Sub-humid Climatic Conditions Research Articles

Shallow soils in dryland ecosystems: Drivers of C accumulation and land management implications

Shallow soils (i.e., Lithic Entisols) cover about 20% of Brazilian drylands. Inherent soil characteristics (i.e., shallow depths) and water scarcity restrict plant growth and carbon (C) inputs in these soils. In such a sensitive ecosystem, sustainable land management options are key to promoting socio-economic development and ensuring food security. Here, we use a dataset of 50 Lithic Entisol profiles distributed within the Brazilian drylands (northeastern region) to: (i) investigate the effects of land-use (cropland, grassland, and native forest), climate (semi-arid and dry sub-humid), and slope classes (0–3%, 3–8%, 8–20% and 20–45%) on soil C accumulation; and (ii) evaluate how understanding multiple drivers C accumulation can support the identification of sustainable land management options. The results suggested that land use does not affect C stock and C/N ratio, nevertheless, they were affected by climate. Under dry sub-humid climate conditions, C stocks were 41.7 Mg ha−1, 44% higher than under semi-arid climate (28.9 Mg ha−1), a result that reflects the effect of higher biomass production in wetter environments. Under slopes of 20–45%, C stocks were 54.3 Mg ha−1, 172% higher than under slopes of 0–3% (19.9 Mg ha−1), because of the higher altitudes and wetter conditions under steeper slopes. Our results showed that areas under lower slopes have lower C stocks and lower aridity index. These drier conditions reduce the productive potential of annual crops and grasslands but enable the cultivation of high-yielding Crassulacean Acid Metabolism (CAM) crops, such as Agave spp, which have a high potential for biofuel production. Furthermore, the possibility of reintroducing organic residues from ethanol production can promote an increase in C stocks, contributing to climate change mitigation. Ultimately, our study provides insights from a holistic view of SOC accumulation drivers, supporting land use planning of highly sensitive environments in tropical drylands around the world.

Strategies to Improve Quality of Fibrous Feeds: Evaluating the potential of Cow Pea (Vigna Unguiculata) accessions grown under sub-humid climatic conditions of Western Ethiopia

Five selected cowpea accessions (ILRI 9325, ILRI 11976, ILRI 6782, ILRI 6783 and WWT) were evaluated for herbage dry matter (DMY) and crude protein (CPY) yields, and nutritive value. Among the tested accessions, ILRI 9325, ILRI 6782, ILRI 6783 and WWT gave higher and comparable yields (P<0.01 for DMY; P=0.05 for CPY), with ILRI 9325 giving superior yields. The overall CP content was 17% with a range of 16% for WWT to 18% for ILRI 9325. The overall mean for neutral detergent fiber (NDF), acid detergent fiber (ADF) and lignin were 43%, 34% and 6%, respectively. The in vitro organic digestibility (IVOMD) ranged from 64% (ILRI 6783) to 69% (WWT). The relative feed value (RFV) index averaged 135 (range = 128 – 142). The mean metabolizable energy (ME) content was 10 MJ/kg DM with a range of 9.5 to 10.4. Three accessions that combined high biomass DM and crude protein yields, and herbage quality were: ILRI 9325, ILRI 11976 and WWT. The two former accessions can thus be promoted to the next variety verification stage alongside with WWT as a check to identify one or two alternative cowpea varieties for official release.

Feasibility of the adaptive thermal comfort model under warm sub-humid climate conditions: Cooling energy savings in Campeche, Mexico

The conventional approach to achieve thermal comfort generally focuses on modifying the setpoint temperature in fully air-conditioned buildings. However, the adaptive thermal comfort approach is an alternative that considers the interaction between buildings, the local climate, and the users to allow significant improvements in energy savings. This paper analyzes the feasibility of implementing adaptive thermal comfort strategies, comparing adaptive models based on the ASHRAE 55-2020 Standard and a regional model for the tropical climate typology of Mexico, and contrasting the results with the static approach. Thirteen locations in the State of Campeche were thermally analyzed, seeing that the ventilation strategies are applicable throughout the State and that both models ensure improvements in energy consumption. In addition, the results suggest that it is necessary to develop more local adaptive models to propose strategies with better potential impact in the region.

