Uso da terra e riscos de degradação do solo no Nordeste de Portugal: mudanças nas últimas décadas

O NE de Portugal está, em extensas áreas, sujeito a degradação do solo, num quadro de suscetibilidade à desertificação e de elevado perigo de incêndio. As mudanças recentes nos padrões de uso da terra vêm suscitando interpretações por vezes contraditórias quanto às suas consequências para o recurso solo. Propõe-se neste trabalho discutir os resultados de uma avaliação diacrónica do quadro de riscos de degradação do solo nas últimas décadas no NE de Portugal. As legendas da Carta do Uso da Terra (1987) e da Carta de Ocupação do Solo (2007) foram compatibilizadas quanto às grandes categorias de uso (agricultura, floresta, matos). Foi definido o quadro de riscos de degradação do solo pelo grau de adequação do uso à aptidão da terra, distinguindo-se áreas em sobre-exploração, com uso adequado e em sub-exploração do recurso solo. Revelam-se tendências na evolução da ocupação do solo já conhecidas em Portugal, com redução das áreas agrícolas e incremento dos matos, que se traduzem na diminuição em cerca de 14% da área em sobre-exploração da terra, e num aumento da área em uso adequado (8%) e em sub-exploração (6%). Os resultados, mostrando uma redução desejável na ameaça ao recurso solo, são discutidos considerando a extensão ainda significativa das áreas em sobre-exploração (44%), bem como o acréscimo potencial de outras ameaças ao recurso solo, como o perigo de incêndio, devido ao aumento estimado em 14% em 20 anos nas áreas combustíveis sujeitas a controle social escasso – os matos.info:eu-repo/semantics/publishedVersio

Viñedos en terrazas en la región vitivinícola del Duero, Portugal: una perspectiva de la gestión del suelo y el agua

The Douro vineyards are a striking example of soil protection materialized in a strongly humanized landscape, where terraces cover a large part of the region. The paper aims at presenting a perspective on soil and water management improvements for Douro terraced vineyards, as a response to actual responsibilities determined by the UNESCO World Heritage statute in preserving a cultural, living and evolutional landscape. After stressing the importance of Douro terraced vineyards in the Portuguese Continental territory and the natural constraints for crop production characterizing the Douro valley, terrace types present in Douro landscapes are described, together with soil changes with terracing operations. Besides the rehabilitation of drystone structures as part of the preservation interventions on the region’s cultural heritage, critical risk areas in recently terraced hillslopes are identified as a priority for soil protection and water management interventions. These are the vineyard areas most expose to direct impact of erosive rainfalls and comprise the inter-row lanes, especially in non-terraced vineyards, the earthen bare risers in recent terraces, and the farm road and drainage networks, spatially coincident, in steep extensively planted hillslopes. Innovative soil and water management practices have to be developed and locally tested in close dialog with regional actors.info:eu-repo/semantics/publishedVersio

Uso da terra e riscos de degradação do solo no Nordeste de Portugal: mudanças nas últimas décadas

O NE de Portugal está, em extensas áreas, sujeito a degradação do solo, num quadro de suscetibilidade à desertificação e de elevado perigo de incêndio. As mudanças recentes nos padrões de uso da terra vêm suscitando interpretações por vezes contraditórias quanto às suas consequências para o recurso solo. Propõe-se neste trabalho discutir os resultados de uma avaliação diacrónica do quadro de riscos de degradação do solo nas últimas décadas no NE de Portugal. As legendas da Carta do Uso da Terra (1987) e da Carta de Ocupação do Solo (2007) foram compatibilizadas quanto às grandes categorias de uso (agricultura, floresta, matos). Foi definido o quadro de riscos de degradação do solo pelo grau de adequação do uso à aptidão da terra, distinguindo-se áreas em sobre-exploração, com uso adequado e em sub-exploração do recurso solo. Revelam-se tendências na evolução da ocupação do solo já conhecidas em Portugal, com redução das áreas agrícolas e incremento dos matos, que se traduzem na diminuição em cerca de 14% da área em sobre-exploração da terra, e num aumento da área em uso adequado (8%) e em sub-exploração (6%). Os resultados, mostrando uma redução desejável na ameaça ao recurso solo, são discutidos considerando a extensão ainda significativa das áreas em sobre-exploração (44%), bem como o acréscimo potencial de outras ameaças ao recurso solo, como o perigo de incêndio, devido ao aumento estimado em 14% em 20 anos nas áreas combustíveis sujeitas a controle social escasso – os matos.info:eu-repo/semantics/publishedVersio

Estimating erosion control performance of soil management practices in Douro viticulture

Conventional 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.info:eu-repo/semantics/publishedVersio

Effects of wind driven rainfalls on soil loss from a Douro vineyard, Portugal

In 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.info:eu-repo/semantics/publishedVersio

Assessing performance of post-fire hillslope erosion control measures designed for different implementation scenarios in NE Portugal: simulations applying USLE

