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Urbanization is one of the most extreme land-use changes and has impacts on climate, water and biodiversity in large areas throughout the planet. In this paper, we quantified the urban heat islands (ICU, acronym in Spanish) and their relation to biophysical parameters of the surface of the earth along the main environmental gradients of Argentina. We analyzed 55 of the largest cities in the country, located in 10 ecoregions, using satellite data (MODIS) of land surface temperature, albedo and vegetation indexes (NDVI) and climatic variables. The average annual ICU in the cities for 2011-2015 was 0.36±1.99 °C for the day and 1.68±0.61 °C for the night. The main drivers of the ICU during the day were rural NDVI, mean precipitation and temperature. At night, the main driver was the difference between urban and rural blue albedo. During the day, some cities behaved like urban cold islands (IFU, acronym in Spanish) associated with arid climates or agricultural contexts, while at night, all cities behaved like ICU. The cooling effect of urban vegetation was identified from the difference between urban and rural NDVI, but no direct negative relationship between ICU and urban NDVI was observed. These results provide new insights on the drivers of the ICU and facilitate the generation of urban development strategies to mitigate the effects of urbanization and to improve the quality of life of urban populations. [ABSTRACT FROM AUTHOR]

The design of sustainable, high-yielding continuous cropping systems requires to maintain, or even restore, critical ecosystem properties, such as soil functioning. In the rolling Pampa (Argentina), total soil organic carbon decreased by 15–40% due to continuous agriculture. Therefore, soils are far from their potential carbon saturation. The most promising strategies to increase yield and restore carbon rely on the sustainable intensification of the current cropping systems based on no-tillage practices. Such strategies also involve increasing resource use through cover crops, increasing cropping intensity, and performing accurate and flexible fertilization and crop protection schemes. This study evaluated the effects of different cropping systems on soil organic carbon stocks in the uppermost 20 cm of the soil profile. We performed a 5-year experiment combining five cropping systems with different cash crop sequence (soybean mono-cropping and two different rotations) and agronomic technology (genotypes, fertilization, and crop protection), which in turn were evaluated under both fallow and cover cropping. Five years after the beginning of the experiment, all systems had a net positive balance of soil carbon accumulation, which averaged 2.25 t C.ha-1.yr-1. On average, 41% of plant carbon inputs remained within the first 20 cm of the soil profile. Cover crops increased plant carbon inputs, with larger effects as the cash crops occupied a shorter period in the field. Therefore, compared to fallow, cover crop doubled carbon input in soybean mono-cropping, had intermediate increments in the maize-soybean sequence, and had the lowest increments in the wheat/soybean-maize-soybean sequence. Under fallow, both rotations outperformed the plant carbon inputs of soybean mono-cropping. Management intensification, only evaluated for rotations, increased plant carbon inputs and soil carbon accumulation in a synergistic interaction with cover crop. Our results indicate that increasing carbon inputs through crop rotation, cover cropping and better agronomic technology is an opportunity to revert the long trend of soil carbon deficit of these agricultural lands. • Approximately 41% of plant carbon inputs remained in soil. • Intensified management and cover cropping acted synergically. • Crop rotations with more frequency of maize accumulated more soil carbon. • Cover cropping doubled annual carbon inputs of soybean mono-cropping. [ABSTRACT FROM AUTHOR]

