3 Banko Janakari, Vol 31 No. 1, 2021 Pp 3‒11https://doi.org/10.3126/banko.v31i1.37337 Assessment of invasion of Ageratina adenophora in the plantation forest of Nepal 1 Forest Research and Training Centre, Pokhara, Gandaki Province, Nepal. *Email: raj_malla@yahoo.com 2 Forest Research and Training Centre, Kathmandu, Nepal 3 International Centre for Integrated Mountain Development, Lalitpur, Nepal Large-scale plantations of pine species were done in the bare hills of the Middle Mountain region of Nepal during the early 1980s. There is a growing concern on the sustainability of the planted pine forests in the country due to the presence of invasive alien plant species (IAPS). Invasive alien plant species are considered as one of the drivers of forest degradation and deforestation. Ageratina adenophora is one of the problematic IAPS found in the planted pine forests throughout the country. In this study, we employed different treatments to control the invasion of A. adenophora in the planted pine (Pinus patula) forest. The research design included four different treatments, viz., (i) control, (ii) stem felling, (iii) floor clearance, and (iv) stem felling cum floor clearance in one block (Block I), which was replicated in another block (Block II). The data were collected using circular sample plots with 2m radius. The ANOVA and TukeyHSD Tests were applied during the analysis process so as to determine the effects of treatments on invasion of A. adenophora. The "floor clearance treatment" was found to be significantly effective to reduce the presence of A. adenophora in the planted pine forest. On the contrary, the "opening of forest cover treatment" was found to be conducive to this invasive species to invade the area. The "stem felling cum floor clearance treatment" could be an effective strategy to control invasion of A. adenophora in planted forest, but as it demands a high cost, it is likely to be appropriate for small forest areas where promotion of regeneration is of high priority. Keywords: Ageratina adenophora, floor clearance, invasion, Pinus patula, treatment R. Malla 1*, R. R. Aryal 2 and S. Ranabhat 3 Received : 10, April, 2021 Revised : 25 April, 2021 Accepted : 26, May, 2021 Published : 30, May, 2021 Large scale plantation program was initiated in the Middle Mountain region of Nepal during the early 1980s (Gilmour et al., 1990). More than 370,000 hectares of plantations in the bare hills were successfully established with different pine species including native Pinus roxburghii, P. wallichiana and alien P. patula (DoF, 2012) as these species can survive and grow well on the areas with very poor soil (Jackson, 1994). According to the FAO (2015), World’s planted forest has increased by over 105 million ha since 1990 resulting in seven percent of the total forests. According to the then Nepal Australia Community Resource Management and Livelihood Project (NACRMLP), a total of 23,404 hectares of plantations had been established in the Sindhupalchowk and Kabhrepalanchok districts of Nepal since the late 1970s (NACRMLP, 2006), mostly dominated by pine species (Hunt et al., 2001) among which P. patula covers almost 75% of the total pine plantations (ERI, 2011). Planted forests share many ecosystem services produced by native mixed forests, but the extent https://orcid.org/0000-0002-3604-2259 https://orcid.org/0000-0001-5458-5380 https://orcid.org/0000-0003-0992-4405 Banko Janakari, Vol 31 No. 1 4 Malla et al. of sharing is determined by its management (Vihervaana et al., 2012). Both the plantations and natural forests have advantages and disadvantages. However, there is a growing concern on the sustainability of planted forests (Powers, 1999), and some of the issues associated with the stands of pure and mixed species have been still undetermined (Jactel et al., 2002). According to the latest forest resource assessment in Nepal, almost 45% of land is occupied with forest cover, including planted and natural forest (DFRS, 2015). However, forest degradation and deforestation has undergone due to many reasons. Invasive alien plant species (IAPS) are considered as one of the drivers of forest degradation (MFSC, 2009), threat to biodiversity conservation (MFSC, 2014) and has adverse effect on forest regeneration (Shrestha, 2019a). Invasive