<p>Thesis submission for Caleb Kell</p>

As they are not only the home of many threatened species, but also one of the main actors in the global carbon cycle, peatlands are highly valuable ecosystems. Human disturbance, in particular drainage for forestry and agriculture, has substantially changed the state of the world’s peatlands and will continue to do so. Lowering the water table by drainage has many hydrological and biological effects, including an increased growth of trees and shrubs as well as reduced growth of the key peat moss genus Sphagnum, leading to peat degradation and release of carbon dioxide. The effects of drainage are sometimes used as predictions for how peatlands will respond to climate change, and undrained mires are thus expected to become more like drained ones in the future. The accuracy of that assumption has, to my knowledge, not been tested on a large scale. Here, I use data from two Swedish national monitoring programs to analyze how the vegetation on drained and undrained mires has changed in recent decades. The results showed an increased tree growth but a decreased establishment of new trees on both drained and undrained mires, implying that contrary to common belief there is no current large-scale afforestation of open mires in Sweden. Sphagnum had, surprisingly, increased on both drained and undrained mires, while other functional groups showed varying results. The tree growth rate was faster on drained mires, but in most other analyses the response to time did not differ depending on drainage regime. Thereby, this study found limited support for the hypothesis that undrained mires are becoming more like drained mires with climate change.

The estimation of afforestation reservation prices for small landowners in New Zealand has not been the subject of much research despite its importance in predicting future land use. Reservation prices for planting represent the minimum payment a landowner must receive before converting land from agriculture to forest. A survey of 728 landowners from every region of New Zealand who own between 20 and 200 hectares of forest as well as other unplanted land used for agriculture were surveyed about forestland, forest land owner demographics, ownership objectives, silviculture and reservation prices. In this study, reservation price strategies were investigated by offering hypothetical annual and one-time payments for converting land from agriculture to forestry. From this survey, the average one-time payment a landowner would be willing to accept to convert a hectare of land from agriculture to forestry was $3,554 and the average annual payment to convert a hectare of land was $360. The key factors influencing the reservation price were; whether or not the landowner lived on the property, if one of the ownership objectives was income from carbon, the primary agricultural enterprise and total household income. An implied discount rate was calculated for each landowner and excluding those who would not accept any payment the average after-tax discount rate was 9.7%. Small landowners indicated that their primary reason for owning plantation forest was income from timber with very few landowners using their forest land for recreation. The median farm size was 400 hectares and the median forest plantation was 37 hectares. Planting of radiata pine peaked in 1994 and 1995 with more radiata pine planted in 1994 than in all the years from 2000-2009. Most landowners are performing some type of silviculture in their forests. Ninety percent of landowners are pruning in the current rotation while only 61% plan to prune in the future. Only 26% of landowners have engaged in any commercial harvesting in the past ten years but as their current rotation matures 71% plan to replant on the same site. A majority of respondents thought the situation for forest landowners was getting better. Understanding the reservation price strategies of landowners is important for predicting future land use patterns and recognizing how close landowners are to converting land. The ownership objectives of landowners and the replanting decisions they make are critical for future timber supply. The results of this study can assist in the development of forest establishment incentive programmes. Better information about landowner characteristics will result in enhanced decision-making for the timber industry and the government in New Zealand.

