Mineralogia do solo

A fase sólida dos solos é composta de uma fracção mineral e uma orgânica. Por sua vez, a fracção mineral divide-se em lotes de dimensões que apresentam diferenças em relação à mineralogia e ao comportamento químico. Os minerais do solo pertencem a dois grandes grupos: Minerais primários e minerais secundários. Os minerais primários são herdados do material originário; mantém-se praticamente inalterado na sua composição. Como exemplos de minerais primários que se podem encontrar nos solos, referem-se: quartzo, feldspatos, plagioclases, micas, piroxenas, anfíbolas, olivinas, etc. Os minerais primários do solo têm importância para a avaliação do grau de evolução do solo e da sua reserva mineral. Os minerais secundários do solo podem ter 3 origens: são sintetizados no próprio solo (in situ) a partir dos produtos da meteorização dos minerais primários menos resistentes; resultam de alterações da estrutura de certos minerais primários, que ocorrem também in situ; são herdados do material originário. Os minerais secundários mais frequentes no solo são: minerais de argila (silicatos de alumínio no estado cristalino – minerais de argila), silicatos não cristalinos; óxidos e hidróxidos de alumínio e ferro; carbonatos de cálcio e de magnésio. São bem definidas as relações entre o tipo de mineralogia do solo e a sua composição granulométrica

Formação do Solo - Processos de Meteorização

Quando se procura entender as razões das diferenças e da diversidade dos solos é indispensável analisar quais são os factores que influem na sua formação e evolução. Para entender a formação do solo é indispensável considerar não só os fenómenos que ocorrem no próprio perfil mas que, de um modo geral, o solo é o resultado de um balanço entre processos de formação e processos de degradação, como é o caso da erosão, entre muitos outros. À medida que se aproximam da superfície do planeta, as rochas vão procurando adaptar-se às condições existentes à superfície, onde as pressões baixas, as temperaturas baixas e variáveis e a abundância de água, contrastam de um modo geralmente bastante drástico com as condições que presidiram à génese dessas mesmas rochas. A meteorização é, então, o processo pelo qual as rochas se fragmentam e adaptam à superfície da Terra, de forma a procurarem um equilíbrio estável à superfície. Há dois tipos fundamentais de meteorização: a física e a química. Na meteorização física os produtos resultantes deste processo apresentam a mesma composição química da rocha original, ocorrendo apenas uma acção mecânica, que leva à facturação das rochas em fragmentos mais pequenos. Os mecanismos mais importantes são: Fissuração e Desagregação. Na meteorização química, os produtos resultantes deste processo apresentam uma composição química diferente da das rochas originais, o que é devido a terem ocorrido reacções químicas entre a rocha e os elementos da atmosfera. Em todo este processo, a água vai ser o agente principal. Assim, o grau de meteorização química vai depender da taxa de precipitação. À medida que se vai dando a meteorização de uma rocha, os produtos resultantes vão formando uma capa que é o chamado rególito, o qual pode ter uma espessura de alguns milímetros até centenas de metros, dependendo principalmente do tipo de clima

Cultural Practices Study, Soil Porosity and Water Management against Desertification Combat

To evaluate the long term effects of different cultural practices in the desertification combat, a comparative study between a dryland conservative cropping system of cereals and another more traditional one was done. The conservative system has had direct seeding along 10 consecutive years, while the traditional one has had soil tillage. On a soil of the type Chromic Vertisol in Portugal the continuity of the porous space and therefore the water dynamics of the soil were evaluated using 2D images. To have a better representation of the area under study, soil samples of 250 cm2 were analyzed. The results, demonstrated that the conservative system, induces an increase of the porous space continuity in depth. Thus, the cultural conservative practices produce alterations in the water regime of the soil, being an important strategy to adopt, as intervening factor in the hydrologic cycle and as a concrete action against desertification

Improving Soil Primary Productivity Conditions with Minimum Energy Input in the Mediterranean

