Today's arid and semi-arid zones of the Mediterranean are affected by desertification, resulting from various factors, including climatic variations and human activities such as overcultivation, overgrazing and deforestation. Afforestation programs are one of the most effective means in preventing desertification. For many years Libya has had afforestation programs in order to restore degraded land and in response to rapid desert encroachment in the north east of Libya, in the area called the Jabal Akhdar (Green Mountain), which has been investigated in this study. The purpose of this research was to investigate the relative roles of exotic compared to native tree species in preventing desertification and enhancing degraded land restoration in the Jabal Akhdar. The effect of environmental factors on exotic compared to native tree species have been assessed by observations on growth and reproductive success of the species, including variables of stocking rate, trunk diameter, tree height, crown diameter, tree coverage, natural mortality, felling and seedling regeneration, as well as calculated variables, derived from these measurements. The effects of methods and age of afforestation on the promotion of biological diversity have been investigated using the Shannon-Wiener diversity index. The effects of tree species on soil depth have also been investigated. Multivariate statistical analyses of site, species and environmental data, using both cluster analyses and factor analyses have been performed, with the aim of determining what is influencing the species, crops or differentiating between the sites, based on soil depth, angle of slope, altitude, rainfall and air temperature values. Pinus halepensis showed success in its growth and regeneration, particularly at higher altitudes and steeper slopes. Cupressus sempervirens was successful in growth and regeneration in the mountains. The exotic Eucalyptus gomphocephala was very successful in its growth, but did not regenerate well, while the exotic Acacia cyanophylla trees had a failure of both growth and regeneration. E. gomphocephala species appeared to favour relativley the flatter (non-mountain) sites, while A. Cyanophylla appeared to favour relativly the mountain sites. All the species responded positively to greater rainfall and deep soil, but they differed in where they were most likely to be successful. Environmental factors such as climate, terrain and soil are the main determinants of species distribution in the study area, in addition to their impact on the growth of the main trees. There appeared not to be any relationship between biodiversity and whether the main trees were native or exotic, and only P. halepensis showed any negative effect on the abundance of shrubs. There was greater diversity of trees and shrubs generally at the younger sites than the old sites. The present study emphasises the current mismanagement of planted forests, particularly with overgrazing contributing to desertification, through preventing tree growth and eliminating most sapling regeneration. This study concludes by making recommendations for more effective choice of tree species to plant, and for subsequent management to improve afforestation programmes in the Jabal Akhdar area.

Today's arid and semi-arid zones of the Mediterranean are affected by desertification, resulting from various factors, including climatic variations and human activities such as overcultivation, overgrazing and deforestation. Afforestation programs are one of the most effective means in preventing desertification. For many years Libya has had afforestation programs in order to restore degraded land and in response to rapid desert encroachment in the north east of Libya, in the area called the Jabal Akhdar (Green Mountain), which has been investigated in this study. The purpose of this research was to investigate the relative roles of exotic compared to native tree species in preventing desertification and enhancing degraded land restoration in the Jabal Akhdar. The effect of environmental factors on exotic compared to native tree species have been assessed by observations on growth and reproductive success of the species, including variables of stocking rate, trunk diameter, tree height, crown diameter, tree coverage, natural mortality, felling and seedling regeneration, as well as calculated variables, derived from these measurements. The effects of methods and age of afforestation on the promotion of biological diversity have been investigated using the Shannon-Wiener diversity index. The effects of tree species on soil depth have