Zonal plant communities of the Ribesalbes-Alcora basin (La Rinconada mine, eastern Spain) during the early Miocene

Zonal plant communities of the Ribesalbes-Alcora basin (La Rinconada mine, eastern Spain) during the early Miocene

Maintaining distances with the engineer: patterns of coexistence in plant communities beyond the patch-bare dichotomy

Two-phase plant communities with an engineer conforming conspicuous patches and affecting the performance and patterns of coexisting species are the norm under stressful conditions. To unveil the mechanisms governing coexistence in these communities at multiple spatial scales, we have developed a new point-raster approach of spatial pattern analysis, which was applied to a Mediterranean high mountain grassland to show how Festuca curvifolia patches affect the local distribution of coexisting species. We recorded 22 111 individuals of 17 plant perennial species. Most coexisting species were negatively associated with F. curvifolia clumps. Nevertheless, bivariate nearest-neighbor analyses revealed that the majority of coexisting species were confined at relatively short distances from F. curvifolia borders (between 0-2 cm and up to 8 cm in some cases). Our study suggests the existence of a fine-scale effect of F. curvifolia for most species promoting coexistence through a mechanism we call 'facilitation in the halo'. Most coexisting species are displaced to an interphase area between patches, where two opposite forces reach equilibrium: attenuated severe conditions by proximity to the F. curvifolia canopy (nutrient-rich islands) and competitive exclusion mitigated by avoiding direct contact with F. curvifolia.

Plant ��-diversity i in human-altered forest ecosystems: the importance of the structural, spatial, and topographical characteristics of stands in patterning plant species assemblages

An understanding of spatial patterns of plant species diversity and the factors that drive those patterns is critical for the development of appropriate biodiversity management in forest ecosystems. We studied the spatial organization of plants species in human- modified and managed oak forests (primarily, Quercus faginea) in the Central Pre- Pyrenees, Spain. To test whether plant community assemblages varied non-randomly across the spatial scales, we used multiplicative diversity partitioning based on a nested hierarchical design of three increasingly coarser spatial scales (transect, stand, region). To quantify the importance of the structural, spatial, and topographical characteristics of stands in patterning plant species assemblages and identify the determinants of plant diversity patterns, we used canonical ordination. We observed a high contribution of ��-diversity to total -diversity and found ��-diversity to be higher and ��-diversity to be lower than expected by random distributions of individuals at different spatial scales. Results, however, partly depended on the weighting of rare and abundant species. Variables expressing the historical management intensities of the stand such as mean stand age, the abundance of the dominant tree species (Q. faginea), age structure of the stand, and stand size were the main factors that explained the compositional variation in plant communities. The results indicate that (1) the structural, spatial, and topographical characteristics of the forest stands have the greatest effect on diversity patterns, (2) forests in landscapes that have different land use histories are environmentally heterogeneous and, therefore, can experience high levels of compositional differentiation, even at local scales (e.g., within the same stand). Maintaining habitat heterogeneity at multiple spatial scales should be considered in the development of management plans for enhancing plant diversity and related functions in human-altered forests

Fertilization Management: Assessing New Techniques and Key Interactions to Increase Crop Yields With Less N2O Emissions

