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We report state-and-transition models for Uruguayan grasslands built on a methodological approach that objectively defined states/phases associated, a priori, with rangeland management. Such approach was based on randomly sampled areas corresponding to mapped grassland communities. Each sampled area matched a MODIS pixel. Vegetation structural indicators were recorded in every pixel. After a multivariate analysis, field observations were grouped according to similarities in terms of structure, and different “states” and “phases” were identified. Ecosystem functioning and the supply of regulating ecosystem services were estimated for each grassland state/phase using the normalized difference vegetation index derived from the MODIS sensor. Finally, workshops were held in order to detect local stakeholders’ perceptions and discuss the management practices to promote the desired transitions among phases. Results were presented for two vegetation units of the Basaltic “Cuesta” region. The “inductive approach” applied led to not only the description of “states” but also the identification of more subtle changes in vegetation ("phases"). Our approach minimized biases due to personal experience, as well as differences derived from using different observation protocols. The two vegetation units presented an internal heterogeneity associated with changes in basal stratum height, total cover, stratification, frequency of decreasing species due to grazing, and proportion of plant life forms. The ecosystem functioning descriptors of each phase responded to extreme climatic events differently. On the basis of stakeholder’s opinions and experiences, stocking rate, sheep/cattle ratio, and grazing method were the main management practices promoting the transition among phases.

The temporal trend of aboveground net primary production (ANPP) is frequently used to estimate the effect of humans on ecosystems. In water-limited ecosystems, like most grazing areas in the world, the effect of humans act upon ANPP in combination with environmental variations. Our main objective was to quantify long-term (1981-2012) changes of ANPP and discriminate the causes of these changes between environmental and human at a subcontinental scale, across vast areas of Patagonia. We estimated ANPP through a radiative model based on remote sensing data. Then, we evaluated the relation between ANPP and environmental interannual variations of two hierarchically related factors: El Nino Southern Oscillation (ENSO) through the Southern Oscillation Index (SOI), and precipitation. We described the effect of humans through the shape of the temporal trends of the residuals (RESTREND) of the environmental model and quantified human relative impact through the RESTREND: ANPP trend ratio. ANPP interannual variation was significantly explained by ENSO (through SOI) and precipitation in 65% of the study area. The SOI had a positive association with annual precipitation. The association between ANPP and annual precipitation was positive. RESTREND analysis was statistically significant in 92% of the area where the tested environmental model worked, representing 60% of the study area, and it was mostly negative. However, its magnitude, revealed through the RESTREND: ANPP trend ratio, was relatively mild. Our analysis revealed that most of ANPP trends were associated with climate and that even when human density is low, its incidence seems to be mainly negative.

Land use changes are occurring with unprecedented magnitude and intensity, imposing global impacts on ecosystem services (ES) and biodiversity. While the impacts of land use changes are increasingly recognized, understanding how landscape connectivity is related to ecosystem functioning is lacking. In the Argentinian Dry Chaco, deforestation increased forest fragmentation but strips of native forest (linear remnants) were usually left after clearings. Although the number of ecological studies on forest strips has increased, their contribution to forest connectivity and functioning has not been assessed. We evaluated the contribution of forest strips to forest connectivity and estimated its effect on forests' functioning considering low, moderate, and high species' dispersal abilities in our estimation. The effects of forest strip connectivity contribution to the forests' Ecosystem Services Supply Index (Forests' ESSI) was also analyzed. Forest strips contributed on average 6% and up to 40% to forest connectivity for moderate dispersal abilities, while low and high dispersals presented low values in almost all cases. The connectivity contribution was highest (between 15 and 40%) and variable for moderate dispersal abilities in landscapes with between 25 and 35% of forest cover. High connectivity contribution was generally achieved for low and moderate dispersals when forest strips conformed a network among forest patches. Forest strip connectivity significantly increased the forests' ESSI (between 1.3 and 2.4% per unit of connectivity contribution) and its effect was higher in comparison to forest amount and fragmentation. This study provides insights for planning the location of forest strips and forest remnants in agricultural landscapes, thus increasing forest connectivity for enhancing ecosystem functioning.

The lack of an organizing conceptual framework to address ecosystem changes reduces our capacity to distinguish biophysical from direct human impacts on grassland dynamics. This is particularly important for subhumid temperate grasslands, one of the world’s most threatened biomes. We identified and mapped 4 functional syndromes of grassland change at the wettest end of its worldwide distribution, the Campos in Uruguay. Syndromes were defined by differences in precipitation use efficiency (PUE, ANPP/precipitation), and in precipitation marginal response (PMR, slope of the linear regression between ANPP and precipitation) between two periods (1981–1995 and 2001–2011). Temporal trends in aboveground net primary production (ANPP, obtained by splicing two sources of NDVI, LTDR and MOD13Q1) were also characterized. To rule out the effect of precipitation we analyzed temporal trends of the residuals from the relationship between ANPP and annual precipitation (RESTRENDS). Functional syndromes associated with increases in seasonality or in the abundance of annual vegetation (ΔPMR > 0, ΔPUE 5000 km2) were the most abundant. ANPP trends were significantly negative in 3.7% of the area (2475 km2) and only positive in 0.3%. However, RESTRENDS were significant in 11% of the area (>7700 km2), and mostly negative (in ∼7200 km2). Most of these negative trends and residual trends were associated to seasonality increase and vegetation loss syndromes. These patterns were consistent with observed changes in the region. We highlight that this conceptual framework is suitable for describing patterns of change and potential causes. Moreover, it provides policymakers with a novel tool to guide management and conservation policies, pointing to sites where intervention (i.e. conservation, restoration) is needed.

