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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Vegetation dynamics and soil characteristics of lophostemon confertus plantations in Hong Kong.

January 2004 (has links)
Kong Hoi-Yeung. / Thesis submitted in: November 2003. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 132-146). / Abstracts in English and Chinese. / Abstract --- p.i / Abstract (in Chinese) --- p.iv / Acknowledgement --- p.v / Table of contents --- p.vii / List of tables --- p.x / List of figures --- p.xi / List of plates --- p.xii / List of appendices --- p.xii / Chapter Chapter one --- Introduction / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Afforestation in Hong Kong --- p.2 / Chapter 1.3 --- Conceptual framework of the study --- p.6 / Chapter 1.4 --- Objectives of the study --- p.13 / Chapter 1.5 --- Scope and significance of the study --- p.14 / Chapter 1.6 --- Organization of the thesis --- p.15 / Chapter Chapter Two --- The Study Area / Chapter 2.1 --- Geographical setting of Hong Kong --- p.17 / Chapter 2.1.1 --- Climate --- p.17 / Chapter 2.1.2 --- Geology --- p.19 / Chapter 2.1.3 --- Soils --- p.20 / Chapter 2.1.4 --- Vegetation --- p.21 / Chapter 2.1.5 --- Characteristics of Lophostemon confertus --- p.23 / Chapter 2.2 --- Site selection --- p.24 / Chapter Chapter Three --- Stand Characteristics of Lophostemon confertus Plantations / Chapter 3.1 --- Introduction --- p.31 / Chapter 3.2 --- Methodology --- p.35 / Chapter 3.2.1 --- Sample plots design --- p.35 / Chapter 3.2.2 --- Tree density --- p.35 / Chapter 3.2.3 --- Tree growth parameters --- p.35 / Chapter 3.2.4 --- Data processing and statistical analysis --- p.36 / Chapter 3.3 --- Results and discussion --- p.37 / Chapter 3.3.1 --- Tree density and mortality rate --- p.37 / Chapter 3.3.2 --- Growth performance of Lophostemon confertus --- p.39 / Chapter 3.3.3 --- Growth rate of Lophostemon confertus in the plantations --- p.41 / Chapter 3.4 --- Conclusion --- p.44 / Chapter Chapter Four --- Soil Characteristics of Lophostemon confertus Plantations / Chapter 4.1 --- Introduction --- p.47 / Chapter 4.2 --- Methodology --- p.51 / Chapter 4.2.1 --- Soil sampling --- p.51 / Chapter 4.2.2 --- Laboratory analysis --- p.52 / Chapter 4.2.3 --- Texture --- p.52 / Chapter 4.2.4 --- Soil pH --- p.53 / Chapter 4.2.5 --- Organic carbon --- p.53 / Chapter 4.2.6 --- Total Kjeldahl Nitrogen (TKN) --- p.53 / Chapter 4.2.7 --- Carbon: Nitrogen ratio --- p.54 / Chapter 4.2.8 --- Mineral nitrogen (NH4-H and N03-N) --- p.54 / Chapter 4.2.9 --- Available phosphorus --- p.55 / Chapter 4.2.10 --- Exchangeable cations --- p.55 / Chapter 4.3 --- Data processing and statistical analysis --- p.55 / Chapter 4.4 --- Results and discussion --- p.56 / Chapter 4.4.1 --- Soil texture --- p.56 / Chapter 4.4.2 --- Effects of Lophostemon confertus plantations on reaction pH --- p.58 / Chapter 4.4.3 --- "Effects of Lophostemon confertus plantations on SOM, TKN and mineral nitrogen" --- p.59 / Chapter 4.4.4 --- Effects of Lophostemon confertus plantations on available P and exchangeable cations --- p.69 / Chapter 4.4.5 --- Effects of Lophostemon confertus plantations on nutrient status of the soils --- p.73 / Chapter 4.5 --- Conclusion --- p.79 / Chapter Chapter Five --- Understorey Vegetation of Lophostemon confertus Plantations / Chapter 5.1 --- Introduction --- p.81 / Chapter 5.2 --- Methodology --- p.85 / Chapter 5.2.1 --- Understorey plant sampling --- p.85 / Chapter 5.2.2 --- Species identification and nomenclature --- p.86 / Chapter 5.2.3 --- Plant growth parameters --- p.87 / Chapter 5.2.4 --- Data processing and statistical analysis --- p.87 / Chapter 5.3 --- Results and discussion --- p.89 / Chapter 5.3.1 --- Floristic composition of the Lophostemon confertus plantations --- p.89 / Chapter 5.3.2 --- "Species richness, diversity and woody abundance of the understorey" --- p.93 / Chapter 5.3.3 --- Species composition and structure of understories --- p.99 / Chapter 5.3.4 --- Dynamics of species establishment in the understorey --- p.109 / Chapter 5.4 --- Conclusion --- p.112 / Chapter Chapter Six --- Conclusion / Chapter 6.1 --- Summary of findings --- p.114 / Chapter 6.2 --- Implications of the study --- p.118 / Chapter 6.2.1 --- Ecological value of Lophostemon confertus plantations in Hong Kong --- p.118 / Chapter 6.2.2 --- Rehabilitation of badland derived from granite --- p.124 / Chapter 6.2.3 --- Management of the existing plantations --- p.126 / Chapter 6.3 --- Limitations of the study --- p.129 / Chapter 6.4 --- Suggestions for future study --- p.130 / References --- p.132 / Appendices --- p.147
32

Three essays on private landowners' response to incentives for carbon sequestration through forest management and afforestation