also been investigated. Multivariate statistical analyses of site, species and environmental data, using both cluster analyses and factor analyses have been performed, with the aim of determining what is influencing the species, crops or differentiating between the sites, based on soil depth, angle of slope, altitude, rainfall and air temperature values. Pinus halepensis showed success in its growth and regeneration, particularly at higher altitudes and steeper slopes. Cupressus sempervirens was successful in growth and regeneration in the mountains. The exotic Eucalyptus gomphocephala was very successful in its growth, but did not regenerate well, while the exotic Acacia cyanophylla trees had a failure of both growth and regeneration. E. gomphocephala species appeared to favour relativley the flatter (non-mountain) sites, while A. Cyanophylla appeared to favour relativly the mountain sites. All the species responded positively to greater rainfall and deep soil, but they differed in where they were most likely to be successful. Environmental factors such as climate, terrain and soil are the main determinants of species distribution in the study area, in addition to their impact on the growth of the main trees. There appeared not to be any relationship between biodiversity and whether the main trees were native or exotic, and only P. halepensis showed any negative effect on the abundance of shrubs. There was greater diversity of trees and shrubs generally at the younger sites than the old sites. The present study emphasises the current mismanagement of planted forests, particularly with overgrazing contributing to desertification, through preventing tree growth and eliminating most sapling regeneration. This study concludes by making recommendations for more effective choice of tree species to plant, and for subsequent management to improve afforestation programmes in the Jabal Akhdar area. / The Libyan Higher Education Ministry

Forestry and the wood-based sector provide increasing contributions to the national and rural economy development. Tree plantations serve as a business opportunity to secure the livelihood of thousands of small-scale timber producer households in several tropical countries. Given that forest land and the timber production it supports is limited, sustainable management of forest-based resources including timber is required. By integrating the value chain and livelihood analysis framework, this study investigates the value chains and impacts on rural livelihoods of commercial Acacia hybrid timber in central Vietnam. Besides that, scenario analysis is applied with a view to proposing the development pathways of the timber value chains and to providing improved information for developing the plantation policy in Vietnam at large. The empirical analysis employs a case study research design to examine the transition towards higher value uses of timber resources, thereby exploring the performance of woodchip, non-FSC furniture and FSC-certified furniture value chains in Thua Thien Hue province. Furthermore, two production areas named Nam Dong and Phu Loc districts are selected as embedded cases to examine the rural development potentials of Acacia hybrid timber production and commercialization. A mix-method approach, including both qualitative such as review and analysis of secondary data and key informant interviews, and quantitative data collection methods such as producer household surveys are applied to gather primary and secondary data. Diverse qualitative and quantitative analyses including content analysis, value chain analysis, livelihood analysis, and scenario analysis are also utilized corresponding to the specific research objectives. The macro-level analysis reveals the strategic responses of Asian wood-based firms to the global economy, particularly in terms of geographical scope, governance, cooperation, and overall performance. In addition, a literature review points out the potential impacts of Asian timber VCs on the environment and livelihoods. While timber product commercialization generates benefits to the value chain actors, unsustainable forest management leads to diverse negative environmental effects. The findings demonstrate considerable knowledge gaps and call for broader geographic coverage, as well as more transparent and quantitative assessments. To deepen the understanding on timber VCs, further research efforts should scrutinize the origins, functions, operations, and interactions of firms in these chains, and incorporate environmental and social aspects. The meso- and micro-level analysis exposes