534 (Indah Wah - Distribution).cdr DISTRIBUTION OF INVASIVE PLANT SPECIES IN DIFFERENT LAND-USE SYSTEMS IN SUMATERA, INDONESIA 1,3* 2 3 4 5 INDAH WAHYUNI , SULISTIJORINI , SETIABUDI , ANA MEIJIDE , MIKI NOMURA , 6 6 3HOLGER KREFT , KATJA REMBOLD , SRI S. TJITROSOEDIRDJO and 3 SOEKISMAN TJITROSOEDIRDJO 1 Post Graduate Student of Plant Biology, Department of Biology, Faculty of Mathematics and Sciences, Institut Pertanian Bogor, Bogor 16680, Indonesia 2 Department of Biology, Faculty of Mathematics and Sciences, Institut Pertanian Bogor, Bogor 16680, Indonesia 3SEAMEO BIOTROP, Bogor 16134, Indonesia 4 Bioclimatology, University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany 5Graduate School of Life Sciences, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai 980-8578, Japan 6Biodiversity, Macroecology and Conservation Biogeography, University of Göttingen, Büsgenweg 1, 37077 Göttingen, Germany Received: 9 September 2015/Accepted: 29 July 2016 ABSTRACT Disturbances caused by the conversion of rain forests into agricultural systems provide an opportunity for the expansion of Invasive Plant Species (IPS). Bukit Duabelas National Park is one of the few remaining lowland forests in Jambi Province (Sumatera, Indonesia). The surrounding areas up to the national park borders have already been converted into jungle rubber agroforests as well as rubber and oil palm plantations which might lead to an increased spread of IPS into the forest. This study was aimed at compiling a list of IPS and determining their distribution and coverage of IPS in four land use systems (rain forest, jungle rubber, rubber and oil palm plantations). Spatial distribution patterns were investigated by creating a horizontal vegetation profile diagram for the permanent plots of the EFForTS project (Ecological and Socioeconomic Functions of Tropical Lowland Rainforest Transformation Systems, http://www.uni-goettingen.de/crc990). The dominance of IPS was determined using Important Value Index. A total of forty IPS were identified across the four land-use systems. The numbers of IPS were the highest in oil palm (28 species) and rubber plantations (27 species), and the lowest in jungle rubber (10 species). IPS were absent in the lowland rain forest. The diversity of IPS was influenced by environmental factors, especially canopy openness. IPS with the highest ground coverage were Dicranopteris linearis and Clidemia hirta. Both of them were found in all three land-use systems outside the rain forest when the forest canopy opens due to illegal logging or other human disturbances. Therefore, reforestation of disturbed areas is recommended to prevent the spread of IPS. Keywords: Invasive Plant Species (IPS), Bukit Duabelas National Park, Clidemia hirta, Dicranopteris linearis INTRODUCTION Sumatera is the second largest island in Indonesia and was once covered with forest (WWF 2010). Nowadays, the forests of Sumatera have been largely replaced by three major tree monocultures i.e. oil palms (Elaeis guineensis), rubber (Hevea brasiliensis) and Acacia mangium (WWF 2010). Bukit Duabelas National Park (BDNP) is one of the few remaining forests in the lowlands of Jambi Province in Sumatera under protection. Illegal logging and the conversion of the surrounding areas into jungle rubber, rubber and oil palm plantations might lead to an increase in Invasive Plant Species (IPS) in the forest. Disturbances in the ecosystem such as plantation development provide an opportunity for the BIOTROPIA 3 2 6 124 132 Vol. 2 No. , 201 : - DOI: 10.11598/btb.2016.2 . .3 2 534 * Corresponding author: indah@biotrop.org 124 expansion of invasive alien plants species ( R a g h u b a n s h i & T r i p a t h i 2 0 0 9 ) . Invasive plants are generally defined as plant species that are non-native to an ecosystem, and which may cause economic or environmental harm or adversely affect human health (CBD 2000). Invasive plants respond readily to human- induced changes of the environment, but may also cause environmental changes and economic damage through their dominance of the landscape (Pimentel 2011). In general, species distributions are determined by environmental conditions, biotic interactions, evolutionary change and dispersal ability. The success of invasive plants is assumed to be affected by several characteristics including: 1. high dispersal rate; 2. high fecundity; 3. high growth rate; 4. capability of vegetative reproduction; and 5. a high tolerance to various abiotic conditions including temperature, humidity and soil type (Velde et al. 2006). Anthropogenic disturbance facilitates the increases