Les forêts d’Écouves (Basse-Normandie) et de Slieveanorra (Irlande du Nord) sont ponctuées de milieux tourbeux. La thèse retrace les trajectoires historiques de ces deux sites, aux changements paradigmatiques synchrones et en étudie, par enquêtes, les représentations et la gestion.Les résultats montrent le poids du sociosystème dans la naissance et le devenir des tourbières intraforestières, mais les systèmes de représentations et pratiques de gestion de ces turfi-sylvosystèmes diffèrent.De la moitié du 19e siècle au milieu du 20e, le bois de Goult était un taillis de feuillus dégradé, ponctué de milieux tourbeux, dévalorisés, voire dangereux. Des tourbières de couverture et des landes tourbeuses pâturées et exploitées extensivement par les paysans locaux caractérisaient les milieux occupés par l’actuelle forêt de Slieveanorra.Durant la période 1950-1980, le « tout boisement » valorisa ces terres marginales par la sylviculture de bois exotiques. Le bois de Goult, domanialisé en 1955, fut reboisé et les zones humides, plantées en épicéas de Sitka (Picea Sitchensis). La forêt de Slieveanorra fut créée de toutes pièces, à partir de 1955 aussi, avec l’acquisition des terres par le ministère de l’Agriculture.À la fin des années 1980, des mesures de gestion conservatoire se multiplient. Interventionnistes en forêt d’Écouves, elles sont plus légères en forêt de Slieveanorra où l’on protège et gère a minima les espaces non boisés. Les Normands, influencés par la communication du PNR Normandie-Maine et de l’ONF, connaissent bien le milieu-tourbière et ses attraits naturalistes tandis que les Nord-irlandais connaissent mieux le produit-tourbe, qu’ils craignent de voir disparaître. / Écouves (Basse-Normandie, France) and Slieveanorra (Northern Ireland) forests are punctuated with peatlands. The thesis relates historical trajectories of these two sites, which experienced synchronic paradigmatic changes, and conducts surveys on representations and management.Results show that the sociosystem weights on the birth and future of intraforest peatlands, but representations and management practices of these turfi-sylvosystems are different.From the beginning of the 19th century to the middle of the 20th, the wood of Goult was a ruined broadleaved coppice, punctuated with depreciate, indeed dangerous, peatlands. The current Slieveanorra forest was occupied with extensively grazed and exploited blanket bogs and peaty heaths.Between 1950 and 1980, the “all-afforestation” policy developed these marginal lands with exotic coniferous trees plantations. The wood of Goult, state-owned in 1955, was replanted and peatlands were afforested with Sitka Spruce (Picea sitchensis). Slieveanorra forest was built, from 1955 too, with land purchasing by the department of Agriculture.Since the end of the 1980’s, conservation measures have grown in number. In the forest of Écouves, they are interventionists whereas in Slieveanorra forest, they are lighter; open spaces are protected and managed at least. Normans are influenced by the PNR Normandie-Maine and ONF communication and know the environment-bog and his naturalists qualities well whereas Northern Irish know the product-turf better, which they don’t want to see disappear.

A evolução da forma urbana adequada ao seu contexto climático é determinante para a qualidade ambiental dos espaços abertos. Porém, em diversas cidades o crescimento urbano acelerado ocorre quase sem nenhum controle ou planejamento. Esse descontrole é apontado como causa de prejuízos ao ambiente natural e construído, entre eles, o desconforto térmico nos espaços abertos. No Brasil, o Plano Diretor é o instrumento dos governos municipais que regula o desenho urbano; no entanto, nota-se um distanciamento entre os aspectos ambientais e a formulação dos planos e leis municipais. A cidade de Umuarama, no noroeste do Paraná, tem assistido a um intenso crescimento urbano, porém, ainda há na cidade uma flexibilidade para a gestão da forma urbana. Atualmente, está em fase de aprovação o novo Plano Diretor Municipal, que propõe a ampliação da área urbana onde é permitida a verticalização, e o Plano Municipal de Arborização Urbana, que busca promover o controle e o aumento da arborização urbana. Face ao proposto pelos planos, essa pesquisa tem como objetivo principal verificar as tendências de estresse térmico no nível do pedestre em futuros cenários de cânions urbanos na área central de Umuarama. O cânion urbano, referente ao espaço conformado pela via e edifícios adjacentes, foi adotado como objeto de estudo por se constituir na