Mesmo com o crescimento da dependência da vida humana em relação aos serviços ecossistêmicos, a taxa de perda de diversidade genética no planeta tem alcançado níveis semelhantes à de grandes eventos de extinção, evidenciando a necessidade de ações para a conservação dos recursos naturais. Em adição aos tradicionais instrumentos de comando e controle para a conservação, os instrumentos econômicos têm tido crescente atenção no mundo nos últimos anos, com especial destaque para os Pagamentos por Serviços Ambientais (PSA). A abordagem de pagamentos de incentivos tem crescido na última década e, apesar das potencialidades que o PSA apresenta, muitos programas falham em incorporar o conhecimento científico em sua execução, sendo esse um dos aspectos que podem acarretar baixo desempenho ambiental e econômico. Neste contexto, o presente projeto buscou avaliar a custo-eficácia do PSA em paisagens fragmentadas. A área de estudo é o estado de São Paulo, cuja fragmentação historicamente ocorre pela expansão agropecuária e pelos diversos impactos decorrentes do grande crescimento populacional em seu território. Foram distribuídos questionários para a obtenção das preferências dos proprietários rurais paulistas em relação aos programas de PSA para restauração de vegetação nativa. Os dados coletados foram relacionados a características socioeconômicas e ambientais e um modelo beta inflacionado de zero misto dentro da classe GAMLSS foi utilizado. Em seguida, o modelo foi utilizado para predizer os resultados para os proprietários não entrevistados e a curva de investimento para diferentes retornos para conservação foi construída. Os resultados apontaram que o PSA é uma alternativa muito custosa frente aos orçamentos ambientais paulistas e que traz poucos benefícios para a restauração no estado de São Paulo. A pesquisa possui uma vertente teórica, pois contribui para a compreensão da adequabilidade do PSA em paisagens fragmentadas, e uma vertente prática, pois explicita a quantidade de recursos necessária para a execução dos programas analisados. / Although the dependence of human activities on ecosystem services has risen in the past decades, the current rate of genetic diversity loss has substantially declined and reached alarming levels. In addition to the traditional command and control approach for the promotion of conservation, growing attention has been given to economic instruments, especially to Payments for Environmental Services (PES). Despite all potentialities of the PES instrument, many programs fail to introduce scientic knowledge in the execution. Such a lack of foundation may result in low environmental and economic performance. The present research aims at evaluating the cost-effectiveness of PES in fragmented landscapes. The study area is the state of São Paulo, which has been fragmented by the agricultural and pasture expansion, and the impacts linked to the large population growth. A survey with dierent PES programs was sent to rural landowners and responses were analyzed and linked to socioeconomic and environmental characteristics through a zero-inflated beta mixed model, within the GAMLSS framework. The model was used to predict enrollment of non-respondents in different PES programs. Finally, the relationship between total area for restoration and the amount of resources needed for each program was compared to the environmental budget of the state of São Paulo. Results show that PES is a very costly alternative that can provide only few results for restoration. The present work has a theoretical orientation, as it contributes to the comprehension of the feasibility of PES programs in fragmented landscapes, and a practical orientation, as it quantifies the amount of resources required by the programs analyzed.

