This study details the physiological responses of cork oak (Quercus suber L.) to manipulated water inputs. Treatments named as dry, ambient and wet, which received 80, 100 and 120% of the annual precipitation, respectively, were applied to a Mediterranean woodland in southern Portugal. Tree ecophysiology and growth were monitored from 2003 to 2005.
The impacts of the water manipulation were primarily observed in tree transpiration, especially during summer drought. Rainfall exclusion reduced the annual stand canopy transpiration by 10% over the 2-year study period, while irrigation increased it by 11%. The accumulated tree transpiration matched precipitation in spring 2004 and 2005 at the stand level, suggesting that cork oak trees rely on precipitation water sources during the peak of the growing season. However, during the summer droughts, groundwater was the main water source for trees.
Despite the significant differences in soil water content and tree transpiration, no treatment effects could be detected in leaf water potential and leaf gas exchange, except for a single event after spring irrigations in the very dry year 2005. These irrigations were intentionally delayed to reduce dry spell duration during the peak of tree growing season. They resulted in an acute positive physiological response of trees from the wet treatment one week after the last irrigation event leading to a 32% raise of stem diameter increment the following months. Our results suggest that in a semi-arid environment precipitation changes in spring (amount and timing) have a stronger impact on cork oak physiology and growth than an overall change in the total annual precipitation. The extreme drought of 2005 had a negative impact on tree growth. The annual increment of tree trunk diameter in the ambient and dry treatments was reduced, while it increased for trees from the wet treatment. Water shortage also significantly reduced leaf area. The latter dropped by 10.4% in response to the extreme drought of 2005 in trees from the ambient treatment. The reduction was less pronounced in trees of the wet treatment (−7.6%), and more pronounced in trees of the dry treatment (−14.7%).
Cork oak showed high resiliency to inter-annual precipitation variability. The annual accumulated tree transpiration, the minimum midday leaf water potential and the absolute amount of groundwater used by trees appeared unaffected by the extreme drought of 2005. Our study shows that cork oak rapidly and completely recovered from the extreme dry year of 2005 or from rainfall exclusion. Our results support the eco-hydrological equilibrium theory by which plant acquire complementary protective mechanisms to buffer the large variability in water availability experienced in semi-arid ecosystems. In optimizing their structural biomass increase in response to increasing drought stress, cork oak trees succeeded in restricting water losses to maintain the minimum leaf water potential above the critical threshold of xylem embolism, though with narrower hydraulic safety margins in 2005.
Our findings highlight cork oak's sensitivity to the amount and timing of late spring precipitation. This could be critical as future climate scenarios predict a reduction of spring precipitation as well as enhanced severity of droughts in the Iberian Peninsula by the end of the 21st century. In inducing water stress before the onset of summer droughts, the predicted spring precipitation decline could drive the species closer to the threshold of catastrophic xylem embolism at the peak of the drought period.
Western Iberia has recently shown increasing frequency of drought conditions coupled with heatwave events, leading to exacerbated limiting climatic conditions for plant growth. It is not clear to what extent wood growth and density of agroforestry species have suffered from such changes or recent extreme climate events. To address this question, tree-ring width and density chronologies were built for a Pinus pinaster stand in southern Portugal and correlated with climate variables, including the minimum, mean and maximum temperatures and the number of cold days.
Monthly and maximum daily precipitations were also analyzed as well as dry spells. The drought effect was assessed using the standardized precipitation-evapotranspiration (SPEI) multi-scalar drought index, between 1 to 24-months. The climate-growth/density relationships were evaluated for the period 1958-2011. We show that both wood radial growth and density highly benefit from the strong decay of cold days and the increase of minimum temperature. Yet the benefits are hindered by long-term water deficit, which results in different levels of impact on wood radial growth and density. Despite of the intensification of long-term water deficit, tree-ring width appears to benefit from the minimum temperature increase, whereas the effects of long-term droughts significantly prevail on tree-ring density.
Our results further highlight the dependency of the species on deep water sources after the juvenile stage. The impact of climate changes on long-term droughts and their repercussion on the shallow groundwater table and P. pinaster’s vulnerability are also discussed. This work provides relevant information for forest management in the semi-arid area of the Alentejo region of Portugal. It should ease the elaboration of mitigation strategies to assure P. pinaster’s production capacity and quality in response to more arid conditions in the near future in the region.