Latin America, and particularly, the Rio de la Plata Grasslands (RPG), are one of the regions with the highest rates of land use change worldwide. These changes drastically alter ecosystems energy flows, affecting biodiversity, atmospheric composition, and the ecosystem capacity to provide services. In this work we evaluated the impact of these changes on Net Primary Production (NPP), one of the most important and integrative ecosystem attributes, through the calculation of Human Appropriation of NPP (HANPP), a very complete indicator of human impact on ecosystems. Our results provide a comprehensive and fine grained description of HANPP patterns over an entire biogeographycal region for two periods that encompass a strong agricultural intensification process. We used medium resolution land use maps and NPP estimates from sub-national level agricultural statistics and remotely sensed data modeling. Results show that the human impact on the energy flow in RPG ecosystems reached very high levels compared to other regions of the world. The average appropriation of was 42% of the potential vegetation NPP in 2001/2002 and it increased 4.5% during the last years due to an intense land use changes. Most of the HANPP was explained by harvest rather than by land use changes, mainly in the last period due to crops yield increase and the expansion of double crop system as a common agronomic practice. High HANPP values found were associated to a set of environmental impacts that affect ecosystems sustainability and their ability to provide ecosystem services.

Temperate subhumid grasslands extend in the eastern part of South America. This region represents one of the most diverse, largest and less transformed grassland areas in the world. The grasslands occupy the vast and continuous plains of central-eastern Argentina, Uruguay and southern Brazil that surround the Rio de la Plata estuary. For this reason, they are referred to as the Rio de la Plata grasslands. These grasslands, despite its apparent physiognomic homogeneity, hold high diversity of species, having grasses as the dominant life form except for few scattered shrubs and trees, and show a year-round photosynthetic activity. In this article we describe structural and functional characteristics of the vegetation of the Rio de la Plata grasslands. We give an overview on biogeography, ecosystem functioning and services, human appropriation of primary production, disturbances, land use change, biological invasions and conservation status.

Fil: Baeza, Santiago. Universidad de la República. Facultad de Agronomía. Departamento de Sistemas Ambientales. Montevideo, Uruguay. Fil: 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. Latin 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. grafs., tbls., mapas

Semiarid forests are worldwide threatened by land use changes, particularly agriculture. However, in some cases, due to particular economic or social processes, agriculture ends and forests may or may not recover to their original state. Using different databases and satellite images integrated into a geographical information system, we located in the central region of the semiarid Chaco forests of Argentina adjacent land use patches of secondary forest (SF), remnant forest (RF) and crops (CP). Using a chronosequence approach, we evaluated changes in the fraction of the photosynthetic active radiation absorbed by the vegetation (FAPAR) between SF and RF and CP, using the enhanced vegetation index (EVI). We evaluated both intra and inter-annual changes in EVI mean (EVImean), EVI maximum (EVImax), EVI minimum (EVImin), and EVI relative range (EVIrr) as descriptors of FAPAR dynamics and analyzed their changes through time (2000 to 2010) and their relation to rainfall. Secondary forests showed higher seasonality and higher EVImean values than RF, but differences disappeared as time since agricultural abandonment increased, suggesting that SF recover their functioning (when compared to RF) after 10 to 15 years. Our results suggest that Chaco's SF have intermediate seasonal patterns in-between RF and CP, as expected by successional theory, and that FAPAR interception by RF appears to be dependent on previous year's precipitation. We found that, although all land uses showed similar precipitation use efficiency (PUE), SF and cropland's productivity were less stable across the years and showed faster increases or decreases compared to RF, depending on precipitation (higher precipitation marginal response- PMR). Our results suggest that at least some aspects of ecosystem functioning can be restored after agricultural abandonment. Future research that combines floristic and structural changes is necessary to fully understand secondary forests regrowth process after agricultural abandonment in the Chaco region.

Aboveground net primary production (ANPP) is a variable that integrates many aspects of ecosystem functioning. Variability in ANPP is a key control for carbon input and accumulation in grasslands systems. In this study, we analyzed the spatial and temporal variability of ANPP of Uruguayan grasslands during 2000–2010. We used enhanced vegetation index (EVI) data provided by the MODIS-Terra sensor to estimate ANPP according to Monteith’s (1972) model as the product of total incident photosynthetically active radiation, the fraction of the radiation absorbed by green vegetation, and the radiation use efficiency. Results showed that ANPP varied spatially among geomorphological units, increasing from the north and midwest of Uruguay

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. Fil: Dieguez, Hernan Dario. 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 Fil: 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; Argentina. Universidad de la República; Uruguay

Regular economic activity takes into account ecosystem goods and services that are exchanged for money in the market (e.g. food, fibre, water) but normally ignores more intangible ones left away from market transactions (e.g. soil protection, climate regulation, disturbance control, habitat provision), even in cases when they become irreversibly impaired. However, because of the increasing pressure brought by the public opinion, the attempts to assign an economic, yet volatile, valuation to ecosystems assets has multiplied in recent years, and policy communities are increasingly compelled to incorporate them into land use planning initiatives. Based on contributions to this special issue, we discuss how the perspective of ecosystem services can contribute to develop sound land-use policies and planning actions. Beyond valuation, several practical implications emerge from the contributions. A myriad of potential tradeoffs must be analyzed because since the provision of some services can be accompanied by the emergence of unexpected dis-services. For example, carbon accumulation based on increasing net primary production rates may simultaneously cut water yields and, hence, water provision. Various existing mechanisms ranging from state-controlled to market-controlled for rewarding the provision of ecosystem services are analyzed and discussed in terms of their capacity to connect nature to land-use planning.

