Islands. .4 natural lnscc: enemy, Heteropyla nrlana, a sapsucker, was inadvertently introduced within the last 10vears and has had a devastatine effect. Most conserva- tionists mt~al l thought that the insect was 3 ho&; however, the loss of koa haole leaves a r lowed hroomsedqe to hecome s\tahli<hed mdcr the trecq, creatine a verv serious fire hazard. Although several insects feed on these sap-suclers. they do not con!rol them. ThFmltrginally economical drylnnd cattle indust? has persuaded 1-he State to introduce a pardsite of the sap- sucker; thee fectivene\r 01 t h ~ c Idlest introduction is not known.

Koster's curse (Clidemia h im) This shrub is hiehlv invasive. thicket-forminn. and smothers all other

plant^. Possibly in6od;ced as an erosion-contr(;ilinC! plant, ('lidenria hos awcll-known noxinus l~istorv in Fij~. I t is cstahlitheJ on : [ I 1 oi the principal Hawaiian Islands. ~robablv soreadinn bv seed on the boots and clothing of people workingbr hiking $the foyesk. One fungus disease has heen introduced to combat it, and a number of insects are heing evaluated. Unfor- tunately, the fungus disease does not spread readily and may have to be distributed in bottles by hikers or workers. Manual or chemical control may be possible in small areas.

Strawberry guava (Pridir~rn cnttl&nurnl . . ...... . . ..... . . ..~ .. This spdcies is a rapidly growing, thickc1~/orming tree which shades out all

other plants. hroduced in 1921 for its fruit. it \oon cscar~ed from culti.r,a- tion Strawberry guava has since spread throughout the islands (helped by its

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read distribution by alien animals) and is probably the most abundant woody w e e i No biological control research program bas been established, but chemical treatments are being tested m Hawaii Volcanoes and Haleakala National Parks.

Lantana (Lantana camara) -~ A t h o r h shrub which f o r k dense thickets, this plant was not a pect when

originally introduced as an ornamental in 1x58. 1Iowevcr. the common myna (Acridorl8erpsrrisris), intrnduced by William tiillebrand in 1865 to control army worms (the larval stage of a noctuid moth), spread the seed, and the plant flourished in thc dry lowlands. This was the rirst plant f<or which natural predators were introduced soon after [he turn of the century (I)wis eral., in press). Many different insects ha1.e bccn releascd since then in attempts to control this w e & some have hwn remarkahlv succesA~l. hut lantana remains a problem in certain dry areas.

RESEARCH AND MANAGEMENT NEEDS

The most important management emphasls to preserve the integr~ty of native Hawaiian ecosystems should be to stdp disturbance caused by alien inffuences. To this end, three immediate thrusts are needed: prevention of further introductions of invasive species, halting further disturbance of na- tive ecosystems by feral ungulates, and aggressive weed control programs.

Prevent Fu r the r Introduct ions The prevention of further importations of alien ~ p e c i e ~ :s imperat~ve ii i r e

are to manage our native habitats effectively. Resources arc needed to edu- cate people not to import biological material ind:scr~minhtcly, as well ;I\ 10 intercept deliberate attempts to smuggle material into the State. An immc- d~a te ~olitical steD would be to reauire that future eoverr~n~cnt-5oonsored landstaping use iative species or plants that are k&wn not to nat~ralize in Hawa~'~. A total prohibition on importations is not necessary. Ilowever, an outriehr ban on certain ~ l a n t nrouus (such as the melactome familv) and on spec& known to be prdblemsin dther tropical islands is imperati;;; species which are part of primary or seconda succession in tropical or sub- ?' tropical areas should be evaluated be ore they are permitted entry.

Public education about the effects of alienspecies is a Federal and State responsibility as well as the responsibility of educators, land managers, conservation-minded lay persons, and scientists. Two recent brochures, "Beware of the Noxious Weed" and "Are You a Carrier?", published by Foster Botanic Garden, Honolulu, are a valuable first ste toward educating the t general public on weed problems in Hawai'i. The est place to conduct the education of visitors is on incomine airulanes. where a 10-minute "commercial" explainin$ the prohlcm~and the im:or<ance oipreventing plant and animal introduct~m.; \wuld he much more effective than the prlnted form currently handed to passengers.

