Browsing by Author "Poesen, Jean"
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- Efeito das características dos elementos grosseiros na erosão inter-sulcos: um contributo para a sua modelaçãoPublication . Figueiredo, Tomás de; Ferreira, Alfredo Gonçalves; Gonçalves, Dionísio; Poesen, JeanO papel da pedregosidade tem vindo a merecer, nos últimos anos, crescente interesse no quadro dos estudos sobre erosão dos solos. Se por um lado é reconhecida a influencia das características dos elementos grosseiros na perda de solo, a incorporação desse efeito na modelação dos processos erosivos em solos pedregosos é ainda incipiente. Com o objectivo de testar o efeito de várias características dos elementos grosseiros na erosão inter-sulcos, foi conduzido um ensaio experimental, à micro-escala. Os resultados do ensaio permitiram calibrar modelos explicativos da influência dessas características na perda de solo por salpico e por escoamento difuso.
- O efeito do comprimento da encosta na erosão em solos pedregosos: modelo e aplicações em áreas de vinha do Vale do Douro, PortugalPublication . Figueiredo, Tomás de; Fonseca, Felícia; Ferreira, António G.; Poesen, Jean; Gonçalves, DionísioOs solos pedregosos cobrem a maior parte da faixa Mediterrânica, regra geral ocupando as zonas de elevado risco potencial de erosão, como por exemplo as superfícies de relevo ondulado e as áreas de montanha. Tratando-se de terras cultivadas, muitas vezes desde longa data, às condições topográficas junta-se o uso do solo como factor potenciador do risco de erosão. A aplicação de medidas de controlo da erosão impõe-se nestas condições e o comprimento da encosta é um factor de erosão que, na prática, muito condiciona o dimensionamento dessas medidas, especialmente quando se trata de medidas estruturais ou de carácter mecânico destinadas ao controle do escoamento superficial. Todavia, o efeito deste factor é reconhecidamente complexo visto que representa a expressão final do processo de transferência de água e sedimento ao longo da encosta, muito afectado por outros factores que não os estritamente associados à topografía dos terrenos. A pedregosidade superficial dos solos é um deles. Este trabalho tem o propósito de apresentar e discutir um modelo descritivo do efeito da pedregosidade superficial dos solos na transferência de sedimento ao longo da encosta, e de o explorar com aplicações em áreas de vinha do Vale do Douro, Portugal. O modelo considera os parâmetros de caracterização dos elementos grosseiros do solo e deduz o modo como estes contribuem para a retenção de partículas num segmento da encosta. As expressões de cálculo deduzifas são justificadamente apresentadas, bem como o suporte experimental que permitiu calibrá-las. Na sua aplicação ao contexto do Vale do Douro consideraram-se as vinhas plantadas segundo o maior declive (vinhas ao alto) como exemplo. As simulações efectuadas com o modelo permitem explicar resultados experimentais e evidencias no terreno, e formular recomendações para a concepção de planos de conservação do solo à escala da parcela cultivada.
- Effects of rock fragments on physical degradation of cultivated soils by rainfallPublication . Van Wesemael, Bas; Poesen, Jean; Figueiredo, Tomás deTo understand better the role of rock fragments in soil and water conservation processes, the effects of rock fragments in maintaining a favourable soil structure and thus also in preventing physical degradation of tilled soils was studied. Laboratory experiments were conducted to investigate the effects of rock fragment content, rock fragment size, initial soil moisture content of the fine earth and surface rock fragment cover on soil subsidence by rainfall (i.e. change in bulk density by one or more cycles of wetting and drying). A total of 15 rainfall simulations (cumulative rainfall, 192.5 mm; mean intensity, 70 mm h−1) were carried out. Before and after each rainfall application the surface elevation of a 19-cm thick plough layer was measured with a laser microrelief meter. In all experiments, the bulk density of the fine earth increased with applied rainfall volume to reach a maximum value at about 200 mm of cumulative rainfall. From the experimental results it was concluded that the subsidence rate decreased sharply for soils containing more than 0.50 kg kg−1 rock fragments, irrespective of rock fragment size. Fine earth bulk densities were negatively related to rock fragment content beyond a threshold value of 0.30 kg kg−1 for small rock fragments (1.7–2.7 cm) and 0.50 kg kg−1 for large rock fragments (7.7 cm). Initial soil moisture content influenced subsidence only in the initial stage of the experiments, when some swelling occurred in the dry soils. Surface rock fragment cover had no significant effect on subsidence of the plough layer. Therefore, subsidence of the plough layer in these experiments appears to be mainly due to changing soil strength upon drainage rather than the result of direct transfer of kinetic energy from falling drops. The relative increase in porosity of the fine earth as well as the absolute increase in macroporosity with rock fragment content will cause deeper penetration of rainfall into the soil, resulting in water conservation. Therefore, crushing of large rock fragments into smaller ones is to be preferred over removal of rock fragments from the plough layer.