Desertification threatens 70% of all dry lands worldwide by diminishing the provision of economic and ecosystem services. However, since long-term vegetation dynamics of semiarid ecosystems are difficult to study, the opportunities to evaluate desertification and degradation properly are limited. In this study, we tailored, calibrated and tested a spatially-explicit simulation model (DINVEG) to describe the long-term dynamics of dominant grass and shrub species in the semiarid Patagonian steppe. We used inverse techniques to identify parameterizations that yield model outputs in agreement with detailed field data, and we performed sensitivity analyses to reveal the main drivers of long-term vegetation dynamics. Whereas many parameterizations (10–45%) matched single field observations (e.g. grass and shrub cover, species-specific density, aboveground net primary production [ANPP]), only a few parameterizations (0.05%) yielded simultaneous match of all field observations. Sensitivity analysis pointed to demographic constraints for shrubs and grasses in the emergence and recruitment phase, respectively, which contributed to balanced shrub-grass abundances in the long run. Vegetation dynamics of simulations that matched all field observations were characterized by a stochastic equilibrium. The soil water content in the top layer (0–10 cm) during the emergence period was the strongest predictor of shrub densities and population growth rates and of growth rates of grasses. Grasses controlled the shrub demography because of the resource overlap of grasses with juvenile shrubs (i.e. water content in the top layer). In agreement with field observations, ecosystem function buffered the strong variability in precipitation (a simulated CV in ANPP of 16% vs CV in precipitation of 33%). Our results show that seedling emergence and recruitment are critical processes for long-term vegetation dynamics in this steppe. The methods presented here could be widely applied when data for direct parameterization of individual-based models are lacking, but data corresponding to model outputs are available. Our modeling methodology can reduce the need for long-term data sets when answering questions regarding community dynamics.

Questions: (1) Can above-ground net primary production (ANPP) of Patagonian meadows be estimated from remote sensing? (2) How does ANPP of Patagonian meadows change in space and time? Location: Northwestern Patagonia, meadows embedded in a steppe matrix (39–43°S, 70–72oW; area: 85 000 km 2 ). Methods: For the first question, we contrasted field ANPP measurements with MODIS high-spatial resolution (pixel size: 0.0625 km 2 ) data and developed a model that estimates radiation use efficiency. For the second question, we applied the model to a 6-year MODIS record for 14 meadows whose physiognomic heterogeneity was known from previous work. Results: Up to 77% of the field-based ANPP variation was accounted for by the absorbed photosynthetic radiation, based on a linear transformation of the normalized difference vegetation index derived from MODIS data. Mean radiation use efficiency was 0.54 g dry matter MJ � 1 . ANPP ranged between 610 and 1060 g m � 2 year � 1 , which represents three to 5.3 times the ANPP of the surrounding arid and semi-arid steppes. The inter-annual coefficient of variation of ANPP was 10%, which is higher than other systems of similar productivity, but much lower than the surrounding steppes (33%). At the level of management units (paddock), ANPP spatial variations were mainly related to the proportion of Prairies, a proxy for low topographic position in the landscape, and longitude, a proxy for precipitation. ANPP inter-annual variation was most related to latitude, a proxy for temperature. Conclusion: The model developed and tested can be used to infer ANPP from remote sensing data at a spatial resolution that allows one to detect variability within meadows and management units. Variations at both the physiognomic unit and paddock level were associated with geographic patterns and topography. Meadows were three to five times more productive and less fluctuating than nearby steppes. When compared with other ecosystems, their productivity was high, but more variable inter-annually, likely due to exceptionally high variability of precipitation in Patagonia.

The homogeneous topography of Argentina's flooding pampas conceals a substantial amount of spatial and temporal ecosystem heterogeneity. Differences in soils, grassland botanical composition and plant growth regimes that occur down to individual paddocks influence livestock grazing patterns and, predictably, affect the productivity of cattle ranches in the region. Over 40 years of ecological research have greatly improved understanding of the structural and functional heterogeneity of this ecosystem. This better understanding has led to the development of grazing management strategies that help ranchers optimize secondary production by achieving a more efficient use of vegetation. As a result, cattle ranches are rapidly increasing profitability by integrating grass-fed yearling finishing programmes with the traditional cow-calf operations of the region. Fil: Cid, Maria Silvia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce; Argentina Fil: Fernández Grecco, R. C.. Instituto Nacional de Tecnología Agropecuaria; Argentina Fil: Oesterheld, Martin. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Paruelo, José. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Cibils, A. F.. New Mexico State University; Estados Unidos Fil: Brizuela, M. A.. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina

Grasslands are one of the most modified biomes on Earth. Land use changes had a large impact on carbon (C) stocks of grasslands. Understanding the impact of land use/land cover changes on C stocks and fluxes is critical to evaluate the potential of rangeland ecosystem as C sinks. In this article we analyze C stocks and fluxes across the environmental gradients of one of the most extensive temperate rangeland areas: the Rio de la Plata Grasslands (RPG) in South America. The analysis summarizes information provided by field studies, remote sensing estimates, and modeling exercises. Average estimates of aboveground net primary production (ANPP) ranged from 240 to 316 g C ? m 22 ? yr 21 . Estimates of belowground NPP (BNPP) were more variable than ANPP and ranged from 264 to 568 g C ? m 22 ? yr 21 . Total Carbon ranged from 5 004 to 15 008 g C ? m 22 . Plant biomass contribution to Total Carbon averaged 13% and varied from 9.5% to 27% among sites. The largest plant C stock corresponded to belowground biomass. Aboveground green biomass represented less than 7% of the plant C. Soil organic carbon (SOC) was concentrated in the slow and passive compartments of the organic matter. Active soil pool represented only 6.7% of the SOC. The understanding of C dynamics and stocks in the RPG grasslands is still partial and incomplete. Field estimates of ANPP and BNPP are scarce, and they are not based on a common measurement protocol. Remotely sensed techniques have the potential to generate a coherent and spatially explicit database on ANPP. However, more work is needed to improve estimates of the spatial and temporal variability of radiation use efficiency. The absence of a flux tower network restricts the ability to track seasonal changes in C uptake and to understand fine-scale controls of C dynamics. Resumen

Temporal variation of aboveground net primary production (ANPP) of arid ecosystems has been associated with precipitation regimes with different results. The objective of this paper was to characterize the relationship between interannual variation of annual and seasonal Normalized Difference Vegetation Index (NDVI), as a surrogate for ANPP, and precipitation in the steppes of Northern Patagonia. In 11 sites encompassing a wide range of conditions and vegetation physiognomies, we studied a 20-year monthly data set of NDVI and precipitation. We took into account the precipitation of current, as well as previous periods of variable length. Interannual variation of annual NDVI was little correlated with annual precipitation, either current or previous. In contrast, it was highly and widely correlated with precipitation accumulated during a few months of the previous growing season. Interannual variation of seasonal NDVI was little correlated with current seasonal precipitation. In contrast, it was significantly correlated with precipitation accumulated during previous periods of variable length according to the season and site under consideration. NDVI was more tightly coupled with precipitation in drier ecosystems. Lags of response between NDVI and precipitation provide an opportunity for forecasting ANPP and suggest even longer lags between climatic variation and herbivore performance.