alien species have negatively affected forest ecosystems, wetlands, protected areas and agro-ecosystems by threatening both biodiversity and people’s livelihood (MFSC, 2014). The impact of invasive alien species is further worsened by ongoing climate change resulting in increase of frequency and intensity of biological invasion (Simberloff, 2000) and severe impact on high altitude forest (Wang et al., 2019) . Limited studies have presented the ranges of impacts of IAPS from habitat degradation of endangered wildlife, e.g., one- horned rhinoceros (Murphy et al. 2013) to problems in the livelihood of rural communities (Rai et al., 2012; Shrestha et al., 2019b). It has been considered globally as the second major cause of biodiversity loss after habitat degradation (Glowka et al., 1994; Bellard et al., 2016). There are, altogether, 26 IAPS in Nepal, and A. adenophora is one of them. It is commonly found in forest, shrub land, grassland and agroecosystem at the altitudinal range of 400−2600m (Shrestha, 2019). The invasion of A. adenophora is more severe at the edges of the forest and agricultural lands and also the wetlands (Baral et al., 2013). In forest and shrub lands, A. adenophora is considered as one of the major problematic species including Chromolaena odorata, Lantana camara and Mikania micrantha (Shrestha, 2019a). Management of invasive species involves three basic strategies i.e. prevention, eradication and control (Radocevich et al., 2009). Effects of invasion and initiatives to manage IAPS and studies on their dynamics have been very limited (Bhatterai et al., 2014). Therefore, this study focused on assessing different treatments which help control invasion of A. adenophora in the planted pine forest. Methods and materials Study area The study was carried out at two sites within the Sangaswoti Deurali Lauri Community Forest (SDLCF) of Kabhrepalanchok district (Bagmati Province) situated in the middle-hill region of Nepal (Figure 1). Figure 1: Location of study sites in Kabhrepalanchok district of Nepal The SDLCF is located at an altitude of over 2200m from the sea level, and is dominated by P. patula associated with a few other tree species. The study sites consist of mainly the pine species planted in the early eighties. The mature stocks of P. patula and P. wallichiana were present in the study sites; around 95% of the stems were of P. patula. The practice of open grazing before the study had led the area prone to biological invasion. The forest grounds Banko Janakari, Vol 31 No. 1 5 Malla et al. of the study sites were invaded mostly by invasive A. adenophora. In Nepal, distribution of A. adenophora is mostly absent in the Terai region (i.e. a wide belt of flat land along the southern border), and it occurs occasionally in the Siwalik region, particularly in western Nepal. The species is widespread in the Middle Mountain region (Shrestha, 2019a). Two blocks (Block I and Block II), each with the area of 2 ha, were established within the SDLCF for the purpose of the study. Each block was further divided into four treatment-plots, each with the size of 0.5 ha (100m × 50m) at the spacing of 5m as buffer (Figure 2) so as to apply four different treatments, viz., (i) control, (ii) stem felling, (iii) floor clearance, and (iv) stem felling cum floor clearance (abbreviated with T0, T1, T2 and T3, respectively). Pl ot u nd er tr ea tm en t T 0 B uf fe r Pl ot u nd er tr ea tm en t T 1 B uf fe r Pl ot u nd er tr ea tm en t T 2 B uf fe r Pl ot u nd er tr ea tm en t T 3 Figure 2: Establishment of treatment-plots within a block in the study sites Note: T0=Control, T1=Floor clearance, T2=Stem felling (10%), T3= Stem felling (10%) cum floor clearance. Data collection After establishing the treatment-plots in the study sites, the aforementioned four treatments (T0, T1, T2 and T3) were applied every year for three consecutive years (FY 2073/074−2075/076). Circular sample plots of 2m radius were laid out systematically at the spacing of 10m × 5m (length × breadth) inside each treatment-plot to collect the coverage of A. adenophora. Altogether, 39 sample plots were established within the four treatment- plots to collect the necessary data. All the circular sample plots were divided into four parts at cardinal directions to record