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[pt] Este trabalho examina o problema da atenuação por chuvas na propagação da energia em freqüências superiores a 10 ghz, com especial ênfase na aplicação dos resultados em regiões de clima tropical. São discutidos em detalhes os métodos existentes para caracterizar a distribuição estatística pontual da precipitação em uma região. Apresenta-se uma solução semi-empírica para a questão da não uniformidade espacial da distribuição de chuvas em um percurso, empregando o conceito de precipitação equivalente e dados de inúmeros trabalhos experimentais publicados na literatura técnica para diversas freqüências e distancias. Finalizando é feito um exemplo ilustrativo do método proposto, tomando por base os dados pluviográficos do Rio de Janeiro. / [en] This work deals with the problem of rainfall attenuation at frequencies above 10 GHz. Particular enphasis is given to the application of the final results for communications links in a tropical region. The proposed nethods to characterize the punctual rainfall statistical distribution in a specific region are discussed in detail. A solution to the problem of a non-uniform spatial distribution of the rainfall through the propagation path is presented, the concept of equivalent precipitation being applied. A big amount of experimental data from the technical literature was utilized, for different frequencies and distances. Finaly, an example of the proposed method is presented, along with an application based upon Rio de Janeiro rain data.

Biodiversity monitoring and predictions of species occurrence are essential to develop outcome-oriented conservation management plans for endangered species and assess their success over time. To assess distribution and patterns of habitat use of large mammal assemblages in Thailand, with a focus on the endangered dhole (Cuon alpinus), I first implemented a long-term camera-trapping project carried out with park rangers from October 2003 through October 2007 in Khao Yai National Park. This project was extremely successful and may serve as a regional model for wildlife conservation. I found significantly lower relative abundance indices for carnivore species, and collectively for all mammals compared to data obtained in 1999-2000, suggesting population declines resulting from increased human activity. I integrated this data into maximum entropy modeling (Maxent) to further evaluate whether ranger stations reduced poaching activity and increased wildlife diversity and abundances. I then conducted a focused camera trap survey from January 2008 through February 2010 in Khao Ang Rue Nai Wildlife Sanctuary to gather critical baseline information on dholes, one of the predator species that seemed to have declined over time and that is exposed to continued pressure from humans. Additionally, I led a collaborative effort with other colleagues in the field to collate and integrate camera trap data from 15 protected areas to build a country-wide habitat suitability map for dholes, other predators, and their major prey species. The predicted presence probability for sambar (Rusa unicolor) and leopards (Panthera pardus) were the most important variables in predicting dhole presence countrywide. Based on my experience from these different field ecological surveys and endeavors, it became clear that local people's beliefs may have a strong influence on dhole management and conservation. Thus, I conducted villager interview surveys to identify local attitudes towards dholes, document the status of dholes in wildlife sanctuaries adjacent to Cambodia, and determine the best approach to improve local support for dhole conservation before proceeding with further field studies of the species in Thailand. A photograph of a dhole was correctly identified by only 20% of the respondents. My studies provide evidence that some protected areas in Thailand continue to support a diversity of carnivore speices of conservation concern, including clouded leopards (Neofelis nebulosa), dholes, and small felids. However, dholes' impact on prey populations may be increasing as tiger (Panthera tigris) and leopards are extripated from protected areas. The next step in dhole conservation is to estimate the size and stability of their fragmented populations and also focus on maintaining adequate prey bases that would support both large felids and dholes

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No description available.