Abstract: Temperate grasses frequently acquire resistance to herbivores through a symbiosis with epichloid fungi that produces alkaloids of variable deterrent effects. However, in those cases without apparent endophyte negative effects on domestic herbivores, it is not clear whether plant consumption or preference is affected or not. We performed three experiments with 1‐year‐old steers (Bos taurus, Aberdeen Angus) and the annual grass Lolium multiflorum, infected or not by Epichloë occultans to evaluate preference and to identify the underlying tolerance mechanisms. The first experiment evaluated steer preference for L. multiflorum cultivated in plots with three endophyte infection frequencies (low, medium and high), and investigated the role of canopy structure and plant nutritional traits on preference. The second experiment evaluated preference for chopped grass, offered in individual trays with contrasting infection frequencies (low and high), to discard possible effects associated with canopy structure and to focus on nutritional traits. The third experiment was performed with a tray + basket design that separated visual and olfactory stimuli from nutritional traits. High endophyte infection frequencies reduced consistently animal preference, even after short (~10 min) feeding events. However, we did not find significant evidence of plant structural, nutritional, visual or olfactory traits. Our results discarded several potential mechanisms; therefore, the dissuasive effect of fungal endophytes on animal consumption might be related to other mechanisms, including, likely, alkaloids and changes on grass metabolome. [ABSTRACT FROM AUTHOR]

Agricultural intensification simplified environments, reduced their diversity, and hindered their ecosystem processes. Permanently vegetated areas (uncultivated margins) embedded in the cultivated matrix play a critical role in maintaining diversity and soil properties, and so mitigate the negative impact of intensification. We performed two studies aimed at evaluating the role of uncultivated margins on soil heterotrophic bacteria. In the first study, we sampled soybean fields and herbaceous and woody margins in three locations along a 100-kilometer transect. In a second study, in one location we sampled uncultivated margins and perpendicular 50-meter transects from each margin towards the centre of its adjacent soybean field. As control, we sampled similar transects in soybean fields that had cropped fields as margins. In both studies, we characterized the catabolic profiles and diversity of the heterotrophic bacterial community and soil properties. Soil microbial communities of uncultivated margins differed in composition and were more diverse than the cropped matrix. In turn, these differences positively correlated with soil pH. Woody margins also influenced the soil microbial composition, diversity and soil pH of neighbouring cultivated fields. In contrast, herbaceous margins did not influence their cultivated neighbours. These results broaden our understanding of soil heterotrophic bacterial community in agro-ecosystems and its implications for ecosystem functioning. [ABSTRACT FROM AUTHOR]

1. The strength of many interactions between plants and other organisms changes across regional gradients. For example, the relevance of plant-herbivore interactions increases with primary production. Likewise, biotic interactions collectively become more intense from the poles to the equator. Yet, the regional variation of the interaction between grasses and systemic fungal endophytes, which provide resistance to biotic and abiotic environmental factors (i.e. herbivory and drought), is poorly understood. 2. We compiled 1008 records of the incidence level of fungal endophytes (Epichloë, Ascomycetes: Clavicipitaceae) on wild populations of 48 cool season grasses, encompassing 10 biomes across a broad latitudinal expanse and primary production gradient. Symbiosis incidence was analysed as a function of mean primary production, precipitation, temperature and latitude of each site, which in turn were obtained from climatic and satellital sources. 3. Across a 30-fold variation of mean primary production, average symbiosis incidence increased from 20% to 70%. The pattern became stronger when the analysis was restricted to the single grass genus Festuca, which accounted for half of the total data. 4. The number of grass populations showing no symbiosis incidence (0%) decreased as primary production increased, whereas those with 100% of incidence increased. 5. Primary production at the regional scale was negatively correlated with latitude but positively with mean annual temperature and precipitation. Symbiosis incidence was similarly correlated with latitude and temperature, and it was not with mean annual precipitation. 6. Synthesis. Different descriptors of this grass-fungus symbiosis show that average incidence in wild populations world-wide increases with mean primary production. As at large spatial scales herbivory and temperature increase and aridity decreases with primary production, our results suggest that, at broad-scales, these biotic and abiotic factors may be important drivers of the symbiosis success. [ABSTRACT FROM AUTHOR]