the structure of Acacia hybrid timber value chains which are shaped by various socio-economic, political, and environmental conditions. All three analyzed timber value chains are buyer-driven, led by processing and exporting companies in the downstream node of chains. At the upstream node, small-scale timber producers are normally less organized and lack market access. Timber production and commercialization provide profitable business activities to timber producers, traders, and processing and exporting companies. From a chain perspective, the woodchip value chain is financially profitable. However, its contribution to the national economy is the least. In contrast, the FSC-certified furniture value chain contributes fundamentally to economic development. The micro-level analysis indicates the difference regarding the socio-economic features, resource access, and management of producer households between the two analyzed districts. Relevant findings also indicate the importance of Acacia hybrid woodlots in the current livelihood system. However, more wealthy households benefit more from the Acacia hybrid timber income, especially in a well-developed market. Timber production and commercialization contribute to rural poverty reduction. Nevertheless, it is the main driver of the overall income inequality in both districts. Results from the literature review and empirical study support to conceptualize and evaluate the three development scenarios, displaying different levels of forest transition interventions and reactions of key actors in the chains. Under the current situation, a fast transition model with strict plantation control is not advisable for timber value chains’ stakeholders, especially those who operate on the ground. A slow transition scenario with a co-management model, instead, serves as a suitable development pathway. To improve the current management system, this study implies five management strategies, including (i) adaptive management; (ii) multi-stakeholder cooperation; (iii) target interventions; (iv) collaborative management and (v) integrated planning. The study can be of interest for further policy interventions focusing on sustainable reforestation and livelihood development in Vietnam. The approach of transition towards high added value products can further be applied in other comparable contextual cases searching for sustainable utilization of timber and forest-based products at large. Theoretically, the thesis highlights that sustainable management of forest-based products will not be obtained unless the related economic, social, and environmental aspects are considered in conjunction. These conditions are driven by several factors, such as national policy frame and market condition. Therefore, it is crucial to understand the interrelations within the economic-socio-ecological system to achieve long-term development targets. / Die Forstwirtschaft und der holzverarbeitende Sektor leisten einen wachsenden Beitrag zur nationalen und ländlichen Wirtschaftsentwicklung. Baumplantagen dienen Tausenden von kleinen Holzproduzentenhaushalten in vielen tropischen Ländern als Geschäftsmöglichkeit, um ihren Lebensunterhalt zu sichern. Da die Waldflächen und die darauf gestützte Holzproduktion begrenzt sind, ist eine nachhaltige Bewirtschaftung der waldbasierten Ressourcen, einschließlich Holz, erforderlich. Diese Studie untersucht die Wertschöpfungsketten und die Auswirkungen von kommerziellem Akazien-Hybridholz auf den Lebensunterhalt der ländlichen Bevölkerung in Zentralvietnam durch Integration von Wertschöpfungsketten- und Lebensunterhaltsanalysen. Außerdem wird eine Szenarioanalyse durchgeführt, um Entwicklungswege für die Holzwertschöpfungsketten vorzuschlagen und bessere Informationen für die Entwicklung der Plantagenpolitik in Vietnam insgesamt bereitzustellen. Die empirische Analyse verwendet ein Fallstudien-Forschungsdesign, um den Übergang zu höherwertigen Nutzungen von Holzressourcen zu untersuchen und dabei die Leistung von Wertschöpfungsketten für Hackschnitzel, nicht FSC-zertifizierte Möbel und FSC-zertifizierte Möbel in der Provinz Thua Thien Hue zu analysieren. Darüber hinaus werden zwei Produktionsgebiete, die Distrikte Nam Dong und Phu Loc, als Fallbeispiele ausgewählt, um die ländlichen Entwicklungspotenziale der Akazien-Hybridholzproduktion und -vermarktung zu untersuchen. Um Primär- und Sekundärdaten zu sammeln wird ein Methodenmix aus qualitativen Methoden, wie der Sichtung und Analyse von Sekundärdaten und der Befragung von Schlüsselinformanten, sowie quantitativen Datenerhebungsmethoden, wie der Befragung von