Thesis (PhD(For))--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Widdringtonia whytei is a tropical endemic, fire-adapted pioneer coniferous tree species within natural fire-fragmented Afromontane forest patches in a confined area on Mulanje Mountain in Malawi. Natural and anthropogenic fires within the surrounding fire-prone landscape, insect attacks, and uncontrolled harvesting of mature trees for timber threaten the survival of W. whytei. This study investigated the effects of population fragmentation on the reproductive biology of W. whytei, through four specific studies: effects of population size, tree size and crown position on viable seed output; seed rain variation among population sizes; effects of temperature and light on viability and germination of W. whytei seeds; and the influence of population size on natural regeneration patterns. The study was conducted during 2008 and 2009 on three sites using three W. whytei population sizes: small (≤10 reproductively mature cone-bearing W. whytei trees), medium (11-20 cone-bearing trees) and large (>20 cone-bearing trees). Data were collected using field and laboratory experiments and a review of secondary information. The effect of fragment size and crown position on viable seed output and seed rain pattern was tested with a nested linear mixed model. The influence of stem diameter (dbh) on viable seed output was tested using a separate data set. The variation in seed rain was explored with a generalised linear model (GLM) with a negative binomial link function. Variations in seed germination was analysed with a Weibull regression model. The influence of fragment size on seedling regeneration was tested with a GLM (binary logistic regression). Viable seed output from W. whytei cones was very low (23%) and was not affected by population size, tree diameter or crown position. W. whytei population size influenced seed rain with large fragments having higher seed rain densities. Number of dispersed seeds was generally very low and poorly dispersed. W. whytei cones are semiserotinous and depends on moderate to severe fires for heavy seedfall and wider dispersal. Such fires did not occur during the study period. Temperature is a critical factor for seed germination. Seeds germinate between 15 and 25°C with the optimum at ~ 20°C either under light or dark conditions. Regeneration density followed the seed rain pattern indicating that seed availability is a critical factor for regeneration. Regular cool fires outside the forest patches and along the edges during the hot dry season, and the thick litter layer and shady conditions inside forest patches, caused most of the seedling mortality. This study highlighted the difficulties W. whytei experiences with low output of viable seed, limited seed dispersal and low seedling regeneration in and around forest patches, i.e. factors important for conservation management of this species. It is recommended that gaps with diameter equal to canopy height and occasional spot fires would promote seed dispersal onto exposed mineral soil for rapid seedling establishment and subsequent population growth. Such natural fire disturbance events may show the true seed rain and seedling establishment patterns in this species. / AFRIKAANSE OPSOMMING: Widdringtonia whytei is ‘n tropiese endemiese, vuuraangepaste pionier naaldhoutagtige boomsoort binne die natuurlike vuurgefragmenteerde Afromontane woudkolle binne ‘n beperkte area op Mulanje berg in Malawi. Natuurlike en menslike vure binne die omringende vuurgeneigde landskap, insekaanvalle, en onbeheerde kap van volwasse bome vir hout bedreig die voortbestaan van W. whytei. Hierdie studie het die effek van populasiefragmentasie op die voortplantingsbiologie van W. whytei ondersoek, deur vier spesifieke studies: die effek van populasiegrootte, boomgrootte en kroonposisie op produksie van lewenskragtige saad; saadreënvariasie tussen populasiegroottes; die effek van temperatuur en lig op lewenskragtigheid en ontkieming van W. whytei saad; en die invloed van populasiegrootte op natuurlike verjongingspatrone. Die studie is gedurende 2008 en 2009 uitgevoer op drie groeiplekke met drie W. whytei populasiegroottes: klein (≤10 keëldraende (volwasse) W. whytei bome), medium (11-20 keëldraende bome) en groot (>20 keëldraende bome). Data is versamel in veld- en laboratorium eksperimente asook 'n oorsig van sekondêre inligting. Die invloed van populasie fragmentgrootte en kroonposisie van bome op saadproduksie en die saadreënpatroon is getoets met ‘n geneste liniêre gemengde model. Die invloed van boomstamdeursnee op die produksie van kiemkragtige saad is met ‘n aparte datastel getoets. Die variasie in saadreënpatroon is met 'n algemene liniêre model (GLM) met 'n negatiewe binomiese skakelfunksie getoets. Variasies in ontkiemingspersentasie van sade is met 'n Weibull regressiemodel ontleed. Die invloed van fragmentgrootte op saailingverjonging is met 'n algemene linêre model (binêre logistiese regressie) getoets. Produksie van lewenskragtige saad in W. whytei keëls was baie lag (23%) en was nie deur populasiegrootte, boomstamdeursnee of kroonposisie beïnvloed nie. W. whytei populasiegrootte het saadreën beïnvloed en groot fragmente het groter saadreëndigthede gehad. Die aantal verspreide sade was in die algemeen baie laag en swak versprei. W. whytei keëls is semi-saadhoudend (serotinous) en is afhanklik van matige tot