High-resolution record of stable isotopes in soil carbonates reveals environmental dynamics in an arid region (central Iran) during the last 32 ka

Although central Iran is pivotal for palaeoclimatic correlations, palaeoenvironmental data for this region is very sparse and a reliable chronology for pedogenic features is lacking. We therefore tried to answer the question how the environmental conditions and, in particular, the climate developed over time by using the isotopic signatures of pedogenic carbonates. We present a chronology of pedogenic carbonates in association with stable carbon and oxygen isotopes in both the matrix and coating carbonates of a relict palаeosol (Baharan palaeosol) in central Iran to understand the dynamics of environmental changes in this region during the late Quaternary. The palаeosol experienced several episodes of leaching during pedogenesis as reflected in its morphology (carbonate coatings under the rock fractions) and geochemical characteristics (Ba/Sr ratios). The δ18O values of both the matrix and coating carbonates in the upper 60 cm (especially in the upper 20 cm) of the pedon are enriched (∼4‰) compared to the subsoil and are mainly related to the impact of evaporation. Moreover, the δ13C values of the carbonates are in isotopic disequilibrium with the modern vegetation cover (desert shrubs) of the study area and are enriched in different degrees. The carbonates in the top 60 cm are formed by the input of atmospheric CO2 and calcareous dust while deeper carbonates formed in an environment exhibiting a higher contribution of C4 plants. Based on the radiocarbon chronology of carbonate coatings, it seems that three main stages of palaeoenvironmental changes occurred in the region during the last 32 ka. The first stage lasted ca. 5,000 years (between 31.6 and 26.0 ka) and was accompanied by deep leaching under sub-humid climatic conditions and the expansion of C4 plants. Under the dominance of semi-arid conditions during the second stage until the late Holocene, a gradual increase in the δ18O values and aridity occurred in the region. The last phase in the late Holocene was characterised by the establishment of an arid and evaporative environment with a sparse vegetation cover. A climatic correlation using the oxygen isotopic composition of secondary carbonates from the Baharan palaeosol, Soreq Cave (the Levant) and Hoti Cave (Oman; both having speleothems records) suggested a climatic connection between central Iran and the eastern Mediterranean during the late Pleistocene and between central Iran and northern Oman during the late Holocene.

Microbial consortia enhance the yield of maize under sub-humid rainfed production system of India

Plant beneficial microorganisms are being used to improve soil health and crop yield in different cropping systems. Maize is an important crop grown around the world for food, feed and raw material for various industries. The aim of the present study was to evaluate two microbial consortia viz., microbial consortia 1 (Pseudomonas putida P7 + Paenibacillus favisporus B30) and microbial consortia 2 (Pseudomonas putida P45 + Bacillus amyloliquefaciens B17) under field conditions for their suitability in improving maize yield under rainfed situations at Ballowal Saunkhri (Punjab) having sub-humid (Hot Dry) climatic conditions. Pooled analysis of three years field experiments data showed that, seed + soil application of microbial consortia 1 and 2 led to enhancement in grain yield of kharif maize by 27.78 and 23.21% respectively over uninoculated control. Likewise, significant increase in Benefit:Cost ratio as well as straw yield was also observed. The present investigation suggests that, microbial consortia would help in significantly improving the yield and economics of maize grown on inceptisols under rainfed conditions.

Simplified Penman-Monteith Equation Determined by Temperature-Based Global Radiation Data and Its Multilocal Validation under Subhumid Climatic Conditions in Hungary

Simplified Penman-Monteith Equation Determined by Temperature-Based Global Radiation Data and Its Multilocal Validation under Subhumid Climatic Conditions in Hungary

The Integrated Approach for Organic and Inorganic Sources of Nutrients to Enhance Performance of Cauliflower (Brassica oleracea var. botrytis L.) under Sub-Humid Climatic Conditions