Provision should be made for peo le to discard harmful and forbidden material prior to leaving the airport. & nfiscation of material should be minimized except from people who are bringing,p!entially hazardous materi- al to the Islands. Quarantine of im orted matertal 1s Important to stop the introduction of associated pests angdiseases. A more vlsible and concerned

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presence by the State's agrjculture inspectors a t ports of disembarkation is also necessary. An inspechon of baggage slmllar to that on departure from Hawai'i would help keep people honest (see Smith, Controlling the Flow. . . , this volume);

Without the cooperation of the general public, however, there is little likelihood that any preventive program will work

Stop Disturbance of Kcosystems Vanv hiol0~15ts h:ne \ t r i w d thc relationshin between disturbance of . ,- -

ecosystems and shen plmt c d ~ l ~ < l ~ n ~ e r ~ t . I.cral ;ngulate mana ement pro- B grams must he dcvelope~l 1.1 the point that native forests are no onger slg- nificantlv disturhcd lw thew ;~riir l i : l l i . \Ye have to acceot the fact that feral ~~~~~~~ ~

ungulat& are here t r ~ s t q , and th:d thc! do provide reireation for a si n i l B - icant numhcr of rcsidenti. Ilon.c\er. i t is possible to keep them out o areas not now infested and to exclude them from imoortant naiural areas such as national parks, S t m Saturtd Are:, Reserves, Kature Conservancy prcscrvcs, areas of value for heir intsitneha or d~versiiy, and habitats of Endangered and Thlratened species. \lost ueeds gain a foothold in natural area, when thcground is exposed h! diwrhance. Feral pigs root u soil in their search

h S for earthworms and vthrr ic~orls, thereb creating a see bed for the \vccJ.; that they may thcrnselvcs introduce tot e area on hair or in tcce>., I'cral goats (Capm hircu~) and cattle (nos taums) eat foliage and othcnv~ie d z m ~ ! native plan&. In so doing thcv also create space for the estahl~hnent o i alicnspecies, some of which they may introduce. The Statc's pr;tcti.x I I ~

m~intainine fen1 animals for huntine in areas of h:oh evolutinn;~n :ml ecological hportancc should cease.-lt aggravates ihe alien p l . ~ n t ' ~ r d ~ l c ~ ~ i 11, encur~ngperpetual disturbance. (See G a p e and Gill; Stmc, \ ~ ~ r i - S m v c ~ Land Viitel%ates, this volume.)

Weed Control Programs Two Droerams are needed. The Erst is research on the biolom of the

most troihlesome weeds. The second is the development of an iniegrated pest management system.

Basic research questions concerning alien species remain unanswered. The most susceptible habitats should be identified and measures adopted to contain or prevent weed outbreaks in areas where management is possible. By evaluat~ng the biology of the alien, it is sometimes possible to identify critical noints in the life cvcle when it is suscentible to control. The most ~ ~~

important functtons of ieiearch are t t i uvalu:& the role olweeds in island r.cosvstems, determine their rm?nct o : ~ inative species and communities, and develop management strstegiri f.w thcir reduction and removal in key areas.

We realize today that technique3 for n~:mginp weeds in native ecosystems need much greater evaluat~on t l u n har treen given in thc paxt. not only for human safeiv but because management of alien species in natural are& in- volves a diffkrent goal than mnn;yr.ment for agrl&ltural reasons. Managers realize that an integrated pest nianJpnent appro.lch to ahen plant control is necessary. This involve5 use r r t hcrh~cldes. nimusl cmtrol, chanees in - cultural practices, and hiolng~chl control.

Chemical methods are essential ior many ip~xir's for which manual con- trol is imoractical and hiolocl:c;tl control doe$ not seem feasible or is far in the future. The use of h e r h h c s requircs considerable testlng prior to operational use in natural arex, bec~u>e native species, many of them rare

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and sensiti\.e, ;Ire 31 ri~k. The use of treatments invnlving localized applica- tion3 n i hcrhic~~lcr, e>pcciully in small areas. is labor intensive but can be quite effective for many species.

Manual removal of some species, including small trees, is also a necessary means of alien plant control. Many localized populations of weeds in Hawai'i's natural areas have been reduced in this way. Volunteerworkers can sometimes he used if the weed to be removed is distinctively different from nearby native species, and if,efforts are well managed. Use of mechanical control (such as bulldozers) is really not practical in natural areas because of damage to native species and exposure of large areas to further alien plant invasion.

Biological control (see Markin, this volume) is a promising long-term weed control strategy for some lants Biological control is controversial because some people do not beEeve that we should further pollute the hiologi- cal environment by introducing new aliens. The biological control agent may itself become a Dest if its actions are not confined to the tareet nlant. How- ~~-

ever, adequate icreening under quarantine cnnd~tions, buch-a. i l l ~ inbcct uuarantine facility at Hawaii Volcanoes National Park, c.m m~nirn~zc t h~s concern. Other ~ e o ~ l e worn, about what will redace the controlled weed. If

~ ~~

h is another wee'd, they q ~ ~ e s h o n the expcnditur~\ ~ 1 1 1 i u u t .ic111c\.ing ; I I I increase in native s ecies This concern ic vald, hut n 2 11;~c to .t;lrl wme- where. 1f bio1onicaycont;ol is conducted in cuniuncriori N I I ~ cor~trol of distur- bance, the chn&es of significant improvement are increased \Ve need to continue research on manual and chemic~l control for rnanv spec~cs and use all management options available. For most species, biologicil control will not be the total answer, and a number of control methods will he needed to alleviate alien plant problems.

