Evapotranspiration dominates the water budget in drylands, exerting important controls not only on the dynamics of water, but also on the amount and distribution of vegetation on a landscape. The spatial and temporal variability of vegetation cover imposes constraints on key ecohydrological processes that feedback to the dynamics of evapotranspiration and, most importantly, its partitioning between direct evaporation and transpiration from plants, one of the most significant ecohydrological challenges. Yet, lacking are systematic evaluations of how variations in woody plant cover--a fundamental vegetation attribute of landscapes that can vary spatially with amount of cover and temporally with leaf phenology-- influence the dynamics of soil microclimate and ultimately the partitioning of evapotranspiration into its components. This study presents the results of field experiments that systematically evaluated the effects of amount of canopy cover and its seasonality in both surface microclimate and soil evaporation. These field observations are complemented by controlled experiments that directly evaluate the relationship between amount of canopy cover and the partitioning of evapotranspiration, with an assessment of its larger-scale implications using a regional land surface-atmosphere model. Finally, this study presents a classroom-adaptation of the evapotranspiration partitioning experiment that was used to effectively translate new scientific concepts and information into k-12 classrooms. Overall, the results from this study provide a comprehensive understanding about the interactive ways in which canopy cover, canopy structure attributes and plant phenology influence soil surface microclimate--characterized by near-ground solar radiation and soil temperature--and soil evaporation. More specifically, the results illustrate how the main control of deciduous-woody vegetation on soil evaporation is the addition of litter to the surface. However, in absence of litter, attributes of woody cover influence soil evaporation variably with season and phenology. Further, The results from this study illustrate how the partitioning of evapotranspiration exhibits a non-linear response to amount of woody canopy cover. Notably, when incorporated into a regional surface-atmosphere model, this non-linearity strongly affects water fluxes, highlighting the potential implications for ecological, hydrological, and atmospheric processes associated with the partitioning of evapotranspiration, providing important insights for natural resource management.

In recent years, green roofs have become an accepted solution in ecological urban design to mitigate the impacts of impervious surfaces (Berghage, Beattie, Jarrett, Thuring, & Razaei, 2009). An experimental research project was conducted at the Mississippi Agriculture and Forestry Experiment Station (MAFES) Green Infrastructure Research Area at South Farm of Mississippi State University to determine how medium depth and slope gradient on rooftops affect plant cover and survival. Plant cover was monitored monthly by photographing the experimental green roof platforms. Photoshop and AutoCAD software programs were employed to digitize and to calculate plant cover from the images. All recorded data was analyzed with Analysis of Variance (ANOVA) tests. It was determined that the effects of medium depth and slope are statistically significant on plant cover and survival.

The aim of proposed thesis is identification and assessment of the impact of various types of vegetation cover on microclimate and local climate. The thesis study an issue of vegetation cover impact on the solar energy transformation, energy fluxes and an impact of vegetation cover on water cycle, mostly at the landscape level. Temperature-humidity characteristics and energy fluxes and their indicators (Bowen ratio, evaporative fraction) were monitored during the growing season in common types of vegetation cover occurring in agricultural landscapes (red clover - Trifolium pratense L., common wheat - Triticum aestivum L., potatoes - Solanum tuberosum L. and permanent grassland (TTP)) and wetland with predominantly tall sedge vegetation (e.g. Carex acuta L., Glyceria maxima (Hartman). Holmberg.). Results show a direct correlation between solar radiation and the amount of energy converted into latent heat of evaporation or sensible heat flux expressed through evapotranspiration. The results of analyses confirmed the theoretical assumption that the vegetation cover significantly influences microclimate, e.i. air temperature and humidity both of itself and surrounding area. The temperature-humidity characteristics were significantly different in the monitored stands. From this findings is obvious that the different types of vegetation can affect local microclimate differently. Moreover, the results showed that the vegetation well stocked with water probably significantly affects the water cycle in the landscape.

