This study sought to identify critical areas for puma (Puma concolor) movement across the state of Arizona in the American Southwest and to identify those most likely to be impacted by current and future human land uses, particularly expanding urban development and associated increases in traffic volume. Human populations in this region are expanding rapidly, with the potential for urban centers and busy roads to increasingly act as barriers to demographic and genetic connectivity of large-bodied, wide-ranging carnivores such as pumas, whose long-distance movements are likely to bring them into contact with human land uses and whose low tolerance both for and from humans may put them at risk unless opportunities for safe passage through or around human-modified landscapes are present. Brownian bridge movement models based on global positioning system collar data collected during bouts of active movement and linear mixed models were used to model habitat quality for puma movement; then, a wall-to-wall application of circuit theory models was used to produce a continuous statewide estimate of connectivity for puma movement and to identify pinch points, or bottlenecks, that may be most at risk of impacts from current and future traffic volume and expanding development. Rugged, shrub- and scrub-dominated regions were highlighted as those offering high quality movement habitat for pumas, and pinch points with the greatest potential impacts from expanding development and traffic, although widely distributed, were particularly prominent to the north and east of the city of Phoenix and along interstate highways in the western portion of the state. These pinch points likely constitute important conservation opportunities, where barriers to movement may cause disproportionate loss of connectivity, but also where actions such as placement of wildlife crossing structures or conservation easements could enhance connectivity and prevent detrimental impacts before they occur.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-04-15T16:01:38Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE_JULIO_CESAR RODRIGUES MARTINS.pdf: 1441227 bytes, checksum: ca0864964efc66522699bbd9ce67a4bd (MD5) / Made available in DSpace on 2016-04-15T16:01:38Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE_JULIO_CESAR RODRIGUES MARTINS.pdf: 1441227 bytes, checksum: ca0864964efc66522699bbd9ce67a4bd (MD5) Previous issue date: 2015-08-10 / CNPq / Frente aos desafios do aquecimento global e as mudanças climáticas, a sociedade tem como desafio, reduzir as emissões de C à atmosfera. Uma das principais vias de transferência do C à atmosfera são através das mudanças no uso da terra, na qual ecossistemas naturais são convertidos em cultivos agrícolas e pastagens para produção de alimentos e energia. Na região semiárida, a produção vegetal é afetada fortemente pela baixa disponibilidade de água e nutrientes nos solos. Por outro lado, a alta densidade populacional na região, o baixo emprego de tecnologia de produção agrícola e a consequente pressão exercida sobre os agroecossistemas, fazem do manejo do solo uma tarefa complexa. Essa complexidade é aumentada quando se considera as futuras mudanças climáticas projetadas para a região. Diante deste cenário, a utilização de adubos orgânicos (esterco bovino e adubos verdes) ou fertilizantes químicos apresenta-se como a principais fontes para fornecimento de nutrientes para as culturas agrícolas. No entanto, não se sabe qual impacto destes adubos sobre a dinâmica do carbono do solo e culturas e/ou pastagens ao longo do tempo. Sendo assim, é possível que o uso de modelos de simulação, como o Century, capazes de integrar as diversas variáveis ambientais e de manejo dos agroecossistemas, possa contribuir para o melhor entendimento do funcionamento desses sistemas e auxiliar no desenvolvimento de sistemas mais sustentáveis de uso da terra na região. Com isso, o presente trabalho teve como objetivos: 1) Avaliar o impacto das mudanças no uso do solo sobre os estoques de carbono do solo na região semiárida do Nordeste do Brasil; 2) Calibrar o modelo CENTURY para simulação da produtividade de milho e dinâmica do C após adubação orgânica com gliricídia ou esterco bovino Neossolo Regolítico da região semiárida da Paraíba, 3) Calibrar e Validar o modelo Century para simulação dos estoques de C do solo e biomassa da braquiária na Zona da Mata Norte de Pernambuco. Os maiores estoques de carbono orgânico total do solo na região semiárida até a camada de 0-20 cm foram encontrados sob mata nativa. O modelo Century foi capaz de simular as produtividades de palhada e de grãos do milho. O modelo Century 4.5 foi validado para simular a dinâmica do carbono orgânico do solo sob Brachiaria decumbens na zona da mata norte de Pernambuco. / The challenges of global warming and