A collective well-succeed enterprise for good agriculture worldwide is possible through the synergetic effects of a series of favourable factors, among them, basically that associated to an adequate management of agricultural practices, improvement in soil tillage technologies, soil protection and conservation measures, animal and plant-breeding programs, genetic engineering and plant fertilization, all practices directed to augment the potential net production and productivity of the best biological varieties or cultivars available. A modern, intensive agricultural production system requires high levels of energy inputs, as compared to a traditional system. One should, for instance, just compare these two different production systems in terms of their global efficiency, but the IPS brought some negative environmental impacts, now diagnosed worldwide. In the Mediterranean areas the seasonal distribution of precipitation is harmful to plant (crop) dry matter (DM) production which can be increased by adequately combining a good management of all input factors with a special care to natural resources protection, namely soil and water conservation. In this work two fertile soils were managed under two alternative (TS = traditional mechanized system and DS = direct-seeding system) production systems during a ten-year period and their physical and chemical characteristics were compared in terms of agro-physical optimization to produce DM. The parameters that have been evaluated were: soil profile evolution texture and coarse elements, bulk density and soil resistance to the penetrometer, consistency limits; aggregates stability, organic matter (SOM) and nitrogen (N) contents and C/N ratio, cation-exchange capacity (CEC) and associated parameters, pores connectivity and soil-water retention curve. From an agronomic perspective the DM production has been also estimated in order to evaluate the ecological sustainability of eventual improvements in soil-water conservation were justified by the alternative system. Results enable to conclude that, inter alia, the alternative system under the perspective of the “Conservation Agriculture Paradigm” (Dumanski, R. et al., 2006) revealed to be prone to conserve more soil and water resources with interesting marginal gain in water and so in DM production. These results are well in the scope of the international concerns on adopting improved common policies for food security and problems associated to water scarcity, worldwide

O Solo e suas Funções

A(s) Ciência(s) do Solo têm tipicamente um carácter pluridisciplinar. Entre essas ciências são tradicionalmente relevantes a Física, Química, Biologia e Mineralogia do Solo. Num sentido mais estrito o solo pode ser entendido como “material não consolidado, mineral ou orgânico, existente à superfície da terra e que serve de meio natural para o crescimento das plantas, constituída por partículas minerais, matéria orgânica, água, ar e organismos vivos.” É habitual atribuir 6 funções aos solos, 3 de natureza ecológica 2 de natureza técnico-industrial e 1 de natureza sócio-cultura

DELIMITING TREE TERRITORY FROM SOIL WATER BALANCE EQUATION: A CASE STUDY

A usual problem linked to the apparent complexity of soil-plant interactions with the climatic forcing (as rainfall) is the need to compute the “active soil depth” (zr), available for water storage. Moreover, zr truncates the bottom depth of the control soil column, where drainage takes place, in the computation framework of a supply-demand-storage approach, in solving the soil water balance (SWB) equation at a site. Since the difficulty to estimate zr can lead to arbitrariness to set an operational value to it, our objective was to derive zr as the integral value of a unique soil layer of homogeneous properties. Our experimental scheme to solve the SWB equation involved a sample of ten young, 5 to 6 years-old, evergreen cork-oak (Quercus suber L.) trees, grown on a sandy loam soil (porosity is s), nearby Évora, Portugal. To achieve that goal, we have assembled several measurements techniques to assess the relevant water mass flux density terms, in the soil-plant-atmosphere continuum, as expressed per unit horizontal ground surface area (Ap), so justified by dimensional analysis. A steady-state IRGA (Li-1600M) apparatus was used to measure a discrete time series on instantaneous maximum diffusive conductance (gs) of sunlit leaf samples from four trees, under saturating light and soil water comfort, during spring season (in 2002). Further, gs was up-scaled to the corresponding daily foliage transpiration rate (Tr), which, in turn, was scaled up to plant root water uptake rate (U), using the derived sunlit leaf area index (Li) as the linear scale factor. In the same time period, the mean soil water variation rate (∆S), as induced by U, has been thermo-gravimetrically determined on collected soil core samples. Both ∆S and Tr was related to the spring season depletion phase of the ASW, lasted for a 30-day long period, the volumetric soil water () residence time (RT), under site conditions. Assumption of water mass conservation for the SWB problem in the rooted soil, as well as for whole-plant water capacitance, implies U matches ∆S, the depth-integrated value of variation, throughout zr domain. Results showed zr can be estimated as a cumulative and directly proportional function of observed Tr and RT, without vertical discretization of the soil column. Model output showed an effective maximum rooting depth (or an equivalent lateral expansion) of 1754 mm (1.75 m), which is interpreted as the mean radius of an ellipsoidal zone of influence, in all directions; it was 1.32 times greater than the mean tree high. The product zr s gives the “effective” soil depth, ca. 0.70 m, in this case study. Extension of the approach can be either determining U for pounded water land use system (e.g., rice cultivation) or estimating the plant density in irrigated orchards, enhancing water management

