Semi-arid Mediterranean Region Research Articles

Sensitivity of extreme rainfall to temperature in semi-arid Mediterranean regions

Warmer air has the potential to hold more water vapour and, therefore, to provide more water to rainfall events. Studying the relationship between rainfall and temperature represents an emerging issue in hydrology and meteorology, since it can be considered fundamental for evaluating the effects of global warming on future precipitation. Various approaches have been tested across different parts of the world, in many cases observing an intensification of extreme precipitation at higher temperatures consistent with the well-known thermodynamic Clausius-Clapeyron relation (CC-scaling rate of 6–7%°C−1). However, at different locations for hourly time-scales, the temperature-extreme rainfall scaling can be higher (super-CC) or lower (sub-CC).This study contributes to the understanding of the scaling relationship between extreme rainfall and temperature under climate conditions characteristic of Mediterranean semi-arid regions, rarely explored in the past. The role of different factors, such as rainfall characteristics and climatic seasonality, modelling framework and rainfall accumulation period are investigated through an application to Sicily (Italy). In particular, the suitability of different types of regression models used to interpret the relationship between hourly and sub-hourly extreme rainfall and surface temperature is explored.We find overall a sub-CC scaling for most of the island of Sicily. However, the rainfall-temperature scaling relationship is not constant over the temperature range and may be dependent on the season. The different results obtained highlight the importance of modelling choices for analyses in regions characterized by semi-arid climates. More specifically, we observe increasing scaling rates for decreasing rainfall accumulation periods, and significant sensitivity of scaling rates to the selected extreme rainfall quantile. Our novel use of piecewise and locally-weighted scatter plot smoothing regression-based approaches allow the accurate characterization of the temperature dependence of extreme rainfall in Sicily. This identifies a peak-like structure for the drier season, not detected by the simple application of the commonly-used exponential regression based approach.

Comparison between geostatistical and machine learning models as predictors of topsoil organic carbon with a focus on local uncertainty estimation

In recent years, the environmental modeling community has moved away from kriging as the main mapping algorithm and embraced machine learning (ML) as the go-to method for spatial prediction. The drawback of this shift has been a gradual decline in the number of papers in which uncertainty is presented and mapped alongside estimates of the target variables because in some ML algorithms, computing the local uncertainty can be challenging. This drawback has been recently identified in the literature as one of the key areas in DSM where progress is most needed. The main objective of this work is to compare geostatistical techniques, ML methods and hybrid methods, e.g., regression kriging, in terms of not only their overall accuracy but also their precision in providing useful confidence intervals at unsampled locations. We aim to provide clear application guidelines for future mapping exercises.For this experiment, we used a legacy soil dataset (n = 414) of topsoil observations from the semi-arid Mediterranean region of Sicily. This dataset was collected in a 2008 survey with a pedo-landscape sampling design; hence, it is ideal for comparing geostatistics and ML. In the comparison, we included algorithms that have been widely adopted in the literature: ordinary and universal kriging, linear regression, random forest (RF), quantile regression forest, boosted regression trees (BRT) and hybrid forms of kriging (e.g., regression kriging with RF and BRT used as regressors).To evaluate the accuracy of each algorithm, a validation test that was based on the random exclusion of 25% of the samples was repeated 100 times. In addition, we performed a test of the transferability, in which the locations with the largest nearest-neighbor distances were excluded from training and re-predicted. The validation results demonstrate that ordinary and universal kriging are the best performers, followed closely by random forest (RF) and quantile regression forest (QRF). In terms of local uncertainty, RF and QRF provide confidence intervals that most often include the observed values of SOC. However, they both provide very wide confidence intervals, which may be problematic in some studies. Other algorithms, such as boosted regression trees and boosted regression kriging, performed slightly worse (on this dataset), but produced narrower ranges of uncertainty. Hence, they may be more attractive since their estimates are very robust against changes and noise in the predictors.

