Human appropriation of primary production in the Dry Chaco

El Chaco Seco experimenta altas tasas de deforestación y transformación productiva. Estimamos la magnitud de la apropiación humana de la productividad primaria neta (PPN) aérea de esta región por vías directas (producción ganadera, forestal y agrícola) e indirectas (fuego), su distribución regional, su relación con variables climáticas y socioeconómicas y sus contrastes entre vegetación natural, pasturas y cultivos. Para 69 departamentos se utilizaron datos censales, climáticos y satelitales (período 2002-2006) a partir de los que se estimó la PPN aérea con modelos climáticos, la apropiación de forraje por ganadería con datos de stock animal y modelos metabólicos, la apropiación de productos agrícolas y forestales con estadísticas nacionales y apropiación indirecta de biomasa por fuego a partir sensores remotos. La ganadería, desarrollada bajo vegetación natural y pasturas (90.9% del área), involucró una apropiación de 248 kgMS.ha-1.año-1, y aumentó en departamentos con mayor fracción de pasturas, ganado agrupado en rodeos más grandes y menores niveles de pobreza. La apropiación forestal, desarrollada bajo vegetación natural (88.7%), alcanzó 64 kgMS.ha-1.año-1 representados predominantemente por carbón vegetal y leña, y fue mayor en departamentos de clima más húmedo. En la fracción agrícola del territorio (6.3%), la apropiación directa trepó a 2293 kgMS.ha-1.año-1, representada principalmente por grano de soja y maíz. La apropiación indirecta por fuego promedió 746 kgMS.ha-1.año-1 para todo el territorio. Este flujo estuvo positivamente asociado a la tasa de desmonte, ascendiendo de ~450 a >2000 kgMS.ha-1.año-1 al pasar de departamentos con mínimo a máximo desmonte. En la actualidad, la baja apropiación de la PPN de la vegetación natural del Chaco Seco constituye un incentivo para su reemplazo por pasturas y cultivos anuales. Una actividad ganadera y/o forestal más eficiente en los bosques representa un desafío tecnológico y político prioritario capaz de reconciliar la producción y la conservación en esta región.The Dry Chaco undergoes high rates of deforestation and productive transformation. Here we estimate human appropriation of net aboveground primary productivity (NPP) for this region, both through direct (livestock, logging, and agricultural production) and indirect pathways (burning), and present their regional distributions and their association with climatic and socioeconomic variables and their contrast between natural vegetation, pastures and crops. For all the 69 counties encompassed by the region we collected productive and climatic statistics and remote sensing data (2002-2006 period). We estimated aboveground NPP based on existing climatic models, forage appropriation based on livestock statistics and metabolic models, forest and agricultural product appropriation using national statistics, and indirect appropriation or consumption by fires based on remote sensing information. Livestock production, based on natural vegetation and pastures (90.9% of the area) appropriated 248 kgDM.ha-1.yr- 1 , increasing in counties with larger pasture proportion, cattle grouped in large herds, and lower poverty levels. The appropriation of forest products, restricted natural vegetation (88.7% of the area), reached 64 kgDM.ha-1.yr-1, represented predominantly by charcoal and firewood, increasing in more humid counties. In the agricultural fraction of the territory (6.3% of the area), direct appropriation reached 2293 kgDM.ha-1.yr-1, represented mainly by soy and corn grain. The indirect appropriation of NPP through fires averaged 746 kgDM.ha-1.yr-1 for the whole territory. This flux was positively associated to the rate of deforestation, climbing from ~450 to >2000 kgDM.ha-1.yr-1 from counties with minimum to maximum deforestation rates. Currently, the low direct appropriation of NPP under natural vegetation in the Dry Chaco involves a strong incentive for its replacement with pastures and annual crops. More efficient livestock and forestry activities in these forest ecosystems represent a technological challenge and a policy making priority capable of reconciling production and conservation in the region.Fil: Rueda, Carla Vanezza. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Matemática Aplicada de San Luis; Argentina. Universidad Nacional de Santiago del Estero. Facultad de Ciencias Forestales; ArgentinaFil: Baldi, Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Matemática Aplicada de San Luis; ArgentinaFil: Verón, Santiago Ramón. Instituto Nacional de Tecnología Agropecuaria. Centro Nacional de Investigaciones Agropecuarias. Centro de Investigaciones de Recursos Naturales. Instituto de Clima y Agua; ArgentinaFil: Jobbagy Gampel, Esteban Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Matemática Aplicada de San Luis; Argentin