menor unidade microclimática urbana e no principal espaço aberto de uso público. A metodologia aplicada se baseia em levantamento de dados em campo; simulação de diferentes cenários de configuração urbana através de modelagem microclimática com o programa ENVI-met, para situação de verão e inverno; e aplicação do índice de conforto térmico Temperatura Fisiológica Equivalente - PET. Os resultados demonstraram que diferentes combinações dos parâmetros da forma urbana, especificamente, da geometria do cânion urbano e arborização presente no seu interior, resultam em tendências diversas de estresse térmico para o pedestre. Os maiores níveis de estresse térmico no nível do pedestre foram observados no período diurno, em situação de verão; esses níveis tendem a ser menores com o aumento da relação H/W e da arborização no interior dos cânions urbanos. Além disso, verificou-se menor amplitude térmica em cânions com maior cobertura verde. Em cânions urbanos com orientação N-S, o aumento da cobertura verde no interior do cânion urbano foi mais importante para a redução do índice PET do que em cânions com orientação L-O; por outro lado, nesses cânions com orientação L-O, o aumento da relação H/W foi mais representativo para minimizar o PET. A compreensão do comportamento do PET nos diversos cenários demonstrou que novas configurações da forma urbana são compatíveis com a qualidade ambiental dos espaços abertos desde que aplicadas estratégias do desenho urbano climaticamente orientado. Ao final, com base nos resultados, foram traçadas recomendações relacionadas à geometria e cobertura verde das vias urbanas a favor do conforto térmico dos usuários desses espaços. / The appropriate evolution of urban form for your climate context is determinant to open spaces environmental quality. However, it is observed that in several cities the accelerated urban growth occurs almost without any control or planning. This lack of control is pointed as the cause of damage to the built and natural environment, including the thermal discomfort in open spaces. In Brazil, the Master Plan is the instrument of the municipal governments that regulates the urban design; however, there is a gap between environmental aspects and the formulation of plans and municipal laws. The city of Umuarama in the Northwest of Paraná, has seen an intense urban growth, however, there is still a flexibility to the management of urban form. Actually, the new municipal Master Plan is in the aproval phase, it proposes the expansion of the urban area where verticalization is permitted, and the municipal urban afforestation plan, that seeks to promote and control the increase of urban afforestation. In view of proposed plans, this research has as main objective to verify the trends of thermal stress in the pedestrian\'s level in future scenarios of urban canyons in the central area of Umuarama. The urban canyon, referring to the space formed by the via and adjacent buildings, was adopted as object of study because it is the smallest unit microclimatic and the main urban open space for public use. The methodology applied is based on in loco data collection; simulation of different scenarios of urban setting through microclimatic modeling with the ENVI-met program, for summer and winter condition; and application of thermal comfort index Physiological Equivalent Temperature - PET. The results showed that different combinations of the urban form parameters, specifically, the urban canyon geometry and afforestation present in your interior, result in various trends of thermal stress to the pedestrian. The highest levels of thermal stress in the pedestrian level were observed during the day, in summer; these levels trend to be smaller with increasing H/W ratio and afforestation in urban canyons. In addition, there has been less thermal amplitude in canyons with more green coverage. In urban canyons with N-S orientation, increasing the green coverage inside the urban canyon was more important for the reduction of the PET index than in the canyons with L-O orientation; on the other hand, in those canyons with L-O orientation, increasing the H/W ratio was more representative to minimize the PET. Understanding PET behavior in different scenarios demonstrated that new urban form settings are compatible with the open spaces environmental quality since applied urban design strategies climatically guided. In the end, based on the results, were delineated recommendations related urban streets geometry and green coverage in favour of thermal comfort of the users of these spaces.