We built a grid-based spatial explicit stochastic model that simulates grazing events and basic processes like seedling establishment, growth or mortality of the dominant species in the grass steppes of Patagonia. After evaluating the model with field data, we performed simulation experiments aimed to explore the interaction of precipitation and grazing regimes on vegetation dynamics. Grazing generated a reduction in tussock density which results in a decline in aboveground net primary production (ANPP). Both response variables presented a non-linear behavior including high temporal variability and delay effects, which may prolong for decades. There was a clear threshold in the response of the variables to stock density, though changes become evident only when a highly selective grazing scenario was used. Under high stock density conditions, precipitation use efficiency (PUE) was 82% lower than the values for non-grazed runs. The inter-annual variability of precipitation was more important than the grazing regime in explaining differences in tussock density. Simulation results highlight important issues regarding rangeland management: grazing regime might be as important as stocking density as a degradation agent, temporal lags might obscure degradation processes for decades, the definition of monitoring variables need to consider their response time constants. Fil: 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 Fil: Pütz, S.. UFZ Centre for Environmental Research Leipzig-Halle; Alemania Fil: Weber, G.. UFZ Centre for Environmental Research Leipzig-Halle; Alemania Fil: Bertiller, Monica Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Golluscio, Rodolfo. 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 Fil: Aguiar, Martin Roberto. 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 Fil: Wiegand, T.. UFZ Centre for Environmental Research Leipzig-Halle; Alemania

Our knowledge about the functional foundations of ecosystem service (ES) provision is still limited and more research is needed to elucidate key functional mechanisms. Using a simplified eco-hydrological scheme, in this work we analyzed how land-use decisions modify the partition of some essential regulatory ES by altering basic relationships between biomass stocks and water flows. A comprehensive meta-analysis and review was conducted based on global, regional and local data from peer-reviewed publications. We analyzed five datasets comprising 1348 studies and 3948 records on precipitation (PPT), aboveground biomass (AGB), AGB change, evapotranspiration (ET), water yield (WY), WY change, runoff (R) and infiltration (I). The conceptual framework was focused on ES that are associated with the ecological functions (e.g., intermediate ES) of ET, WY, R and I. ES included soil protection, carbon sequestration, local climate regulation, water-flow regulation and water recharge. To address the problem of data normality, the analysis included both parametric and non-parametric regression analysis. Results demonstrate that PPT is a first-order biophysical factor that controls ES release at the broader scales. At decreasing scales, ES are partitioned as result of PPT interactions with other biophysical and anthropogenic factors. At intermediate scales, land-use change interacts with PPT modifying ES partition as it the case of afforestation in dry regions, where ET and climate regulation may be enhanced at the expense of R and water-flow regulation. At smaller scales, site-specific conditions such as topography interact with PPT and AGB displaying different ES partition formats. The probable implications of future land-use and climate change on some key ES production and partition are discussed. Fil: Viglizzo, Ernesto Francisco. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina. Universidad Nacional de La Pampa; Argentina Fil: Jobbagy Gampel, Esteban Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentina Fil: Ricard, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina Fil: 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

Carbon gains are a key aspect of ecosystem functioning since they represent the energy available for upper trophic levels. Carbon gains (or primary production) are strongly correlated with other ecosystem attributes such as secondary production and they are also the support for the provision of many ecosystem services. Given the documented dependency of primary production on precipitation, we expect that altered precipitation regimes, such as those projected by climate models, will have a significant impact on carbon gains. Land use and land cover changes are also expected to have a significant impact on the dynamics of carbon gains. We generated a spectral database of the fraction of photosynthetically active radiation intercepted by vegetation (fPAR), in order to study long-term trends (i.e., decades) in carbon gains and its spatial and temporal relationships with precipitation and land cover patterns in Uruguay, which is part of the Rio de la Plata Grasslands, one of the largest temperate grasslands biome of the world. We found that carbon gains of native forests and grassland afforestation exhibited the strongest positive spatial response to precipitation, whereas crops and rangelands the weakest. In addition, we found that the temporal response of carbon gains to precipitation was strong and positive for all land uses. Although there were not clear trends in precipitation, we found strong negative trends in carbon gains through time, particularly in rangelands of the "Northern Campos" of Uruguay, where these trends represent a decrease between 10% and 25% of the annual aboveground net primary production. On the other hand, positive trends in carbon gains through time were associated to grassland afforestation and native forests. Therefore, during the period analyzed, land cover had a stronger influence on the observed trends in carbon gains than precipitation. These patterns emerged as a consequence of the interaction among precipitation, temperature, edaphic factors and management. Present trends in the controlling factors of C gains would exacerbate the observed patterns with serious consequences for the provision of ecosystems services. Fil: Texeira González, Marcos Alexis. 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 Fil: Oyarzabal, Mariano. 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 Fil: Piñeiro, Gervasio. 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 Fil: Baeza, Santiago. Universidad de la República; Uruguay Fil: 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 la República; Uruguay