Kim, Taeyoung 14 December 2012 (has links)
This dissertation consists of three essays on private landowners' response to incentives for carbon sequestration in forests. The first essay examines private landowner response to incentives for carbon sequestration through various combinations of intermediate management practices. The second essay focuses on agricultural landowners' willingness to participate in an incentive program for carbon sequestration through afforestation, and estimates the potential for carbon sequestration from afforestation, as well as its cost. The third study examines relative performances of incentive targeting strategies for forest carbon sequestration under asymmetric information given spatially heterogeneous land types. The first essay uses an econometric approach to analyze the factors affecting non-industrial private forest landowners' choice of forest management practices, and examines how these choices might change in response to the use of incentives for carbon sequestration. I use estimated parameters to simulate the carbon sequestration potential for different combinations of management practices, and compare the effectiveness and costs of performance-based and practice-based incentive payment schemes in the Western U.S. The results suggest that incentive payments can increase the probability that desirable combinations of management practices are adopted, and particularly that incentives targeting increased fertilization yield the highest carbon sequestration potential. I also find that a performance-based payment scheme produces higher carbon sequestration than a practice-based payments scheme. However, the annual sequestration potential of intermediate forest management in response to incentive payment is not as large as the sequestration potential of afforestation. The second essay uses a survey-based stated preference approach to predict landowners' willingness to participate in a tree planting program for carbon sequestration as a function of various factors affecting landowners' decision making and different levels of incentive payments. The estimation results show that the annual payment for carbon sequestration significantly and positively affects landowners' stated level of enrollment in a tree planting program. I use the estimated parameters to conduct regional level simulations of carbon sequestration in response to incentive payments. These simulations show that the carbon supply function in the Pacific Northwest region is steeper than in the Southeast region because of the lower adoption rate and less available lands. The national level carbon supply functions derived from this study are steeper than those obtained from bottom-up engineering approaches and optimization models, and are in the same range as those from revealed preference approach studies. The third essay uses both a conceptual analysis and a numerical analysis to examine the relative performances of incentive programs for carbon sequestration using alternative targeting criteria in the presence of asymmetric information and heterogeneity in costs and benefits. The results show that in the presence of asymmetric information, the combination of high cost-high benefit variability and negative correlation, which is the combination that achieves the greatest benefit gains under perfect information, can result in the greatest benefit losses. Additionally, a comparison of two targeting schemes shows that if cost variability is greater than benefit variability with negative correlation, the benefit achieved under benefit-cost ratio targeting can be lower than that under acreage targeting, so that an optimal targeting strategy under perfect information may no longer be optimal under asymmetric information. / Graduation date: 2013
33

Analysis of the potential socio-economic impact of establishing plantation forestry on rural communities in Sanga District, Niassa province, Mozambique

Landry, Jennifer Ann January 2009 (has links)
Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: This thesis assesses the livelihoods of rural households in a proposed green field forestry area, located in Sanga District of Niassa province, Mozambique. The livelihood analysis was used to analyze potential socio-economic impacts of introducing forest plantations to rural households located within the proposed afforestation area. The study made use of household interviews, key informant interviews and secondary data. The sustainable livelihoods framework was used in the research process to develop the household questionnaire and to identify livelihood strategies. Data was analyzed using 331 household questionnaires collected throughout the proposed afforestation area in various communities in the study area. Findings from the study indicated that there is minimal wealth gaps between rural households; but that the introduction of the forestry industry and the subsequent employment created thereof may result in larger wealth gaps between wage earning and non-wage earning households. The study further concludes by linking the potential socio-economic impacts with mitigation recommendations that could be harmonized with FSC Standard requirements for forestry companies interested in developing a forest industry in the study area. / AFRIKAANSE OPSOMMING: Hierdie tesis ontleed die lewensbestaan van landelike huishoudings in ‘n voorgestelde nuwe bosbou area, gelee in die Sanga distrik van die Niassa provinsie, Mosambiek. Die lewensbestaan ontleding was gebruik om die potensiele sosio-ekonomiese impak van die vestiging van bosbou plantasies op landelike huishoudings in die voorgestelde bebossings area te analiseer. Hierdie studie het gebruik gemaak van huishoudelike onderhoude, sleutel informant onderhoude asook sekondere data. Die volhoubare lewensbestaan raamwerk was gebruik in die navorsings proses om die huishoudelike onderhoude te ontwikkel en om die huishoudelike strategiee te identifiseer. Data was geanaliseer van 331 huishoudelike onderhoude afgeneem in verskeie gemeenskappe binne die studie areas. Bevindinge van die studie het aangetoon dat daar minimale inkomste gapings is tussen landelike huishoudings, maar met die vestiging van kommersiele bosbou en geassosieerde werskeppings moontlikhede, mag groter inkomste gapings ontwikkel tussen huishoudings wat inkostes uit bosbou verdien en huishoudings daarsonder. Verder het die studie aangetoon dat daar ‚n potensiele sosiale impak is van mense wat na die area migreer en dat sulke impakte deur FSC sertifisering beheer kan word.
34

Les communautés végétales des interfaces forêt-prairie et leur environnement face aux cas d'afforestation et de déforestation / Plant communities of forest-grassland interfaces and their environment in a context of afforestation and deforestation