El ��xido nitroso (N2O) es un potente gas de efecto invernadero (GHG) proveniente mayoritariamente de la fertilizaci��n nitrogenada de los suelos agr��colas. Identificar estrategias de manejo de la fertilizaci��n que reduzcan estas emisiones sin suponer un descenso de los rendimientos es vital tanto a nivel econ��mico como medioambiental. Con ese prop��sito, en esta Tesis se han evaluado: (i) estrategias de manejo directo de la fertilizaci��n (inhibidores de la nitrificaci��n/ureasa); y (ii) interacciones de los fertilizantes con (1) el manejo del agua, (2) residuos de cosecha y (3) diferentes especies de plantas. Para conseguirlo se llevaron a cabo meta-an��lisis, incubaciones de laboratorio, ensayos en invernadero y experimentos de campo. Los inhibidores de la nitrificaci��n y de la actividad ureasa se proponen habitualmente como medidas para reducir las p��rdidas de nitr��geno (N), por lo que su aplicaci��n estar��a asociada al uso eficiente del N por parte de los cultivos (NUE). Sin embargo, su efecto sobre los rendimientos es variable. Con el objetivo de evaluar en una primera fase su efectividad para incrementar el NUE y la productividad de los cultivos, se llev�� a cabo un meta-an��lisis. Los inhibidores de la nitrificaci��n dicyandiamide (DCD) y 3,4-dimetilepyrazol phosphate (DMPP) y el inhibidor de la ureasa N-(n-butyl) thiophosphoric triamide (NBPT) fueron seleccionados para el an��lisis ya que generalmente son considerados las mejores opciones disponibles comercialmente. Nuestros resultados mostraron que su uso puede ser recomendado con el fin de incrementar tanto el rendimiento del cultivo como el NUE (incremento medio del 7.5% y 12.9%, respectivamente). Sin embargo, se observ�� que su efectividad depende en gran medida de los factores medioambientales y de manejo de los estudios evaluados. Una mayor respuesta fue encontrada en suelos de textura gruesa, sistemas irrigados y/o en cultivos que reciben altas tasas de fertilizante nitrogenado. En suelos alcalinos (pH ��� 8), el inhibidor de la ureasa NBPT produjo el mayor efecto. Dado que su uso representa un coste adicional para los agricultores, entender las mejores pr��cticas que permitan maximizar su efectividad es necesario para posteriormente realizar comparaciones efectivas con otras pr��cticas que incrementen la productividad de los cultivos y el NUE. En base a los resultados del meta-an��lisis, se seleccion�� el NBPT como un inhibidor con gran potencial. Inicialmente desarrollado para reducir la volatilizaci��n de amoniaco (NH3), en los ��ltimos a��os algunos investigadores han demostrado en estudios de campo un efecto mitigador de este inhibidor sobre las p��rdidas de N2O provenientes de suelos fertilizados bajo condiciones de baja humedad del suelo. Dada la alta variabilidad de los experimentos de campo, donde la humedad del suelo cambia r��pidamente, ha sido imposible entender mecan��sticamente el potencial de los inhibidores de la ureasa (UIs) para reducir emisiones de N2O y su dependencia con respecto al porcentaje de poros llenos de agua del suelo (WFPS). Por lo tanto se realiz�� una incubaci��n en laboratorio con el prop��sito de evaluar cu��l es el principal mecanismo bi��tico tras las emisiones de N2O cuando se aplican UIs bajo diferentes condiciones de humedad del suelo (40, 60 y 80% WFPS), y para analizar hasta qu�� punto el WFPS regula el efecto del inhibidor sobre las emisiones de N2O. Un segundo UI (i.e. PPDA) fue utilizado para comparar el efecto del NBPT con el de otro inhibidor de la ureasa disponible comercialmente; esto nos permiti�� comprobar si el efecto de NBPT es espec��fico de ese inhibidor o no. Las emisiones de N2O al 40% WFPS fueron despreciables, siendo significativamente m��s bajas que las de todos los tratamientos fertilizantes al 60 y 80% WFPS. Comparado con la urea sin inhibidor, NBPT+U redujo las emisiones de N2O al 60% WFPS pero no tuvo efecto al 80% WFPS. La aplicaci��n de PPDA increment�� significativamente las emisiones con respecto a la urea al 80% WFPS mientras que no se encontr�� un efecto significativo al 60% WFPS. Al 80% WFPS la desnitrificaci��n fue la principal fuente de las emisiones de N2O en todos los tratamientos mientras que al 60% tanto la nitrificaci��n como la desnitrificaci��n tuvieron un papel relevante. Estos resultados muestran que un correcto manejo del NBPT puede suponer una estrategia efectiva para mitigar las emisiones de N2O. Con el objetivo de trasladar nuestros resultados de los estudios previos a condiciones de campo reales, se desarroll�� un experimento en el que se evalu�� la efectividad del NBPT para reducir p��rdidas de N y aumentar la productividad durante un cultivo de cebada (Hordeum vulgare L.) en secano Mediterr��neo. Se determin�� el rendimiento del cultivo, las concentraciones de N mineral del suelo, el carbono org��nico disuelto (DOC), el potencial de desnitrificaci��n, y los flujos de NH3, N2O y ��xido n��trico (NO). La adici��n del inhibidor redujo las emisiones de NH3 durante los 30 d��as posteriores a la aplicaci��n de urea en un 58% y las emisiones netas de N2O y NO durante los 95 d��as posteriores a la aplicaci��n de urea en un 86 y 88%, respectivamente. El uso de NBPT tambi��n increment�� el rendimiento en grano en un 5% y el consumo de N en un 6%, aunque ninguno de estos incrementos fue estad��sticamente significativo. Bajo las condiciones experimentales dadas, estos resultados demuestran el potencial del inhibidor de la ureasa NBPT para mitigar las emisiones de NH3, N2O y NO provenientes de suelos arables fertilizados con urea, mediante la ralentizaci��n de la hidr��lisis de la urea y posterior liberaci��n de menores concentraciones de NH4 + a la capa superior del suelo. El riego por goteo combinado con la aplicaci��n dividida de fertilizante nitrogenado disuelto en el agua de riego (i.e. fertirriego por goteo) se considera normalmente una pr��ctica eficiente para el uso del agua y de los nutrientes. Algunos de los principales factores (WFPS, NH4 + y NO3 -) que regulan las emisiones de GHGs (i.e. N2O, CO2 y CH4) y NO pueden ser f��cilmente manipulados por medio del fertirriego por goteo sin que se generen disminuciones del rendimiento. Con ese prop��sito se evaluaron opciones de manejo para reducir estas emisiones en un experimento de campo durante un cultivo de mel��n (Cucumis melo L.). Los tratamientos incluyeron distintas frecuencias de riego (semanal/diario) y tipos de fertilizantes nitrogenados (urea/nitrato c��lcico) aplicados por fertirriego. Fertirrigar con urea en lugar de nitrato c��lcico aument�� las emisiones de N2O y NO por un factor de 2.4 y 2.9, respectivamente (P < 0.005). El riego diario redujo las emisiones de NO un 42% (P < 0.005) pero aument�� las emisiones de CO2 un 21% (P < 0.05) comparado con el riego semanal. Analizando el Poder de Calentamiento global en base al rendimiento as�� como los factores de emisi��n del NO, concluimos que el fertirriego semanal con un fertilizante