Natural Colonization Research Articles

Arbuscular mycorrhiza status of gold and uranium tailings and surrounding soils of South Africa's deep level gold mines. II. Infectivity

An AMF infectivity study and spore viability assessment was performed on substrata obtained from gold and uranium mine tailings dumps (‘slimes dams’) in the North West and Free State provinces of South Africa. Three slimes dams in each region were categorized as recently vegetated (RV), old vegetated (OV) and never vegetated (NV), and dams then divided into five zones based on elevation above ground level, steepness and broad chemical differences. Rhizosphere samples were collected from two of three plant species common to all sites; Eragrostis curvula, Atriplex semibaccata and Cynodon dactylon, as well as from bare areas, in order to allow comparisons across all site categories because of the rarity of the grasses on the lower slope of NV dams. Infectivity was determined by the mean infection percentage method from a bioassay of the substrata using Eragrostis curvula cv Ermelo as a host plant. There was no difference in total infectivity between North West and Free State substrata, but within regions, there were differences in infectivity between rehabilitation ages, between zones, and between rhizosphere and bare areas. Toepaddock substrata and veld soil produced the highest total infection levels overall. On both dams and veld, total arbuscular levels differed between rhizosphere and bare substrata, and the percentage of arbuscules (max. 15.4%) and vesicles (max. 22.0%) as a proportion of total infection structures was low. A low correlation between infectivity and total spore numbers was also found. Spore numbers and the numbers of viable spores increased with zone down the slimes dams to the veld, and also differed within zones between rhizosphere and bare substrata with marked interactive effects. Substratum organic matter (SOM) levels differed between regions, and between zones within the North West region increasing with distance down the slopes to the veld, and were strongly correlated with total spore numbers. Substratum pH values and most AMF parameters were positively correlated in the order of RV>OV>NV dams, indicating that natural colonization of acidic NV sites by AMF is at very low rates, and that AMF colonizing RV slopes are not surviving the transition from RV to OV, with the associated increase in acidity, conductivity and decline in plant cover. Substratum conductivity differed between zones in both regions, with minor interaction between region and zone, and was negatively correlated with pH, AMF infectivity and total spore numbers. Our findings demonstrate that the ameliorant effects of liming and irrigation on substratum pH and conductivity are short-lived, but despite the physico-chemical constraints, a significant measurable AMF inoculum potential does exist on all substrata. Amelioration of tailings with organic matter and use of acid and salt-tolerant AMF would be expected to contribute to more persistent AMF communities and vegetation on gold and uranium slimes dams.

Colonization and predation of thrips (Thysanoptera: Thripidae) by Orius spp. (Heteroptera: Anthocoridae) in sweet pepper greenhouses in Northwest Italy

Frankliniella occidentalis (Pergande) and Thrips tabaci Lindeman (Thysanoptera: Thripidae) are major pests of sweet pepper for direct damage and tospovirus transmission. To control their infestations, Orius laevigatus (Fieber) (Heteroptera: Anthocoridae) is produced by many commercial insectaries and widely used on IPM vegetable crops of Europe. This predator is naturally widespread along the Mediterranean and Atlantic coasts, and not in more continental areas, where other Orius spp. are more common. Research was conducted in a continental area of Northwest Italy in 2002–2003 to assess the natural presence of anthocorids on pepper, and to compare their colonization and predatory ability with those of the species artificially introduced. Experiments were conducted in 12 sweet pepper greenhouses, in six of which O. laevigatus release was made. From late May to early October, thrips and anthocorids were sampled on pepper by collecting flowers; Orius spp. were also collected on neighboring wild flora. Independently of the releases, Orius specimens were found in all surveyed greenhouses, but O. niger Wolff, also captured on various wild plants, was the most abundant species. It naturally colonized crops from late June and proved to be the most efficient predator on sweet pepper in the surveyed area, if not disturbed by pesticide application. Contrarily, O. laevigatus was rarely found and only in the greenhouses in which it had been released. However its introduction resulted in thrips control before natural colonization by the native species occurred.