Burst, Maxime 04 July 2017 (has links)
En Europe tempérée, les paysages sont dominés par une mosaïque de forêts, prairies et cultures depuis plusieurs siècles. Cette longue période de temps a permis la spécialisation d'espèces au sein des habitats et de leurs interfaces grâce à de forts contrastes environnementaux. Cependant, de fréquents changements d'occupation du sol ont eu lieu par le passé, lesquels se sont accélérés dans les dernières décennies, remettant en cause la stabilité des communautés végétales et de leur environnement. L'afforestation d'anciennes prairies et l'extension de prairies par déforestation, le plus souvent issues de la progression et de la régression d'anciennes lisières, n'ont que peu été étudiées. Au sein des interfaces foret-prairie, en plus d'un effet lisière induit au sein de chaque habitat par la proximité de l'habitat adjacent, un effet histoire peut s'ajouter au sein des habitats récents, c'est-à-dire un héritage environnemental et/ou floristique (dette d'extinction, crédit de colonisation). Au sein des lisières d'habitats récents, une interaction entre effet lisière et effet histoire peut également être rencontrée. Dans cette thèse, les objectifs ont été d'évaluer l'influence relative de l'effet lisière et de l'effet histoire le long d'interfaces forêt-prairie stables, issues d'afforestation et issues de déforestation en s'intéressant (i) aux conditions environnementales, (ii) à la richesse et à la composition floristique des communautés végétales, et (iii) aux valeurs de traits au sein des communautés. Nos résultats ont montré des gradients croissants d'intensité lumineuse et de nutriments des sols allant des lisières aux cœurs de prairies. En réponse à ces gradients, un fort effet lisière sur la composition des communautés végétales a été trouvé en prairie. Ces différences floristiques entre lisières et cœurs de prairies s'expliquent par la présence d'un grand nombre d'espèces transgressives parmi les espèces spécialistes de forêt, lesquelles ont des valeurs de traits favorisant leur transgression en prairie. A côté de cela, une dette d'extinction d'espèces spécialistes de prairie a été trouvée au sein des forêts récentes, laquelle est responsable d'une hauteur végétative plus importante par rapport aux forêts anciennes. Ces résultats s'expliquent par une intensité lumineuse restée plus élevée au sein des forêts récentes, même après plusieurs décennies. Une dette d'extinction d'espèces spécialistes de forêt a aussi été mise en évidence en lisière de prairie récente, laquelle est le résultat d'une interaction entre effet lisière et effet histoire. En prairie récente, l'effet lisière favorise le maintien des espèces forestières. D'après nos résultats, les lisières de forêt et de prairie, dont la plupart ont subit un déplacement au cours des deux derniers siècles, hébergent de nombreuses espèces végétales spécialistes des habitats anciens, parfois en dette d'extinction. Une réévaluation de la distribution des espèces au sein des communautés végétales de forêts et prairies semble alors nécessaire en tenant en compte de l'histoire des habitats. Face à l'instabilité croissante des forêts et prairies, l'identification des espèces en dette d'extinction représente une chance pour la conservation et la restauration de la biodiversité végétale / In temperate Europe, landscapes are dominated by a mosaic of forests, grasslands and crops since several centuries. This long period of time allowed the specialization of species within the habitats and their interfaces thanks to strong environmental contrasts. However, there have been frequent land-use changes in the past, which have accelerated in recent decades, challenging the stability of plant communities and their environment. The afforestation of former grasslands and the extension of grasslands by deforestation, mostly resulting from the progression and regression of the edges, have been poorly studied. In the forest-grassland interfaces, in addition to an edge effect induced in each habitat by the proximity to the adjacent habitat, a history effect can be added in recent habitats, i.e. an environmental and/or floristic legacy (extinction debt, colonization credit). In the recent habitat edges, an interaction between edge effect and history effect can also be encountered. In this thesis, the objectives were to evaluate the relative abundance of the edge effect and the history effect along forest-grassland interfaces stable, from afforestation process and from deforestation process, by studying (i) environmental conditions, (ii) the richness and floristic composition of plant communities, and (iii) trait values within communities. Our results showed increasing gradients of light intensity and soil nutrients ranging from grassland edges to grassland cores. In response to these gradients, a strong edge effect on the composition of plant communities was found in grasslands. These floristic differences between grassland edges and grassland cores are explained by the presence of a large number of transgressive species among the forest specialist species, which have trait values favoring their transgression in grasslands. Besides this, an extinction debt of grassland specialist species has been found in recent forests, which is responsible for a higher vegetative height compared to ancient forests. These results can be explained by the fact that light intensity remained higher in recent forests, even after several decades. An extinction debt of forest specialist species has also been demonstrated in the recent grassland edges, which is the result of an interaction between edge effect and history effect. In recent grasslands, the edge effect favors the maintenance of forest species. According to our findings, forest and grassland edges, most of which have been displaced over the past two centuries, are home to many plant species that are habitat specialists, sometimes in extinction debt. A re-evaluation of the distribution of species within forest and grassland plant communities then seems necessary, taking into account the history of habitats. In a context of increasing forests and grasslands instability, the identification of species in extinction debt represents an opportunity for the conservation and restoration of plant biodiversity
35

Recovery of vegetation and bees after removal of pine forests by fire in the Limietberg region of the Cape Floristic Region biodiversity hotspot