de tipo n��trico es la mejor opci��n para combinar productividad agron��mica con sostenibilidad medioambiental en este tipo de agroecosistemas. Los suelos agr��colas en las ��reas semi��ridas Mediterr��neas se caracterizan por su bajo contenido en materia org��nica y bajos niveles de fertilidad. La aplicaci��n de residuos de cosecha y/o abonos es una alternativa sostenible y eficiente desde el punto de vista econ��mico para superar este problema. Sin embargo, estas pr��cticas podr��an inducir cambios importantes en las emisiones de N2O de estos agroecosistemas, con impactos adicionales en las emisiones de CO2. En este contexto se llev�� a cabo un experimento de campo durante un cultivo de cebada (Hordeum vulgare L.) bajo condiciones Mediterr��neas para evaluar el efecto de combinar residuos de cosecha de ma��z con distintos inputs de fertilizantes nitrogenados (pur��n de cerdo y/o urea) en estas emisiones. La incorporaci��n de rastrojo de ma��z increment�� las emisiones de N2O durante el periodo experimental un 105%. Sin embargo, las emisiones de NO se redujeron significativamente en las parcelas enmendadas con rastrojo. La sustituci��n parcial de urea por pur��n de cerdo redujo las emisiones netas de N2O un 46 y 39%, con y sin incorporaci��n de residuo de cosecha respectivamente. Las emisiones netas de NO se redujeron un 38 y un 17% para estos mismos tratamientos. El ratio molar DOC:NO3 - demostr�� predecir consistentemente las emisiones de N2O y NO. El efecto principal de la interacci��n entre el fertilizante nitrogenado y el rastrojo de ma��z se dio a los 4-6 meses de su aplicaci��n, generando un aumento del N2O y una disminuci��n del NO. La sustituci��n de urea por pur��n de cerdo puede considerarse una buena estrategia de manejo dado que el uso de este residuo org��nico redujo las emisiones de ��xidos de N. Los pastos de todo el mundo proveen numerosos servicios ecosist��micos pero tambi��n suponen una importante fuente de emisi��n de N2O, especialmente en respuesta a la deposici��n de N proveniente del ganado mientras pasta. Para explorar el papel de las plantas como mediadoras de estas emisiones, se analiz�� si las emisiones de N2O dependen de la riqueza en especies herb��ceas y/o de la composici��n espec��fica de especies, en ausencia y presencia de una deposici��n de orina. Las hip��tesis fueron: 1) las emisiones de N2O tienen una relaci��n negativa con la productividad de las plantas; 2) mezclas de cuatro especies generan menores emisiones que monocultivos (dado que su productividad ser�� mayor); 3) las emisiones son menores en combinaciones de especies con distinta morfolog��a radicular y alta biomasa de ra��z; y 4) la identidad de las especies clave para reducir el N2O depende de si hay orina o no. Se establecieron monocultivos y mezclas de dos y cuatro especies comunes en pastos con rasgos funcionales divergentes: Lolium perenne L. (Lp), Festuca arundinacea Schreb. (Fa), Phleum pratense L. (Php) y Poa trivialis L. (Pt), y se cuantificaron las emisiones de N2O durante 42 d��as. No se encontr�� relaci��n entre la riqueza en especies y las emisiones de N2O. Sin embargo, estas emisiones fueron significativamente menores en ciertas combinaciones de especies. En ausencia de orina, las comunidades de plantas Fa+Php actuaron como un sumidero de N2O, mientras que los monocultivos de estas especies constituyeron una fuente de N2O. Con aplicaci��n de orina la comunidad Lp+Pt redujo (P < 0.001) las emisiones de N2O un 44% comparado con los monocultivos de Lp. Las reducciones de N2O encontradas en ciertas combinaciones de especies pudieron explicarse por una productividad total mayor y por una complementariedad en la morfolog��a radicular. Este estudio muestra que la composici��n de especies herb��ceas es un componente clave que define las emisiones de N2O de los ecosistemas de pasto. La selecci��n de combinaciones de plantas espec��ficas en base a la deposici��n de N esperada puede, por lo tanto, ser clave para la mitigaci��n de las emisiones de N2O. ABSTRACT Nitrous oxide (N2O) is a potent greenhouse gas (GHG) directly linked to applications of nitrogen (N) fertilizers to agricultural soils. Identifying mitigation strategies for these emissions based on fertilizer management without incurring in yield penalties is of economic and environmental concern. With that aim, this Thesis evaluated: (i) the use of nitrification and urease inhibitors; and (ii) interactions of N fertilizers with (1) water management, (2) crop residues and (3) plant species richness/identity. Meta-analysis, laboratory incubations, greenhouse mesocosm and field experiments were carried out in order to understand and develop effective mitigation strategies. Nitrification and urease inhibitors are proposed as means to reduce N losses, thereby increasing crop nitrogen use efficiency (NUE). However, their effect on crop yield is variable. A meta-analysis was initially conducted to evaluate their effectiveness at increasing NUE and crop productivity. Commonly used nitrification inhibitors (dicyandiamide (DCD) and 3,4-dimethylepyrazole phosphate (DMPP)) and the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) were selected for analysis as they are generally considered the best available options. Our results show that their use can be recommended in order to increase both crop yields and NUE (grand mean increase of 7.5% and 12.9%, respectively). However, their effectiveness was dependent on the environmental and management factors of the studies evaluated. Larger responses were found in coarse-textured soils, irrigated systems and/or crops receiving high nitrogen fertilizer rates. In alkaline soils (pH ��� 8), the urease inhibitor NBPT produced the largest effect size. Given that their use represents an additional cost for farmers, understanding the best management practices to maximize their effectiveness is paramount to allow effective comparison with other practices that increase crop productivity and NUE. Based on the meta-analysis results, NBPT was identified as a mitigation option with large potential. Urease inhibitors (UIs) have shown to promote high N use efficiency by reducing ammonia (NH3) volatilization. In the last few years, however, some field researches have shown an effective mitigation of UIs over N2O losses from fertilized soils under conditions of low soil moisture. Given the inherent high variability of field experiments where soil moisture content changes rapidly, it has been impossible to mechanistically understand the potential of UIs to reduce N2O emissions and its dependency on the soil water-filled pore space (WFPS). An incubation experiment was carried out aiming to assess what is the main biotic mechanism behind N2O emission when UIs are applied under different soil moisture conditions (40, 60 and 80% WFPS), and to analyze to what extent the soil WFPS regulates the effect of the inhibitor over N2O emissions. A second UI (i.e. PPDA) was also used aiming