Early prediction of durum wheat yield in Spain using radial basis functions interpolation models based on agroclimatic data

Durum wheat is an important crop in semi-arid Mediterranean regions as Andalusia, an autonomous community in the southern part of Spain. Accurate early predictions of durum wheat yield can provide precious information for within-season adjustment of crop managing as well as for economical and political stakeholders. In this study, an alternative methodology to mechanistic crop models is proposed for within-season early prediction of durum wheat yield in Spain based on estimates for its larger producer community, Andalusia. The proposed Radial Basis Functions (RBF) interpolation models are based on the sown area and a large number of climatic variables. Global warming and increasing occurrence of extreme weather events are only two of the factors that make crop yield forecast extremely difficult as they can lead to an increased interannual yield variability. Nevertheless, the RBF models proposed presented good quality yield predictions clearly outperforming multivariate linear models used as benchmark. Moreover, RBF models’ predictions made four months prior to harvest are able to capture the trend of the yield series as well as near-harvest predictions.

Typological assessment of dairy farms systems in semi-arid Mediterranean region of Western Algeria

The present study aimed to characterize the dairy cattle farming systems in semi arid region in western Algeria. A typology of the farms was established following the description of livestock dairy farming practices and the assessment of their contribution to farm efficiency. The enquiry was conducted on 60 dairy farms during 2018-2019 agricultural campaign to determine structural, technical and economic parameters. The Results show a large diversity of farmer?s strategies, particularly in feeding and economic indicators. The statistical analysis has identified 3 groups of farms. The first group contains 12 farms produce average milk yield about 4120 kg and promote use of forages. The participation of concentrates in total dry matter ingestion (DMI) is about 45.3 %, the average costs of milk production is of 37.1 DA/ liter?0.52 ? and charge of food in total production costs in the order of 62.8 %. 32 dairy farms of second group are characterized by average milk yields 3240 kg and the contribution of concentrated foods represents 49.2 % of total DMI. The cost of liter of milk is about 42.7 DA?0.60 ? and food costs in order of 68.7 % of total production costs. The third group contains 16 dairy farms whose illustrates farms with a significant contribution of concentrates in the global feed balance (54.3 % of total DMI). These concentrated foods were poorly converted into milk as recorded yields are the lowest (2010 kg). Production costs of liter milk and the percentage price of food in total cost production were respectively highest (49.4 DA?0.69 ?) and (80.2 %). The results of this typology indicate the diversity of dairy farms systems in semi-arid region in North Africa, which must be taken to ensure the profitability and sustainability of farms identified. The socio-economic factors are behind the genesis of sample farms, the technical feeding and rationing and no diversification of forage calendar make clear the variations in groups of dairy husbandry. To guarantee sustainability development of typological groups, a specific measure, particularly in feeding management, will be applied for different livestock systems identified.

Influence of dry ambient conditions on performance of underground medium-voltage DC cables

In its publication IEC 60287, the International Electrotechnical Commission recommends procedures for thermal analysis of power cables in the presence of a dry-out zone in the surrounding medium. It is well known, that the ampacity of cables depends strongly on the so-called critical temperature at which the surrounding medium dries out. However, research on how to estimate this critical temperature has been limited. In semi-arid Mediterranean climate regions, dry summers typically lead to a decrease of the critical temperature. In this paper, the critical temperature is calculated for a field in Riverside, California under various ambient conditions. This is done from the numerical solution of the differential equation for moisture content in the planar case of steady-state coupled heat and mass transfer in porous media. Finite-difference simulations of a system of two medium-voltage DC cables in this field are performed with SHEMAT-Suite (Simulator of HEat and MAss Transport) to compute the maximum temperature for daily cases of calculated critical temperature and compared to a prediction from IEC 60287. It is found that large day-to-day variations in field conditions in a semi-arid area may significantly affect the maximum allowable current. Our results emphasize the importance of ambient conditions for the cable performance.