Impact‐induced impoverishment and transformation of a sandstone habitat for lithophytic microorganisms

Abstract— Sandstones are a common habitat for lithophytic microorganisms, including cryptoendoliths. We describe laboratory experiments on the colonization of impact metamorphosed sandstones from the Haughton impact structure, Canadian High Arctic. Colonization experiments with the coccoid cyanobacterium, Chroococcidiopsis sp. and the motile gram‐positive bacterium Bacillus subtilis, show that, in contrast to initially low porosity crystalline target rocks, which can become more porous as a result of impact bulking, by closing pore spaces the sedimentary cryptoendolithic habitat can be impoverished by impact. However, the heterogeneous distribution of collapsed pores, melt phases, and subsequent recrystallization, results in heterogeneous colonization patterns. Cavities and vesicles formed during melting can yield new habitats for both cryptoendoliths and chasmoendoliths, manifested in the natural cryptoendolithic colonization of shocked sandstones. By contrast, post‐impact thermal annealing and recrystallization of impact melt phases destroys the cavities and vesicles. In extreme cases, complete recrystallization of the rock fabric makes the material suitable only for epilithic, and potentially hypolithic, colonists. These experiments further our understanding of the influence of the target lithology on the effects of asteroid and comet impacts on habitats for lithophytic microorganisms.

Core Rot Development in Red Delicious Apples Is Affected by Susceptibility of the Seed Locule to Alternaria alternata Colonization

ABSTRACT Alternaria alternata is the causal organism of core rot decay symptoms in susceptible cv. Red Delicious but not in resistant cv. Golden Delicious. The two cultivars did not differ in natural colonization of the style and ovary during the first week after full bloom; colonization of the ovary in the susceptible cultivar subsequently decreased with increasing distance from the calycine tube. By 30 days after full bloom, Alternaria recovery from ovary 1, adjacent to the end of the calycine tube, was 100 and 40% in the susceptible and resistant cultivars, respectively. In the susceptible cultivar, Alternaria recovery decreased from 75 to 20% in ovaries 2, 3, and 4, while there was only minor incidence in the resistant cultivar. Inoculation of the mesoderms of the two cultivars induced similar decay symptoms, but inoculated locules of Red Delicious were more susceptible than those of Golden Delicious. Increased inoculum concentration or isolate virulence enhanced the difference in locule susceptibility between the cultivars. Inoculation on isolated seed locules or on media amended with susceptible locule tissue as a carbon source induced greater transcript levels of several genes than the inoculation on resistant tissue. Endo- and exoglucanase activity levels were higher at pH 4.8 than at 4.2, conditions typical of the mesoderm adjacent to the seed locules of the susceptible and resistant cultivars, respectively. Current results suggest that susceptibility of Red Delicious apples to core rot decay is dependent on the sensitivity to locule colonization and on mesoderm pH, a factor that enhances fungal virulence.

Identification and analysis of differentially expressed Heterobasidion parviporum genes during natural colonization of Norway spruce stems

To identify differentially expressed genes of the white-rot fungus Heterobasidion parviporum, two cDNA libraries were constructed using suppressive subtraction hybridization (SSH) technique with RNA extracted from an advanced stage of decay area and from colonization front next to the reaction zone of the stem of a mature Norway spruce naturally colonized by the fungus. Besides several cytochrome P450s and hypothetical proteins with unknown function, the SSH libraries constructed contained, among others, genes involved in basic cellular processes, and lignin and cellulose degradation. To examine the role of selected candidate genes for each functional group, three trees, each colonized by a different genotype of the pathogen and showing a variable degree of wood decay, were used for real-time RT-PCR profiling of candidate genes. In the decay transition areas the study revealed activity centers that showed remarkable similarity in the transcript profiles of the monitored genes.

Genetic analysis of potential postglacial watershed crossings in Central Europe by the bullhead (Cottus gobioL.)

Natural colonizations across watersheds have been frequently proposed to explain the present distributions of many freshwater fish species. However, detailed studies of such potential watershed crossings are still missing. Here, we investigated potential postglacial watershed crossings of the widely distributed European bullhead (Cottus gobio L.) in two different areas along the Rhine-Rhône watershed using detailed genetic analysis. The main advantage of studying bullheads vs. other freshwater fish species is that their distribution has been lightly influenced by human activities and as such, interpretations of colonization history are not confounded by artificial transplantations. The genetic analyses of eight microsatellite loci revealed strong genetic similarities between populations of both sides of the Rhine-Rhône watershed in the Lake Geneva area, giving strong evidence for a natural watershed crossing of bullheads from the upper Rhine drainage into the Rhône drainage in the Lake Geneva area likely facilitated by the retreat of the glaciers after the last glacial maximum some 20,000 years ago. Populations from the Lake Geneva basin were genetically more similar to populations from across the watershed in the upper Rhine drainage than to populations further downstream in the lower Rhône. In contrast, populations from Belfort, an area, which was not covered by ice during the last glacial maximum, showed strong genetic differentiation between populations of the upper Rhine and Rhône drainages. Based on our results on the bullhead, we propose that glacial retreat may have eased the dispersal of numerous European freshwater fish species across several geological boundaries.