Produzentenhaushalten, verwendet. Außerdem werden diverse qualitative und quantitative Analysen wie Inhaltsanalyse, Wertschöpfungskettenanalyse, Lebensunterhaltsanalyse und Szenarioanalyse entsprechend den spezifischen Forschungszielen eingesetzt. Die Analyse auf der Makroebene zeigt die strategischen Reaktionen der asiatischen Holzfirmen auf die globale Wirtschaft, insbesondere in Bezug auf geografische Reichweite, Governance, Kooperation und Gesamtleistung. Darüber hinaus zeigt eine Literaturübersicht die potenziellen Auswirkungen asiatischer Holzwertschöpfungsketten auf die Umwelt und die Lebensgrundlagen der lokalen Bevölkerung auf. Während die Kommerzialisierung von Holzprodukten Vorteile für die Akteure der Wertschöpfungskette mit sich bringt, führt eine nicht nachhaltige Waldbewirtschaftung zu diversen negativen Umwelteffekten. Die Ergebnisse zeigen erhebliche Wissenslücken auf und fordern eine breitere geografische Abdeckung sowie transparentere und quantitativere Bewertungen. Um das Verständnis von Holz-Wertschöpfungsketten zu vertiefen, sollten weitere Forschungsarbeiten die Ursprünge, Funktionen, Abläufe und Interaktionen von Unternehmen in diesen Ketten untersuchen und dabei ökologische und soziale Aspekte mit einbeziehen. Die Analyse auf der Meso- und Mikroebene legt die Struktur der Akazien-Hybridholz-Wertschöpfungsketten offen, welche von verschiedenen sozioökonomischen, politischen und ökologischen Bedingungen geprägt sind. Alle drei analysierten Holzwertschöpfungsketten sind käufergesteuert, angeführt von Verarbeitungs- und Exportunternehmen im nachgelagerten Knotenpunkt der Ketten. Am vorgelagerten Knotenpunkt sind die kleinen Holzproduzenten in der Regel weniger organisiert und haben keinen Marktzugang. Die Holzproduktion und -vermarktung bieten profitable Geschäftsaktivitäten für Holzproduzenten, Händler sowie Verarbeitungs- und Exportunternehmen. Aus der Kettenperspektive ist die Wertschöpfungskette Hackschnitzel finanziell profitabel. Ihr Beitrag zur Volkswirtschaft ist jedoch der geringste. Im Gegensatz dazu trägt die FSC-zertifizierte Möbel-Wertschöpfungskette grundlegend zur wirtschaftlichen Entwicklung bei. Die Analyse auf der Mikroebene zeigt die Unterschiede zwischen den beiden analysierten Distrikten in Bezug auf die sozioökonomischen Merkmale, den Ressourcenzugang und das Management der Produzentenhaushalte. Relevante Ergebnisse weisen auch auf die Bedeutung von Akazien-Hybridholzplantagen im derzeitigen Lebensunterhaltssystem hin. Allerdings profitieren wohlhabendere Haushalte mehr von den Einnahmen durch Akazien-Hybridholz, insbesondere bei einem gut entwickelten Markt. Holzproduktion und Kommerzialisierung tragen zur ländlichen Armutsbekämpfung bei, dennoch ist sie der ausschlaggebende Kraft für die allgemeine Einkommensungleichheit in beiden Distrikten. Die Ergebnisse der Literaturrecherche und der empirischen Studie helfen dabei, die drei Entwicklungsszenarien zu konzipieren und zu bewerten, die unterschiedliche Ebenen der Waldumwandlungsmaßnahmen und Reaktionen der Hauptakteure in den Ketten darstellen. In der aktuellen Situation ist ein schnelles Übergangsmodell mit strikter Kontrolle der Plantagen für die Akteure der Holzwertschöpfungsketten nicht ratsam, insbesondere für diejenigen, die vor Ort tätig sind. Ein langsames Übergangsszenario mit einem Co-Management-Modell dient stattdessen als geeigneter Entwicklungspfad. Um das derzeitige Managementsystem zu verbessern, schlägt diese Studie fünf Managementstrategien vor, darunter (i) adaptives Management, (ii) Zusammenarbeit mehrerer Interessengruppen, (iii) gezielte Interventionen, (iv) kooperatives Management und (v) integrierte Planung. Die Studie kann für weitere politische Interventionen von Interesse sein, welche sich auf eine nachhaltige Wiederaufforstung und die Entwicklung der Lebensgrundlagen in Vietnam konzentrieren. Der Ansatz des Übergangs zu Produkten mit hoher Wertschöpfung kann auch in anderen vergleichbaren Fällen angewandt werden, in denen eine nachhaltige Nutzung von Holz- und Forstprodukten im Allgemeinen angestrebt wird. Theoretisch unterstreicht die Arbeit, dass eine nachhaltige Bewirtschaftung von Forstprodukten nur dann erreicht werden kann, wenn die damit verbundenen wirtschaftlichen, sozialen und ökologischen Aspekte in Verbindung betrachtet werden. Diese Bedingungen werden von verschiedenen Faktoren beeinflusst, wie z.B. dem nationalen politischen Rahmen und den Marktbedingungen. Daher ist es entscheidend, die Zusammenhänge innerhalb des ökonomisch-sozio-ökologischen Systems zu verstehen, um langfristige Entwicklungsziele zu erreichen.