The Potential Relationship Between Archaeological Artifact Exposure and Surface Geomorphic Processes: Northeastern Peloponnese, Greece

ABSTRACTComplex interactions between topography, near-surface geology, active tectonics, climate, and human activity shape a landscape, conditioning archaeological deposits and making sediment deposits from surface erosion important archives. There is a potential relationship between the intensity of geomorphic processes and surface artifact distribution. This study assesses the potential relationship between soil erosion by water and the spatial distribution of archaeological surface artifacts in the Inachos River watershed, Greece. The mountainous, semi-arid Mediterranean region is particularly vulnerable to soil loss. Soil erosion is quantified by applying the Revised Universal Soil Loss Equation in a GIS framework. Estimates of soil loss vary spatially compared to surface artifact finds of the pedestrian survey of the Western Argolid Regional Project. A statistically significant relationship is identified between surface erosion rates and artifact density. Preferential topography for occupation suggests this is an associative rather than causative relationship. Knowledgeable interpretation of artifact distribution enables accurate reconstruction of human settlement history.

Effects of Metal Oxides and Urea Fertilizer on Agronomic Traits of Safflower

Abstract In Mediterranean semi-arid regions major constraints impinging on agricultural development are deficiency of water and nutrient depleted soils. The problem of enhancing crop yield in these areas is widely distinguished as a challenge. In order to evaluate the integrated application of urea fertilizer (0, 160, and 320 kg ha−1) and nano-metal oxide (Fe2O3, ZnO, and CuO) on safflower growth performance, a field experiment was carried out in the Baneh district, a semi-arid region in Western Iran. Urea fertilizer significantly increased the plant height (11%), canopy width (8%), ground cover percentage (6%), plant dry weight (35%), number of secondary branches (16%), seeds number per head (19%), and total seed yield (38%). However, the higher application of urea fertilizer resulted in a significant decrease in wrinkled seed percentage (3.25%), harvest index (2.62%), and thousand seed weight (2.67%). Also, nano-metal oxides significantly affected morphological traits and yield components. Mean comparison revealed that the best performance was obtained by the integrated application of 320 kg urea fertilizer and nano-Fe or nano-Zn. Overall, the present research highlighted the necessity of balanced and integrated application of macronutrients and micronutrient fertilizers for sustainable safflower production in semi-arid regions of Western Iran.

Impact of rainfall frequency and intensity on inter- and intra-annual satellite-derived EVI vegetation productivity of an Acacia caven shrubland community in Central Chile

Seasonal precipitation is critical for springtime plant activity, and a direct connection may exist between the rainfall frequency and intensity with vegetation productivity in dryland ecosystems. This connection has been poorly quantified in the semi-arid Mediterranean region of Chile. In this work, we describe the effects of the monthly frequency (λ) and intensity (α) of rainfall events on two satellite-derived Enhanced Vegetation Index (EVI) descriptors: the time-integrated vegetation index (mEVI), a surrogate for total potential productivity, and the maximum vegetation index (iEVI), a surrogate for maximum photosynthetic activity, in a shrubland ecosystem dominated by Acacia caven. Time series analyses over a period of 15 years (2000–2014) were carried out for assessing their relationships and lags. Rainfall descriptors largely explained the temporal variation in vegetation productivity. Values of mEVI and iEVI showed a short-term statistical dependence of up to 4 months with precipitation frequency, meaning that vegetation productivity was delayed compared to the occurrence of rain events. This delay might be related to soils acting as water reservoirs being used by different plant types at different times and soil depths, i.e., herbs using water from the upper soil horizons with small lags in relation to rain pulses, while shrubs drawing water from deeper in the soil would exhibit greater range of lags. The asynchrony between rainfall events and suitable environmental conditions for growth, and the ability of plants to draw water at different soil depths with different lags may be an ecological adaptation to the high inter- and intra-annual rainfall variability.