A influência benéfica de áreas verdes no conforto humano em áreas urbanas tem sido reconhecida por estudos de diferentes campos do conhecimento. A fim de verificar a relação existente do conforto humano com métricas de cobertura arbórea na cidade de Piracicaba/SP, foram dispostos 43 registradores higrotérmicos microprocessados durante 40 dias de coleta tanto na estação chuvosa e seca dos anos de (2015-2016), bem como uma estação meteorológica móvel, da marca Davis Vantage Vu, de modo a obter as variáveis de conforto humano relacionadas com a sensação térmica relatada pelos residentes. Para tanto, foram utilizados índices de avaliação de conforto térmico (UTCI - Universal Thermal Comfort Index) e (PET- Physiologically Equivalent Temperature) obtidos por meio do modelo RayMan Pro. Questionários aplicados aos residentes das áreas de estudo possibilitaram verificar se os resultados obtidos por meio dos índices UTCI e PET correspondiam à real sensação de conforto térmico relatada pelos entrevistados. O tecido urbano foi caracterizado por meio de classificação supervisionada realizada pelo software MultiSpec feita a partir de imagem multiespectral de alta resolução do satélite WorldView 2 no ano de 2011 para a cidade de Piracicaba/SP. Buffers (áreas de influências dos pontos analisados) de 10, 20 e 500 metros foram gerados ao redor dos pontos de estudo pelo software Quantum Gis, v. 2.4, possibilitando correlacionar a porcentagem de cobertura com os dados microclimáticos obtidos com o objetivo de se obter modelos estatísticos que conseguissem predizer o quanto de cobertura arbórea seria necessária para a diminuição de uma dada temperatura média urbana. Foram obtidos valores de Índice de Floresta Urbana (IFU) para os bairros analisados. As estações Davis Vantage Vu foi calibrada com a da ESALQ/USP no intuito de que os dados climáticos tivessem maior veracidade e estivessem condizentes com a sensação térmica relatada pelos entrevistados; além disso, foram feitos ajustes dos dias de coleta na tentativa de padronizá-los. Dentre os resultados obtidos, os valores de IFUs corresponderam aos bairros mais confortáveis. Verificou-se, também, maior correlação dos dados microclimáticos dos 43 pontos com o uso e ocupação do solo para buffers de 20 metros na estação chuvosa e buffers de 500 metros na estação seca. Sendo assim, modelos estatísticos serviram para afirmar que aproximadamente 57% (R2 = 0,57) do valor da temperatura média urbana foi explicado pela quantidade de cobertura arbórea na estação chuvosa e 60% (R2 = 0,60) do valor da temperatura média urbana foi explicado pela quantidade de cobertura arbórea na estação seca. Como resultado precípuo desta pesquisa, os modelos gerados permitiram responder uma resposta ainda inexistente: a quantidade de árvores necessária para diminuir o calor excessivo em determinada área urbana, algo altamente desejável em tempos de alterações climáticas e com cidades em crise de abastecimento de água e energia elétrica. Constatou-se, portanto, que para diminuir 1°C da temperatura média urbana é necessário acrescentar 14,31% de cobertura arbórea na estação seca e 27,70% na estação chuvosa no município de Piracicaba/SP. Como avanço nesta pesquisa e inédito para a cidade, os modelos estatísticos permitem ser adotados por outras cidades com a finalidade de proporcionar maior conforto ambiental urbano para a população e inspecionar e avaliar a situação da arborização urbana nas cidades brasileiras. / The beneficial influence of green areas on human comfort in urban areas has been recognized by studies from different fields of knowledge. In order to verify the existing relationship of human comfort with tree cover metrics in the city of Piracicaba/SP, 43 microprocessed hygrothermal registers were arranged during 40 days of collection in both rainy and dry season of the years 2015-2016, as well as a mobile weather station of the Davis Vantage Vu brand, in order to obtain the human comfort variables related to the thermal sensation reported by residents. The thermal comfort index (UTCI) and PET (Physiologically Equivalent Temperature) values were obtained using the RayMan Pro model. Questionnaires applied to the residents of the study areas made it possible