Citrus is grown in almost all countries with a sub-tropical or tropical climate. Africa produces about 7% of global citrus production representing 67 362 564 tonnes in the 2003-04 season. Of these countries, South Africa is the most important citrus producer with the bulk of its fruit being exported to mainly European countries. Although South Africa is the world’s fourteenth biggest producer, it is currently ranked third in terms of global export volumes. An increase in the number of foodborne disease outbreaks over the past few decades has been related to the shift towards consumption of fresh produce and growing world trade. Other factors include changing demographic profiles, changing farm practises, extensive distribution and handling networks, increased consumption of unprocessed products, emergence of new pathogens and more effective detection methods. Shigella spp., Listeria monocytogenes, Hepatitis virus, Caliciviridae virus, Salmonella spp., Escherichia coli and Vibrio cholera are some of the microorganisms implicated in disease outbreaks caused by the consumption of fresh produce. This dissertation focuses on citrus fruit safety and a selected foodborne pathogen, Salmonella enterica serovar Typhimurium. Salmonella has been implicated in several outbreaks associated with the consumption of unpasteurized orange juice, mangoes, cantaloupes, sprouts and tomatoes. S. enterica sv. Typhimurium is also a water-borne pathogen, and its importance in agricultural irrigation and packhouse wash water was also studied. The presence of S. enterica sv. Typhimurium in biofilms in packhouse water and on fruit was finally investigated since biofilms are known to harbour a number of these pathogens. Biofilm formation was monitored in the warm water dip tank using a photo acoustic monitoring device and confirmed by scanning electron microscopy and enumeration. Water sources, i.e. bathroom, handwash stations, irrigation water and warm water baths had high total viable bacterial counts and faecalassociated contamination. Biofilms also formed within the packhouse dip tank at an increased rate. The Polymerase Chain Reaction (PCR) was used to investigate the presence of Salmonella in the citrus export chain. No Salmonella spp. could be detected. S. enterica sv. Typhimurium survived for up to four weeks on the surface of citrus fruit under simulated export conditions. However, Salmonella is not able to survive uninterrupted cold storage conditions for a period longer than two or three weeks. Scanning Electron Micrographs showed that Salmonella is capable of attaching to and colonizing the citrus fruit surface and is able to be incorporated into existing biofilms in warm water tanks of packhouses. This study showed that Salmonella can thrive in packhouse water and potentially be a continuous source of contamination for fruit moving through the infected warm water dip tank. Everyone participating in fruit production, storage and post-harvest handling of fresh fruit should be involved in ensuring quality and safety, since events in the orchard can affect storage life, and incorrect handling during marketing may nullify all previous efforts of quality maintenance. To minimize the occurrence of these pathogens in the fruit chain from production to consumption, several basic good agricultural practices and food safety systems needs to be incorporated and managed correctly. / Dissertation (MSc)--University of Pretoria, 2009. / Microbiology and Plant Pathology / unrestricted

A década de 90 foi caracterizada por uma grande expansão no mercado Brasileiro e mundial de frutas, em especial nas frutas de outono, como o caqui Diospyros kaki L.). Embora a quase totalidade da produção nacional de caqui seja destinada ao mercado interno, o Brasil vem se consolidando nos últimos anos como país exportador dessa fruta para países do continente americano e europeu. Por essa razão, o cultivo dessa fruteira vem se constituindo numa importante atividade agrícola para pequenos produtores no Brasil. O conhecimento da fenologia e de como varia o conteúdo em carboidratos de reserva do caquizeiro em clima tropical é de grande importância para o estudo do desenvolvimento dessa espécie nessas condições. A falta informações dessa natureza para o caquizeiro cultivado no Brasil motivou o presente estudo com a variedade Rama Forte, a mais cultivada e consumida no país. O trabalho conduzido em um pomar localizado na área experimental, setor de horticultura, da escola Superior de Agricultura "Luiz de Queiroz" (ESALQ) em Piracicaba - SP, no período 2002/2003. A fenologia foi caracterizada desde a brotação das gemas até a abscisão