- Effects of surface rock fragment characteristics on interrill runoff and erosion of a silty loam soilPublication . Figueiredo, Tomás de; Poesen, JeanThe role played by rock fragments in water erosion has received much attention in recent years. Knowledge of the effects of rock fragment characteristics on interrill erosion is incomplete. Hence, in order to investigate these effects on a small scale, a simulation experiment was conducted in Bragança, Northeast Portugal. The experimental setup consisted of 48 bottom perforated rectangular metal boxes (612 cm2), placed at a 10% slope, filled with 3.5 cm of a sieved silty loam soil over 2 cm of sand, covered by simulated rock fragments and maintained at near saturation. Twelve treatments, four replicates each, were exposed to 240 mm natural rainfall, comprising selected combinations of rock fragments size (small, medium—gravel range, and large—stone range), shape (rectangular and circular), position (surface, half-embedded and embedded) and cover percentage (17, 30 and 66%), and bare soil. Infiltration depth, runoff depth, washed and splashed sediment were repeatedly measured in appropriate collection devices. For bare soil, total wash and total splash were equivalent to 42.2 g m−2 and 70.6 g m−2, respectively. Infiltration and runoff represented 52% and 13% of total rainfall, respectively. Wash has a negative exponential relationship with rock fragment cover (RC). The regression coefficient varies negatively with cumulative precipitation, decreasing significantly after a surface seal is formed (at about 80 mm cumulative precipitation). The relationship between splash and RC, linear and negative, varies with time, too. Correlation with RC is positive for infiltration depth and negative for runoff depth, both reflecting the seal development with time. The effects of rock fragments size, position and form were tested for 30% RC. Size has a positive effect on runoff depth, wash and splash, and a negative effect on infiltration depth. The effect of rock fragment size on infiltration, runoff and erosion is more pronounced than that of position. The effect of shape was less significant than that of size and position.
- Effects of wind driven rainfalls on soil loss from a Douro vineyard, PortugalPublication . Figueiredo, Tomás de; Poesen, Jean; Hernández, Zulimar; Fonseca, FelíciaIn permanent row crops, rainfall interception by canopies in rows varies according to wind direction and this may affect raindrop impact and erosion in the inter-row area. The paper aims at discussing the effects of wind direction during rainfalls on soil loss from vineyard plots with different slope aspect in the Douro Region, Portugal. Long term continuous rainfall records, daily wind direction, and soil loss from 5 plots (32m long x 5n wide), in a 45% slope row‐planted vineyard, with slope aspect from NW to SW, were explored separating events only with water loss (NER, 67 non‐erosive events) from the others (ERO, 100 erosive events), and considering for each event wind direction at peak rainfall intensity. Calm atmosphere prevailed but with lower frequency in ERO (65%) than in NER (72%). Most frequent winds were NW (20%) and S (11%) in ERRO, and SE (12%) and NW (7%) in NER. Wind direction affected the differences between plots in event soil loss (expressed by the CV of the 5 plots soil loss in each event), with a CV 90% for NW winds, 37% for S, and 33% for Calm. NW winds blow parallel to vine rows in some plots and almost perpendicular in the others and this effect was most evident during the larger erosion events when lowest to highest plot soil loss ratio reached 1:50. These results may contribute to better tune the application of conservation measures in Douro vineyards considering plot location and dominant wind direction.