intense vure vir massiewe saadvrystelling en wyer saadverspreiding. Sulke vure het nie gedurende die studieperiode voorgekom nie. Temperatuur is ‘n kritiese factor vir saadontkieming. Sade ontkiem goed tussen 15 en 25°C met die optimum rondom ~ 20°C onder beide lig en donker toestande. Fragmentgrootte het nie die saailingverjonging in W. whytei beïnvloed nie. Verjongingsdigtheid het die saadreënpatroon gevolg, wat daarop dui dat saadbeskikbaarheid ‘n kritiese factor is vir saailingverjonging. Gereelde koel vure buite die woudkolle en langs die woudrand gedurende die droë warm seisoen, en die dik lae blaarval (litter) en skadutoestande binne ‘n woud, het meeste van die saailingmortaliteit veroorsaak. Hierdie studie het die probleme beklemtoon wat W. whytei ondervind met die lae produksie van kiemkragtige saad, saadverspreiding en saailingverjonging binne en rondom die woudkolle, m.a.w. faktore wat belangrik is vir bewaringsbestuur van hierdie boomsoort. Die aanbeveling word gemaak dat kroonopeninge met ‘n deursnee gelyk aan minstens die kroonhoogte, en sporadiese kolbrande binne die woudkolle kan saadverspreiding op blootgestelde minerale grond vir vinnige saailingvestiging en gevolglike populasiegroei bevorder. Sodanige vuurversteuringsgeleenthede mag die werklike patrone in saadreën en saailingvestiging in hierdie species toon.

Amphibians are the most abundant terrestrial vertebrates on Earth. They are crucial in maintaining the transfer of energy and matter from freshwater to terrestrial systems and are also indicators of ecosystem health. Mexico hosts great amphibian diversity with high levels of endemism. Nevertheless, the knowledge of amphibian ecology in the country is at an early stage. This thesis aspires to contribute to the knowledge of Mexican amphibian ecology and to the understanding of the processes underlying amphibian responses to environmental changes. To do so the thesis includes: 1) analyses from fine scales (at landscape level) based on data from two consecutive rainy seasons of fieldwork (nocturnal sampling), in two protected areas in southern Mexico, La Pera and Nahá; 2) at regional scales, analyses based on spatial databases of conservation instruments (i.e. environmental services, governmental, private, and community protected areas, etc.) generated specifically for Mexico; 3) to coarse scales (the whole country), analyses based on ecological niche modelling using the most complete database for Mexican amphibian records and climate layers developed purposely for the country. Thus, the thesis involves different time-scale processes, from ecological to biogeographical. In addition this thesis contains an analysis of the media representation of amphibian biodiversity threats and issues, specifically climate change, based on literature research. I was involved in the process of generating most of the databases used in this thesis. Whilst the main theme of this thesis is amphibian conservation, it also encompasses a wide range of specific subjects. Firstly, foundational knowledge about amphibian conservation is established in Chapter I. Also, the region, Chiapas in southern Mexico, where the fieldwork was carried out for two consecutive years (2009-2010) is described within a historical context and a glossary of terms is presented. In Chapter II, based on one year of fieldwork in two fragmented protected areas (PAs) of different management category, one state and one biosphere reserve, I examine how community structure is related to key features of the environment. The possible effects of governance issues in protected areas and their relationship with the drivers of amphibian metacommunities are also explored. A total of 144 transects were sampled from 33 patches in La Pera and 140 transects from 36 patches in Nahá. In each transect environmental variables were recorded. Partial Canonical Correspondence Analyses (partial CCA) indicated that the drivers of metacommunity patterns vary between the sampled landscapes. Habitat structure explained more of the community variation than either space or weather conditions: > 50% for La Pera and 30% Nahá; but the relationship to geographical space and local climate varied greatly. The differences in relationships among the environmental variables and between them and the amphibian metacommunities finds expression also in the pattern of human exploitation of these areas, which has latterly at least also found expression through differing governance. In Chapter III, the effects of environmental variation on metacommunities structure are explored. Metacommunity theory assumes that emergent properties can be determined that characterise a set of linked communities within a landscape. It follows that change in environmental conditions should generate changes in the metacommunity structure. In La Pera a total of 30 patches were sampled, with a total of 120 transects in 2009, and 133 transects in 2010. In Nahá 31 patches were sampled, with a total of 111 transects in 2009 and 122 transects in 2010. In the analyses of this chapter only transects sampled in both years are included. The total number of individuals increased greatly from 2009 to 2010, but the most abundant species between surveyed years varied slightly, in both areas. In La Pera metacommunity the structure changed from quasi-Clementsian to quasi-Gleasonian, while in Nahá it changed from Clementsian to Gleasonian. CCA show that