The large global extension of arid and semi-arid regions together with their widespread degradation give these areas a high potential to sequester carbon. We explored the possibilities of semi-arid ecosystems to sequester carbon by means of rangeland exclusion and afforestation with Pinus ponderosa in NW Patagonia (Argentina). We sampled all pools where organic carbon accumulates in a network of five trios of adjacent grazed, non-grazed and afforested stands (age: 12–25 years, density 605–1052 trees ha −1 ). After 15 years since trees were planted, afforestation added ∼50% more C to the initial ecosystem carbon pool, with annual sequestration rate ranging 0.5–3.3 Mg C ha −1 year −1 . Carbon gains in afforested stands were higher above than below-ground (150% vs. 32%). Root biomass differences (374% more in afforested vs. grazed stands, p = 0.0 0 1 1 ) explained below-ground carbon contrasts whereas soil organic carbon showed no differences with afforestation. By contrast, grazing exclosures did not result in significant changes in the total carbon storage in comparison with the adjacent grazed stands ( p = 0.4 2 ) suggesting a slow ecosystem recovery in the time frame of this study (∼15 years of exclusion). Nevertheless, higher litter amount was found in the former (+53%, p = 0.0 7 ). Neither, soil organic carbon nor root carbon showed significant differences between grazed and non-grazed conditions. Considering that more than 1.1 millions of hectares of the studied ecosystems are highly degraded and suitable for tree planting, afforesting this area could result in a carbon sequestration rate of 1.7 Tg C year −1 , almost 6% of the current fossil fuel emissions of Argentina; however environmental consequences which could emerge from this deep land use shift must be taken into account when afforestation program are being designed.

Identifying the conditions and mechanisms that control ecosystem processes, such as net primary production, is a central goal of ecosystem ecology. Ideas have ranged from single limiting-resource theories to colimitation by nutrients and climate, to simulation models with edaphic, climatic, and competitive controls. Although some investigators have begun to consider the influence of land-use practices, especially cropping, few studies have quantified the impact of cropping at large scales relative to other known controls over ecosystem processes. We used a 9-year record of productivity, biomass seasonality, climate, weather, soil conditions, and cropping in the US Great Plains to quantify the controls over spatial and temporal patterns of net primary production and to estimate sensitivity to specific driving variables. We considered climate, soil conditions, and long-term average cropping as controls over spatial patterns, while weather and interannual cropping variations were used as controls over temporal variability. We found that variation in primary production is primarily spatial, whereas variation in seasonality is more evenly split between spatial and temporal components. Our statistical (multiple linear regression) models explained more of the variation in the amount of primary production than in its seasonality, and more of the spatial than the temporal patterns. Our results indicate that although climate is the most important variable for explaining spatial patterns, cropping explains a substantial amount of the residual variability. Soil texture and depth contributed very little to our models of spatial variability. Weather and cropping deviation both made modest contributions to the models of temporal variability. These results suggest that the controls over seasonality and temporal variation are not well understood. Our sensitivity analysis indicates that production is more sensitive to climate than to weather and that it is very sensitive to cropping intensity. In addition to identifying potential gaps in out knowledge, these results provide insight into the probable long- and short-term ecosystem response to changes in climate, weather, and cropping.

Ecosystem and soil scientists frequently use whole soil carbon:nitrogen (C:N) ratios to estimate the rate of N mineralization from decomposition of soil organic matter (SOM). However, SOM is actually composed of several pools and ignoring this heterogeneity leads to incorrect estimations since the smaller pools, which are usually the most active, can be masked by the larger pools. In this paper, we add new evidence against the use of C:N ratios of the whole soil: we show that a disturbance can decrease the whole-soil C:N ratio and yet increase C:N ratios of all SOM pools. This curious numerical response, known as Simpson’s paradox, casts doubt on the meaning of frequently reported whole-soil C:N changes following a disturbance, and challenges the N mineralization estimates derived from whole-soil C:N ratio or single-pool modeling approaches. Whole-soil C:N ratio may not only hide features of the labile SOM pool, but also obscure changes of the large recalcitrant SOM pools which determine long-term N availability.

Aim To e xamine the geographical patterns of the interception of photosynthetically active radiation by vegetation and to describe its spatial heterogeneity through the definition of ecosystem functional types (EFTs) based on the annual dynamics of the Normalized Difference Vegetation Index (NDVI), a spectral index related to carbon gains. Location The Iberian Peninsula. Methods EFTs were derived from three attributes of the NDVI obtained from NOAA/AVHRR sensors: the annual integral (NDVI-I), as a surrogate of primary production, an integrative indicator of ecosystem functioning; and the intra-annual relative range (RREL) and month of maximum NDVI (MMAX), which represent key features of seasonality. Results NDVI-I decreased south-eastwards. The highest values were observed in the Eurosiberian Region and in the highest Mediterranean ranges. Low values occurred in inner plains, river basins and in the southeast. The Eurosiberian Region and Mediterranean mountains presented the lowest RREL, while Eurosiberian peaks, river basins, inner-agricultural plains, wetlands and the southeastern part of Iberia presented the highest. Eurosiberian ecosystems showed a summer maximum of NDVI, as did high mountains, wetlands and irrigated areas in the Mediterranean Region. Mediterranean mountains had autumn‐early-winter maxima, while semi-arid zones, river basins and continental plains had spring maxima. Based on the behaviour in the functional traits, 49 EFTs were defined. Main conclusions The classification, based on only the NDVI dynamics, represents the spatial heterogeneity in ecosystem functioning by means of the interception of radiation by vegetation in the Iberian Peninsula. The patterns of the NDVI attributes may be used as a reference in evaluating the impacts of environmental changes. Iberia had a high spatial variability: except for biophysically impossible combinations (high NDVI-I and high seasonality), almost any pattern of seasonal dynamics of radiation interception was represented in the Peninsula. The approach used to define EFTs opens the possibility of monitoring and comparing ecosystem functioning through time.