climate change, the company aims to reduce emissions of C to the atmosphere. One of the main routes of the C transfer to the atmosphere is through changes in land use, in which natural ecosystems are converted to agricultural crops and grasslands to produce food and energy. In the semiarid region, crop production is strongly affected by low availability of water and nutrients in soils. On the other hand, the high population density in the region, the low use of agricultural technology and the consequent pressure on agricultural ecosystems, make soil management a complex task. This complexity is increased when considering future climate changes projected for the region. In this scenario, the use of organic fertilizers (animal manure and green manure) or chemical fertilizers presented as the main sources for the supply of nutrients to crops. However, it is unclear what impact these fertilizers on the dynamics of soil carbon and crops and / or pasture over time. Thus, it is possible that the use of simulation models such as the Century, able to integrate the various environmental variables and management of agro-ecosystems, can contribute to a better understanding of the functioning of these systems and assist in developing more sustainable systems of use of land in the region. Thus, this study aimed to: 1) Assess the impact of changes in land use on soil carbon stocks in the semiarid region of Northeast Brazil; 2) Calibrate the CENTURY model to simulate the corn yield and C dynamics after organic fertilization with gliricidia or Entisol manure of semi-arid region of Paraiba, 3) calibrate and validate the Century model for simulation of soil C stocks and biomass Brachiaria in the Zona da Mata Norte of Pernambuco. The biggest stocks of the total soil organic carbon in the semiarid region to 0-20 cm were found in bushland. The Century model was able to simulate the yield of straw and corn grains. The Century model 4.5 was validated to simulate the dynamics of soil organic carbon under Brachiaria decumbens in the area north forest of Pernambuco.

As reliance on energy and water resources grow, so do the concerns regarding their security, especially in terms of availability. A projected rise in population, accompanied by the relentless pursuit of economic growth and increasing climate change, indicate that greater stress will be placed on these same resources. Biofuels are considered to be a viable alternative to fossil fuels and sugarcane-based ethanol has become an important source for energy security in Brazil, its main producer. At the same time, water scarcity issues have prompted the Brazilian government to compose its first National Plan for Water Security. Research shows that change in land use, a prevalent factor in the production of biofuels, can greatly impact water resources through evapotranspiration, suggesting the possibility of the existence of a link between the two events. This study aimed to investigate this phenomenon by assessing how Brazil’s push for energy security through the production of sugarcane-based ethanol could be affecting its water security. The state of Sao Paulo and the lower Cerrado, including the states of Goias, Minas Gerais and Mato Grosso do Sul, were selected as units of analysis since they comprise the largest production area in the country and are located within the La Plata Basin, where water issues have been experienced in the recent past. Results showed impressive increases over the past four decades in the amount of sugarcane and ethanol produced, as well as in the expansion of land used to cultivate sugarcane in both cases. Furthermore, the results disclosed an increasing trend in precipitation deficit for both regions. The discussion revealed that the direct land use change engendered by the expansion of sugarcane cultivation for ethanol cannot be linked to the decrease in availability of rainwater since it did not negatively impact moisture recycling. Indirect deforestation caused by the displacement of pastureland was, however, determined to have contributed to reduced rates of evapotranspiration, negatively impacting continental moisture recycling, which is imperative for levels of rainfall in the La Plata Basin. The study concludes that the increased production of sugarcane-based ethanol in Sao Paulo and in the lower Cerrado, aimed to ensure energy security for Brazil, is negatively affecting its water security through reduced rates of precipitation associated with indirect land use change. More generally, this conclusion provides insights into the energy-water nexus and a better understanding of critical tradeoffs and potentially irreversible risks that can come with isolated solutions to issues pertaining to larger, complex systems. Finally, it stresses the importance of a nexus approach for sustainable development.