the variance explained between years was similar. Re-arrangements in the metacommunity structures linked to environmental changes are observed. Results show that amphibian metacommunity structure can change with short environmental changes or disturbances, mainly weather variations from one year to another. This would suggest that metacommunity structures are a dynamic property in fluctuating systems. The aim of Chapter IV is to assess patterns of beta diversity for Mexican terrestrial vertebrates, and explore their relationships with environmental heterogeneity metrics at different spatial scales, identifying the most important surrogates at each spatial scale. The analyses in this chapter are based on the most complete database of Mexican terrestrial vertebrates, comprising distribution maps of 2513 species: 883 resident birds, 344 mammals, 364 amphibians and 811 reptiles. Higher β-diversity values are found along mountain ranges for amphibians, reptiles and mammals, whereas for birds high values are also found on the Mexican Plateau. Results demonstrate that the relationships between β-diversity and the environmental heterogeneity surrogates vary in form and strength across scale and between vertebrate groups. In Chapter V, I set out to characterize at fine scale, alpha and beta diversity patterns for Mexican amphibians and analyze how these patterns might change under a moderate climate-change scenario, and to highlight the overall consequences for amphibian diversity at the country level. The analyses are performed with a climatic envelope modelling approach using MaxEnt and a set of climatic layers developed specifically for Mexico. Models of future scenarios for Mexican amphibian alpha and beta diversity for 2020, 2050, 2080, show that high levels of species extinctions follow if low dispersal capability and high presence thresholds are used, but the overall geographic pattern of beta diversity remains stable. Zones of high beta diversity are associated with topographic formations, whilst the values of beta diversity initially increase, then decline over time under a moderate climate scenario. Extinctions (complete loss of range within country boundaries) are particularly intense during the period 2020–2050. The results imply that heterogeneous zones associated with mountain ranges will remain particularly important for amphibian diversity and thus such areas should be targeted for continued conservation prioritization in the face of climate change scenario. There is an inevitable degree of uncertainty associated with future climate projections and the possible ecological and biogeographical responses. Nevertheless, the climate change projections are typically translated in the media as certain. Chapter VI illustrates the interplay of these competing communication goals, through a review of the representations of the golden toad (Incilius [Bufo] periglenes) in print media and in peer-reviewed literature. The concept of “distanciation”, which means placing a distance between two connected issues (cause and effect), is introduced in this chapter, along with the potential issues that this process may generate in the implementation of conservation strategies. Distanciation is a perception created in the members of the audience of the media, but does not imply a total separation regarding an issue. For example, the audience is interested in the news about climate change effects, but they feel distant because the effects of climate change might be evident within a large time period (i.e. 2050); and although the causes are occurring now, the audience does not see the urgent need to act. Chapter VII represents the first attempt to analyze the status of conservation of some microendemic amphibians in Latin America when some social initiatives (e.g. private and community reserves) are included in the assessment. The efficiency of the existing set of governmental protected areas (PA), and the contribution of social initiatives for land protection of amphibians are evaluated. The chapter shows how the role of land conservation, through social initiatives, is fast becoming a crucial element for the survival of a substantial number of species not protected by state-designated PA. Given the current speed of land use change, we cannot expect to save all species from extinction, and so it must be decided, rather quickly, how to focus the limited resources available to prevent the greatest number of extinctions. In Chapter VIII, a simple conservation triage method is proposed. Using this triage method, the threat status for 145 micro-endemic Mexican amphibian species is evaluated, alongside potential threat abatement responses derived from existing policy instruments and social initiatives. Both indicators are combined to provide broad-scale conservation strategies that would best suit amphibian micro-endemic buffered areas (AMBAs) in Mexico. Results show that almost 25% of the species analysed urgently need field-base verification to confirm their persistence; for the rest, a conservation strategy is developed based on existing conservation instruments. Monitoring populations is essential in order to understand temporal patterns of community change and to better comprehend the underlying processes that shape and maintain biodiversity. These aspects, along with a general discussion focused mainly on the distanciation problem are addressed in Chapter IX.