To overcome the limitations of soil fertility and provide high crop output, soil fertility management, including the sensible use of mixes of organic and inorganic fertilizers, is a realistic approach. The strategy of integrated nutrient usage was used since there was a decrease in soil characteristics and crop productivity as a result of the overuse of chemical fertilizers. The present study was designed in 2019–2020 and 2020–2021 at the high-tech unit, Department of Horticulture, Udaipur to investigate the integrated use of FYM and inorganic fertilizers along with silicon on the development and output parameters of cauliflower (Brassica oleracea var. botrytis L.). The field experiment was carried out with fourteen treatments as a soil application under randomized block design. The results revealed that treatment T14 (50% recommended dose of nitrogen by FYM + 50% recommended dose of fertilizers + 100 kg Silicon/ha) showed maximum plant height at harvest (65.73 cm), number of leaves per plant (24.27), leaf area index (11.83), chlorophyll content at 50 days after transplanting (1.99 mg/g), stalk length (8.23 cm) and stem girth (7.41 cm), minimum number of days to curd initiation after transplanting (66.37), minimum number of days required for marketable curd maturity after transplanting (89.17), maximum plant weight (1154.74 g), diameter of curd (15.75 cm), curd yield (277.53 q/ha) and dry weight of curd (91.41 g) as compared to control. In the end, the results showed that the growth and yield of cauliflower were better when silicon, manure, and chemical fertilizers were used together.

Polyphenolic Compound Variation in Globe Artichoke Cultivars as Affected by Fertilization and Biostimulants Application.

Globe artichoke is an ancient herbaceous plant native to the Mediterranean Basin. The edible part of the plant is limited to the fleshy leaves (bracts) and receptacle of a large immature inflorescence (head) that has been shown to be a rich source of bioactive compounds. Nutritional and pharmacological properties of artichoke heads and leaves are attributed mainly to polyphenolic compounds and inulin present at high concentration. In this study, polyphenols were investigated in two artichoke cultivars (Opal and Madrigal) in response to four nitrogen rates and foliar applications of biostimulating products under drip irrigation. Field experiments were carried out over two growing seasons (2015–2016, 2016–2017) in Policoro (MT), Southern Italy, on a deep clay soil in sub-humid climate conditions. Phenolic compounds were isolated and characterized by means of high-performance liquid chromatography with photodiode array detection and electrospray ionization/mass spectrometry (HPLC-DAD-MS/MS) analysis. In both cultivars, caffeoylquinic acids were more abundant when a dose of 100 kg ha−1 of ammonium nitrate was provided, whereas apigenins were not affected by nitrogen fertilization. Luteolins increased in cv Opal and decreased in cv Madrigal following N fertilization. The application of biostimulants (3 L ha−1) favored the accumulation of polyphenols, in particular of caffeoylquinic acids and apigenin, in artichoke heads in both cultivars. The results obtained highlight some positive aspects related to the synergistic effect of nitrogen fertilization and biostimulant foliar application.

Chlorophyll Response to Water Stress and the Potential of Using Crop Water Stress Index in Sugar Beet Farming.

Field experiments were conducted in 2019 and 2021 growing seasons to evaluate the chlorophyll readings and crop water stress index (CWSI) response to full and deficit irrigation for drip-irrigated sugar beet (Beta vulgaris L.) under sub-humid climate of Bursa, Turkey. In addition, the changes of soil water content under different irrigation treatments and statistical relationships between chlorophyll and CWSI values and ETc, root yield and sugar yield were investigated. Experiments were carried out in a completely randomized blocks design with three replications. Irrigations were scheduled based on the replenishment of 100 (S1), 66 (S2), 33 (S3), and 0% (S4) of soil water depletion within the soil profile of 0–90 cm using 7 day irrigation intervals. Lower and upper baselines obtained by measurements based on the canopy temperature from the treatments full irrigated and non-irrigated were used to calculate CWSI. The variations in CWSI values were consistent with the variations of seasonal soil water contents induced by the different irrigation practices. CWSI values generally varied between 0 and 1 throughout the experimental periods. In 2019, seasonal mean chlorophyll readings varied between 203.3 and 249.1, and mean CWSI values varied between 0.12 and 0.85. In 2021, seasonal mean chlorophyll readings varied between 232.7 and 259.3 and mean CWSI values between 0.19 and 0.89. Unlike chlorophyll values, CWSI decreased with increased irrigation water amount. In both years, statistically significant relationships were determined between chlorophyll readings and CWSI and ETc, root yield and sugar yield. The greatest root yield was achieved with a seasonal mean CWSI value of 0.12. An exponential equation determined as “Root Yield = 10.804e−1,55CWSI” between seasonal average CWSI values and root yield can be used for estimation of root yield in sugar beet farming. The mean CWSI values determined by infrared thermometer technique can be used in determination of crop water stress and irrigation scheduling of sugar beet cultivation under sub-humid climatic conditions.