Fuegos para energía: una oportunidad económica y ambiental para los bosques secos de Argentina

A medida que las consecuencias ambientales y económicas derivadas del uso de combustibles fósiles se hacen evidentes, los ecosistemas comienzan a ser identificados como fuentes de energía biológica o bioenergía. Si bien la biomasa vegetal fue la principal fuente de energía de la humanidad hasta la revolución industrial, la renovada atención que están recibiendo los ecosistemas terrestres actualmente, compite con una apropiación de alimentos, fibras y productos forestales sin precedentes en la historia del planeta. El auge de los biocombustibles en Argentina, promocionados por la Ley 26.093, puede tener impactos adversos en la producción de alimentos y beneficios climáticos limitados o cuestionables. En este contexto se requieren nuevas perspectivas para identificar qué ecosistemas y qué manejos agronómicos representan las fuentes de energía más atractivas desde el punto de vista de los compromisos entre la generación de energía, la producción de alimentos y la preservación del ambiente. Los fuegos que consumen vegetación constituyen una importante vía de pérdida de energía de los ecosistemas. Nuestras estimaciones sugieren que en Argentina, la generación de electricidad utilizando la biomasa de bosques templados secos -que eventualmente se pierde en incendios- podría contribuir de manera significativa al presupuesto energético y proveer una utilización alternativa a estos ambientes.Fil: Verón, Santiago Ramón. Instituto Nacional de Tecnología Agropecuaria. Centro Nacional de Investigaciones Agropecuarias. Centro de Investigaciones de Recursos Naturales. Instituto de Clima y Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Jobbagy Gampel, Esteban Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Matemática Aplicada de San Luis; ArgentinaFil: Di Bella, Carlos Marcelo. Instituto Nacional de Tecnología Agropecuaria. Centro Nacional de Investigaciones Agropecuarias. Centro de Investigaciones de Recursos Naturales. Instituto de Clima y Agua; ArgentinaFil: Paruelo, José. Universidad de Buenos Aires. Facultad de Agronomia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentin

Comparison of different BRDF correction methods to generate daily normalized MODIS 250 m time series

Realizing the full benefits of MODIS' temporal resolution requires, among others, the correction of the directional effect (i.e. the combined impact of the variation of the measurement geometry and of the observed land surface upon the registered radiant flux). While different BRDF methods have been proposed to address this effect, its performance has been evaluated at coarse spatial resolutions making it difficult to assess its applicability to, for example, crop monitoring. Here we test 2 approaches based on two different assumptions: the Classic approach that relies on the hypothesis of stable target and a recent Alternative that is based on the idea that despite reflectance magnitude may change rapidly, the BRDF shape varies slowly in time. Additionally, we segmented the growing season into different numbers of periods for the BRDF correction (a single period along the growing season, 3 periods based in phenology and 9–12 periods of fixed 16-days). The resulting 6 methods were compared over annual crops (wheat, maize and soybean) at 250 m spatial resolution from a site located in the Argentine Pampas. We used MOD and MYD 09 GQ and GA as inputs and compared the corrected daily red and infrared reflectances and the NDVI time series against the filtered benchmark (input time series with quality filters applied) by means of the high frequency variability (i.e. noise). We also tested whether corrected time series were better correlated with soybean PAR interception and biomass. Our results showed that methods' performance was more explained by the number of periods than by the approach (Classic or Alternative). Single period methods decreased noise by 52%, 55% and 4% for red, infrared and NDVI time series. The use of 3 periods improved the correction performance to 63, 64 and 24% for red, infrared and NVDI time series respectively, while the highest reductions (65, 68 and 32% for red, infrared and NVDI) were found with 16-day intervals (9–12 periods) considering a magnitude inversion process. Wheat displayed the lowest noise reduction compared to the other crops. BRDF parameters obtained from different methods were associated to crop structure, suggesting that they have biophysical meaning. The decrease in noise obtained with correction methods was translated into a better assessment of the fraction of intercepted PAR and biomass. These promising results suggest the possibility of extensive field crop monitoring at an unprecedented temporal resolution.Fil: de Abelleyra, Diego. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Recursos Naturales. Instituto de Clima y Agua; ArgentinaFil: Verón, Santiago Ramón. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Recursos Naturales. Instituto de Clima y Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Crop rotations in the Rolling Pampas: Characterization, spatial pattern and its potential controls