foliar. A variação dos teores de carboidratos de reserva em ramos e em raízes é descrita tendo por base os diferentes períodos de coleta de material no campo, e discutidos em função dos estádios fenológicos da planta e das estações do ano. As plantas estudadas passaram pelos estádios de dormência, brotação, elongação, florescimento, frutificação, senescência e abscisão foliar. As curvas de crescimento do fruto exibiram o padrão sigmoidal duplo, sendo que o crescimento em diâmetro se antecipou em relação ao acúmulo de massa. O crescimento do cálice se estabilizou ao final do último estágio de desenvolvimento dos frutos. Da brotação das gemas no final do inverno até a maturação dos frutos no início do outono passaram-se 199 dias. Após o florescimento foram produzidos apenas frutos sem sementes, com duração de 161 dias até a sua maturação. Ocorreram dois picos no abortamento de frutos. Os primeiros sintomas de senescência das folhas foram registrados a partir do último estágio de desenvolvimento dos frutos, dois meses e meio após a formação da copa ter sido concluída. Da brotação das gemas até o completo desfolhamento somaram-se 287 dias no decorrer de toda a primavera, verão e outono. A análise dos teores dos carboidratos de reserva mostrou que ocorreram variações significativas (P ≤0,05) no teor de amido e de açúcares solúveis totais nos órgãos amostrados. O amido se constitui numa importante fonte de material de reserva a ser mobilizada durante o ciclo do caquizeiro. Em relação aos açúcares solúveis totais, o amido mostrou maiores variações significativas, tanto no ramo como na raiz ao longo do período estudado. A recomposição no estoque de carboidratos de reserva nos ramos e nas raízes ocorreu durante o período de atividade fotossintética. / The decade of 90 was characterized by a great expansion in the Brazilian and world-wide market of fruits, in special in the autumn fruits, as persimmon (Diospyros kaki L.). Although almost the totality of the national production of persimmon either destined to the domestic market, Brazil comes if consolidating in the last years as exporting country of this fruit for countries of the American and European continent. Therefore, persimmon crop comes if constituting in an important agricultural activity for small growers in Brazil. The knowledge of the phenology of persimmon tree and how their reserve in carbohydrate content varies in tropical climate is of great importance for the study of persimmon´s tree in these conditions. The lack of information of this nature for the persimmon cultivated in Brazil motivated the present study with the ‘ Rama Forte’ variety, the most cultivated and consumed in the country. The work was lead in an orchard located in the sector of horticulture, in the Escola Superior de Agricultura "Luiz de Queiroz" (ESALQ), in Piracicaba, SP, during 2002/2003 growing cicle. The phenology of tree was characterized from budbreak to leaf fall, and carboydrate reserves in stems and roots was described for different times of plant material collected in the field, and argued based on phenological stages. The mixed buds had passed the stages of dormancy, budbreak, shoot elongation, bloom, fruition, leaf senescence and leaf fall successively. The curves of growth of the fruit had shown the double sigmoidal standard and growth of fruit diameter preceded that of fresh and dry weight. Calyx growth stabilized in the end of the last stage of fruit development. From budbreak, in the end of winter to the maturation of fruits, in the beginning of autumn was recorded 199 days. Only seedless fruits were produced. From flowering to fruit maturity 161 days was registered. Two peaks in the abortion of fruits had occurred. The first symptoms of leaf senescence had been registered from the last stage of fruit development, two months after the canopy have been concluded. From budbreak to the complete leaf fall 287 days was recorded during all the spring, summer and autumn growing seasons. Starch and total soluble sugars content fluctuated in roots and stems throughout (P≤0,05) phenologycal stages of persimmons tree. Starch fluctuations showed to be more prone to significant variations in relation to the total soluble sugars in the stems as in the root. Two peaks of starch depletion was registered. The stem and root tissue started to accumulate starch during the net exporting photoassimilates by leaf photosynthesis. These results indicate that root and stem tissues play a role as a carbohydrate reserve pools to be mobilized for shoot elongation, flowering and for the maintenance of the tree during the lack of photosynthesis activity of persimmon tree.