Regional climate models provided precipitation and temperature time series for control (1961-1990) and scenario (2071-2100) periods. At southern Portugal, the climate models in the control period systematically present higher temperatures and lower precipitation than the observations. Therefore, the direct input of climate model data into hydrological models might result in more severe scenarios for future water availability. Three bias correction methods (Delta Change, Direct Forcing and Hybrid) are analysed and their performances in water availability impact studies are assessed.
The Delta Change method assumes that the observed series variability is maintained in the scenario period and is corrected by the evolution predicted by the climate models. The Direct Forcing method maintains the scenario series variability, which is corrected by the bias found in the control period, and the Hybrid method maintains the control model series variability, which is corrected by the bias found in the control period and by the evolution predicted by the climate models.
To assess the climate impacts in the water resources expected for the scenario period, a physically based spatially distributed hydrological model, SHETRAN, is used for runoff projections in a southern Portugal basin. The annual and seasonal runoff shows a runoff decrease in the scenario period, increasing the water shortage that is already experienced. The overall annual reduction varies between -80% and -35%. In general, the results show that the runoff reductions obtained with climate models corrected with the Delta Change method are highest but with a narrow range that varies between -80% and -52%.
This study evaluates climate change potential impacts on irrigated agriculture in the Guadiana river basin, in the south of Portugal, by running long-term soil water balance simulations using the ISAREG model and taking into consideration the maximum potential yield. The ISAREG simulations were focused in a set of the most locally representative crops to assess the evolution of net and total water requirements, considering a monthly time step for two 30-year future periods,(2011–2040) and (2041–2070).
Reference evapotranspiration was estimated using the temperature-based Hargreaves–Samani equation, and the simulations were performed using, as inputs, a combination of five climate change scenarios built using the Ensemble-Delta technique fromCMIP3 climateprojectionsdatasets to setdifferent alternative climate change bracketing conditions for rainfall and air temperature.Water balance outputs for different climate scenarios were combined with four agricultural scenarios allowing for the estimation of total irrigation requirements.
A general increase in crop irrigation requirements was estimated, mainly for those crops as maize, pasture, and orchards that are already big irrigation water consumers. Crops as olive groves and vineyards, well adapted to the Mediterranean conditions, show less sensitivity to climate change. The combined results of crop irrigation requirements for climate change and agricultural scenarios allow for the expectation of sustainability for the agricultural scenarios A and C, essentially defined by the complete use of the irrigation network and systems currently being constructed with the Alqueva project, but not for the ambitious irrigation area expanding scenario B.
Respiration traits allow calculating temperature-dependent carbon use efficiency and prediction of growth rates.
This protocol aims
(1) to enable validation of respiration traits as non-DNA biomarkers for breeding on robust plants in support of sustainable and healthy plant production;
(2) to provide an efficient, novel way to identify and predict functionality of DNA-based markers (genes, polymorphisms, edited genes, transgenes, genomes, and hologenomes), and
(3) to directly help farmers select robust material appropriate for a specified region.
The protocol is based on applying isothermal calorespirometry and consists of four steps: plant tissue preparation, calorespirometry measurements, data processing, and final validation through massive field-based data.The methodology can serve selection and improvement for a wide range of crops. Several of them are currently being tested in the author's lab. Among them are important cereals, such as wheat, barley, and rye, and diverse vegetables. However, it is critical that the protocol for measuring respiration traits be well adjusted to the plant species by considering deep knowledge on the specific physiology and functional cell biology behind the final target trait for production.
Here, Daucus carota L. is chosen as an advanced example to demonstrate critical species-specific steps for protocol development. Carrot is an important global vegetable that is grown worldwide and in all climate regions (moderate, subtropical, and tropical). Recently, this species is also used in my lab as a model for studies on alternative oxidase (AOX) gene diversity and evolutionary dynamics in interaction with endophytes.
Reservoirs often play an important role in mitigating water supply problems. However, the implications of climate change are not always considered in reservoir planning and management. This study aimed to address this challenge in the Alto Sabor watershed, northeast Portugal.
The study analysed whether or not the shortage of water supply can be effectively addressed through the construction of a new reservoir (two-reservoir system) by considering future climate projections. The hydrological model Soil and Water Assessment Tool (SWAT) was calibrated and validated against daily-observed discharge and reservoir volume, with a good agreement between model predictions and observations.