Resistance of Apple Cultivars to <I>Dysaphis plantaginea</I> (Hemiptera: Aphididae): Role of Tree Phenology in Infestation Avoidance

To test the importance of flowering phenology in damage caused to apple cultivars by rosy apple aphid, Dysaphis plantaginea (Passerini) (Hemiptera: Aphididae), susceptibility of 16 cultivars was compared in greenhouse conditions after infestation with aptera and in the field after natural tree colonization. Flowering phenology was recorded in the field for all the cultivars. In both greenhouse and field trials, there were differences among cultivars with respect to aphid infestation and damage. However, damage in the greenhouse and field was not significantly correlated. Flowering phenology was also different among cultivars. Flowering order among cultivars was significantly negatively correlated with aphid infestation and damage in field, i.e., early leafing cultivars showed higher infestation and damage than late-leafing cultivars. If egg hatching occurs before bud bursting, neonate larvae will suffer a high mortality because they cannot feed on these late cultivars. A later recolonization of these trees is hampered because (1) winged aphids cannot live on apple but only on the secondary host, (2) apterous forms have a limited dispersal capability, and (3) aphid predators progressively increase in the orchard. Therefore, synchronization between egg hatching and bud bursting is of critical importance in the success or failure of infestation.

How to Use Genetic Data to Distinguish Between Natural and Human-Mediated Introduction of Littorina littorea to North America

The rapid range southward expansion of the periwinkle Littorina littorea from the Canadian maritimes has fueled a long-running debate over whether this species was introduced to North America by human activity. A reappraisal of the mitochondrial DNA sequence evidence finds considerable endemic allelic diversity in the American population. The degree of endemic genetic diversity is higher than expected from human-mediated colonization, but not so much to suggest that it survived the last glacial maximum in America. Coalescent estimates of population divergence agree that colonization of America preceded European contact. A reappraisal of the ITS nuclear sequence data finds extensive recombination. Taking this recombination into account strengthens the genetic case against human-mediated introduction. Finally, a reappraisal of conflicting allozyme studies from the 1970’s supports a claim of limited divergence between American and European populations. This is consistent with post-glacial colonization, but the allozyme data cannot distinguish between natural or human-mediated colonization. Taken as a whole, the DNA sequence data supports the many sub-fossil reports of an American L. littorea population in the Canadian maritimes that preceded even the first visits by the Vikings.

Non-anthropogenic dynamic factors and regeneration of (hemi)boreal urban woodlands – synthesising urban and rural ecological knowledge

The natural dynamics of urban woodlands are seldom discussed despite the general acknowledgement that understanding of natural processes is a prerequisite for successful management of ecosystems. This paper reviews the non-anthropogenic dynamic factors, and anthropogenic changes in them, in urban woodlands. Several gaps in the knowledge are identified: (1) amount of tree regeneration and factors affecting it, (2) seedbed availability for poor competitors, (3) wind as a dynamic factor, (4) insect outbreak severity, (5) effect of urban climate on tree regeneration, (6) pollination and dispersal and (7) effect of herbivory on tree regeneration. It is concluded that natural dynamics drive regeneration in urban woodlands, but the disturbance regime and successional pathways may be altered. Natural colonisation of derelict land and natural dynamics in existing woodlands are beneficial because of decreased management costs, and the biodiversity, educational, recreational and psychological values they provide.

Restoration of mangrove plantations and colonisation by native species in Leizhou bay, South China

AbstractTo examine the natural colonisation of native mangrove species into remediated exotic mangrove stands in Leizhou Bay, South China, we compared soil physical–chemical properties, community structure and recruitments of barren mangrove areas, native mangrove species plantations, and exotic mangrove species—Sonneratia apetala Buch.Ham—between plantations and natural forest. We found that severely degraded mangrove stands could not regenerate naturally without human intervention due to severely altered local environments, whereas some native species had been recruited into the 4–10 year S. apetala plantations. In the first 10 years, the exotic species S. apetala grew better than native species such as Rhizophora stylosa Griff and Kandelia candel (Linn.) Druce. The mangrove plantation gradually affected soil physical and chemical properties during its recovery. The exotic S. apetala was more competitive than native species and its plantation was able to restore soil organic matter in about 14 years. Thus, S. apetala can be considered as a pioneer species to improve degraded habitats to facilitate recolonisation by native mangrove species. However, removal to control proliferation may be needed at late stages to facilitate growth of native species. To ensure sustainability of mangroves in South China, the existing mangrove wetlands must be managed as an ecosystem, with long‐term scientific monitoring program in place.

