Land use / land cover change (2000 – 2014) in the Rio de la Plata grasslands : an analysis based on MODIS NDVI time series

Baeza, Santiago. Universidad de la República. Facultad de Agronomía. Departamento de Sistemas Ambientales. Montevideo, Uruguay.Paruelo, José María. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Laboratorio de Análisis Regional y Teledetección (LART) Buenos Aires, Argentina.22Latin America in general and the Rio de la Plata Grasslands (RPG) in particular, are one of the regions in the world with the highest rates of change in land use/land cover (LULC) in recent times. Despite the magnitude of this change process, LULC descriptions in the RPG are far from being complete, even more those that evaluate LULC change through time. In this work we described LULC and its changes over time for the first 14 years of the 21st century and for the entire grassland biome of the Rio de la Plata, one of the most extensive grassland regions in the world. We performed simple but exhaustive classifications at regional level based on vegetation phenology, using extensive LULC field database, time series of MODIS NDVI satellite images and decision trees classifiers, generating an annual map for all RPG. The used technique achieved very good levels of accuracy at the regional (94.3%–95.5%) and sub-regional (78.2%–97.6%) scales, with commission and omission errors generally low (Min = 0.6, Max = 10.3, Median = 5.7, and Min = 0, Max = 41.8, Median = 6.8 for regional and sub regional classification respectively) and evenly distributed, but fails when LULC classifications are generated in years when the climate is very dierent from those used to generate spectral signatures and train decision trees, or when the NDVI time series accumulates large volumes of lost data. Our results show that the RPG are immersed in a strong process of land use change, mainly due to the advance of the agricultural frontier and at the expense of loss of grassland areas. The agricultural area increased 23% in the analyzed period, adding over than 50,000 Km2 of new crops. Most agricultural expansion, and therefore the greatest losses of grassland, concentrates on both sides of Uruguay river (Mesopotamic Pampa and the western portion of Southern and Northern Campos) and the western portion of Inland Pampa. The generated maps open the door for more detailed and spatially explicit modeling of many important aspects of ecosystem functioning, for quantification in the provision of ecosystem services and for more efficient management of natural resources

Disentangling the signal of climatic fluctuations from land use : changes in ecosystem functioning in South American protected areas (1982-2012)

177-189Global environmental change is characterized by changing climate, atmospheric composition and land use. Its impact on ecosystem structure and functioning has been detected throughout the world. While every ecosystem is vulnerable to climate change, the degree of the impact and the magnitude of the ecosystem response are likely to vary. Protected areas of South America provide a ‘laboratory’ to test expectations of climate change effects on ecosystems at a regional scale. By using protected areas we minimized the effects of land use/land cover changes over ecosystem functioning. We analyzed the temporal trends, that is, directional changes, and spatial heterogeneity of both climatic variables and attributes of the seasonal dynamics of the normalized difference vegetation index, that is, a surrogate of vegetation carbon gains derived from satellite information, on 201 protected areas of South America. Increased productivity and higher seasonality, frequently climate driven, is the most common signal across South American biomes but concentrated on those areas located in the tropics and subtropics. In general, arid and semiarid sites responded positively to increases in precipitation and negatively to increases in temperature, while humid ecosystems responded in the opposite way. Our results provide a preliminary basis for predicting which ecosystems will respond more rapidly and strongly to climate change. We also provide support to the fact that protected areas are not static systems as their functioning is changing with different magnitude and in contrasting directions

Disentangling the signal of climatic fluctuations from land use: changes in ecosystem functioning in South American protected areas (1982-2012)