The symbiosis between cool-season grasses and fungi of the genus Epichloë is widespread, but highly variable in natural ecosystems. Biotic and abiotic controls underlying its distribution patterns have been difficult to establish, but might be related to a greater capacity of infected plants to deal with drought and herbivory. In this study we examined the relationship between grazing intensity and symbiosis frequency in plant species differentially preferred by herbivores. In all the grass species found in the studied Patagonian steppe, we determined the infection frequency along a grazing gradient by sheep (ungrazed, moderate- and intense-grazing). Three out of five preferred species and one out of four non-preferred species presented the symbiosis. Within the group of species having the symbiosis, intense grazing decreased the infection frequency of the preferred species while the frequency of the non-preferred species remained constant. These changes of infection frequency were correlated with changes in tiller biomass of hosts suggesting that symbiosis frequency could depend on overall plant performance. Our results suggest that high grazing intensity could weaken the relationship between these endophytes and their palatable hosts, eventually making them even more vulnerable to further grazing. [ABSTRACT FROM AUTHOR]

Highlights: [•] Woody margins had the largest soil carbon stocks while herbaceous margins had the smallest ones. [•] Woody margins increased soil carbon stocks of neighbouring crops. [•] Differences in litter quality and decomposition among margins accounted for variation in soil carbon stocks. [Copyright &y& Elsevier]

In sugarcane cropping systems, green-cane harvesting has progressively replaced the traditional burning of standing crop prior to harvest, increasing the role of decomposition as a mechanism to replenish soil nutrients. We examined the impact of cultivar choice and irrigation water quality on decomposition of sugarcane residue. In two independent litterbag experiments, we isolated the effects of changes in plant residue quality and irrigated water quality. Cultivar residue exhibited significant variation of carbon and nitrogen concentrations and carbon to nitrogen ratio. Decomposition rate varied among cultivars, and those with greater carbon-to-nitrogen ratios decomposed faster than cultivars with lower ratios. Soil irrigated with river water showed a lower mineral and organic nitrogen concentration and decomposition rate than those irrigated with industry effluent wastewater. These results provide empirical evidence that both cultivar choice and water used for irrigation have a limited but significant impact on plant residue decomposition. [ABSTRACT FROM AUTHOR]

The impact of grazing widely differs among plant communities. A generalized model published in 1988 proposed that this variation could be accounted for by the interaction between primary productivity and the evolutionary history of grazing. As productivity increased, the model predicted larger changes of species composition. Evolutionary history of grazing interacted with productivity: the changes in low-production systems were smaller if evolutionary history was long, whereas the changes in high-production systems were independent of evolutionary history. In this paper, we focus on: (i) the difficulties of determining the evolutionary history of grazing of a community, and (ii) additional mechanisms, which, as a sequence of filters in the process of community assembly, could be operating across the gradient of primary production. Assigning a given evolutionary history of grazing to a site has been difficult due to the lack of information on the historical population and distribution of herbivores with an adequate spatial and temporal resolution, and the lack of agreement on the size of the relevant evolutionary time window. Regarding the variation through a gradient of primary production, we propose three additional mechanisms coherent with the prediction of the model. First, the regional pool of available species increases with primary production. Second, grazing intensity (consumption as a proportion of above-ground production) also increases with primary production. Third, the strength of interspecific positive biotic interactions that protect plants from herbivores decreases with primary production. We highlight an additional potential mechanism, seed dispersal, whose variation across the gradient of productivity is not yet sufficiently understood. By connecting the logic of environmental filters to explain community assemblage with the original proposition of the generalized model, we suggest a series of research lines that can lead to a better understanding of why different communities respond differently to grazing. [ABSTRACT FROM AUTHOR]

Grazing-induced floristic changes in plant communities may accelerate or reduce plant and soil processes through changes in litter quality. Here, we intended to elucidate if the joint action of live and senescing plant tissue of palatable and non-palatable species differentially influences soil processes and properties. We conducted a 1-year experiment with mesocosms from a subhumid grassland. Mesocosms were monocultures of palatable or non-palatable species and a multispecific control. Palatable species included a legume and annual and perennial grasses, whereas non-palatable species included a perennial grass and annual and perennial forbs. Palatable monocultures showed greater soil mineral nitrogen, soil bacterial diversity, and lower soil pH than non-palatable monocultures. These differences were not accounted for by differences in plant biomass. The multispecific control treatment only exhibited greater shoot biomass than the monocultures, and lower root biomass than the palatable monocultures. Our results suggest that the whole (live + dead plant tissue) had a specific imprint on soil system even when variation was not very apparent in terms of plant biomass, and that this effect was associated with plant palatability to domestic large herbivores. [ABSTRACT FROM AUTHOR]