Effects of Agricultural Land Use on the Ecohydrology of Small- Medium Mediterranean River Basins: Insights from a Case Study in the South of Portugal

Southern Europe has been experiencing an accelerated intensification of agricultural systems in the last decades with consequent environmental effects. This study aimed to evaluate the effects of agricultural land use in two small-medium river basins in the South of Portugal, regarding: (i) water quality and stream habitat; (ii) fish fauna; and (iii) soil. Sampling included fish captures, water, and soil sample collection. Hydromorphological habitat features were also assessed. Land use was quantified at the basin and local scales. Results showed that the most negative effects were associated with intensive, heavily irrigated, fertilized, and pastured local systems, mostly represented at the basin scale by olive groves, irrigated crops, and pastures. Conversely, local agricultural intensity did not prove to be a threat to the integrity and quality of the soil, seeming to ensure the sustainability of the local uses and their systems. Negative effects were observed on water quality and instream habitat and degradation of riparian vegetation, resulting in fish assemblages’ impoverishment. This study contributes to a comprehensive approach to the effects of agricultural land use, highlighting the need to integrate the results of different natural resources to efficiently support policy and decision makers toward a sustainable agriculture, water management, and land use planning

Genetic variation among and within Quercus suber L. populations in survival, growth, vigor and plant architecture traits

Cork oak is an important forest tree species in the Western Mediterranean region due to the high economic value of its renewable cork and its ecological and social services. However, studies regarding the genetic variation within cork oak populations are scarce, and this gap of knowledge is contributing to the delay of the set-up of a breeding and conservation strategy for the species. In this study, the genetic variation in fitness (survival, height, and stem diameter) and plant architecture traits (apical dominance, stem straightness, stem inclination degree, branchiness), and tree vigor was evaluated among and within cork oak populations in two progeny field trials established in Portugal. Measurements were carried out in each trial in two different periods: ages 9 and 14 years at Monte da Fava trial and 8 and 14 years at Herdade da Caniceira trial. A significant genetic variation among and within cork oak populations was detected for survival, growth, and form traits (stem straightness and inclination). Growth traits presented high values of heritability estimates at the family mean level (≥0.75), and genetic gains were obtained when families with superior growth were selected. Additionally, results highlighted that early selection of families with superior performance could be performed, and it is possible to achieve improvement in both growth and form traits simultaneously, with implications on the profitability and sustainability of cork oak standsinfo:eu-repo/semantics/publishedVersio

Efeitos do uso do solo na ecohidrologia de bacias hidrográficas

A ocupação e uso do solo, desempenham um importante papel nos fenómenos das mudanças globais constituindo um importante fator que afeta a integridade dos ecossistemas terrestres e aquáticos. Muitas bacias hidrográficas de regiões Mediterrânicas e semi-áridas, caracterizadas durante séculos por sistemas de produção agrícola em extensivo de sequeiro, nas últimas décadas sofreram uma mudança bastante acelerada nos sistemas de produção agrícola devido à perspetiva de uma agricultura de regadio rentável. Apesar do crescente reconhecimento dos impactos dos sistemas agrícolas intensivos, tem-se assistido a um forte incentivo à produção dirigido à intensificação de diversas culturas. Os sistemas de produção agrícola intensivos são caracterizados por uma elevada densidade de plantas, rega sistemática e colheita mecanizada, com incorporação de grandes quantidades de energia e água à custa dos recursos naturais. Estes sistemas associados a um clima em alteração onde os eventos extremos se estão a tornar mais frequentes e mais intensos, têm impactos ambientais negatives fortes, particularmente na erosão do solo, escoamento para corpos de água, degradação de habitats e exploração e contaminação de recursos aquáticos escassos, bem como na degradação dos ecossistemas aquáticos e perda de biodiversidade. A degradação da água e do solo estão largamente associadas à poluição difusa a qual surge em amplas áreas, tais como campos agrícolas ao longo das bacias hidrográficas sobretudo devido à fertilização irracional, rega e uso de pesticidas. As bacias hidrográficas agroflorestais tendem a estar sujeitas a alterações mais disruptivas do uso da terra, devido a ações forçadoras a que esta está sujeita anualmente. Com efeito, em cada ano, mais terra arável é lavrada para culturas arvenses de sequeiro ou, as culturas são cortadas sazonalmente, gerando assim pousios, culturas em linha, rotação de prados ou pastagens. Estas práticas levam a alterações na infiltração, aumentam a erosão e o potencial de contaminação do escoamento. Como resultado, características do solo como o teor em material orgânica, carbono, textura, capacidade de armazenamento de água e fertilidade química, podem alterar-se dramaticamente e os rios enfrentam elevadas chegadas de sedimentos e fertilizantes (principalmente fosfatos e nitratos) com consequências na permeabilidade do substrato, na qualidade da água e na integridade do biota aquático. Este fenómeno é particularmente agravado em regiões com elevada variabilidade no regime de precipitação, onde as cheias alternadas com períodos de seca, promovem condições que levam ao aumento da erosão do solo e perda de nutrientes, particularmente em bacias hidrográficas com elevadas alterações no uso e ocupação do solo. Assim, o objetivo deste estudo consistiu em avaliar o efeito do uso e ocupação do solo em duas pequenas bacias hidrográficas do Sul de Portugal, relativamente à composição do solo, qualidade da água e integridade do biota aquático, especificamente através da fauna piscícola. Apesar de preliminar, este estudo ilustra a relação entre os usos de solo e a integridade dos recursos naturais associados. O impacto dos agro-sistemas resulta do seu grau de intensificação mas também de múltiplas outras pressões a eles associadas, as quais individualmente ou em conjunto afetam o serviço dos ecossistemas de suporte às atividades humanas e à conservação da biodiversidade. Nesta perspetiva é importante que o ordenamento e gestão das bacias hidrográficas integrem uma visão de compromisso entre os usos de solo associados à intensificação dos sistemas agrícolas e a conservação dos recursos naturais e ecossistemas associados, por forma a promover o desenvolvimento sustentável da agricultura