Deserts do not advance, they are created: Land degradation and desertification in semiarid environments in the Middle Atlas, Morocco

Semiarid Mediterranean regions are highly susceptible to desertification. This study investigated the influence of increasing anthropogenic pressure on land degradation in highly vulnerable semiarid environments in the Mediterranean region. Remote sensing imagery was used to identify changes in land cover between 1984 and 2007, which indicated a clear trend of land degradation, and that the most important features were the transformation of forest to shrubland, the conversion of shrubland to grassland, and, the degradation of grassland to bare land, the last stage of degradation. The largest amount of degraded land was in the administrative fraction that was characterized by high population and livestock numbers, as well as the large number of settlements on rangeland. Bayesian Model Averaging showed that the probability of land degradation was highest near settlements, water points, and in areas that had gentle slopes. Furthermore, landscape pattern analysis revealed a reduction in the area occupied by Genista pseudopilosa, and an increase in the fragmentation of patches of Artemisia herba alba. The land degradation, which was triggered by high livestock pressure, might be irreversible, and restoration to initial conditions impossible because of the level of degradation; essentially, in areas where the degradation has reached a very advanced stage.

Influence of Integrated Application of Nano-Chelated Trace Elements and Sulfur on Desi Chickpea in the Short-Season Mediterranean-Type Environment

AbstractChickpea is one of the most important legume crops in the Mediterranean semiarid regions. Soils of these regions generally have free CaCO3, high pH and low organic matter, which reduce the availability of micronutrients and cause their deficiencies. In order to study the effects of integrated application of different level of elemental sulfur (0, 15, 30 kg·ha−1) and nano-chelated micronutrients (Zn, Fe, Mn) on growth and agro-morphological traits of chickpea (Cicer arietinum L.), a field experiment was conducted in the semiarid regions of the northwestern part of Iran. Evaluation of morphological traits showed that application of high level of sulfur significantly improved plant height, the number of primary branches and canopy width compared to the control. The longest growth period was recorded for plants grown by application of high level of sulfur and nano-chelated Zn fertilizer. The obtained data revealed that application of nano-chelated Zn fertilizer resulted in a significant increase in seed number per plant and seed weight compared to other nano-micronutrient fertilizers. Overall, the best growth performance and the highest seed yield were obtained from the integrated application of Zn and high level of sulfur. The findings showed that soil micronutrient deficiencies are partly due to high alkalinity of the soil, and application of sulfur beyond 15 kg·ha−1 can be an effective method to increase the efficacy of nanofertilizers. Integrated application of micronutrient and sulfur should be considered as an efficient agronomic management option for chickpea production systems in semiarid region.

The Effect of Iron, Zinc and Organic Fertilizer on Yield of Chickpea (Cicer artietinum L.) in Mediterranean Climate

Chickpea is one the most important legume crops in Mediterranean semi-arid regions and its sustainable production strongly depends on the nutrient management and water availability. Soils of these regions generally have high pH, and low organic matter, which reduce the availability of micronutrients and led to multi-micronutrient deficiencies. For estimating the effect of integrated application of different levels of organic fertilizer (zero, 20 t ha-1, 40 t ha-1) and micronutrient fertilizers (Zn, Fe) on agronomic traits and yield components of chickpea, an experiment was carried out at the highland semi-arid regions in Piranshahr district (36° 40ʹ N, 45° 08ʹ E; 1840 m). Assessment of phenological development revealed that plants grown under control condition (no-organic and micronutrients fertilizer) had a significantly slower development. Assessment of agronomic characteristics showed that application of micronutrients fertilizer substantially increased plant height, first pod height, canopy width, number of the seed, seed weight, economic and biological yield compared to control condition. By increasing the application rate of organic fertilizer its positive effects became more impressive on growth and yield component. The best growth performance was recorded by integrated application of 40 t ha-1 organic fertilizer and micronutrients fertilizers. However, there was no significant difference between fertilizer of Fe and Zn. Overall, the results indicated that the studied site is facing with micronutrient deficiencies and application organic fertilizer can noticeably improve the efficiency of micronutrients fertilizer. A quick and supplementary approach is therefore required for remedy of both Zn and Fe deficiencies in the short term. The finding showed that a substantial yield improvement is possible by integrated application of organic and micronutrient fertilizer.