The rapid demand for wood products globally has put pressure on natural forests. Therefore, global efforts are now being directed toward establishing plantation forests to fill the wood supply gap while reducing the pressure on natural forests. This study conceptualized the socio-economic contribution of large-scale plantation forests to adjacent rural communities in the Northern Province of Sierra Leone based on the local perceptions of 125 households interviewed during data collection. To complement the household survey data, two forest-plantation experts were interviewed. The study found that local communities mainly benefit from plantation forestry through employment, improved road conditions, and water well constructions. However, the delivery of these benefits differed among the communities depending on the spatial distance from the plantation forestry central office. Benefits related to improvements in road conditions were perceived higher in the more far away communities. The trend is similar for the perception of benefits from plantation forestry activities: the farthest community with limited opportunities for alternative livelihood options appreciated the plantation forestry benefits highly and as fairly distributed. The results further revealed that perceived benefits from the plantation forestry industry, specifically employment and income, were rather unevenly distributed because the elites were able to capture more benefits than the others. These people were also identified to be influential in the distribution of benefits from the plantation industry. It is suggested that the plantation industry makes a conscious effort to extend the delivery of benefits to more community members regardless of their landholding, social status, or education level to ensure equal access to employment and land lease income, as well as CSR benefits.

Planting density and genotype have close relationship with the water relations in plants. The scenario of increased occurrence of extreme weather events and the change of Eucalyptus forest plantations to high water deficit regions, led us to the three key questions of this study: (1) What is the relationship between planting density and the potential water stress? (2) The planting spacing interferes the water use efficiency (WUE), i.e. the amount of biomass produced by the amount of water transpired? (3) Can the planting density change the soil water balance (BHS)? To develop this work, we settled a field trial in Mogi Guacu, SP, in February 2012. We planted four genetic material (Eucalyptus grandis x E.urophylla1 {Urograndis1}, Eucalyptus grandis x E.urophylla2, E.urophylla and E.grandis x E.camaldulensis {Grancam}) with different levels of tolerance to drought and four planting spacings (3.4, 7.0, 10.5 and 16.9 m2 plant-1, which correspond to densities of 2,949 , 1,424 and 1,028 and 591 plants ha-1). In Chapter 1, we evaluated the leaf water potential (representing potential water stress) of the four clones for 1 year, between 1.5 and 2.5 years. Regardless of the genetic material, the higher the wood productivity, the greater the leaf water potential. The denser planting (2,949 plants ha-1) stands generated 39% more wood, however, water stress potential reached up to 33% higher than the least dense planting (591 plants ha-1). In the second chapter, during the same period, we evaluated the efficiency of water use, which did not vary according to the change of planting density, but showed differences between genotypes with US 2.3, 2.2 and 1, 5 g L-1 to Urograndis, Urophylla and Grancam, respectively, at a density of 1,424 plants ha-1. Finally, the third chapter evaluated for two years, between 1.7 and 3.7 years, transpiration (T), soil evaporation (Es) and canopy interception (Ei), which together made up evapotranspiration (ET). Subtraction of precipitation (P) per ET resulted in soil water balance (SWB). The SWB was positive or near zero for the two clones evaluated (Urograndis1 and Grancam) when planting density was less than or equal to 1,028 trees ha-1. In the denser planting, the balance was -25%. These studies show that: a higher wood growth results in a higher potential drought stress, generating a clear trade-off between production and survival of trees. However, the detailed study of genetic materials fall under that there are increasing opportunities in water use efficiency, though without the increase in water use, bringing a greater share of water in the watershed scale. Finally, plantations above 1,028 ha-1 trees resulted in a negative soil water balance of -25% at the peak of growth. Together, this study reveals that spacing associated with genotypes can serve as tools in the search for balance between timber production and conservation of natural resources. / A densidade de plantio e o genótipo possuem estreita relação com as relações hídricas nas plantas. Sob um cenário de maior ocorrência de eventos climáticos extremos e do avanço dos plantios florestais de eucalipto para regiões de elevado déficit hídrico, elaboramos três perguntas-chave para esse estudo: (1) Qual a relação entre a densidade de plantio e o potencial estresse hídrico? (2) O espaçamento de plantio interfere na eficiência do uso da água (EUA), i.e., na quantidade de biomassa produzida pela quantidade de água transpirada? (3) Pode a densidade de plantio alterar o balanço hídrico do solo (BHS)? Para responder a essas questões, instalou-se um ensaio de campo em Mogi Guacu, SP, em fevereiro de 2012. Foram plantados quatro materiais genéticos (Eucalyptus grandis x E.urophylla1 {Urograndis1}, Eucalyptus grandis x E.urophylla2, E.urophylla e E.grandis x E.camaldulensis {Grancam}) com distintos níveis de tolerância à seca e quatro espaçamentos de plantio (3,4, 7,0, 10,5 e 16,9 m2 planta-1, que correspondem às densidades de 2.949, 1.424 e 1.028 e 591 plantas ha-1). No capítulo 1, avaliou-se o potencial hídrico foliar (representando o potencial estresse hídrico) dos quatro clones durante 1 ano, entre 1,5 e 2,5 anos. Independentemente do material genético, quanto maior a produtividade madeireira atingida, maior o potencial hídrico foliar. Os plantios mais adensados (2.949 plantas ha-1) geraram povoamentos 39% mais produtivos, no entanto, o potencial estresse hídrico chegou a atingir 33% acima do plantio menos adensado (591 plantas ha-1). No segundo capítulo, durante o mesmo período, avaliou-se a eficiência do uso da água, que não variou conforme a mudança de densidade de plantio, mas apresentou diferença entre os genótipos, com EUA de 2,3, 2,2 e 1,5 g L-1 para os clones Urograndis, Urophylla e Grancam, respectivamente, na densidade de 1.424 plantas ha-1. Por fim, o terceiro capítulo avaliou durante dois anos, entre 1,7 e 3,7 anos, a transpiração (T), evaporação do solo (Es) e interceptação de água pela copa (Ei), que somados compunham e evapotranspiração (ET). A subtração da precipitação (P) da ET resultou no balanço hídrico do solo (BHS). O BHS foi positivo ou próximo de zero para os dois clones avaliados (Urograndis1 e Grancam) quando a densidade de plantio foi inferior ou igual a 1.028 árvores ha-1. No plantio mais adensado, o balanço foi de -25%. Estes estudos demonstram que: a maior produtividade madeireira acarreta em maior potencial estresse hídrico, gerando um claro dilema entre a produção e a sobrevivência dos plantios. No entanto, o estudo detalhado dos materiais genéticos releva que há possibilidades de incremento na eficiência do uso da água sem que ocorra o aumento no uso da água, trazendo um maior compartilhamento da água na escala da microbacia. Por fim, plantios acima de 1.028 árvores ha-1 resultaram em um balanço hídrico do solo negativo médio de -25% no pico do crescimento. Em conjunto, o presente trabalho releva que o espaçamento associado a materiais genéticos específicos, podem servir como ferramenta na busca pelo equilíbrio entre a produção madeireira e a conservação de recursos naturais.

