Pampean Region Research Articles

A Maxent Predictive Model for Hunter-Gatherer Sites in the Southern Pampas, Argentina

The following paper presents the results of a Species Distribution Model (SDM) for grassland hunter-gatherer archaeology sites in the southern Pampas region of Argentina. The goal of this exploratory model is to provide a complementary survey model for the detection of archaeological sites in this region, which will also help characterize and discuss site locations and regional distribution patterns of hunter-gatherer occupations. Even in this largely homogenous and highly dynamic landscape, SDMs can help guide archaeological surveys by identifying some environmental variables affecting hunter-gatherer decisions, and can provide insights into mobility and archaeological settlement patterns. Among the available tools for SDM, Maximum Entropy Modeling (Maxent) is one of the most widely used approaches in archaeological predictive modelling. After controlling for bias and adjustment of several modifiable parameters, the Maxent software provided a potentially effective predictive model to direct future archaeological survey and heritage management projects. The results of this research suggest that watercourses and slope were the key environmental factors influencing the distribution of hunter-gatherer archaeological sites in the southern Pampas region.

Pores size distribution and pores volume density of Mollisols and Vertisols under different cropping intensity managements with no-tillage

In the Argentina Pampas, one of the most extensive agricultural areas in the temperate fringe of southern hemisphere, soil health is jeopardized mostly by the decline of physical and biological properties due to soil fragility and agricultural managements, even under No-tillage (NT). In this study, topsoil physical health of three Mollisols and one Vertisol under two agricultural managements with no-tillage (good and poor agricultural practices -GAP and PAP-, differing mostly in their cropping intensity -CI-) was evaluated by the indirect measurement of porosity features. Two types of pore features derived from soil water release curves (SWRC) of undisturbed samples at three depths (0.0–0.05, 0.05–0.010 and 0.010–0.20 m) were employed: a) pores size distribution (>1000, 300, 50 and < 50 µm) and b) pore volume density parameters: location (Dmode, Dmean and Dmedian) and shape (SD, Skewness and Kurtosis). Pore parameters were related to management variables, to clay mineralogy and to several soil physical and chemical properties allowing to i) evaluate the effects of cropping intensification on soil physical properties; ii) evaluate the effects of intrinsic and dynamics factors on the behaviour of pore variable; iii) build an optimal pore size frequency curve to assess soil health. Among all porosity features assessed, PMac>300 µm and Dmode showed close relationships with agricultural management variables and were positively related to a labile organic carbon fraction (POCc) and to the aggregates stability tests, regardless of the soil type. Thus, they both may be selected as sound indicators of physical health status of different pampean soils under NT cultivation. Particularly, in the PAP treatments and for the three depths evaluated, PMac>300 µm showed values below critical thresholds, highlighting the physical deterioration of soils subjected to this management. Cropping intensification expressed by the CI index was also strongly related with large pores and soil properties (i.e. organic carbon and aggregates stability). These results demonstrate that cropping intensification expressed by the CI index was effective to counteract compaction processes in a variety of soils of the Pampa region and must be seen as an important strategy to avoid porosity loss and to improve the benefits of NT.

Comparative Dynamics of Nutrient Release through Litter Decomposition in Eucalyptus grandis Hill ex Maiden and Pinus taeda L. Stands

The installation of commercial stands with exotic forest species on low fertility soils originally covered by native pastures is an unusual situation worldwide. In recent years, the area occupied by forest systems designed for pulp or wood production with immediate replanting has increased strongly in the Pampean region of South America. In this context, the study of nutrient recycling from forest litter decomposition acquires particular relevance. This work seeks to evaluate and compare the nutrient release from the decomposition of forest litter produced by 14-year-old Eucalyptus grandis Hill ex Maiden and Pinus taeda L. stands and test the applicability of a new sampling methodology in the nutrient recycling assessment. For two years, the evaluation of N, P, K, Ca, Mg, Fe, Mn, Cu and Zn dynamics during litter decomposition was carried out. In general, K concentration decreased through decomposition, meanwhile, all other nutrients showed some degree of immobilization, but this was counteracted by biomass loss for most of them. This mainly resulted in net nutrient release from litter. A higher release rate of all nutrients from P. taeda forest litter compared to E. grandis, with the exception of Mn, was verified. Fe immobilization was observed in both species showing a higher immobilization rate in E. grandis compared to P. taeda. Finally, Zn exhibited immobilization processes in E. grandis and releases in P. taeda. This might suggest higher temporal and quantitative availability of nutrients in P. taeda, due their faster return to the soil. These findings could be relevant in the development of models for sustainable management, adapting the demand for nutrients to the supply during forest rotations.