to compare the effect of NBPT with that of another commercially available urease inhibitor; this allowed us to see if the effect of NBPT was inhibitor-specific or not. The N2O emissions at 40% WFPS were almost negligible, being significantly lower from all fertilized treatments than that produced at 60 and 80% WFPS. Compared to urea alone, NBPT+U reduced the N2O emissions at 60% WFPS but had no effect at 80% WFPS. The application of PPDA significantly increased the emissions with respect to U at 80% WFPS whereas no significant effect was found at 60% WFPS. At 80% WFPS denitrification was the main source of N2O emissions for all treatments. Both nitrification and denitrification had a determinant role on these emissions at 60% WFPS. These results suggest that adequate management of the UI NBPT can provide, under certain soil conditions, an opportunity for N2O mitigation. We translated our previous results to realistic field conditions by means of a field experiment with a barley crop (Hordeum vulgare L.) under rainfed Mediterranean conditions in which we evaluated the effectiveness of NBPT to reduce N losses and increase crop yields. Crop yield, soil mineral N concentrations, dissolved organic carbon (DOC), denitrification potential, NH3, N2O and nitric oxide (NO) fluxes were measured during the growing season. The inclusion of the inhibitor reduced NH3 emissions in the 30 d following urea application by 58% and net N2O and NO emissions in the 95 d following urea application by 86 and 88%, respectively. NBPT addition also increased grain yield by 5% and N uptake by 6%, although neither increase was statistically significant. Under the experimental conditions presented here, these results demonstrate the potential of the urease inhibitor NBPT in abating NH3, N2O and NO emissions from arable soils fertilized with urea, slowing urea hydrolysis and releasing lower concentrations of NH4 + to the upper soil layer. Drip irrigation combined with split application of N fertilizer dissolved in the irrigation water (i.e. drip fertigation) is commonly considered best management practice for water and nutrient efficiency. Some of the main factors (WFPS, NH4 + and NO3 -) regulating the emissions of GHGs (i.e. N2O, carbon dioxide (CO2) and methane (CH4)) and NO can easily be manipulated by drip fertigation without yield penalties. In this study, we tested management options to reduce these emissions in a field experiment with a melon (Cucumis melo L.) crop. Treatments included drip irrigation frequency (weekly/daily) and type of N fertilizer (urea/calcium nitrate) applied by fertigation. Crop yield, environmental parameters, soil mineral N concentrations, N2O, NO, CH4, and CO2 fluxes were measured during the growing season. Fertigation with urea instead of calcium nitrate increased N2O and NO emissions by a factor of 2.4 and 2.9, respectively (P < 0.005). Daily irrigation reduced NO emissions by 42% (P < 0.005) but increased CO2 emissions by 21% (P < 0.05) compared with weekly irrigation. Based on yield-scaled Global Warming Potential as well as NO emission factors, we conclude that weekly fertigation with a NO3 --based fertilizer is the best option to combine agronomic productivity with environmental sustainability. Agricultural soils in semiarid Mediterranean areas are characterized by low organic matter contents and low fertility levels. Application of crop residues and/or manures as amendments is a cost-effective and sustainable alternative to overcome this problem. However, these management practices may induce important changes in the nitrogen oxide emissions from these agroecosystems, with additional impacts on CO2 emissions. In this context, a field experiment was carried out with a barley (Hordeum vulgare L.) crop under Mediterranean conditions to evaluate the effect of combining maize (Zea mays L.) residues and N fertilizer inputs (organic and/or mineral) on these emissions. Crop yield and N uptake, soil mineral N concentrations, dissolved organic carbon (DOC), denitrification capacity, N2O, NO and CO2 fluxes were measured during the growing season. The incorporation of maize stover increased N2O emissions during the experimental period by c. 105 %. Conversely, NO emissions were significantly reduced in the plots amended with crop residues. The partial substitution of urea by pig slurry reduced net N2O emissions by 46 and 39 %, with and without the incorporation of crop residues respectively. Net emissions of NO were reduced 38 and 17 % for the same treatments. Molar DOC:NO3 - ratio was found to be a robust predictor of N2O and NO fluxes. The main effect of the interaction between crop residue and N fertilizer application occurred in the medium term (4-6 month after application), enhancing N2O emissions and decreasing NO emissions as consequence of residue incorporation. The substitution of urea by pig slurry can be considered a good management strategy since N2O and NO emissions were reduced by the use of the organic residue. Grassland ecosystems worldwide provide many important ecosystem services but they also function as a major source of N2O, especially in response to N deposition by grazing animals. In order to explore the role of plants as mediators of these emissions, we tested whether and how N2O emissions are dependent on grass species richness and/or specific grass species composition in the absence and presence of urine deposition. We hypothesized that: 1) N2O emissions relate negatively to plant productivity; 2) four-species mixtures have lower emissions than monocultures (as they are expected to be more productive); 3) emissions are lowest in combinations of species with diverging root morphology and high root biomass; and 4) the identity of the key species that reduce N2O emissions is dependent on urine deposition. We established monocultures and two- and four-species mixtures of common grass species with diverging functional traits: Lolium perenne L. (Lp), Festuca arundinacea Schreb. (Fa), Phleum pratense L. (Php) and Poa trivialis L. (Pt), and quantified N2O emissions for 42 days. We found no relation between plant species richness and N2O emissions. However, N2O emissions were significantly reduced in specific plant species combinations. In the absence of urine, plant communities of Fa+Php acted as a sink for N2O, whereas the monocultures of these species constituted a N2O source. With urine application Lp+Pt plant communities reduced (P < 0.001) N2O emissions by 44% compared to monocultures of Lp. Reductions in N2O emissions by species mixtures could be explained by total biomass productivity and by complementarity in root morphology. Our study shows that plant species composition is a key component underlying N2O emissions from grassland ecosystems. Selection of specific grass species combinations in the context of the expected nitrogen deposition regimes may therefore provide a key management practice for mitigation of N2O emissions.