A década de 90 foi caracterizada por uma grande expansão no mercado Brasileiro e mundial de frutas, em especial nas frutas de outono, como o caqui Diospyros kaki L.). Embora a quase totalidade da produção nacional de caqui seja destinada ao mercado interno, o Brasil vem se consolidando nos últimos anos como país exportador dessa fruta para países do continente americano e europeu. Por essa razão, o cultivo dessa fruteira vem se constituindo numa importante atividade agrícola para pequenos produtores no Brasil. O conhecimento da fenologia e de como varia o conteúdo em carboidratos de reserva do caquizeiro em clima tropical é de grande importância para o estudo do desenvolvimento dessa espécie nessas condições. A falta informações dessa natureza para o caquizeiro cultivado no Brasil motivou o presente estudo com a variedade Rama Forte, a mais cultivada e consumida no país. O trabalho conduzido em um pomar localizado na área experimental, setor de horticultura, da escola Superior de Agricultura “Luiz de Queiroz” (ESALQ) em Piracicaba – SP, no período 2002/2003. A fenologia foi caracterizada desde a brotação das gemas até a abscisão foliar. A variação dos teores de carboidratos de reserva em ramos e em raízes é descrita tendo por base os diferentes períodos de coleta de material no campo, e discutidos em função dos estádios fenológicos da planta e das estações do ano. As plantas estudadas passaram pelos estádios de dormência, brotação, elongação, florescimento, frutificação, senescência e abscisão foliar. As curvas de crescimento do fruto exibiram o padrão sigmoidal duplo, sendo que o crescimento em diâmetro se antecipou em relação ao acúmulo de massa. O crescimento do cálice se estabilizou ao final do último estágio de desenvolvimento dos frutos. Da brotação das gemas no final do inverno até a maturação dos frutos no início do outono passaram-se 199 dias. Após o florescimento foram produzidos apenas frutos sem sementes, com duração de 161 dias até a sua maturação. Ocorreram dois picos no abortamento de frutos. Os primeiros sintomas de senescência das folhas foram registrados a partir do último estágio de desenvolvimento dos frutos, dois meses e meio após a formação da copa ter sido concluída. Da brotação das gemas até o completo desfolhamento somaram-se 287 dias no decorrer de toda a primavera, verão e outono. A análise dos teores dos carboidratos de reserva mostrou que ocorreram variações significativas (P ≤0,05) no teor de amido e de açúcares solúveis totais nos órgãos amostrados. O amido se constitui numa importante fonte de material de reserva a ser mobilizada durante o ciclo do caquizeiro. Em relação aos açúcares solúveis totais, o amido mostrou maiores variações significativas, tanto no ramo como na raiz ao longo do período estudado. A recomposição no estoque de carboidratos de reserva nos ramos e nas raízes ocorreu durante o período de atividade fotossintética. / The decade of 90 was characterized by a great expansion in the Brazilian and world-wide market of fruits, in special in the autumn fruits, as persimmon (Diospyros kaki L.). Although almost the totality of the national production of persimmon either destined to the domestic market, Brazil comes if consolidating in the last years as exporting country of this fruit for countries of the American and European continent. Therefore, persimmon crop comes if constituting in an important agricultural activity for small growers in Brazil. The knowledge of the phenology of persimmon tree and how their reserve in carbohydrate content varies in tropical climate is of great importance for the study of persimmon´s tree in these conditions. The lack of information of this nature for the persimmon cultivated in Brazil motivated the present study with the ‘ Rama Forte’ variety, the most cultivated and consumed in the country. The work was lead in an orchard located in the sector of horticulture, in the Escola Superior de Agricultura “Luiz de Queiroz” (ESALQ), in Piracicaba, SP, during 2002/2003 growing cicle. The phenology of tree was characterized from budbreak to leaf fall, and carboydrate reserves in stems and roots was described for different times of plant material collected in the field, and argued based on phenological stages. The mixed buds had passed the stages of dormancy, budbreak, shoot elongation, bloom, fruition, leaf senescence and leaf fall successively. The curves of growth of the fruit had shown the double sigmoidal standard and growth of fruit diameter preceded that of fresh and dry weight. Calyx growth stabilized in the end of the last stage of fruit development. From budbreak, in