Gardee, Muhammed Nizaar 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The present global biodiversity crisis is characterized mostly by loss of species due to habitat destruction but there other major threats – notably invasive alien species. The term “biodiversity hotspot” has been coined to emphasize areas for conservation prioritization – areas that have high biodiversity under threat from habitat destruction, invasive species, etc. The Cape Floristic Region (CFR) in the Western Cape (WC) Province of South Africa has the highest biodiversity of all Mediterranean-type climate regions globally and is classified among global biodiversity hotspots. The CFR, a Mediterranean-type climate heathland with a naturally high fire frequency, faces threat from transformation by development, disturbed (increased) fire frequencies and intensities, and invasive organisms, most notably invasive trees. Such threats disturb keystone species and keystone processes including insect pollinator assemblages and associated insect flower visitation webs and frequencies. Invasive pines are a serious threat to insect flower visitation as pine trees (Pinus spp.) shade out much indigenous vegetation in the CFR. Little is known of their long-term effects on insect flower visitors and vegetation recovery in post-pine restoration and recovery areas after such trees are removed. I investigated the recovery of vegetation and the most important insect pollinator, bees, after the removal of pines by fire and passive recovery in a CFR valley in the Western Cape. In 1999, a wildfire burned much of the WC Limietberg Nature Reserve along with an adjacent pine tree forestry stand - which was then left to recover, providing an ideal opportunity to investigate the enduring effects of pine afforestation in the CFR. In two data chapters, I compared the post-fire passive recovery of vegetation (Chapter 2) and bee diversity (Chapter 4) in areas which had previously been planted with pines vs. those which had contained natural fynbos. To improve on sampling methodology, I conducted an experiment that demonstrated the Observer Effect in bee sampling with a sweep net (Chapter 3), and I developed a novel sampling device (Chapter 5) for insect flower visitors. Sampling of vegetation and bee diversity was conducted in a paired sampling design, where fynbos (Natural) sub-sites were paired with sub-sites which had previously been afforested with pines (Post-Pine Recovery; PPR) and the two sub-sites were separated by a distinct, linear boundary (Natural/PPR boundary). Sampling was conducted along transects parallel to the boundary and extending in both directions from the boundary into the Natural and in the opposite direction into PPR sub-sites. Five transects were positioned at 3, 10, 20, 30, and 40 m from the boundary (Ecotone) and three were positioned at 60, 80, and 100 m from the boundary (Deep). In Chapter 2, I found that natural sub-sites consistently had higher total plant species abundance and species richness than PPR sub-sites. Approximately two thirds of plant species were more abundant in Natural sub-sites than in PPR sub-sites. There was no significant correlation in species richness or abundance with distance from the Natural/PPR boundary. Some genera are cautiously indicated as having lower success in recovery after pine afforestation: Erica spp., Restio spp., Hypodiscus spp. while Helichrysum spp. is also tentatively indicated to recover well in PPR sub-sites. Soil disturbance and concomitant disruption of normal ecosystem functions, including pollination, is indicated as a probable reason for disruption of plant recovery. In Chapter 3, sweep netting methodology was tested for the Observer Effect. A noticeable increase in bee visitation frequency to a common generalist plant species in bloom, Metalasia densa, was correlated with longer waiting periods after I stopped moving indicating the presence of an Observer Effect. This suggests that sweep netting for bees should only be commenced after a waiting period of five minutes during which the sweep netter is motionless. In Chapter 4, using a flight-intercept modified pan trap, I compared bee species richness and bee species abundance across different seasons and in both mass-flowering and sparser flower patches. There was no significant difference in bee species richness between Natural and PPR sub-sites. All bee species, except one complex, were more abundant in Natural sub-sites. Nearly two thirds of all bee species (n=37 of 56) caught with sweep netting and the modified pan trap are undescribed species. Similar to the vegetation, the effects of soil disturbance as a result of decades of pine forest shading and pine forest litterfall followed by an unusually hot pine forest fire are indicated as the most likely reasons for lower bee abundance in PPR sub-sites. This is due to the difficulty associated with viable nest establishment and suitable pollen and nectar forage availability in disturbed areas. In Chapter 5, the newly developed Pan and Flight Intercept Combination (PAFIC) trap’s design, pilot testing, and comparison with the traditional pan trap is discussed. A preliminary test suggests that the PAFIC trap is more efficient (with higher abundance) than the traditional pan trap. In Chapter 6, I discuss the implications of the disturbance of pine forestry and unusual pine fire to plant species and bee species assemblages. Bee-pollination webs in PPR sub-sites are indicated as being substantially simpler than those in Natural areas as well as compositionally different. The recovery of pollination as a keystone process in post pine-afforestation areas faces a substantial challenge given the disturbance to soil that decades of pine afforestation followed by pine forest fire can cause. Some suggestions are made for the restoration of fynbos areas recovering from pine afforestation including a discussion of augmenting re-vegetation measures (fynbos seed dispersal and seedling planting) with methods of restoring of healthy pedogenesis, epigaeic arthropod communities, and fynbos seedbanks. / AFRIKAANSE OPSOMMING: Die huidige globale biodiversiteit krisis is gekenmerk meestal deur die verlies van spesies as gevolg van die vernietiging van habitat. Maar daar is ook ander groot bedreigings – veral merkbaar indringerspesies. Die term “biodiversiteit brandpunt” is geskep om gebiede vir bewaring prioritisering te beklemtoon - gebiede wat 'n hoë biodiversiteit bevat wat bedreig word deur die vernietiging van habitat, indringerspesies, ens. Die Kaap Floristiese Streek (KFS) in die Wes-Kaap (WK) Provinsie van Suid-Afrika het die hoogste biodiversiteit van alle Mediterreense tipe klimaat streke wêreldwyd, en is onder die globale biodiversiteit brandpunte geklassifiseer. Die KFS, 'n Mediterreense-tipe klimaat heideveld met 'n natuurlike hoë brand frekwensie, word bedreig as gevolg van transformasie deur ontwikkeling, versteurde (verhoogde) vuur regimes, en indringer organismes, veral indringerbome. Sulke bedreigings versteur hoeksteen spesies en die hoeksteen prosesse, insluitende insek bestuiwer samestelling en verwante insek blom besoekings webbe en frekwensies. Indringer dennebome (Pinus spp.) is 'n ernstige bedreiging vir insek blom besoeking want dennebome verskaf skaduwee aan baie inheemse plantegroei in die KFS. Min is bekend oor die langtermyn effekte op insek blom besoekers en plantegroei restorasie na denneboom verwydering en restorasie gebiede na sodanige bome verwyder word. Ek ondersoek die restorasie van plantegroei en die belangrikste insek bestuiwer, bye, na die vernietiging van dennebome deur vuur en passiewe herstel in 'n KFS vallei in die Wes-Kaap. In 1999 het'n veldbrand baie van die WK Limietberg Natuurreservaat saam met 'n aangrensende denneboom bosbouplantasie gebrand - wat toe gelaat is om te herstel via intermediêre suksessie na inheemse fynbos plantegroei. Dit bied 'n ideale geleentheid om die blywende gevolge van denneboom aanplanting in die KFS te ondersoek. In twee data hoofstukke, vergelyk ek die passiewe herstel van plantegroei na ‘n brand (Hoofstuk 2) en by diversiteit (Hoofstuk 4) in gebiede wat voorheen geplant is met dennebome teenoor diegene wat natuurlike fynbos vervat het. Om te verbeter op steekproefmetodiek, het ek 'n eksperiment onderneem wat demonstreer hoe die Waarnemer Effek by monsterneming met 'n vee-net beïnvloed (Hoofstuk 3), en het ek 'n nuwe monsterneming toestel ontwerp (Hoofstuk 5) vir insek blom besoekers. Monsterneming van plantegroei en by diversiteit is uitgevoer in 'n gegroepeerde steekproef ontwerp, waar fynbos (Natuurlik) sub-terreine gegroepeer is met sub-terreine wat voorheen aangeplant was met dennebome (Na Denneboom Verwydering Herstel; NDVH) en die twee sub-terreine is geskei deur 'n duidelike, lineêre grens (Natuurlik / NDVH grens). Steekproefneming is gedoen langs transekte parallel tot die grens en versprei in albei rigtings van die grens tot binne die natuurlike fynbos en in die teenoorgestelde rigting tot binne NDVH sub-terreine. Vyf transekte is geposisioneer binne 50 m van die grens (Oorgang sone) en drie is ver geplaas van die grens (Diep). In Hoofstuk 2 het ek gevind dat natuurlike sub-terreine konsekwent hoër totale getal plant individue en spesierykheid as NDVH sub-terreine gehad het. Ongeveer twee derdes van plantspesies was meer volop in natuurlike sub-terreine as in NDVH sub-terreine. Daar was geen beduidende korrelasie in spesierykheid of totale hoeveelheid plant individue met betrekking tot afstand van die Natuurlike /NDVH grens. Sommige genera word versigtig aangedui as met laer sukses in die restorasie terreine na denneboom aanplanting: Erica spp., Restio spp., Hypodiscus spp. terwyl Helichrysum spp. voorlopig aangedui is as goed herstel in NDVH sub-terreine. Grondversteuring en gepaardgaande ontwrigting van normale funksionering van die ekosisteem, insluitend bestuiwing, word aangedui as 'n waarskynlike rede vir die ontwrigting van die herstel van plantegroei. In Hoofstuk 3 is vee-net metodologie getoets vir die Waarnemer Effek. 'N merkbare toename in by besoeking frekwensie van 'n algemene plantspesie in blomtyd, Metalasia densa, is gekorreleer met langer wagtydperke nadat ek gestop het om te beweeg, en dui dus op die teenwoordigheid van 'n Waarnemer Effek. Dit dui daarop dat die vee-net vir bye eers gebruik moet word na 'n wagtydperk waartydens die waarnemer bewegingloos verkeer. In Hoofstuk 4, met behulp van 'n vlug-onderskep gewysigde pan lokval, het ek by spesierykheid en totale by hoeveelheid vergelyk oor verskillende seisoene en in beide massa-beblomde en yler blom kolle. Daar was geen beduidende verskil in by spesierykheid tussen natuurlike en NDVH sub-terreine. Alle by spesies, behalwe een spesie kompleks, was meer volop in natuurlike sub-terreine. Byna twee derdes van alle by spesies (n = 37 van 56) gevang met vee-nette en die van die gewysigde pan lokvalle is onbeskryfde spesies. Soortgelyk aan die plantegroei, is die gevolge van grondversteuring as gevolg van dekades van denneboom bos skadu en denneboom bos blaar afval gevolg deur 'n buitengewoon warm denneboom bos brand as die mees waarskynlike redes vir laer by hoeveelheid in NDVH sub-terreine aangedui. Dit is as gevolg van die probleme wat verband hou met lewensvatbare nes vestiging en geskikte stuifmeel en nektar voer beskikbaarheid in versteurde gebiede. In Hoofstuk 5 is die nuut ontwikkelde Pan en Vlug Onderskep Kombinasie (PEVOK) lokval ontwerp, aanvanklike toetsing, en vergelyking met die tradisionele pan lokval bespreek. 'N Voorlopige toets dui daarop dat die PEVOK lokval meer doeltreffend (met 'n hoër oorvloed) is as die tradisionele pan lokval. In Hoofstuk 6 bespreek ek die implikasies van die versteuring van denneboom bosbou en ongewone denneboom vuur met betrekking tot plant spesies en by spesies samestelling. By-bestuiwing webbe in NDVH sub-terreine word aangedui as wesenlik eenvoudiger as dié in natuurlike areas asook verskillend in samestelling. Die herstel van bestuiwing as 'n hoeksteen in na denneboom-aangeplante gebiede staar 'n aansienlike uitdaging in die gesig, gegee die versteuring van grond wat dekades van denneboom aanplanting gevolg deur denneboom bos brand kan veroorsaak. Sommige voorstelle is gemaak vir die herstel van fynbos gebiede wat herstel van denneboom aanplanting, insluitend 'n bespreking van die aanvulling van plantegroei hervestiging maatreëls (fynbos saadverspreiding en saailinge plant) met die metodes van die herstel van 'n gesonde pedogenese, bogrondse geleedpotige gemeenskappe, en fynbos saadbanke.
36