to verify if the results obtained through the UTCI and PET index corresponded to the real sensation of thermal comfort reported by the interviewees. The urban area was characterized by supervised classification performed by MultiSpec software made from a high-resolution multispectral image of WorldView 2 satellite in 2011 for the city of Piracicaba/SP. Buffers (areas of influence of the analyzed points) of 10, 20 and 500 meters were generated around the points of study by Quantum Gis software, v. 2.4, making it possible to correlate the percentage of coverage with the microclimatic data, obtained with the objective of make statistical models that could predict how much tree cover would be necessary for the decrease of a given urban temperature average. Urban Forest Index (IFU) values were obtained for the neighborhoods analyzed. The Davis Vantage Vu stations were calibrated with ESALQ/USP stations in order to make the climate data more accurate and consistent with the thermal sensation reported by the interviewees; In addition, adjustments of collection days were made in an attempt to standardize them. Among the results obtained, IFU values corresponded to the most comfortable neighborhoods. It was also verified a higher correlation of the microclimatic data of the 43 points with the use and occupation of the soil for buffers of 20 meters in the rainy season and buffers of 500 meters in the dry season. Thus, statistical models served to assert that approximately 57% (R&sup2; = 0.57) of the mean urban temperature was explained by the amount of tree cover in the rainy season and 60% (R&sup2; = 0.60) of the average temperature was explained by the amount of tree cover in the dry season. As a result of this research, the models generated allowed to respond to a still non-existent response: the amount of trees needed to reduce excessive heat in a given urban area, something highly desirable in times of climate change and with cities in crisis of water and energy supply power. It was verified, therefore, that to reduce 1&deg;C of the urban average temperature it is necessary to add 14.31% of tree cover in the dry season and 27.70% in the rainy season in the city of Piracicaba/SP. As an advance in this research and unprecedented for the city, the statistical models allow adoption by other cities with the purpose of providing greater urban environmental comfort for the population and to inspect and evaluate the situation of urban afforestation in Brazilian cities.

No description available.

Wald weist gegenüber anderen Landnutzungen meist die günstigeren Wasserrückhalteigenschaften auf. Diese sind jedoch begrenzt. Ob zusätzlicher Wald in einem Einzugsgebiet zur Reduktion eines Hochwassers führt, hängt ab von der Vorwitterung, den Eigenschaften des Bodens, auf dem die Aufforstung etabliert wurde, Dauer und Intensität des hochwasserauslösenden Niederschlagsereignisses und Lage und Größe der Aufforstungsfläche im betrachteten Einzugsgebiet. Weiterhin spielt das Waldmanagement, welches in dieser Arbeit nur am Rande diskutiert wurde, eine bedeutende Rolle. Bei der Umwandlung einer anderen Landnutzung in Wald sind noch nicht alle Prozesse, die den Wasserrückhalt betreffen, ausreichend untersucht und beschrieben. Dies gilt besonders für die Änderungen in der hydraulischen Architektur der Böden. Es wurde dargestellt, dass aufwachsende Wälder schon nach wenigen Jahren die Porenverteilung besonders in den oberen Bodenhorizonten verändern. Obwohl experimentelle Felduntersuchungen besonders durch die Suche nach geeigneten Teststandorten schwierig sind, wären weitere Messergebnisse von anderen Böden mit anderen Baumarten hier wünschenswert. Eine modellhafte Beschreibung einer Landnutzungsänderung hin zu Wald in Bezug auf den Hochwasserrückhalt ist demnach mit hohen Unsicherheiten behaftet. Modelle bleiben dennoch die einzige Möglichkeit, Auswirkungen von Landnutzungsänderungen mit vertretbarem Aufwand quantifizierend abzuschätzen. Allgemein gilt bei der Anwendung hydrologischer Modelle zur Prognose von Auswirkungen veränderter Landnutzungen, dass bislang wenig quantitativ verwertbares Wissen über Änderungen im Boden besteht. Weder der Zielzustand noch der Verlauf der Transformation können