Evaluation of aquifer recharge into Salto Chico, Hernandarias and Ubajay formations. Palmar Creek, Entre Ríos, Argentina

The study of recharge mechanisms and volumes in aquifers is one of the most important issues for achieving sustainable exploitation of the groundwater resource. This factor has an impact on agricultural productivity as irrigation increases the yields of many crops and agriculture is the main economic activity in Argentina. However, recharge studies are not common in the country and this is why this paper is a new contribution. We have carried out a detailed study of the soil and hydrogeology in a hydrological basin. This basin is in an agricultural area typical of the Pampean region. Detailed records of precipitation, soil moisture and hydraulic head have been collected from stations designed for this purpose. We have also analyzed the influence and magnitude of vertical recharge from a water balance in the unsaturated zone. The calculation of the net recharge has also been included in the saturated zone. We have shown that the geological conditions of the basin influence the aquifer recharge. In outcrop zone of F. Ubajay the infiltration of surpluses allows a vertical transit equivalent to 6.61% with net recharge values of 1.41% of precipitation. In the outcrop zone of F. Hernandarias the conditions do not favour the infiltration of water surpluses and only allow a transit equivalent to 0.89% with a net recharge of 0.04% of precipitation. This scenario suggests that vertical recharge is not a dominant or quantitatively important process, which is atypical in Argentina’s Pampean region. These values are far from those previously established which varied between 7% and 15% of the average annual rainfall. The implications for water management in the region are significant and make it necessary to rethink the conceptual model of the aquifers in the area

Modelling water productivity for ecological intensification of crop sequences in the Inner Argentinean Pampas

• We evaluated water productivity (WP) and glucose yield of crop sequences. • Crop sequences were characterized with indexes of Ecological Intensification (EI). • WP was more related to water capture (C w ) than to water use efficiency (WUE). • WP, C w and WUE were associated with EI indexes. • The impact of VPD on WUE was as important as rainfall and its distribution pattern. The design of crop sequences based on ecological intensification (EI) may help to restore lost agroecosystem services and to increase resource use efficiency. Our aim was to evaluate, using a modelling approach, the impact of EI-based strategies, such as changing crop sequence configuration and increasing cropping intensity and agrobiodiversity, in the Inner Argentinean Pampas (IAP) region on water productivity (WP) of crop sequences and its components, i.e. water capture (C w ) and water use efficiency (WUE). We simulated crop sequences using SWB crop model for a 50-year period in two locations of IAP region. Crop sequences, of two-year duration each, had different configurations and included sole and/or double-crops in the growing season. These crop sequences were characterized using the following indexes of EI: cropping intensity index (CII), agrobiodiversity index (ABDI), cereal proportion (CP), maize ( Zea mays L.) proportion (MP) and soybean ( Glycine max [L] Merrill) proportion (SP). Our main findings reveal that: i) Regardless of location, all crop sequences alternatives to those based on a high SP had a higher estimated glucose yield, ii) Estimated glucose yield, WP, C w , and WUE were significantly related to one or more indexes of EI included in multiple lineal models, iii) The role of C w was more important than that of WUE to increase WP, iv) The choice of crop sequence was more critical to increase C w when decreasing rainfall, v) vapour pressure deficit appears as a meteorological variable at least as important as the total amount of rainfall and its distribution pattern to design crop sequences in the IAP. Thus, the used modelling approach allowed us to evaluate crop sequences spanning a wide range of ecological intensification indexes, which take into account the level of agrobiodiversity, cropping intensity, and the proportion of key crops in their composition, gaining useful insights to design sustainable cropping systems.