Balanço hídrico climático distribuído como suporte a decisão para ações de restauração florestal na bacia do rio Piracicaba / Climatic water balance distributed as decision support for forest restoration in Piracicaba river basin

Maia, Cássio Bueno 12 February 2016 (has links)
A escassez hídrica devido às baixas vazões e problemas de captação de água são objeto de debates e conflitos na bacia hidrográfica do rio Piracicaba. A restauração florestal é tida como uma alternativa para a minimização destes conflitos. No entanto, as florestas modificam significativamente os processos hidrológicos, influenciando a dinâmica da água na bacia hidrográfica. Portanto, a fim de se obter disponibilidade hídrica a longo prazo, é necessário identificar as áreas aptas para a restauração florestal, onde os efeitos sejam positivos para os recursos hídricos. Dentro deste contexto, o presente trabalho teve como objetivo utilizar um modelo hídrico climático distribuído para espacializar as características hídricas e climáticas favoráveis, ou não, à restauração florestal. Para isto, foi utilizada a bacia hidrográfica do rio Piracicaba como área de estudo (12.500 km2). Foram obtidos dados mensais normais de precipitação, temperatura, radiação solar, topografia e capacidade de armazenamento de água no solo, distribuídos espacialmente na bacia hidrográfica. A partir destas informações, foi calculado o balanço hídrico climático distribuído (BHCD) através da ferramenta \"Water Balance\", que calcula a evapotranspiração potencial e real, o déficit e o excedente hídrico em um ambiente SIG (Sistema de Informações Geográficas). Os resultados foram comparados com o balanço hídrico climático (BHC), tradicional ou pontual, e uma análise estatística de agrupamentos de áreas com características hidrológicas semelhantes foi realizada. A divisão da bacia hidrográfica em classes (ou grupos) com características semelhantes permite compreender a sensibilidade natural das áreas e possíveis efeitos na disponibilidade hídrica. A capacidade de determinar, em diferentes escalas de estudo, a dinâmica dos recursos hídricos possibilitou melhores condições de análise diante da heterogeneidade natural da bacia hidrográfica. Os dados gerados permitiram identificar áreas onde as recomendações locais podem ser feitas com base nas variáveis do balanço hídrico. Dessa forma, a espacialização das variáveis e o agrupamento por características hidrológicas são ferramentas que podem ser utilizadas em projetos de restauração florestal, uma vez que podem subsidiar decisões a respeito das áreas mais favoráveis a restauração florestal. / Water shortage due to low flows and water basin capitation problems are subject of debates and conflicts in Piracicaba river basin. Forest restoration is an alternative to minimize these conflicts. However, forests significantly modify the hydrological processes, influencing the dynamics of the water in the watershed. Therefore, in order to obtain water availability in the long term, it is necessary to identify suitable areas for forest restoration, where effects are positive for water resources. In this context, this study aimed at using a climatic model water to spatialize the water features and favorable climate, or not, to forest restoration. For this purpose, the Piracicaba river basin was used as study area (12,500 km2). Monthly data were obtained from precipitation, temperature, solar radiation, topography, and water storage capacity in the soil. Trough these data, distributed climatic water balance was calculated by the Water Balance tool, integrated in a GIS (Geographic Information System) which calculates the potential and actual evapotranspiration, deficit and the surplus water. Results were compared with traditional climatic water balance. Later statistical analyses was performed to identify areas with similar hydrological characteristics. This division of the watershed into classes (or groups) with similar characteristics allows us to understand the natural sensitivity of the areas and possible effects on water availability. The ability to determine, in different study scales, the dynamics of water resources, has enabled better analysis of conditions on the natural heterogeneity of the basin. Raised info has identified areas where local recommendations can be made based on the variables of water balance. Thus, spatial distribution of variables and grouping by hydrological characteristics are tools that can be used in forest restoration projects as it can subsidize decisions regarding the most favorable areas for forest restoration.
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Balanço hídrico climático distribuído como suporte a decisão para ações de restauração florestal na bacia do rio Piracicaba / Climatic water balance distributed as decision support for forest restoration in Piracicaba river basin

