Browsing by Author "Fernando, M. T. R."

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Changes in the composition and diversity of standing vegetation and soil seed bank in a lowland wet evergreen forest
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Imbuldeniya, T. D.; Wijetunga, A. S. T. B.; Fernando, M. T. R.
The lowland wet evergreen forests in Sri Lanka hold significant ecological and socio-economic value, making it a crucial ecosystem worthy of conservation efforts. Salgala forest reserve (FR) in the Kegalle district is one of the small, isolated forest reserves and home to many endemic plant species. Like many other forest reserves in the country, Salgala FR is also under anthropogenic and natural threats such as habitat degradation, erosion, and invasive species. In order to take protection measures, it is important to assess the amount and trends in biodiversity on the site. This study was carried out to assess the species diversity and composition of vegetation and soil seed bank (SSB) in the Salgala FR along an elevational gradient. Vegetation and soil sampling were conducted at three different elevations: above 300 m elevation, between 250 m- 300 m and between 250 m and 200 m. The stratified random sampling method was carried out due to the heterogeneity of the terrain and vegetation and seven main sampling plots of 10 m x 10 m were laid to assess the overstory vegetation with the individuals higher than 1.5 m and circumference of tree trunks at breast height is greater or equal to 30 cm. Five subplots of 2 m x 2 m and another two 1 m x 1 m sub-sub plots were laid within each main sampling plot to assess the diversity of understory vegetation in two strata. During this study, 70 soil samples (35 kg) were collected from 7 sampling plots and under greenhouse conditions, soil samples were incubated for SSB analysis. Hutcheson’s t-test was used to analyze diversity variation in standing vegetation and SSB along the elevational clusters in FR with Shannon Weiner index values. The results indicate a decreasing trend in the Shannon diversity index (H`) with increasing elevation for SSB, while the vegetation has shown a different pattern. However, the higher diversity was recorded in mid-elevation for the standing vegetation (H’=3.5390), while the higher elevation for both standing vegetation (H`= 2.7659) and SSB (H`= 1.4809) has recorded the least diversity values. Higher slopes and soil erosion in higher elevations in the sampling sites and several slope-related factors can have an impact on the differences of diversity in vegetation. And, these differences are due to the amount of sunlight received, lack of water, and nutrient depletion brought on by soil erosion. Stemonurus apicalis was identified as the dominant plant species in the standing vegetation. However, Clidemia hirta was the dominant species in the soil seed bank in Salgala FR. Hence, variations in the composition of the existing vegetation in these seven sampling locations may be attributed to disparities in germination prerequisites, competitive forces, anthropogenic disruptions, and soil erosion processes.
Effects of climate change on early life history stages of selected montane forest species in Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Gunawardana, D. D. D. D.; Fernando, M. T. R.
Global climate change has become a significant challenge for ecosystems across the world, as it alters the global temperature, and rainfall patterns and creates extreme weather events. It influences different components such as environmental, ecological, and socio-economic stability. Among the climatic factors, temperature and rainfall play a critical role in determining vegetation distribution and abundance. Montane and alpine forests located at higher altitudes are the most vulnerable terrestrial ecosystems to the current climate change. Surpassing the various life stages of plants, seed germination, and seedling establishment are the phases highly affected by climate change. The main objective of this research was to determine the effect of predicted high temperatures and drought stress on the early life history stages of plants in the montane forests of Sri Lanka. Seeds from Eurya ceylanica and Hortonia floribunda were obtained from the Knuckles Forest whereas Exacum trinervium and Maesa indica were collected from the Loolkandura estate. Then the effect of temperature and water potential were measured by their germination percentages and shoot-root lengths under different temperatures. Seeds collected from Knuckles Forest were incubated at different temperatures, such as 17oC, 25oC, and 30oC on filter papers saturated with water, in Petri dishes. Seeds collected from Loolkandura were subjected to different temperatures (17oC, 25oC, and 30oC) and an osmotic potential gradient (0 MPa, -0.25 MPa, -0.50 MPa, and -0.75 MPa) by dissolving different amounts of