- Eficácia no controlo da erosão de medidas de gestão do solo baseadas em coberturas herbáceas: simulações para a viticultura do Douro, PortugalPublication . Figueiredo, Tomás de; Hernández, Zulimar; Fonseca, Felícia; Poesen, JeanA gestão do solo (GS) convencional na viticultura do Douro, Portugal, compreende mobilizações para controlo das infestantes ao longo do ciclo cultural. Práticas alternativas de GS reduzem ou excluem as mobilizações, mantendo o solo coberto grande parte do ano. Com o propósito de comparar o desempenho relativo no controlo da erosão de práticas alternativas de GS, este estudo utilizou registos de longo prazo de uma vinha na Quinta de Santa Bárbara, Pinhão (estado vegetativo das videiras, operações culturais e precipitação). Aplicouse o fator C da Equação Universal de Perda de Solo, combinando o efeito das coberturas da linha de plantação pelas videiras e da entrelinha por vegetação herbácea e resíduos sobre o solo, ao longo do ciclo típico das vinhas, e considerando a distribuição temporal da erosividade da precipitação. A variação do fator C calculado estima o desempenho das práticas de GS convencional e alternativa, com diferentes densidades, datas de remoção e níveis de resíduos da vegetação herbácea na entrelinha. Os resultados mostram que o nível de resíduos sobre o solo após o controlo de infestantes é mais decisivo (aumento de 54% no controlo da erosão para 80 % de cobertura por resíduos na entrelinha) do que o atraso na data de controlo das infestantes (aumento de 37% para atraso até meados de Julho), sendo menos evidente o efeito da densidade da cobertura herbácea, semeada (aumento de 17% para 80 % de cobertura da entrelinha). Espera-se que a abordagem e os resultados deste estudo contribuam para afinar práticas de controlo da erosão na viticultura do Douro.
- Eficácia no controlo da erosão de medidas de gestão do solo baseadas em coberturas herbáceas: simulações para a viticultura do Douro, PortugalPublication . Figueiredo, Tomás de; Hernández, Zulimar; Fonseca, Felícia; Poesen, JeanA gestão do solo (GS) convencional na viticultura do Douro, Portugal, compreende mobilizações para controlo das infestantes ao longo do ciclo cultural. Práticas alternativas de GS reduzem ou excluem as mobilizações, mantendo o solo coberto grande parte do ano. Com o propósito de comparar o desempenho relativo no controlo da erosão de práticas alternativas de GS, este estudo utilizou registos de longo prazo de uma vinha na Quinta de Santa Bárbara, Pinhão (estado vegetativo das videiras, operações culturais e precipitação). Aplicouse o fator C da Equação Universal de Perda de Solo, combinando o efeito das coberturas da linha de plantação pelas videiras e da entrelinha por vegetação herbácea e resíduos sobre o solo, ao longo do ciclo típico das vinhas, e considerando a distribuição temporal da erosividade da precipitação. A variação do fator C calculado estima o desempenho das práticas de GS convencional e alternativa, com diferentes densidades, datas de remoção e níveis de resíduos da vegetação herbácea na entrelinha. Os resultados mostram que o nível de resíduos sobre o solo após o controlo de infestantes é mais decisivo (aumento de 54% no controlo da erosão para 80 % de cobertura por resíduos na entrelinha) do que o atraso na data de controlo das infestantes (aumento de 37% para atraso até meados de Julho), sendo menos evidente o efeito da densidade da cobertura herbácea, semeada (aumento de 17% para 80 % de cobertura da entrelinha). Espera-se que a abordagem e os resultados deste estudo contribuam para afinar práticas de controlo da erosão na viticultura do Douro.
- Erosional response of steep slope vineyards to wind driven rainfalls: a case study in the Douro Region, PortugalPublication . Figueiredo, Tomás de; Poesen, Jean; Fonseca, Felícia; Hernández, ZulimarIn permanent row crops, wind direction affects the rainfall that hit the ground, with consequences to runoff and soil loss, because rows may intercept a large or a negligible part of the wind driven rains, according to the relative directions of wind and plant row. This study aims at identifying and discussing the effects of wind direction during rainfalls on soil loss from vineyard plots with different slope aspect. Data from 5 erosion plots (32m long x 5n wide), installed in the Douro valley (Portugal), in 45% slope row‐planted vineyard, with slope aspect from NW to SW, consisted in long term data series of continuous rainfall records, daily wind direction, and soil loss, were explored separating events only with water loss (NER, 67 non‐erosive events) from the others (ERO, 100 erosive events), and assuming for each event wind direction at peak rainfall intensity. Calm atmosphere prevailed but with lower frequency in ERO (65%) than in NER (72%). Most frequent winds were NW (13%) and S (12%) in ERRO, and SE (12%) and NW (7%) in NER. Wind direction affected the differences between plots in event soil loss (expressed by the CV of the 5 plots soil loss in each event), with a CV 100% for NW winds, 49% for S, and 63% for Calm. NW winds blow parallel to vine rows in some plots and almost perpendicular in the others. This effect was most evident during the larger erosion events (1:50 ratio in event soil loss in SW plot and NW plot, during a NW driven rainfall). In permanent row crops, the effect of wind direction during erosive rainfalls should be taken into account when analyzing plot soil loss data, especially in the most significant events.