Changes in spatial point patterns of pioneer woody plants across a large tropical landslide

We assessed whether the relative importance of positive and negative interactions in early successional communities varied across a large landslide on Casita Volcano (Nicaragua). We tested several hypotheses concerning the signatures of these processes in the spatial patterns of woody pioneer plants, as well as those of mortality and recruitment events, in several zones of the landslide differing in substrate stability and fertility, over a period of two years (2001 and 2002). We identified all woody individuals with a diameter >1 cm and mapped them in 28 plots measuring 10 �� 10-m. On these maps, we performed a spatial point pattern analysis using univariate and bivariate pair-correlation functions; g (r) and g12 (r), and pairwise differences of univariate and bivariate functions. Spatial signatures of positive and negative interactions among woody plants were more prevalent in the most and least stressful zones of the landslide, respectively. Natural and human-induced disturbances such as the occurrence of fire, removal of newly colonizing plants through erosion and clearcutting of pioneer trees were also identified as potentially important pattern-creating processes. These results are in agreement with the stress-gradient hypothesis, which states that the relative importance of facilitation and competition varies inversely across gradients of abiotic stress. Our findings also indicate that the assembly of early successional plant communities in large heterogeneous landslides might be driven by a much larger array of processes than previously thought.

Deforestaci��n y P��rdida de h��bitat en Bosques de monta��a en la Cuenca alta del R��o Zamora (Loja, Ecuador)

Los bosques h��medos de monta��a se encuentran reconocidos como uno de los ecosistemas m��s amenazados en el mundo, llegando inclusive a ser considerado como un ���hotspot��� por su alta diversidad y endemismo. La acelerada p��rdida de cobertura vegetal de estos bosques ha ocasionado que, en la actualidad, se encuentren restringidos a una peque��a fracci��n de su ��rea de distribuci��n hist��rica. Pese a esto, los estudios realizados sobre cual es efecto de la deforestaci��n, fragmentaci��n, cambios de uso de suelo y su efecto en las comunidades de plantas presentes en este tipo de vegetaci��n a��n son muy escuetos, en comparaci��n a los realizados con sus similares amaz��nicos. En este trabajo, el cual se encuentra dividido en seis cap��tulos, abordaremos los siguientes objetivos: a) Comprender cu��l es la din��mica que han seguido los diferentes tipos de bosques montanos andinos de la cuenca del Rio Zamora, Sur de Ecuador durante entre 1976 y 2002. b) Proveer de evidencia de las tasas de deforestaci��n y fragmentaci��n de todos los tipos diferentes de bosques montanos andinos presentes en la cuenca del Rio Zamora, Sur de Ecuador entre 1976 y 2002. c) Determinar qu�� factores inducen a la fragmentaci��n de bosques de monta��a en la cuenca alta del r��o Zamora entre 1976 y 2002. d) Determinar cu��les son y c��mo afectan los factores ambientales y socioecon��micos a la din��mica de la deforestaci��n y regeneraci��n (p��rdida y recuperaci��n del h��bitat) sufrida por los bosques de monta��a dentro de la zona de estudio y e) Determinar si la deforestaci��n y fragmentaci��n act��an sobre la diversidad y estructura de las comunidades de tres tipos de organismos (comunidades de ��rboles, comunidades de l��quenes ep��fitos y comunidades de hep��ticas ep��fitas). Este estudio se centr�� en el cuenca alta del r��o Zamora, localizada al sur de Ecuador entre las coordenadas 3�� 00�� 53��� a 4�� 20�� 24.65��� de latitud sur y 79�� 49��58��� a 78�� 35�� 38��� de longitud oeste, que cubre alrededor de 4300 km2 de territorio situado entre las capitales de las provincias de Loja y Zamora-Chinchipe. Con objeto de predecir la din��mica futura de la deforestaci��n en la regi��n de Loja y c��mo se ver��n afectados los diferentes tipos de h��bitat, as�� como para detectar los factores que m��s influyen en dicha din��mica, se han construido modelos basados en la historia de la deforestaci��n derivados de fotograf��as a��reas e im��genes satelitales de tres fechas (1976, 1989 y 2002). La cuantificaci��n de la deforestaci��n se realiz�� mediante la tasa de inter��s compuesto y para la caracterizaci��n de la configuraci��n espacial de los fragmentos de bosque nativo se calcularon ��ndices de paisaje los cuales fueron calculados utilizando el programa Fragstats 3.3. Se ha clasificado el recubrimiento del terreno en forestal y no forestal y se ha modelado su evoluci��n temporal con Modelos Lineales Generalizados Mixtos (GLMM), empleando como variables explicativas tanto variables ambientales espacialmente expl��citas (altitud, orientaci��n, pendiente, etc) como antr��picas (distancia a zonas urbanizadas, deforestadas, caminos, entre otras). Para medir el efecto de la deforestaci��n sobre las comunidades modelo (de ��rboles, l��quenes y hep��ticas) se monitorearon 11 fragmentos de vegetaci��n de distinto tama��o: dos fragmentos de m��s de cien hect��reas, tres fragmentos de entre diez y noventa ha y seis fragmentos de menos de diez hect��reas. En ellos se instalaron un total de 38 transectos y 113 cuadrantes de 20 x 20 m a distancias que se alejaban progresivamente del borde en 10, 40 y 80 m. Nuestros resultados muestran una tasa media anual de deforestaci��n del 1,16% para todo el per��odo de estudio, que el tipo de vegetaci��n que m��s alta tasa de destrucci��n ha sufrido, es el p��ramo herb��ceo, con un 2,45% anual. El an��lisis de los patrones de fragmentaci��n determin�� un aumento en 2002 de m��s del doble de fragmentos presentes en 1976, lo cual se repite en el an��lisis del ��ndice de densidad promedio. El ��ndice de proximidad media entre fragmentos muestra una reducci��n progresiva de la continuidad de las ��reas forestadas. Si bien las formas de los fragmentos se han mantenido bastante similares a lo largo del per��odo de estudio, la conectividad entre estos ha disminuido en un 84%. Por otro lado, de nuestros an��lisis se desprende que las zonas con mayor probabilidad de deforestarse son aquellas que est��n cercanas a zonas previamente deforestadas; la cercan��a a las v��as tambi��n influye significativamente en la deforestaci��n, causando un efecto directo en la composici��n y estructura de las comunidades estudiadas, que en el caso de los ��rboles viene mediado por el tama��o del fragmento y en el caso del componente ep��fito (hep��ticas y l��quenes), viene mediado tanto por el tama��o del fragmento como por la distancia al borde del mismo. Se concluye la posibilidad de que, de mantenerse esta tendencia, este tipo de bosques desaparecer�� en corto tiempo y los servicios ecosist��micos que prestan, se ver��n seriamente comprometidos. ABSTRACT Mountain rainforests are recognized as one of the most threatened ecosystems in the world, and have even come to be considered as a ���hotspot��� due to their high degree of diversity and endemism. The accelerated loss of plant cover of these forests has caused them to be restricted today to a small fraction of their area of historic distribution. In spite of this, studies done on the effect of deforestation, fragmentation, changes in soil use and their effect on the plant communities present in this type of vegetation are very brief compared to those done on their analogues in the Amazon region. In this study, which is divided into six chapters, we will address the following objectives: a) To understand what the dynamic followed by the different types of Andean mountain forests in the Zamora River watershed of southern Ecuador has been between 1976 and 2002. b) To provide evidence of the rates of deforestation and fragmentation of all the different types of Andean mountain forests existing in the upper watershed of the Zamora River between 1976 and 2002. c) To determine the factors that induces fragmentation of all different types of Andean mountain forests existing in the upper watershed of the Zamora River between 1976 and 2002. d) To determine what the environmental and anthropogenic factors are driving the dynamic of deforestation and regeneration (loss and recuperation of the habitat) suffered by the mountain forests in the area of the study and e) To determine if the deforestation and fragmentation act upon the diversity and structure of three model communities: trees, epiphytic lichens and epiphytic liverworts. This study is centered on the upper Zamora River watershed, located in southern Ecuador between 3�� 00�� 53��� and 4�� 20�� 24.65 south latitude and 79�� 49�� 58��� to 78�� 35�� 38��� west longitude, and covers around 4,300 km2 of territory located between Loja and Zamora-Chinchipe provinces. For the purpose of predicting the future dynamic of deforestation in the Loja region and how different types of habitats will be affected, as well as detecting the environmental and socioeconomic factors that influence landscape dynamics, models were constructed based on deforestation history, derived from aerial photographs and satellite images for three dates (1976, 1989 and 2002). Quantifying the deforestation was done using the compound interest rate; to characterize the spatial configuration of fragments of native forest, landscape indices were calculated with Fragstats 3.3 program. Land cover was classified as forested and not forested and its evolution over time was modeled with Generalized Linear Mixed Models (GLMM), using spatially explicit environmental variables (altitude, orientation, slope, etc.) as well as anthropic variables (distance to urbanized, deforested areas and roads, among others) as explanatory variables. To measure the effects of fragmentation on three types of model communities (forest trees and epiphytic lichen and liverworts), 11 vegetation fragments of different sizes were monitored: two fragments of more than one hundred hectares, three fragments of between ten and ninety ha and six fragments of fewer than ten hectares . In these fragments, a total of 38 transects and 113 20 x 20 m quadrats were installed at distances that progressively moved away from the edge of the fragment by 10, 40 and 80 m. Our results show an average annual rate of deforestation of 1.16% for the entire period of the study, and that the type of vegetation that suffered the highest rate of destruction was grassy paramo, with an annual rate of 2.45%. The analysis of fragmentation patterns determined the number of fragments in 2002 more than doubled the number of fragments present in 1976, and the same occurred for the average density index. The variation of the average proximity index among fragments showed a progressive reduction of the continuity of forested areas. Although fragment shapes have remained quite similar over the period of the study, connectivity among them has diminished by 84%. On the other hand, it emerged from our analysis that the areas of greatest probability of deforestation were those that are close to previously deforested areas; proximity to roads also significantly favored the deforestation causing a direct effect on the composition of our model communities, that in the case of forest trees is determined by the size of the fragment, and in the case of the epiphyte communities (liverworts and lichens), is determined, by the size of the fragment as well as the distance to edge. A subject under discussion is the possibility that if this tendency continues, this type of forest will disappear in a short time, and the ecological services it provides, will be seriously endangered.