O desmatamento e a fragmentação decorrentes da expansão das atividades humanas nas paisagens florestais tropicais promovem mudanças na estrutura da paisagem, em geral com perda de florestas antigas para a agricultura ou pastagem, parcialmente compensada regionalmente com a regeneração das florestas secundárias jovens. Tal processo gera paisagens heterogêneas, com florestas secundárias em diferentes estádios de sucessão e perturbação. O estoque de carbono nestas florestas pode, assim, variar muito e essa variação pode ocorrer em diferentes escalas espaciais. O presente estudo buscou entender como as diferentes condições locais e da paisagem contribuem para o estoque de carbono. O estudo foi realizado em florestas secundárias da Mata Atlântica, no Sistema Cantareira (região sudeste do Brasil). A biomassa acima do solo (BAS) foi estimada a partir de dados de inventário florestal e modelos alométricos de biomassa. A fim de testar como a biomassa de uma floresta tropical varia em paisagens antropizadas, foram construídos modelos lineares generalizados (GLM, distribuição Gaussiana) com quatro grupos de variáveis: idade da floresta; perturbações humanas; topografia (declividade e altitude); e estrutura da paisagem. Foram construídos modelos simples, compostos, com e sem interação, além do modelo nulo. O modelo mais plausível foi selecionado pelo critério de Akaike corrigido para pequenas amostras (AICc). Numa escala mais local, a variação da BAS em função da distância à borda foi analisada. A BAS variou amplamente entre os locais de estudo e isso foi parcialmente explicado pelas variáveis explanatórias, uma vez que todos os modelos e variáveis selecionadas foram melhores do que os modelos nulos. O resultado mais surpreendente foi o baixo estoque geral de carbono nas áreas de estudo (30,91 ± 11,00 Mg.ha-1). Os resultados sugerem que este padrão está principalmente relacionado com efeitos de borda e com a influência de fatores diretamente impulsionados pela ocupação humana (como, por exemplo, florestas mais perturbadas, paisagens com baixa cobertura florestal e ocorrência relativa alta de florestas mais jovens). Os resultados indicam ainda que nesta condição de alta perturbação os fatores abióticos, tais como a localização topográfica, podem ter uma importância menor do que seria de esperar por estudos anteriores. Os baixos estoques de carbono e alta variabilidade espacial observada indicam a necessidade de se incorporar estimativas de carbono em escalas espaciais mais finas em programas de mitigação climática e de manutenção de serviços ecossistêmicos em paisagens fragmentadas / Deforestation and fragmentation resulting from the expansion of human activities in tropical forest landscapes promote changes in landscape structure, usually with loss of mature forests for agriculture or pasture, partially offset regionally with the regeneration of young secondary forests. This process generates heterogeneous landscapes with secondary forests in different stages of succession and disturbance. The stock of carbon in these forests can thus vary greatly and this variation may occur at different spatial scales. This study aimed to understand how the different local and landscape conditions contribute to carbon stock. The study was performed in secondary Atlantic Forest fragments in Cantareira System (southeastern Brazil). The above-ground biomass (AGB) was estimated by forest inventory data and allometric biomass models. In order to test how the biomass of a tropical forest varies in disturbed landscapes, generalized linear models (GLM, Gaussian distribution) were constructed with four groups of variables: forest age; human disturbances; topography (terrain slope and elevation); and landscape structure. We constructed simple and compound, with and without interaction, models beyond to the null model. The most plausible model was selected by Akaike criterion corrected for small samples (AICc). On a more local scale, the variation of AGB according to the distance to the edge was analyzed. AGB varied widely among study sites and this was partly explained by the explanatory variables, since data suited better to all models and selected variables than the null model. The most surprising result was the low overall carbon stock in the study areas (30.91 ± 11.00 Mg.ha-1). The results suggest that this pattern is mainly related to edge effects and the influence of factors directly driven by human occupation (e.g. more disturbed forests, landscapes with low forest cover and high relative occurrence of younger forests). The results also indicate that this condition of high disturbance abiotic factors, such as the topographical location, may have less importance than would be expected from previous studies. Low carbon stocks and high spatial variability indicate the need to incorporate in carbon stock estimates a finer spatial scale for climate mitigation and maintenance of ecosystem services programs in fragmented landscapes