polyethylene glycol in distilled water. According to the results, except M. indica other species did not show germination until 30 days, but germinated upon the scarification and gibberellic acid treatment depicting they have seed dormancy. Although E. ceylanica germinated at all 3 temperatures, the highest shoot and root growth were observed at 25oC showing that it can be adapted to the current warmer climate with moderate temperature increments. H. floribunda showed germination only at 25oC with remarkable seedling growth revealing that high temperatures promote its seed germination and seedling establishment. E. trinervium showed poor germination only at 17oC under -0.25MPa. Thus, other high temperatures are unfavorable for its germination. However, further studies are required to determine the precise climate effect on E. trinervium. M. indica had remarkable germination along with higher shoot and root growth at 17oC. Hence, global warming demotes the M. indica seed germination and establishment. However, it had the potential to survive under moderate temperature increments up to 25oC and water deficit conditions up to -0.25 MPa. M. indica seedlings can tolerate extended drought periods within their existing local range. But it is unable to survive in severe osmotic stress at -0.75 MPa and high-temperature conditions like 30oC when its range shifts to other locations. Since M. indica is a pioneer species in Knuckles Forest and has adaptability for climatic warming in local regions, it can be used to promote ecological succession in fragmented areas of montane forests and improve its biodiversity.
Investigating the competitive ability of endemic Osbeckia octandra with its co- occurrence with invasive Sphagneticola trilobata and native weed, Urena lobata
(Faculty of Science, University of Kelaniya, Sri Lanka., 2021) Prabodani, N. L. A.; Fernando, M. T. R.
In Sri Lanka, Osbeckia octandra (L) DC. is a widely used valuable endemic herb in Ayurvedic medicine, popular natural remedy among Sri Lankans and an important pollinator plant. Their local populations are disappearing rapidly due to various anthropogenic activities. Further, local roadside habitats of some O. octandra populations are under the threat of invasion by several exotic and native weedy species. When the competition exerted by those competitively superior invasive and weedy species become severe, O. octandra populations can be threatened for extinction. Thus, the present study was carried out to investigate the competitive ability of O. octandra with its co-occurring exotic invasive Sphagneticola trilobata (L.) and native weedy Urena lobata (L.) species under soil water and nutrient gradients. Pot experiments were conducted with O. octandra monocultures as controls and O. octandra mixed-cultures with either S. trilobata or U. lobata as experimental pots to study the inter-specific competition for soil nutrients under three different nutrient levels (low, moderate and high) and for soil water, under two different water availabilities (well-watered and water-stressed). One set of 12 pots (4 pots of O. octandra/S. trilobata; 1:1 pots+ 4 pots of O. octandra/U. lobata 1:1 pots+ 4 pots of control pots) was prepared for every assigned nutrient and watering condition. After a five-month experimental period, the mean values of final plant heights, fresh weights, above and below ground dry biomasses of O. octandra plants were recorded and obtained data were analyzed by Analysis of Variance (Two- way ANOVA, P < 0.05) and Tukey’s pairwise comparison using the MINITAB 17 statistical software. According to the results, O. octandra plants in monocultures have performed better than the O. octandra from mixed cultures under all the tested different nutrient and water availability conditions, indicating that invasive S. trilobata and weedy U. lobata have significantly higher competitive abilities over endemic O. octandra along with the soil nutrient and water continua (P < 0.05). Having significantly lower root biomass of O. octandra in mixed cultures compared to the monoculture under low nutrient condition (P < 0.05), revealed that O. octandra has a low phenotypic plasticity. Also, our results revealed that non-invasive U. lobata was equally competitive as invasive S. trilobata against O. octandra under different soil nutrient conditions. Moreover, S. trilobata exerted a significantly higher competition than by U. lobata on O. octandra under well-watered condition (P < 0.05), while under water stressed condition U. lobata exerted a significantly higher competition than by S. trilobata (P < 0.05). Our results clearly shown, that the native weedy U. lobata has a potential to become invasive locally as S. trilobata in future, and suppress the growth of native, less competitive flora. Thus, further studies on invasiveness of native weedy species on endemic species will be needed to investigate.