No abstract

Economically feasible strategies to cope with invasive species are urgently needed. Plant density can be increased to reduce competitive effects on target plants. This study indicates that increasing native plant density can be used to reduce the effect of invasive Ageratina adenophora. Seedlings of an indigenous tree species, Schima wallichii, were grown in pots containing uninvaded or invaded soil, with or without A. adenophora leaf litter on the soil surface. Schima wallichii seedlings were also grown at four densities under four levels of A. adenophora leaf litter. Root and shoot biomass and length were measured as response parameters in both bioassays. Schima wallichii growth was inhibited by A. adenophora leaf litter and invaded soil. High litter levels reduced S. wallichii root length and dry weight at low plant densities. The inhibition disappeared at high S. wallichii plant densities. As A. adenophora did not inhibit S. wallichii growth at high plant densities, adjustments of seedling density should be studied as a possible management strategy for invasion by A. adenophora and potentially by other exotic plant species. As density-dependent growth inhibition is the key characteristic of chemical interference, we propose that phytotoxins contribute to A. adenophora invasion particularly at low densities of native seedlings.

Background: Nepal has diversity in castes and ethnic groups where the indigenous people whose major population live in rural areas depend on traditional practices of health care system. Among 125 caste/ethnic groups in Nepal Kisan is one of the endangered ethnic group confined at Jhapa district of the country. Several studies have documented traditional knowledge of different indigenous groups of Nepal but such study was lacking in case of Kisan.Methods: Interview and group discussions were conducted in the Kisan communities in three village development committees and one municipality of Jhapa district of eastern Nepal. A total 91 individuals including traditional healers were interviewed. Transect walk survey was conducted to identify the medicinal plants with the key informants during the field study. Results:The study reported 40 species medicinal plants belonging to 32 families tradionally used by Kisan community for the treatment of 34 kinds of diseases. Traditional knowledge is found associated with Kisan's religious practices and believes. The knowledge is confined to the elderly people and traditional healers in the community. Conclusion:Kisan indigenous people have a sound knowledge on medicinal plants of their locality that also reflects their religious practices and believes. As the knowledge is limited to the elderly people and only to the traditional healers there is gap of knowledge transfer to young generations. This study provides a baseline for further research and studies on medicinal plants.

The response of native plants to allelopathic interference of invasive species may differ from species to species. In this study, the phytotoxic effects of Ageratina adenophora were tested on two native shrubs (Osbeckia stellata and Elsholtzia blanda) of Nepal. Both the shrubs were grown in pots under treatments of A. adenophora fresh leaves and root leachates, and litter. Then, the seedling length and biomass were compared among the treatments. The results show that A. adenophora litter has stimulatory effects but the leachates from fresh leaves and root are phytotoxic to the growth and development of native shrubs. Infrared Spectroscopy (IR) analysis confirmed the presence of O–H (Hydroxyl), N–H (Amines), C≡C (Alkynes), and C–H stretching (Aromatic) or C–O–C stretching (Ethers) in the leachates representing harmful allelochemicals. The invaded soil by A. adenophora had low pH and a high amount of organic matter, total nitrogen, phosphorus, and potassium than the uninvaded soil. The results indicate that the native O. stellata and E. blanda are harmed by A. adenophora in nature by leaching of allelochemicals and probably by reducing the soil pH. Overall, this study has provided valuable insights regarding the effects of A. adenophora invasion on native shrubs and revealing the potential mechanism of its invasiveness.