Eutrofieringen i Östersjön har länge varit ett omfattande miljöproblem, med ökad algblomning, syrebrist och döda bottnar som följd. Dessa problem uppstår då det tillförs ett överskott av närsalterna kväve och fosfor. Detta närsaltsläckage kommer till stor del från mänsklig aktivitet, varav stora mängder kommer från jordbruket.  Syftet med detta projekt är för det första att kartlägga dagens kunskapsläge kring vilka åtgärder som kan implementeras för att minska närsaltstransporten i vattendrag. Vidare syftar projektet till att undersöka hur den rumsliga placeringen av dessa åtgärder påverkar närsaltsretentionen samt hur närsaltsläckagets fördelning påverkar detta. Detta har gjorts genom att bygga upp en modell där åtgärdernas placering, storlek och antal såväl som kväveläckagets fördelning varieras för att studera hur näringsbelastningen till nedströms recipient påverkas. Modelleringen har avgränsats till att endast undersöka våtmarker och kväve.  Resultatet av modelleringen visar att en stor våtmark placerad nära utloppet ger högst total näringsretention. Vidare visar resultatet att både kvävekoncentrationer i vattendragen och retentioner i enskilda våtmarker inom området påverkas av kväveläckagets rumsliga fördelning, vilket tyder på att även detta behöver beaktas för att kunna skydda vattenförekomster inom landskapet. Resultatet visar också på att den bästa våtmarksplaceringen är strax uppströms om den recipient som ska skyddas. / The Baltic Sea suffers from eutrophication, which leads to increased algae growth, affecting the water quality and the surrounding ecosystems. This has been an extensive environmental problem for a long time and the main cause of this problem is excessive inputs of nitrogen and phosphorus. These nutrient inputs occur in great parts due to human activities and a significant proportion originates from agriculture. Non-point sources, such as nutrients lost from agricultural soils, are difficult to locate and consequently it’s hard to implement the right measure in the right place.  One of the objectives of this report is to map out which measures that can be implemented in watercourses to increase the nutrient retention. The report also aims to analyze how the spatial distribution of these measures, as well as the nutrient input, affects the nutrient retention. This has been done by creating a model, where wetlands can be positioned in different places within a catchment area. The model has been limited to only analyze wetlands and nitrogen. The positioning, area and number of the wetlands as well as the nitrogen input was varied in order to analyze how the retention was affected.  The result of this modelling showed that the highest nutrient retention in total was achieved by placing one big wetland close to the outlet of the studied area. Furthermore, the concentration and retention of nitrogen within the area varied when the distribution of the nitrogen input was altered, which indicates that it’s important to analyze this in order to improve the water quality within the landscape. Finally, to obtain the highest efficiency of a wetland, the wetland should be placed just above the recipient it’s intended to protect.

Arsenic, which is a naturally occurring element in the severe health issues during exposure. Both the World Health Organisation and The Swedish Environmental Protection Agency (Naturvårdsverket) state that >10 ppm arsenic in bedrock is already concerning. During a construction of a new highway junction in the Arlanda-Rosersberg area soil samples revealed elevated levels of arsenic. Since it poses a risk to public health and further spreading without knowledge about the origin and extent of the contamination, the Swedish Geological Survey undertook an investigation to address this issue which included geological mapping as well as geochemical analysis of the whole rock samples.  This thesis has used the collected geochemical data to visualise the spatial distribution of arsenic over the project area to examine if there is a correlation between elevated concentrations and specific lithologies, or if other processes such as pegmatite formation could be responsible enrichment. Kernel interpolation with ArcGIS Pro was used to create three maps with unique parameters: without geological barriers, with geological barriers including samples taken from nearby pegmatites, and with geological barriers excluding samples taken from nearby pegmatites. The resulting maps indicate that a majority of the project area far exceeds the recommended limit, regardless of the parameters.  