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Piper aduncum - the great plant invader

see also my website: www.piperaduncum.net

 

When I arrived in Papua New Guinea in 1995, I noticed that the fallow vegetation in many shifting cultivation systems was dominated by a single species. Foresters told me it was Piper aduncum, an introduced species. At that time no systematic research was done on the cause for its spreading nor on its effects on soils and crops. That were reasons for a series of investigations and experiments. Below is a brief report on this highly important plant invader including current research activities and some future plans.

 

Bioinvasion

Introducing plant species into new environments can have many unanticipated ecological effects. Whether deliberately introduced as ornamentals and economic plants or brought in accidentally, new species can have devastating effects on ecosystem quality and functioning through out-competing indigenous species and habitat modification. As a result, an endemic flora may become extinct. An example which has recently gained attention in Africa and Asia is the small shrub Chromolaena odorata, a native of Central and South America which was brought to Asia in the late 19th century. It then spread rapidly across Asia and arrived in Africa in the 1940s. Its spread is closely related to human activities, in particular frequent disturbances of the natural vegetation from agriculture and road maintenance. An example from the Pacific is Miconia calvescens which was introduced as an ornamental but is now one of the major pests in the Society Islands of the Pacific where it is nicknamed the “green cancer”.  

In many areas of Papua New Guinea the shrub Piper aduncum has invaded. The invasion of Piper aduncum in the humid lowlands appears similar to the spreading of Chromolaena odorata in Asia and parts of West Africa, and to the invasion of Miconia calvescens.

 

Origin of Piper aduncum

Piper aduncum is a member of the family Piperaceae of which there are some economically important species in the Pacific, including Piper nigrum (pepper), Piper methysticum (kava), and Piper bettle of which the fruits are used with betel nut (Areca cathecu) in Papua New Guinea. Piper aduncum is a shrub or small tree with alternate leaves and spiky flowers and fruits. It occasionally reaches an height of 7 to 8 m, and has very small seeds, which are mostly dispersed by the wind, fruit bats and birds. Piper aduncum is common throughout Central America where it is found between sea level and 2,000 m a.s.l. along roadsides and in forest clearance areas on well-drained soils. It occurs in Mexico, Central America, Surinam, Cuba, Southern Florida, Trinidad and Tobago, and Jamaica and is very common in Costa Rica on open or partly shaded sites. In the Neotropics, Piper aduncum may be locally abundant but the species rarely dominates the vegetation or is found in mature vegetation. In the Amazon areas, it has been reported as an invading plant after timber exploitation. Extracts of Piper aduncum are used as folk medicine in South America. The species is mentioned in several ethnopharmalogical databases, and has antifungal and antibacterial compounds.   

Genteng Highlands piper & Arif.jpg (127817 bytes)  Genteng Highlands piper & ferns 3.jpg (168123 bytes)  Genteng Highlands piper disturbed sites 2.jpg (123999 bytes)  Piper aduncum.jpg (51569 bytes)

Thumbnails: In Malaysia Piper aduncum is common in secondary 

fallow vegetation in the Genteng Highlands

 

 

Spreading of Piper aduncum

Piper aduncum was introduced in the Botanical gardens of Bogor (Indonesia) in the 1860. By the 1920s, it commonly occurred in a radius of 50 to 100 km around the Botanical Gardens in young secondary vegetation, close to rivers and on very steep slopes, locally in dense stands. Piper aduncum was noted in Jayapura in 1955 and in Biak in 1960 on Papua (Irian Jaya) and in Malaysia (see thumbnails above) and Borneo in the 1960s. It has also been recorded in Singapore and Sumatra, and is on the list of unwanted weed species by the quarantine service of Australia. Piper aduncum was introduced into Fiji in the 1920s and is now widespread in the wet and intermediate zones of Viti Levu. It is also found on Hawaii, Vanuatu, Christmas Island and the Solomons Islands. It is not known when and how Piper aduncum arrived in Papua New Guinea but it is likely that the seeds came in by accidental transport from Papua or perhaps from Fiji. The botanist Mary Clemens first observed Piper aduncum in 1935 near the mission station Heldsbach in the Morobe Province.