abstract: Land-use change has arguably been the largest contributor to the emergence of novel zoonotic diseases within the past century. However, the relationship between patterns of land-use change and the resulting landscape configuration on disease spread is poorly understood as current cross-species disease transmission models have not adequately incorporated spatial features of habitats. Furthermore, mathematical-epidemiological studies have not considered the role that land-use change plays in disease transmission throughout an ecosystem. This dissertation models how a landscape's configuration, examining the amount and shape of habitat overlap, contributes to cross-species disease transmission to determine the role that land-use change has on the spread of infectious diseases. To approach this, an epidemiological model of transmission between a domesticated and a wild species is constructed. Each species is homogeneously mixed in its respective habitat and heterogeneously mixed in the habitat overlap, where cross-species transmission occurs. Habitat overlap is modeled using landscape ecology metrics. This general framework is then applied to brucellosis transmission between elk and cattle in the Greater Yellowstone Ecosystem. The application of the general framework allows for the exploration of how land-use change has contributed to brucellosis prevalence in these two species, and how land management can be utilized to control disease transmission. This model is then extended to include a third species, bison, in order to provide insight to the indirect consequences of disease transmission for a species that is situated on land that has not been converted. The results of this study can ultimately help stakeholders develop policy for controlling brucellosis transmission between livestock, elk, and bison, and in turn, could lead to less disease prevalence, reduce associated costs, and assist in population management. This research contributes novelty by combining landscape ecology metrics with theoretical epidemiological models to understand how the shape, size, and distribution of habitat fragments on a landscape affect cross-species disease transmission. The general framework demonstrates how habitat edge in single patch impacts cross-species disease transmission. The application to brucellosis transmission in the Greater Yellowstone Ecosystem between elk, cattle, and bison is original research that enhances understanding of how land conversion is associated with enzootic disease spread. / Dissertation/Thesis / Doctoral Dissertation Applied Mathematics for the Life and Social Sciences 2020

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(地域研究) / 甲第21904号 / 地博第250号 / 新制||地||92(附属図書館) / 京都大学大学院アジア・アフリカ地域研究研究科グローバル地域研究専攻 / (主査)教授 河野 泰之, 教授 藤倉 達郎, 教授 藤田 幸一, 教授 竹田 晋也 / 学位規則第4条第1項該当 / Doctor of Area Studies / Kyoto University / DGAM

Narragansett Bay, Rhode Island, is a valuable natural resource that suffers summer hypoxic events resulting from over a century of cultural eutrophication. Current efforts to reduce nitrogen loading from wastewater treatment facilities discharging into the Bay and its tributaries hold the promise of working towards ecological restoration. But, the efficacy of these efforts may be limited, or undone, if future changes in climate or land use increase nutrient and sediment loads to the Bay. This study developed a SWAT model of the upper Narragansett Bay watershed to simulate water quantity and quality. The baseline model was calibrated and validated to accurately reflect watershed behavior. I then used the model to simulate water quantity and quality under an altered climate, with an IPCC projected increase in temperature of 3°C and a 10% increase in precipitation by 2080. A second scenario incorporated projected 2080 land use in the absence of climate change. The third scenario combined the climate change and land use change alterations to examine cumulative impacts. A comparison of scenario outputs against the baseline simulation highlighted the expected impacts climate change and land use change will have on the watershed. Both climate change and land use change demonstrated impacts on surface runoff, water yield, PET and ET, streamflow, and loading of sediment, organic N, organic P and nitrate. Climate impacts were much greater than land use impacts, but land use impacts displayed greater regional variation. The results of the combined simulation indicate that future climate and land use change will likely negatively impact the Bay and undermine current efforts at restoration. However, the results also highlight the potential to utilize land use to mitigate some of the impacts of climate change.

Many agricultural landscapes in India are irrigated with wastewater, and it is a common livelihood practice particularly in urban and peri-urban areas. Farmers around urban agglomerations continuously depend on the wastewater released from nearby urban centres. While providing opportunities with respect to water and nutrient supply, irrigating with wastewater has adverse environmental impacts, particularly on the local aquifer systems. Therefore, addressing the wastewater irrigation influence on local aquifer systems is crucial for sustainable groundwater management. The present research demonstrates the impacts of wastewater irrigation, seasonality and spatio-temporal variations in the groundwater quality and its geochemical evolution and mixing processes in different land use and crop settings. The doctoral research aims at understanding the aquifer heterogeneity, land use conditions, groundwater dynamics and contaminant fate and transport in the long-term wastewater irrigation system to develop sustainable and suitable groundwater management strategies. The selected study watershed is located on the banks of Musi River in a peri-urban catchment of the Musi River basin in India. Statistical techniques, land use change modelling and solute flow and transport modelling tools are employed to identify and quantify the linkages between contaminants, agricultural use and environmental variables, particularly those characterizing the groundwater qualities. The research results suggest that concentrations of the major ionic substances increase after the monsoon season, especially in wastewater irrigated areas and the major polluted groundwaters to come from the wastewater irrigated parts of the watershed. Clusters of chemical variables identified indicate that groundwater pollution is highly impacted by mineral interactions and long-term wastewater irrigation. The groundwater geochemistry of the watershed is largely controlled by long-term wastewater irrigation, local rainfall patterns and water-rock interactions. The detected land use changes in the watershed indicate that, as a consequence of urban pressures, agricultural landscapes are being converted into built-up areas and, at the same time, former barren land is converted to agricultural plots. The mapped land use data are used in modelling the aquifer conditions and to observe the groundwater dynamics in the peri-urban environment. The study results provide the basis for sustainable agriculture and groundwater development using the efficient scenarios identified for wastewater irrigation management. The resulting strategies for integrated management of water and waste will contribute to the water security and achieve the respective Sustainable Development Goals (SDGs 2, 3, 6, 11 and 15).