Cássio Bueno Maia 12 February 2016 (has links)
A escassez hídrica devido às baixas vazões e problemas de captação de água são objeto de debates e conflitos na bacia hidrográfica do rio Piracicaba. A restauração florestal é tida como uma alternativa para a minimização destes conflitos. No entanto, as florestas modificam significativamente os processos hidrológicos, influenciando a dinâmica da água na bacia hidrográfica. Portanto, a fim de se obter disponibilidade hídrica a longo prazo, é necessário identificar as áreas aptas para a restauração florestal, onde os efeitos sejam positivos para os recursos hídricos. Dentro deste contexto, o presente trabalho teve como objetivo utilizar um modelo hídrico climático distribuído para espacializar as características hídricas e climáticas favoráveis, ou não, à restauração florestal. Para isto, foi utilizada a bacia hidrográfica do rio Piracicaba como área de estudo (12.500 km2). Foram obtidos dados mensais normais de precipitação, temperatura, radiação solar, topografia e capacidade de armazenamento de água no solo, distribuídos espacialmente na bacia hidrográfica. A partir destas informações, foi calculado o balanço hídrico climático distribuído (BHCD) através da ferramenta \"Water Balance\", que calcula a evapotranspiração potencial e real, o déficit e o excedente hídrico em um ambiente SIG (Sistema de Informações Geográficas). Os resultados foram comparados com o balanço hídrico climático (BHC), tradicional ou pontual, e uma análise estatística de agrupamentos de áreas com características hidrológicas semelhantes foi realizada. A divisão da bacia hidrográfica em classes (ou grupos) com características semelhantes permite compreender a sensibilidade natural das áreas e possíveis efeitos na disponibilidade hídrica. A capacidade de determinar, em diferentes escalas de estudo, a dinâmica dos recursos hídricos possibilitou melhores condições de análise diante da heterogeneidade natural da bacia hidrográfica. Os dados gerados permitiram identificar áreas onde as recomendações locais podem ser feitas com base nas variáveis do balanço hídrico. Dessa forma, a espacialização das variáveis e o agrupamento por características hidrológicas são ferramentas que podem ser utilizadas em projetos de restauração florestal, uma vez que podem subsidiar decisões a respeito das áreas mais favoráveis a restauração florestal. / Water shortage due to low flows and water basin capitation problems are subject of debates and conflicts in Piracicaba river basin. Forest restoration is an alternative to minimize these conflicts. However, forests significantly modify the hydrological processes, influencing the dynamics of the water in the watershed. Therefore, in order to obtain water availability in the long term, it is necessary to identify suitable areas for forest restoration, where effects are positive for water resources. In this context, this study aimed at using a climatic model water to spatialize the water features and favorable climate, or not, to forest restoration. For this purpose, the Piracicaba river basin was used as study area (12,500 km2). Monthly data were obtained from precipitation, temperature, solar radiation, topography, and water storage capacity in the soil. Trough these data, distributed climatic water balance was calculated by the Water Balance tool, integrated in a GIS (Geographic Information System) which calculates the potential and actual evapotranspiration, deficit and the surplus water. Results were compared with traditional climatic water balance. Later statistical analyses was performed to identify areas with similar hydrological characteristics. This division of the watershed into classes (or groups) with similar characteristics allows us to understand the natural sensitivity of the areas and possible effects on water availability. The ability to determine, in different study scales, the dynamics of water resources, has enabled better analysis of conditions on the natural heterogeneity of the basin. Raised info has identified areas where local recommendations can be made based on the variables of water balance. Thus, spatial distribution of variables and grouping by hydrological characteristics are tools that can be used in forest restoration projects as it can subsidize decisions regarding the most favorable areas for forest restoration.
38

Estudo da vegetação arbórea da Praça dos Girassóis, Palmas-TO

Panta, Maxwell Viana 28 March 2017 (has links)
As praças podem ser definidas como espaços urbanos livres utilizados como locais públicos, as quais devem ser priorizadas dentro do planejamento urbano, de modo a assumir seu papel de área verde, tornando local de convivência e alcançando sua função socioambiental. A gestão e manejo dessas áreas dependem diretamente do seu conhecimento fitossociológico detalhado. Partindo disto, este trabalho objetivou-se estudar a composição florística da Praça dos Girassóis na cidade de Palmas – TO. Realizou-se o inventário de todas as árvores presentes na Praça dos Girassóis, considerando todos os indivíduos arbóreos com CAP (circunferência a altura do peito, 1,30 m do solo) igual ou superior a 20 cm foram identificados quanto à família botânica, nome científico, nome popular, origem (nativo ou exótico) bem como estado fitossanitário, endemismo e ameaça de extinção. Após a coleta de dados, calculou-se o índice de diversidade proposto por Shannon-Weiner (H’), riqueza proposto por Odum (d) e o cálculo de uniformidade proposto por Pielou (J). Foram identiticados 1514 exemplares arbóreos, pertencentes a 29 famílias botânicas, 75 gêneros e 89 espécies, destas, 20 são exóticas e 69 nativas. A espécie mais abundante foi a Handroanthus heptaphyllus (Vell.) Mattos, com relação a origem 78% das espécies foram classificadas como nativas, sendo 56 espécies (62,92%) pertencentes ao domínio fitogeográfico Cerrado e 34 (38,20%) de ocorrência confirmada no Tocantins. O endemismo foi confirmado em 16 espécies (18%), sendo a Parkia platycephala Benth. com maior número de indivíduos (146). Dentre as espécies encontradas, duas aparecem como ameaçadas de extinção: Paubrasilia echinata (Lam.) E. Gagnon, H.C. Lima & G.P. Lewis e Swietenia macrophylla King. Conclui-se que a Praça dos Girassóis apresenta bons índices de diversidade: (H’=4,95) (D’=0,95), riqueza (d=27,67), uniformidade (J=0,76) e fitossanidade (93,20% das árvores saudáveis), além de possuir forte identidade do domínio fitogeográfico em que está inserida. / Squares can be defined as free urban spaces used as public places, which should be prioritized within urban planning, in order to assume its role as a green area, becoming a place of coexistence and reaching its socio-environmental function. The management and management of these areas depend directly on their detailed phytosociological knowledge. From this, the objective of this work was to study the floristic composition of the Square of the Sunflowers in the city of Palmas - TO. The inventory of all the trees present in the Square of the Sunflowers, considering all the arboreal individuals with CAP (chest height circumference, 1,30 m of the soil) equal to or greater than 20 cm were identified for the botanical family, name Scientific name, popular name, origin (native or exotic) as well as phytosanitary status, endemism and threat of extinction. After the data collection, we calculated the diversity index proposed by Shannon-Weiner (H '), the wealth proposed by Odum (d) and the uniformity calculation proposed by Pielou (J). 1514 arboreal specimens were identified, belonging to 29 botanical families, 75 genera and 89 species, of which 20 are exotic and 69 are native. The most abundant species were Handroanthus heptaphyllus (Vell.) Mattos, 78% of the species were classified as native, 56 species (62.92%) belonging to the Cerrado phytogeographic domain and 34 (38.20%) Occurrence confirmed in Tocantins. Endemism was confirmed in 16 species (18%), with Parkia platycephala Benth. with greater number of individuals (146). Among the species found, two appear to be endangered: Paubrasilia echinata (Lam.) E. Gagnon, H.C. Lima & G.P. Lewis and Swietenia macrophylla King. It is concluded that the Square of Sunflowers presents good diversity indexes: (H '= 4.95) (D' = 0.95), richness (d = 27.67), uniformity (J = 0.76) and phytosanitary (93.20% of healthy trees), besides having a strong identity of the phytogeographic domain in which it is inserted.
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Índices espaciais e de diversidade florística das zonas central e residencial central de Imperatriz - MA