O desmatamento e a fragmentação decorrentes da expansão das atividades humanas nas paisagens florestais tropicais promovem mudanças na estrutura da paisagem, em geral com perda de florestas antigas para a agricultura ou pastagem, parcialmente compensada regionalmente com a regeneração das florestas secundárias jovens. Tal processo gera paisagens heterogêneas, com florestas secundárias em diferentes estádios de sucessão e perturbação. O estoque de carbono nestas florestas pode, assim, variar muito e essa variação pode ocorrer em diferentes escalas espaciais. O presente estudo buscou entender como as diferentes condições locais e da paisagem contribuem para o estoque de carbono. O estudo foi realizado em florestas secundárias da Mata Atlântica, no Sistema Cantareira (região sudeste do Brasil). A biomassa acima do solo (BAS) foi estimada a partir de dados de inventário florestal e modelos alométricos de biomassa. A fim de testar como a biomassa de uma floresta tropical varia em paisagens antropizadas, foram construídos modelos lineares generalizados (GLM, distribuição Gaussiana) com quatro grupos de variáveis: idade da floresta; perturbações humanas; topografia (declividade e altitude); e estrutura da paisagem. Foram construídos modelos simples, compostos, com e sem interação, além do modelo nulo. O modelo mais plausível foi selecionado pelo critério de Akaike corrigido para pequenas amostras (AICc). Numa escala mais local, a variação da BAS em função da distância à borda foi analisada. A BAS variou amplamente entre os locais de estudo e isso foi parcialmente explicado pelas variáveis explanatórias, uma vez que todos os modelos e variáveis selecionadas foram melhores do que os modelos nulos. O resultado mais surpreendente foi o baixo estoque geral de carbono nas áreas de estudo (30,91 ± 11,00 Mg.ha-1). Os resultados sugerem que este padrão está principalmente relacionado com efeitos de borda e com a influência de fatores diretamente impulsionados pela ocupação humana (como, por exemplo, florestas mais perturbadas, paisagens com baixa cobertura florestal e ocorrência relativa alta de florestas mais jovens). Os resultados indicam ainda que nesta condição de alta perturbação os fatores abióticos, tais como a localização topográfica, podem ter uma importância menor do que seria de esperar por estudos anteriores. Os baixos estoques de carbono e alta variabilidade espacial observada indicam a necessidade de se incorporar estimativas de carbono em escalas espaciais mais finas em programas de mitigação climática e de manutenção de serviços ecossistêmicos em paisagens fragmentadas / Deforestation and fragmentation resulting from the expansion of human activities in tropical forest landscapes promote changes in landscape structure, usually with loss of mature forests for agriculture or pasture, partially offset regionally with the regeneration of young secondary forests. This process generates heterogeneous landscapes with secondary forests in different stages of succession and disturbance. The stock of carbon in these forests can thus vary greatly and this variation may occur at different spatial scales. This study aimed to understand how the different local and landscape conditions contribute to carbon stock. The study was performed in secondary Atlantic Forest fragments in Cantareira System (southeastern Brazil). The above-ground biomass (AGB) was estimated by forest inventory data and allometric biomass models. In order to test how the biomass of a tropical forest varies in disturbed landscapes, generalized linear models (GLM, Gaussian distribution) were constructed with four groups of variables: forest age; human disturbances; topography (terrain slope and elevation); and landscape structure. We constructed simple and compound, with and without interaction, models beyond to the null model. The most plausible model was selected by Akaike criterion corrected for small samples (AICc). On a more local scale, the variation of AGB according to the distance