RECOMMENDATIONS

There is no easv answer to controlline alien olants on islands. Each species has to be mnnoged on itr own an&gencrhly hy a number of different a proaches. I t is thc <uices~ful integration of these different ap roaches tRar is the challencc tn the rese:trch ,cientist and the manager. blutions are not found quicklvTn nimt c;~,cs, hut generally wme controris possible for most plants in at lea,t sums arc3,. Keeping the number of invasive weeds E n t in any n a t ~ ~ r d arca I J a minimum is a vc ry~mpor t i~~ t long-rermstrat- e w ofmanagement. As n1;n;tgernent devclop~ techniques to control the wide- spread species, the pool ~ i i \ \ eeds which can fill in the vacated area will he mtnimized. thus at\,ine nat~\c mecics 3 better chance to reestablish.

llawaiian nsiurai'arcas II:L& ,uffcrcd major disturbances in almost eve? ecological zone. The lecl>t imp;l:tcd areas. for.example some rain forest and alpine areas, should hc prmected i : r \~. llestorlng these environments is probably fcasihlc. Other arras. such 3s coastal lowlands, are usunllv so far degraded that it is dehatahlc that thcy can ever be restored to a scmhlance of their natural condition. These :m;is should not be abandoned outright. however, because thcy support several rare, native specles.

NI spccies naturalized in Hawai.i need to be evaluated for their potential to invade native ecosvstcms. Ecolocical studm on those species which arc or maybe severely hpacting naturzl areas are necessary. -Hikers and other

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people working or recreating in back-countly areas should be aware of prob- lem n l a n t ~ and record basic data about weed distribut~ons.

bf areas already altered.

Important References

Cuddihy, L.W. [this volume] Vegetation zones of the Hawaiian Islands. Davis. C.J.. E. Yoshioka. and D. Kaeeler. In Dress. Biocontrol of Lmrmto comma.

Howoi'i: Manazement mdReseorch. Univ. Hawaii Press for Univ Hawaii Cao~erative National Park Resources Studies Unit, Honolulu.

E Jer, F.E. 1942. Indigene versus alien in the development of arid Hawaiian vegetation, Ecology 23:14-23.

G a p < W.C., and L.T. Gill. [this volume] Conservation education in Hawai'i: history, problems, and needs.

Gerrish, G., and D. Mueller-Dombois. 1980. Behavior of native and nan-native plants in two tropical rain forests on Oahu, Hawaiian Islands. Phytocoa~tologia 8237.295.

Harper, J.L. 1965. Establishment, aggression, and cohabitation in weedy species. Pp. 243-265 IN H.G. Baker and G.L. Stebbins (eds.), 77te Generics of Coioniri,zg Species. Academic Press, New York.

Harris, D.R. 1962. Invasion of oceanic islands by alien plants. Tronsacrions, Insrirure of B"lish Geogmphy 31:67-82.

Haselwood, E.L., and G.G. Motter. 1983. Handbook ofHawoiian Weeds. 2nd edition, revised and expanded by R.T. Hiram. Univ Hawaii Press for Harold L. Lyon Arboretum, Honolulu.

Markin, G.P. [This volume] Alien plant management by biological control. Melville, R. 1979. Endangered island floras. Pp. 361-378 IN D. Bramwell (ed.), Plontr

and Islands. Academic Press, London. Mueller-Dombois. D. 1981. Understandine Hawaiian forest ecosvstems: the kev to bioloeical

~ u t c h i n s o ~ R o s s Publ. c;., ~tro;dsburg, Pennsylvania. Salisbury, E. 1964. Weeds andAlims. 2nd edition. Collins, London. Santos, G.L., D. Kageler, D.E. Gardner, and C.P. Stone. 1986. Herbicidal Controlof

Selected Alien Piant Species in Hawaii Volcanoes National Pa*. Univ. Hawaii Cooperative National Park Resources Studies Unit Technical Report M). Botaoy Dept., Univ. Hawaii, Honolulu.

Smith, C.W. 1985. Impact of alien plants on Hawai'i's native biota. Pp. 1M-250 IN C.P. Stone and J.M. Scott (eds.), Hawai'i's T m s t i a l Ecosystemc Plereworiort and Management. Univ. Hawaii Press for Univ. Hawaii Cooperative National Park Resources Studies Unit, Honolulu.

Smith, C.W. [This volume] Controlling the flow of nan-native species.

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stone, C.P. [This volurnc] Nan-native land vertebrates. stone, C.P., C.W. Smith, and J.T. Tunison (eds.). In press. Alien Plant Invasions i t

Native Ecosystems ofHowai'i: Management and Rescorch. Univ. Hawaii Press for Univ. Hawaii Cooperative National Park Resources Studies Unit, Honolulu.

Street, J.R. [this volume] Soils in Hawai'i. Wagner, W.L., D.R. Herbst, and S.H. Sohmrr. In press. Maneol of lhe Flowering Plants of

Hawoi'i. Bishop Museum and Univ. Hawaii Presses, Honolulu.