Natural occurrence of Azospirillum brasilense in strawberry plants

Azospirillum species are free-living nitrogen-fixing bacteria commonly found in soil and in association with roots of different plant species. For their capacity to stimulate growth they are known as plant growth-promoting bacteria (PGPB). In this work, we demonstrate the natural occurrence and colonization of different parts of strawberry plants by Azospirillum brasilense in the cropping area of Tucuman, Argentina. Although bacteria isolations were carried out from two strawberry cultivars, e.g., Camarosa and Pajaro, attempts were successful only with the cultivar Camarosa. Whereas different strains of Azospirillum were isolated from the root surface and inner tissues of roots and stolons of the cultivar Camarosa, we have not obtained Azospirillum isolates from the cultivar Pajaro. After microbiological and molecular characterization (ARDRA) we determined that the isolates belonged to the species A. brasilense. All isolates showed to have the capacity to fix nitrogen, to produce siderophores and indoles. Local isolates exhibited different yields of indoles production when growing in N-free NFb semisolid media supplemented or not with tryptophan (0.1 mg ml−1). This is the first report on the natural occurrence of A. brasilense in strawberry plants, especially colonizing inner tissues of stolons, as well as roots. The local isolates showed three important characteristics within the PGPB group: N2-fixation, siderophores, and indoles production.

Stoats (Mustela erminea) provide evidence of natural overland colonization of Ireland

The current Irish biota has controversial origins. Ireland was largely covered by ice at the Last Glacial Maximum (LGM) and may not have had land connections to continental Europe and Britain thereafter. Given the potential difficulty for terrestrial species to colonize Ireland except by human introduction, we investigated the stoat (Mustela erminea) as a possible cold-tolerant model species for natural colonization of Ireland at the LGM itself. The stoat currently lives in Ireland and Britain and across much of the Holarctic region including the high Arctic. We studied mitochondrial DNA variation (1771 bp) over the whole geographical range of the stoat (186 individuals and 142 localities), but with particular emphasis on the British Isles and continental Europe. Irish stoats showed considerably greater nucleotide and haplotype diversity than those in Britain. Bayesian dating is consistent with an LGM colonization of Ireland and suggests that Britain was colonized later. This later colonization probably reflects a replacement event, which can explain why Irish and British stoats belong to different mitochondrial lineages as well as different morphologically defined subspecies. The molecular data strongly indicate that stoats colonized Ireland naturally and that their genetic variability reflects accumulation of mutations during a population expansion on the island.

Schoenoplectus corymbosus: a tropical Old‐World sedge (Cyperaceae) discovered in Spain and Morocco

Schoenoplectus corymbosus is a sedge from tropical wetlands widely distributed in Pakistan, India and Africa. Recent collections confirm its presence in wetlands of southern Spain and Morocco. We consider the presence of this plant in the western extreme of the Mediterranean as a consequence of recent colonization, because it was not collected here until 1999, in spite of its medium–large size. Additionally, it grows in much visited areas like nature reserves (such as Doñana National Park). The populations from Spain and Morocco are characterized here, a description of S. corymbosus and a key for Schoenoplectus from Europe and north Africa is supplied. Finally, the possible natural and recent colonization processes of these new populations are discussed.