to the edge was analyzed. AGB varied widely among study sites and this was partly explained by the explanatory variables, since data suited better to all models and selected variables than the null model. The most surprising result was the low overall carbon stock in the study areas (30.91 ± 11.00 Mg.ha-1). The results suggest that this pattern is mainly related to edge effects and the influence of factors directly driven by human occupation (e.g. more disturbed forests, landscapes with low forest cover and high relative occurrence of younger forests). The results also indicate that this condition of high disturbance abiotic factors, such as the topographical location, may have less importance than would be expected from previous studies. Low carbon stocks and high spatial variability indicate the need to incorporate in carbon stock estimates a finer spatial scale for climate mitigation and maintenance of ecosystem services programs in fragmented landscapes

No description available.

Habitat fragmentation can influence the genetics of a population through the direct loss of genetic diversity, and by the genetic processes that occur as a result of small remnant populations or the geographic isolation of populations. I examined the population genetics of two woodland amphibian species in localities with different land-use histories. The wood frog (Rana sylvatica) and the red-backed salamander (Plethodon cinereus) use the same general habitat but differ with respect to a few key life-history characteristics relating to dispersal. I then compared between species the relative influence each land-use scenario had on the population genetic structure. I found that habitat fragmentation affected the population genetics of the two amphibians and did so differently for each species. The differential population genetic response of these two amphibians to habitat fragmentation reinforces the important role of life-history characteristics in how the genetic structure of a population is shaped over time.

Thesis (Ph. D.)--Miami University, Dept. of Zoology, 2004. / Title from second page of PDF document. Document formatted into pages; contains [3], iii, 138 p. : ill. Includes bibliographical references (p.121-138).

Expanding anthropogenic development within the tropical forest biome is driving the loss of an irreplaceable global resource. Mega-diverse tropical forests are vital for regulating the global carbon cycle, and are essential for climate change mitigation. Today, over half of the world’s remaining tropical forest is degraded or regenerating secondary forest. Tropical forests are becoming increasingly fragmented through the expansion of agriculture and roads. Landscape-scale flooding of terrestrial habitats caused by dam construction is an emerging driver of habitat loss and fragmentation. Much attention has been paid to the long-term impacts of tropical forest fragmentation for biodiversity, ecosystem functioning, and carbon emissions. Most of our understanding of the impacts associated with habitat fragmentation originates from systems in which the habitat matrix surrounding remnant forest patches is another, albeit low quality, terrestrial habitat. However, dam-induced habitat fragmentation results in remnant terrestrial biological communities becoming isolated on islands within a water matrix. A water matrix presents the worst-case scenario for remnant habitat fragments. In Chapter 2 I synthesise the results of numerous studies reporting the responses of taxonomic groups to isolation on reservoir land-bridge islands, and uncover a globally-applicable pattern of extinction debt acting upon remnant biological communities on reservoir islands. All islands, regardless of taxonomic group, habitat type, or island area lose species as island isolation time increases. Moreover, I show that contrary to existing ecological theory, once terrestrial habitat becomes isolated within a water matrix, it is effectively too isolated for species losses to be buffered by metapopulation dynamics. Dam development is rapidly expanding in the largest remaining tract of intact tropical forest, the Amazon Basin. In Chapters 3 and 4 I study the Balbina mega-dam system in the central Brazilian Amazon. Here, I use detailed field inventories of trees and lianas on islands and in continuous mainland habitat to determine the impact of landscape-scale habitat fragmentation caused by reservoir creation on these taxonomic groups. I find that islands