Outputs from four General Circulation Models (GCM) for two scenarios (RCP 4.5 and 8.5) were statistically downscaled and bias-corrected with ground observations. A general increase in temperature is expected in the future while the change in precipitation is more uncertain as per the differences among climatic models. In general, annual precipitation would slightly decrease while seasonal changes would be more significant, with more precipitation in winter and much less in spring and summer. SWAT simulations suggest that the existence of two-reservoir will better solve the water supply problems under current climate conditions compared to a single-reservoir system.
However in the future, the reliability of this solution will decrease, especially due to the variability of projections from the different climatic models. The solution to water supply problems in this region, adopted taking only present-day climate into account, will likely be inefficient for water supply management under future climate conditions.
A fenotipagem de alto débito permite identificar parâmetros funcionais diretamente relacionados com o comportamento varietal em condições de stress climático. É uma ferramenta importante no moderno melhoramento de plantas uma vez que permite complementar os critérios habitualmente utilizados, aumentando a eficiência de seleção.
Agriculture is strongly dependent on weather conditions and climate change can alter precipitation patterns leading to extreme events as droughts and floods. Irrigated crops, such as rice, could be affected by water shortage due to prolonged drought periods or even floods.
In Portugal, important paddy fields are located in Sado and Tejo river basins. Analysis of precipitation in meteorological stations from 1931/32 to 2016/17 in Sado basin and 1909/10 to 2016/17 in Tejo basin show similar variations. From record’s beginning until 1949/50 a dryer season was observed, followed by a wet season from 1950/51 until 1994/95. An instable and drier season was observed from 1995/96 onwards, with a decrease in the precipitation pattern in parallel with a great oscillation compared with the trendline.
Conversely, in wet periods the precipitation pattern is more alike with smaller variations in what regards the trendline. Thus, farmers are forced to select, the more drought resistant crops in order to face the insecurity of dryer periods. No extrapolations can be derived from yield and precipitation data within a short-time period of 11 and 10 years as seen in the Sado and Tejo basins. The increase in precipitation does not always means higher yields, since other interacting factors might influence productivity.
Here we develop a framework to design multi-species monitoring networks using species distribution models and conservation planning tools to optimize the location of monitoring stations to detect potential range shifts driven by climate change. For this study, we focused on seven bat species in Northern Portugal (Western Europe). Maximum entropy modelling was used to predict the likely occurrence of those species under present and future climatic conditions. By comparing present and future predicted distributions, we identified areas where each species is likely to gain, lose or maintain suitable climatic space.
We then used a decision support tool (the Marxan software) to design three optimized monitoring networks considering: a) changes in species likely occurrence, b) species conservation status, and c) level of volunteer commitment. For present climatic conditions, species distribution models revealed that areas suitable for most species occur in the north-eastern part of the region. However, areas predicted to become climatically suitable in the future shifted towards west. The three simulated monitoring networks, adaptable for an unpredictable volunteer commitment, included 28, 54 and 110 sampling locations respectively, distributed across the study area and covering the potential full range of conditions where species range shifts may occur.
Our results show that our framework outperforms the traditional approach that only considers current species ranges, in allocating monitoring stations distributed across different categories of predicted shifts in species distributions. This study presents a straightforward framework to design monitoring schemes aimed specifically at testing hypotheses about where and when species ranges may shift with climatic changes, while also ensuring surveillance of general population trends.
Agroforestry systems and tree cover on agricultural land make an important contribution to climate change mitigation, but are not systematically accounted for in either global carbon budgets or national carbon accounting. This paper assesses the role of trees on agricultural land and their significance for carbon sequestration at a global level, along with recent change trends.
Remote sensing data show that in 2010, 43% of all agricultural land globally had at least 10% tree cover and that this has increased by 2% over the previous ten years. Combining geographically and bioclimatically stratified Intergovernmental Panel on Climate Change (IPCC) Tier 1 default estimates of carbon storage with this tree cover analysis, we estimated 45.3 PgC on agricultural land globally, with trees contributing >75%.
Between 2000 and 2010 tree cover increased by 3.7%, resulting in an increase of >2 PgC (or 4.6%) of biomass carbon. On average, globally, biomass carbon increased from 20.4 to 21.4 tC ha−1. Regional and country-level variation in stocks and trends were mapped and tabulated globally, and for all countries. Brazil, Indonesia, China and India had the largest increases in biomass carbon stored on agricultural land, while Argentina, Myanmar, and Sierra Leone had the largest decreases.