the cover percentage of A. adenophora. In between the treatment-plots, buffers of 5m width were created so as to neutralize the buffer effects on the plantations within the treatment-plots. The presence of A. adenophora in the treatment- plots was recorded on the basis of ocular estimation. Data analysis The data collected from the field were analyzed separately for each block. The coverage of the IAPS in each sample plot within each treatment- plot are highlighted in Figure 3. The mean and standard deviation of the coverage percent of the IAPS were calculated for all the treatment-plots. The significant effects of treatments in each block was determined by applying the ANOVA test. Besides, the TukeyHSD test was also applied to compare the means of the target variables. All the statistical analyses were conducted in R program (R Core Team, 2019). Similarly, the distribution of the IAPS, whether homogenous or heterogeneous in each treatment-plots, was analyzed in graphs (Figures 3 and 4). Moreover, the cost incurred for applying treatments in the blocks was also calculated using the number of labors and their per day rate as per the government norms; however, only the labor cost was considered in the analysis. Results Number of pine stems In the establishment year, the number of pine stems in both the blocks were recorded. Every year, 10 percent of the stems were removed from the treatment-plots T2 and T3 within both the blocks in course of the application of treatments (Table 1). Banko Janakari, Vol 31 No. 1 6 Malla et al. Table1: Number of pine stems after the treatments in different years Treatment Before treatment 2015 2016 2017 Block I Block II Block I Block II Block I Block II Block I Block II Control (T0) 205 212 205 212 205 212 205 212 Floor clearance (T1) 192 159 192 159 192 159 192 159 Stem felling (10% per year) denoted by T2 161 170 145 153 129 136 113 119 Stem felling (10% per year) cum floor clearance denoted by T3 154 174 139 157 124 140 109 123 Distribution of A. adenophora The distribution of A. adenophora was not similar in all the treatment-plots. The effects of treatment can be easily noticed in Figure 3 and Figure 4. The treatment-plots T1 and T3 followed some linear pattern as compared to the treatment-plots T0 and T2 with the lower level of the presence of A. adenophora in both the blocks. The results showed that the floor clearance work had important role in reducing the presence of A. adenophora. Figure 3: Distribution of A. adenophora in Block I Banko Janakari, Vol 31 No. 1 7 Malla et al. Figure 4: Distribution of A. adenophora in Block II Coverage of A. adenophora In the case of Block I, the mean coverage percent of A. adenophora was found to be the highest (59.61%) in the controlled plot T0 followed by the treatment- plots T2 (44.23%), T3 (30.76 %), and T1 (26.28%), respectively (Table 2). Similarly, the standard deviation of the coverage of A. adenophora was found to be the highest (20.24) in the treatment-plot T2 followed by the controlled plot T0 (18.68), and the treatment-plots T3 (10.67) and T1 (5.58), respectively within the same block. Table 2: Mean and standard deviation of the IAPS coverage Block Treatment Mean cover (%) I T0 59.61 (18.68) T1 26.28 (5.58) T2 44.23 (20.24) T3 30.76 (10.67) II T0 72.43 (22.79) T1 29.48 (9.71) T2 83.97 (14.60) T3 30.12 (14.74) Note: Standard Deviations in parentheses In the case of Block II, the mean coverage of the IAPS was found to be the highest (83.97%) in the treatment-plot T2 followed by the controlled plot T0 (72.43%) and the treatment-plots T3 (30.12%) and T1 (29.48%), respectively. Similarly, the standard deviation of the IAPS coverage was found to be the highest (22.79) in the controlled plot T0 followed by the treatment plots T3 (14.74), T2 (14.60) and T1 (9.71), respectively (Table 2). The result showed that the mean coverage of A. adenophora was higher in the treatment-plots where floor clearance had not been performed. The effect of floor clearance work (either solely or accompanied with stem felling) had reduced the presence of A. adenophora in the study sites. The trend of the presence of A. adenophora in both the blocks was more or less similar. The ANOVA Test indicated that there was significant effect of the "floor clearance treatment" on the