The tropical montane forest of Ecuador is one of the ‘hot spots’ of species diversity. Despite this great species diversity, there are forests in our study area, namely in the Zamora-Chinchipe province in southern Ecuador, which are being depleted at an alarming rate. For example, large areas are being permanently deforested for use as ‘pastureland ’. This development is typically characterized by intensive slash and burn activities for vegetation clearance. After clear cut and slash burning, pasture species are planted of which Setaria sphacelata and Melinis minutiflora, are the most common. However, forest clearing by slash burn for pasture production occurs in the region simultaneously with subsequent invasion of bracken fern (Pteridium arachnoideum) and re-colonization of secondary succession vegetation on abandoned pasture land. In this study, we will examine the effects that the above phenomena have on ecosystems, namely the effects associated with the conversion of natural forestland to pasture land, and the succession that occurs as a result. We will also examine how land use change affects the nutrient status of the soil. This study focuses specifically on the area called the ‘San Francisco Valley’, (3°58’ 30”S latitude, 79°4’ 25”W longitude), which lies between Loja and the Zamora-Chinchipe provinces in Ecuador. Field work for this study was carried out at 1,798 and 2,226 m a.s.l in the following sites: 1) the San Francisco Natural Forest (this area refers to the eastern part of Podocarpus National Park); 2) active pastures Type I (this area refers to the pastureland in front of the San Francisco Scientific Station ECSF, and are pastures that have existed for 50 years or more); 3) active pastures Type II (this area refers to the pastureland in Sabanilla sites, and are pastures that have existed for approximately 17 years); and 4) abandoned pastureland (affected by succession over a period of at least twenty years). Each land-use type consists of five plots of approximately 20 x 20m2. Five points in each plot were then chosen and later sampled (two sub-samples) according to the defined horizons and depth units, namely the organic layer and mineral top soil horizons. Organic layer (only on forest and succession sampling plots) were designated as LOf1, Of2/Oh1 and mineral top soil was sampled to a depth of a 0-10, 10-20, 20-30 cm. To quantify the effects of the impact that land use change has on the chemical characteristics of soil in the selected areas, we analyzed the following bio-elements: the pH value, soil organic carbon (SOC), the total nitrogen (TN), the effective cation exchange capacity (ECEC), as well as stocks of total and available macronutrients. In addition, we examined the biological characteristics such as carbon and nitrogen microbial biomass (MBC, MBN), basal respiration (BR), and nitrogen mineralization (Nmin) in organic layers and top mineral soils (0-30 cm) of the following: the San Francisco Natural Forest, ECSF pastureland, Sabanilla pastureland, and abandoned pastures affected by succession. The main results of this study can be summarised as follows: The soil pH value increased after forest-to-pasture conversion and tended to decrease with soil depth. Moreover, pastureland in the study that was fifty years or more, showed evidence of a decrease in pH values. This decrease in pH value of the soil can be attributed to the reduction in exchangeable cations . However, they still remained higher than the pH values for the forest sites in the study. After the abandonment of pastureland, we observed a re-acidification in the soil of succession sites. This resulted in a decrease of base saturation . On the other hand, the total exchangeable base cation stocks were significantly higher for pasture soils compared with forest and succession soils. This was because of the addition of basic cations by ‘slash and burn activity ’. In this study, we observed that the greater values of soil organic carbon stocks occurred in forest sites. This can be explained by their high SOC value in the organic layer (73.9 Mg ha-1). However, the mineral layer (0 to 30 cm depth) of forest had a lower value than pasture and succession sites. This higher SOC stock of the mineral layer of our pasture sites are partly a result of carbon input from the former