Land use has a large impact on ecosystem functioning, though evidences of these impacts at the regional scale are scarce. The objective of this paper was to analyze the impacts of agricultural land use on ecosystem functioning (radiation interception and carbon uptake) in temperate areas of North and South America. From land cover maps generated using high-resolution satellite images we selected sites dominated by row crops (RC), small grain crops (SG), pastures (PA), and rangelands (RA) in the Central Plains of USA and the Pampas of Argentina. These two regions share climatic characteristics and the agricultural conditions (crop types) are also very similar. Both areas were originally dominated by temperate grasslands. In these sites we extracted the temporal series of the normalized difference vegetation index (NDVI) from the NOAA satellites for the period 1989–1998 and calculated the mean seasonal NDVI curve for each site. Additionally, we calculated the mean annual NDVI, the maximum NDVI, the date of the year when the max NDVI was recorded and the interannual variability of these three attributes. We compared the mean values of each NDVI-derived attribute between land cover types and between continents. The NDVI seasonal patterns for each land cover type were roughly similar between the Central Plains and the Pampas during the growing season. The largest differences were observed during the winter and spring, when the NDVI of all land cover types in the Central Plains remained at lower values than in the Pampas. This was probably caused by the high annual thermal amplitude in the Central Plains that results in a much more restricted growing season. As a result of these differences in the shape of the NDVI curve, the mean annual NDVI in the Central Plains was lower than in the Pampas for all land cover types but the maximum NDVI did not differ importantly. In both regions, row crops delayed the date of the NDVI peak, small grain crops advanced it and pastures did not change it importantly, compared with rangelands. The interannual variability of the NDVI attributes was higher for small grains than for row crops in both regions. However, small grains crops were consistently more variable between years in the Central Plains than in the Pampas. The opposite occurred with pastures and rangelands, which were more variable in the Pampas than in the Central Plains. This paper confirms and generalizes previous findings that showed important imprints of land use on ecosystem functioning in temperate ecosystems. Our results support the idea that the changes in land cover that have occurred in the Central Plains and the Pampas leaded to similar changes in the way that ecosystems absorb solar radiation and in the patterns of carbon uptake.

Aims 1. To characterize ecosystem functioning by focusing on above-ground net primary production (ANPP), and 2. to relate the spatial heterogeneity of both functional and structural attributes of vegetation to environmental factors and landscape structure. We discuss the relationship between vegetation structure and functioning found in Patagonia in terms of the capabilities of remote sensing techniques to monitor and assess desertification. Location Western portion of the Patagonian steppes in Argentina (39 ° 30 ′ S to 45 ° 27 ′ S). Methods We used remotely-sensed data from Landsat TM and AVHRR / NOAA sensors to characterize vegetation structure (physiognomic units) and ecosystem functioning (ANPP and its seasonal and interannual variation). We combined the satellite information with floristic releves and field estimates of ANPP. We built an empirical relationship between the Landsat TM-derived normalized difference vegetation index (NDVI) and field ANPP. Using stepwise regressions we explored the relationship between ANPP and both environmental variables (precipitation and temperature surrogates) and structural attributes of the landscape (proportion and diversity of different physiognomic classes (PCs)). Results PCs were quite heterogeneous in floristic terms, probably reflecting degradation processes. Regional estimates of ANPP showed differences of one order of magnitude among physiognomic classes. Fifty percent of the spatial variance in ANPP was accounted for by longitude, reflecting the dependency of ANPP on precipitation. The proportion of prairies and semideserts, latitude and, to a lesser extent, the number of PCs within an 8 × 8 km cell accounted for an additional 33% of the ANPP variability. ANPP spatial heterogeneity (calculated from Landsat TM data) within an 8 × 8 km cell was positively associated with the mean AVHRR / NOAA NDVI and with the diversity of physiognomic classes. Main conclusions Our results suggest that the spatial and temporal patterns of ecosystem functioning described from ANPP result not only from water availability and thermal conditions but also from landscape structure (proportion and diversity of different PCs). The structural classification performed using remotely-sensed data captured the spatial variability in physiognomy. Such capability will allow the use of spectral classifications to monitor desertification.

Land-cover change associated with agriculture has had an enormous effect on the structure and functioning of temperate ecosystems. However, the empirical evidence for the impact of land use on ecosystem functioning at the regional scale is scarce. Most of our knowledge on land-use impact has been derived from simulation studies or from small plot experiments. In this article we studied the effects of land use on (i) the seasonal dynamics and (ii) the interannual variability of the Normalized Difference Vegetation Index (NDVI), a variable linearly related to the fraction of the photosynthetically active radiation (PAR) intercepted by the canopy. We also analysed the relative importance of environmental factors and land use on the spatial patterns of NDVI. We compared three cultivated land-cover types against native grasslands. The seasonal dynamics of NDVI was used as a descriptor of ecosystem functioning. In order to reduce the dimensionality of our data we analysed the annual integral (NDVI-I), the date of maximum NDVI (DMAX) and the quarterly average NDVI. These attributes were studied for 7 years and for 346 sites distributed across eastern Colorado (USA). Land use did modify ecosystem functioning at the regional level in eastern Colorado. The seasonal dynamics of NDVI, a surrogate for the fraction of PAR intercepted by the canopy, were significantly altered by agricultural practices. Land use modified both the NDVI integral and the seasonal dynamics of this spectral index. Despite the variability within land-cover categories, land use was the most important factor in explaining regional differences of the NDVI attributes analysed. Within the range of environmental conditions found in eastern Colorado, land use was more important than mean annual precipitation, mean annual temperature and soil texture in determining the seasonal dynamics of NDVI.

Aboveground net primary production (ANPP) is positively related to mean annual precipitation, an estimate of water availability. This relationship is fundamental to our understanding and management of grassland ecosystems. However, the slope of the relationship between ANPP and precipitation (precipitation-use efficiency, PUE) has been shown to be different for temporal compared with spatial precipitation series. When ANPP and precipitation are averaged over a number of years for different sites, PUE is similar for grasslands all over the world. Studies for two US Long Term Ecological Research Sites have shown that PUE derived from a long-term dataset (temporal model) has a significantly lower slope than the value derived for sites distributed across the US central grassland region (spatial model). PUE differences between the temporal model and the spatial model may be associated with both vegetational and biogeochemical constraints. Here we use two independent datasets, one derived from field estimates of ANPP and the other from remote sensing, to show that the PUE is low at both the dry end and the wet end of the annual precipitation gradient typical of grassland areas (200–1200 mm), and peaks around 475 mm. The intermediate peak may be related to relatively low levels of both vegetational and biogeochemical constraints at this level of resource availability.