Diversidad funcional y diversidad filogen��tica en los bosques secos del sur del Ecuador

El concepto tradicional de reglas de ensamblaje refleja la idea de que las especies no co-ocurren al azar sino que est��n restringidos en su co-ocurrencia por la competencia interespec��fica o por un filtrado ambiental. En est�� tesis abord�� la importancia de los procesos que determinan el ensamble de la comunidad en la estructuraci��n de los Bosques Secos en el Sur del Ecuador. Este estudio se realiz�� en la regi��n biogeogr��fica Tumbesina, donde se encuentra la mayor concentraci��n de bosques secos tropicales bien conservados del sur de Ecuador, y que constituyen una de las ��reas de endemismo m��s importantes del mundo. El clima se caracteriza por una estaci��n seca que va desde mayo a diciembre y una estaci��n lluviosa de enero a abril, su temperatura anual var��a entre 20��C y 26��C y una precipitaci��n promedio anual entre 300 y 700 mm. Mi primer tema fue orientado a evaluar si la distribuci��n de los rasgos funcionales a nivel comunitario es compatible con la existencia de un filtro ambiental (filtrado del h��bitat) o con la existencia de un proceso de limitaci��n de la semejanza funcional impuesta por la competencia inter-espec��fica entre 58 especies de plantas le��osas repartidas en 109 parcelas (10x50m). Para ello, se analiz�� la distribuci��n de los valores de cinco rasgos funcionales (altura m��xima, densidad de la madera, ��rea foliar espec��fica, tama��o de la hoja y de masa de la semilla), resumida mediante varios estad��sticos (rango, varianza, kurtosis y la desviaci��n est��ndar de la distribuci��n de distancias funcionales a la especies m��s pr��xima) y se compar�� con la distribuci��n esperada bajo un modelo nulo con ausencia de competencia. Los resultados obtenidos apoyan que tanto el filtrado ambiental como la limitaci��n a la semejanza afectan el ensamble de las comunidades vegetales de los bosques secos Tumbesinos. Un segundo tema fue identificar si la diversidad funcional est�� condicionada por los gradientes ambientales, y en concreto si disminuye en los ambientes m��s estresantes a causa del filtrado ambiental, y si por el contrario aumenta en los ambientes m��s benignos donde la competencia se vuelve m��s importante, teniendo en cuenta las posibles modificaciones a este patr��n general a causa de las interacciones de facilitaci��n. Para abordar este estudio analizamos tanto las variaciones en la diversidad funcional (respecto a los de los cinco rasgos funcionales empleados en el primer cap��tulo de la tesis) como las variaciones de diversidad filogen��tica a lo largo de un gradiente de estr��s clim��tico en los bosques tumbesinos, y se contrastaron frente a las diversidades esperadas bajo un modelo de ensamblaje completamente aleatorio de la comunidad. Los an��lisis mostraron que tan s��lo la diversidad de tama��os foliares sigui�� el patr��n de variaci��n esperado, disminuyendo a medida que aument�� el estr��s abi��tico mientras que ni el resto de rasgos funcionales ni la diversidad funcional multivariada ni la diversidad filogen��tica mostraron una variaci��n significativa a lo largo del gradiente ambiental. Un tercer tema fue evaluar si los procesos que organizan la estructura funcional de la comunidad operan a diferentes escalas espaciales. Para ello cartografi�� todos los ��rboles y arbustos de m��s de 5 cm de di��metro en una parcela de 9 Ha de bosque seco y caracteric�� funcionalmente todas las especies. Dicha parcela fue dividida en subparcelas de diferente tama��o, obteni��ndose subparcelas a seis escalas espaciales distintas. Los resultados muestran agregaci��n de estrategias funcionales semejantes a escalas peque��as, lo que sugiere la existencia bien de filtros ambientales actuando a escala fina o bien de procesos competitivos que igualan la estrategia ��ptima a dichas escalas. Finalmente con la misma informaci��n de la parcela permanente de 9 Ha. Nos propusimos evaluar el efecto y comportamiento de las especies respecto a la organizaci��n de la diversidad taxon��mica, funcional y filogen��tica. Para ello utilic�� tres funciones sumario espaciales: ISAR- para el nivel taxon��mico, IFDAR para el nivel funcional y IPSVAR para el nivel filogen��tica y las contrastamos frente a modelos nulos que describen la distribuci��n espacial de las especies individuales. Los resultados mostraron que en todas las escalas espaciales consideradas para ISAR, IFDAR y IPSVAR, la mayor��a de las especies se comportaron como neutras, es decir, que est��n rodeados por la riqueza de diversidad semejante a la esperada. Sin embargo, algunas especies aparecieron como acumuladoras de diversidad funcional y filogen��tica, lo que sugiere su implicaci��n en procesos competitivos de limitaci��n de la semejanza. Una peque��a proporci��n de las especies apareci�� como repelente de la diversidad funcional y filogen��tica, lo que sugiere su implicaci��n en un proceso de filtrado de h��bitat. En este estudio pone de relieve c��mo el an��lisis de las dimensiones alternativas de la biodiversidad, como la diversidad funcional y filogen��tica, puede ayudarnos a entender la co-ocurrencia de especies en diversos ensambles de comunidad. Todos los resultados de este estudio aportan nuevas evidencias de los procesos de ensamblaje de la comunidad de los Bosques Estacionalmente secos y como las variables ambientales y la competencia juegan un papel importante en la estructuraci��n de la comunidad. ABSTRACT The traditional concept of the rules assembly for species communities reflects the idea that species do not co-occur at random but are restricted in their co-occurrence by interspecific competition or an environmental filter. In this thesis, I addressed the importance of the se processes in the assembly of plant communities in the dry forests of southern Ecuador. This study was conducted in the biogeographic region of Tumbesina has the largest concentration of well-conserved tropical dry forests of southern Ecuador, and is recognized as one of the most important areas of endemism in the world. The climate is characterized by a dry season from May to December and a rainy season from January to April. The annual temperature varies between 20 �� C and 26 �� C and an average annual rainfall between 300 and 700 mm. I first assessed whether the distribution of functional traits at the level of the community is compatible with the existence of an environmental filter (imposed by habitat) or the existence of a limitation on functional similarity imposed by interspecific competition. This analysis was conducted for 58 species of woody plants spread over 109 plots of 10 x 50 m. Specifically, I compared the distribution of values of five functional traits (maximum height, wood density, specific leaf area, leaf size and mass of the seed), via selected statistical properties (range, variance, kurtosis and analyzed the standard deviation of the distribution of the closest functional species) distances and compared with a expected distribution under a null model of no competition. The results support that both environmental filtering and a limitation on trait similarity affect the assembly of plant communities in dry forests Tumbesina. My second chapter evaluated whether variation in functional diversity is conditioned by environmental gradients. In particular, I tested whether it decreases in the most stressful environments because of environmental filters, or if, on the contrary, functional diversity is greater in more benign environments where competition becomes more important (notwithstanding possible changes to this general pattern due to facilitation). To address this theme I analyzed changes in both the functional diversity (maximum height, wood density, specific leaf area, leaf size and mass of the seed) and the phylogenetic diversity, along a gradient of climatic stress in Tumbes forests. The observed patterns of variation were contrasted against the diversity expected under a completely random null model of community assembly. Only the diversity of leaf sizes followed the hypothesis decreasing in as trait variation abiotic stress increased, while the other functional traits multivariate functional diversity and phylogenetic diversity no showed significant variation along the environmental gradient. The third theme assess whether the processes that organize the functional structure of the community operate at different spatial scales. To do this I mapped all the trees and shrubs of more than 5 cm in diameter within a plot of 9 hectares of dry forest and functionally classified each species. The plot was divided into subplots of different sizes, obtaining subplots of six different spatial scales. I found aggregation of similar functional strategies at small scales, which may indicate the existence of environmental filters or competitive processes that correspond to the optimal strategy for these fine scales. Finally, with the same information from the permanent plot of 9 ha, I evaluated the effect and behavior of individual species on the organization of the taxonomic, functional and phylogenetic diversity. The analysis comprised three spatial summary functions: ISAR- for taxonomic level analysis, IFDAR for functional level analysis, and IPSVAR for phylogenetic level analysis, in each case the pattern of diversity was contrasted against null models that randomly reallocate describe the spatial distribution of individual species and their traits. For all spatial scales considering ISAR, IFDAR and IPSVAR, most species behaved as neutral, i.e. they are surrounded by the diversity of other traits similar to that expected under a null model. However, some species appeared as accumulator of functional and phylogenetic diversity, suggesting that they may play a role in competitive processes that limiting similarity. A small proportion of the species appeared as repellent of functional and phylogenetic diversity, suggesting their involvement in a process of habitat filtering. These analysis highlights that the analysis of alternative dimensions of biodiversity, such as functional and phylogenetic diversity, can help us understand the co-occurrence of species in the assembly of biotic communities. All results of this study provide further evidence of the processes of assembly of the community of the seasonally dry forests as environmental variables and competition play an important role in structuring the community.

Onom��stica, ecolog��a y territorio. La toponimia de La Rioja como indicador biogeogr��fico y de la din��mica del paisaje forestal