Based on the data it is currently impossible to distinctly determine the origin of the arsenic contamination, since the results suggest a role of both lithological correlation and process-related source, and a combination of both cannot be ruled out. Therefore, to improve the resolution and knowledge about the area, more extensive examination and gathering of data would be beneficial, as well as implementing improvements of the method to better simulate the mobilisation of arsenic. / Arsenik är ett naturligt förekommande grundämne i berggrunden som är känt för att orsaka allvarliga problem för människors hälsa vid exponering. Både World Health Organisation och Naturvårdsverket uppger att >10 ppm arsenik i berggrunden är oroväckande. Vid byggandet av en motorvägsavfart i Arlanda-Rosersbergs området visade jordprover höga koncentrationer av arsenik. Eftersom det utgör en risk för människors hälsa, samt fortsatt spridning utan kunskap om ursprung och utsträckning av kontaminationen, utförde Sveriges Geologiska Undersökning (SGU) ett projekt vilket inkluderade geologisk kartläggning samt geokemiska analyser.  Det här självständiga arbetet har använt det geokemiska data för att visualisera den rumsliga spridningen av arsenik över projektområdet för att undersöka om det finns ett samband mellan höga koncentrationer och geologiska enheter, eller om magmatiska processer som bildandet av pegmatit kan vara källan till arsenik. Kernel interpolation med ArcGIS Pro användes för att skapa tre kartor med unika parametrar: utan geologiska barriärer, med geologiska barriärer inklusive prover tagna i närheten av pegmatiter, med geologiska barriärer exklusive prover tagna i närheten av pegmatiter. De resulterande kartorna indikerar att en majoritet av projektområdet överskrider den rekommenderade gränsen, oavsett parametrar.  Baserat på data är det vid nuläget omöjligt att avgöra ursprunget av arsenik, eftersom resultatet indikerar både geologiskt samband och process relaterad källa, därför kan en kombination av dem inte uteslutas. För att förbättra kunskapen om området krävs mer omfattande undersökning och data, samt förbättringar av metoden för att bättre simulera mobiliseringen av arsenik.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The 21st Century is witnessing the concurrence of neoliberal globalisation and widespread informalisation. To this extent, the informal sector or economy is perceived as a permanent ‘feature of modern capitalist development’ (Chen 2007: 2). Its expansion, particularly in developing countries, has far reaching implications for employment generation, occupational or livelihood diversification, urban form dynamics, urban planning, as well as the general economic outcome. The historical evolutionary truth of the informal origin of most businesses coupled with the reality of informal-formal sector continuum gives credence to the critical imperative of multi-path development regime that does not consider the informal sector as a dead end. Consequently, the research explored the policy implications of the spatial and structural relationships between the informal and formal business sectors in urban Nigeria. The study region is viewed from the prism of Enugu, the major administrative centre in the southeast region of the country. Here, spatial-structural causalities at the city level are conjectured as surrogates of the globalisation-induced transformations occurring in the country from 1990 to 2010 (Andranovich & Riposa 1993). The research sought to: one, examine the extent relationships between the distribution structures of two economic segments in the city; and two, explore the changes in inter-sectoral linkages and the urban business landscape mediated by the global-local economic changes. To guide the study, two research hypotheses were formulated, viz.: (1) to prove whether or not some significant spatial/structural relationships exist between the distribution of informal and formal business units in the study area; and (2) to verify if the observed changes in the spatial and structural relationships between the two segments are accounted for by the same sets of physical, economic, and socio-cultural variables. The study made use of primary and secondary data, which were collected via mixed research methods. The proportional stratified sampling was used where necessary. The primary data were collected through casual observation/recognisance, photographic and questionnaire surveys, and semi-structured personal interviews; while the secondary data were sourced from literature review, maps and databanks of local governments and Federal Inland Revenue Service (FIRS). The data analytical procedure involved data reduction and hypotheses testing. The former technique consists of sectoral aggregation (the segmentation by coherent attribute-sectors) and spatial aggregation (translation from quantitative into spatial dimensions) (Wang & Vom Hofe 2007), while the latter required the use of Spatial Statistics Analysis toolsets of the ArGIS software and the Principal Component Analysis (PCA) of the SPSS package. The Spatial Statistics Analysis (the Spatial Autocorrelation or Moran’s I index) and PCA results permitted the rejection of the two null hypotheses respectively. The Moran’s I index is 0.16 with a Z score of 159.78 at a significant level of .01 and critical value of 2.58, revealing a highly clustered spatial