Global environmental change is characterized by changing climate, atmospheric composition and land use. Its impact on ecosystem structure and functioning has been detected throughout the world. While every ecosystem is vulnerable to climate change, the degree of the impact and the magnitude of the ecosystem response are likely to vary. Protected areas of South America provide a ‘laboratory’ to test expectations of climate change effects on ecosystems at a regional scale. By using protected areas we minimized the effects of land use/land cover changes over ecosystem functioning. We analyzed the temporal trends, that is, directional changes, and spatial heterogeneity of both climatic variables and attributes of the seasonal dynamics of the normalized difference vegetation index, that is, a surrogate of vegetation carbon gains derived from satellite information, on 201 protected areas of South America. Increased productivity and higher seasonality, frequently climate driven, is the most common signal across South American biomes but concentrated on those areas located in the tropics and subtropics. In general, arid and semiarid sites responded positively to increases in precipitation and negatively to increases in temperature, while humid ecosystems responded in the opposite way. Our results provide a preliminary basis for predicting which ecosystems will respond more rapidly and strongly to climate change. We also provide support to the fact that protected areas are not static systems as their functioning is changing with different magnitude and in contrasting directions

Native Forest Land Management: Zoning results performed by North argentinean provinces

Argentina cuenta con varias experiencias de ordenamiento territorial (OT) pero hasta el momento no ha sancionado una ley integral. Uno de los principales antecedentes es el ordenamiento territorial de los bosques nativos (OTBN) a través de la ley 26331, sancionada en 2007. El objetivo de este trabajo fue evaluar las experiencias de zonificación en el marco de esta ley de las provincias de Santiago del Estero, Chaco, Formosa y Salta. Se analizó la aplicación de los 10 criterios de sustentabilidad ambiental contemplados por la ley y se compararon cuantitativamente los mapas de zonificación resultantes del proceso de OTBN en las áreas limítrofes. La interpretación de los criterios de sustentabilidad ambiental ha sido dispar entre provincias debido, en parte, a que la información de base utilizada no tiene el mismo nivel de detalle. Salta y Chaco consideraron mayor detalle en estos criterios mientras que Santiago del Estero y Formosa utilizaron información con un nivel de detalle menor. La comparación de la categorización de bosques entre provincias colindantes muestra que la mayor concordancia en las categorías asignadas se observa en los límites de Santiago del Estero y Chaco (58.3%). El grado de concordancia entre los restantes pares de provincias colindantes resultó considerablemente menor:24.76% entre Chaco y Salta; 20.65% entre Formosa y Salta; 10.54% entre Chaco y Formosa y 1.28% entre Salta y Santiago del Estero. Los resultados sugieren que las zonificaciones no han resultado consistentes debido al bajo nivel de concordancia en la categorización de sus bosques.Argentina has several experiences on Land Planning, but so far there is not an integral normative. A key background experience is the land use planning of native forest act (26331) from 2007.The aim of this study was to evaluate the experiences of zoning of the provinces of Santiago del Estero, Chaco, Formosa and Salta in the context of this act. We characterize the way the 10 criteria of environmental sustainability were considered by the four provinces, and we quantitatively compared the zoning maps on the provincial boundaries. The interpretation of the criteria of environmental sustainability differed, in part, because the different provinces did not use the same level of detail. Salta and Chaco considered a higher level of detail on these criteria than the rest. The comparison of the way forests were categorized showed that the highest concordance corresponded to the Santiago del Estero - Chaco border (58.3%). All the other pairs of neighbor provinces presented a significantly lower concordance: 24.76% between Chaco and Salta, 20.65% between Formosa and Salta, 10.54% between Chaco and Formosa and 1.28% between Salta and Santiago del Estero. Our results suggest that the zoning has not been consistent due to the low agreement on the categorization of forests among provinces.Fil: García Collazo, María Agustina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Métodos Cuantitativos y Sistemas de Información; ArgentinaFil: Panizza, Amalia. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Métodos Cuantitativos y Sistemas de Información; 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; Argentin

Environmental and Human Controls of Ecosystem Functional Diversity in Temperate South America