presence of A. adenophora in both the blocks- Block I (f<2e-16) and Block II (f< 2e- 16). It confirms that the floor clearance on the pine plantation forest helps reduce the presence of this invasive species significantly. On the other hand, the TukeyHSD Test in R Program (which was performed to test the multiple comparison of Banko Janakari, Vol 31 No. 1 8 Malla et al. Table 3: Comparison of the means of different treatments based on TukeyHSD Test Block I Treatments Difference Lwr Upr p adj T1−T0 −33.33 −42.17 −24.48 0.0000 T2−T0 −15.38 −24.22 −6.54 0.0000 T3−T0 −28.84 −37.69 −20.00 0.0000 T2−T1 17.94 9.10 26.79 0.0000 T3−T1 4.48 −4.35 23.33 0.5529 T3−T2 −13.46 −22.30 −4.61 0.0006 Block II Treatment Difference Lwr Upr p adj T1−T0 −42.98 −52.46 −33.43 0.0000 T2−T0 11.53 2.02 21.05 0.0104 T3−T0 −41.51 −51.09 −31.93 0.0000 T2−T1 54.48 44.97 64.00 0.0000 T3−T1 1.43 −8.14 11.00 0.9799 T3−T2 −53.05 −62.62 −43.47 0.0000 the means) showed that all the treatments were significant except T3 and T1 in both the blocks (Table 3). The treatment-plots T1 and T3 with the "floor clearance treatment" showed similar results. Cost associated with removal of IAPS The uprooting of A. adenophora including the removal of pine needles during floor clearance in the treatment-plots required significant labor cost. The cost incurred during the floor clearance treatment was NRs 13,800.00 (~ US $120) per ha per year. A total of 6 ha area was cleared in the treatment-plots in course of floor clearance during the study period of three years resulting expenditure of NRs 82,800.00 (~ US $720). The cost incurred in the removal of A. adenophora had, no doubt, contributed in lowering the presence of A. adenophora in the study sites (Table 4). Table 4: Cost of treatment (floor clearance) for 3 years in the study sites Block Treatment Cost/ha/yr. (NRs.) Total area (ha) Cost (NRs.) A. Adenophora coverage (%) I T0 - - - 59.61 T1 13,800 (~ US $120) 0.5 × 3 = 1.5 20,700 (~ US $180) 26.28 T2 - - - 44.23 T3 13,800 (~ US $120) 0.5 × 3 = 1.5 20,700 (~ US $180) 30.76 II T0 - - - 72.43 T1 13,800 (~ US $120) 0.5 × 3 = 1.5 20,700 (~$ US 180) 29.48 T2 - - - 83.97 T3 13,800 (~ US $120) 0.5 × 3 = 1.5 20,700 (~$ US 180) 30.12 Total 6.0 82,800.00 (~ US $ 720) - Banko Janakari, Vol 31 No. 1 9 Malla et al. Discussion Both anthropogenic and natural factors are responsible for the introduction and spread of IAPS (Rai et al., 2012). In order to control population of A. adenophora, one of the problematic IAPS, different control measures (i.e. biological, chemical and mechanical) have been in practice (Poudel et al, 2019). Manual removal of A. adenophora from the forest helps control its population to certain level than leaving the forest as it is. In the large area, it may not be feasible as it demands more budget. However, it can be financially viable for a small forest area that needs regeneration of native tree species. Impact of invasive alien plant species on forest regeneration has been reported in many studies. It is shown that invasive species has stronger inhibitory effects on tree seedling establishment and growth compared to native understory species (Nilsson et al. 2000; Wallstedt et al. 2005). High abundance of A. adenophora inhibits the growth of seedlings of native canopy trees (Denggao et al., 2018), detrimental impact on local biodiversity and negative impact on local communities (Baral et al., 2013). Thus, it is important to maintain the population of A. adenophora to minimize its detrimental effect on native tree regeneration. Invasion of A. adenophora mostly occurs in open land such as grass land, agriculture land, open wood land, forest margins, etc. (Baral et. al., 2013) has reported that open areas are conducive for the establishment of A. adenophora, and it is the first species to colonize the degraded areas preventing other plants to grow. Our result also showed that the invasion of A. Adenophora had positive relation with the opening of forest. It was noticed that the opening of the forest by felling the stems triggered the IAPS to invade the area. Floor clearance work is associated with the removal of A. adenophora and other pine needles in a pine plantation forest assuming that it controls the population of IAPS. Our results showed that the floor clearance work had