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  • 1
    Electronic Resource
    Electronic Resource
    Interactions between the coccid, Icerya seychellarum (Westw.) and its host tree species on Aldabra Atoll (1980)
    Springer
    Oecologia 46 (1980), S. 180-185 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary (i) In an area of coastal scrub on Aldabra Atoll the growth and phenology of 120 bushes of Scaevola taccada was measured along three transects stretching 200 m inland from the sea, between May 1977 and November 1978. Correlations between bush parameters, the infestation by the coccid Icerya seychellarum and prevailing saline conditions were measured. Considerable death (up to 50% of labelled clusters) of S. taccada occurred in 1977–78. Leaf infestation ranged from 0 to 1.6 mg dry weight of coccids cm-2 total leaf area per cluster. (ii) Coccids fed predominantly on senescing leaves and seasonal differences in leaf infestation were closely associated with changes in leaf phenology. Under experimental conditions coccids could utilize green leaves. (iii) Infestation increased with distance away from the sea whilst the influence of salt, and its effect in increasing leaf succulence, decreased inland. Infestation was strongly negatively correlated with leaf succulence. (iv) Two experiments with S. taccada showed that coccids significantly reduced the growth of leaves and roots and increased the rate of leaf senescence. 0.5 mg cm-2 of coccids reduced leaf production by 39%. (v) In May 1977 the proportion of dead clusters was significantly positively correlated with coccid infestation and in 1978, when mean cluster death doubled, death near the coast (0–100 m) was positively correlated with leaf succulence, whilst inland (101–200 m) death significantly increased with increasing infestation. (vi) It was concluded that coccids could account for the reductions in leaf production in the field and that they contributed to much of the bush death. (vii) The effects of coccids on the leaf production of S. taccada and Euphorbia pyrifolia (Part I) closely agreed. It was estimated that 1.25 mg cm-2 of coccids can completely check leaf production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00540124
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  • 2
    Electronic Resource
    Electronic Resource
    Competition between grassland plants of different initial sizes (1978)
    Springer
    Oecologia 33 (1978), S. 361-380 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Four species of grassland plant, Plantago lanceolata, Holcus lanatus, Lolium perenne and Rumex acetosa, were grown as monocultures and mixtures in pots of nutrient poor soil in a glasshouse for 8 months. There were four plants per pot and these were arranged in two competition modes: either root and shoot interactions were permitted, or only roots allowed to interact by using above-ground partitions. Time of introduction of seedlings was varied to give a range of plant size ratios at the start of the experiment. The factorial design catered for all combinations of species, competition modes and planting times, replicated in four blocks. The shoots were clipped at a fixed height at each of five harvests. Rumex grew badly and was mostly omitted from analysis of the data. By (i) following the change in the relationship of clip dry weights against planting time with successive harvests, (ii) plotting the change in the logarithm of the ratio of cumulative clip dry weights with time and (iii) the use of de Wit logarithmic ratio plots it was demonstrated that each monoculture and mixture combination's ratios of plant weights converged towards stable equilibrium values. Three hypotheses are put forward to explain why in monocultures a smaller plant was at a competitive advantage relative to a larger neighbour and was not suppressed in its growth by the latter. In mixtures this plant size effect was superimposed to different extents on the relative aggressiveness of the species considered. It was concluded that in a nutrient poor soil, when competition for light was low, root interactions can promote the co-existence of neighbouring plant species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348119
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  • 3
    Electronic Resource
    Electronic Resource
    Interactions between the coccid, Icerya seychellarum (Westw.), and its host tree species on Aldabra Atoll (1980)
    Springer