Our objective was to analyse the interannual variability of different characteristics of the seasonal dynamics of NDVI and their relationships with climatic variables for grassland and shrubland sites of North America. We selected twenty-five sites located in relatively undisturbed areas. We analysed the variability of seven traits derived from the annual dynamics of the NDVI at each site: the annual integral, the difference between maximum and minimum NDVI, the dates of the inflection points of a double logistic model fitted to the NDVI curve, the difference between these dates, the date of maximum NDVI, and the coefficient of determination of the double logistic model. The temporal variability of traits that integrated aspects of primary productivity over the year was lower than those related to seasonality. This suggests that from year to year, grassland and shrubland ecosystems would differ more in the timing of production and senescence than in the total amount of carbon fixed. The integral of NDVI showed less temporal variability than annual precipitation. The coefficient of variation of both precipitation and the NDVI integral were positively related. The slope of the relationship was significantly lower than 1, indicating that the variability of ecosystem function is a lower proportion of the variability of annual precipitation in areas with a high relative variability of this climatic variable than in areas of low variability. The variability of most of the NDVI traits analysed showed a negative and, in general, non-linear relationship with annual precipitation. The same kind of relationship has been reported elsewhere for annual precipitation and its coefficient of variation. Mean annual precipitation has been reported as the main control of above-ground net primary production in grassland and shrubland ecosystems. Our results suggest that this climatic variable is also associated with the interannual variability of carbon gains, such as the primary production and its seasonality.

We analyzed the similarity of structural and functional characteristics of temperate grassland and shrubland ecosystems of North and South America. We based our analyses on correlative models that describe the climatic controls of grassland and shrubland structure and functioning at regional scales. We evaluated models that describe the regional distribution of plant functional types (C 3 and C4 grasses and shrubs), soil organic carbon (SOC), and aboveground net primary production (ANPP) and its seasonality. To evaluate the predictive power of the models, we compared their estimates against observed data. We derived data sets, independent from those used to generate the models in North America, from climatically similar areas in South America. Our results support the notion that, in climatically similar regions, structural and func- tional attributes such as plant functional type composition, SOC, ANPP, and ANPP sea- sonality have similar environmental controls, independent of the evolutionary history of the regions. The study suggests the existence of an important degree of convergence at regional scales in both functional and structural attributes. It also points out differences in the regional patterns of some attributes that require further analyses.

Grass cover along a grazing intensity gradient in Patagonia decreases, whereas bare soil and shrub cover increases. Our objective was to study the effect of a change in the dominant plant functional type on soil water balance, primary production, herbivore biomass, roughness, and albedo. Using a soil water balance model, we found increases in evaporation and deep drainage, and a decrease in total transpiration along the grazing intensity gradient. Above-ground primary production, estimated from transpiration, decreased along the grazing intensity gradient because shrubs did not fully compensate for the decrease in grass production. Using a statistical model, we calculated herbivore biomass from estimates of above-ground primary production. Estimated herbivore biomass was lowest in the shrub-dominated extreme of the grazing gradient. Roughness increased from the grass-dominated to the shrub-dominated community. Albedo had a maximum at an intermediate position along the gradient. Our results suggest that changes in plant functional type composition, independent of changes in biomass, affect ecosystem functioning and the exchange of energy and material with the atmosphere. Grasses and shrubs proved to be appropriate plant functional types to link structure and function of ecosystems.

An important goal of conservation biology is the maintenance of ecosystem processes. Incorporating quantitative measurements of ecosystem functions into conservation practice is important given that it provides not only proxies for biodiversity patterns, but also new tools and criteria for management. In the satellite era, the translation of spectral information into ecosystem functional variables expands and complements the more traditional use of satellite imagery in conservation biology. Remote sensing scientists have generated accurate techniques to quantify ecosystem processes and properties of key importance for conservation planning such as primary production, ecosystem carbon gains, surface temperature, albedo, evapotranspiration, and precipitation use efficiency; however, these techniques are still unfamiliar to conservation biologists. In this article, we identify specific fields where a remotely-sensed characterization of ecosystem functioning may aid conservation science and practice. Such fields include the management and monitoring of species and populations of conservation concern; the assessment of ecosystem representativeness and singularity; the use of protected areas as reference sites to assess global change effects; the implementation of monitoring and warning systems to guide adaptive management; the direct evaluation of supporting ecosystem services; and the planning and monitoring of ecological restorations. The approaches presented here illustrate feasible ways to incorporate the ecosystem functioning dimension into conservation through the use of satellite-derived information. © 2012 Springer Science+Business Media B.V.

We assessed the extension of natural habitat conversion into croplands and grazing lands in subtropical NW Argentina and its impact on two key ecosystem functional attributes. We quantified changes in remotely sensed surrogates of aboveground net primary production (ANPP) and seasonality of carbon gains. Both functional attributes are associated with intermediate ecosystem services sensu Fisher et al. (2009). Deforestation was estimated based on photointerpretation of Landsat imagery. The seasonal dynamics of the MODIS satellite Enhanced Vegetation Index (EVI) was used to calculate the EVI annual mean as a surrogate of ANPP, and the EVI seasonal coefficient of variation as an indicator of seasonal variability of carbon gains. The 2000-2007 period showed a high rate of land clearing: 5.9% of NW Argentina (1,757,600. ha) was cleared for agriculture and ranching, corresponding to an annual rate of 1.15%. Dry forests experienced the highest rate and humid forests the lowest. Though land clearing for agriculture and ranching had relatively small impacts on total annual ANPP, once deforested, parcels significantly became more seasonal than the natural vegetation replaced. Such increase in seasonality is associated with a reduction of photosynthetic activity during a portion of the year (fallow). Direct consequences of this reduction can be expected on several ecosystem services such as erosion control and water regulation, due to greater exposure of bare soil, and biodiversity, due to the loss or decline in habitat quality and the decrease of green biomass availability for primary consumers during fallow. Land clearing also increased the magnitude of inter-annual differences in C gains, suggesting a greater buffer capacity against climate fluctuations of natural vegetation compared to croplands. Fil: Volante, José Norberto. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Salta. Estación Experimental Agropecuaria Salta; Argentina Fil: Alcaraz Segura, Domingo. 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; Argentina Fil: Mosciaro, M. J.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Salta. Estación Experimental Agropecuaria Salta; Argentina Fil: Viglizzo, Ernesto Francisco. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; Argentina Fil: 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; Argentina