Se presenta un trabajo de investigaci��n topon��mica en La Rioja con enfoque geobot��nico. La premisa de partida es que la toponimia relacionada con especies y agrupaciones vegetales, productos forestales y usos del suelo proporciona informaci��n valiosa sobre la corolog��a y la din��mica de la vegetaci��n al ser clasificada y analizada con criterios biogeogr��ficos y ecol��gicos. Se ha elegido la regi��n riojana como zona piloto, al concurrir distintos tipos fison��micos de vegetaci��n y un conjunto muy diverso de comunidades vegetales representativas del paisaje peninsular. Se a��ade una larga historia de usos agr��colas en la llanura del Ebro que contrasta con la predominante actividad forestal en las zonas monta��osas, en particular la potenciaci��n de los pastos para ganader��a trashumante. La Rioja tiene car��cter de encrucijada no s��lo fitocorol��gica: es tambi��n tierra de fronteras pol��ticas y transiciones ling����sticas. En el l��xico y la toponimia conviven variantes puras del castellano, rasgos del romance navarro-aragon��s, elementos genuinos de una variante medieval riojana, palabras moz��rabes y un numeroso y significativo elenco de top��nimos de origen vasco. El trabajo se inicia con unas consideraciones epistemol��gicas. Se establece un planteamiento de la Toponimia como ciencia interdisciplinar, la etiolog��a de los nombres geogr��ficos, as�� como su valor apelativo descriptor de los atributos del paisaje. Se enumeran los condicionantes metodol��gicos de la investigaci��n topon��mica y se desarrolla una reflexi��n sobre las particularidades de la toponimia geobot��nica. Se dedica un ep��grafe a rese��ar estudios precedentes de toponimia bot��nica y ecol��gica y el estado actual de conocimientos sobre la toponimia de La Rioja. La delimitaci��n superficial de los parajes designados por los nombres geogr��ficos es clave para un an��lisis orientado a detectar la correspondencia entre los elementos aludidos por el top��nimo y las especies y comunidades vegetales. Las ��reas de distribuci��n y presencia, as�� como las transformaciones del paisaje, quedan definidas en superficies acotadas territorialmente. La metodolog��a seguida se basa en la revisi��n exhaustiva de fuentes topon��micas ya existentes; destacadamente, los datos procedentes de la cartograf��a del Castro de R��stica, adscritos a pol��gonos con dimensi��n espacial. Las denominaciones de las parcelas catastrales se han complementado con los nombres geogr��ficos del Diccionario de Toponimia Actual de La Rioja (DTALR) (Gonz��lez Blanco, 1987), el nomencl��tor NomGeo del IGN, y algunas recopilaciones topon��micas municipales. De la base de datos conjunta se han seleccionado los top��nimos con significado geobot��nico. Se propone una taxonom��a de grupos sem��nticos basada en categor��as de estructura (arbolado, matorral, cubiertas herb��ceas y ��reas de vegetaci��n escasa o rala) y en la adscripci��n a tipos de vegetaci��n potencialmente dominantes, ordenados seg��n una escala de higrofilia decreciente). Tambi��n se rese��an top��nimos referentes a usos y aprovechamientos en el medio rural: dehesas, ganader��a, productos forestales y algunos cultivos agr��colas. El trabajo re��ne en un repertorio sistem��tico los datos topon��micos, acopiados por comarcas y t��rminos municipales. Se incluye la relaci��n de nombres geogr��ficos encontrados por campos nocionales y se comentan los nombres vern��culos que les han dado origen y su etimolog��a. Quedan se��alados los top��nimos georreferenciados y asignados a entidades superficiales en la cartograf��a digital catastral, que se ha superpuesto a mapas forestales a escalas 1:200.000 y 1:50.000, en cuya elaboraci��n participamos. El an��lisis ha permitido definir ���top��nimo externo��� como el recinto catastral en que la especie o agrupaci��n aludida no tiene presencia en la vegetaci��n actual, al menos como dominante. Los top��nimos externos m��s significativos de cada grupo han sido analizados describiendo la cubierta vegetal actual correspondiente, lo que permite interpretar, junto con las caracter��sticas fisiogr��ficas del paraje, las causas posibles de ausencia del elemento aludido, teniendo en cuenta criterios generales de mesolog��a, de din��mica de la vegetaci��n y de la historia de la acci��n humana. El trabajo se cierra con un cap��tulo de conclusiones generales, conceptuales y metodol��gicas, as�� como una relaci��n de l��neas de profundizaci��n de la investigaci��n que quedan apuntadas. Se completa con una relaci��n de fuentes y referencias bibliogr��ficas fundamentales. ABSTRACT This paper presents a study of the toponymy of La Rioja with a specific focus on place names reflecting the region���s geobotany. Its underlying premise is that the toponymy associated with plant species and communities, forest products and land uses can provide valuable information about the chorology and vegetation dynamics when classified and analysed using biogeographical and ecological criteria. La Rioja has been chosen for this pilot study because it concentrates vegetation types of distinct physiognomy and a highly diverse set of plant communities that can be considered representative of the vegetation of the peninsula���s landscapes. This combines with a long history of different agricultural uses on the Ebro plain that contrast with the predominance of forestry activity in the more mountainous areas, in particular the promotion of pasture for livestock transhumance. Indeed, La Rioja is not only a crossroads in terms of its phytochorology, but it is also a land of political boundaries and language transitions. Coexisting in its lexicon and toponymy, we find pure Castilian variants, features from the Romance language of Navarro-Aragonese, genuine elements of the medieval variant of the Riojan dialect, words of Mozarabic and a large and significant list of place names of Basque origin. The paper begins by outlining a number of epistemological considerations and establishes an interdisciplinary approach to toponymy, the aetiology of geographical names, and their value in the descriptive naming of the features of a landscape. It continues by enumerating the methodological determinants of toponymic research and reflects on the specific characteristics of geobotanical toponyms. The next section is dedicated to examining previous studies of botanical and ecological place names and providing a state-of-the-art review of the toponymy of La Rioja. Delimiting the sites designated by the geographical names is essential to any analysis designed to detect the correspondence between the elements alluded to by the toponyms and plant species and communities. These areas of distribution and presence, as well as the landscape changes, are defined in terms of spatially delimited surface areas. The methodology adopted involves an exhaustive review of existing toponymic sources; in particular, data obtained from the maps of the Rustic Cadastre, assigned to spatial polygons. The names of these cadastral parcels are complemented by the geographical names taken from the Diccionario de Toponimia Actual de La Rioja (DTALR) (Gonz��lez Blanco, 1987); the gazetteer ��� NomGeo, published by Spain���s Instituto Geogr��fico Nacional; and, various municipal list of toponyms. Place names with a geobotanical meaning were then selected from this joint database. The paper proposes a taxonomy of semantic groups based on structural categories (namely wooded areas, brushland, grassy areas and areas of scanty or sparse vegetation) and assignment to the potentially dominant type of vegetation (ordered on a scale of decreasing hygrophilic trends). Place names referring to land uses and practices in rural areas ��� including, pasture, livestock, forest products and some agricultural crops ��� are also described. The study produces a systematic list of toponyms ordered by counties and municipalities. The geographical names are organised by notional fields and the vernacular names that have given rise to them and their etymology are discussed. The toponyms are georeferenced and assigned to surface elements on the digital cadastral map, superimposed on forest maps at scales of 1:200,000 and 1:50,000, in the production of which the authors participated. The analysis has allowed us to define ���external toponyms��� as those cadastral parcels in which the plant species or group alluded to is no longer present in the vegetation, at least as the dominant type. The most significant external toponyms in each group have been analysed by describing the corresponding, present-day vegetation cover, which allows us to interpret, along with the physiographic features of the site, the possible causes of the absence of the aforementioned element, bearing in mind general criteria of mesology, vegetation dynamics and the history of human action. The paper finishes by offering a number of general conceptual and methodological conclusions, and a list of areas that future research can usefully examine. The study is supplemented with a list of sources and key references.

Regenerative morphological traits in a woody species community in Tumbesian tropical dry forest.

The study of functional morphological traits enables us to know fundamental aspects of the dynamics of plant communities in local and global habitats. Regenerative morphological traits play an important role in defining plant history and ecological behavior. Seed and fruit characteristics determine to a large extent the patterns for dispersal, germination, establishment and seedling recruitment a given species exhibits on its natural habitat. Despite their prominent role, seed and fruit traits have been poorly studied at the community level of woody plant species in neo-tropical dry forests. In the present study we aimed at i) evaluate the functional role of morphological traits of seeds, fruits and embryo in woody plant species; ii) determine which are the morphological patterns present in seeds collected from the community of woody species that occur in neo-tropical dry forests; and iii) compare woody plant species seed mass values comparatively between neo-tropical dry and tropical forests. To do so, mature seeds were collected from 79 plant species that occur in the Tumbesian forest of Southwest Ecuador. The studied species included the 42 and 37 most representative tree and shrubbery species of the Tumbesian forest respectively. A total of 18 morphological traits (seven quantitative and 11 qualitative) were measured and evaluated in the seeds, fruits and embryos of the selected species, and we compared the seeds mass with other forest types. Our results showed a huge heterogeneity among traits values in the studied species. Seed mass, volume and number were the traits that vary the most at the community level, i.e. seed length ranged from 1.3 to 39 mm, and seed width from 0.6 to 25 mm. Only six embryo types were found among the 79 plant species. In 40 % of the cases, fully developed inverted embryos with large and thick cotyledons to store considerable amount of nutrients were recorded. We concluded that highly variable and functionally complementary morphological traits occur among the studied woody plants of the dry Tumbesian forest. The latter favors a plethora of behavioral mechanisms to coexist among woody species of the dry forest in response to the environmental stress that is typical of arid areas.