the end of winter to the maturation of fruits, in the beginning of autumn was recorded 199 days. Only seedless fruits were produced. From flowering to fruit maturity 161 days was registered. Two peaks in the abortion of fruits had occurred. The first symptoms of leaf senescence had been registered from the last stage of fruit development, two months after the canopy have been concluded. From budbreak to the complete leaf fall 287 days was recorded during all the spring, summer and autumn growing seasons. Starch and total soluble sugars content fluctuated in roots and stems throughout (P≤0,05) phenologycal stages of persimmons tree. Starch fluctuations showed to be more prone to significant variations in relation to the total soluble sugars in the stems as in the root. Two peaks of starch depletion was registered. The stem and root tissue started to accumulate starch during the net exporting photoassimilates by leaf photosynthesis. These results indicate that root and stem tissues play a role as a carbohydrate reserve pools to be mobilized for shoot elongation, flowering and for the maintenance of the tree during the lack of photosynthesis activity of persimmon tree.

In the Zapotitan Valley near San Andres, El Salvador, Central America, an experiment was conducted to determine the availability of residual soil N to corn grown during the rainy season. This was an extension of an experiment conducted during the preceding dry season. The variables of the dry season experiment were irrigation method, crop, and rate of fertilizer N application. Soil N03-N and NH4-N were determined by soil sample analysis to a soil depth of 120 em by 30 em depth increments. The samples were taken at the end of the dry season experiment and again at harvest time of the wet season experiment. Yield of corn grown during the rainy season was measured. The results indicate the following: (1) soil N03-N alone was an efficient indicator of residual soil N; (2) there was a linear increase of soil N03-N with N applied four months previously at the beginning of the dry season crops; (3) soil sampled to the 30 cm depth was sufficient to estimate availability of the residual N; (4) corn yields increased linearly with the increase of soil N03-N; (5) the measurement of residual soil N03-N can be used as a soil text index in connection with N prediction equations for estimating fertilizer N requirements. The measurements of soil N03-N can, therefore, increase the efficiency of fertilizer use in a wet-dry tropical climate.

The Wind-Evaporation-Sea Surface Temperature (WES) feedback is believedto play an important role in the tropics, where climate variability is governed byatmosphere-ocean coupled interactions. This dissertation reports on studies to distinctlyisolate the WES feedback mechanism over tropical oceans using a modiedversion of an NCAR-Community Climate Model (CCM3) thermodynamically coupledto a slab ocean model, where the WES feedback is deliberately suppressed inthe bulk aerodynamic formulation for surface heat uxes. A comparison of coupledintegrations using the modified WES-off CCM3 to those carried out using the standardCCM3 conclusively identifies the role of the WES feedback in enhancing theinter-annual variability over deep tropical oceans and the westward propagation ofthe equatorial annual cycle. An important role for near surface humidity in tropicalclimate variability in enhancing inter-annual variability and in sustaining the equatorialannual cycle is also suggested. Statistical analyses over the tropical Atlanticreveal that the free coupled meridional mode of the Atlantic Ocean is amplified in thepresence of the WES feedback. Similar analyses of coupled model integrations, whenforced with an articial El Ni~no Southern Oscillation (ENSO)-like SST cycle in tropicalPacific, reveal that only in the presence of the WES feedback is the meridionalmode the preferred mode of response of the Atlantic to ENSO forcings. It is also foundthat WES feedback reinforces the tendency of the ITCZ to stay north of the equator over the Atlantic during El-Nino events. Comparative studies between Last GlacialMaximum (LGM) equivalent imposed northern hemispheric sea-ice experiments withthe WES-off model and the standard model indicate a dominant role for the WESfeedback in the southward shift of the ITCZ as indicated by paleo-climate records.However, it is found not to be the sole thermodynamic mechanism responsible for thepropagation of high latitude cold SST anomalies to the tropics, suggesting significantroles for other mechanisms in the tropical response to high latitude changes.