association (or dependence) between the informal and formal business distribution in the study area. Based on the eigenvalues of 10 selected variables, the PCA extracted three major determinants of the observed spatial-structural causalities, namely: socio-economic and cultural traits or business ethos, client base and market control, and physical environment/business transaction mode. The findings challenges the received model of Nigeria retail hierarchy, and among the key recommendations for guaranteeing stronger informal-formal sector linkages that are generative of sustainable endogenous development are: (i) the reinstatement of the import substitution programme; (ii) implementation of the innovative Cluster Concept of Industrial Development Strategy (CCIDS) of 2007; and (iii) adoption of urban planning standards that are pro-informal sector. / AFRIKAANSE OPSOMMING: In die 21ste eeubeleefonsgelyktydigneoliberaleglobalisasie en wydverspreideinformalisasie. Samelopendhiermee word die informelesektorvandieekonomiegesien as ’n “permanentekenmerk van die kapitalistieseontwikkeling.” (Chen 2007: 2). Die uitbreidingdaarvan, veral in ontwikkelendelande, het verreikendeimplikasies vir die skepping van werksgeleenthede, die diversifikasie van loopbaan- en broodwinnings-moontlikhede, stedelikevorms, stedelikebeplanning, asookalgemeneekonomieseuitkomstes. Die historieseevolusionêrewaarheidoor die oorsprong van die meestebesighede, tesame met die realiteit van die informelesektorkontinuum, verleengeloofwaardigheidaandie kritiesebelangrikheid van die multi-pad ontwikkelingraamwerkwaarbinne die informelesektorniegesien word as ’n doodloopstraatnie. Gevolglik het die navorser die beleidsimplikasies van die ruimtelike- en struktureleverhoudingtussen die informele en die formele sake-sektors in stedelikeNigeriëondersoek. Die studiegebied word besigtigvanuit die prisma van Enugu, die hoof administratiewesentrum van die suidelikestreek van Nigerië. Hier word ruimetelik-struktureleoorsaaklikhedegebruik as maatstawwe vir die transformasieswatdeurglobalisasieveroorsaak is, en wattussen 1990 en 2010 in die land plaasgvind het (Andranovich&Riposa 1993). Daar is in die navorsinggepoog om eerstens die omvang van verwantskappetussen die verspreidingstrukture van die twee ekonomiesesegmente van die stad vas te stel, en tweedens, om die veranderings in inter-sektorieseskakels en die stedelike sake landskapwatdeur die globaale-plaaslikeekonomieseveranderingsbemiddel is, te bestudeer. Twee navorsinghipoteses is geformaliseer, naamlik (1) om te bewys of daarbetekenisvolleruimtelike/struktureleverwantskappebestaantussen die verspreiding van informele en formeleeenhede in die studie- gebied, en (2) om te bevestig of die veranderings in die ruimtelike en struktureleverwantskappetussen die twee besigheidsegmentetoegeskryfkan word aandieselfdestelfisiese, ekonomiese en sosio-kultureleveranderlikes. In die studie is daargebruikgemaak van primêre en sekondêre data watdeurmiddel van gemengdenavorsingmetodesversamel is. Die proporsioneelgestratifiseerdesteekproefmetode is, waarnodig, gebruik. Die primêre data is deurterloopseobservasie, fotografiese- en vraelysopnames, en semi-gestruktureerde persoonlike onderhoudeversamel, terwyl die sekondêre data verkry is uit ’n oorsig van die letterkunde, landkaarte, en die databanke van plaaslikeowerhede en die binnelandsebelastingsdiens. (FIRS). Die data ontledingsproses het data reduksie en hipotesetoetsingingesluit. Dievorigetegniekbestaanuitsektorieseaggregasie (segmentasiedeursamehandeattribuutsektore) en ruimtelikeaggregasie (oorgesitvanafkwantitatiewenaruimtelikedimensies) (Wang & VomHofe 2007). Vir die laasgenoemde was dit nodig om Spatial Statistics Analysis gereedskapstel van die ArGISsagteware en die Principal Component Analysis (PCA) van die SPSS paket te gebruik. The Spatial Statistics Analysis (die Spatial Autocorrelation of Moran se I indeks) en die PCA resultatehet die verwerping van die twee nulhipotesesmoontlikgemaak. Moran se I indeks is 0.16 met ’n Z telling van 159.78 teen ’n betekenisvollevlak van .01 en ’n kritiesewaarde van 2.58, wat ’n hoogsgetrosderuimetlikeassosiasieaantoon, of dat die verspreiding van die informele en formelebesighede in die studiegebiednabymekaargeleë en afhanklik is van mekaar. Gegrond op die eigenwaardes van die 10 gekoseveranderlikes, is daardeur die PCA bepaalwat die drie hoof ruimtelik-strukturelekousaliteite is. Dit is sosio-ekonomiese en kulturelekenmerke, kliente basis en markbeheer, en fisieseomgewing/sake transaksie modus. Die bevindingeverskil van die ontvangdemodel van die Nigeriesehierargie. Om sterkerinformele-formeleskakelswatvolhoubareendogeneontwikkelingwaarborg, te genereer, word die volgendeaanbevelingsgemaak: (i) die invoerplaasvervangings-program moetingestel word, (ii) die Cluster Concept of Industrial Development Strategy (CCIDS) van 2007 moet implementer word; en (iii) stedelikebeplanningstandaardewat pro-informelesektor is, moet aanvaar word.