    Oecologia 46 (1980), S. 171-179 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary (i) The growth of ca. 100 individuals of a small deciduous tree Euphorbia pyrifolia, of different ages and edaphic regimes, and with different levels of infestation by the coccid Icerya seychellarum, has been studied on Aldabra Atoll over two years (1976–1978). Infestation on leaves ranged between 0 and 1.3 mg dry weight of coccids cm-2 of total leaf area. (ii) Field observations and an experiment in which coccids were “seeded” on to transplanted trees showed a preference of coccids to feed on senescing leaves rather than on green leaves. Deterrence by green leaves is discussed. (iii) Highest infestations developed on trees which produced the most senescent leaf material early in the wet season. The rate of leaf production on the heaviest infested trees was 36% of that on lightly infested trees. (iv) The level of coccid infestation did not depend on the concentration of soluble nitrogen in senescing leaves but on the total amount of nitrogen exported. The level of soluble nitrogen in green leaves was reduced in heavily infested leaf clusters. (v) Experimental clearance of coccids by insecticide showed that 0.7 mg cm-2 of coccids reduced the rate of leaf growth by 52%. This corresponded closely to the effect of similar levels of coccids in the field. (vi) Leaf infestation was positively correlated with the percentage of dead apices per tree and negatively correlated with the degree of branch extension. (vii) It was concluded that leaf phenology influenced the development of coccid populations and that coccids significantly reduced plant growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00540123
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  • 4
    Electronic Resource
    Electronic Resource
    Host-tree susceptibility to the coccid Icerya seychellarum Westw. (Margarodidae: Homoptera) on Aldabra Atoll: the rôle of leaf morphology, chemistry and phenology (1983)
    Springer
    Oecologia 60 (1983), S. 333-339 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The relative susceptibility of thirty-tree species to feeding by the coccid, Icerya seychellarum, (from a previous atoll survey) were correlated with four morphological characters (leaf lamina and midrib thicknesses, density of hairs on leaf underside and presence of waxy upper leaf surface) and the concentrations of six mineral elements (N, P, K, Ca, Mg and Na) and three measures of chemical defense (total phenols, condensed tannins and alkaloids). For twenty-two species four phenological variables, from a separate two year study, were also correlated with susceptibility. Lamina thickness, presence of dense hairs and the concentrations of alkaloids or condensed tannins were significantly correlated with host susceptibility. The ideal host has thick, evergreen and hairless leaves. Some host species with high concentrations of secondary chemicals were also highly susceptible and a new hypothesis suggests that stylet manoeuvrability enables a coccid to avoid these substances in thick, but not thin, leaves. Experimental ‘seeding’ of crawlers on to eleven host species showed marked differences in susceptibility in different stages of the life-cycle: presence of dense hairs appeared to deter settlement whilst thick lamina enhanced coccid survival.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00376848
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  • 5
    Electronic Resource
    Electronic Resource
    The influence of drainage and soil phosphorus on the vegetation of Douala-Edea Forest Reserve, Cameroun (1986)
    Springer
    Plant ecology 65 (1986), S. 149-162 
    Details
    ISSN: 1573-5052
    Keywords: Africa ; Cameroun ; Douala-Edea ; Drainage ; Gradient ; Phosphorus ; Rain-forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract All living trees (≥30 cm gbh) were enumerated in 104 80×80 m plots arranged along four transects in the Douala-Edea Forest Reserve Cameroun, a system of low-lying ancient coastal sand dunes interspersed by numerous streams and swamps. The extent of permanent and seasonal swamps was recorded for each plot. Two hundred thirty taxa were recognized of which 63% were identified to species. Mean tree density was 376 ha−1, basal area 31.0 m2 ha−1 and number of species per plot 39. The Olacaceae were the most abundant family in terms of basal area, but the Euphorbiaceae the most frequently represented. The most abundant species wasCoula edulis (Olacaceae). Twenty-two plots had most of their area permanently or seasonally swamped. Percentage sand, silt and clay ranged between 32–100, 0–64, 0–21% respectively. The ranges for other variables recorded were: pH (2.7–5.4), organic carbon (1.5–12.4%), available phosphorus (7–90 ppm) and potassium (28–188 ppm), and nitrogen (ammonium 4–40 ppm, nitrate 1–12 ppm). Classification of the plots on the basis of six soil variables provided three large distinct groups: swamp plots and non-swamp plots, the latter divided into plots of low and high available soil phosphorus. Swamp plots were distinguished by high abundances ofProtomegabaria stapfiana andLibrevillea klainei, though correspondence ordination of plots in these groups showedP. stapfiana associated with more clayey soils andLibrevillea klainei (andGluema ivorensis) on the very sandy soils. Direct gradient analysis highlighted several species associated with these lower phosphorus soils. Available soil phosphorus is not as low at Douala-Edea as in parts of Korup, and the association of these Douala-Edea soils with the Caesalpinioideae is correspondingly weaker.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00044815
