Pablo A. Cipriotti

Towards an assessment of multiple ecosystem processes and services via functional traits

Managing ecosystems to ensure the provision of multiple ecosystem services is a key challenge for applied ecology. Functional traits are receiving increasing attention as the main ecological attributes by which different organisms and biological communities influence ecosystem services through their effects on underlying ecosystem processes. Here we synthesize concepts and empirical evidence on linkages between functional traits and ecosystem services across different trophic levels. Most of the 247 studies reviewed considered plants and soil invertebrates, but quantitative trait–service associations have been documented for a range of organisms and ecosystems, illustrating the wide applicability of the trait approach. Within each trophic level, specific processes are affected by a combination of traits while particular key traits are simultaneously involved in the control of multiple processes. These multiple associations between traits and ecosystem processes can help to identify predictable trait–service clusters that depend on several trophic levels, such as clusters of traits of plants and soil organisms that underlie nutrient cycling, herbivory, and fodder and fibre production. We propose that the assessment of trait–service clusters will represent a crucial step in ecosystem service monitoring and in balancing the delivery of multiple, and sometimes conflicting, services in ecosystem management.

Effects of grazing on patch structure in a semi-arid two-phase vegetation mosaic

Abstract Question: What are the grazing effects in the spatial organization and the internal structure of high and low cover patches from a two-phase vegetation mosaic? Location: Patagonian steppe, Argentina. Methods: We mapped vegetation under three different grazing conditions: ungrazed, lightly grazed and heavily grazed. We analysed the spatial patterns of the dominant life forms. Also, in each patch type, we determined density, species composition, richness, diversity, size structure and dead biomass of grasses under different grazing conditions. Results: The vegetation was spatially organized in a two-phase mosaic. High cover patches resulted from the association of grasses and shrubs and low cover patches were represented by scattered tussock grasses on bare ground. This spatial organization was not affected by grazing, but heavy grazing changed the grass species involved in high cover patches and reduced the density and cover of grasses in both patch types. Species richness and diversity in high cover patches decreased under grazing conditions, whereas in low cover patches it remained unchanged. Also, the decrease of palatable grasses was steeper in high cover patches than in low cover patches under grazing conditions. Conclusions: We suggest that although grazing promotes or inhibits particular species, it does not modify the mosaic structure of Patagonian steppe. The fact that the mosaic remained unchanged after 100 years of grazing suggests that grazing does not compromize population processes involved in maintaining patch structure, including seed dispersal, establishment or biotic interactions among life forms. Nomenclature: Correa (1971–1984). Abbreviations: CSR = Complete spatial randomness; INTA = Instituto Nacional de Tecnología Agropecuaria.

Hieracium pilosella invasion in the Tierra del Fuego steppe, Southern Patagonia

Biological invasions have important ecological impacts at both local and global levels, affecting biodiversity, ecosystem functioning, and economic sustainability. The study of invasions requires specific methodological approaches to gain rapid insight into the spatial and temporal dynamics of the system. We studied a recent invasion by the exotic herb Hieracium pilosella L. (Mouse-ear hawkweed, Asteraceae) in the Argentinean portion of the northern part of Tierra del Fuego Island in Southern Patagonia. To assess the extent of this invasion and the related ecological and land use factors, we performed an extensive field sampling at a regional scale and used a spatial pattern approach using geostatistical techniques to build a map of the invasion. Our results showed that the invading species is widely distributed across the entire Fuegian steppe, in general with low cover (<2%) and a particular spatial structure having hot spots (10–70%) related to specific land uses. We found regional-latitudinal and also local-community level variability in the frequency, cover and spatial distribution of the invasive species, each of them associated with particular ecological factors, and no association with regular domestic animal grazing. Region-wide invasion may be accounted for by wind dispersal of the seeds and the latitudinal variability of the precipitation; while local-variability was associated with the susceptibility of different plant communities to invasion. Hot spots were found to be related to massive soil disturbances (e.g., road building, shrub removal, physical impacts of long-term and intense domestic animal use, etc.), probably due to the presence of bare soil favoring colonization by the invading species. Scrublands, lawns and grasslands were more invaded than wetlands, heathlands or salt grasslands. Since the invasion is apparently at initial stages due to the low cover values found, we believe that information about the extent and environmental or management factors involved in this exotic plant’s expansion should be used to design appropriate control and mitigation tools. In this sense, our results point to management actions focused on reducing the presence of hot spots of invasion by means of quick revegetation of bare soil after a massive disturbance event takes place.

Morphological and growth responses to water stress of two sub-populations of Bromus pictus from soils with contrasting water availability