Growth of the halophyteAtriplex halimuson a green roof at the semi-arid Mediterranean region as affected by substrate type and irrigation regime

Aiming to exploit native, drought tolerant plants for use on green roofs at the semi-arid Mediterranean region, the effect of substrate type and irrigation frequency on growth of the halophyte Atriplex halimus was investigated on an extensive green roof in Athens, Greece. Rooted cuttings were planted in December 2012 in experimental modules with a green roof infrastructure on a fully exposed second-floor flat roof and were kept in culture until September 2014. Two types of substrate, 10 cm deep, were used, one with soil, i.e. grape marc compost:perlite:soil:pumice (3:3:2:2, v/v) and a lighter one, without soil, i.e. grape marc compost:perlite:pumice (3:3:4, v/v). Two irrigation frequencies were applied during the two dry periods, i.e. every 5 days (normal) and 9 days (sparse) in summer 2013 and every 4 days (normal) and 7 days (sparse) in summer 2014, when substrate moisture was 17-20% and 5-9% for normal and sparse, respectively. At the first growth period (2013) plant height was promoted by normal irrigation, while the above ground fresh and dry weight in October 2013 was promoted both by normal irrigation and soil amended substrate. At the end of the second growth period (2014), dry weight of the above ground part of the plant was higher under normal irrigation, while plant height was not affected by any of the main factors. No evidence of damage to the plant photosynthetic apparatus was recorded in any of the treatments, while stomatal resistance (Rleaf) was increased in plants under sparse irrigation indicating water limitation. Plants grew well and looked similar in all treatments. Thus A. halimus is suitable for use on extensive green roofs in areas with semi-arid Mediterranean climate, with soilless (light weight) substrate and sparse irrigation.

Effect of substrate type and irrigation frequency on growth ofPallenis maritimaon an urban extensive green roof at the semi-arid Mediterranean region

Effect of substrate type and irrigation frequency on growth of<i>Pallenis maritima</i>on an urban extensive green roof at the semi-arid Mediterranean region

Modelling surface geomorphic processes using the RUSLE and specific stream power in a GIS framework, NE Peloponnese, Greece

Mediterranean regions, with climate variability and long histories of human disturbance, are particularly vulnerable to soil erosion and sediment redistribution. This study examines surface soil stability and stream energy of the 243 km2 Inachos River watershed in the northeast Peloponnese, Greece. This mountainous, semi-arid Mediterranean region has an extensive history of human activity. Soil loss and stream energy are each quantified by applying the Revised Universal Soil Loss Equation (RUSLE) using the Unit Stream Power Erosion Deposition (USPED) method and the specific stream power approach to the main river channels. These models are used to indicate the spatial variability in geomorphic activity. Results show an average soil loss for the Inachos River catchment of 15.0 t ha−1 a−1, exceeding the rate of soil formation. Values range from nil in low gradient environments to 4287 t ha−1 a−1 in steep, mountainous regions. Gradient and rainfall erosivity are the primary factors. High specific stream power in the upper watershed exceeds 17,100 W m−2, resulting in the mobilization of sediment into channelized debris flows that transport sediment from the steep hillslopes. Episodic high-magnitude precipitation events promote the longitudinal connectivity of the catchment. The long occupation and agricultural history, extending as far back as Neolithic time, has accelerated downslope sediment transport.

Patterns of microbial food webs in Mediterranean shallow lakes with contrasting nutrient levels and predation pressures

To elucidate the specific and combined effects of bottom-up and top-down control on the microbial community in warm lakes, we sampled microbial community along with physical–chemical and biological variables and performed in situ food web experiments, in 14 Turkish shallow lakes with contrasting nutrient levels and predation pressures. Our field results revealed that differences in microbial communities correlated with differences in zooplankton community structure, temperature (increasing nutrient concentrations, change in zooplankton composition), nutrient concentrations (increasing bacteria and heterotrophic nanoflagellate abundances with increasing nitrogen concentrations and temperature) and macrophyte coverage (ciliates as potential consumers of bacteria and HNF was strongest in macrophyte-dominated lakes). Our in situ experimental study revealed that the zooplankton not only affect the biomass and composition of microbial communities but also alter the microbial structure and trophic relationships. Our results therefore indicate that both bottom-up factors and top-down effects were important for the efficiency of the carbon transfer from bacteria to higher trophic levels in the study lakes. Due to an anticipated increase in eutrophication, temperature and alteration of the classical food web with climate warming, major changes in the microbial community of lakes are, therefore, expected in a warmer future in semi-arid Mediterranean climatic regions.