hier sicher prognostiziert werden. Vernachlässigt man aber solche Prozesse, dürfen bei einer Ergebnisdiskussion auch nur die berücksichtigten Prozesse angeführt werden. Die Weiterentwicklung der Modelle mit gezielter paralleler Datenerhebung ist hier unabdingbar. Die zunehmenden Fragestellungen hinsichtlich veränderter Landnutzungssysteme erfordern auch innovative Formen der Parametrisierung und Kalibrierung der Modelle. Der zunehmende Grad an Prozessabbildungen in den Modellen darf die Parametrisierbarkeit nicht unmöglich machen. Eine adäquate Prozessabbildung ist jedoch der Schlüssel für die szenarienfähige Modellierung. Die Kommunikation der Ergebnisse muss deshalb eine hohe Transparenz mit der Benennung aller bekannten Unsicherheiten aufweisen, da Entscheidungen in der Landnutzung Konsequenzen über sehr lange Zeiträume hinweg nach sich ziehen. Die qualifizierte Prognose von Landnutzungsänderungen ist eine disziplinübergreifende Aufgabe. Hier wirken soziologische, ökonomische und ökologische Prozesse zusammen, deren Resultat die zukünftige Landnutzung ist. Eine weitere wichtige Schlussfolgerung der vorliegenden Arbeit ist daher, dass für die Umsetzung von Maßnahmen, zur Erhöhung des Wasserrückhaltes, wie hier der Aufforstung, ein breiter wissenschaftlicher und gesellschaftlicher Konsens herrschen muss. Es braucht integrierte Ansätze zur disziplinübergreifenden Beschreibung von Auswirkungen veränderter Landnutzung. Trotz aller Unsicherheiten bei der wissenschaftlichen Beweisführung wird erwartet, dass bis zur Umsetzung der Hochwasserrisiko-Managementpläne „nachhaltige Flächennutzungen“ zur „Verbesserung des Wasserrückhaltes“ definiert sind. Besonders für die politischen Entscheidungsträger ist zur Entwicklung geeigneter Steuerelemente festzuhalten, das Hochwasserschutzmaßnahmen in der Fläche ihre hauptsächliche Wirkung nicht am Punkt der Implementierung entfalten, sondern erst weiter flussabwärts. Daher sind die bisherigen Förderinstrumente der EU-Agrarflächenförderung für den Hochwasserschutz in der Fläche nahezu nicht anwendbar. Es gilt hier sektorales Denken zu überwinden. Unterschiedliche Ansprüche an Landnutzungssysteme sind durch Lösungsansätze auszubalancieren, die die unterschiedlichen Landschaftsfunktionen berücksichtigen, von denen Wasserrückhalt ein Teil sein kann. Andere Schutzziele wie Naturschutz, Bodenschutz, Ziele der Wasserrahmenrichtlinie, Fragen eines ästhetischen Landschaftsbildes und nicht zuletzt Fragen der wirtschaftlichen Ansprüche an die einzelnen Flächen spielen hier eine wichtige Rolle. Bei der Entwicklung begründeter Zukunftsszenarien ist diese transdisziplinäre Herangehensweise unbedingt zu empfehlen. Hochwasserschutz kann aber nicht die Aufgabe haben, Hochwasserereignisse vollkommen auszuschließen. Schon heute ist bekannt, dass das Ausbleiben kleiner und mittlerer Hochwässer ökologische Konsequenzen hat. Vielmehr könnte in Gebieten, wie dem hier untersuchten, eine Erhöhung des Waldanteils dazu beitragen, die anthropogenen Störungen zu reduzieren und den Wasserrückhalt dahingehend zu erhöhen, dass hochwasserverschärfende Eingriffe in den Einzugsgebieten zurückgebaut werden. / Forests show, compared to other land uses, in many cases good water retention potential. This is however limited. Whether additional forest area in a catchment leads to a reduction of flooding depends on the pre-event atmospheric conditions, the soil characteristics at the afforested site, the duration and intensity of the rain storm event, and location and size of the afforested area. Further, the forest management, which is only briefly discussed in this thesis, plays an important role. Many water retention related processes occurring during the transformation of a landuse into forest are not yet sufficiently investigated an described. This applies especially to the changes in the hydraulic architecture of the soil. It was shown that after a few years growing forests have already changed the pore distribution, especially in the upper soil horizons. However, further research under different soil and tree type would be desirable. Therefore, a model-based description of land use change towards forest with regard to flood retention comprises uncertainties which should