       

It was not very widespread in the early 1970s and Piper aduncum is not separately listed in the standard text on New Guinea vegetation by Paijmans. By the late 1990s Piper aduncum is very common in the lowlands of the Morobe and Madang Provinces, and is also observed in the Central Highlands above 2,000 m a.s.l. Seeds are being spread by flying foxes and logging equipment. Causes for its rapid spreading remain unclear but evidence is being accumulated that areas of high native plant species richness and cover, like many areas in Papua New Guinea,  and areas high in soil fertility may be highly invasible. 

 

Hobu forest, gardens and piper (2).jpg (117106 bytes)   Hobu roadcut.jpg (151454 bytes)  Hagen and Tambul.jpg (69405 bytes)  Piper aduncum Markham valley 4.jpg (53307 bytes)  

Thumbnails (left to right): In Papua new Guinea Piper aduncum is common in 

secondary fallow vegetation; along road cuts; in the highlands near Mt Hagen; 

it can nowadays also been seen invading imperata grasslands (Markham valley)

 

 

Our research

Despite the widespread occurrence of Piper aduncum fallows in the humid lowlands of Papua New Guinea, there is no information available on the amount of biomass and nutrients. There is also no information available on the effects of Piper aduncum on the subsequent crop. Therefore, I started a series of experiments in 1996 that investigated these effects. The experiments were conducted in Hobu, near Lae, Papua New Guinea.  

 

Hobu_aerialview.jpg (97053 bytes) Piper with boy.JPG (27496 bytes) SE9_July_1997_2.jpg (84084 bytes) Litterbag.jpg (235599 bytes) SE9 Oct 1998.jpg (45332 bytes)

Thumbnails (left to right): The experimental site at Hobu; one-year old Piper aduncum trees; fallow experiment with gliricidia, piper and imperata; installation of litterbags in 

previous Piper aduncum plots; plots planted with sweet potato

In the first experiment we planted Piper aduncum plots and also plots with Gliricidia sepium and Imperata cylindrica (see thumbnails). The fallows were slashed after one year and sweet potato was planted. The effects of the fallows on sweet potato yield were investigated including nutrient dynamics, decomposition of the fallow biomass, nutrient uptake and soil chemical and physical changes. In another experiment the nutrient and biomass accumulation of Piper aduncum were followed for two years. Our results have shown that Piper aduncum accumulates large amounts of biomass and nutrients, particularly K, and that is has significant effects on the soil and its productivity, further details are here.

Hobu piper.jpg (62255 bytes)  Hobu 1998.jpg (94773 bytes)  SE8 roots mature piper 2.JPG (129298 bytes)  Open field day .jpg (64889 bytes)

Thumbnails (left to right): Piper aduncum garden Hobu; experimental site in 1998; 

Piper aduncum roots (shallow); farmers' open day at experimental site in Hobu

 

Our research focused on the soil and crop effects as well collecting some basic growth data on Piper aduncum. During the research we talked to many farmers and it became obvious that different farmers had different perceptions. Some liked and used its wood and leaves for various purposes whereas others felt it was unwanted fallow species.  A comment often heard was that "em mekim graun drai" (it dries the soil) - a finding which we proved in various experiments. No systematic investigation was undertaken on the socio-economics effects of Piper aduncum.

Thomas Siges, a MSc student from Wageningen University conducted fieldwork near Finschhafen (Saruwaged mountain range) from July to November 2003. He investigated the effects on the livelihoods of farmers in three different villages where Piper aduncum is common. Thomas interviewed a large number of farmers and asked them how they perceive the invasion of Piper aduncum, how they used its products and whether it  has changed their farming systems. The table below shows the significance of plant uses in three study villages.

X: Less frequently used.   XX:  Frequently used.  XXX: More frequently used.  (-): Not used.

From Siges, Hartemink, Hebinck and Allen (2005)

  

       Sanangac

      Sanzeng

    Tongucboc

Farm uses

 

 

 

Digging stick

XXX

X

-

making fences

XXX

XXX

XX

Stakes

XXX

XXX

XX

Pegs

XX

X

-

Tool handles

XX

XX

X

Soil retention structures

XXX

XXX

XXX

Shade

XX

XXX

X

Helps tillage

XXX

XXX

XX

Good fertilizer

XXX

XX

X

Burn debris

XXX

XXX

XXX

Weed control

 

XXX

X

X

Household uses

 

 

 