Summary: Floristic, Ecological and Phytosociological, Study of the Forests of the Mbiye Island at Kisangani, DR Congo The Mbiye Island is situated on the Congo River, in the Eastern part of Kisangani. It is located upstream of the Wagenia Falls, between latitude 0º31’ North and longitude 25º11’ East, with 376 m of altitude. It adjoins the town of Kisangani, and it is 14 km long and 4 km wide. All around Kisangani, the Mbiye Island is the only ecosystem which has a dense forest that is relatively well preserved. This Island has an area of 1,400 ha, and it comprises three types of forest: dry land forest, periodically flooded forest and swampy forest. The main purpose of this study has been to make a qualitative and quantitative analysis of the physiognomy and structure of these three types of forest. I relied on two methods in data collecting: the Phytosociological plotting method with a sampling equal to 100 individuals for the higher strata and 100 m² grass strata, associated with dbh measure for trees whose diameter is ≥ 10 cm. In total, out of the 80 plottings, 67 multi strata and structurals each of which has been decomposed in 4 sub-plottings fit together. Based on the presence-absence criterion, the other 13 multi strata and structurals have been made into Chablis, and all the data have been globally analyzed. An inventory of 33991 individuals has been made in this study. After their identification, it has been found out that there 470 species belonging to 297 types and 90 families. Rubiaceae, Caesalpiniaceae and euphorbiaceae families have been found out to be the most important in Genus and species. In the raw spectra of biological types, the phanerophyts (83.0%) are the most predominant, and within which the mesophanerophyts (trees 10 to 30 m tall in their old age) are the most predominant (39.0%). The Phytogeographical spectra have more omni-guineo-congolese (35%) elements; and amongst the diaspore types, the sarcochores (69%) are the most predominant. 58 endemic species (12.3%) of the central forest sector have been found out at the Mbiye Island. After the classification and ordination of the 80 plottings by Twinspan and DCA, three Phytosociological groupings have been found out in the dry land forest: (1) grouping of Funtumia elastica and Albizia ealaensis, (2) grouping of Nesogordonia leplaei and Antiaris toxicaria, (3) prouping of Olyra latifolia and Campylospermum elongatum; two others for floodable forests (1) grouping of Rinorea oblongifolia and Byrsocarpus coccineus, (2) grouping of Pachystela seretii, Dracaena kindtiana and Culcasia yangambiensis, and three others for swampy forests: (1) grouping of Strombosia grandifolia, Calamus deerratus, Culcasia angolensis and Elaeis guineensis, (2) grouping of Cleistopholis patens and Pterygota bequaertii, (3) grouping of Diospyros bipendensis, Strychnos icaja and Palisota barteri and then two groupings for the Chablis plottings (1) grouping of Palisota schweinfurthii, Eremospatha haullevilleana, Thomandersia hensii and Pycnocoma insularis and (2) grouping of Nephrolepis biserrata and Scaphopetalum thonneri. The coelocaryon botryoides has shown a uniform spatial distribution in the in the forest periodically flooded, whereas Gilbertiodendron dewevrei has shown an aggregated distribution. Comparison of richness in different taxa within the sampling has given high values as far as the numbers of species is concerned and genus of the same family in the phytosociological sampling. Out of all the species listed, 189 have been considered to be common species with regard to the three forest types, other 144 belonged to two types. 90 species have been listed only on solid land, 27 on periodically flooded forest 20 on swampy forest. Euphorbiaceae, Rubiaceae and Caesalpiniaceae families were the best represented in species and genus. With regard to richness in each forest type, the forest of solid soil was the only one to have high values both in species and genus, and the swampy forest was less represented. With reference to richness according to strata, the herbaceous and under-shrub stratum (H) was the richest whereas the stratum of dominant trees (E+A1) was the poorest. Mbiye island forest is the nearest one of Kisangani for which it plays the most important role with regards to supplies in different forest products and non-ligneous forest products. In total, 12.3% endemic species of Central forest sector have been listed there, but due to frequent use by man this time, all these endemic species may disappear from this island. It is therefore urgent that particular attention be paid on it. Actions of conservation and lasting exploitation must be started in order to block their extinction. Key words: DRCongo, Flora, Ecology, Phytosociology, insularity, flooding, spatial distribution, biodiversity, synusie, Mbiye Island, Kisangani./Résumé : Etude floristique, écologique