Angelo, Dalton Henrique 25 September 2017 (has links)
Considerando a importância das árvores por proporcionar o embelezamento das cidades, a amenização da temperatura local e entre outros fatores, se faz necessário conhecer as espécies que compõem a arborização urbana, o qual pode ser avaliada através do inventário. Após o levantamento florístico é possível medir a qualidade da arborização através de índices de riqueza e/ou índices espaciais das árvores em via pública. Baseado nisso, este estudo teve o objetivo de estudar a arborização urbana em duas regiões centrais da cidade Imperatriz – MA, avaliando riqueza, dominância, equidade e os índices espaciais. Para isso foi feito um inventário total dos indivíduos arbóreos, no qual contemplou-se altura das árvores ≥ 1,5 m, circunferência a altura do peito – CAP, raios e altura da copa, altura da 1ª bifurcação e também dados da malha urbana (largura e comprimento da calçada e vias, distância da árvore para o meio fio, dimensões da área de livre crescimento, altura de fiação e distância entre árvores). Todos os dados coletados foram inseridos em planilhas do programa Microsoft Office Excel onde foram calculados os índices de riqueza: Shannon-Weaver (H’), Odum, Menhinick (Dmn) e Jentsch (QM), índices de diversidade; Simpson (D) McIntosh (dominância); Pielou (J) e Bulla (E) (equidade) e os índices espaciais: ICA, IPO, Déficit, ICV, IDA, IAQC, PCV, IAVT, IAVPB, IAVPV, AVB, IPT, IPE, Sad, Npot e dfut. No estudo obteve-se um total de 228 quadras inventariadas, sendo 145 quadras pertencentes à Zona Central (ZC) e 83 a Zona Residencial Central (ZRC). Foram inventariados 2321 indivíduos distribuídos em 69 espécies e 27 famílias botânicas. Verificou-se também que na área total foram encontradas 24 espécies de origem nativas e 45 exóticas. Através da caracterização florística, observou-se que Licania tomentosa (Benth.) Fritsch e Azadirachta indica A. Juss são as espécies mais frequentes os quais representam 63,77% dos indivíduos. Os índices de riqueza demonstram baixa diversidade de espécies (H’, Dmn e QM), com exceção do índice de Odum. Os índices de dominância evidenciam a baixa diversidade, mostrando que existe alta dominância de poucas espécies. E os índices de equidade mostram haver baixa uniformidade do número de árvores para o número de espécies. No geral, a ZRC demonstrou ser menos diversa, com maior dominância e menor equidade. Quanto aos índices espaciais os resultados demonstram que a ocupação das copas em relação à área de calçadas está abaixo do recomendado, tanto para área total (19,81%) quanto para ZC (25,11%) e ZRC (16,93%), representando um déficit total de 7570 árvores, que representam percentualmente 76,5% de implantação de indivíduos para que houvesse ocupação completa.Quanto à relação do número de habitantes, a arborização de vias e praças de Imperatriz também se encontra inadequada, demonstrada pelo ICV (1,03 m²/habitante), IAVT e IAVPV (0,70 m²/habitante). Portanto, é possível perceber que a área de estudo em Imperatriz possui baixa diversidade, com poucos indivíduos em relação ao número de espécies, demonstra ainda haver desproporção entre a quantidade de árvores por espécie. Por outro lado, a área de estudo apresenta potencial para receber plantio de novas árvores desde que haja planejamento adequado por meio de um plano diretor de arborização urbana. / Considering the importance of trees for providing the beautification of cities, the amelioration of the local temperature and other factors, it is necessary to know the species that make up the urban forestry, which can be assessed through the inventory. After the floristic survey it is possible to measure the quality of the afforestation through indices of wealth and / or spatial indexes of the trees on public roads. Based on this, this study aimed to study the urban forestation in two central regions of the city Imperatriz - MA, evaluating wealth, dominance, equity and spatial indices. To this was done a total inventory of individual trees, which is included tree height ≥ 1.5 m, diameter at breast height - CAP rays and height of the canopy height of 1st data fork and also the urban network (width and length of sidewalk and pathways, distance from the tree to the curb, dimensions of the free growing area, spinning height and distance between trees). All data were entered in Microsoft Office Excel spreadsheet program where wealth indices were calculated: Shannon-Weaver (H '), Odum, Menhinick (Dmn) and Jentsch (QM), diversity indices; Simpson (D) McIntosh (dominance); Evenness (J) and Bulla (E) (fairness) and spatial indexes: ICA, IPO deficit, ICV, IDA IAQC, PCV IAVT, IAVPB, IAVPV, AVB, IPT IPE Sad, and Npot dfut. In the study yielded a total of 228 scheduled blocks, 145 blocks and belonging to the central zone (ZC) and 83 Central Residential (ZRC). 2321 individuals were scheduled distributed in 69 species and 27 botanical families. It was also found that the total area found 24 species of native origin and 45 exotic. Through the floristic characterization, it was observed that Licania tomentosa (Benth.) Fritsch and Azadirachta indica A. Juss s will be the most common species which represents 63.77% of the subjects. The richness indices show low diversity of species (H +, Dmn and QM), except Odum index. The dominance indexes show low diversity, showing that there is a high dominance of few species. And the equity indices show a low uniformity of the number of trees for the number of species. Overall, the ZRC proved to be less diverse, with greater dominance and less equity. As for spatial indexes s results demonstrate that the occupation of the cups with respect to area walkways are below the recommended both pa ra total area (19.81%) and for ZC (25.11%) and ZRC (16.93 %), representing a total deficit of 7570 trees, representing 76.5% percentage deployment individuals so that there was full occupancy. Regarding the number of inhabitants, the arborization of Imperatriz roads and squares is also inadequate, as demonstrated by the ICV (1.03 m² / inhabitant), IAVT and IAVPV (0.70 m² / inhabitant). Therefore, it is possible to notice that the study area in Imperatriz has low diversity, with few individuals in relation to the number of species, it also shows a disproportion between the number of trees per species. On the other hand, the study area has the potential to be planted with new trees provided there is adequate planning through a master plan for urban afforestation.
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Fluxo de gases de efeito estufa em solos do pampa gaúcho sob Silvicultura / Flow of greenhouse gases in soils of the gaucho pampas under silviculture