Kernel filling and desiccation in temperate maize: Breeding and environmental effects

Sowing date (SD) modifies the environmental conditions during the kernel-filling period as well as during kernel dry down after physiological maturity (PM), particularly for late-sown maize (Zea mays L.) crops that currently cover 50 % of the maize area in Argentina. The main goal of this work was to evaluate breeding effects on kernel filling and kernel desiccation traits in a set of five commercial maize hybrids released by a single breeding program between 1980 and 2016 when grown under contrasting environments in the temperate Central Pampas region. The evolution of kernel weight (KW) and kernel moisture (KM) were assessed. Maximum KW (KWMAX), maximum kernel water content (KWCMAX), kernel filling rate (KFR), kernel filling duration (KFD) and KM at silking+20 days (KMR1+20) and PM (KMPM) were computed together with husks number. Pre-PM kernel desiccation was described using an exponential decay model with k1 as the proportionality drying coefficient. For the post-PM period, kernel desiccation was modelled assuming that the change in KM in a given period is proportional to the difference between the kernel and the equilibrium moisture contents, where k2 was the corresponding proportionality drying coefficient. For KWMAX, a genetic progress of 0.26 % year −1 (p < 0.05) was estimated from 1993 to 2016. This trend was explained by the increase registered in KFD (0.32 % year−1, p < 0.01), which was partially compensated by a reduction in KFR (−0.08 % year−1, p < 0.05). No genetic progress was detected for husks number, KWCMAX, KMR1+20, KMPM, k1 and k2, but introduction of dent germplasm produced an increase in KWCMAX, KMR1+20 and KMPM and a decrease in k2. KFR and KFD as well as kernel desiccation dynamics were strongly affected by SDs. Breeding effects that extended KFD, together with the broad adoption of late sowings, promote a reduction in k2, which must be considered for the correct assessment of trade-offs between drying costs and kernel quality penalization by pests and diseases.

Logistical mobility in the eastern Tandilia mountain range (Argentina): Technological analysis for mid-Holocene hunter-gatherer occupations

This work analyze the technological management of raw materials and the mobility strategy of the human groups that occupied during the mid-Holocene (ca. 8000-3000 BP) the eastern Tandilia mountain range, and discuss them inside of settlement systems context for the southeastern Pampean region. The lithic study results of 13 occupations excavated in caves and rockshelters shows that mobility strategies in Tandilia mountain ranges were closer to collector models, where logistical groups moved into mountain range valleys in search of natural resources. We can recognize different strategies for raw material procurement: the immediately available rocks were obtained through direct access on daily foraging trips; the regional rocks were obtained through logistical displacements, residential movements and embedded strategies; and the access to the long distance rocks was through exchange between neighboring populations. Besides, during ca. 7000 to 5000 cal BP an increased use of immediately available raw materials and a high archaeological signal was detected. This scenario can be linked with an increased environmental aridity episode where human groups occupied with most intensity the Tandilia mountain valleys due to the greater availability of the water resources. Finally, this work provides new data suggesting that during this period in the southeastern Pampean region context, the hunter-gatherer groups combined forager and collector strategies to take advantage of the natural resources of the landscape with diverse environments (coastline, grassland plains, dunes field and mountain ranges).

Quantifying soil organic carbon’s critical role in cereal productivity losses under annualized crop rotations

Understanding the impact of soil degradation on crop productivity is essential for decision-makers to predict agronomic, economic, and environmental outcomes of agricultural operations. Soil organic carbon (SOC) is influenced by the cropping system and affects soil health through its effect on other soil physical, chemical, and biological properties. Data from a 56-year long-term experiment in Uruguay’s Pampa region were analyzed to quantify the effects of soil degradation on wheat (Triticum aestivum L.), and barley (Hordeum vulgare) yields. A significant degree of soil degradation was generated by six rotations with variable annual crop and pasture proportions (0%, 33%, 50%, and 66% of non harvest pasture). Yield records (n = 368) and annual values of 14 explanatory variables containing soil, climatic, and management indicators were evaluated using random forest regressions. Rotation-induced SOC variation ranged from 1.2% to 2.6%, and robust relationships between SOC, soil physical, chemical, and biological properties were established. Over time, yields increased in crop pasture systems but plateaued for the annualized crop rotation (0% pasture). Yield improvements due to agronomic technology advances partly mask soil degradation effects. SOC losses lead to a reduction in yield, even when the SOC level was above 2%. Thus, no critical level of SOC could be determined. SOC interacted with climate indicators to impact yield. This analysis confirms the central role of SOC in yield outcomes beyond nutrient availability, and its potential to represent a wide range of soil functions. Our findings indicate that crop rotations with a higher percentage annual vs. perennial crops negatively impact SOC, associated soil properties, and yield potential.