The Wind-Evaporation-Sea Surface Temperature (WES) feedback is believedto play an important role in the tropics, where climate variability is governed byatmosphere-ocean coupled interactions. This dissertation reports on studies to distinctlyisolate the WES feedback mechanism over tropical oceans using a modiedversion of an NCAR-Community Climate Model (CCM3) thermodynamically coupledto a slab ocean model, where the WES feedback is deliberately suppressed inthe bulk aerodynamic formulation for surface heat uxes. A comparison of coupledintegrations using the modified WES-off CCM3 to those carried out using the standardCCM3 conclusively identifies the role of the WES feedback in enhancing theinter-annual variability over deep tropical oceans and the westward propagation ofthe equatorial annual cycle. An important role for near surface humidity in tropicalclimate variability in enhancing inter-annual variability and in sustaining the equatorialannual cycle is also suggested. Statistical analyses over the tropical Atlanticreveal that the free coupled meridional mode of the Atlantic Ocean is amplified in thepresence of the WES feedback. Similar analyses of coupled model integrations, whenforced with an articial El Ni~no Southern Oscillation (ENSO)-like SST cycle in tropicalPacific, reveal that only in the presence of the WES feedback is the meridionalmode the preferred mode of response of the Atlantic to ENSO forcings. It is also foundthat WES feedback reinforces the tendency of the ITCZ to stay north of the equator over the Atlantic during El-Nino events. Comparative studies between Last GlacialMaximum (LGM) equivalent imposed northern hemispheric sea-ice experiments withthe WES-off model and the standard model indicate a dominant role for the WESfeedback in the southward shift of the ITCZ as indicated by paleo-climate records.However, it is found not to be the sole thermodynamic mechanism responsible for thepropagation of high latitude cold SST anomalies to the tropics, suggesting significantroles for other mechanisms in the tropical response to high latitude changes.

Forensic anthropology, forensic taphonomy and forensic entomology are specialties that greatly contribute to judicial investigations and the identification of a decomposing corpse. This research examines the effect of calcium oxide (CaO), known as “quicklime”, on the decomposition process of human remains in a tropical climate. Quicklime has been used since the Early Iron Age, in wars, mass graves and today by criminals, as there is a belief or social myth that it can speed up the process of decomposition of bodies. However, there are no studies on the effect of this chemical on decomposing bodies in a tropical climate. Puerto Rico, in addition to having this climate, has a high crime rate related to drug trafficking. This study uses a series (n=10) of pig (Sus scrofa) burials as a model for human corpses, which were documented through photographs and state of decomposition, as well as climatic conditions, soil pH, odor of decomposition, and the lost mass. The author hypothesizes that the tropical climate contributes to the rapid decomposition of bodies by altering their appearance and morphology; since it is warmer, bacteria multiply more quickly and the entomofauna is more active, in comparison with studies already carried out in temperate climates. In addition, quicklime helps soft tissue decomposition proceed faster and reduces decomposition odor. Among the results, it was observed that there was no acceleration in the decomposition process due to the application of calcium oxide, and this chemical does not have the qualities attributed to it by social myths regarding the complete destruction of human remains, which could be considered an advantage for investigators in cases where there is a buried corpse covered in quicklime. However, it was possible to show that among other effects of quicklime, it subjectively reduces the odor of decomposition, inhibits and/or reduces the activity of the entomofauna, maintains a soil with an alkaline pH and therefore caused the mummification of the body. It can be suggested that the tropical climate helps in an effective decomposition due to the high temperatures, the humidity, and the activity of the entomofauna. Therefore, in both temperate and tropical climates, quicklime does not accelerate the decomposition process, but in a tropical climate it can inhibit the activity of