Made available in DSpace on 2017-07-10T17:37:33Z (GMT). No. of bitstreams: 1 Roberto_Siqueira_Filho.pdf: 599786 bytes, checksum: 20c51a992fef457567584c4778cba829 (MD5) Previous issue date: 2005-06-14 / The present work had for objective to evaluate the effect of different covering crops and the surface liming in no-tillage system, determining the content of dry biomass produced by each one of these species and the effect of the liming on the chemical properties of the soil and its consequent effect in the yield components and the productivity of the winter maize crop. The experiment was lead in period 2003/2004, in the experimental farm of the IAPAR (Paraná State Agronomic Institute), in one soil classified as Eutroferric Red Latosol, in the city of Palotina - PR. The treatments had been constituted of five vegetal covering species (millet, guandu, foxtail millet, association of guandu with millet and pousio), in combinations with and without surface liming. 3,2 t ha-1 of dolomitic limestone had been applied in surface in certain plots, without incorporation. It was determined that the desiccation of green fertilizers would be carried through when the species emitted string beans or panicle. At the moment of the desiccation of the plots the collections of biomass for determination of the production and the speed of decomposition of each one of the species had been initiated, happening again themselves this sampling 15, 30 and 45 days after. Also stratified soil samples had been collected (0 0,10 and 0,10 0,20 m) in each plot, in the line of sowing of the species, for determination of pH, levels of P, M.O., H + Al, K, Ca and Mg and values of SB, CTC, V% and m%. The sowed maize were the simple modified hybrid AG-9010. The experiment in the field was conducted until being carried through the harvest of the plots and determined the productivity. Also the determination of the components of the production (number of grains for spike, mass of the grains for spike and mass of 100 grains) in function of the vegetal species and application or not of limestone in each plot was carried through. One concluded that, independently of the species of covering, the surface liming is efficient in the correction of the acidity of the soil and increase of pH and levels of calcium and magnesium in the 0 0,10 m layer. At guandu plots occurred increase of the level of phosphorus of the soil in the depth of 0,10 0,20 m, however this fact must be associated to the liming, a time that this species presents great capacity to acidify of the soil. The Millet presented greater production of dry matter and bigger tax of decomposition, followed for the association of millet with guandu and guandu. Grass mills also presented minor residue production and lesser tax of decomposition during the period of 45 days. The combination of liming more guandu as species of soil covering before the winter maize crop, results in profits in the mass of the spike and mass of 100 grains, with positive consequences in the productivity / O presente trabalho teve por objetivo avaliar o efeito de diferentes espécies de cobertura vegetal e da aplicação superficial de calcário em sistema plantio direto, determinando o teor de biomassa seca que cada uma das espécies produziu e o efeito da calagem sobre as propriedades químicas do solo e seu conseqüente efeito nos componentes da produção e na produtividade do milho safrinha . O experimento foi conduzido no período 2003/2004, na fazenda experimental do IAPAR (Instituto Agronômico do Paraná), em um solo classificado como Latossolo Vermelho Eutroférrico, no município de Palotina - PR. Os tratamentos foram constituídos de cinco espécies de cobertura vegetal (milheto, guandú, capim moha, associação de guandú com milheto e pousio) em combinações com e sem calagem em superfície. Foram aplicadas 3,2 t ha-1 de calcário dolomítico em superfície nas parcelas pré-determinadas, sem incorporação. A dessecação dos adubos verdes foi realizada quando as espécies estavam no estádio de emissão de vagens e de panículas. No momento da dessecação das parcelas iniciaram-se as coletas de biomassa para determinação da produção e da velocidade de decomposição de cada uma das espécies, repetindo-se essa amostragem 15, 30 e 45 dias após à primeira. Também foram coletadas amostras estratificadas de solo (0-10 e 0,10 0,20 m) em cada parcela, na linha de semeadura da espécie, para determinação de pH, teores de P, M.O., H + Al, K, Ca e Mg e valores de SB, CTC, V% e m%. A cultivar de milho utilizada foi o híbrido simples