Climate, sea-level and anthropogenic processes controlling the environmental evolution of shallow lakes in the southeastern Pampa plain (South East South America) during the last 12 ka

The evolution of both Lake Hinojales-San Leoncio (37°23′S; 57°23′W) and Tobares (37°30′S; 57°28′W) was reconstructed using pollen, non-pollen palynomorphs, plant macrofossil remains and associated fauna, diatoms and mollusks. This is the first paleolimnological reconstruction covering the hydroclimatic variability over the last 12 ka for the southeastern Pampa plain. At the onset of the Holocene (12-11 ka), shallow clear brackish-to-hypersaline water bodies subject to episodic expansion/retraction cycles developed in the area under wet climatic conditions. During the Early Holocene, unstable environments were inferred due to intercalated episodes of total desiccation, associated with a drop in rainfall that promoted drier conditions than those previously inferred. The Middle Holocene (only represented in Lake Hinojales-San Leoncio) was characterized by the development of a brackish-saline lake with a deeper water column, under drier climatic conditions than those recorded previously. The temporal persistence of this saline paleolake might have been influenced by the marine transgressive-regressive cycle dated between 6000 and ca. 2000 yr BP in the coastal area close to the lake. From nearly 2500 to ca. 600 cal yr BP there was a gradual change from brackish to freshwater-brackish water conditions, as a consequence of a regional increase in rainfall together with the decrease in sea level that promoted the establishment of modern humid to sub-humid climatic conditions prevailing today in the Pampa plain. The last 35 cal yr BP represented the onset of modern eutrophic conditions within the lake, which are concomitant with the agriculture intensification in the region. The regional changes in the different biological proxies analyzed here, support the hypothesis of a predominance of external climatic triggers over intrinsic limnological processes as main causes of paleoenvironmental changes modulating the evolution of lakes. The main environmental forces affecting these lakes seem to be indirectly related to precipitation during the Early Holocene, sea level changes during the Middle Holocene and the recent (Anthropocene) human impacts related to the intensification of farming activities.

Evaluation of Climatic and Tectonic Imprints In Fluvial Successions of An Early Permian Depositional System (Asselian VrchlabÍ Formation, Krkonoše Piedmont Basin, Czech Republic)

ABSTRACT The Krkonoše Piedmont Basin, an early post-Variscan basin (c. 310–280 Ma) located in the NE Bohemian Massif (Czech Republic, central Europe), contains up to 300-m-thick non-marine Lower Permian (Asselian) deposits of the Vrchlabí Formation that crop out in its western part. The Early Permian Krkonoše Piedmont Basin exhibits striking similarities—in terms of tectonostratigraphic evolution, depositional patterns, and volcanism—to other early post-Variscan, near-equatorial intermontane basins. This work focuses on sedimentological analysis of the Vrchlabí Formation using outcrop data, combined with borehole and newly acquired field gamma spectrometry data. The formation consists predominantly of fluvial deposits in the southern part of the basin that pass laterally into deltaic and lacustrine deposits of the Rudník Member, located in the central part of the basin. Fluvial deposits are formed by sandstone and conglomeratic bodies, decimeters to several meters thick, interpreted as single-story and multi-story channel fills as well as various macroforms (e.g., bars) deposited by a low-sinuosity fluvial system. Channel fills intercalate with floodplain deposits centimeters to few meters thick. Vertically, the studied fluvial succession is divided into five intervals based on i) variable preservation ratio between channel fill and floodplain deposits and ii) external and internal geometries of sandstone and conglomerate channel bodies. In order to explain the observed vertical changes in fluvial style and to determine the main controlling factors, the interaction of the fluvial system with the contemporaneous lake was investigated by interpreting base-level changes of the fluvial system and their correlation with lake level changes. In the central part of the basin the transition from fluvio-deltaic to lacustrine deposits is represented by alternating beige to gray sandstones centimeters to few meters thick and by dark gray mudstones up to several meters thick that pass northwards into shales. At the outcrop scale, the new sedimentological data in combination with newly acquired gamma-ray logs enabled tracing the lateral extent of individual fluvial bodies. The integration of the new data with older borehole data leads to a substantially better understanding of lateral and vertical relationship between the fluvio-deltaic and the lacustrine facies at the basin scale. Tectonic subsidence played a substantial role during the initial deposition of the Vrchlabí Formation. However, the external geometries, the internal architecture of fluvial channel bodies, and the variable degree of floodplain preservation throughout the entire Vrchlabí Formation cannot be explained by tectonics only, but requires the consideration of climatic controls. The Early Permian fluvial system is interpreted to reflect seasonal discharge variability with dry and wet periods under long-term subhumid climatic conditions that shifted towards more arid conditions during the latest depositional stage of the Vrchlabí Formation.