entomofauna and the odor of decomposition. Statistically, results show that the Total Body Score (TBS) did not vary significantly, but the percentage of Mass Loss (ML) had a statistical difference due to the adhesion of the compacted quicklime to the experimental carcasses which increased the overall mass and not because a difference in the actual tissue loss was measured. This is since the decay process almost stopped after 77 days of burial and the mass loss nearly ceased, because with more days of rain and humidity, the more chemical reaction quicklime does (turning it into hydrated lime), causing solidification and mummification in the experimental pig carcasses. The quicklime also maintained an alkaline pH in the pig carcasses compared to the acidic pH of the controls after the decomposition. Therefore, quicklime causes a very sudden dehydration, and, in this sense, it prevents the proliferation of bacteria and, therefore, putrefaction, causing a mummification process. In addition, with the results obtained in this investigation and in other future ones, it will be possible to add scientific, anthropological, and forensic data on the analysis of the effects of quicklime in the stages of decomposition of human remain and in different deposition environments, to establish the time elapsed between death and the moment in which the body has been buried (exposed or not to quicklime) and contribute to criminal cases.

Although studies on stable-carbon isotopes in trees from temperate zones provide abundant paleoclimatic data, tropical trees are still understudied in this context. Therefore this study examined the variability of intra- and inter-annual stable-carbon isotopic pattern in several tree species from various tropical climates. The 𝛿¹³C values of samples of 12 broadleaved trees (seven species) from various paleotropical and neotropical sites along a climatic moisture gradient were investigated. The inter-annual variability between species and sites was studied. Further the relationship between 𝛿¹³C and precipitation time series was analyzed. Results show that tropical tree species show a similar variability in carbon isotopic composition as temperate tree species. Significant correlations between annual precipitation and tree-ring 𝛿¹³C time series were negative. Successful crossdating of a tree-ring 𝛿¹³C time series highlights the potential of carbon isotope measurements for tropical tree-ring analytical studies. Tropical broadleaved trees are able to capture a carbon isotopic signal in their annual rings even under everwet conditions and show good potential for paleoclimatic research.

Gravity waves play a fundamental role in driving the large-scale circulation of the atmosphere. They are influenced both by the variation in their sources and the filtering effects of the winds they encounter as they ascend through the atmosphere. In this thesis we present new evidence that gravity waves play a key role in coupling the troposphere, stratosphere and mesosphere. In particular, we examine the connection of gravity waves to two important large-scale oscillations that occur in the atmosphere, namely the Madden-Julian Oscillation (MJO) in the troposphere and the Mesospheric Semi-Annual Oscillation (MSAO). We present the first ever demonstration that the MJO acts to modulate the global field of gravity waves ascending into the tropical stratosphere. We discover a significant correlation with the MJO zonal-wind anomalies and so suggest that the MJO modulates the stratospheric gravity-wave field through a critical-level wave-filtering mechanism. Strong evidence for this mechanism is provided by consideration of the winds encountered by ascending waves. The Ascension Island meteor radar is used for the first time to measure momentum fluxes over the Island. These measurements are then used to investigate the role of gravity-wave in driving a dramatic and anomalous wind event that was observed to occur during the first westward phase of the MSAO in 2002. Gravity waves are shown to play an important role in driving this event, but the observations presented here also suggest that the current theory of the mechanism describing these anomalous mesospheric wind events is not valid. Both of these studies highlight the critical importance of gravity waves to the dynamics of the atmosphere and highlight the need for further work to truly understand these waves, their processes and their variability.