modificado AG-9010. Conduziu-se o experimento no campo até ser realizada a colheita das parcelas e determinada a produtividade. Também foi realizada a determinação dos componentes da produção (número de grãos por espiga, massa dos grãos por espiga e massa de 100 grãos) em função das espécies vegetais e aplicação ou não de calcário em cada parcela. Concluiu-se que a calagem em superfície, independentemente da espécie de cobertura, foi eficaz na correção da acidez do solo, proporcionando o aumento de pH e dos teores de cálcio e magnésio na camada de 0 0,10 m. Na presença de guandú ocorreu aumento do teor de fósforo do solo na profundidade de 0,10 0,20 m, entretanto, esse fato deve estar associado à calagem, uma vez que esta espécie apresenta grande capacidade de acidificar o solo. O milheto apresentou maior produção de biomassa seca e também maior taxa de decomposição, seguida pela associação de milheto e guandú e apenas guandú. O capim moha apresentou menor produção de resíduo e também menor taxa de decomposição durante o período de 45 dias. A combinação de calagem mais cultivo de guandú como espécie de cobertura de solo antes do milho safrinha resultou em ganhos na massa da espiga e massa de 100 grãos, com reflexos positivos na produtividade

Woody plant encroachment, that is, a substantial increase in the abundance of woody plants in a grassland or savanna, occurs in many parts of the world. It often has large effects on plant and animal populations and communities and on ecosystem properties and processes. However, little is known about the dynamics of woody plant encroachment and how these are affected by soils, by topography, and by the spatial pattern of the vegetation. Encroachment in turn can affect the spatial pattern of the vegetation. Using data from historical aerial photographs, I measured changes in woody plant cover and constructed, parameterized and compared a set of dynamic models of woody plant encroachment in central Texas savannas. These models predicted final woody cover from initial woody cover and the initial spatial configuration of woody plants. Then I incorporated soil and topography into these models to determine their effects. Finally, I examined the effects of encroachment on the spatial pattern of the vegetation. Incorporating negative density dependence in our models improved their fit, demonstrating that encroachment is density-dependent. A function that predicted the formation of new woody patches from a density-independent seed supply also improved the models' performance. The improvement in the models that resulted from incorporating the total length of woody-herbaceous edges confirmed that encroachment in this system occurs in part by the outward expansion of woody patches. The spatial pattern of the vegetation changed during woody plant encroachment. Spatial pattern (measured as degree of fragmentation) often had a non-linear relationship with cover. Furthermore, the spatial heterogeneity in fragmentation, that is, plot-to-plot variation in the degree of fragmentation, also changed during encroachment. Topography and soil type had, in general, little effect the dynamics of woody plant encroachment. Therefore, a relatively simple model of woody plant encroachment provided good predictions of woody cover at the end of the time periods. Other systems experiencing woody plant encroachment, forest succession, or invasion by non-native plants could be modeled using the same approach. / text

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2006. / Härtill 4 uppsatser.

Made available in DSpace on 2016-04-28T14:59:42Z (GMT). No. of bitstreams: 1 2006-Roberta Cristiane Ribeiro.pdf: 1282161 bytes, checksum: 5e7174cb11915976886dd9494c3fb2d5 (MD5) Previous issue date: 2006-09-12 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In the way to improve the agronomic indexes and animal science of acting in the pastures cultivated on State of Rio de Janeiro soils, it`s needing a deeper studies to evaluate the impact of forage legumes in those ecosystems introduction. Seeking to contribute in that direction, an experiment was installed aiming at research the effects with different introduction methods of forage legumes in a pasture forage grass in monoculture. The work hypothesis was the treatments of nature chemical or mechanical that reduces the growth in the established grass, will have favorable effects on the establishment and persistence forage legume. The work was accomplished in the experimental field of Forage study, in the Institute animal