Redefining the Distributional Boundaries and Phylogenetic Relationships for Ctenomids From Central Argentina.

With about 68 recognized living species, subterranean rodents of the genus Ctenomys are found in a multiplicity of habitats, from the dunes of the Atlantic coast to the Andes Mountains, including environments ranging from humid steppes of Pampas to the dry deserts of Chaco region. However, this genus needs an exhaustive reevaluation of its systematic and phylogenetic relationships regarding the different groups that compose it. This knowledge is essential to propose biodiversity conservation strategies both at species level and at higher hierarchical levels. In order to clarify the taxonomy and the recent evolutionary history from populations of Ctenomys in the Pampas region, Argentina, phylogenetic relationships among them were evaluated using mitochondrial DNA sequences: gene encoding cytochrome b protein (1,140 bp) and the non-coding D-loop region (434 bp). To infer the divergence times inside the Ctenomys clade, a Bayesian calibrate tree using fossil remains data from different families within Caviomorpha was performed at first. Secondly, that calibration data was used as priors in a new Bayesian phylogenetic inference within the genus Ctenomys. This phylogenetic tree emphasized on species currently distributed on the Pampas region, more precisely considering both the talarum and mendocinus groups. Bayesian inferences (BI) were integrated with the results of a Maximum Likelihood approach (ML). Based on these results, the distributional limits of the mendocinus and talarum groups appear to be related to the physiognomy of the Pampas region soils. On the other hand, the validity of C. pundti complex as a differentiated species of C. talarum is debated. According to previous evidence from morphological and chromosomal studies, these results show a very low divergence between those species that originally were classified within the talarum group. Mitochondrial DNA sequences from populations associated with these putative species have not recovered as reciprocal monophyletic groups in the phylogenetic analyses. In conclusion, C. talarum and C. pundti complex might be considered as the same biological species, or lineages going through a recent or incipient differentiation process. The results obtained in this study have important implications for conservation policies and practices, since both species are currently categorized as Vulnerable and Endangered, respectively.

Precipitation estimations based on remote sensing compared with data from weather stations over agricultural region of Argentina pampas

Global patterns of precipitation have changed due to the increase in temperature as a result of climate change. Measuring the amount of precipitation at a given location using surface instruments is relatively simple. However, the great spatial and temporal variability of the intensity, type and occurrence of this phenomenon, makes direct and uniformly calibrated measurements difficult in large regions. Satellite information is an important alternative to describe precipitation events; the Global Precipitation Measurement (GPM) mission estimates precipitation, considering different time periods, with three products Integrated Multi-Satellite Retrievals for GPM (IMERG), in near real time. This study evaluates and quantifies, temporal and spatially, the monthly precipitation estimated by Early (IMERG-E), Late (IMERG-L) and Final (IMERG-F) products compared with data from weather stations located in agricultural areas of the Pampas region in Argentina. Data of precipitation belonging to meteorological stations located at four provinces: Buenos Aires, Córdoba, La Pampa and Santa Fe, for 2014–2018 periods, were considered. The spatial performance of IMERG was evaluated using statistical coefficients and Taylor diagrams, considering at region, province and stations level. The adjustment of the products increased from IMERG-E to IMERG–F, obtaining R2 values between 0.86 and 0.95 and RMSE from 14.2 to 29.3 mm, the best results corresponding to Córdoba and the worst to La Pampa. The performance of GPM products varies temporally; IMERG-F presented a higher correlation coefficient and a lower percent root mean square error in warm than in cold seasons. The results indicate that GPM can effectively capture the amount and patterns of monthly precipitation over the Pampas region of Argentina, which is important for its application to agricultural production and disaster prevention.