standing biomass. Likewise, in the mineral layers, we found that MBC content increases in a similar way to the SOC content. For example, when we compared the MBC content of forests with the pasture sites, we observed that pastures had approximately three times as much MBC. The results of nitrogen stored in the Microbial Biomass (MBN) showed the same tendency as the MBC values. Moreover, for organic layers, the total nitrogen stocks of forest were higher compared to succession sites. On the other hand, for mineral soil (0 to 30 cm depth), nitrogen stocks increased after forest to pasture conversion. This increase is partly due to the burning of aboveground biomass and the subsequent death of roots. Furthermore, the values of nitrogen stocks decreased again in succession sites (4.2 Mg N. ha-1), with similar values those of forests (4.4 Mg N. ha-1 ). Our results show that the slash-and-burn practice leads to a significant increase of P stock. We found that stocks of total phosphorus were significantly higher in the mineral topsoil (0–30 cm) of 50 year-old pastures (ECSF) than in the 17 year-old pastures (Sabanilla). It is important to note that the P stocks in the mineral soil of the abandoned pasture (20 year-old pasture sites) tend to return to forest values (399.9. Kg.ha-1). Nevertheless, the results show very low values of available P on both pastures and succession sites compared with forest sites. In the organic layers, our results show significant differences in the values of basal respiration between forest and succession sites. This indicates that the level of CO2 was greater in the selected forestland due to an increase of organic material. This essentially means that there was an increase of micro-organisms in the soil and subsequently an improved nutrient cycle . For the mineral soil, however, the results only showed a significant difference of 0-10 cm depth in the ECSF pastures and forests. In our study, we did not find any significant differences in the net nitrogen mineralization values in the four studied areas. Nevertheless, the results show that net nitrogen mineralization values decrease systematically according to the depth of the land uses. Summarizing, after the conversion of forest to pasture, there was an increase of the value of bio-elements in the mineral layers at both pasture sites. However, this increase was higher in 50 year old pastures (ECSF) than in the 17 year old pastures (Sabanilla). In addition, we noticed that after 20 years of the abandonment of pastures, most measured soil properties returned to the old-growth forest levels. / El bosque montano tropical de Ecuador es uno de los \"puntos calientes\" de diversidad de especies. Pero el bosque primario en el área de investigación (la provincia de Zamora Chinchipe al Sur de Ecuador) se está perdiendo a un ritmo alarmante. Grandes áreas están siendo permanentemente deforestadas para su uso como tierras de pastoreo. Este proceso se caracteriza por el uso intensivo de fuego para desmonte de la vegetación. Después de la quema y roza, se plantan especies de pastos entre las que Setaria sphacelata y Melinis minutiflora son las más comunes. Sin embargo, la quema y tala del bosque para la conversión a zonas de pastos ocurre simultáneamente con la subsecuente invasión del helecho común (Pteridium arachnoideum), produciéndose. La difusión de esta maleza y la decreciente productividad de los pastos (especialmente Setaria spacelata y Melinis minutiflora) conducen a que las tierras se utilizan en pastoreo hasta que la tierra se agota de nutrientes y luego se abandonan. En este estudio, se examinan los efectos que los fenómenos anteriormente mencionados tienen sobre los ecosistemas; a saber, los efectos asociados a la conversión de bosques naturales en tierras de pastoreo y la posterior sucesión de los pastizales; además de cómo el cambio de uso del suelo afecta el estado nutricional de los suelos del sur del Ecuador. El estudio se sitúa en la zona del valle de San Francisco (3°58’ 30”S latitud, 79°4’ 25”W longitud), entre Loja y Zamora Chinchipe, provincias que se encuentran en el sur de Ecuador. El trabajo de campo se llevó a cabo a una altura entre 1,798 y 2,226 m s.n.m.; en: 1) las áreas de bosque natural San Francisco (esta área se refiere a la parte oriental del Parque Nacional Podocarpus); 