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  • 6
    Electronic Resource
    Electronic Resource
    Floristic variation within kerangas (heath) forest: re-evaluation of data from Sarawak and Brunei (1991)
    Springer
    Plant ecology 96 (1991), S. 43-86 
    Details
    ISSN: 1573-5052
    Keywords: Ordination ; Tropical ; Sampling ; Soils ; Gradient ; Rain forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The variation in species composition of trees ≥7.6 cm gbh in thirty-eight plots (mostly c. 0.2 ha in extent) from physiognomically-defined kerangas forest were re-analyzed by principal components analysis ordination (species centering and standardization by sample norm). Analyses were performed separately on basal area abundances, on the densities of trees in three size classes (≥7.6, ≥30.5 and ≥61.0 cm gbh) and on the density of small and large trees (7.6-〈30.5 and 30.5-〈61.0 cm gbh). A total of 636 taxa were reduced to 381 for analysis, removing those of very low density and plot frequency. Three groups of plots were identified: forest at low elevation, and generally coastal, on deep humus podzols; forest at intermediate elevation on mostly red-yellow podzols with affinities to dipterocarp forest; and forest at high elevation on mostly peaty podzols. The first group was divisible into five subgroups along a drainage gradient, while the more poorly drained plots showing affinities to peatswamp forest. Forty to eighty of the taxa, depending on the criteria for selection, were sufficient to define a stable, reduced spatial structure of the data matrix. Two subgroups, both coastal on deep podzols, represent the extreme form of kerangas forest per se. A comparison of Agathis borneensis- and Shorea albida-dominated plots revealed few other associated and differentiating taxa. Patterns were clearest from analyses of basal area data and of densities of all and small trees. Ordinations and grouping of plots for small, but not large, tree densities were similar to those for basal area. Different species were differentiated on the basis of the abundance measure, leading to group (tabular) definition of associations in a dual manner. A new system of summarization is presented which combines basal area, density and frequency in a graded hierarchical approach. The association between vegetation and soil type was difficult to unravel because of the limited environmental space sampled. Soil type was confounded with elevation, rainfall and geographical location. A major factor is clay content probably affecting nutrient status and water holding properties. ‘Modal analysis’ of small tree densities showed clearest patterns in this respect. There were no patterns at the family or genus level, nor in leaf size spectra within kerangas. Problems in the treatment, analysis and summarization of tropical forest data sets are discussed. These problems centre on the scale and intensity of field sampling and the advantages of measuring small trees leading to a dual basal area and density approach. All published studies, including this one, within kerangas forest have used inadequate sampling for the purposes of revealing species changes with respect to soil type and composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00031653
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  • 7
    Electronic Resource
    Electronic Resource
    Primary lowland dipterocarp forest at Danum Valley, Sabah, Malaysia. Species composition and patterns in the understorey (1996)
    Springer
    Plant ecology 122 (1996), S. 193-220 
    Details
    ISSN: 1573-5052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The spatial distributions of species of tree ≥10 cm gbh were examined in two 4 ha plots and related to the local variation in topography and soil chemistry. The plots were similar in their species composition, particularly in terms of the densities of small trees, and they showed very similar edaphic characteristics. Size class distributions varied little within and between plots. Ordination of 0.25 ha subplots highlighted parallel gradients in the vegetation of both plots when the densities of trees ≥10 cm gbh were considered. Focusing on understorey trees in the 10-〈50 cm gbh class at the 0.04 ha subplot scale showed a similar vegetation gradient in both plots closely associated with change from lower slope to ridge. No relationship with soil chemistry was found. On the ridges a special group of understorey species formed clumps and these species contributed importantly to the ordinations. Borneo has a regional history of occasionally severe droughts. It is suggested here that the observed patterns in the understorey are due to differential responses to low soil water supply, the ridges probably tending to dryness more than the lower slopes. Within the large and diverse family Euphorbiaceae, which dominates the understorey at Danum, there may be ecophysiological groupings of species. The long-term effects of disturbance interacting with local edaphic factors on forest structure and composition are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00044700