The regional controls of biodiversity patterns have been traditionally evaluated using structural and compositional components at the species level, but evaluation of the functional component at the ecosystem level is still scarce. During the last decades, the role of ecosystem functioning in management and conservation has increased. Our aim was to use satellite-derived Ecosystem Functional Types (EFTs, patches of the land-surface with similar carbon gain dynamics) to characterize the regional patterns of ecosystem functional diversity and to evaluate the environmental and human controls that determine EFT richness across natural and human-modified systems in temperate South America. The EFT identification was based on three descriptors of carbon gain dynamics derived from seasonal curves of the MODIS Enhanced Vegetation Index (EVI): annual mean (surrogate of primary production), seasonal coefficient of variation (indicator of seasonality) and date of maximum EVI (descriptor of phenology). As observed for species richness in the southern hemisphere, water availability, not energy, emerged as the main climatic driver of EFT richness in natural areas of temperate South America. In anthropogenic areas, the role of both water and energy decreased and increasing human intervention increased richness at low levels of human influence, but decreased richness at high levels of human influence

Sistemas agrícolas y silvopastoriles en el Chaco semiárido : impactos sobre la productividad primaria

Baldassini, Pablo. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina.Paruelo, José María. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina.45-62La productividad primaria neta (PPN) se define como la tasa a la cual se acumula biomasa por unidad de área y de tiempo, y se la considera una variable integradora del funcionamiento de los ecosistemas. El desmonte y los cambios en el uso del suelo que afectan gran parte de la región del Chaco Semiárido pueden impactar sobre las ganancias totales de C y su estacionalidad. Trabajos previos en la región utilizan índices espectrales de vegetación como subrogado de la PPN. Sin embargo, arriban a resultados dispares y sólo se circunscriben a lo que sucede con la parte aérea (PPNA), sin considerar los cambios que ocurren en la porción subterránea (PPNS), que suele variar entre tipos fisonómicos de vegetación. Sobre la base del modelo de eficiencia en el uso de la radiación, de información espectral derivada de sensores remotos y de relaciones PPNS/PPN de la bibliografía, el objetivo de este trabajo fue cuantificar el efecto de la transformación en el uso y la cobertura del suelo sobre la PPN, y su variación estacional. En particular, se evaluó el cambio de la PPN en sistemas agrícolas y silvopastoriles con un componente leñoso variable, respecto del bosque original. En general, se observó que los usos del suelo que presentaban una mayor productividad aérea mostraban, al mismo tiempo, los menores niveles de productividad subterránea. El doble cultivo trigo-maíz presentó la mayor PPN total, significativamente superior a la de los sistemas silvopastoriles entre 5 y 25% de cobertura arbórea, y a los cultivos de trigo-soja y soja de primera. Sin embargo, su productividad no varió significativamente de la del bosque, las pasturas megatérmicas y el maíz de primera. Los resultados obtenidos no sólo aportan información sustancial para concluir cuantitativamente en términos de la magnitud del cambio en unidades de materia seca, sino que también permiten establecer un orden o ranking más apropiado de las coberturas y usos del suelo en cuanto a la productividad total