of invasive plant species richness (Gassó et al. 2009). Some invasive plants have a greater ability than others to colonize disturbed habitats (Freeman et al. 2015) and it is important to identify the most dominant IPS representing the biggest threat to invade natural ecosystems. IPS respond positively to natural or anthropogenic environmental disturbance. Natural disturbance and land use intensity facilitate the introduction of alien plant species in an area (Uddin et al. 2013). Light availability and exposed soil facilitate the establishment of IPS. The objectives of this study were to examine the diversity, distribution and coverage of IPS in four land-use systems (forest, jungle rubber, rubber plantation and oil palm plantation), to investigate the most dominant species and the environmental factors influencing IPS distribution. MATERIALS AND METHODS Study Site The study was carried out in Bukit Duabelas National Park (BDNP) and in surrounding villages in Jambi Province (Sumatera, Indonesia). BDNP covers 60,500 hectares and represents one of the few remaining lowland rainforests in Jambi Province with formal protection. The topography ranges from 50 to 438 m above sea level (asl). This forest is inhabited by the nomadic tribe “Suku Anak Dalam” (Orang Rimba). Traditional activities of the Orang Rimba include shifting cultivation, hunting, fishing and honey collection. The surrounding areas outside BDNP are covered by agricultural systems, namely jungle rubber (rubber agroforestry), rubber plantation and oil palm plantation. BO2 BF3 BF4 BJ4 BO4 BR4 BR3 BJ5 Figure 1 Study site in Jambi Province (Sumatera, Indonesia). The present study was carried out on the following plots: rain forest: BF3 & BF4; jungle rubber: BJ4 & BJ5; rubber plantation: BR3 & BR4; oil palm plantation: BO2 & BO4. (The map was created by Mohd. Zuhdi, Department of Soil Science of Universitas Jambi, Indonesia). 125 – Distribution of invasive plant species in different land-use systems Wahyuni et al. The research was conducted in four different land-use systems: lowland rainforest (F), jungle rubber agroforest (J), rubber plantation (R) and oil palm plantation (O). Forest plots were located inside BDNP and the other land-use systems in three surrounding villages, i.e. Dusun Baru, Lubuk Kepayang and Pauh. Vegetation surveys were carried out within the permanent plots (50 × 50 m) of the EFForTS project (Ecological and Socioeconomic Functions of Tropical Lowland R a i n f o r e s t Tr a n s f o r m a t i o n S y s t e m s, http://www.uni-goettingen.de/crc990). Two replicate plots were selected for each land-use system resulting in a total of eight plots (Fig. 1). The Abundance and Presence of IPS Horizontal profile diagrams for all invasive plants were created by projecting their coverage 2 onto the forest floor. Each 50 x 50 m plot was 2 divided into 25 subplots (10 × 10 m ) to simplify the calculation and delineation of invasive plant coverage. The coverage was drawn on graph paper with a scale of 1 : 100 in the field, and the sketches were then scanned and digitized in ArcView 3.3. The dominance of IPS was determined using Important Value Index (IVI), based on the frequency and coverage of invasive plants. To calculate the IVI, the percentage values of the relative frequency and relative dominance were summed and calculated with the following formulas (Cox 1972). Environmental Data Air temperature and air humidity were measured using thermohygrometers (Galltec Mela, Germany) installed in a meteorological station located in the center of each plot at 2 m above ground. Data were measured hourly and recorded in a data logger (LogTrans16-GPRS, UIT, Germany). The same station also measured soil temperature and soil moisture at 0.3 m depth (Trime-Pico 32, IMKO, Germany). For this analysis, the average of all data recorded for 16 months from June 2013 were used. The canopy cover was calculated from hemispherical photographs taken at 1.2 m above the ground from 32 positions within each plot (Canon EOS 700D SLR camera with a SIGMA 4.5 mm F2.8 EX DC circular fisheye lens). The photographs were taken in early morning (5:00 - 7.00 AM), late afternoon (5:00 - 7:00 PM), evenly overcast days to avoid direct sunlight entering the lens, as described in Drescher et al. (2016). To obtain non- overexposed, high contrast photographs, exposure was determined following the histogram-exposure protocol after Beckschäfer et al. (2013). The photographs were processed with the software “ImageJ” (Rasband 2014). Data Analysis Cluster analysis was carried out to compare the IPS community within the