Predicting temporary wetland plant community responses to changes in the hydroperiod

The expected changes on rainfall in the next decades may cause significant changes of the hydroperiod of temporary wetlands and, consequently, shifts on plant community distributions. Predicting plant community responses to changes in the hydroperiod is a key issue for conservation and management of temporary wetlands. We present a predictive distribution model for Arthrocnemum macrostachyum communities in the Do��ana wetland (Southern Spain). Logistic regression was used to fit the model using the number of days of inundation and the mean water height as predictors. The internal validation of the model yielded good performance measures. The model was applied to a set of expected scenarios of changes in the hydroperiod to anticipate the most likely shifts in the distribution of Arthrocnemum macrostachyum communities.

Comparative study of Fusarium communities from soil and rhizoplane of melon plants from tropical farming soils.

Fifty-nine rhizospheric soil samples from twenty different melon farms of Guatemala and Honduras were analysed to study the Fusarium species present in the soil and those developing on roots surfaces.

Hybrid wind-diesel power plant valuation and optimization using real option theory and dynamic programming

El sistema de energ��a e��lica-diesel h��brido tiene un gran potencial en la prestaci��n de suministro de energ��a a comunidades remotas. En comparaci��n con los sistemas tradicionales de diesel, las plantas de energ��a h��bridas ofrecen grandes ventajas tales como el suministro de capacidad de energ��a extra para "microgrids", reducci��n de los contaminantes y emisiones de gases de efecto invernadero, y la cobertura del riesgo de aumento inesperado del precio del combustible. El principal objetivo de la presente tesis es proporcionar nuevos conocimientos para la evaluaci��n y optimizaci��n de los sistemas de energ��a h��brido e��lico-diesel considerando las incertidumbres. Dado que la energ��a e��lica es una variable estoc��stica, ��sta no puede ser controlada ni predecirse con exactitud. La naturaleza incierta del viento como fuente de energ��a produce serios problemas tanto para la operaci��n como para la evaluaci��n del valor del sistema de energ��a e��lica-diesel h��brido. Por un lado, la regulaci��n de la potencia inyectada desde las turbinas de viento es una dif��cil tarea cuando opera el sistema h��brido. Por otro lado, el bene.cio econ��mico de un sistema e��lico-diesel h��brido se logra directamente a trav��s de la energ��a entregada a la red de alimentaci��n de la energ��a e��lica. Consecuentemente, la incertidumbre de los recursos e��licos incrementa la dificultad de estimar los beneficios globales en la etapa de planificaci��n. La principal preocupaci��n del modelo tradicional determinista es no tener en cuenta la incertidumbre futura a la hora de tomar la decisi��n de operaci��n. Con lo cual, no se prev�� las acciones operativas flexibles en respuesta a los escenarios futuros. El an��lisis del rendimiento y simulaci��n por ordenador en el Proyecto E��lico San Crist��bal demuestra que la incertidumbre sobre la energ��a e��lica, las estrategias de control, almacenamiento de energ��a, y la curva de potencia de aerogeneradores tienen un impacto significativo sobre el rendimiento del sistema. En la presente tesis, se analiza la relaci��n entre la teor��a de valoraci��n de opciones y el proceso de toma de decisiones. La opci��n real se desarrolla con un modelo y se presenta a trav��s de ejemplos pr��cticos para evaluar el valor de los sistemas de energ��a e��lica-diesel h��bridos. Los resultados muestran que las opciones operacionales pueden aportar un valor adicional para el sistema de energ��a h��brida, cuando esta flexibilidad operativa se utiliza correctamente. Este marco se puede aplicar en la optimizaci��n de la operaci��n a corto plazo teniendo en cuenta la naturaleza dependiente de la trayectoria de la pol��tica ��ptima de despacho, dadas las plausibles futuras realizaciones de la producci��n de energ��a e��lica. En comparaci��n con los m��todos de valoraci��n y optimizaci��n existentes, el resultado del caso de estudio num��rico muestra que la pol��tica de operaci��n resultante del modelo de optimizaci��n propuesto presenta una notable actuaci��n en la reducci��n del con- sumo total de combustible del sistema e��lico-diesel. Con el .n de tomar decisiones ��ptimas, los operadores de plantas de energ��a y los gestores de ��stas no deben centrarse s��lo en el resultado directo de cada acci��n operativa, tampoco deber��an tomar decisiones deterministas. La forma correcta es gestionar din��micamente el sistema de energ��a teniendo en cuenta el valor futuro condicionado en cada opci��n frente a la incertidumbre. ABSTRACT Hybrid wind-diesel power systems have a great potential in providing energy supply to remote communities. Compared with the traditional diesel systems, hybrid power plants are providing many advantages such as providing extra energy capacity to the micro-grid, reducing pollution and greenhouse-gas emissions, and hedging the risk of unexpected fuel price increases. This dissertation aims at providing novel insights for assessing and optimizing hybrid wind-diesel power systems considering the related uncertainties. Since wind power can neither be controlled nor accurately predicted, the energy harvested from a wind turbine may be considered a stochastic variable. This uncertain nature of wind energy source results in serious problems for both the operation and value assessment of the hybrid wind-diesel power system. On the one hand, regulating the uncertain power injected from wind turbines is a difficult task when operating the hybrid system. On the other hand, the economic profit of a hybrid wind-diesel system is achieved directly through the energy delivered to the power grid from the wind energy. Therefore, the uncertainty of wind resources has increased the difficulty in estimating the total benefits in the planning stage. The main concern of the traditional deterministic model is that it does not consider the future uncertainty when making the dispatch decision. Thus, it does not provide flexible operational actions in response to the uncertain future scenarios. Performance analysis and computer simulation on the San Cristobal Wind Project demonstrate that the wind power uncertainty, control strategies, energy storage, and the wind turbine power curve have a significant impact on the performance of the system. In this dissertation, the relationship between option pricing theory and decision making process is discussed. A real option model is developed and presented through practical examples for assessing the value of hybrid wind-diesel power systems. Results show that operational options can provide additional value to the hybrid power system when this operational flexibility is correctly utilized. This framework can be applied in optimizing short term dispatch decisions considering the path-dependent nature of the optimal dispatch policy, given the plausible future realizations of the wind power production. Comparing with the existing valuation and optimization methods, result from numerical example shows that the dispatch policy resulting from the proposed optimization model exhibits a remarkable performance in minimizing the total fuel consumption of the wind-diesel system. In order to make optimal decisions, power plant operators and managers should not just focus on the direct outcome of each operational action; neither should they make deterministic decisions. The correct way is to dynamically manage the power system by taking into consideration the conditional future value in each option in response to the uncertainty.