Modelling the Hydro‐Sedimentary Dynamics of a Mediterranean Semiarid Ungauged Watershed Beyond the Instrumental Period

AbstractThe development of reliable tools to quantify long‐term sediment budgets is critical to establish adequate environmental and management policies in semiarid Mediterranean regions. In this study, we apply a multidisciplinary methodology to estimate water and sediment yields in ungauged Mediterranean watersheds over a period of scarce instrumental data (i.e. second half of 19th and first half of 20th centuries). Runoff and precipitation reconstructions have been obtained using an integrative approach involving synoptic reanalysis models, regional climatic datasets, historical archives and palaeoflood proxies from natural archives. The resulting hydrological reconstruction has been implemented on a hydro‐sedimentary distributed model (i.e. TETIS) to understand the hydro‐sedimentary dynamics in the studied watershed. We highlight that, in our study area, regional‐data (instrumental, historical and sedimentary) based models show higher accuracy in the sediment yield and runoff reconstruction than synoptic reanalysis climate models. The modelled sedimentary dynamics for the studied period respond to a complex interplay between human activities and climate variability. During the 19th century deforestation and grazing activities combined with higher frequency on extreme runoff events resulted in higher runoff and sediment yield in the period 1863–1900. Over the 20th century, reduced precipitation and land abandonment led to a decrease in erosion rates and sediment yield although increased in 1945–1960 coinciding with a period of higher frequency of heavy rainfalls. This hydrological response to climate and human activities in the study watershed improves our understanding of plausible future trends of environmental degradation in small Mediterranean watersheds under different land use and climate change scenarios.This article includes supporting information which features an explanation of GILMCLIM downscaling model, The precipitation series resulting from the reanalysis data (Figure S1), an analysis of the different precipitation series used (Table S1) and an extensive explanation of how the relation between Puentes and Valdeinfierno reservoirs was considered. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Impacts of future climate scenarios on hypersaline habitats and their conservation interest

This study is focused on determining the response behaviour of five saline plant communities to two environmental variables: flooding and salinity. Also, total soil organic carbon, diversity, plant cover and vegetation height were measured. Once this behaviour is known, the impacts of future climate scenarios may be approached. Since some of these variables could be altered by climate change, the future vegetation dynamics might indicate the trending of change, so plant communities can be used as bioindicators. The investigation was carried out in some small coastal wetlands located in a semiarid Mediterranean region. Low values of diversity were found in these plant communities due to a great effect of flooding, followed by salinity. ‘Reed beds’ are bioindicators of flooding and environmental disturbance. ‘Saline rushes’ are also flooding bioindicators and efficient accumulators of organic matter. ‘Mediterranean halophilous scrubs’ are bioindicators of seasonal flooding and changes to salinity. ‘Mediterranean halo-nitrophilous scrubs’ might be considered as bioindicators of low flooding and low salinity in anthropic environment while ‘Mediterranean salt steppes’ bioindicate driest conditions. At present, Mediterranean halophilous scrubs are the most widely extended community, which could be interpreted as a consequence of a changing and sharply seasonal climate. Our research suggests that future climate change scenarios involving flooding increases would support the proliferation of the lowest diversity and thus lower ecological value plant communities (i.e. reed beds). Conversely, a future scenario of decreasing flooding would benefit the most diverse and valuable conservation community actually priortized by European Habitats Directive (Mediterranean salt steppes, Limonietalia).