Large herbivores may alter carbon and nutrient cycling in soil by changing above- and below-ground litter decomposition dynamics. Grazing effects may reflect changes in plant allocation patterns, and thus litter quality, or the site conditions for decomposition, but the relative roles of these broad mechanisms have rarely been tested. We examined plant and soil mediated effects of grazing history on litter mass loss and nutrient release in two grazing-tolerant grasses, Lolium multiflorum and Paspalum dilatatum, in a humid pampa grassland, Argentina. Shoot and root litters produced in a common garden by conspecific plants collected from grazed and ungrazed sites were incubated under both grazing conditions. We found that grazing history effects on litter decomposition were stronger for shoot than for root material. Root mass loss was neither affected by litter origin nor incubation site, although roots from the grazed origin immobilised more nutrients. Plants from the grazed site produced shoots with higher cell soluble contents and lower lignin:N ratios. Grazing effects mediated by shoot litter origin depended on the species, and were less apparent than incubation site effects. Lolium shoots from the grazed site decomposed and released nutrients faster, whereas Paspalum shoots from the grazed site retained more nutrient than their respective counterparts from the ungrazed site. Such divergent, species-specific dynamics did not translate into consistent differences in soil mineral N beneath decomposing litters. Indeed, shoot mass loss and nutrient release were generally faster in the grazed grassland, where soil N availability was higher. Our results show that grazing influenced nutrient cycling by modifying litter breakdown within species as well as the soil environment for decomposition. They also indicate that grazing effects on decomposition are likely to involve aerial litter pools rather than the more recalcitrant root compartment. [ABSTRACT FROM AUTHOR]

Net primary production (NPP) and nutrient dynamics of grasslands are regulated by different biotic and abiotic factors, which may differentially affect functional plant groups. Most studies have dealt with grasslands that have extremely low or zero production over a significant period of the year. Here we explore the relative importance of a few environmental factors as controls of aerial and below-ground plant biomass production and nutrient dynamics in a grassland that is active throughout the year. We investigate their effect on the response of three main plant functional groups (warm- and cool-season graminoids and forbs). We conducted a factorial experiment in a continuously grazed site in the Flooding Pampa grassland (Argentina). Factors were seasons (summer, autumn, winter and spring), and environmental agents (mowing, shade, addition of phosphorus [P] and nitrogen [N]). N addition had the largest and most extended impact: it tripled aerial NPP in spring and summer but had no effect on below-ground biomass. This positive effect was accompanied by higher N acquisition and higher soil N availability. Mowing increased aerial NPP in winter, increased root biomass in the first 10 cm during autumn and winter and promoted N and P uptake by plants. Shading did not affect aerial NPP, but stimulated N and P uptake by plants. P addition had no effect on aerial NPP, but increased shallow root biomass and its N content in spring, and tripled P accumulation in plant biomass. The three plant functional groups differentially accounted for these ecosystem-level responses. Graminoids explained the greater biomass production of N-fertilized plots and mowing tended to promote forbs. These results suggest that the environmental controls of aerial NPP in this grassland vary among seasons, differentially impact the major floristic groups, and affect the energy and nutrient transfer to herbivores. [ABSTRACT FROM AUTHOR]

