16 research outputs found

    SEEDLING SURVIVAL AND GROWTH OF Mesua AND Dipterocarpus SPECIES IN A SRI LANKAN RAIN FOREST

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    Seedlings of Dipterocarpus (D. hispidus and D. ievlanicusi and Mesua 1M. [errea and M.nagassarium, were investigated for their survival and growth 111 differentmicroenvironments in a lowland rain forest in south-west of Sri Lanka. These species occurtogether as canopy dominants of late-successional rain forest. Partitioning of theregeneration niche can be one explanation for the co-existence of ecologically similarcanopy tree species within a forest. This study tested that differences in disturbances acrossthe topography of lowland rain forest cause different survival and growth rates 111 closelyrelated tree species among and within canopy openings of different size.Seedlings were planted in plots located in five zones representing a range of forestgroundstorey micro-environments found adjacent to and across canopy openings of threesites- valley, midslope and ridgetop. Plots were located from north to south across each gap(i) undcrstorey 10m to the south of the gap, (ii) southern gap edge, (iii ) centre, (iv) northernedge and (v) understorey 10m to the north of the gap. Experiments were designed tomonitor survival and growth of planted seedlings for two years. At the end of two yearssurvival was calculated, height increment recorded and destructive samples were taken tomeasure dry mass gain of root, stem and leaves.Seedlings of Mesua [errea, M. nagassarium and D. zevlanicus showed high survival on allsites and in all gap/ canopy conditions. D. hispidus showed the lowest survival in all sites.Growth measures attained maxima in the centre gap/ canopy condition in the three sites forall species. Results also demonstrated clear differences among species. Dipterocarpusexhihited greater growth responsiveness than Mesne species. These differences appeared tohe related to availability of soil moisture and groundstorey radiation regimes. This studydemonstrated that closely related species have specific growth characteristics that alloweach to establish and grow hetter than its relatives in particular forest microenvironments.

    GROWTH AND SURVIVAL OF PIONEER AND LATE SUCCESSIONAL SPECIES IN SIMULATED LIGHT ENVIRONMENTS IN A SRI LANKAN LOWLAND RAIN FOREST

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    Growth and survival of two pioneer and four late successional species in different light levels inshade houses were investigated over a period of one year from January 2000 to January 200 1 atthe Sinharaja field research station.Schumacheria castaneifo/ia (Dilleniaceae) and Vltex altissima (Verbenaceae) represented thepioneer species. Psychotria nigra, Gaertnera vaginans (Rubiaceae), Syzygium operculatum andS. rubicundum and (Myrtaceae) were selected as late successional species. The four latesuccessional species were further subdivided into two canopy species (S. operculatum and S.rubicundum) and two understorey species (Psychotria nigra and Gaertnera vaginans) based onheight at maturity oftheir parent trees. Seedlings were grown under four light environments (fullsun, 1200; partial sun, 800; partial shade, 350; shade, 50j.Lmolm-2s-1) that represented a range ofPPFD (photosynthetic photon flux density) found within the forest. Five seedlings of eachspecies were grown in each light environment, which was replicated three times. At the end ofone year the height increments and percentage survival of seedlings were measured.The study revealed that two Syzygium species, Gaertnera vaginans and S. castaneifolia showingthe lowest height increments 'when grown in shade. But no significant difference was observedbetween shade and full sun for these species. Although the lowest height increments for Valtissima and P. nigra were observed in full sun and in partial shade respectively, there is nosignificant difference among shade, partial sun and full sun for V altissima. Psychotria nigra didnot show any significant difference among four light treatments. The greatest relative heightgrowth was observed in partial shade for G. vag/nans and S. castaneifoliz; V altissima, and inpartial sun for two Syzygium species. Plasticity (ratio between highest and lowest values amonglight treatments) measurement of height increment was highest in G. vaginans (3.47), the lowestin P. nigra (l.52) compared to s. operculatum (1.79), S rubicundum (2.18), V altissima (2.19),S. castaneifolia (3.08). Percentage seedling survival of S. castaneifolia, and V a/tissima was100% under all light levels .All species survived equally well in partial sun light level. In shade,seedling survival of G. vaginans, and S operculatum was 93% and in Psychotria nigra, it was80%. G. vaginans and P. nigra showed 93% seedling survival in partial shade .In full sun G.vaginans and S. rubicundum exhibited 93.3% survival while P nigra showed 67 % survival.These results suggest that pioneer species grow and survive well in all light levels than latesuccessional species in early stage of their life cycle.