ecosystem. The cluster analysis was conducted based on IVI and calculated into similarity index, which was then converted into dissimilarity index with single linkage clustering. The formulas are as follows (McGarigal et al. 2000): where: IS = Similarity Index; A = total IVI of IPS in ecosystem A; B = total IVI of IPS in ecosystem B; C = the comparison of total IVI of IPS in ecosystem A and B; D = dissimilarity index. One-way ANOVA with Tukey-test were used to identify significant differences in the number and coverage of IPS as well as the differences of environmental data among the ecosystems. Principal Component Analysis (PCA) was conducted to observe the relationships between (1) (2) IVI = Relative Frequence + Relative Dominance Relative frequence Relative dominance Number of sample plots where a certain species was distributed Number of total sample plots x 100 % (3) Sum total of a certain species in the total sample plots Sum total cover of all species inthe total sample plots x 100 % = = 126 BIOTROPIA Vol. 23 No. 2, 2016 environmental factors and the number and coverage of IPS. One way ANOVA with Tukey- test and PCA were performed using XSLSTAT 2014 software (a Microsoft Excel add-in). RESULTS AND DISCUSSION Diversity of IPS within the Different Land- Use Systems A total of forty IPS were identified in the four land-use systems. Oil palm plantations had the highest richness of IPS (28 species), closely followed by rubber plantations (27 species). In jungle rubber agroforests, the number of IPS was much lower than in the monocultures (10 species), and IPS were absent in rain forest (Table 1 and 2). Cluster analysis separated the IPS community into three distinct groups (Fig. 2), but oil palm and rubber plantations had the most similar IPS communities. Oil palm and rubber plantations were characterized by a similarly intensive management resulting in comparatively high numbers and compositions of IPS. Principal component analysis results (PCA) showed that IPS coverage was higher in plots with high canopy openness (Fig. 3). The highest Table 1 Diversity of families, genera and species of invasive plants in four land-use systems Ecosystem type Number of family Number of genera Number of species Forest 0 0 0 Jungle rubber 6 10 10 Rubber plantation 13 24 27 Oil palm plantation 13 27 28 2Table 2 Average species numbers and total coverage (%) of IPS per plot (50 × 50 m ) in the four land-use systems Data BF (Forest) BJ (Jungle rubber) BR (Rubber plantation) BO (Oil palm plantation) Average of IPS number per plots (50 × 50 m) 0.00±0.00 8.00±2.83 19.50±0.71 21.00±9.52 Average of IPS total cover (%) per plots (50 × 50 m) 0.00±0.00 43.04±12.54 25.10±30.04 71.80±14.29 Environmental data Natural forest Jungle rubber Rubber plantation Oil Palm plantation Air temperature 24.47±0.44 25.05±0.38 25.58±0.36 25.44±0.72 Humidity 91.87±1.61 87.61±2.07 82.58±2.00 83.76±2.42 Soil moisture 25.00±2.40 30.39±2.08 43.54±5.52 35.39±4.73 Soil temperature 25.18±0.28 25.34±2.09 25.33±1.04 26.35±0.93 Canopy Openness 2.14±1.13 5.40±3.12 15.22±6.90 18.70±9.43 Table 3 Environmental data of the four land-use systems (forest, jungle rubber, rubber and oil palm plantations) Notes: Air temperature, humidity, moisture and soil temperature data are means of 10 replications±standard deviation. Data of canopy openness are means of 60 replications±standard deviation BO BR BJ BF 0.52 0.45 1.00 0.50 Figure 2 IPS community differences within ecosystems in Bukit Duabelas National Park separated by cluster analysis based on IVI values 127 – Distribution of invasive plant species in different land-use systems Wahyuni et al. coverage of IPS was found in oil palm plantation which also had the highest canopy openness (18.70%; Table 3). Based on Yaap et al. (2010), oil palm plantation, structurally, was less complex than natural forest, with a uniform tree age structure, lower canopy, less stable microclimate and intensively human disturbance. Dominant species in plantation are typically invasive species and pest (Yaap et al. 2010). Most of the IPS are shade intolerant. Fine (2002) reviewed that the number of invasive plant species was positively related to disturbance which increased light levels. Additionally, the number and coverage of IPS correlated with air temperature (Fig. 3); higher numbers of IPS were found where air temperature was high. Air temperature and light influence many plant processes. The interaction of this abiotic factor could influence growth rate, flowering period, seed dormancy and characteristic of plant morphology (Booth et al. 2010). In this study, air temperature