Genotypic selection in Daphnia populations consisting of inbred sibships

The genetic basis of fitness reduction associated with inbreeding is still poorly understood. Here we use associations between allozyme genotypes and fitness to investigate the genetic basis of inbreeding depression in experimental outdoor populations of the water flea, Daphnia magna. In Daphnia, a phase of clonal reproduction follows hatching from sexually produced resting eggs, and changes in genotype frequencies during the clonal phase can be used to estimate fitness. Our experiment resembles natural colonization of ponds in that single clones colonize an empty pool, expand asexually and produce sexual offspring by selfing (sisters mate with their clonal brothers). These offspring diapause and form populations consisting of selfed sibships in the following spring. In 12 of 13 experimental populations, genotypes of selfed hatchlings after diapause conformed to Mendelian expectations. During the subsequent ca. 10 asexual generations, however, genotype frequencies changed significantly at 19 of 27 single loci studied within populations, mostly in favour of heterozygotes, with heterozygosity at multiple loci affecting the change in genotype frequency multiplicatively. Because variance in heterozygosity among siblings at a given marker reflects only heterozygosity in the chromosomal region around this marker, our results suggest that selection at fitness-associated loci in the chromosomal regions near the markers were responsible for these changes. The genotype frequency changes were more consistent with selection acting on linked loci than on the allozymes themselves. Taken together, the evidence for abundant selection in the chromosomal regions of the markers and the fact that changes in genotype frequencies became apparent only after several generations of clonal selection, point to a genetic load consisting of many alleles of small or intermediate effects, which is consistent with the strong genetic differentiation and repeated genetic bottlenecks in the metapopulation from which the animals for this study were obtained.

Nematophagous Fungi Associated with Root Galls of Rice Caused by Meloidogyne graminicola and its Control by Arthrobotrys dactyloides and Dactylaria brochopaga

AbstractRoot galls of rice caused by Meloidogyne graminicola were examined for natural colonization by nematophagous fungi from four fields with different nematode infestations. Old galls from severely infested fields had a higher frequency of Monacrosporium eudermatum and Stylopaga hadra than young galls. The frequency of Arthrobotrys oligospora, Arthrobotrys dactyloides, Dactylaria brochopaga and Monacrosporium gephyropagum was lower. A greater proportion (%) of root galls were colonized by nematophagous fungi in those fields in which rice roots had a greater root gall index. This indicated that disease severity supported the colonization of galls by nematophagous fungi. In vitro predacity tests of four fungi showed that A. dactyloides was most effective in capturing and killing J2 of Mel. graminicola followed by D. brochopaga and Mon. eudermatum. Application of inocula of A. dactyloides and D. brochopaga in soil infested with Mel. graminicola, respectively, reduced the number of root galls by 86% and of females by 94%, and eggs and juveniles by 94%. The application of these fungi to soil increased plant growth: shoot length by 42.7% and 39.8%, root length by 45.5% and 48.9%, fresh weight of shoot by 59.9% and 56.7% and fresh weight of root by 20.3% and 25.1%, respectively, compared to these parameters for plants grown in nematode‐infested soil.

Abiotic and biotic factors influencing the early stages of vegetation colonization in restored marly gullies (Southern Alps, France)

In the French Southern Alps, erosion-control experiments have been conducted since spring 2002 in marly catchments subjected to a mountainous and Mediterranean climate. Bioengineering works, installed in the gully beds and constituted as vegetation barriers, have been efficient in trapping sediment, thus creating sediment deposits upstream of each barrier. Natural colonization of these deposits by vegetation, which could enhance soil protection against erosion, have therefore been observed. From 2003 to 2005, we investigated the abiotic and biotic factors influencing plant establishment after restoration on 29 bioengineering works constructed in two experimental marly gullies. On the sediment deposits upstream of each structure, we identified the standing vegetation, measured species richness and abundance, and also evaluated vegetation cover on the gully sides. The results indicate that colonization by plants may be influenced by abiotic factors such as the presence of vegetation on the gully sides and climatic conditions. In addition, the ability of the bioengineering works to retain water seems to have an impact on the success of vegetation establishment. Finally, we highlighted changes in growth form proportions over time that may result from biotic factors such as plant–plant interactions. These results allow us to hypothesize on how vegetation evolves over the medium term after ecological restoration of eroded marly gullies in a mountainous and Mediterranean climate.

Natural and man-induced revegetation on mining wastes: Changes in the floristic composition during early succession

The performance of introduced species when interacting with colonising herbs and shrubs from the surrounding areas has become an important issue in plant ecology and restoration management. In this paper, we examined the influence of hydroseeding a commercial seed mixture on the revegetation of uranium mine wastes under a semi-arid Mediterranean climate in West-Central Spain. Eight dump slope sites differing two by two in revegetation treatment (hydroseeding or not) and aspect (north/south) were monitored annually during 3 years. There was a combined effect of treatment and aspect on the floristic composition during early succession. Particularly, hydroseeding increased differences in floristic composition between aspects, being the contribution of sown species to these differences small and short. Hydroseeding increased plant cover and diversity significantly only 2 years after its application on the north-facing slopes, favoured the perennial species (mainly hemicryptophytes), and had a different effect depending on the aspect favouring grasses and legumes on the north- and south-facing slopes, respectively. The species mixture was not suitable and the use of local seeds should be tested in future revegetation projects at this zone. The importance of improving natural colonisation for ecological restoration is emphasised.