Changes in plant community composition induced by vertebrate grazers have been found to either accelerate or slow C and nutrient cycling in soil. This variation may reflect the differential effects of grazing-promoted (G+) plant species on overall litter quality and decomposition processes. Further, site conditions associated with prior grazing history are expected to influence litter decay and nutrient turnover. We studied how grazing-induced changes in plant life forms and species identity modified the quality of litter inputs to soil, decomposition rate and nutrient release in a flooding Pampa grassland, Argentina. Litter from G+ forbs and grasses (two species each) and grazing-reduced (G−) grasses (two species) was incubated in long-term grazed and ungrazed sites. G+ species, overall, showed higher rates of decomposition and N and P release from litter. However, this pattern was primarily driven by the low-growing, high litter-quality forbs included among G+ species. Forbs decomposed and released nutrients faster than either G+ or G− grasses. While no consistent differences between G+ and G− grasses were observed, patterns of grass litter decay and nutrient release corresponded with interspecific differences in phenology and photosynthetic pathway. Litter decomposition, N release and soil N availability were higher in the grazed site, irrespective of species litter type. Our results contradict the notion that grazing, by reducing more palatable species and promoting less palatable ones, should decrease nutrient cycling from litter. Plant tissue quality and palatability may not unequivocally link patterns of grazing resistance and litter decomposability within a community, especially where grazing causes major shifts in life form composition. Thus, plant functional groups defined by species’ “responses” to grazing may only partially overlap with functional groups based on species “effects” on C and nutrient cycling. [ABSTRACT FROM AUTHOR]

Continuous biomass removal by grazing usually changes the resource allocation pattern of plants. These changes often increase resistance to tissue removal and produce individuals with different morphometric traits, such as root to shoot or blade to sheath ratios. Shifts in morphometric traits, in turn, may alter nutrient cycling through changes in the average quality of litter that decomposes in soil. Previous work has shown that Paspalum dilatatum, a native grass from the Pampas grasslands, which inhabits a vast area and supports a wide range of grazing conditions, increases its blade to sheath ratio under continuous grazing with respect to ungrazed conditions. Here, we explored the consequences of these changes apparently associated with grazing regime on litter quality and nutrient dynamics during litter breakdown in soil. We separately analysed litter quality of blades and sheaths of P. dilatatum and determined under controlled conditions their decomposition and nutrient release kinetics over a maximum period of 1 year. We also studied the mineral nitrogen contents in soil amended with each litter type. Blade quality was significantly higher than sheath quality, nitrogen concentrations of blades and sheaths were approximately 1% and 0.6%, respectively, and lignin to nitrogen ratios were approximately 5 and 11 for blades and sheaths, respectively. Phosphorus concentration, however, was similar in both litter types. Blades decomposed 10% faster than sheaths, released 20% more nitrogen and released 15% more phosphorus than sheaths during the last half of the incubation period. During the first 3 months, the soil nitrogen content of litter-amended incubations indicated immobilization with respect to non-amended control; however, later blade incubations mineralized nitrogen, whereas sheath incubations continued immobilizing it. Results revealed that grazing potentially accelerates nutrient cycling during decomposition by increasing the blade to sheath ratio of P. dilatatum individuals, and suggest that this may be an important mechanism underlying grazing impact on nutrient cycling. [ABSTRACT FROM AUTHOR]

The description of the relationship between temperature (T) and electricity consumption (EC) is key to improving our understanding of a potential climate change amplification feedback and, thus, energy planning. We sought to characterize the relationship between the EC and daily T of different regions of Argentina and use these historical relationships to estimate expected EC under T future scenarios. We used a time series approach to model EC, removing trends and seasonality and accounting for breaks and discontinuities. EC and T data were obtained from Argentine Wholesale Market Administrator Company and global databases, respectively. We evaluate the T-EC model for the period between 1997 and 2014 and two sub-periods: 1997–2001 and 2011–2014. We use modeled temperature projections for the 2027–2044 period based on the Representative Pathway Concentration 4.5 together with our region-specific T-EC models to predict changes in EC due to T changes. The shape of the T-EC relationships is quite stable between periods and regions but varies according to the temperature gradient. We find large increases in EC in warm days (from 40 to 126 Wh/cap/°C) and a region-specific response to cold days (from flat to steep responses). The T at which EC was at minimum varies between 14 and 20 °C and increase in time as mean daily T also increase. Estimated temperature projections translate into an average increase factor of 7.2 in EC with contrasting relative importance between regions of Argentina. Results highlight potential sensitivity of EC to T in the developing countries. [ABSTRACT FROM AUTHOR]