and light are a strongly regulatory force for IPS distribution. Some invasive species are more successful in disturbed habitat because they are able to take advantage of the high light levels. Besides light intensity, Ibàñez et al. (2009) revealed that relatively warmer areas correlated with invasive plants occurrence. IPS were not found in the rain forest of Bukit Duabelas National Park. Their absence might be due to high canopy cover in the forest, leading to low light penetration as well as cooler and more humid conditions in the understory. These conditions might not support IPS growth. A more open canopy causes higher soil evaporation and increases in air temperature (Lambers et al. 2008) which may support IPS growth. Canopy openness and air temperature were lower in the forest than in the other land-use systems (Table 3). Junaedi and Dodo (2014) revealed that most IPS could not reach the forest interior where the canopy cover was still relatively intact. IPS prefer forest edges or forest gaps and are more successfully in infesting open and disturbed areas with high light levels where the native species are not as competitive. Disturbance, therefore, creates habitats that are more suitable for IPS than for native species. This shift from native to invasive species could influence the ecosystem balances. Thus, abiotic factors seem to be more important for the successful plant invasion than biotic factors (Booth et al. 2010; Peters 2001). Lower propagule pressure might be additional factor in the forest compared to the three other land-use systems. However, Peters (2001) showed an interesting interplay between abiotic conditions, soil disturbance and wild pig activity affecting the spread of C. hirta in a forest reserve in Malaysia. Figure 3 Principal Component Analysis (PCA) on relationship between the number and coverage of IPS to environmental factors: air temperature (AT), air humidity (AH), soil temperature (ST), soil moisture (SM) and canopy openness (CO) 128 BIOTROPIA Vol. 23 No. 2, 2016 Species composition of IPS differed between the four land-use systems (Table 4). More than 60% of the IPS in jungle rubber did not occur in rubber and oil palm plantations, while 30% of the IPS in rubber plantation were not found in oil palm plantation. Agroforestry systems such as jungle rubber are characterized by a relatively high diversity of native tree species and high canopy cover and this may cause lower numbers of IPSs. In contrast to jungle rubber, the tree crops in rubber and oil palm plantations are planted in regular distances of several meters to each other and the space in-between is weeded regularly. This condition appears to be most suitable for IPS and may also explain the higher similarity of IPS- communities in the two monoculture systems. Figure 4 Distribution pattern of IPS at oil palm plantation plot (BO2) Figure 5 Distribution pattern of IPS at jungle rubber plot (BJ5) Figure 6 Distribution pattern of IPS at rubber plantation plot (BR4) 129 – Distribution of invasive plant species in different land-use systems Wahyuni et al. 18 Lantana camara 0 0 0 2.95 19 Ageratum conyzoides 0 0 2.63 2.75 20 Mussaenda frondosa 0 0 2.64 2.73 21 Urena lobata 0 0 2.65 2.58 22 Uncaria cordata* 0 0 2.7 2.56 23 Bridelia insulana 0 0 2.65 2.48 24 Pennisetum polistachyon 0 0 0 2.48 25 Sporobolus diander* 0 0 0 2.46 26 Polygala paniculata 0 0 0 2.45 27 Stenochlaena palustris* 0 0 7.78 2.45 28 Borreria laevis 0 0 2.94 0 29 Chromolaena odorata 0 2.45 0 0 30 Cyperus difformis 0 0 2.64 0 31 Cyrtococcum acrescens 0 0 2.66 0 32 Cyrtococcum patens 0 0 7.47 0 33 Cyrtococcum trigonum 0 9.94 2.65 0 34 Dianella ensiflora 0 0 2.65 0 35 Fimbristylis dura 0 0 2.64 0 36 Macaranga triloba 0 0 2.78 0 37 Oplismenus compositus 0 6.57 0 0 38 Paspalum conjugatum 0 0 2.67 0 39 Tetracera scandens* 0 0 2.77 0 40 Tetracera indica* 0 14.05 0 0 Total 0 147.85 133.08 171.4 No. Species IVI (%) BF BJ BR BO 1 Clidemia hirta 0 34.23 7.3 45.76 2 Asystasia gangetica 0 0 2.64 11.76 3 Dicranopteris linearis* 0 28.84 17.45 11.25 4 Centhoteca lappacea 0 6.81 5.41 8.05 5 Axonopus compressus 0 0 5.53 7.83 6 Scleria ciliaris* 0 13.18 8.23 7.35 7 Melastoma malabathricum 0 12.62 5.47 6.7 8 Ottochloa nodosa 0 0 0 6.69 9 Paspalum dilatatum 0 0 5.51 5.81 10 Taenitis blechnoides* 0 12.79 5.41 5.74 11 Lygodium flexuosum* 0 6.38 0 5.46 12 Stachytarpheta jamaicensis 0 0 0 5.46 13 Breynia stipitata 0 0 5.36 4.94 14 Imperata cylindrica* 0 0 6.46 3.44 15 Borreria alata 0 0 5.38 3.16 16 Mikania micrantha 0 0 0 3.11 17 Stachytarpheta indica 0 0 0 3 Spatial Distribution Patterns of IPS within the