Long‐term effectiveness of sowing high and low diversity seed mixtures to enhance plant community development on ex‐arable fields

AbstractQuestions: How is succession on ex‐arable land affected by sowing high and low diversity mixtures of grassland species as compared to natural succession? How long do effects persist?Location: Experimental plots installed in the Czech Republic, The Netherlands, Spain, Sweden and the United Kingdom.Methods: The experiment was established on ex‐arable land, with five blocks, each containing three 10 m × 10 m experimental plots: natural colonization, a low‐ (four species) and high‐diversity (15 species) seed mixture. Species composition and biomass was followed for eight years.Results: The sown plants considerably affected the whole successional pathway and the effects persisted during the whole eight year period. Whilst the proportion of sown species (characterized by their cover) increased during the study period, the number of sown species started to decrease from the third season onwards. Sowing caused suppression of natural colonizing species, and the sown plots had more biomass. These effects were on average larger in the high diversity mixtures. However, the low diversity replicate sown with the mixture that produced the largest biomass or largest suppression of natural colonizers fell within the range recorded at the five replicates of the high diversity plots. The natural colonization plots usually had the highest total species richness and lowest productivity at the end of the observation period.Conclusions: The effect of sowing demonstrated dispersal limitation as a factor controlling the rate of early secondary succession. Diversity was important primarily for its‘insurance effect’: the high diversity mixtures were always able to compensate for the failure of some species.

Road Slope Revegetation in Semiarid Mediterranean Environments. Part I: Seed Dispersal and Spontaneous Colonization

Abstract The importance of neighboring vegetation as a seed reservoir for spontaneous colonization of adjacent road slopes was analyzed in a semiarid region of east Spain. Two independent methodological approaches were used to examine the relative contribution of seed from neighboring vegetation and the efficiency of different seed dispersal strategies in plant colonization. We first used a randomization test to compare floristic similarity between road slopes, neighboring flora, and local flora (the regional species pool found in the same climate and soil conditions as the road slopes). Second, we compared seed dispersal mechanisms of road slope vegetation with those of the surrounding area using frequency analysis. Species composition of road slopes was more similar to that of the flora of adjacent surrounding areas than expected by chance. Anemochorous (wind‐dispersed) plants were over‐represented in road slopes 8 years after road slopes were built. We concluded that seed dispersal from neighboring vegetation is an important factor in the vegetative colonization of road slopes. However, this initial species pool was also strongly shaped by the harsh environmental conditions of roadcuts and southern aspect. These results have important implications in road slope restoration because they suggest that naturally vegetated areas should be maintained adjacent to road slopes to enhance seed immigration from species adapted to local site conditions, which will accelerate the successional process. The application of this single reclamation strategy and mixed strategies that combine the use of natural colonization and soil amendment for road slope restoration in Mediterranean environmental conditions is discussed.

Impact of exotic plantations and harvesting methods on the regeneration of indigenous tree species in Kibale forest, Uganda

AbstractExotic plantations of Cupressus lusitanica Mill, Pinus caribaea Morolet and Eucalyptus species were established in the grasslands of Kibale Forest Reserve during the late 1960s and early 1970s. Thirty years later (1995), plantation harvesting began based on pitsawing and sawmilling methods. This study aimed at assessing the effect of logging exotic plantations and the methods of harvesting on the young regeneration of indigenous tree species. Sample plots were randomly established in the plantations in the sawmilled and pitsawn areas. All tree stems over 1.3 m in height were identified, diameter at 1.3 m and height measured. The plantations showed a total of 91 tree species with the logged C. lusitanica and P. caribaea areas exhibiting higher number of tree species (79 and 78 respectively) than Eucalyptus (55). The pioneer, colonizing and secondary forest species contributed significantly to the density of regeneration in logged C. lusitanica (2170.5 t ha−1), P. caribaea (2309.2 t ha−1) and eucalyptus (1513.7 t ha−1) areas. The Climax species were still very low and the species very scanty. While pitsawing and sawmilling seem to have had little influence on species richness (Ps = 63, Sm = 65), pitsawing encouraged higher tree regeneration densities (ps = 2223.5 t ha−1) than sawmilling (Sm = 1822 t ha−1). Deductively, C. lusitanica and P. caribaea plantations could be used economically in afforestation, reforestation and accelerated natural forest colonization.