    EFFECT OF CANOPY GAPS A'ND TOPOGRAPHIC REGIMES IN SEEDLINGS PERFORMANCE IN SINHARAJA RAIN FOREST, SOUTHWEST SFU LANKA

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    Growth and survival of tree canopy dominant seedlings in the Sinharaja lowland rain forest insouthwest Sri Lanka were monitored. Twelve canopy gaps and closed canopy sites wereselected, as four of each on different topographic positions- valley, midslope and ridgetop.Measurements of height, number of leaves and mortality were recorded over a two-year period.Hemispherical canopy photographs were taken to calculate Indirect Site Factor (ISF), Direct SiteFactor (DSF), and canopy openness. Greatest canopy openness, highest DSF values wererecorded for ridgetop sites and smallest values were recorded for valley sites. Over the two-yearperiod sixty-six (11.45%) seedlings died in the ridge top, which indicated the highest mortalityrate. Survival of seedlings in the canopy gap ani .orest understorey declined on progressingfrom valley to ridgetop sites. Seedlings of Mesua ferrea had a higher survival than other speciesin the canopy opening and understorey conditions. Height growth and leaf number were greatestin the gap sites. A significant relationship was found between DSF and maximum height growth(33.05,P>O.OO) for Syzygium rubicundum. Shorea trapezlfolta, Shorea distich a and Syzygiumrubicundum showed greatest height increment .n the valley, midslope and ridgetop sitesrespectively. No relationship was found between DSF and leaf numbers in all seedlings exceptSyzygium rubicundum, where has increased with increasing DSF

    ECOPHYSIOLOGY OF TWO LIANA SPECIES Calamus ovoideus AND Coscinium fenestratum UNDER DIFFERENT CANOPY REMOVAL TREATMENTS

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    Calamus ovoideus Thw. and Coscinium fenestratum Colbr. are naturally growing economicallyimportant liana species, around the Sinharaja MAB reserve, Sri Lanka. Growth performance andphysiological attributes of these species were examined using plants established in 1991 underthree different canopy removal treatments ina Pinus caribaea plantation in the buffer zone ofSinharaja forest. They were 3 pine rows and 1 pi lie row removed, 3 pine rows under plantingand the Pinus underplanting control where the initial light intensities were 22, 10, 5 and 3mol/m21 day respectively.The results showed that height after 8 years and the annual height increments were significantlyhigher among the three canopy removal treatments compared to that in the closed canopy controlfor both species. In C. ovoideus greatest height was in the three-pine rows removal treatment andleast in the closed canopy under planting . .In contrast, Cifenestratum showed no significantheight difference among the three canopy removal treatments compared to the control. The meanroot collar diameter after 8 years and its increments in C. fenestratum were significantly higherin the canopy removal treatments compared to that of the control. In the physiological studies,both species showed significant differences in their net photosynthetic rate and stomatalconductance when grown under different light regimes. The higher photosynthetic rate of C.ovoideus was in the one pine removed treatment ar.d in C. fenestratum it was in the three pinerows removed treatment.After 8 years of establishment, for both study species the three and one pine rows removed andthree pine rows underplanting treatment were better than the Pinus underplanting (closedunderstorey) treatment. This study revealed that these liana species could be successfullyintroduced to the monocuIture Pinus caribaea plantations in the lowland wet zone of Sri Lanka.

    In situ variation in leaf anatomy and morphology of Andira legalis (Leguminosae) in two neighbouring but contrasting light environments in a Brazilian sandy coastal plain

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    Andira legalis (Vell.) Toledo is a legume shrub widespread along the sandy plains of the Brazilian coast. It occurs both shaded, in forest habitats, or exposed to full sunlight, in the vegetation islands growing on sand deposits. Previous studies reported a high range of morpho-physiological variation for this species along a geographical gradient. This study compared leaf morphology and anatomy of A. legalis in two distinct but adjacent light environments: a dense forest (shaded) and a scrub of Palmae (exposed). We studied the amplitude of variation for these traits within a small (0.5 ha) geographical area. Leaf anatomy parameters were measured for five leaves collected from five plants in each habitat. The parameters measured were leaf and mesophyll thickness, thickness of the outer periclinal cell wall, thickness of the adaxial and abaxial epidermis and vascular bundle transversal section area, and also common epidermal cells, stomata and trichome density. Leaf morphology parameters were obtained from five leaves of each of 20 plants in each site. Dry and fresh weights were measured to obtain leaf specific mass and succulence. All anatomy and morphology parameters, except trichome density, were significantly higher for the sun-exposed plants. Less expected, however, was the marked qualitative difference between exposed and shaded plants: in the former the mesophyll had a unilateral symmetry (i.e., the whole mesophyll occupied by photosynthetic tissue), whereas in the latter there was a dorsiventral symmetry (i.e., partly palisade and partly spongy parenchyma). Such amplitude of variation shows that even within a small geographic area A. legalis has a broad ecological plasticity
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