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Title: Environmental effects on the growth of broadleaved trees introduced under pine stands in Sri Lanka
Author: Weerawardane, N. D. R.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1996
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Results indicated that Alstonia growth was very satisfactory under pine overstorey where row thinning of pine trees had been done with considerable canopy opening. Mulch treatments significantly improved the height and diameter growth by 20% and 28% respectively while trenching and mycorrhiza application showed no response at this site. Total dry matter accumulation, Relative Growth Rate (RGR) and Net Assimilation Rate (NAR) were also significantly improved by mulch treatments. Khaya plants were grown under a row thinned pine stand which was a comparatively dry site and mulching improved growth rates of seedlings by 47% and 20% for height and diameter respectively. These growth increases were almost doubled when mulching was combined with trenching. Dry matter production, RGR and NAR were also improved with these treatments and root:shoot ratio was reduced. Mycorrhizal inoculation showed improvements of RGR, NAR and reduction in Leaf Area Ratio (LAR) of these plants. Cedrela which was grown under a uniformly thinned stand in a much wetter site did not perform well, and failed to show significant height and diameter growth improvements to any of the treatments. However, mulch treatments favoured its leaf growth compared to the control, showing higher leaf and Leaf Weight Ratios (LWR). Swietenia showed about 61% increase to the combined treatment of mulch, trench and mycorrhiza in terms of height growth during the shorter period of this experiment. Survival was very high in all species except Cedrela. Mulched conditions generally favoured the growth of all species particularly in the less wet sites. Observations suggested that it also improved soil micro-climate in terms of moisture, nutrients and aeration of topsoil. Different uniform thinning levels at higher elevations of pine from 30 to 10 m2basal area increased direct light level from 18% to 58%, and indirect light levels also followed the same pattern with slightly lower values as measured by hemispherical photographs. Alstonia, Cedrela, Swietenia and Michelia all responded positively to increasing light levels with growth being less in all species under 30 and 20 m2 basal area. Swietenia and Alstonia tended to show much reduced growth with light levels below 50% full sun. Under mid elevations Alstonia indicated sufficient light conditions around 59% full sun with row thinning while Swietenia indicated about 53% or low light would be suitable for its height growth at mid elevations. Khaya, on the other hand, indicated light levels above 50% are beneficial for its growth although it can tolerate low light conditions.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available