- Estimating erosion control performance of soil management practices in Douro viticulturePublication . Figueiredo, Tomás de; Hernández, Zulimar; Fonseca, Felícia; Poesen, JeanConventional soil management (sm) in Douro viticulture, Portugal, comprise several weed control tillage operations along the crop cycle. Alternative sm practices reduce or exclude tillage, keeping ground cover for large part of the wetter seasons. Aiming at comparing the relative performance in erosion control of alternative sm practices, this study used long term records from a Douro vineyard as vine and ground vegetation evolution, crop management operations and detailed rainfall data. The USLE C factor was calculated combining vine row cover and inter-row ground cover effects in the typical vine cycle. With rainfall erosivity temporal distribution, erosion control by ground vegetation management options, representing different sm practices, was assessed for conventional and alternative (imposing different ground vegetation density, removal date and residues level after weed control). Results compare relative soil protection performance of alternative sm practices with conventional sm. Leaving residues over ground after weed control works better (54% increase in erosion control for 80% residue cover), than delaying weed control date (37% increase for a delay to mid-July), while increasing sown ground vegetation density is not so effective (17% increase for 80% cover). The methodological approach and results of this study are expected to contribute to better adjust sm practices for erosion control in Douro viticulture.
- Long term erosion rates in Douro vineyards, Portugal: effects of rainfall characteristics and plant densityPublication . Figueiredo, Tomás de; Poesen, Jean; Fonseca, Felícia; Hernández, ZulimarThe Douro Region, NE Portugal, where the grapes for Port Wine are produced, faces a high potential erosion risk due to its natural setting, for long tackled with heavy labour inputs. These allowed the stabilization of steep vineyard covered hill-slopes by means of traditional terracing, manually built and following models that changed through time. Alternative vineyard installation and cultivation techniques were tested and progressively adopted, namely row plantation perpendicular to the contour, nowadays an integral yet small part of the plantation schemes accepted under the rules of the World Heritage status, granted by UNESCO in 2001. This paper investigates the effects of vine plantation schemes on longterm (I 0 years) runoff and soil loss data recorded in the Douro Region using a set of meso-scale erosion plots installed in vineyards planted in rows perpendicular to the contour. It also aims at identifying, and quantitatively deriving the significance of erosion factors helping to interpret the results obtained, namely rainfall characteristics and vine plant density. Runoff and soil loss were measured in five plots, 32.1 m long and 5.2 m wide, on a 45% slope, over a silt loam soil containing 60% rock fragments by mass, under Mediterranean climatic regime with less than 600 mm mean annual rainfalL Vine plantation schemes tested correspond to three different plant densities (3571, 4808, 5917 plants ha·1) on paired plots (except for the intermediate plant density, tested in a single plot), which provided a mean vegetation cover of 50, 60 and 75%, respectively. The 10 year data analyzed correspond to 167 runoff events. Mean annual runoff and soil loss were 22 mm and 361 kg ha·1, respectively. These relatively low soil loss rates are explained by the very high rock fragment cover, protecting the topsoil from wash by runoff. Soil loss was very much concentrated in a few erosive events, 3 of them being responsible for ca.75% of the total soil loss recorded in 10 years. These events occurred in spring and summer, whereas most erosive events in Mediterranean conditions occur in autumn and winter. Results also show that increasing the vine plant density by 66% resulted in a reduction of mean annual runoff by 19% and of mean annual soil loss by 57%, demonstrating the significant effect on erosion control of platation scheme decisions taken prior to the installation of permanent crops such as vineyards.