Spatio-temporal topsoil organic carbon mapping of a semi-arid Mediterranean region: The role of land use, soil texture, topographic indices and the influence of remote sensing data to modelling

SOC is the most important indicator of soil fertility and monitoring its space-time changes is a prerequisite to establish strategies to reduce soil loss and preserve its quality. Here we modelled the topsoil (0–0.3m) SOC concentration of the cultivated area of Sicily in 1993 and 2008. Sicily is an extremely variable region with a high number of ecosystems, soils, and microclimates. We studied the role of time and land use in the modelling of SOC, and assessed the role of remote sensing (RS) covariates in the boosted regression trees modelling. The models obtained showed a high pseudo-R2 (0.63–0.69) and low uncertainty (s.d.<0.76gCkg−1 with RS, and <1.25gCkg−1 without RS). These outputs allowed depicting a time variation of SOC at 1arcsec. SOC estimation strongly depended on the soil texture, land use, rainfall and topographic indices related to erosion and deposition. RS indices captured one fifth of the total variance explained, slightly changed the ranking of variance explained by the non-RS predictors, and reduced the variability of the model replicates. During the study period, SOC decreased in the areas with relatively high initial SOC, and increased in the area with high temperature and low rainfall, dominated by arables. This was likely due to the compulsory application of some Good Agricultural and Environmental practices. These results confirm that the importance of texture and land use in short-term SOC variation is comparable to climate. The present results call for agronomic and policy intervention at the district level to maintain fertility and yield potential. In addition, the present results suggest that the application of RS covariates enhanced the modelling performance.

Allometric relationships for estimating vegetative and reproductive biomass in grapevine (Vitis viniferaL.)

Background and Aims Vineyards, one of the most widespread agricultural systems, have significant but scarcely evaluated carbon sequestration potential. Allometry is a cost-effective approach to estimate plant biomass, but few studies – focused mainly on permanent structure carbon fixation – have dealt with it in grapevine. This study develops allometric models that accurately estimate grapevine standing biomass (total vine biomass at harvest), using extensive field-collected data sets. Methods and Results Data were obtained in vineyards located in Spanish regions representative of the variability found in warm semi-arid Mediterranean regions. We developed and validated functions to estimate vine biomass for all vine organs. The models obtained estimated accurately the biomass fixed by each organ separately and even more accurately at the whole plant scale. To illustrate the potential of the models, they satisfactorily assessed the influence of seasonal vine water status on vine biomass production and partitioning using an independent data set. Conclusions and Significance of the Study The models constitute a powerful tool to determine in a non-destructive and cost-effective manner standing biomass from simple vine measurements, which makes them suitable for quantifying carbon stocks and allocation patterns, and for evaluating the influence of climate or cultural practices at large scale to estimate better – at a regional or international level – the contribution of grapevine culture to CO2 balances.

Evaposublimation from the snow in the Mediterranean mountains of Sierra Nevada (Spain)

Abstract. In this study we quantify the evaposublimation and the energy balance of the seasonal snowpack in the Mediterranean semiarid region of Sierra Nevada, Spain (37° N). In these kinds of regions, the incidence of this return of water to the atmosphere is particularly important to the hydrology and water availability. The analysis of the evaposublimation from snow allows us to deduct the losses of water expected in the short and medium term and is critical for the efficient planning of this basic and scarce resource. To achieve this, we performed 10 field campaigns from 2009 to 2015, during which detailed measurements of mass fluxes of a controlled volume of snow were recorded using a modified version of an evaporation pan with lysimeter. Meteorological data at the site of the snow control volume were extensively monitored during the tests. With these data, a point energy balance snowmelt model was validated for the area. This model, fed with the complete meteorological data set available at the Refugio Poqueira Station (2500 m a.s.l.), let us estimate that evaposublimation losses for this site can range from 24 to 33 % of total annual ablation. This ratio is very variable throughout the year and between years, depending on the particular occurrence of snowfall and mild weather events, which is generally quite erratic in this semiarid region. Evaposublimation proceeds at maximum rates of up to 0.49 mm h−1, an order of magnitude less than maximum melt rates. However, evaposublimation occurs during 60 % of the time that snow lies, while snowmelt only takes up 10 % of this time. Hence, both processes remain close in magnitude on the annual scale.