Surface water extent dynamics from three periods of continuous Landsat time series; subregional differences across Argentine plains

&lt;p&gt;The Pampean region in Argentina is an extensive plain characterized by abundant shallow lakes that fulfill many environmental, ecological, and social functions. This study aims to detect the multiannual lake area changes in this region during 2001-2009 using remote sensing, including lakes as small as ≥10,000 m&lt;sup&gt;2&lt;/sup&gt; or 1 ha. Landsat scenes of the wet (2008-2009), normal (2006), and dry (2008-2009) seasons were obtained, and using remote sensing techniques, the number and area of shallow lakes were calculated. The spatiotemporal variation of shallow lakes was studied in different climate periods in eight singular subregions. Spatial associations between annual precipitation and lake number and area were analyzed through the development of a Geographic Information System (GIS) at a subregional scale. During the study period the total lake area in the Pampean region decreased by 5257.39 km&lt;sup&gt;2 &lt;/sup&gt;(62 %), but each subregion showed different responses to climatic events. In seven of them, the differences between climate periods prove to be statistically significant (P&amp;gt;0.01). The relationship between precipitation and lake number and area revealed the domain of positive association. We conclude that climate factors play a dominant role in lake changes across the Pampean plains. However, other factors such as origin, topographic and edaphic characteristics intensify or mitigate changes in surface hydrology.&lt;/p&gt;

Aptitud para la implantación y supervivencia de gramíneas forrajeras estivales nativas y exóticas en la provincia de La Pampa, Argentina

Grasslands in arid and semiarid regions suffer ecological degradation and production limitations. A management alternative to reverse this situation is the sowing of mega­thermal forage species. The objective was to evaluate vegetative and reproductive characters for the establishment of native and introduced forage grasses of the semiarid pampean region. The species evaluated were: the native Leptochloa crinita and Pappophorum caespitosum and the introduced ones Eragrostis curvula, Eragrostis superba, Tetrachne dregei, Digitaria eriantha and Panicum coloratum. Survival (Ix), Canopy height (AM), Canopy diameter (DM), Number of tillers (NM), Length of floral stems (LVF), Number of floral stems (NVF), Number of seeds per plant (NSP) and Weight of thousand seeds (PMS) were determined. Survival, 3 months after implantation, was high and without significant differences between species. P. coloratum obtained the highest values regarding: NVF (3 and 12 months), LVF (12 months), DM (10 and 12 months) and PMS (4 and 14 months after its implantation). D. eriantha obtained the highest values in: LVF (3 months) and AM (3 and 12 months); while E. curvula in NM (10 and 12 months), T. dregei in NSP (14 months) and P. caespitosum in NSP (4 months after implantation) and had significant differences with the rest of the species. It is feasible to implant the evaluated species, because they show high survival, good propagation by tillering (introduced) and high seed production (native).

First-year cover crop effects on the physical and hydraulic properties of the surface layer in a loamy soil

Soil degradation is a global problem, threating its conservation and affecting agronomic production. No-tillage (NT) is the main management system for soil conservation world-wide. However, in Argentina, simplification of the crop sequence with high proportion of soybean under NT is a very common practice, leading to soil physical constrains. Crop sequence intensification through the inclusion of cover crops has been reported as an effective tool in the long-term for the enhancement of ecosystems services, improving NT performance. The objective of this work was to follow the evolution of the structural pore domain in the surface layer during the first year after the incorporation of cover crop (cover fallow of barley (Hordeum vulgare L.) and vetch (Vicia sp. L.), CF), as compared with bare fallow (BF), under NT management in a field experiment located in the Argentinean Depressed Pampas Region. Mini-infiltration and evaporation experiments were conducted in undisturbed soil samples (0−5 cm depth) in the laboratory in order to determine the pore size distribution (PoSD) and hydraulic conductivity (K (h)) functions in three different dates (after cover crop seeding, after maize seeding and before maize harvest) in order to follow the changes in soil pore functioning during the first year of cover cropping management. Changes in the soil pore functioning were observed in the short-term after the first cover crop cycle, showing the time-dependence of the hydraulic soil properties. These changes were mainly observed during the maize cycle. Under CF an increment of structural porosity (PS) was observed at the end of the maize crop cycle, while during the fallow period this variable remained relatively constant. K (h) and structural porosity connectivity (Cw) showed a rapid increment under BF during the fallow period, while under CF the increase was more gradual, which could be related to pore clogging and roots decay cycles. From the obtained results, we found that the introduction of cover crops under NT promotes the increment of a secondary pore system related to structural soil porosity during the first year and enhances the unsaturated hydraulic conductivity and pore connectivity, especially at the end of the summer crop cycle. Our results highlight the importance of including cover crops into the crop rotation to improve the structural porosity and its connectivity. As well, the results show the necessity of including the short-term changes in the study of soil hydraulics properties.