significant effect on maintaining the population of A. adenophora at minimum level as compared to the other treatments. The floor clearance accompanied by stem felling did not produce better result than the floor clearance alone. Opening of forest (canopy gap) makes the environment favorable for IAPS to dominate other vegetation (Vargas et al., 2013). On the contrary, increasing tree canopy closure in the forest suppress growth of IAPS (Khaniya & Shrestha, 2020). The best option to control the population of A. adenophora in pine plantation forest could be a periodic removal of this invasive species from the forest ground with least disturbance to canopy cover of the forest. The cost associated with the removal of A. adenophora could be costly for large area in terms of labor cost. However, in the context of Nepal, most of the forests (47.5%) are managed by the communities belonging to 4.2 million households (DFRS, 2015; DoF, 2017). So, mobilization of communities could be a better option for rejuvenation of small degraded forest areas from IAPS. In this regard, Khania & Shrestha (2020) have also suggested to control IAPS through participatory way. Conclusion Invasion of IAPS in the forest area is a problem for the existence of native species. In the planted pine forest, invasion of A. adenophora is common in Nepal. The condition is further exacerbated when it gets conducive environment to spread all over. Invasion of A. adenophora has positive relation with the opening of forest cover. Creating gaps by stem felling in the planted pine forest offers IAPS to invade the area. In order to control its population, human intervention is vital. Periodic removal of this invasive species from the forest floor helps reduce its intensity of invasion. Floor clearance along with maintaining forest cover is one of the best means to control the population of A. adenophora at minimum level in the planted pine forest. The cost for floor clearance periodically in planted pine forest is high for the developing countries like Nepal. However, it could be applicable to small forest areas where the regeneration of desired species is of high priority. Banko Janakari, Vol 31 No. 1 10 Malla et al. Acknowledgements This article has been prepared on the basis of the data collected from the research plots established by the then Department of Forest Research and Survey (now the Forest Research and Training Centre, FRTC) within the SDLCF of Kabhrepalanchok district in 2014. We are thankful to the FRTC for providing the necessary data as well as financial support to accomplish the study. Besides, we would like to thank all the technical staff involved in the fieldwork. References Baral, S., Adhikari, A., Khanal, R., Malla, Y., Kunwar, R., Basnyat, B., Gauli, K. and Acharya, R. P (2013). Invasion of alien species and their impact on different ecosystems of Panchase Area, Nepal. Banko Janakari 27 (1): 31−42. Bellard, C., Cassey, P. and Blackburn, T. M (2016). Alien species as a driver of recent extinctions. Biology letters 12 (2), 20150623 Bhattarai, K. R., Måen, I. E. and Subedi, S. C (2014). Biodiversity and invasibility: distribution patterns of invasive plant species in the Himalayas, Nepal. Journal of Mountain Science 11 (3): 688–696. Denggao, F., Xiaoni W., Huang, N. and Changqun D (2018): Effects of the invasive herb Ageratina adenophora on understory plant communities and tree seedling growth in Pinus yunnanensis forests in Yunnan, China. Journal of Forest Research. https:// doi.org/10.1080/13416979.2018.1429202 DFRS (2015). State of Nepal's Forests. Forest Resource Assessment (FRA) Nepal, Department of Forest Research and Survey. Kathmandu, Nepal. DoF (2012). Community Forest Data Base. Community Forestry Division, Department of Forest, Ministry of Forest and Soil Conservation, Kathmandu, Nepal. DoF (2017). Hamro Ban. Annual Report of Fiscal Year 2016−2017, Department of Forest. Kathmandu, Nepal. FAO (2015). Global Forest Resources Assessment (2015). Food and Agriculture Organization of the United Nations, Rome. Gilmour, D., King, G., Applegate, G. and Mohns, B. (1990). Silviculture of plantation forest in central Nepal to maximize community benefits. Forest Ecology and Management 32: 173−186. Glowka, L., Burhenne-Guilmin, F. and Synge, H. (1994). A Guide