MORPHOLOGICAL PLASTICITY AND COMPETITIVE ABILITY OF AUSTROEUPATORIUM INULIFOLIUM (original) (raw)
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PLASTIC RESPONSES OF AUSTROEUPATORIUM INULIFOLIUM UNDER VARYING SOIL RESOURCE LEVELS
Invasive Alien Species (IAS) has become to a major threat to the natural and semi natural ecosystems of Sri Lanka. Among them, Austroeupatorium inulifolium (Asteraceae) is silently invading hilly areas in the Wet Zone of Sri Lanka. In the present experiment we tried to identify some eco-physiological traits of Austroeupatorium which could amend their invasive behavior and potential. A pot experiment was conducted under glasshouse conditions where Austoeupatorium seedlings were subjected to different intra-specific competition (1, 2 and 4 individuals per pot). Half the number of pots was 'enriched' with nutrient solution (once per a week for 5 weeks) and the other half remained with no added nutrients ('un-enriched'). Plants were then harvested, oven dried before taking the dry shoot and roots weights to calculate root weight ratio, root:shoot ratio and relative growth rate. Austroeupatorium seedlings showed a decreasing trend of growth from low to high density treatments under 'enriched' conditions indicating high intra-specific competition among plants under enhanced soil resource availability. Plants did not show any intra-specific competition when plants are exposed to resource-poor situations. Root weight ratio (RWR) and root:shoot ratios were significantly lower in seedlings exposed to medium density level (x2) compared to other two treatments only when plants are enriched with nutrients. This indicates lower allocation of biomass into below-ground parts than the above-ground parts when plants are subjected to less intra-specific competition under fertile conditions.
Ceylon Journal of Science, 2018
A light loving invasive shrub, Austroeupatorium inuli-folium has been spreading many land use types in the Knuckles Forest Reserve (KFR) in Sri Lanka, including man-made grasslands. In developing countries, there are limitations of using novel technologies to quantify and track the distribution of invasive species due to high costs and lack of facilities. This is a setback for their early detection and to introduce effective control measures. This pilot study attempted to map the distribution of A. inulifolium in man-made grasslands in KFR using high spatial multispectral images. Unsupervised, supervised and knowledge-based classifications were performed to quantify the spatial distribution of A. inulifolium in ERDAS Imagine. The results generated comparable results of the extent of area under A. inulifolium by using the unsupervised (108 ha), supervised (94 ha) and knowledge-based classifications (93 ha). They were 18, 15 and 15% from the total area selected for the study (622-646 ha), respectively. The results indicated the suitability of high spatial multispectral imageries in quantifying the spatial distribution of A. inulifolium. Further studies are recommended to investigate long-term changes in invasive plant population using multi temporal satellite data.
Chapter 19 Research on invasive alien plants in Sri Lanka
Sri Lanka has a short history on invasive alien plants (IAP) as much of the work on invasive alien species (IAS) was initiated after organization of the first national symposium in 1999. During the past ten years, IAP in Sri Lanka received considerable attention by scientists and as a result several research publications were released. An analysis was done using 124 publications on IAP in Sri Lanka resulted over the past ten years in order to identify the aspects/subject areas that have been given priority in past research, species that have been addressed in detail, specific locations in which studies on IAP have been conducted and the degree of involvement of the government and non government sectors in IAP research. The total number of publications per year was also observed. Majority, (73%) of the publications on IAP of the last decade was based on field and laboratory studies and 27% were reviews. Impacts, control and management of IAP were well addressed, but not many publications were focused on economical impacts. Aspects such as genetics/germplasm studies, reproductive biology, germination, establishment and propagation methods, distribution and spread, potential uses, allelopathic compounds, legal issues and studies on public awareness were paid little attention while physiology and competitive ability of IAP and detection of new or potential IAP and their locations were fairly investigated. Only 22 IAP have been subjected to autecological studies. Plant species such as Lantana camara, Mimosa pigra, Parthenium hysterophorus, Prosopis juliflora, Cuscuta chinensis were popular examples. Eighty three per cent of the publications were focused on terrestrial species although aquatic species were considered as the most problematic group of IAP. Locations such as Udawattekele forest reserve and Hantana range were popular study sites among the 14 areas in which IAP work was based on. Authors of many of the publications were affiliated to government institutions and the involvement of the university community on IAP research was 60%. Frequency of publications on IAP were high in years 1999, 2000 and 2008 indicating that organization of national symposia has provided a better opportunity in disseminating findings of IAP work in Sri Lanka. However, it is evident that very limited aspects of IAP have been explored during the past few years and many windows of opportunities exist for IAP work in the future.
Austroeupatorium inulifolium is aggressively invading many land use types in the Knuckles Conservation Area (KCA) in Sri Lanka. The Cymbopogon nardus dominated grasslands, often demarcated by native forests, are the most vulnerable. The present study quantified the soil seed bank and the standing vegetation of these highly invaded grasslands. Forest-grassland edge (FGE) has been identified as the starting point for this invasion, and therefore sampling was carried out twice at different distances from the FGE towards the grassland (0, 10 and 30 m). The soil seed bank showed high seasonality with higher abundance and richness in the wet season than in the dry season. Interestingly, the dry season soil seed bank was dominated by native species (78%) while the wet season seed bank was dominated marginally by exotics (52%), with the highest contribution from Austroeupatorium. The scarcity of tree seedlings was noticed during the study. Austroeupatorium and tree seeds showed decreasing trends from the FGE towards the invasive grassland, and were evident in the seed bank as well as in the standing vegetation. Despite similar trends, the soil seed bank and the standing vegetation of invasive grasslands showed low similarity in terms of richness and abundance due to the dominance of a single species. The results suggest that Austroeupatorium invasion has the potential to alter the existing vegetation in these highly degraded grasslands and influences their succession over time.