Effect of Accelerant Additives in Concrete with Limestone Aggregate in Warm Weather

Additives are chemical compounds that are added to concrete during its manufacture to modify one or more of its properties. The first additive used in modern concrete was the accelerator, intended to shorten the time during which the material is not capable of supporting stress. Traditionally, accelerators have been made from calcium chloride, but today the trend is to use chloride-free additives to prevent reinforcing steel from corroding and thereby make constructions durable. The objective of this study was to evaluate the effects on the concrete of two types of accelerating admixture, using limestone aggregates, under warm sub-humid climate conditions. The applied methodology consisted of the measurement in the laboratory of some of the main properties of concrete in fresh and hardened states, in samples manufactured both with and without accelerators. The results showed that the accelerator without chloride was less effective than the one based on calcium chloride and that without doses of the accelerator, the effectiveness documented by the manufacturers was achieved.

Developing new hyperspectral vegetation indexes sensitive to yield and evapotranspiration of dry beans

Dry bean (phaseolus vulgaris L.) field experiment was carried out under the subhumid climatic conditions of Bafra, Turkey, to evaluate the possibilities of using hyperspectral reflectance data for estimating yield and water consumption. Three irrigation management treatments that depend on monitoring soil water content and one rain-fed treatment were subjected to dry beans arranged in a randomized complete block design with three replications. In addition to soil water measurements, hyperspectral reflectance observations were made throughout the dry beans? growing season. Actual crop evapotranspiration values were calculated by using a detailed soil water balance approach. After smoothing the hyperspectral reflectance data, the first and second derivatives of spectra were calculated. Statistical analysis methods were applied to determine the most sensitive wavelengths to dry bean yield and evapotranspiration (ETa) for developing new spectral indexes based on measured spectral data. Furthermore, some of the well know spectral vegetation indexes were calculated. Statistical comparison between spectral indexes and yield showed that the difference of the second derivative of spectra in 749 and 697 nm could be a good indicator (r = 0.998 and RMSE = 0.027) for estimating dry bean grain yield. Similarly, the difference of the second derivative of spectra in 1003 and 717 nm gave the most significant statistical comparison result (r = 1.0 and RMSE = 3.0) for ETa.

Effects of Seeding Rate and Sowing Date on Herbage Dry Matter and Seed Yield Performance of Brachiaria Grass Grown under Subhumid Climatic Conditions of Western Oromia, Ethiopia

The experiment was conducted at Bako Agricultural Research Center (BARC) for three years (2013, 2014 and 2015) to compare the effect of sowing dates and seeding rates on productivity of Brachiaria decumbens. The treatments consisted of four sowing dates (1 week, 3 weeks, 5 weeks and 7 weeks) after onset of main rain and four levels of seeding rates (6, 8, 10 and 12) kg ha -1 . Accordingly, sowing dates started on May 28, 2013 and thereafter at 14-days intervals: June 11, 2013; June 25, 2013 and July 09, 2013. An experimental design of a randomized complete block in factorial arrangement with three replications was used. The analysis of variance indicated that seeding rate by planting time interaction effect was highly significant (p<0.01) for herbage DM yield and seed yield. However, none significant differences were observed for plant height, plot cover and vigorousity. The highest herbage dry matter yield and seed yield (18.67 ton ha -1 ) and (6.37 Qt ha -1 ), respectively were obtained from seeding rate of 6 kg ha -1 that planted at three weeks after the commencement of main rainy season. Year have also significant (p<0.01) effect on both herbage dry matter and seed yields. Maximum herbage dry matter yield (22 ton ha -1 ) and seed yield (9.76 qt ha -1 ) were obtained during the first year (2013) in the second sowing time (June 11, 2013) at 6 kg ha -1 seeding rate. Therefore, it can be recommended that the lower seed rate (6kg ha -1 ) sown at 3 weeks after commencement of the main rain was produced better herbage DM (18.7 ton ha -1 ) and seed yields (6.37 qt ha -1 ) and was favorable for Bako area and similar agro ecologies. Keywords : Dry matter, herbage yield, sowing time, seed rate DOI: 10.7176/JAAS/70-01 Publication date: January 31 st 2021