Wildfires are common in NE Portugal, annually affecting large areas and contributing to increase soil degradation in a territory under severe erosion risk. Wildfires dominantly occur in forests and scrubland that cover mountain areas all over the region. Post-fire measures, required for erosion control in such hillslopes, if applied, currently lack background design. The research aimed at assessing the performance of erosion control measures in hillslopes representing different implementation scenarios in Bragança District, NE Portugal (6608 km2). Methodology applied involved building up regional scenarios for simulated application of common post-fire measures (seeding and contour barriers), using USLE procedures. Variability of precipitation, soil and slope gradient across the region was represented by 14 simulation scenarios, for which potential erosion was calculated with USLE R, K and S factors, regionally assessed in previous work by the authors. Scenarios correspond to a range of susceptibility of burnt areas across the region, represented by potential erosion. Different sediment retention degrees and spacing of contour barriers (made with burnt vegetation residues) were simulated, exploring USLE L factor to estimate their effectiveness in reducing erosion. Seeding herbaceous vegetation as a post-fire measure was simulated applying USLE C factor and considering vegetation growth rates typical of each scenario. Post-fire measures were classified according to their performance in reducing potential erosion to tolerable rates in the different implementation scenarios: low, moderate, and high performance with, respectively, erosion rates > 10 Mg ha-1 y-1, 10 – 2 Mg ha-1 y-1, and < 2 Mg ha-1 y-1. Seeding is a low performance measure and reseeding next post-fire year is recommended. Contour barriers show generally high performance, yet dependent on design parameters. In fact, increasing barrier retention degree is more effective than reducing the spacing between barriers, a result that highlights the need for well-built contour barriers. The combination of the two measures has a high performance in most scenarios, thus recommending its wide application across the region. These results point out the importance of adequately designed post-fire measures, adapted to the regional diversity of potential erosion conditions, in order to mitigate impacts and accelerate recovery of NE Portugal burnt areas.info:eu-repo/semantics/publishedVersio

Uso da terra e riscos de degradação do solo no Nordeste de Portugal: mudanças nos últimos trinta anos

O NE de Portugal está, em extensas áreas, sujeito a degradação do solo, num quadro de suscetibilidade à desertificação e de elevado perigo de incêndio. As mudanças recentes nos padrões de uso da terra vêm suscitando interpretações por vezes contraditórias quanto às suas consequências para o recurso solo. Propõe-se neste trabalho discutir os resultados de uma avaliação diacrónica do quadro de riscos de degradação do solo nos últimos trinta anos no NE de Portugal. Utilizando duas bases cartográficas (Agroconsultores e Coba, 1991, e COS 2007, nível 3), cujas legendas foram compatibilizadas de modo a permitir comparação entre as duas datas quanto às grandes categorias de uso da terra (agricultura, floresta, matos), foi definido o quadro de riscos de degradação do solo pelo grau de adequação do uso da terra à sua aptidão, como estabelecida em Agroconsultores e Coba (1991). Identificaram-se áreas em sobre-exploração (uso mais exigente do que a aptidão permitiria, representando por isso risco potencial de degradação do recurso), em uso adequado (coincidente com a aptidão), e em sub-exploração (uso menos exigente). Revelam-se tendências na evolução da ocupação do solo já conhecidas em Portugal, com redução das áreas agrícolas e incremento dos matos, que se traduzem na diminuição em cerca de 14% da área em sobre-exploração da terra, e num aumento da área em uso adequado (8%) e em sub-exploração (6%). Os resultados, mostrando uma redução desejável na ameaça ao recurso solo, são discutidos considerando a extensão ainda significativa das áreas em sobre-exploração (44%), bem como o acréscimo potencial de outras ameaças ao recurso solo, como o perigo de incêndio, devido ao aumento de áreas combustíveis sujeitas a controle social escasso – os matos – a merecer especial atenção por parte dos decisores e atores regionais.info:eu-repo/semantics/publishedVersio

Short-term effects of olive-pomace-based conditioners on soil aggregation stability

Mediterranean agriculture asks for sustainable strategies to prevent actual soil organic matter decline rates. Composting agri-food by-products for application in farmland, besides contributing to a circular economy at regional or local scales, may improve soil resistance to physical degradation. Aggregate stability (AS) is a crucial property for building up such resistance. Olive pomace is an abundant by-product of the olive oil industry that may be valorized through composting. This study aimed to assess the influence on AS of olive-pomace-based composts (OPC) applied to a sandy loam Leptosol and a clay loam Fluvisol. To assess the effects of compost characteristics on AS, three OPCs resulting from different olive pomace proportions in the composting raw material (44, 31, and 25% by volume) were applied to aggregate samples in three doses (10, 20, and 40 t.ha−1, plus control) with fine and coarse grain sizes. Controlled laboratory conditions subjected samples to daily wetting-drying cycles during a 30-day experiment. AS was measured by wet sieving. OPC application significantly increased AS in the Leptosol amended with fine (+15% vs. control) and coarse (+19%) grain-size compost. In well-aggregated Fluvisol, amendment induced a significant increase in AS only in the compost coarse grain size (+12%). The application dose significantly affected AS, with 10 t.ha−1 being the best-performing dose. OPC applications in weakly aggregated soils are seemingly an encouraging soil management practice for improving soil resistance to physical degradation and reducing soil organic matter decline rates in Mediterranean farmland.The authors are grateful for the financial support of the research carried out by projects “BIOMA—Circular Economy and the digital transformation in Agrifood sector, POCI-01-0247-FEDER- 046112”, and “ForestWaterUp—Nature-based solutions for the ecological restoration of degraded soils in the Sabor Lakes, POCI-07-62G4-FEDER-181557”. The authors are also grateful to the Foundation for Science and Technology (FCT, Portugal) for the financial support through national funds FCT/MCTES (PIDDAC) to CIMO (UIDB/00690/2020 and UIDP/00690/2020) and SusTEC (LA/P/0007/2020). Ana Caroline Royer thanks the national funding by FCT, the Foundation for Science and Technology, through the individual research grant 2022.11024.BD.info:eu-repo/semantics/publishedVersio