One of the most important decisions made by farmers every year involves land allocation to different crops. Accurate information on crop sequences over large areas is a key prerequisite to address social concerns as soybean monoculture, to map good agronomic practices and to assess farmers' adaptive capacity among others. Here we aimed to characterize crop sequences and describe the crop rotation patterns in an area of the Rolling Pampas in Argentina. We performed annual supervised classifications for the 2010/2011 to 2016/2017 growing seasons using high resolution satellite images and in situ data. Classification's accuracies were always higher than 85%. Analysis of crop sequences showed that the most common practice was alternating periods of continuous planting of early soybean with periods where maize and/or wheat were included in the rotation. In addition, during the period analyzed nearly 10% of the study area exhibited continuous soybean monoculture, and 6% of the area showed a strict crop rotation of maize, soybean, and wheat-soybean double crop. Changes in early soybean planted area were significantly associated (p < 0.1) to its previous year's international price, and were probably affected by political economy regulations. The inclusion of maize or wheat in the rotation was more frequently observed at larger cadastral units, while soybean monoculture was more frequent in smaller cadastral units. This suggests that farmers’ capitalization may be associated to different crop rotation decisions through a different long term planning capacity.Fil: de Abelleyra, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Recursos Naturales. Instituto de Clima y Agua; ArgentinaFil: Verón, Santiago Ramón. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía; Argentin

Comparison of X and C band satellite radar images to characterize irrigated agricultural fields

Despite the effect of water content on radar backscattering is well known, isolating the contributions from soil, vegetation, and vegetation superficial water content (wetness) is still challenging. This work aim to characterize the backscatter response over maize crops in the Argentine pampas with differing soil and vegetation water content and wetness considering multipolarimetric X and C band radar. Two images (RADARSAT-2 and TerraSAR-X) were acquired with a 20' time difference over the same study area. Simultaneously with acquisitions, field measurements of superficial soil moisture, dry and wet vegetation biomass and height were performed over irrigated and non irrigated and standing and non emerged crop fields. Soil moisture showed high r2for backscatter and several polarimetric decompositions approaches. On the contrary low correlation was found for maize crop growth parameters. X and C band radar indexes seem to saturate at low maize biomass values but could be associated to superficial crop wetness.Fil: Verón, Santiago Ramón. Instituto Nacional de Tecnología Agropecuaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: de Abelleyra, Diego. Instituto Nacional de Tecnología Agropecuaria; Argentin

Grazing-induced losses of biodiversity affect the transpiration of an arid ecosystem

Degradation processes often lead to species loss.Such losses would impact on ecosystem functioning depending on the extinction order and the functional and structural aspects of species. For the Patagonian arid steppe,we used a simulation model to study the effects of species loss on the rate and variability (i.e. stability) of transpiration as a key attribute of ecosystem functioning.We addressed (1) the differences between the overgrazing extinction order and other potential orders, and (2) the role of biomass abundance, biomass distribution, and functional diversity on the effect of species loss due to overgrazing.We considered a community composed of ten species which were assigned an order of extinction due to overgrazing based on their preference by livestock. We performed four model simulations to test for overgrazing effects through different combinations of species loss, and reductions of biomass and functional diversity. In general, transpiration rate and variability were positively associated to species richness and remained fairly constant until half the species were lost by overgrazing. The extinction order by overgrazing was the most conservative of all possible orders. The amount of biomass was more important than functional diversity in accounting for the impacts of species richness on transpiration. Our results suggest that, to prevent Patagonian steppes from shifting to stable, low-production systems (by overgrazing), maintaining community biomass is more important than preserving species richness or species functional diversity.Fil: Verón, Santiago Ramón. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Métodos Cuantitativos y Sistemas de Información; Argentina. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Paruelo, José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Métodos Cuantitativos y Sistemas de Información; ArgentinaFil: Oesterheld, Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin

Impacts of precipitation and temperature on crop yields in the Pampas

Understanding regional impacts of recent climate trends can help anticipate how further climate change will affect agricultural productivity. We here used panel models to estimate the contribution of growing season precipitation (P), average temperature (T) and diurnal temperature range (DTR) on wheat, maize and soy yield and yield trends between 1971 and 2012 from 33 counties of the Argentine Pampas. A parallel analysis was conducted on a per county basis by adjusting a linear model to the first difference (i.e., subtracting from each value the previous year value) in yield and first difference in weather variables to estimate crop sensitivity to interannual changes in P, T, and DTR. Our results show a relatively small but significant negative impact of climate trends on yield which is consistent with the estimated crop and county specific sensitivity of yield to interannual changes in P, T and DTR and their temporal trends. Median yield loss from climate trends for the 1971−2012 period amounted to 5.4 % of average yields for maize, 5.1 % for wheat, and 2.6 % for soy. Crop yield gains for this time period could have been 15–20 % higher if climate remained without directional changes in the Pampas. On average, crop yield responded more to trends in T and DTR than in P. Translated into economic terms the observed reductions in maize, wheat, and soy yields due to climate trends in the Pampas would equal $1.1 B using 2013 producer prices. These results add to the increasing evidence that climate trends are slowing yield increase.Fil: Verón, Santiago Ramón. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Recursos Naturales. Instituto de Clima y Agua; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Métodos Cuantitativos y Sistemas de Información; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: de Abelleyra, Diego. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Recursos Naturales. Instituto de Clima y Agua; ArgentinaFil: Lobell, David B.. University Of Stanford; Estados Unido

The imprint of humans on landscape patterns and vegetation functioning in the dry subtropics

Dry subtropical regions (DST), originally hosting woodlands and savannas, are subject to contrasting human pressures and land uses and different degrees of water limitation. We quantified how this variable context influences landscape pattern and vegetation functioning, by exploring the associations between three groups of variables describing (i) human pressures (population density, poverty, and market isolation) and climate (water availability),(ii) landscape pattern (woody cover, infrastructure, paddock size, etc.), and (iii) vegetation functioning (magnitude and stability of primary productivity), in regions of Asia, Africa, Australia, and America. We collected data from global socioeconomic databases and remote sensing products for 4525 samples (representing uncultivated and cultivated conditions), located along 35 transects spanning semiarid to subhumid conditions. A Reciprocal Averaging ordination of uncultivated samples revealed a dominant gradient of declining woody cover accompanied by lower and less stable productivity. This gradient, likely capturing increasing vegetation degradation, had a negative relationship with poverty (characterized by infant mortality) and with market isolation (measured by travel time to large cities). With partial overlaps, regions displayed an increasing degradation ranking from Africa to South America, to Australia, to North America, and to Asia. A similar analysis of cultivated samples, showed a dominant gradient of increasing paddock size accompanied by decreasing primary productivity stability, which included all regions except Asia. This gradient was negatively associated with poverty and population density. A unique combination of small paddocks and high infrastructure differentiated Asian cultivated samples. While water availability gradients were related to productivity trends, they were unrelated to landscape pattern. Our comparative approach suggests that, in DST, human pressures have an overwhelming role driving landscape patterns and one shared with water availability shaping vegetation functioning.Fil: Baldi, Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Matemática Aplicada de San Luis; ArgentinaFil: Verón, Santiago Ramón. Instituto Nacional de Tecnología Agropecuaria. Centro Nacional de Investigaciones Agropecuarias. Centro de Investigaciones de Recursos Naturales. Instituto de Clima y Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Jobbagy Gampel, Esteban Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Matemática Aplicada de San Luis; Argentin