Geochemical and Petrological Studies of Permo-Carboniferous Sandstones from the Rangit Pebble-Slate Formation, Sikkim Lesser Himalaya, India: Implication for Provenance, Tectonic Setting, and Paleoclimate

The Permo-Carboniferous depositional sequence of Lower Gondwana in Sikkim Lesser Himalaya was investigated through an integrated approach of lithological, petrological, and geochemical studies. Lithologically, it is characterized by glacial diamictite at the base and shale-sandstone facies at the top of a sequence which is interpreted as a glaciomarine deposit. Coarser sandstone and massive diamictite composed of quartz, feldspar, muscovite, zircon, and other lithic fragments are observed in thin section. Geochemistry of all studied samples from the Rangit Pebble Slate Formation shows the dominance of silicon dioxide compared to other elemental oxides. The tectonic discrimination diagram positively infers passive margin sedimentation from a felsic-rich provenance. Chemical Index of Alteration was used to depict the weathering trends of all studied samples which reflect paleo-sedimentation under humid to sub-humid climatic conditions.

Neoarthropitys gondwanaensis gen. nov. et sp. nov. from the Middle Triassic of Gondwana: an intermediate stage in the anatomical trend of Equisetalean stems

A new petrified stem from the Middle Triassic Quebrada de los Fósiles Formation (Puesto Viejo Group, San Rafael Basin) in Mendoza Province, central-western Argentina, is described. The specimen shows affinities with fossil and extant Sphenophyta, such as the presence of a medullar cavity and primary xylem with carinal canal. A new genus and species – Neoarthropitys gondwanaensis – is established based on the presence of a secondary xylem with interfascicular rays and fascicular wedges, and the development of a mesarch–endarch primary xylem. These anatomical features allow differentiating it from all previously known Equisetales taxa, showing an intermediate stage between Calamitaceae which is characterized by mesarch primary xylem and by presence of the secondary xylem, and the Equisetaceae having endarch primary xylem and lacking of secondary xylem. The presence of a mesarch–endarch primary xylem in the Triassic Argentinian specimen has phylogenetic value, appearing as an intermediate stage in the anatomical trends of Equisetales stems. Neoarthropitys gondwanaensis gen. nov. et sp. nov. has a set of equisetalean features not present in any other clade, supporting the idea that they were part of a distinct group. The presence of transfusion tracheid piths supports previous hypothesis that the plants recorded in the Quebrada de los Fósiles Formation grew in an ecologically disturbed environment by intermittent volcanic ash falls, in the floodplains of a high-sinuosity fluvial system under seasonally sub-humid climatic conditions.

Pedogenic and subaerial exposure microfabrics in a late Carboniferous-early Permian carbonate-volcanic lacustrine-palustrine system (San Ignacio Formation, Frontal Cordillera, Argentina)

In the Argentinian Andes (Frontal Cordillera) the upper part of the late Carboniferous-early Permian San Ignacio Formation is made up of lacustrine-palustrine microbial carbonates and interbedded volcanic deposits. In this lacustrine-palustrine environment a natural monospecific forest was developed. The deposits of this sedimentary-volcanic succession were repeatedly subjected to subaerial exposure and modified by pedogenesis to varying degrees giving rise to paleosoils development. Diagenetic microfabrics were well preserved in the carbonates and volcanic rocks. The carbonate microfabrics comprise a wide spectrum of features consisting of root marks and stumps-related structures (rhizoliths, alveolar texture, tunnel-like structures and coprolites of arthropods), pisoids, coated grains and pseudomicrokarst, cracking, brecciated and nodular fabrics, and grainification also occur corresponding to different stages in the pedogenic evolution. Meteoric dissolution and cementation processes are observed; examples are well identified by scanning electron microscope showing silica-filled voids in partially dissolved carbonates and growths of inorganic carbonate microcrystals or of microbial origin in voids. Other different types of cements can be seen such as discontinuous carbonate crusts, ribbon spar, cavities with silt infillings and pendant cements. The whole set of these microfabrics are indicative of wetting, desiccation and meteoric conditions (vadose and phreatic). The abundance of plant roots and associated micro-organisms mainly of bacterial origin (micro-rods, short rod-shapes, nano-fibres, filaments and nano-spheres) played an important role in the pedogenic and subaerial diagenetic processes affecting these deposits. The immature character of the paleosoils and absence of calcretes point out to short intervals of subaerial exposure due to oscillating fluctuations in water level, intermittent volcanic supply, tectonic subsidence and oscillating climatic conditions. The whole of the macro and microfabrics reveals that the prevailing weather could correspond to an intermediate between semi-arid to sub-humid, however the alternating wetting and drying conditions in which the fossil forest developed and the abundance and diversity of micro-organisms, suggest a transition to sub-humid climate conditions.