science, the Universidade Federal Rural of Rio de Janeiro, from November/2003 to Abril/2005. The studied forage legumes were estilosantes cv. Campo Grande and desm?dio (Desmodium ovalifolium Wall cv. Itabela), installed into grass pasture of Brachiaria humidicola (Rendle) Schweickt. The introduction methods compared were: i) herbicide (Glyphosate, 0,75%, V/L), one day before the planting; ii) with grass mechanical cut; iii) planting in furrows and; iv) prepare soil with use of harrowing, being used a design was a randomized block, with four repetitions. The growth of the forage legumes in the several swards formed after the installation of the treatments, it was accompanied through count of the plants number and plants height, frequency estimates, absolute and relative, of grass and legume in the sward, and the Index of Leaf Area. Together, they were made evaluations of interception photosynthetically active radiation and degree of covering of the sward mixed pasture. The contribution forage legume to the production forage mass, green and dry, was done through cuts, to the 157 and 430 days after seeding. The mixed with estilosantes cv. Campo Grande didn't prosper, due the failure in the germination and or plants emergency of the forage legume. In contrast, in the mixed case between the braqui?ria and the desm?dio specie, the initial hypothesis was confirmed fully, once all the introduction methods allowed the establishment and permanence forage legume in the grass pasture. Specifically, for this associate, it was ended that to foment a fast covering of the soil, the most suitable treatments are the harrowing and weeds (mechanical cut), while to harmonize his associate, protecting the persistence of both components, the plantings in furrow and herbicide use was the most interesting alternatives. / Como forma de melhorar os ?ndices agron?micos e zoot?cnicos de desempenho das pastagens cultivadas sobre solos do Estado do Rio de Janeiro, existe a necessidade de maiores estudos para avaliar o impacto da introdu??o de leguminosas forrageiras nesses ecossistemas. Visando contribuir nessa dire??o, foi instalado um experimento objetivando pesquisar os efeitos de diferentes m?todos de introdu??o de leguminosas forrageiras numa pastagem de gram?nea forrageira em monocultura. A hip?tese de trabalho foi a de que tratamentos de natureza qu?mica ou mec?nica que reduzam o crescimento da gram?nea estabelecida, ter?o efeitos favor?veis sobre o estabelecimento e persist?ncia da leguminosa. O trabalho foi realizado na ?rea experimental de Forragicultura, no Instituto de Zootecnia da Universidade Federal Rural do Rio de Janeiro, durante o per?odo de novembro de 2003 a abril de 2005. As leguminosas estudadas foram estilosantes cv. Campo Grande e desm?dio (Desmodium ovalifolium Wall cv. Itabela), instaladas sobre pastagem de Brachiaria humidicola (Rendle) Schweickt. Os m?todos de introdu??o comparados foram: i) herbicida dessecante (Glyphosate, 0,75%, V/L), um dia antes do plantio; ii) ro?ada: rebaixamento da gram?nea, com corte mec?nico iii) plantio em sulcos e; iv) preparo do solo com uso de enxada rotativa, empregando-se um desenho de blocos inteiramente casualizados, com quatro repeti??es. O crescimento das leguminosas nos diversos doss?is formados ap?s a instala??o dos tratamentos, foi acompanhado atrav?s de contagem do n?mero de plantas e da altura das plantas, estimativas de freq??ncia, absoluta e relativa, de gram?nea e leguminosa no relvado, e o ?ndice de ?rea Foliar. Em conjunto, foram feitas avalia??es de intercepta??o de radia??o fotossinteticamente ativa e grau de cobertura dos doss?is do cons?rcio. A contribui??o da leguminosa ? produ??o da massa de forragem, verde e seca, foi feita atrav?s de cortes, aos 157 e 430 dias ap?s a semeadura. O cons?rcio com estilosantes cv. Campo Grande n?o prosperou, devido ao fracasso na germina??o e ou emerg?ncia das pl?ntulas da leguminosa. Em contraste, no caso do cons?rcio entre a braqui?ria e o desm?dio, a hip?tese inicial foi plenamente confirmada, uma vez que todos os m?todos de introdu??o permitiram o estabelecimento e perman?ncia da leguminosa na pastagem. Especificamente, para este cons?rcio, foi conclu?do que para fomentar uma r?pida cobertura do solo, os tratamentos mais indicados s?o a enxada rotativa e a ro?ada, enquanto que para harmonizar o cons?rcio, resguardando a persist?ncia de ambos componentes, os plantios em sulco e uso de herbicida foram ?s alternativas mais interessantes.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 3 uppsatser.