be taken into consideration. Nevertheless, models are the only possibility to assess land use change effects with justifiable expenditure. In general, the application of hydrological models comprised sparse useful information about changes in the soil due to a changed land use. Neither the target state nor the progression of the transformation can be predicted with certainty. Further development of models with parallel observations and data gathering is essential. With increasing number of questions regarding modified land use systems, a need arises for innovative forms of parameterisation and model calibration. The increasing degree of process mapping in models may make parameterability difficult, however, adequate process mapping is the key to scenario capable modelling. The communication of results must therefore include a high degree of transparency in the definition of all known uncertainties, because decisions have long lasting consequences. A qualified prediction of land use changes is a cross-disciplinary task. Ecological, economical, and sociological processes together form the future land use distribution. An important conclusion from this thesis is that the implementation of measures targeting increased water retention requires must result in a consensus with society and economics. Integrated approaches and transdisciplinary assessment of impacts of land use modifications are needed. Although, the uncertainties in model-based land use change assessment are high, there is a need for the definition of “sustainable land use” and “increase of water retention” for the flood risk management plans. Adapted land use as a component of integrated flood risk management has a major constraint: the benefits of water retention in the landscape are mostly not directly noticeable at the place where a measure is implemented. This is highly important for stakeholders and decision makers. However, given that most of the land available for afforestation is a private property, it may be necessary to provide subsidies to encourage landowners to increase the percentage of forested land. Competitive land use system requirements need to be balanced with approaches dealing with different landscape functions. Water retention is part of this functioning. Other protection aims like nature protection, soil protection, aims of the Water Framework Directive, aesthetic land use pattern but also the agrar-economic production play an important role. Well-founded future land use scenarios should use this transdisciplinary view. Finally, it is also important to keep in mind that floods belong to a healthy river runoff regime. Floods are an important part of the natural hydrological cycle, and therefore the goal of watershed management should not be to eliminate them entirely. Additional forest can help to re-establish the natural water retention potential in anthropogenically disturbed river basins and to decrease the human-made contribution to flood generation.

十年建設期間（1928-1937）國民政府曾大力推動造林事業，當時森林被認為具有防災、經營致富的作用，是建國要務之一。分析造林運動的原因，一方面由於經濟因素，各項建設展開，中國木材供應不足；一方面是環境因素，希望藉由造林減少水旱災，保護生命財產安全，經濟與環境考量相互影響之下促成。華北地區由於長期的農業開墾，在森林資源上甚為缺乏，故造林事業在華北有重要意義。事實上，華北許多人工林地為私人所有，反映造林事業一般民眾扮演重要角色。造林可視為利用土地進行種植生產的產業，一般民眾參與承領荒地造林可以增加副業，獲得日常用材、出售木材等實質利益，將原本無生產力的荒地賦予經濟價值，有現實經濟意義。環境方面，此時國民政府宣傳造林防水防旱的功能，並希望通過造林達到防沙固堤的效果，民眾通過植樹造林，亦可積極參與改善環境。通過環境改善，又保障農業活動、生命財產安全等經濟利益，造林、經濟、環境三者乃相依互存的關係。造林事業由於中日戰爭爆發後曾一度中斷，然日本華北佔領區當局於戰時亦相當重視各項調查試驗、推廣造林，顯示造林工作之重要與其延續性。因此，經濟與環境，可說是瞭解政府推動、民間參與造林事業的重要線索。

Due to the intense suppression of native vegetation in nascent areas of the State of Sergipe, one can notice a significant environmental degradation. Thus, it becomes necessary the adoption of practices aimed at the restoration of the vegetation and these can be carried through artificial regeneration with direct seeding or planting seedlings. Therefore, the study was carried to evaluate the development of native species in the Piauitinga watershed in Salgado-SE, with the artificial regeneration methods (direct sowing and planting seedlings), using the native forest species Anadenanthera macrocarpa (Benth.) Bren, Ceiba speciosa (A. St. Hill), Hymenaea stigonocarpa (Mart.) Hayne, Psidium guajava L. and Tabebuia aurea (Manso) Benth. & Hook. Initially, were