Emerging economies (Brazil, Russia, India, China and other countries) are expected to play a major role in the global economy during the 21st century. Some of these countries have exceptional soil and climate characteristics that determine evident advantages for food production. These features, combined with a rapid adoption of technologies generated by industrialized economies (i.e. transgenic crops and others), have been instrumental to fast expansion of agricultural production in recent years. For such reasons, some of these economies are strongly based on production of food commodities (agriculture represents 18.3, 12.6, 9.4 and 8.1% of the gross domestic product of India, China, Argentina and Brazil, respectively) and have a great share in global food production. Despite the mentioned characteristics that make agricultural activity so efficient in these countries, generation of new technologies in order to guarantee the systems' sustainability and add value to agricultural production (by means of, for example, royalties or technologies generated with local criteria) relies on research carried out in areas such as crop science, biotechnology, ecology, plant breeding and, of course, seed science. However, the amount of local research carried out in these countries appears not to be in agreement with the importance that agricultural production has in their economies. For example, Argentina produces 16.20% of the soybean produced in the world but only 2% of the scientific literature related to this crop in its many aspects. This imbalance between the weight that agricultural production has on these economies and generation of knowledge in the related disciplines, threatens the sustainability of these economic models and, therefore, of global food production. Seed science, then, is called on to play a major role in these emerging economies, through the different approaches (i.e. ecological, physiological, agronomical and molecular) that the discipline has to offer. Here we provide four examples in which seed science (through any of the four approaches mentioned above): (1) has identified subtle but crucial components of newly adopted production systems; (2) has proposed means for their adjustment in order to secure the sustainability of those systems; and (3) might help to add value to agricultural production through the development of new germplasm displaying specific features (e.g. timing of dormancy release adjusted to industrial necessities). [ABSTRACT FROM PUBLISHER]

Changes in land use often increase the provisioning ecosystem services at the cost of decreasing the regulating services. Thus, the appropriation of primary production to optimize the supply of forage for livestock production may undermine C and N storage, essential to maintain the integrity of ecological systems and the biosphere. The aim of this work was to study this trade-off by estimating the effect of grazing intensity on two provisioning and regulating ecosystem services (forage supply and C and N storage, respectively) in a 300 km 2 Patagonian steppe. In areas with different historical sheep grazing regime (intensive, moderate and ungrazed), we estimated forage supply through the aboveground biomass of preferentially consumed species as well as total C and N storage in plants, through forage and non-forage aboveground biomass, litter and root biomass in the top 20 cm of soil. We found that forage supply and C and N storage were highest in moderately grazed areas and were positively correlated, indicating the absence of trade-offs between them. Grazing exclusion had no effect on total plant C and N, but decreased these stocks in green grass biomass in relation to moderate grazing. Intensive grazing decreased both provisioning and regulating services, markedly diminishing grass C and N stocks and grass forage compared to other conditions. Conversely, shrubs and roots were not influenced by grazing regime. This study provides evidence that in arid rangelands, an adequate grazing management could be a key control to complementarily maximize both provisioning and regulating ecosystem services. [ABSTRACT FROM AUTHOR]