Planting density and genotype have close relationship with the water relations in plants. The scenario of increased occurrence of extreme weather events and the change of Eucalyptus forest plantations to high water deficit regions, led us to the three key questions of this study: (1) What is the relationship between planting density and the potential water stress? (2) The planting spacing interferes the water use efficiency (WUE), i.e. the amount of biomass produced by the amount of water transpired? (3) Can the planting density change the soil water balance (BHS)? To develop this work, we settled a field trial in Mogi Guacu, SP, in February 2012. We planted four genetic material (Eucalyptus grandis x E.urophylla1 {Urograndis1}, Eucalyptus grandis x E.urophylla2, E.urophylla and E.grandis x E.camaldulensis {Grancam}) with different levels of tolerance to drought and four planting spacings (3.4, 7.0, 10.5 and 16.9 m2 plant-1, which correspond to densities of 2,949 , 1,424 and 1,028 and 591 plants ha-1). In Chapter 1, we evaluated the leaf water potential (representing potential water stress) of the four clones for 1 year, between 1.5 and 2.5 years. Regardless of the genetic material, the higher the wood productivity, the greater the leaf water potential. The denser planting (2,949 plants ha-1) stands generated 39% more wood, however, water stress potential reached up to 33% higher than the least dense planting (591 plants ha-1). In the second chapter, during the same period, we evaluated the efficiency of water use, which did not vary according to the change of planting density, but showed differences between genotypes with US 2.3, 2.2 and 1, 5 g L-1 to Urograndis, Urophylla and Grancam, respectively, at a density of 1,424 plants ha-1. Finally, the third chapter evaluated for two years, between 1.7 and 3.7 years, transpiration (T), soil evaporation (Es) and canopy interception (Ei), which together made up evapotranspiration (ET). Subtraction of precipitation (P) per ET resulted in soil water balance (SWB). The SWB was positive or near zero for the two clones evaluated (Urograndis1 and Grancam) when planting density was less than or equal to 1,028 trees ha-1. In the denser planting, the balance was -25%. These studies show that: a higher wood growth results in a higher potential drought stress, generating a clear trade-off between production and survival of trees. However, the detailed study of genetic materials fall under that there are increasing opportunities in water use efficiency, though without the increase in water use, bringing a greater share of water in the watershed scale. Finally, plantations above 1,028 ha-1 trees resulted in a negative soil water balance of -25% at the peak of growth. Together, this study reveals that spacing associated with genotypes can serve as tools in the search for balance between timber production and conservation of natural resources. / A densidade de plantio e o genótipo possuem estreita relação com as relações hídricas nas plantas. Sob um cenário de maior ocorrência de eventos climáticos extremos e do avanço dos plantios florestais de eucalipto para regiões de elevado déficit hídrico, elaboramos três perguntas-chave para esse estudo: (1) Qual a relação entre a densidade de plantio e o potencial estresse hídrico? (2) O espaçamento de plantio interfere na eficiência do uso da água (EUA), i.e., na quantidade de biomassa produzida pela quantidade de água transpirada? (3) Pode a densidade de plantio alterar o balanço hídrico do solo (BHS)? Para responder a essas questões, instalou-se um ensaio de campo em Mogi Guacu, SP, em fevereiro de 2012. Foram plantados quatro materiais genéticos (Eucalyptus grandis x E.urophylla1 {Urograndis1}, Eucalyptus grandis x E.urophylla2, E.urophylla e E.grandis x E.camaldulensis {Grancam}) com distintos níveis de tolerância à seca e quatro espaçamentos de plantio (3,4, 7,0, 10,5 e 16,9 m2 planta-1, que correspondem às densidades de 2.949, 1.424 e 1.028 e 591 plantas ha-1). No capítulo 1, avaliou-se o potencial hídrico foliar (representando o potencial estresse hídrico) dos quatro clones durante 1 ano, entre 1,5 e 2,5 anos. Independentemente do material genético, quanto maior a produtividade madeireira atingida, maior o potencial hídrico foliar. Os plantios mais adensados (2.949 plantas ha-1) geraram povoamentos 39% mais produtivos, no entanto, o potencial estresse hídrico chegou a atingir 33% acima do plantio menos adensado (591 plantas ha-1). No segundo capítulo, durante o mesmo período, avaliou-se a eficiência do uso da água, que não variou conforme a mudança de densidade de plantio, mas apresentou diferença entre os genótipos, com EUA de 2,3, 2,2 e 1,5 g L-1 para os clones Urograndis, Urophylla e