Land-Use Systems The horizontal profile diagram provided information on current distribution of IPS. The highest coverage of IPS were in oil palm plantation (74%), followed by jungle rubber (45%) and rubber plantations (30%) (Fig. 4, 5 and 6, respectively). The invasive plants in jungle rubber were evenly distributed within the plots (Fig. 5). High coverage of invasive plants in oil Table 4 Important Value Index (IVI) of IPS in four land-use systems in Bukit Duabelas National Park. The species with the highest IVI are highlighted in bold; the native species were indicated by asterisk (*) 130 BIOTROPIA Vol. 23 No. 2, 2016 palm plantations is due to the relatively open canopy compared to other land-use systems. However, the invasive plant coverage in rubber plantation was lower than that in jungle rubber, whereas the canopy in jungle rubber was more closed than that in rubber plantations. The species dominance was analyzed based on the Important Value Index (IVI) (Table 4). Clidemia hirta was the most dominant species in jungle rubber followed by the native invasive species Dicranopteris linearis and Tetracera indica. C. hirta was also the most dominant species in oil palm plantation followed by Asystasia gangetica and D. linearis. In rubber plantations, the most dominant species was D. linearis, followed by Scleria ciliaris and Stenochlaena palustris. Based on the IVI values, the most important invasive species were D. linearis and C. hirta and this was also confirmed by the horizontal profile diagrams (Fig. 4, 5 and 6). Both species were found in all three agricultural land-use systems i.e. jungle rubber, rubber and oil palm plantations. The distribution pattern of C. hirta is spread generally random and in small colonies. The preferred habitat of C. hirta is humid tropical lowland (Dawson 2008). In some cases, C. hirta has been introduced intentionally into Botanical Gardens, such as Peradeniya (Sri Lanka) in 1894, Amani (Tanzania) in 1930 and Wahiawa (Hawaii) in 1941 (Dawson 2008). C. hirta is dispersed well due to its edible fruits being eaten by birds and other animals and its large numbers of seeds (more than 100 seeds/fruit). In addition, the seeds are able to stay dormant for 4 years in the soil (Dawson 2008). In its native range in South America, this species tends to grow in open areas (Gerlach 2006). Our plots were dominated by C. hirta up to the heavily shaded areas in the center of the jungle rubber plots (Fig. 5). Dicranopteris linearis is a native species and became weed because of deforestation and forest conversion into agricultural systems. In open canopy areas, the distribution pattern of D. linearis is clumped in a huge colony. However, D. linearis also occurred in jungle rubber where the canopy coverage was relatively high compared to that in rubber and oil palm plantations, D. linearis mainly grow in lighter conditions along the plot borders and in canopy gaps (Fig. 5). D. linearis is also abundant along roadsides and along the trail leading to the forest. CONCLUSIONS There were strong differences in species numbers and community composition of IPS in the four land-use systems studied. Canopy cover and associated changes in abiotic conditions were probably the main factor influencing IPS distribution. IPS infestation was higher in open areas such as oil palm and rubber plantations than that in areas with less light i.e. jungle rubber and rain forest. Canopy cover was the highest in natural forest where IPS were completely absent. D. linearis and C. hirta were found to be the most widely distributed IPS. Some activities that facilitated disturbances, i.e. land-use change, illegal logging and forest fire should be prevented. Immediate action of reforestation of disturbed areas in the national park should be applied. The IPS which were established in the plantations should also be prevented from spreading into the national park. It is necessary to prohibit visitors entering the national park from the fully IPS invaded pathway from the plantations. Immediate action needed to destroy IPS infestation to BDNP. ACKNOWLEDGEMENTS The authors are grateful to the Ministry of Research, Technology and Higher Education (RISTEKDIKTI) for research permission in Indonesia. Sincere thanks also due to the staff of Bukit Duabelas National Park, the landowners of our research plots and Universitas Jambi for the facilities and working permit issuance for Bukit Duabelas National Park. Thanks to Saiful Bachri, Defra Nurdiansyah and Anton Radiansyah for their assistance with data collection. 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