Cleaning stains on cooking utensils

XXX

XXX

XXX

Temporary platforms for resting

X

X

X

Ashes used as insecticide

X

X

XX

Leaves used as toilet tissues

XXX

XXX

X

Walking stick

              X 

                     X

                     X

Fire stick

XXX

XXX

XXX

Fuel wood

XXX

XXX

XXX

Rafters for houses

XXX

XXX

X

Poles for buildings

XX

X

-

Cleaning stains on teeth

XX

X

XX

Plant support

XXX

XXX

XX

Sticks for flower bed fences

                X

X

                 X

Making temporary ladders

 

XX

X

-

Services

 

 

 

Attracts wild animals

XX

XXX

XX

Improves soil fertility

X

XX

X

Dries of waterlogged soils

X

X

X

Provides shades

XX

XXX

X

Chases away the leech

X

XX

X

Host to other useful plants

-

X

-

Good sweet potato yield in short fallow

XXX

XX

XX

Provides wind breaks

XX

XX

XX

 

The table shows that piper is widely used. The invasion and dominance of piper has also some negative effects on rural livelihoods in the study area. This is mainly related to the destruction of the natural forest that is being replaced by secondary fallow vegetation dominated by piper, and in part it is due to the loss of natural secondary fallows vegetation. There is loss of social cohesion due the enhanced clearing of the forest, vanishing sacred places, disapperance of certain forest products and the destruction of the natural forest.

 

Publications 

Hartemink, A.E. 2006  Invasion of Piper aduncum in the shifting cultivation systems of Papua New Guinea. ISRIC - World Soil Information, Wageningen. [with a Foreword by Prof David Pimentel]. xiv+234 pp. ISBN 90 810628 1 6. More info here    (52 Mb)

Hartemink, A.E. 2006  Piper aduncum fallows in the lowlands of Papua New Guinea. In:  Voices from the Forest - Integrating Indigenous Knowledge into Sustainable Upland Farming. M. Cairns (Ed), The Johns Hopkins University Press, pp 190-194.

Siges, T., A.E. Hartemink, P. Hebinck & B.J. Allen 2005  The invasive shrub Piper aduncum and rural livelihoods in the Finschhafen area of Papua New Guinea. Human Ecology 33(6): 875-893

Hartemink, A.E. 2004  Nutrient stocks of short-term fallows on high base status soils in the humid tropics of Papua New Guinea. Agroforestry Systems 63: 33-43.

Hartemink, A.E. 2003  Integrated nutrient management research with sweet potato in Papua New Guinea. Outlook on Agriculture 32: 173-182.

Hartemink, A.E. 2003  Sweet potato yield and nutrient dynamics after short-term fallows in the humid lowlands of Papua New Guinea. Netherlands Journal of Agricultural Science 50: 297-319.

Hartemink, A.E. 2002  The invasion of Piper aduncum in Papua New Guinea: Friend or foe?  Flora Malesiana Bulletin 13: 66-68. Offprint

Hartemink, A.E. 2002  Nutrient stocks and nutrient cycling of fallows in the humid lowlands of Papua New Guinea. 17th World Congress of Soil Science, Vol. II: 691. IUSS, Bangkok. text      poster

Hartemink, A.E. 2001  Biomass and nutrient accumulation of Piper aduncum and Imperata cylindrica fallows in the humid lowlands of Papua New Guinea. Forest Ecology and Management 144: 19-32.

Hartemink, A.E. & J.N. O’Sullivan 2001  Leaf litter decomposition of Piper aduncum, Gliricidia sepium and Imperata cylindrica in the humid lowlands of Papua New Guinea. Plant and Soil 230: 115-124.

Hartemink, A.E., S. Poloma & J.N. O’Sullivan & 2001  Integrated nutrient management research with sweet potato at Hobu. In: Food Security in Papua New Guinea. R.M Bourke, M.G. Allen & J.G. Salisbury (Eds). ACIAR Proceedings no. 99, Canberra pp. 698-711.

Rogers, H.R. & A.E. Hartemink 2000  Soil seed banks and growth rates of an invasive species, Piper aduncum, in the lowlands of Papua New Guinea. Journal of Tropical Ecology 16: 243-251.

Hartemink, A.E., 1999  Piper aduncum fallows in the lowlands of Papua New Guinea. In: M. Cairns (Ed), Indigenous strategies for intensification of shifting cultivation in Southeast Asia. ICRAF, Bogor, pp. 193-196.  

  
 

www.alfredhartemink.nl