held the physical and physiological quality of the seeds analysis in laboratory and subsequently a field experiment was established in a randomized block delimitation (RBD) in a factorial design with four replications, in an area previously occupied by pasture, located in Salgado-SE. The sowing was carried in holes (30x30x30cm), with spacing of 1,5 m x 1,5 m with 9 plants for species in every block and the planting of seedlings occurred similarly, totaling 90 plants per block, occupying an area of 0,1024 hectares. Were evaluated the percentage of emergence and seedling survival in the field, the initial development of seedlings and Relative Growth Rate (RGR) until 300 days after implantation. The species that showed better rates of emergence and survival was H. stigonocarpa with 74,44% and 48,89% respectively. Any plant of A. macrocarpa survived. In the of characteristics evaluation of growth in the field in relation to tillage, there was greater growth in height for P. guajava (25,84 cm) and diameter, T. aurea (6,51 mm). In planting seedlings, the more growth on the height was in the C. speciosa (93,26 cm) and the specie T. aurea presented greater increment in diameter (20,92 mm). There was statistical difference in the RGR of plants for planting two strategies. The species T. aurea, C. speciosa and H. stigonocarpa characteristics presented viable for use by direct seeding and planting seedlings in the recuperation of degraded areas of nascent. The strategy of planting that had higher averages for the parameters evaluated was the planting of seedlings in recuperation of the area studied. / Devido à intensa supressão da vegetação nativa em áreas de nascentes do Estado de Sergipe, pode-se notar um significativo quadro de degradação ambiental. Dessa forma, torna-se necessária a adoção de práticas que visem à recomposição da vegetação e estas podem ser realizadas através da regeneração artificial, com a semeadura direta ou plantio de mudas. Diante o exposto, o trabalho foi realizado com o objetivo de avaliar o desenvolvimento de espécies florestais nativas em área de nascente na bacia hidrográfica do rio Piauitinga, no município de Salgado-SE, com relação aos métodos de regeneração artificial (semeadura direta e plantio de mudas), utilizando-se as espécies florestais nativas Anadenanthera macrocarpa (Benth.) Bren, Ceiba speciosa (A. St. Hill), Hymenaea stigonocarpa (Mart.) Hayne, Psidium guajava L. e Tabebuia aurea (Manso) Benth. & Hook. Análises da morfometria, determinação da umidade e qualidade fisiológica das sementes foram previamente realizadas em laboratório. O experimento em campo foi implantado em Delineamento em Blocos Casualizados (DBC), em esquema fatorial com quatro repetições, em uma área anteriormente ocupada por pastagem, localizada no município de Salgado-SE. A semeadura direta e o plantio de mudas foram realizados em covas (30x30x30cm), com espaçamento de 1,5m x 1,5m, contendo 9 plantas por espécie em cada bloco, totalizando 90 plantas por bloco, ocupando uma extensão de 0,1024 hectares. Foram avaliadas as porcentagens de emergência e sobrevivência das plântulas em campo, desenvolvimento inicial das mudas e Taxa de Crescimento Relativo (TCR) até os 300 dias após a implantação. A espécie que apresentou melhores índices de emergência e sobrevivência foi H. stigonocarpa com 74,44% e 48,89%, respectivamente. Na semeadura direta, nenhuma planta de A. macrocarpa sobreviveu. Na avaliação das características de crescimento em campo em relação à semeadura direta, observou-se maior crescimento em altura para P. guajava (25,84cm) e para diâmetro, T. aurea (6,51mm). No plantio de mudas, o maior crescimento em altura foi na C. speciosa (93,26cm) e a espécie T. aurea apresentou maior incremento em diâmetro (20,92mm). Houve diferença estatística na TCR das plantas, para as duas estratégias de plantio. As espécies T. aurea, C. speciosa e H. stigonocarpa apresentaram características viáveis para serem utilizadas por meio da semeadura direta e plantio de mudas em projetos de recuperação em áreas de nascentes degradadas. A estratégia de plantio que apresentou maiores médias em relação aos parâmetros avaliados foi o plantio de mudas, na recuperação da área estudada.