O solo é um recurso natural essencial para os seres humanos. Porém, atualmente, as atividades humanas estão provocando a degradação do solo principalmente através da aceleração dos processos erosivos. Os estudos sobre estes processos ajudam na compreensão, interpretação e conservação do solo. Assim, este trabalho pretende estudar e datar os processos erosivos em uma voçoroca localizada na Estação Experimental de Tupi (Piracicaba SP) mediante o uso da dendrogeomorfologia. A dendrogeomorfologia é uma ciência relativamente recente que relaciona os anéis de crescimento das árvores com processos geomorfológicos permitindo a reconstrução cronológica e ocorrência dos eventos. A relevância deste estudo é conhecer o potencial desta ciência em áreas tropicais já que atualmente este tipo de estudos são escassos nestas áreas. Esta técnica foi aplicada utilizando raízes expostas de espécies do gênero Pinus sp. A datação do processo erosivo baseou-se nas mudanças no padrão de crescimento das raízes, tais como: a largura do anel, crescimento excêntrico, porcentagem do lenho tardio e densidade do lenho ocorridas após a sua exposição pelo processo erosivo. Através do estudo destas alterações determinou-se o primeiro ano de exposição da raiz e se calculou a taxa de erosão anual. Os resultados mostraram que a voçoroca está formada pela integração de dois sistemas de diferentes origens que confluem em um degrau de erosão. A abertura das voçorocas está influenciada pela presença de processos de \"piping\" na área, os quais também afetam a morfologia das raízes quando enterradas. A taxa de erosão vertical, segundo o método de GÄRTNER (2007), atingem valores entre 17,0 e 36,5 mm/ano quantificando o processo de afundamento da voçoroca; e a taxa de erosão horizontal, segundo o método de MALIK (2008), valores de 0,70 e 1,45 m/ano caracterizando o avanço longitudinal da mesma. Estes resultados são elevados se comparados com resultados obtidos em climas temperados por outros autores e similares aos publicados por BOVI (2013) na mesma área de estudo. Finalmente, a dendrogeomorfologia se corrobora como uma ferramenta de grande potencial em áreas tropicais. Os dados e informações obtidos podem se traduzir num banco de dados dendrogeomorfológicos e contribuir à expansão desta ciência no Brasil e áreas de ambientes tropicais. / Soil is a vital natural resource for humans. However today, human activities are causing soil degradation mainly by accelerating soil erosion. Studies of these processes help to understand, interpret and conserve the soil. This work aims to study and date the erosion in a gully located in the Experimental Station of Tupi (Piracicaba SP) using dendrogeomorphology. Dendrogeomorphology is a relatively new science that relates the growth tree rings with geomorphological processes allowing chronological reconstruction and occurrence of events. The relevance of this study is to know the potential of this science in tropical areas because currently this type of studies are lacking in these areas. This technique was applied using exposed roots of species of Pinus sp. The dating of the erosion process was based on the changes in the pattern of root growth, such as the width of the ring, eccentric growth, percentage of latewood and density of the wood that occur after exposure by erosion. Through the study of these changes the first year of root exposure was determined, and the annual rate of erosion was estimated. The results showed the gully is formed by the integration of two different systems that converge in an erosion step. The opening of the gully is influenced by the presence of piping in the area, which also affect the morphology of the roots when buried. The vertical erosion rate, according to the method of GÄRTNER (2007), reached values between 17.0 and 36.5 mm/year quantifying the deepenning process of the gully; and horizontal erosion rate according to the method of MALIK (2008), values of 0.70 and 1.45 m/year characterizing the longitudinal advancement of the gully. These results were high compared with results obtained in temperate climates by others authors, and similar to those published by BOVI (2013) in the same site. Finally, dendrogeomorphology demonstrates great potential as a tool in tropical areas. The data and information obtained can be translated into a dendrogeomorphological database and contribute to the expansion of this science in Brazil and areas of tropical environments.