maintain tree communities at significantly lower densities, richness and diversity compared to continuous forest. Furthermore, tree communities on islands exhibit compositional divergence from those found in mainland continuous forest. Island tree assemblages are dominated by low-wood density species, and may be on a trajectory towards communities characteristic of early successional forests with reduced carbon storage capacity. In contrast, liana assemblages remain compositionally intact and are becoming increasingly dominant relative to trees. Thus, lianas appear robust to many of the negative impacts associated with landscape-scale habitat fragmentation. As insular tree communities continue to degrade through area- and edge-effects, lianas may become a key feature of this archipelagic landscape due to their competitive advantage over trees in disturbed forest habitats. Lianas significantly inhibit tree recruitment and carbon storage. Thus, findings from Chapters 3 and 4 provide strong evidence for additional, and currently unaccounted-for biodiversity and carbon impacts associated with tropical dams. As development of tropical forest regions increases, there is an urgent need to reconcile the need for resources with the need for ecosystem service provision, such as carbon storage, particularly as we attempt to mitigate the impacts of rising atmospheric carbon. Recent studies have shown that secondary tropical forests have the potential to rapidly uptake atmospheric carbon, and act as a powerful tool in climate change mitigation policy. Broad-scale estimates of secondary forest carbon uptake are currently based on above-ground biomass alone. In Chapter 5 I present carbon stock estimates of additional tropical forest carbon pools - soil and dead woody biomass - in secondary forests ranging from 40-120 years. I find that soil fertility (nitrogen concentration) is key in determining carbon storage in secondary forests, and that the stability of carbon stocks held in dead woody biomass increases with secondary forest stand age. I highlight the need to integrate detailed site-specific information into broad-scale predictive models of secondary tropical forest carbon sequestration. This thesis links ecological theory and landscape-scale field inventories, to provide new understanding of the long-term costs of tropical forest fragmentation for biodiversity conservation and carbon storage, and provides further evidence of the important role secondary tropical forests may play in carbon sequestration and climate change mitigation.

Thesis (MScConsEcol (Conservation Ecology and Entomology))--University of Stellenbosch, 2009. / Habitat loss and fragmentation are two of the most pressing threats to biodiversity. Avifaunal diversity and integrity is under immense pressure from these two processes. We have made major advances in our understanding of avifaunal responses to habitat fragmentation, but mostly focus on either fragment scale and/or landscape scale influences of fragmentation on birds. A more comprehensive approach to assessing the impacts of fragmentation was used in this study. The avifaunas of two different geographical regions and bioregions were surveyed and a multiscale analysis of avifaunal responses to fragmentation was attempted. The study sites include the West Coast and East Coast Renosterveld Bioregions in the Cape Floristic Region, South Africa. Assemblage shifts, feeding guild compositional changes, species abundance variation and species persistence were examined at the three spatial scales. Time- and distance-restricted point counts were used to document birds that were directly dependent on the habitat fragments. Forty fragments were selected in each bioregion and a once-off snapshot of the avifaunal richness and diversity was obtained. Results indicate that the avifauna of the two bioregions responded differently to habitat fragmentation. In the East Coast Renosterveld Bioregion, the assemblages, guild composition and species abundances were most accurately predicted by landscape configuration. An assemblage shift occurred at 20 ha fragment area, compared to the 50 ha fragment area threshold of the West Coast Renosterveld Bioregion’s avifauna composition. In the West Coast Renosterveld Bioregion, fragment area was the better predictor of assemblage, guild composition and species abundances. However in both bioregions, the persistence of common species was equally sensitive to area and landscape scale effects.