2) pasto activos Tipo I (esta área se refiere a los pastos en frente de la Estación Científica San Francisco ECSF, y son pastizales que tienen más de 50 años de edad); 3) pastos activos Tipo II (esta área se refiere a los pastos en los sitios de Sabanilla, y son pastizales que existen desde hace aproximadamente 17 años); y 4) pastos abandonados bajo vegetación de sucesión (más de 20 años de edad). Cada tipo de uso de la tierra consistió en cinco parcelas de aproximadamente 20 x 20 m2; se eligieron cinco puntos en cada parcela y se tomaron muestras (dos sub-muestras) de acuerdo con los horizontes orgánico y mineral. Las capas Orgánicas (solo presentes en el bosque y en los sitios de sucesión) se identificaron como LOf1, Of2/Oh1 y las capas minerales se muestrearon hasta los 0-30 cm de profundidad del suelo. Para cuantificar los efectos del impacto del cambio del uso de la tierra en las características químicas del suelo, se analizó los siguientes bio-elementos: pH, carbono orgánico del suelo (COS), nitrógeno total (Nt), la capacidad de intercambio catiónico efectiva (CICE), así como las reservas del contenido total y disponibilidad de los macro nutrientes. Además, las características biológicas, tales como el carbón (MBC) y nitrógeno (MBN) de la biomasa microbiana, la respiración basal (Rb) y la mineralización de nitrógeno (Nmin) en las capas orgánicas y en la capa mineral del suelo (hasta -30 cm) de los bosques naturales, pastos y pastizales abandonados bajo vegetación de sucesión. Los principales resultados del estudio se describen a continuación: El valor de pH del suelo indica una elevada acidez, después de la conversión de bosque a pastos y tiene una tendencia general a disminuir con la profundidad del suelo, cuando los pastos se hacen más viejos (más de 50 años de edad); los valores de pH del suelo disminuye como consecuencia de la lixiviación de cationes intercambiables, pero siguen siendo superiores a los valores de pH de los sitios del bosque. Tras el abandono de los pastos se observó una re-acidificación en el suelo de los sitios de sucesión, lo que resulta en una disminución de la saturación de bases. Los resultados además indican que las capas orgánicas, especialmente en los suelos de los bosques, almacenan una cantidad importante de potasio, calcio y magnesio. Sin embargo, las reservas totales de cationes básicos intercambiables fueron significativamente mayores en los suelos de los pastizales que en los bosques y que los suelos de sucesión, debido a la adición de cationes básicos producidos por la tala y quema usada en la conversión de bosques a pastizales. En este estudio, se encontró que los mayores valores de reservas de COS se producen en zonas forestales, que se corresponde con un alto valor en la capa orgánica (73,9 Mg C ha-1). Sin embargo, la capa mineral (hasta - 30 cm de profundidad) de los suelos del bosque tiene un valor menor en comparación con los valores de los pastos y sucesión. Este alto contenido de COS en los pastos, se debe en parte al ingreso de carbono desde la biomasa. Asimismo, en las capas minerales, se encontró que el contenido de carbono en biomasa microbiana (CBM) aumenta de una manera similar al contenido de carbono orgánico del suelo (COS). Por ejemplo, cuando comparamos el contenido de CBM de los bosques con los sitios de pastoreo, se observó que los pastos tenían aproximadamente tres veces más MBC. El resultado de nitrógeno almacenado en la biomasa microbiana (NBM) mostró la misma tendencia que los valores de CBM. En las capas orgánicas, las reservas totales de nitrógeno de los bosques fueron mayores en comparación con los sitios de sucesión. Por otro lado, en el suelo mineral (hasta -30 cm de profundidad) las reservas de nitrógeno aumentan después de la conversión de bosques a pastizales. Este incremento es parte debido a la quema de la biomasa superior y de la subsecuente muerte de las raíces. Además, los valores de las reservas de nitrógeno disminuyen de nuevo en los sitios de sucesión (4.2 Mg N. ha-1), a valores similares a las del bosque (4.4 Mg N. ha-1 ). Nuestros resultados muestran que las prácticas de quema y tala incrementan significativamente las reservas de fosforo, encontramos que las reservas de fosforo total fueron significativamente altas en las capas minerales (- 30 cm) de los pastos de 50 años (ECSF), seguido de los pastos de 17 años de edad (Sabanilla). Es importante notar que las reservas de fosforo en las capas minerales de los suelos de pastos abandonados (20 años de edad) tienden a retornar a los valores del bosque (399.9. Kg.ha-1). Sin embargo, los resultados muestran valores muy bajos de fosforo disponible en ambos sitios de pastos y sucesión comparado con el bosque. En las capas orgánicas, los resultados revelan diferencias significativas en los valores de la respiración basal (potencial) entre el bosque y la sucesión. Esto indica que el nivel de CO2 fue mayor en el los sitios de bosque debido a un aumento de la materia orgánica. Esto implica un aumento de los microorganismos en el suelo y, posteriormente, una mejora en el ciclo de nutrientes. En el suelo mineral, los resultados sólo muestran una diferencia significativa en la profundidad de 0-10 cm entre los pastos ECSF con los bosques. En nuestro estudio, no se encontró diferencias significativas en los valores de mineralización neta de nitrógeno entre las cuatro áreas estudiadas. Sin embargo, los resultados muestran que los valores netos de mineralización del nitrógeno disminuyen sistemáticamente con la profundidad en todos los usos de los suelos estudiados. En resumen, después de la conversión de bosques en pastizales, se produjo un incremento del valor de los bio-elementos en las capas minerales de ambos sitios de pastoreo. Sin embargo, este aumento fue mayor en los pastos de 50 años de edad (ECSF) que en los pastos de 17 años de edad (Sabanilla). Además, los resultados muestras que después de 20 años del abandono de los pastos, la mayoría de los parámetros medidos retornan a valores similares a los de los sitios de bosque. / Im globalen Kontext stellt der tropische Bergregenwald in Süd-Ecuador ein „Hotspot“ der Biodiversität dar. Im Untersuchungsgebiet ist die enorme Artenvielfalt durch die massive Zerstörung der natürlichen Waldökosysteme gefährdet. Der Wald wird durch intensive Brandrodung großflächig in Weideland umgewandelt. Im Laufe der Weidenutzung kommt es auf den Weideflächen zu einer zunehmenden Ausbreitung und Dominanz des tropischen Adlerfarns (Pteridium arachnoideum). Die Farnausbreitung und die abnehmende Produktivität der Weidegräser insbesondere von Setaria sphacelata und Melinis minutiflora, führt zum Verlassen der Weiden und zur Etablierung neuer Weideflächen durch fortgesetzte Brandrodung des Naturwaldes. Aufgelassene ehemalige Weideflächen unterliegen einer sekundären Sukzession. Innerhalb dieser Studie wurden die Effekte der Umwandlung des Naturwaldes in Weideland, der Weidenutzung sowie der Wirkungen der sekundären Sukzession nach dem Verlassen unproduktiver Weideflächen auf die Nährstoffsituation der Böden untersucht. Die Untersuchung erfolgte im Gebiet des „San Francisco Tales“, (3°58’ 30”S, 79°4’ 25”W), welches sich zwischen den beiden Provinzen Loja und Zamora-Chinchipe in Ecuador befindet. Feldarbeiten innerhalb dieser Studie wurden in einer Höhe zwischen 1798 und 2225 m NN in den folgenden Bereichen ausgeführt: 1) Naturwald in San Francisco; 2) aktive Weidefläche Typ I (seit circa 50 Jahren in Nutzung); 3) aktive Weidefläche Typ II (seit circa 17 Jahren in Nutzung); und 4) verlassenes Weideland (bestimmt durch sekundäre Sukzession seit mindestens 20 Jahren). Jeder Landnutzungstyp besteht aus fünf Plots mit einer Ausdehnung von circa 20 x 20 m. Fünf Punkte innerhalb eines jeden Plots wurden zur Beprobung ausgewählt. Die organische Auflage (Naturwald, verlassenes Weideland) wurde nach Auflagehorizonten (LOf1 und Of2/Oh) und der Mineralboden nach Tiefenstufen (0-10 cm, 10-20 und 20-30 cm) getrennt beprobt. Um die Effekte und den Einfluss des Landnutzungswandels auf chemische Bodenkennwerte zu quantifizieren, wurden die folgenden Indikatoren untersucht: pH, organischer Kohlenstoffgehalt des Bodens (SOC), Gesamtstickstoff (TN), effektive Kationenaustauschkapazität (CECeff) sowie Vorräte der gesamten und pflanzenverfügbaren Makronährelemente. Zusätzlich wurden bodenbiologische Indikatoren wie Kohlenstoff und Stickstoff der mikrobiellen Biomasse (MBC, MBN), Basalatmung (BR) und Stickstoffmineralisation (Nmin) in den organischen Auflagehorizonten und dem mineralischen Oberboden (0-30 cm) wie folgt untersucht: Naturwald in San Francisco, ECSF Weideflächen, Sabanilla