In the semiarid Chaco savannas, the balance between herbaceous and woody species affects landscape configuration and ecosystem services such as forage production. Therefore, understanding the factors that control this balance is crucial for management. In a factorial experiment, we assessed the effects of fire and water availability on the emergence and recruitment of grasses, forbs and woody species. The results showed that the effects of fire and water availability on early regeneration stages differed among the three functional groups. For grasses, fire and water addition enhanced emergence when acted solely, but only the positive effects of fire were translated into a greater recruitment, irrespective of the water availability. For forbs, only water addition, when acted solely, promoted the emergence, although this effect was not translated into a greater recruitment. Lastly, in the case of woody species, both fire and water addition reduced emergence and recruitment. Our results support the notion that both fire and greater water availability would contribute to the maintenance and recovery of a grass-dominated state of vegetation through a positive effect of fire on grasses recruitment and a general negative effect of fire and water on woody species emergence and recruitment. [ABSTRACT FROM AUTHOR]

Feedbacks between plants and soil microbes are critical for ecosystem regulation and restoration. Soil microbial diversity is largely dependent on plant diversity, yet these relationships have received little attention at the landscape scale. In agricultural landscapes, the presence of different plant cover types (landscape elements) can modulate these feedbacks by adding spatial heterogeneity through changes in the amount and composition of plant residues. Furthermore, it can also influence the soil biota. Therefore, the more diverse the landscape elements of farmlands, the higher the increase of their heterogeneity. We investigated the microbial catabolic profiles and respiration rates of soils from different plant cover types through the manipulation of plant residues and microbial communities. In individual microcosms, we incubated sterilized soils sampled from five different cover types of a temperate agricultural landscape: Soybean Monocropping, two crop rotations (Rotation and Intensified Rotation) and two uncropped margins: Herbaceous and Woody spontaneous vegetation. We amended them with each of two plant residues: wheat stubble (Wheat) and a mix of spontaneous vegetation (Mix). Soils were also inoculated with each of two soil microbial communities: Soybean Monocropping and Woody margins. We predict that soils treated with the Mix residue and the Woody margins community will show higher catabolic diversity and respiration than those treated with Wheat stubble and Soybean Monocropping community. In turn, we predict that soils from Woody margins, with higher carbon content, will respire more and amplify the effects of plant residue and microbial community. The microbial catabolic profile changed with plant residue and microbial community whereas the microbial respiration changed with cover type. After 30 days of incubation, soils inoculated with Woody margin community sustained higher diversity than those inoculated with Soybean Monocropping community. Conversely, Wheat stubble increased microbial diversity with respect to the Mix, particularly in soils from Woody margins while Mix residue increased the microbial diversity of soils from Soybean Monocropping. Finally, microbial respiration of soils from Woody margins showed the greatest respiration and Soybean Monocropping the lowest, in correlation with their carbon contents. Despite the complex interactions between soil carbon contents and plant residue composition, our results suggest that internal transfers of soil and plant residue between the different landscape elements might contribute to increasing the resilience of agricultural landscapes. • The microbial catabolic profiles changed with plant residues and microbial community. • Wheat residues increased microbial diversity of soils from woody margins. • Mix residue increased microbial diversity of soils from soybean monocropping. • Soil microbes from woody margins had the highest diversity across all soils. • Soil microbial respiration was only affected by cover type. [ABSTRACT FROM AUTHOR]

Agricultural intensification has increased food production by reducing crop diversity and increasing fertilization and crop protection. Unfortunately, intensification has also reduced soil ecosystem services. Diversifying crop rotations could be a feasible alternative to promote positive feedbacks between soil biota and soil properties. Here, we investigated the impact of diversifying crop rotations on functional composition and diversity of the heterotrophic soil bacterial communities. We studied three frequent rotations with a total number of crops ranging from two to four. Before the experiment, all plots were cultivated with soybean. In the first experimental year, the crop sequences were (1) fallow/soybean, (2) barley/soybean, and (3) field pea/maize. In the second year, all plots were subjected to a wheat/soybean double crop. The experiment was replicated in three locations of the Rolling Pampa (Argentina). Soil and plant sampling took place immediately after the soybean harvest, in the second year. The most diverse rotation (field pea/maize, wheat/soybean) showed the highest standing biomass and litter and the most metabolically diverse and active soil microbial community (P ≤ 0.05). In turn, metabolic diversity was positively associated with plant and litter biomass (r 2  = 0.7) and with soil pH (r 2  = 0.72). Our results revealed that crop rotation affects soil metabolic bacterial diversity and activity (P ≤ 0.05). The most diverse rotation (four different crops) had also the most diverse and active soil microbial biota, concomitantly with a higher plant biomass production and soil pH. Because soil microbial activity and metabolic diversity detected in specific rotations potentially contribute to soil aggregate formation and other soil properties intimately related with nutrient cycling and plant production, the negative effect of agricultural intensification could be attenuated by designing specific and more diverse crop rotations. [ABSTRACT FROM AUTHOR]