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  • 8
    Electronic Resource
    Electronic Resource
    Spatial pattern of trees in kerangas forest, Sarawak (1986)
    Springer
    Plant ecology 65 (1986), S. 77-89 
    Details
    ISSN: 1573-5052
    Keywords: Kerangas forest ; Pattern ; Regeneration ; Sarawak ; Spectral analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 64 most abundant species (≥10 cm dbh) in a 400×480 m plot of predominantly kerangas forest in Sarawak were individually investigated for two-dimensional pattern by spectral analysis using the basal areas of trees in 20×20 m contiguous quadrats. All species had individuals in the upper canopy. 30 species showed pattern with clumps. The most frequent scales of clump size were between 35 and 55 m across. Patterned species were less abundant in the plot, had a greater proportion of smaller (10–20 cm dbh) trees and had a lower ratio of upper to lower canopy trees than species without pattern. Trend across the plot between dipterocarp and kerangas forest types matched the change in soil from red-yellow podzol (oxisol and ultisol) to medium gleyic and bleached sand podzols (spodosol). However, soil differences and small scale (ca. 50 m) changes in topography did not account for patterns. The scale of pattern matches the size of gaps produced by windthrow. It is suggested that patterned species are light-demanding and grow from seeds in gaps, whereas non-patterned species are shade tolerant, growing within closed forest to sapling size and eventually maturing by filling smaller single tree gaps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00044877
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  • 9
    Electronic Resource
    Electronic Resource
    The influence of topography and soil phosphorus on the vegetation of Korup Forest Reserve, Cameroun (1986)
    Springer
    Plant ecology 65 (1986), S. 131-148 
    Details
    ISSN: 1573-5052
    Keywords: Africa ; Cameroun ; Gradient ; Korup ; Phosphorus ; Rain-forest ; Topography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract All living trees (≥30 cm gbh) were enumerated in 135 80×80 m plots, each subdivided into four 40×40 m subplots, and arranged along four 5 km transect lines in the Korup Forest Reserve, Cameroun. For each plot altitude, slope and the extent of permanent and seasonal swamps were recorded. Four hundred and eleven taxa were recognized of which 66% were identified to species. Mean tree density was 471 ha−1, basal area 27.6 m2 ha−1 and number of species per plot 75. The subfamily Caesalpinioideae (Leguminosae) was the most abundant family/subfamily in terms of basal area, but the Scytopetalaceae the most frequently represented, mainly on account ofOubanguia alata. Ten plots had at least three quarters of their area permanently swamped, and three, to a similar extent, were seasonally swamped. The ranges in sand, silt and clay content were 60–91, 0–24 and 4–20% respectively. The pH value, organic carbon content and nitrate-nitrogen concentration ranged between 4.0–5.8, 1.3–5.7% and 0–35 ppm respectively. The largest soil variations were in available phosphorus, range 2–29 ppm, and potassium, 38–375 ppm. Correspondence analysis ordination of all plots showed a major indirect floristic gradient correlated with increasing altitude, slope and soil phosphorus and potassium. Removal of the topographic effect by separate re-ordinations of four groups of plots at low, middle (2) and high altitude/slopes highlighted a strong correlation of the main floristic gradients of the middle altitude/slope groups with the concentration of available soil phosphorus. Direct gradient analysis using all plots with respect to available soil phosphorus concentration confirmed the indirect analyses. Individual species response to phosphorus were also shown by direct comparisons in the vegetation on plots of high and low available soil phosphorus concentration. Low available phosphorus soils (≤5 ppm) are strongly associated with species of the subfamily Caesalpinioideae, especially of the tribes Amherstieae and Detarieae. It is suggested that this result is probably due to the ability of these particular legume tribes to form associations with ectotrophic mycorrhizae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00044814
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