to the Convention on Biological Diversity. IUCN, Gland, Switzerland. Hunt, S., Dangal, S. and Shrestha, S. (2001). The Impact of Stocking on the Growth of Pine Plantations in the Mid-hills of Kabhrepalanchok and Sindhupalchok Districts. Jactel, H., Goulard, M., Menassieu, P. and Gouzon, G. (2002). Habitat diversity in forest plantations reduces infestations of the Pine stem borer Dioryctria sylvestrella. Journal of Applied Ecology 39: 618−628. Jackson, J. (1994). Manual of Afforestation in Nepal. Forest Research and Survey Centre, Ministry of Forests and Soil Conservation, Kathmandu, Nepal. Khaniya, L. and Shrestha, B. B. 2020. Forest regrowth reduces richness and abundance of invasive alien plant species in community managed Shorea robusta forests of central Nepal. Journal of Ecology and Environment 44 (1):1−8. MFSC (2009). Study on Invasive Alien Species (IAS) as Drivers to Deforestation and Degradation of Forests in Different Physiographic Regions of Nepal. REDD Cell, Ministry of Forests and Soil Conservation, Babarmahal, Kathmandu. Banko Janakari, Vol 31 No. 1 11 Malla et al. MFSC (2014). Nepal National Biodiversity Strategy and Action Plan 2014−2020. Ministry of Forests and Soil Conservation, Kathmandu, Nepal. Murphy, S. T., Subedi, N., Gnawali, S. R., Lamichhane, B. R., Upadhyay, G. P., Kock, R. and Amin, R. (2013). Invasive Mikania in Chitwan National Park, Nepal: the threat to the greater one-horned rhinoceros Rhinoceros unicornis and factors driving the invasion. Oryx 47: 361−368. NACRMLP (2006). Thinning Guidelines for Pinus patula and Pinus roxburghii Plantations in Nepal. Nepal Australia Community Resource Management and Livelihood Project, Kathmandu, Nepal. Nilsson, M. C., Zackrisson, O., Sterner, O. and Wallstedt, A. (2000). Characterization of the differential interference effects of two boreal dwarf shrub species. Oecologia. 123: 122–128. Poudel, A. S., Jha, P. K., Shrestha, B. B. and Muniappan, R. (2019). Biology and management of the invasive weed Ageratina adenophora (Asteraceae): current state of knowledge and future research needs. Weed research 59 (2): 79–92. R Core Team (2019). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project. org/. Radocevich, S. R., Prather, T., Ghersa, C. M. and Lass, L. (2009). Implementing science based invasive plant management. In: Management of Invasive Weeds. (ed.) Inderjit. Springer Science + Business Media B.V. pp 345−359. Rai, R.K., Scarborough, H., Subedi, N. and Lamichhane, B. (2012). Invasive plants - Do they devastate or diversify rural livelihoods? Rural farmers’ perception of three invasive plants in Nepal. Journal of Nature Conservation 20: 170–176. Shrestha, B. B. (2019a). Management of invasive alien plant species in Nepal: current practices and future prospects. In: Tropical Ecosystems: Structure, Functions and Global Change. S.C. Garkoti, S. Van Bloem, P. Z. Fule and R. L. Semwal (Eds.). Springer Nature Singapore. pp. 45−68. Shrestha, B. B., Shrestha, U. B., Sharma, K. P., Thapa-Parajuli, R. B., Devkota, A. and Siwakoti, M. (2019b). Community perception and prioritization of invasive alien plants in Chitwan- Annapurna Landscape, Nepal. Journal of environmental management 229: 38–47. Simberloff, D. (2000). Global climate change and introduced species in United States forests. The Science of the Total Environment 262: 253–261. Vargas, R., Gartner, S., Alvarez, M., Hagen, E. and Reif, A. (2013). Does restoration help the Conservation of the threatened forest of Robinson Crusoe Island? The impact of forest gap attributes on endemic plant species richness and exotic invasions. Biodiversity Conservation 22: 1283–300 Vihervaana, P., Marjokorpi, A., Kumpula, T., Walls, M. and Kampinnen, M. (2012). Ecosystem services of fast-growing tree plantations. A case study on integrating social valuations with land-use changes in Uruguay. Forest Policy and Economics 14: 58–68. Wallstedt, A., Gallet, C. and Nilsson, M. C. (2005). Behaviour and recovery of the secondary metabolite Batatasin-III from boreal foresthumus: influence of temperature, humus type and microbial community. Biochemistry System Ecology 33: 385–407. Wang, C. J., Li, Q.F. and Wan, J. Z. (2019). Potential invasive plant expansion in global ecoregions under climate change. PeerJ 7: e6479. DOI 10.7717/peerj.6479.