Grancam, respectivamente, na densidade de 1.424 plantas ha-1. Por fim, o terceiro capítulo avaliou durante dois anos, entre 1,7 e 3,7 anos, a transpiração (T), evaporação do solo (Es) e interceptação de água pela copa (Ei), que somados compunham e evapotranspiração (ET). A subtração da precipitação (P) da ET resultou no balanço hídrico do solo (BHS). O BHS foi positivo ou próximo de zero para os dois clones avaliados (Urograndis1 e Grancam) quando a densidade de plantio foi inferior ou igual a 1.028 árvores ha-1. No plantio mais adensado, o balanço foi de -25%. Estes estudos demonstram que: a maior produtividade madeireira acarreta em maior potencial estresse hídrico, gerando um claro dilema entre a produção e a sobrevivência dos plantios. No entanto, o estudo detalhado dos materiais genéticos releva que há possibilidades de incremento na eficiência do uso da água sem que ocorra o aumento no uso da água, trazendo um maior compartilhamento da água na escala da microbacia. Por fim, plantios acima de 1.028 árvores ha-1 resultaram em um balanço hídrico do solo negativo médio de -25% no pico do crescimento. Em conjunto, o presente trabalho releva que o espaçamento associado a materiais genéticos específicos, podem servir como ferramenta na busca pelo equilíbrio entre a produção madeireira e a conservação de recursos naturais.

Natural forests are characterised by great vegetation diversity and create habitats for a major part of Earth’s terrestrial organisms. Plantation forests, which are mainly composed of a few genera of fast-growing trees, constitute an increasing fraction of global forests, but they only partly compensate for loss of area, habitat and ecological functions in natural forests. Plantation forests established near natural forests can be expected to serve as buffers, but they seem to be relatively poor in invertebrate species and it is not clear why. This bachelor’s degree project aimed at establishing the ecological and edaphic factors that correlate with soil invertebrate diversity in dry upland forests and surrounding plantation forests in eastern Africa. Some aspects of the above-ground vegetation heterogeneity were investigated since this was assumed to influence the heterogeneity of the soil environment, which is considered as critical for soil biodiversity. The obtained knowledge may be valuable in conservation activities in East African forests, which are threatened by destruction, fragmentation and exotic species. The study area was Karura Forest, a dry upland forest in Nairobi, Kenya. Three different sites were investigated; a natural forest site characterized by the indigenous tree species Brachylaena huillensis and Croton megalocarpus, and two different plantation forest sites, characterized by the exotic species Cupressus lusitanica and Eucalyptus paniculata, respectively. For each forest type, six plots were visited. Soil invertebrates were extracted from collected soil and litter samples by sieving and Berlese-Tullgren funnels. The invertebrates were identified, and the taxonomic diversity calculated at the order level. The ecological and edaphic factors, measured or calculated for each plot, were tree species diversity, ratio of exotic tree species, vertical structure of trees, vegetation cover, vegetation density, litter quality, soil pH, soil temperature and soil moisture. One-way ANOVA was used to compare soil invertebrate diversity and other variables between different forest types. Akaike’s Information Criterion and Multiple Linear Regression were used to establish linear models with variables that could explain measured variations of the diversity. There was some evidence for higher soil invertebrate diversity in natural forests than in surrounding plantation forests. The abundance of soil invertebrates was also clearly higher in natural forests, which indicates that natural forests are more important than plantation forests for conservation of soil invertebrate populations. Soil invertebrate diversity (in terms of number of orders present) was found to be influenced by forest type and litter quality. The diversity was higher at places with high amounts of coarse litter, which here is considered as more heterogenous than fine litter. The dependence on forest type was partly a consequence of differences in soil pH since Eucalyptus trees lower soil pH and thereby also soil biodiversity. No relation to heterogeneity of above-ground vegetation was found. For future conservation activities in Karura Forest Reserve it is recommended to continue removing exotic plant species and replanting indigenous trees, to prioritize the removal of Eucalyptus trees before Cypress trees, to only remove a few trees at a time and to establish ground vegetation when doing so.