Controls of forage selective defoliation by sheep in arid rangelands

Selective grazing by domestic livestock is a major control of plant community structure anddynamics in drylands. However, grazing impact predictions supporting management decisions are fre-quently based on average biomass consumption, neglecting selectivity. We evaluated the relative impor-tance of grazing pressure, total and each species density, and plant dead biomass proportion as drivers ofselective defoliation by sheep in three dominant native grass species in Patagonian steppes. Species werePoa ligularis,Festuca pallescens,andPappostipa speciosa, whicha prioripresent different preference degree bysheep. The relevance of these drivers for differently preferred species has not been simultaneously studied.We recorded the defoliation frequency and degree of the three species (dependent variables) throughout112field surveys. Besides, we recorded grazing management and vegetation structure descriptors (inde-pendent variables).Poa ligulariswas highly defoliated (90% of plants), and grazing pressure was the lead-ing driver (asymptotic exponential relationship). ForF. pallescens, almost 70% of plants were defoliated,and defoliation non-linearly increased as grazing pressure rose and linearly decreased as both its dead bio-mass proportion andP. ligularisdensity increased. ForP. speciosa, defoliation was low (20% of plants) andlinearly decreased as both its dead biomass proportion and the density of the other two species increased.Grazing pressure played a negligible role in this species. These patterns confirmed thatP. ligularis,F. palles-cens,andP. speciosa,respectively, present high, intermediate, and low preference degree by sheep. In con-clusion, ourfindings suggest that (1) selective defoliation can be satisfactorily predicted as function ofgrazing pressure, species densities, and plant dead biomass proportion; (2) grazing pressure becomes amore relevant driver as species preference rises and its effect on defoliation is markedly non-linear; (3) thedead biomass proportion and the abundance of highly preferred species are the leading factors determin-ing less preferred species defoliation; and (4) grazing pressure management by itself is not enough toreduce the high defoliation of preferred species and increase the defoliation of non-preferred species. Thisknowledge is critical for developing effective management practices to control forage species defoliation inrangelands worldwide where species with different preference by herbivores coexist

Eficiencia en el uso de la radiación y productividad primaria en recursos forrajeros del este de Uruguay

Baeza, Santiago. Facultad de Agronomía. Unidad de Sistemas Ambientales. UdelaR. Montevideo, Uruguay.Paruelo, José María. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Laboratorio de Análisis Regional y Teledetección (LART). Buenos Aires, Argentina.Ayala, Walter. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Treinta y Tres. Entre Ríos, Argentina.48-59La productividad primaria neta aérea (PPNA) es uno de los atributos ecosistémicos más importantes, siendo el principal control de la carga ganadera en pastizales. Tradicionalmente se ha estimado a partir de cortes periódicos de biomasa. La información espectral permite estimar la PPNA a bajo costo y en tiempo real sobre áreas extensas. Para ello se requiere la calibración de modelos que relacionen información espectral con la PPNA estimada mediante cortes de biomasa a campo, cuantificando un factor clave en esta relación: la eficiencia de conversión de la radiación en biomasa (Eficiencia en el Uso de la Radiación: EUR). En este trabajo combinamos datos de PPNA estimada a campo, con datos obtenidos de imágenes de satélite y estaciones meteorológicas, para estimar EUR y generar modelos de estimación de la PPNA en tiempo real en pastizales naturales con y sin siembras en cobertura de leguminosas, en la región de Sierras y Lomadas del Este. La EUR para pastizales naturales fue de 0,24 g MS/MJ (Materia Seca/Mega Joules), mientras que en los sitios intersembrados la EUR fue aproximadamente el doble, dependiendo del sistema analizado. Los modelos para estimar PPNA explicaron el 70 y 58% de la varianza de los datos (p smaller than 0,001), con r2 de predicción de 0,67 y 0,55 (p smaller than 0,001), para pastizales naturales e intersiembras respectivamente

The law is spider’s web: an assessment of illegal deforestation in the Argentine Dry Chaco ten years after the enactment of the “Forest Law”

Deforestation control is one of the major challenges worldwide. The aim of this study was to analyse deforestation under the Forest Law in the Argentine Dry Chaco ecoregion a decade after its enactment and to assess compliance with forest protection standards in this region. For this purpose, we overlapped the provincial land zoning maps with an annual plot level deforestation database and, for some provinces, with the rural cadastral cartography. Deforestation exceeding the values allowed by the Forest Law and the provincial zonings during this period totalized 722,782 ha (28% of the total deforested area in this period), of which 59,732 ha were deforested in high conservation value areas, 644,396 ha in medium conservation value areas and 18,654 ha in low conservation value areas. While Santiago del Estero was the province with the highest deforested area in medium conservation value areas, Córdoba was the province with the highest deforested area in high conservation value areas. Our results are an important step towards identifying discrepancies between the legal objectives and the observed results and represent an input to think about solutions to improve the environmental governance of the region