Raman spectroscopy study of ca 12.000 yrs cal BP lithic artifacts adhesions from archaeological sites in the Pampas region, Argentina

This paper presents the results of the first studies of non-destructive chemical and physical spectroscopic methods (Raman) applied to lithic artifacts recovered from five archaeological sites in the Pleistocene/Holocene transition of the Pampas region (Argentina). The aim of this paper is to identify the adhesions/alterations recognized in lithic stone tools and to discuss the different agents and taphonomic processes (natural and cultural) that created them. The results show that different chemical compounds (e.g., manganese, carbonate, phosphate, mineral pigments, organic compound [resin], etc.), were adhered to the surface of lithic artifacts as a result of natural processes and past human behavior. Furthermore, results obtained allow an understanding of the taphonomic agents that acted in the formation processes of archaeological sites and to generate a frame of reference to act as a control for assessing the impact that the mineral chemical dissolution and the occasional past human activity in the regional archaeological record of the eastern Tandilia range system.

Soil compaction response to wheel traffic in the Rolling Pampas region of Argentina

&#x0D; The present work shows the effects of the different agricultural wheels traffic on the soil physical properties on a Typic Argiudoll soil worked under no-tillage cropping system. Soil compaction produced by traffic was quantified through these parameters: a) cone index, b) rut depth and c) soil water content at the traffic moment. Grain chaser, sprayer, harvester combine and tractor equipped with commonly used wheels in the study area were tested. The main results obtained showed that the tyres with the highest inflation pressure and tyre ground pressures produced the highest values of cone index and rut depth. Typic Argiudoll soil worked under continuous no-tillage cropping system is not able to constrain topsoil and subsoil compaction when it is wheeled by tyre with ground pressures greater than 77.6 kPa.&#x0D; Highlights&#x0D; &#x0D; Soil compaction causes a reduction in root growth and yield in many crops.&#x0D; Soil under a no-tillage system does not limit topsoil and subsoil compaction when wheeled by tyres with ground pressures greater than 77.6 kPa&#x0D; When the machinery load increases on soils with high bearing capacity (soils under a long-term no-tillage system), the subsoil compaction problems increase.&#x0D;

Las moscas de las flores (Diptera: Syrphidae) en agroecosistemas pampeanos: un caso de estudio

Agroecosystems produce profound alterations on the structure and functioning of the original environment, mainly due to the reduction of biodiversity. Flower flies (Diptera: Syrphidae) are potentially useful organisms for the diverse ecosystem services they provide. We studied syrphids collected in a Pampean agroecosystem to assess richness, abundance, host plants, and the ecosystem services they could offer. Flower flies were represented by three subfamilies, eight tribes, 17 genera, and 26 species/morphospecies. Adults of these flies visited flowers of 44 species of wild and/or cultivated plants and exhibited a generalist interaction pattern. Larvae of the most abundant species were predators (mainly soft-bodied Hemiptera) and/or decomposers/aquatic filters. Only one species was pollinivorous. Our results, together with the scarce published bibliography, suggest that the syrphid communities of the highly modified Pampean region are composed of a few very abundant species and many rare or low representative species.

Genomic, karyological and morphological changes of South American garlics (Ipheion) provide insights into mechanisms of speciation in the Pampean region.

Speciation proceeds through mechanisms that promote reproductive isolation and shape the extent of genetic variation in natural populations, and thus its study is essential to understand the evolutionary processes leading to increased biodiversity. Chromosomal rearrangements are known to facilitate reproductive isolation by hybrid sterility and favour speciation events. The genus Ipheion (Amaryllidaceae, Allioideae) is unique as its species exhibit a remarkable karyological variability but lack population-level genetic data. To unveil the diversification processes acting upon the formation of new lineages within Ipheion in the Pampas of South America, we combined morphology and karyology approaches with genotyping-by-sequencing. Our phylogenomic and population genomics results supported the taxonomic division of Ipheion into three morphological and genetically well-differentiated groups. The origin of Ipheion uniflorum was traced back to its current southern distribution area in the southern Pampean region (in Argentina), from where it had expanded to the north reaching Uruguay. Our results further suggested that chromosome rearrangements and ploidy shifts had triggered speciation events, first during the origin of I. uniflorum and later during its subsequent diversification into I. recurvifolium and I. tweedieanum, in both cases reinforced by extrinsic factors and biogeographical settings. The current study illustrates the analytical power of multidisciplinary approaches integrating phylo- and population genomics with classic analyses to reveal evolutionary processes in plants.

