Agroecosystems Of Argentina Research Articles

Chaetophractus villosus (Cingulata: Chlamyphoridae)

Abstract Chaetophractus villosus (Desmarest, 1804) is commonly known as the large hairy armadillo. It is one of two living species of Chaetophractus. Like all armadillos, it bears a dorsal carapace of ossified dermal scutes covered by epidermal scales. Dorsal hair is sparse, long, and black and brown. This semifossorial armadillo inhabits grasslands, savannas, steppes, forests, and even degraded areas such as agroecosystems of Argentina, the “Gran Chaco” of Bolivia and Paraguay, and southern Chile. Chaetophractus villosus is omnivorous–carnivorous. It is listed as “Least Concern” (LC) on the International Union for Conservation of Nature Red List of Threatened Species, and is mainly affected by hunting, persecution as an agricultural pest, and vehicle collisions.

Effect of silicate fertilizers on wheat and soil properties in Southeastern Buenos Aires province, Argentina. A preliminary study

Silicon is a major component in soils and is essential for the development of certain crops that produce silicophytoliths. Although there are studies about the effect of silicate fertilizers, there is no research in soils of the Pampean Plains of Argentina. Therefore, the aim of this work was to evaluate the effect of two different sources of silicate fertilizers on plant and soil available silicon content and its role in the physical and chemical properties of agricultural soils under a wheat crop in southeastern Buenos Aires province. Field tests were carried out with the application of liquid and powder silicate fertilizers. Si content was analyzed in plant material. Morphological, physical and chemical properties were determined on surface soil samples. The Si content on wheat has doubled throughout the trial. The contribution of Si to the soil solution would be similar with both silicate fertilizers and the available phosphorus content showed a negative relationship with the available Si content. Such fertilization slightly influenced the structural stability and granulometry of soils. Although this work shows the first results about the effect of silicate fertilizers in agroecosystems of Argentina, it is necessary to deepen the knowledge about their effect on plant and soil quality.

Long-term association of Tyrannus savana and Sturnella superciliaris density with land cover and climatic variables in agroecosystems of Argentina

Agricultural expansion and intensification resulted in important changes in the agricultural landscape of the Pampas region, Argentina. We used linear mixed models to analyze the relationship between environmental variables associated to land use/cover, productivity and climate and changes in densities of two bird species, the Fork-tailed Flycatcher (Tyrannus savana) and the White-browed Blackbird (Sturnella superciliaris). The study area in central Argentina was divided in three agroproductive sub-regions: (1) predominantly agricultural, (2) mixed agricultural– rangeland and (3) mixed agricultural–forested rangeland. Bird populations were sampled annually during 2003–2011 using point-transects along secondary roads (48 transects). Mean estimated density for Fork-tailed Flycatcher was 0.132 ind/ha, increased in the agricultural sub-region and was associated with decreasing forest cover and increasing fallow and weedy fields cover. Mean density of the White-browed Blackbird was 0.045 ind/ha, decreased in the agricultural-rangeland sub-region and increased in landscapes with more perennial pastures, fallow and weedy fields and annual pastures, avoiding sites with more forest cover. Productivity and climatic variables only showed a strong association with White-browed Blackbird density. Our results suggest that land use/cover, productivity and climatic factors are important variables when planning strategies to conserve bird population at a regional level in agroecosystems of Argentina.

Field trials of line-transect surveys of bird carcasses in agro-ecosystems of Argentina’s Pampas region

Abstract Pesticides caused high mortality of birds in agro-ecosystems of Argentina’s Pampas region during 1995–2003. As part of a program to monitor mortality events, we trained observers in distance sampling methods, conducted field trials under simulated conditions to assess the degree to which the critical assumptions of line-transect surveys were met, and estimated the density and number of chicken carcasses randomly placed along fixed transects in corn stubble, corn, alfalfa, wheat, pasture, and forest. The assumption of 100% detection probability of carcasses at 0 distance was met. We measured cluster size (1–5 carcasses) exactly and measured perpendicular distance from a cluster to transect centerline (0–40 m) with little error (absolute difference between actual and measured distances: x=0.14 m, SE=0.01, n= 121). Cluster detection was not size-biased in corn stubble but was size-biased in corn, alfalfa, wheat, pasture, forest, and all strata combined. Thirteen 3-observer teams performed equally w...

Scale-dependent controls on ecological functions in agroecosystems of Argentina

Agricultural managers that operate at different levels (plot, farm, landscape, region) need to understand how ecological functions (energy, nutrients and water flows and cycles) are controlled by scale-dependent factors. Using cross-level data from the Argentine pampas, analyzed by simple and multiple regression analysis, we demonstrate that controls differ from one spatio-temporal level to the other, but they can be altered by humans. In the Argentine pampas, environmental controls (climate, landform, soil quality) seem to have a strong top-down influence on lower levels. But the bottom-up aggregated effect of anthropogenic controls seems to scale-up to upper levels and counteract such influence. Thus, the more intense use of land and technology in small units, the larger the up-scaling human influence on ecological functions. We suggest that a discrimination among farming intensity levels is useful and necessary to understand and predict human controls on ecological functions across scales.