La berce du Caucase (Heracleum mantegazzianum) est une espèce envahissante provoquant des photodermatites lors d’un contact avec la sève. Son éradication laisse le sol à nu, facilitant ainsi sa réinfestation. L’objectif de mon projet est d’évaluer l’effet de l’ensemencement d’un couvert végétal pour empêcher l’établissement de la berce par phénomène de compétition. J’ai d’abord effectué une expérience en mésocosme utilisant cinq mélanges d’espèces herbacées afin de tester l’effet de la composition sur la germination, la croissance et la survie de la berce du Caucase. Trois mélanges, incluant ceux contenant Solidago canadensis, ont réduit le nombre de semences ayant germé. Tous les mélanges ont réduit la croissance et la survie des semis. Afin de déterminer si l’allélopathie pouvait être le mécanisme responsable de ce phénomène, j’ai testé l’effet de substances allélopathiques, extraites des feuilles et des racines du S. canadensis, sur la germination des semences de la berce. Bien qu’elle montre un effet allélopathique sur une espèce modèle (le radis), mon expérience n’a pas permis de détecter d’effet négatif sur la germination de la berce. Étant donné que celle-ci peut se faire dans l’obscurité, un mécanisme autre que la lumière ou l’allélopathie serait la cause de la réduction du taux de germination chez certains mélanges. Par contre, la réduction de la lumière par le couvert végétal serait la cause probable de la diminution de croissance et de la survie des semis. En définitive, un mélange composé majoritairement de graminées et produisant rapidement un couvert végétal dense aurait un meilleur potentiel pour la restauration suite à des travaux de lutte. / Giant Hogweed (Heracleum mantegazzianum) is an invasive species that causes human skin photodermatitis after contact with the sap. Control techniques of the plant often produced a soil devoid of vegetation cover, which facilitates reinvasion. The objective of my project was to evaluate the effect (competition) of plant seeding on the establishment of Giant Hogweed. First, I conducted a mesocosm experiment using five herbaceous plant mixtures in order to test the effect of composition and associated cover on germination, growth and survival of Giant Hogweed. Three mixtures, especially those with Solidago canadensis, reduced germination rate. Every mixture reduced growth and survival of Giant Hogweed seedlings. In order to identify the mechanism responsible for this phenomenon, I tested the effect of allelopathic substances, extracted from leaves and roots of S. canadensis, on germination of Giant Hogweed seeds. Although an allelopathic effect on a model species (radish) was detected, the substances did not impede Giant Hogweed germination. Considering germination occurs in darkness, a mechanism other than light or allelopathy would be responsible for the reduction of germination rate in certain plant mixtures. However, the reduction of light through plant cover would likely be the cause for the decrease of growth and survival of Giant Hogweed seedlings. A seed mixture mostly composed of grasses and rapidly producing a dense plant cover has a good potential for restoration following weeding.

The work presented in this Doctoral Thesis has studied the temporal and spatial patterns of the most relevant soil parameters with special attention posed to soil biological and biochemical dynamics occurring at the studied soils in a very fragile area at Cap de Creus Peninsula, NE Spain. The main objective was to establish evidence of soil quality through the study of soil carbon dynamics (loss and storage) and their interactions with soil ecosystems. Soil environments were classified in terms of degree of soil quality, relating soil properties with plant cover species, especially along a sequence of agricultural abandonment where perturbations like wildfire and strong downpours often cause regressive dynamics in the natural succession of spontaneous vegetation and start erosion and degradation processes. At this regard, when fire occurrence is frequent, a quick drop down of all soil attributes was recorded leading to loss of biodiversity and, ultimately, desertification. / El treball de tesi doctoral ha estudiat els trets espacials i temporals de paràmetres mes rellevants del sòl, amb especial atenció en la dinàmica biològica i bioquímica que es dona en un àrea molt fràgil situada en la Península del Cap de Creus, NE Espanya. L’objectiu principal ha estat establir la qualitat dels sòls mitjançant l’estudi de la dinàmica del carboni (pèrdues i embornals) i la interacció amb l’ecosistema sòl. Els ambients estudiats s’han classificats en termes de qualitat del sòl, relacionant les seves propietats amb la coberta vegetal, especialment al llarg d’una seqüència d’abandonament agrícola on la presencia de pertorbacions com incendis o pluges causen sovint una dinàmica regressiva en la successió natural de la vegetació espontània i activen processos d’erosió i degradació. Tanmateix, en cas d’incendis freqüents, es registra un ràpid deteriorament de les propietats del sòl que provoca una pèrdua de biodiversitat i, mes tard, una desertificació.