Flood Risk and Adaptation Strategies for Soybean Production Systems on the Flood-Prone Pampas under Climate Change

In recent decades, multiple flood events have had a devastating impact on soybean production in Argentina. Recent advances suggest that the frequency and intensity of destructive flood events on the Argentinian Pampas will increase under pressure from climate change. This paper provides bottom-up insight into the flood risk for soybean production systems under climate change and the suitability of adaptation strategies in two of the most flood-prone areas of the Pampas region. The flood risk perceptions of soybean producers were explored through interviews, translated into climatic indicators and then studied using a multi-model climate data analysis. Soybean producers perceived the present flood risk for rural accessibility to be of the highest concern, especially during the harvest and sowing seasons when heavy machinery needs to reach soybean lots. An analysis of climatic change projections found a rising trend in annual and harvest precipitation and a slight drying trend during the sowing season. This indicates that the flood risk for harvest accessibility may increase under climate change. Several adaptation strategies were identified that can systemically address flood risks, but these require collaborative action and cannot be undertaken by individual producers. The results suggest that if cooperative adaptation efforts are not made in the short term, the continued increase in flood risk may force soybean producers in the case study locations to shift away from soybean towards more robust land uses.

Do soil carbon sequestration and soil fertility increase by including a gramineous cover crop in continuous soybean?

AbstractCover cropping is a farming practice that may improve C sequestration and soil fertility, but these effects can vary under different edaphoclimatic conditions. The effects of including a winter gramineous cover crop (CC) in continuous soybeans were evaluated in three long‐term experiments (8 yr) on one coarse‐textured soil and two fine‐textured soils in the Pampas region of Argentina. The impacts of CC on soil C sequestration, soil nutrient availability, soil organic C (SOC), and N contents of soil particle size fractions were also determined. The inclusion of CC only increased SOC stock by 3.1 Mg ha‐1 in the coarse‐textured soil (CTS). The labile C fraction in the 0–5‐cm depth increased in both the CTS and the fine‐textured soils (FTS) by 263% and 93%, respectively. Soil N also increased in the labile fraction by 119% and 112% when a CC was used in the CTS and FTS soils, respectively. Moreover, the inclusion of a CC decreased soil P availability in one experiment (4.9 kg ha‐1) and increased soil manganese in two experiments (11 kg ha‐1 on average). The inclusion of a gramineous CC in a soybean monoculture increased the C balance, particularly in coarse‐textured soils. Considering that soil N was similarly affected, the C/N ratio was not impacted.

Calibration of the potential evapotranspiration product “MOD16A2” for the Argentinian Pampas Region

Evapotranspiration (ET) is the hydrological variable with the greatest relevance in the Argentina Pampas Region (APR), because through this process a large part of the water that enters as precipitation is lost from the system. Knowing the spatial variability of the ET is essential to be able to include it in hydrological models. An alternative is the use of satellite products. In previous papers, the MOD16A2 product of potential ET (ETp) was evaluated, comparing it with in situ data of twenty-four stations distributed in the APR in 2012, 2013 and 2014, with a total of 3,094 pairs of analyzed data, observing a higher over estimation of 50% throughout the period which could be attributed to the error in the term of net radiation in the ETp equation. Using the same database, in this paper the systematic error found in the MOD16A2 product was corrected by means of a linear regression, using 60% of the data pairs ETp (MOD16A2) of in situ data to calibrate the model and the remaining 40% for its validation. The results showed a decrease in the mean square error of 2.4 to 0.6 mm day-1 and the mean absolute error of 2.2 to 0.5 mm day-1. After correction, the MOD16A2 product improves significantly and can be used for hydrological purposes at the basin scale. It is recommended for evaluating the method in large basins and in other regions of the world to determine if there are systematic errors, and eventually correct them following the procedure proposed here.