et phytosociologique des forêts de l'île Mbiye, Kisangani, RDCongo. L'île Mbiye est une île du fleuve Congo située dans la partie Est de la ville de Kisangani, en amont des chutes Wagenia, entre 0° 31' de latitude Nord et 25° 11' de longitude Est, avec une altitude de 376 m. Elle jouxte la ville de Kisangani et sa longueur maximale est de 14 km sur 4 km de largeur. Elle est le seul écosystème à proximité de la ville, possédant encore une forêt dense relativement bien conservée et formant un îlot de 1400 ha comprenant trois types forestiers : la forêt de terre ferme, la forêt périodiquement inondée et la forêt marécageuse. L’objectif principal de cette étude a été de faire une analyse quantitative et qualitative de la physionomie et la structure de ces trois types forestiers. Deux méthodes ont permis la récolte de données ; la méthode de relevés phytosociologiques à effort d’échantillonnage égal à 100 individus pour les strates supérieures et 100 m² pour la strate herbacée, associée à celle de mesure de D130, pour les arbres à diamètre ≥ 10 cm. Au total, 80 relevés dont 67 multistrates et structurels, décomposés chacun en 4 sous-relevés emboîtés, ont été mis en place. 13 autres ont été faits dans les chablis avec l’appréciation basée sur le critère de présence-absence et toutes les données ont été analysées globalement. A l’issue de cette étude, 33991 individus ont été recensés. Après leur identification, au total 470 espèces appartenant à 297 genres et 90 familles ont été obtenues. Les familles des Rubiaceae, des Caesalpiniaceae et des Euphorbiaceae sont les plus importantes, tant en genres qu’en espèces. Dans les spectres bruts de types biologiques, les phanérophytes (83,0 %) sont les plus abondants et au sein desquels les mésophanérophytes (arbres de 10 à 30 m au stade adulte) sont les plus dominants (39,0 %). Les spectres phytogéographiques ont montré une prédominance d’éléments omni-guinéo-congolais (35 %) alors que parmi les types de diaspores, les sarcochores (69 %) sont les plus dominants. 58 espèces endémiques du Secteur forestier central (soit 12,3 %) ont été recensées à l’île Mbiye. Après classification et ordination de ces 80 relevés par Twinspan et DCA, trois groupements phytosociologiques ont été obtenus dans la forêt de terre ferme: (1) groupement à Funtumia elastica et Albizia ealaensis, (2) groupement à Nesogordonia leplaei et Antiaris toxicaria, (3) groupement à Olyra latifolia et Campylospermum elongatum ; deux autres pour les forêts inondables (1) groupement à Rinorea oblongifolia et Byrsocarpus coccineus, (2) groupement à Pachystela seretii, Dracaena kindtiana et Culcasia yangambiensis ; trois autres encore pour les forêts marécageuses : (1) groupement à Strombosia grandifolia, Calamus deerratus, Culcasia angolensis et Elaeis guineensis, (2) groupement à Cleistopholis patens et Pterygota bequaertii, (3) groupement à Diospyros bipendensis, Strychnos icaja et Palisota barteri, et enfin, deux groupements pour les relevés de chablis (1) groupement à Palisota schweinfurthii, Eremospatha haullevilleana, Thomandersia hensii et Pycnocoma insularum et (2) groupement à Nephrolepis biserrata et Scaphopetalum thonneri. L’espèce Coelocaryon botryoides a montré une répartition spatiale uniforme dans la forêt périodiquement inondée alors que Gilbertiodendron dewevrei y a montré une répartition agrégée. La comparaison de la richesse en différents taxa au sein de relevés et de placettes a donné de valeurs supérieures en nombre d’espèces, de genres et même de familles, dans les relevés phytociologiques. Sur le total des espèces recensées, 189 ont été considérées comme espèces communes aux trois types forestiers, 144 autres appartenaient aux deux types. 90 espèces n’ont été recensées qu’en forêt de terre ferme, 27 en forêt périodiquement inondée et 20 dans la forêt marécageuse. Les familles des Euphorbiaceae, des Rubiaceae et celle des Caesalpiniaceae ont été les mieux représentées en espèces et en genres. En ce qui concerne la richesse dans chaque type forestier, la forêt de terre ferme était la seule à avoir des valeurs supérieures tant en espèces qu’en genres et la forêt marécageuse était la moins représentée. Quant à la richesse spécifique selon les strates, la strate herbacée et sous-arbustive (H) était la plus riche alors que la strate des arbres dominants (E+A1) était la plus pauvre. La forêt de l’île Mbiye est la seule forêt proche de la ville de Kisangani pour laquelle elle joue un rôle de premier plan en ce qui concerne le ravitaillement en différents produits forestiers et forestiers non ligneux. Au total, 12,3% d’espèces endémiques du Secteur forestier Central y ont été recensées, mais vue l’action anthropique qu’elle connaît ce dernier temps, toutes ces espèces endémiques risquent de disparaître de cette île. Il est alors urgent qu’une attention particulière, soit tournée vers elle. Des actions de conservation et d’exploitation durable doivent être amorcées en vue contrecarrer l’extinction des celles-ci. Mots clés : RDCongo, flore, écologie, phytosociologie, insularité, inondation, répartition spatiale, biodiversité, synusie, île Mbiye, Kisangani.