Tendências de mudança na precipitação e na susceptibilidade à seca avaliada pelo Índice de Precipitação Normalizada (SPI) no nordeste de Portugal

Much of NE Portugal is an area of arid zones with moderate to severe susceptibility to desertification and drought. A single and coupled trend analysis of precipitation and SPI drought index was performed in six weather stations in NE Portugal (representative of the regional climate domains), over a seventy-year time series (1931-2000). Precipitation over the study period decreased at most stations, with a more pronounced trend in the wetter areas, whereas in the semiarid areas an increase in precipitation was found. As well as the frequency of months with severe and extreme drought, the frequency of dry and wet months increased when the SPI timescale increased (1 to 6 months) and when a more recent computation period is considered (1931-1960 to 1971-2000). The results highlight a tendency for precipitation extremes to occur in NE Portugal. The general development of trends in precipitation and drought reported in this study confirm a progressive severity in the susceptibility to desertification affecting NE PortugalAs zonas áridas ocupam boa parte do NE Portugal, região de moderada a severa suscetibilidade à desertificação e seca. A análise de tendência da precipitação, isolada e combinada, e do índice de seca SPI foi realizada em seis estações meteorológicas no NE Portugal (representativas dos climas regionais), no período 1931-2000. A precipitação diminuiu na maioria das estações, de modo mais pronunciado nas áreas mais húmidas, enquanto nas do semiárido se verificou um aumento na precipitação. Tal como no caso da frequência de meses com seca severa e extrema, a frequência de meses secos e húmidos aumentou com o aumento da escala de tempo do SPI (de 1 a 6 meses) e considerando o período de cálculo mais recente (de 1931-1960 a 1971-2000). Os resultados evidenciam uma tendência para o aumento da ocorrência de extremos de precipitação. Estas tendências de mudança na precipitação e seca confirmam um aumento da severidade na suscetibilidade à desertificação que afeta o NE Portugal.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020). This research was partially funded by the EU FEDER Fund, through the POCTEP programme funding the TERRAMATER (grant0701_ TERRAMATER_1_E) research project. Furthermore, Royer A.C.’s contribution to the research was partially financially supported by the Instituto Politécnico de Bragança through the Double Diploma MSc programme in Environmental Technology with the Technological Federal University of Paraná, Brazil.info:eu-repo/semantics/publishedVersio

Regression models for soil water storage estimation using the ESA CCI satellite soil moisture product: a case study in Northeast Portugal

The European Space Agency Climate Change Initiative Soil Moisture (ESA CCI SM) product provides soil moisture estimates from radar satellite data with a daily temporal resolution. Despite validation exercises with ground data that have been performed since the product’s launch, SM has not yet been consistently related to soil water storage, which is a key step for its application for prediction purposes. This study aimed to analyse the relationship between soil water storage (S), which was obtained from soil water balance computations with ground meteorological data, and soil moisture, which was obtained from radar data, as affected by soil water storage capacity (Smax). As a case study, a 14-year monthly series of soil water storage, produced via soil water balance computations using ground meteorological data from northeast Portugal and Smax from 25 mm to 150 mm, were matched with the corresponding monthly averaged SM product. Linear (I) and logistic (II) regression models relating S with SM were compared. Model performance (r2 in the 0.8–0.9 range) varied non-monotonically with Smax, with it being the highest at an Smax of 50 mm. The logistic model (II) performed better than the linear model (I) in the lower range of Smax. Improvements in model performance obtained with segregation of the data series in two subsets, representing soil water recharge and depletion phases throughout the year, outlined the hysteresis in the relationship between S and SM.This research was partially funded by the Foundation for Science and Technology (FCT, Lisbon, Portugal), grant number UIDB/00690/2020. Furthermore, A.C.R.’s contribution to the research was financially supported, first, by the Instituto Politécnico de Bragança through the Double Diploma MSc programme in Environmental Technology with the Technological Federal University of Paraná, Brazil, and second, by the EU FEDER Fund, through the POCTEP programme funding the TERRAMATER research project (grant 0701_TERRAMATER_1_E).info:eu-repo/semantics/publishedVersio