Seed origin drives differences in survival and growth traits of cork oak (Quercus suber L.) populations

Cork oak (Quercus suber L.) has a high ecological and social value and supplies raw materials for the cork industry, a relevant contributor to the economies of Mediterranean countries. Understanding the adaptation potential of cork oak populations to cope with different environmental conditions is a key issue of forest management, particularly for selecting the most adapted genetic material for (re)forestation and assuring the long-term sustainability of the cork industry. Intraspecific variation in fitness surrogate traits (survival, height and stem diameter) was investigated in thirty-five cork oak populations sampled from the entire range of the natural distribution of the species. The study was conducted in two provenance field trials, established in Portugal under different edaphoclimatic conditions. Each trial was surveyed at four tree ages (two ages, 11 and 14 years, were sampled simultaneously in both trials). The trial located at a lower altitude, which had higher mean winter and annual temperatures, exhibited higher growth and survival rates. In both trials, significant genetic variation among cork oak populations was observed for the analyzed traits and evaluated ages. Moroccan populations displayed a higher probability of survival and higher growth rates, while local populations exhibited an intermediate performance. Low to moderate correlations were found between the analyzed traits and the environmental variables of seed origin, suggesting that factors other than climate are likely to be relevant for cork oak adaptation. Moderate to high values of population mean-basis broad-sense heritability (H2≥0.44) and high genetic correlations between traits (0.88–0.95) were found for growth traits. This information is crucial for the establishment of a breeding program for the species. With this study, we have improved the knowledge regarding how cork oak performs for fitness surrogate traits in different environments.The cork oak provenance field trials were funded by European (FAIR1-CT-95-0202) and national foundations (PBIC/AGR/2282/95, PAMAF 4027, PRAXIS/3/3.2/Flor/2110/95). The growth and survival measurements were assessed with the support of the European project: “CREOAK: Conservation and restoration of European cork OAK woodlands: a unique ecosystem in the balance” (QLK5–CT–2002–01594); and the “Repovoamento com sobreiro: Variabilidade genética e biologia da semente conservada (POCTI/41359/AGG/2001) national project. Research activities were also funded by Forest Research Centre (CEF), a research unit funded by Fundação para a Ciência e a Tecnologia I.P. (FCT), Portugal (UID/AGR/00239/2013). Teresa Sampaio was funded by the Portuguese Foundation for Science and Technology, Portugal through a doctoral grant under the SUSFOR Doctoral Programme (PD/ BD/52402/2013). The authors are thankful to Maria Carolina Varela who setting up the EU-concerted action on cork oak, FAIR I CT 95 0202 and to Carla Faria, Carla Leite and Regina Chambel that collaborated on the establishment of the Portuguese genetic trials. We also thanks to Ana Margarida Nunes, Lurdes Marçal, Madalena Silva, Maria João Lourenço and Sara Rocha for their support in field work.info:eu-repo/semantics/publishedVersio