Introduction and objectives In Vietnam, the forest resources have been declining and degrading severely in recent years. The degradation has decreased the natural forest area, changed the forest structure seriously and reduced timber volume and biodiversity. From 1999 to 2005, the rich forest area has decreased 10.2%, whereas the poor secondary forest has increased dramatically by 20.7%. Forest structure plays an important role in forestry research. Understanding forest structure will unlock an understanding of the history, function and future of a forest ecosystem (Spies, 1998). The forest structure is an excellent basis for restoration measures. Therefore, this research is necessary to contribute to improving forest area and quality, reducing difficulties in forest management. The study also enhances the grasp of forest structure, structure changes after harvesting and fills serious gaps in knowledge. In addition, the research results will contribute to improving and rescuing the poor secondary forest and restoring it, approaching the old-growth forest in Vietnam. Material and methods The study was conducted in Kon Ka Kinh national park. The park is located in the Northeastern region of Gia Lai province, 50 km from Pleiku city center to the Northeast. The park is distributed over seven different communes in three districts: K’Bang, Mang Yang and Đăk Đoa. Data were collected from 10 plots of secondary forests (Type IIb) and 10 plots of primeval forests (Type IV). Stratified random sampling was applied to select plot locations. 1 ha plots were used to investigate gaps. 2000 m2 plots were used to measure overstorey trees such as diameter at breast height, total height, crown width and species names. 500 m2 subplots were used to record tree positions. For regeneration, 25 systematic 4 m2 subplots were established inside 1 ha plots. After data were collected in the field, data analyses were conducted by using R and Excel. Firstly, some stand information, such as density, volume and so on, was calculated, and then descriptive statistics were computed for diameter and height variables. Linear mixed effect models were applied to analyze the difference of diameter and height and to check the effect of random factor between the two forest types. Diameter and height frequency distributions were also generated and compared by using permutational analysis of variance (PERMANOVA). Non-linear regression models were analyzed for diameter and height variables. Similar analyses were implemented for gaps. Regarding spatial point patterns of overstorey trees, replicated point pattern analysis techniques were applied in this research. For biodiversity, some calculations were run such as richness and biodiversity indices, comparison of biodiversity indices by using linear mixed models and biodiversity differences between two forest types tested again by permutational analysis of variance. In terms of regeneration, some analyses were implemented such as: height frequency distribution generation, frequency difference testing, biodiversity indices for the regeneration and spatial distribution checking by using a nonrandomness index. Results and discussion After analyzing the data, some essential findings were obtained as follows: Hypothesis H1 “The overstorey structure of secondary forests is more homogeneous and uniform than old-growth forests” is accepted. In other words, the secondary forest density is about 1.8 times higher than the jungle. However, the volume is only 0.56 times as large. The average diameter and height of the secondary forest is smaller by 5.71 cm and 3.73 m than the old-growth forest, respectively. Linear mixed effect model results indicate that this difference is statistically different and the effect of the random factor (Section) is not important. Type IIb has many small trees and the diameter frequency distribution is quite homogeneous. The old-growth forest has more big trees. For both forest stages, the height frequency distribution is positively skewed. PERMANOVA results illustrate that the frequency distribution is statistically different between the two forest types. Regression functions are also more variant and diverse in the old-growth forest, because all standard deviations of the parameters are greater there. Gap analysis results indicate that the number of gaps in the young forest is slightly higher, while the average gap size is much smaller. The gap frequency distribution is statistically different between the two types. In terms of the spatial point pattern of overlayer trees, the G-test and the pair correlation function results show