Stefânia Guedes de Godoi 12 December 2013 (has links)
Submitted by Francine Silva (francine.silva@unipampa.edu.br) on 2019-03-25T14:21:04Z No. of bitstreams: 1 Fluxo de gases de efeito estufa em solos do pampa gaúcho sob Silvicultura.pdf: 731174 bytes, checksum: dbbab000c0161ef5446f57a10d836639 (MD5) / Made available in DSpace on 2019-03-25T14:21:04Z (GMT). No. of bitstreams: 1 Fluxo de gases de efeito estufa em solos do pampa gaúcho sob Silvicultura.pdf: 731174 bytes, checksum: dbbab000c0161ef5446f57a10d836639 (MD5) Previous issue date: 2013-12-12 / A região do Pampa Gaúcho está passando por modificação do tipo de uso do solo, com a inserção da silvicultura em solos de pastagens ou agricultura. No entanto, pouco se conhece sobre o impacto que tal mudança implica no fluxo dos Gases de Efeito Estufa (GEE) nessa região, especialmente em relação aos fluxos de metano (CH4) e óxido nitroso (N2O) do solo. Este estudo teve como objetivo principal avaliar a inserção da silvicultura, com Acacia mearnsii De Wild e Eucalyptus saligna, em áreas de campo nativo e o seu efeito no fluxo CH4 e N2O do solo, e determinar os principais fatores de solo que governam os fluxos destes gases. Dois experimentos foram realizados durante o período de um ano, em povoamentos de Acacia mearnsii De Wild avaliando quatro tratamentos: Acácia (AM), Acácia com retirada manual de serrapilheira (A-s), Acácia recém colhida (AC) e campo nativo (CN); e de Eucalyptus saligna avaliando cinco tratamentos: Eucalipto com quatro anos (E4), Eucalipto com quatro anos com retirada manual da serrapilheira (E4-s), Eucalipto com dois anos (E2), Mata Nativa (MN) e Campo Nativo (CN), utilizando o campo nativo como tratamento de referência. As amostras de ar foram coletadas quinzenalmente pelo método de câmaras estáticas e os teores dos gases foram determinados por cromatografia gasosa. Em cada evento de amostragem de ar, foram avaliados a umidade e os teores de nitrogênio mineral do solo, coletada a serrapilheira e monitorada a temperatura do solo e do ar dentro da câmara. A inserção tanto do eucalipto como de acácia não alterou significativamente os fluxos de CH4 e N2O do solo em relação ao campo nativo adjacente a cada floresta. Os fluxos de N2O foram geralmente baixos, com a maioria dos valores entre –5 e 30 μg N m-2 h-1, provavelmente favorecidas pela baixa precipitação do período avaliado e dos baixos teores de nitrogênio mineral do solo. Houve predomínio de oxidação de CH4 nos solos sob silvicultura no período avaliado, em magnitude similar ao campo nativo. O solo sob eucalipto com dois anos tendeu a emitir mais N2O do que com quatro anos. A colheita da acácia promoveu aumento da emissão de N2O, provavelmente decorrente da maior disponibilidade de nitrogênio mineral no solo para os processos de nitrificação e desnitrificação. Em relação ao CH4, a maior emissão coincidiu com os períodos de temperatura do solo mais elevada, o que é coerente com o aumento da atividade biológica, principalmente em áreas com menor cobertura vegetal. Os teores de carbono orgânico total (COT) e nitrogênio total (NT) do solo sob eucalipto e acácia não diferiram significativamente do campo nativo para a ampla maioria das camadas avaliadas. Somado aos baixos fluxos de CH4 e N2O da silvicultura, o sequestro de carbono via biomassa vegetal e produtos madeireiros sugerem que a mudança de uso do solo com inserção de silvicultura seja uma opção efetiva para a mitigação dos GEE e aumento do sequestro de carbono em áreas da região do Pampa Gaúcho. / The soil use in the region of the Pampa Gaúcho has been modified by of forestation in soils previously used for agriculture or grazing. However, little is known about the impact of this change on greenhouse gases (GHG) fluxes in the soil in that region, mainly regarded to the methane (CH4) and nitrous oxide (N2O). This study aimed to evaluate the effect of the conversion of native grassland to forestry, with Acacia mearnsii De Wild and Eucalyptus saligna, in the Pampa Gaúcho on the soil CH4 and N2O fluxes, besides determining the soil variables that govern these fluxes. Two experiments were conducted for one year, in plantations of Acacia mearnsii De Wild evaluating four treatments: Acacia (AM), Acacia with manual litter removal (A-s), Acacia recently harvested (AH) and native grassland (NG); and Eucalyptus saligna evaluating five treatments: four–year Eucalyptus plantation (E4), four– year Eucalyptus plantation with manual litter removal (E4-l), two–year Eucalyptus plantation (E2), Native forest (NF) and Native grassland (NG), using the native grassland as reference treatment. The air samples were taken biweekly by the method of static chambers and gas concentrations were determined by gas chromatography. In each sampling event, we evaluated the soil moisture and mineral nitrogen content, deposition of litter and monitored the soil and chamber air temperature. The forestation with both eucalyptus and acacia did not alter significantly the soils fluxes of CH4 and N2O in comparison to the native grassland adjacent to each forest. The N2O flux are generally low, with most values ranging from –5 to 30 μg N m-2 h-1, probably favoured by the low rainfall and soil mineral nitrogen levels during the evaluated period. Similarly magnitude to the soil under native grassland, CH4 oxidation predominated in forested soils in the period of the experiment. The soil with two-year old eucalyptus plantation tended to emit more N2O than the four-year plantation. The harvest of acacia increased the soil N2O emission, likely due to the larger availability of mineral N in the soil for the nitrification and denitrification processes. With respect to CH4, the largest emission coincided with periods of higher soil temperature, which is coherent herewith increased of the biological activity, especially in areas with less vegetation cover. The contents of total organic carbon (TOC) and total nitrogen (TN) in soils with eucalyptus and acacia were not significantly different from those observed in native grassland soil for most layers. The low CH4 and N2O emissions from forestry added to the carbon sequestration in the plant biomass and wood products suggests that the change of land use for forestation is an effective option for mitigating the GHG emissions and for increasing the carbon sequestration in areas such as the Pampa Gaúcho.

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