Validation of RUSLE K factor using aggregate stability in contrasted mediterranean eco-geomorphological landscapes (southern Spain)

Mediterranean mountains are facing great environmental and socioeconomic challenges in the current framework of Global Change. One of these is soil degradation, which is one of the major threats in those territories. Soil degradation is more dramatic where eco-geomorphology and land uses with less vegetation cover promote soil erosion. Soil erosion is influenced by soil erodibility, which can be assessed by different methodologies, e.g. RUSLE K factor and aggregate stability of soils. This study deals with the validation of RUSLE K factor by means of soil aggregate stability analysed in two-contrasted watersheds from one Mediterranean mountainous region in South of Spain, under sub-humid and semiarid climatic conditions. In both of them, landscape dynamic from 1956 to 2016 was analysed in order to characterize the modifications in land uses. A total of 361-soil samples was also taken covering all land uses for analysing aggregate stability of soils as well as those soil properties needed to calculate the RUSLE K factor. The results indicated that: i) landscape dynamic was influenced by changes in land uses contributing mainly to an increment in vegetation cover in the rainiest watershed; ii) the analysed soil properties showed very few significant differences between watersheds and between land uses, especially regarding organic matter content; and iii) the validation of K Factor using aggregate stability was better in the rainiest watershed and, within this one, in the natural land uses and irrigated cultivations, meaning where the biotic factors were more influential. These results implicated more researches are necessary, principally, focussed on the validation of the RUSLE K parameter using different fractions of aggregates as well as considering other eco-geomorphological parameters.

Nitrate transport in a karst aquifer: Numerical model development and source evaluation

Protecting karst aquifers from nitrate contamination is an issue of global concern due to the inherent vulnerability of karst aquifers to contamination and the negative health effects of elevated nitrate levels. Hydrological and transport models were developed to assess nitrate transport within a karstic aquifer located in an area with both semi-arid and sub-humid climate conditions. Groundwater flow through the aquifer matrix and conduits was simulated with CFPv2, an experimental version of the Conduit Flow Process (CFP) version of the MODular FLOW (MODFLOW) groundwater model. Nitrate transport was simulated with the experimental Conduit Mass Transport Three-Dimensional Model (CMT3D). The hydrologic calibration of the steady-state model was successful based on a scaled Root Mean Squared Error (RMSE) of 4.9% for hydraulic heads and percent errors of 3.0% and 6.6% for the two major springs in the area. Performance of the transient hydrologic model exceeded the performance of the existing Equivalent Porous Media (EPM) model with a scaled RMSE of 2.2% and springflow errors of 1.5% and 2.8% for the major springs. Similarly, nitrate calibration was successful with all Percent Bias (PBIAS) values between ±25%. Additional calibration statistics including a two-tailed t-test indicated successful calibration. The CMT3D model corroborates prior research findings that anthropogenic sources as well as biogenic wastes are important sources of nitrate to the aquifer. The methodology used in this study represents an additional tool for watershed managers to address nitrate contamination within karst aquifers.

Effect of Growth Stage Moisture Stress on Common Bean (Phaseolus Vulgaris L.) Yield and Water Productivity at Jimma, Ethiopia

Water stress is a major crop production constraint for common bean (Phaseolus vulgaris L.). This study investigated the response of common bean (Phaseolus vulgaris L.) to moisture stress at different growth stages for yield and water productivity under sub-humid climate conditions over a three-year period. A field experiment was conducted at Jimma Agricultural Research. A randomized complete block design with three replications was used. fifteen treatments which combined and imposed at four growth stages were used. The combined result indicated that there were a significant variation among treatments for yield, above ground dry biomass and water productivity. The yield of common bean was significantly affected due to moisture stress imposed at different growth stages.