that trees distribute randomly in the secondary forest. In contrast, the spatial point patterns of trees are more regular and diverse in the old-growth forest. The spatial point pattern difference is not significant, and this is proved by a permutational t-test for pair correlation function (pcf). Envelope function results indicate that the variation of pcf in young forests is much lower than in the primary forests. Hypothesis H2 “The overstorey species biodiversity of the secondary forest is less than in the old-growth forest” is rejected. Results show that the number of species of the secondary forest is much greater than in the old-growth forest, especially richness. The richness of the secondary forest is 1.16 times higher. The Simpson and Shannon indices are slightly smaller in the secondary forest. The average Simpson index for both forest stages is 0.898 and 0.920, respectively. However, the difference is not significant. Species accumulation curves become relatively flatter on the right, meaning a reasonable number of plots have been observed. Estimated number of species from accumulation curves in two forest types are 105 and 95/ha. PERMANOVA results show that number of species and proportion of individuals in each species are significantly different between forest types. Hypothesis H3 “The number regenerating species of the secondary forest is less and they distribute more regularly, compared to the old-growth forest” is rejected. There are both similarities and differences between the two types. The regeneration density of the stage IIb is 22,930 seedlings/ha, greater than the old forest by 9,030 seedlings. The height frequency distribution shows a decreasing trend. Similar to overstorey, the richness of the secondary forest is 141 species, higher than the old-growth forest by 9 species. Biodiversity indices are not statistically different between two types. PERMANOVA results indicate that the number of species and the proportion of individuals for each species are also not significantly different from observed forest types. Nonrandomness index results show that the regeneration distributes regularly. Up to 95% of the plots reflect this distribution trend. Hypothesis H4 “Restoration measures (with and without human intervention) could be implemented in the regenerating forest” is accepted. The investigated results show that the secondary forest still has mother trees, and it has enough seedlings to restore. Therefore, restoration solutions with and without human intervention can be implemented. Firstly, forest protection should be applied. This measure is relevant to national park regulations in Vietnam. Rangers and other related organizations will be responsible for carrying out protection activities. These activities will protect forest resources from illegal logging, grazing and tourist activities. Environmental education and awareness-raising activities for indigenous people is also important. Another measure is additional and enrichment planting. It should focus on exclusive species of the overstorey in Type IIb or exclusive species of the primary forest. Selection of these species will lead to species biodiversity increase in the future. This also meets the purpose of the maximum biodiversity solution. Conclusion Forest resources play a very important role in human life as well as maintaining the sustainability of ecosystems. However, at present, they are under serious threat, particularly in Vietnam. Central Highland, Vietnam, where forest resources are still relatively good, is also threatened by illegal logging, lack of knowledge of people and so on. Therefore, it needs the hands of the people, especially foresters and researchers. Through research, scientists can provide the knowledge and understanding of the forest, including the structure and forest restoration. This study has obtained important findings. The secondary forest is more homogeneous and uniform, while the old-growth forest is very diverse. Biodiversity of the overstorey in the secondary forest is more than the primary. The number of regenerating species in the secondary forest is higher, but other indices are not statistically different between two types. The regeneration distribute regularly on the ground. The secondary forest still has mother trees and sufficient regeneration, so some restoration measures can be applied here. Findings of the study contribute to improve people’s understanding of the structure and the structural changes after harvesting in Kon Ka Kinh national park, Gia Lai. That is a key to have better understandings of the history and values of the forests. These findings and the proposed restoration measures address rescuing degraded forests in Central Highland in particular and Vietnam in general. And further, this is a promising basis for the management and sustainable use of forest resources in the future.