Weideflächen und aufgelassene, von der Sukzession beeinflusste Weiden. Die hauptsächlichen Resultate der Untersuchung können wie folgt zusammengefasst werden: Der pH-Wert des Bodens erhöhte sich nach der Umwandlung von Wald zu Weide und zeigt mit zunehmender Tiefe einen abnehmenden Trend. Darüber hinaus nahmen die pH-Werte von der 17 Jahre alten zur 50 Jahre alten Weide ab. Diese Abnahme kann auf den Rückgang austauschbarer Kationen zurückgeführt werden. Dennoch verblieb der pH-Wert in den 50 Jahre alten Weiden oberhalb des pH-Wertes der im Wald beprobten Flächen. Nach dem Auflassen der Weiden wurde eine erneute Versauerung des Bodens im Stadium der Sukzession beobachtet. Dieser pH-Rückgang wird durch einen Abnahme der Basensättigung begleitet. Auf der anderen Seite waren die Vorräte an austauschbaren Basen der CECeff auf den Weideflächen signifikant über denen der Wald- und Sukzessionsflächen. Ursächlich dafür war die Freisetzung basischer Kationen während der Brandrodung des Naturwaldes. Innerhalb dieser Studie wurden die höchsten Vorräte an Bodenkohlenstoff im Naturwald ermittelt. Das kann durch hohe Vorräte an SOC in der organischen Auflage (73.9 Mg ha-1) erklärt werden. Allerdings waren die Vorräte im Mineralboden (0-30 cm) des Waldes geringer als auf den Weide- und Sukzessionsflächen. Diese höheren SOC-Vorräte im Mineralboden der Weideflächen sind teilweise das Resultat der höheren Kohlenstoffzufuhr durch Reste der oberirdischen Biomasse. Der Gehalt an mikrobiellem Biomassekohlenstoff nahm in ähnlicher Art und Weise wie der des bodenbürtigen organischen Kohlenstoffs zu. Beispielsweise wurde beim Vergleich von MBC und MBN-Gehalten des Waldes mit denen der Weide der dreifache Gehalt in der Weide gefunden. Außerdem waren die Stickstoffvorräte der organischen Auflagen im Wald höher als auf den Sukzessionsflächen. Andererseits nahmen die Stickstoffvorräte nach der Umwandlung von Wald zu Weide im Mineralboden (0-30 cm) zu. Diese Zunahme beruht zum Teil auf dem Abbrennen der oberirdischen Biomasse und dem anschließenden Absterben der Wurzeln. Des Weiteren verringerten sich die Stickstoffvorräte im Stadium der Sukzession (4.2 Mg N ha-1) und glichen sich wieder denen des Waldes (4.4 Mg N ha-1) an. Die Resultate zeigen, dass die Brandrodung zu einem signifikanten Anstieg der Phosphorvorräte führte. Vorräte des Gesamtphosphors waren in den mineralischen Oberböden (0-30 cm) der 50 Jahre alten Weide, gefolgt von der 17 Jahre alten Weide signifikant am höchsten. Zu betonen ist, dass die P-Vorräte im Mineralboden der aufgelassenen Weide dazu tendieren auf Werte des Waldes abzusinken (399.9 kg ha-1). Trotzdem zeigten die Ergebnisse sehr geringe Werte für pflanzenverfügbaren Phosphor in Weide und Sukzession im Vergleich zum Wald. In den organischen Auflagehorizonten wurden signifikante Unterschiede in der mikrobiellen Aktivität (Basalatmung) zwischen Wald und Weide gefunden. Das zeigt, dass das Niveau an C-Mineralisierung in der ausgewählten Waldfläche größer ist, was auf die erhöhte Verfügbarkeit der organischen Substanz zurückgeführt werden kann. Das bedeutet im Wesentlichen einen Anstieg der Mikroorganismen in den Böden und darauffolgend einen verbesserten Nährstoffkreislauf. Für den Mineralboden zeigten die Ergebnisse jedoch nur einen signifikanten Unterschied in einer Tiefe von 0-10 cm zwischen Wald und Weide. Signifikante Unterschiede in der Nettostickstoffmineralisation der vier untersuchten Gebiete konnten nicht gefunden werden. Nichtsdestotrotz zeigten die Ergebnisse, dass die Nettostickstoffmineralisation mit zunehmender Tiefe in den unterschiedlichen Landnutzungen abnimmt. Zusammenfassend kann festgestellt werden, dass nach der Brandrodung die Gehalte an Bioelementen im Mineralboden beider Weideflächen zunahmen. Dieser Anstieg war in den 50 Jahre alten Weideflächen (ECSF) sogar ausgeprägter als in den 17 Jahre alten Weideflächen (Sabanilla). Zusätzlich zeigte sich in den 20 Jahre alten Sukzessionsflächen, dass durch die Regeneration einer organischen Auflage ein positiver Effekt hinsichtlich erhöhter Vorräte an SOC und pflanzenverfügbarem Phosphor festgestellt werden konnte. Diese allmähliche Zunahme an Nährstoffen im Boden der Sukzession setzte sich fort, bis das Ausgangsniveau des Waldes wieder erreicht war.

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