Extensive agriculture imprints a certain spatial and temporal homogeneity on a landscape and often hides its natural heterogeneity. Moreover, this homogenization may be disconnected from land use capacity, increasing the risk of land degradation. We described the anthropogenic and natural heterogeneity of an agricultural basin of the central Rolling Pampa of Argentina, to assess whether the current land use is consistent with the natural land capacity. First, we mapped and characterized the anthropogenic and natural spatial heterogeneity through two independent analyses, one based on land cover and the other on geomorphological and edaphic variables. Second, we investigated the relationship between anthropogenic and natural heterogeneity by integrating the previous analyses with a third one, focused on vegetation activity (normalized difference vegetation activity index, NDVI). The results showed two anthropogenic landscape units, whereas six natural landscape units were identified. Anthropogenic landscape I was mainly associated with natural landscapes 1, 2 and 3. These landscapes were characterized by large, regularly shaped fields dominated by soybean. Anthropogenic landscape II was associated with natural landscapes 4, 5 and 6, which were characterized by smaller and more irregularly shaped fields and were more diversely cultivated than the other group of landscapes. Anthropogenic landscape I and its three associated natural landscapes had lower average vegetation activity but higher seasonal and inter-annual variation than anthropogenic landscape II and its associated landscapes. In conclusion, on a landscape level, natural heterogeneity may be hidden in agricultural landscapes with highly homogeneous land use, such as the Pampas region. If not taken into consideration, this could increase the risk of land degradation in certain conditions or landscapes. • Agricultural practices hide agroecosystems' natural heterogeneity. • The lack of a relationship between anthropogenic and natural heterogeneity could increase the risk of soil degradation • Multivariate and remote sensing techniques can be combined to analyse agricultural landscapes in an integrated way. [ABSTRACT FROM AUTHOR]

Many complex, natural landscapes have been transformed into simpler agroecosystems by continuous cropping and the application of glyphosate and fertilizers. The current mosaic with different land cover types can harbor different soil microbial communities. Here, we investigated how the microbial community and ryegrass plants responded to glyphosate and nitrogen application to soils from four different cover types (soybean monocropping; wheat/soybean-field pea rotation, herbaceous- and woody- uncropped margins). We predict that soils from different land cover types will display different responses of their detritivore microbial communities and plant growth to herbicide and fertilizer application. All the studied variables differed among land cover types. Woody margins tripled the soil carbon content and the microbial respiration of herbaceous margins, although the later had more diverse soil microbial communities. Soils from soybean monoculture had higher respiration rates (37%) than those from crop rotation, where ryegrass accumulated lower biomass (12% lower). Despite these differences between land cover types, neither glyphosate nor nitrogen fertilization significantly influenced these properties. Only ryegrass plants growing on glyphosate-treated soils accumulated more biomass than the rest whereas they did not respond to nitrogen. These results suggest that glyphosate and nitrogen at recommended doses did not have a significant impact on the soil performance of the different types of cover. • Different land covers promote environmental and microbial heterogeneity in arable soils. • Soil microbes and ryegrass growing in monocropping soils outperformed those from crop rotation. • Microbial respiration and composition from different land covers were not affected by glyphosate and nitrogen addition. [ABSTRACT FROM AUTHOR]