Nosotros estudiamos respuestas morfologicas y de crecimiento a la sequia para dos subpoblaciones de Bromus pictus provenientes de comunidades con suelos de distinta disponibilidad de agua en la estepa patagonica. Luego de un proceso de aclimatizacion comun a ambas subpoblaciones, individuos de cada subpoblacion fueron sometidos a tres niveles de disponibilidad de agua durante 44 dias. Independientemente del nivel de disponibilidad hidrica, la subpoblacion proveniente de la comunidad con mayor agua disponible exhibio una mayor tasa de crecimiento relativa aerea (RGR) y mayor tamano foliar (area y peso) comparado con la subpoblacion proveniente de la comunidad con menor agua disponible. Estos resultados prueban la evolucion esperada de mayores tasas de crecimiento y tamanos de hoja en aquellos ambientes ricos en recursos. La subpoblacion proveniente de la comunidad con menor agua disponible tambien exhibio una mayor tasa de macollaje y un habito de crecimiento mas postrado que la subpoblacion proveniente de la comunidad con mayor agua disponible. Un mayor numero de macollos pequenos puede ser una estrategia util para una rapida respuesta a los pulsos de agua y para distribuir el riesgo la muerte inducida por sequias. Un habito de crecimiento mas postrado puede tambien presentar ventajas tales como reducir el area expuesta al aire seco. Los resultados obtenidos demuestran que la heterogeneidad del suelo puede promover variacion genetica, aunque no permitieron detectar interacciones estadisticamente significativas entre los factores vinculados con las poblaciones y la disponibilidad de agua. La variacion genetica encontrada entre las poblaciones puede ser util para desarrollar programas de mejoramiento e incrementar el potencial evolutivo de una especie nativa para adaptarse a cambios ambientales

Biological limits on nitrogen use for plant photosynthesis: a quantitative revision comparing cultivated and wild species

The relationship between leaf photosynthesis and nitrogen is a critical production function for ecosystem functioning. Cultivated species have been studied in terms of this relationship, focusing on improving nitrogen (N) use, while wild species have been studied to evaluate leaf evolutionary patterns. A comprehensive comparison of cultivated vs wild species for this relevant function is currently lacking. We hypothesize that cultivated species show increased carbon assimilation per unit leaf N area compared with wild species as associated with artificial selection for resource-acquisition traits. We compiled published data on light-saturated photosynthesis (Amax ) and leaf nitrogen (LNarea ) for cultivated and wild species. The relationship between Amax and LNarea was evaluated using a frontier analysis (90th percentile) to benchmark the biological limit of nitrogen use for photosynthesis. Carbon assimilation in relation to leaf N was not consistently higher in cultivated species; out of 14 cultivated species, only wheat, rice, maize and sorghum showed higher ability to use N for photosynthesis compared with wild species. Results indicate that cultivated species have not surpassed the biological limit on nitrogen use observed for wild species. Future increases in photosynthesis based on natural variation need to be assisted by bioengineering of key enzymes to increase crop productivity.

A complex network of interactions controls coexistence and relative abundances in Patagonian grass‐shrub steppes

Fil: Cipriotti, Pablo Ariel. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Parque Centenario. Instituto de Investigaciones Fisiologicas y Ecologicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Metodos Cuantitativos y Sistemas de Informacion; Argentina

Species-specific effects of the invasive Hieracium pilosella in Magellanic steppe grasslands are driven by nitrogen cycle changes

AimsThe principal objective was to evaluate the interference by the invasive species, H. pilosella, on native grassland species at the physiological performance level. We hypothesised that the invasive species is able to alter the nitrogen uptake of native plant species, and can modify community functioning.MethodsThis study was performed under field conditions in the Magellanic Steppe (Argentina). We compared stable isotope signatures, nutrient content and several functional physiological traits in four grassland species with and without H. pilosella interference.ResultsWe found significant interference effects from the invasive species on native species, mostly through changes in nitrogen uptake. The variation in the natural abundance of foliar δ15N suggests that the native plants switched nitrogen sources due to interference with the exotic species. A linear relationship between chlorophyll and proline content that disappears when species are under H. pilosella interference, suggests major changes in the N allocation of native species. Grassland species under interference with exotic species exhibit lower photochemical efficiency and higher water use efficiency. Canonical discriminant analysis evidenced the existence of a different set of functional traits between invasive and native plants, and also among native species with and without H. pilosella interference.ConclusionsOur results support the hypothesis that H. pilosella exerts intense interference with native species through shifting the N sources available for native species, a lower leaf N content, and increasing water stress.

Spatial variability of short-term effect of tillage on soil penetration resistance

ABSTRACT The effect of tillage on soil properties varies within field due to spatial variability of soils. Mapping changes of soil penetration resistance (PR) would be useful to understand and assess tillage practices to alleviate soil compaction. The objectives were to model the short-term effect of tillage on PR and its spatial structure, and to delineate homogeneous zones based on soil response in a Typic Argiudoll previously managed under no-till. A grid sampling for PR and soil water content (SWC) were performed before and after chiselling. Spatial analysis was performed on the effect of tillage on PR data by 10 cm layers and homogeneous zones were delineated by k-means cluster analysis. The effect of tillage was −0.33 MPa in 10–20 and 20–30 cm layer. No differences of PR were found at 0–10 cm. Short range (5–7 m) spatial structure on the horizontal plane was observed in all layers. Only 45% of the field showed a marked effect of tillage on PR. Mapping the effect of tillage on PR would be a useful approach for evaluating the global and local response of soil to tillage, as well as for delineating of areas within field for site-specific tillage practices.

Land surface phenology trends of the Isla Grande de Tierra del Fuego from 15 years MODIS data

El presente estudio corresponde a una primera aproximación de la tendencia de la fenología de la superficie para la Isla Grande de Tierra del Fuego, mediante el análisis de las métricas fenológicas. Inicio, duración y término de la temporada de crecimiento. Se utilizaron compuestos de 16 días correspondientes a índice de vegetación mejorado (EVI) para una serie temporal de 15 años. El análisis de métricas fenológicas obtenidas permite visualizar tendencias espaciales y temporales para el área de estudio.