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; Argentina Fil: 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; Argentina Fil: 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; Argentina

Spatial heterogeneity in ecosystem functioning is a key component of ecological variability requiring special attention in the context of global change. A large history of human use has produced high physiognomic heterogeneity in Mediterranean ecosystems. However, the consequences for ecosystem functioning remain insufficiently understood. We analyzed spectral indicators of matter and energy fluxes in the land surface to classify the functional ecosystem heterogeneity in a Mediterranean region covering different management histories and protection types. We specifically analyzed the spatial variability in seasonal and annual patterns in the Normalized Difference Vegetation Index (NDVI), surface temperature (Ts) and albedo from five Landsat ETM images. Then we classified numerically this variability into ecosystem functional types (EFTs) and explored their seasonal dynamics in terms of photosynthetic radiation absorption and evapotranspiration. We identified eight main EFTs with ecologically relevant differences including contrasting dynamics in fPAR seasonality, great variation in incoming radiation reflection and differing evapotranspiration rates, particularly during the water-limitation period. Functional variability in natural vegetation mostly consisted in dissimilar annual rates of NDVI and albedo, whereas differences in seasonality were more evident in transformed areas. Similarly, the spatial distribution of EFTs was partly associated to protection, with two EFTs exclusive of protected areas and comparatively higher functional diversity in humanized areas. Landform effects on water availability in protected areas and human activities under different ecological settings were seemingly responsible for the large functional diversity of the region. We advocate for the explicit incorporation of multifunctional ecosystem heterogeneity in ecosystem manage- ment and monitoring designs.

Baseline assessments and monitoring of pro- tected areas are essential for making management decisions, evaluating the effectiveness of management practices, and tracking the effects of global changes. For these purposes, the analysis of functional attributes of ecosystems (i.e., different aspects of the exchange of matter and energy) has advantages over the traditional use of structural attributes, like a quicker response to disturbances and the fact that they are easily monitored through remote sensing. In this study, we described the spatiotemporal patterns of different aspects of the ecosystem functioning of the Spanish national parks and their response to environmental changes between 1982 and 2006. To do so, we used the NOAA/AVHRR-GIMMS dataset of the Normalized Difference Vegetation Index (NDVI), a linear estimator of the fraction of photosynthetic active radiation intercepted by vegetation, which is the main control of carbon gains. Nearly all parks have significantly changed during the last 25 years: The radiation interception has increased, the contrast between the growing and non- growing seasons has diminished, and the dates of maximum and minimum interception have advanced. Some parks concentrated more changes than others and the degree of change varied depending on their different environmental conditions, management, and conservation histories. Our approach identified reference conditions and temporal changes for different aspects of ecosystem functioning, which can be used for management purposes of protected areas in response to global changes.

In the last decades, South American ecosystems underwent important functional modifications due to climate alterations and direct human intervention on land use and land cover. Among remotely sensed data sets, NOAA-AVHRR "Normalized Difference Vegetation Index" (NDVI) represents one of the most powerful tools to evaluate these changes thanks to their extended temporal coverage. In this paper we explored the possibilities and limitations of three commonly used NOAA-AVHRR NDVI series (PAL, GIMIMS and FASIR) to detect ecosystem functional changes in the South American continent. We performed pixel-based linear regressions for four NDVI variables (average annual, maximum annual, minimum annual and intra-annual coefficient of variation) for the 1982-1999 period and (1) analyzed the convergences and divergences of significant multi-annual trends identified across all series, (2) explored the degree of aggregation of the trends using the O-ring statistic, and (3) evaluated observed trends using independent information on ecosystem functional changes in five focal regions. Several differences arose in terms of the patterns of change (the sign, localization and total number of pixels with changes). FASIR presented the highest proportion of changing pixels (32.7%) and GIMMS the lowest (16.2%). PAL and FASIR data sets showed the highest agreement, with a convergence of detected trends on 71.2% of the pixels. Even though positive and negative changes showed substantial spatial aggregation, important differences in the scale of aggregation emerged among the series, with GIMMS showing the smaller scale (11 pixels). The independent evaluations suggest higher accuracy in the detection of ecosystem changes among PAL and FASIR series than with GIMMS, as they detected trends that match expected shifts. In fact, this last series eliminated most of the long term patterns over the continent. For example, in the "Eastern Paraguay" and "Uruguay River margins" focal regions, the extensive changes due to land use and land cover change expansion were detected by PAL and FASIR, but completely ignored by GIMMS. Although the technical explanation of the differences remains unclear and needs further exploration, we found that the evaluation of this type of remote sensing tools should not only be focused at the level of assumptions (i.e. physical or mathematical aspects of image processing), but also at the level of results (i.e. contrasting observed patterns with independent proofs of change). We finally present the online collaborative initiative "Land ecosystem change utility for South America", which facilitates this type of evaluations and helps to identify the most important functional changes of the continent. Fil: Baldi, Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentina Fil: Nosetto, Marcelo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentina Fil: Aragón, Myriam Roxana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentina. Universidad de Buenos Aires. Facultad de Agronomía; Argentina Fil: Aversa, Fernando. Universidad Nacional de San Luis; Argentina Fil: 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 Fil: Jobbagy Gampel, Esteban Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentina

Soil moisture, and hence precipitation, exerts a dominant control on net primary productivity (NPP; the rate of carbon accumulation by autotrophs) in semiarid to subhumid ecosystems, such as grasslands and shrublands. At the global scale, mean annual precipitation has been shown to account for >50% of the variance in aboveground net primary production (ANPP) in grassland ecosystems (Lauenroth 1979; Le Houerou et al. 1988). Within specific regions, numerous investigators have demonstrated strong positive relationships between mean annual precipitation (MAP) and primary productivity (or some surrogate variable) for various ecosystems globally, including the Great Plains grasslands (Sala et al. 1988; Knapp et al. 2001; Epstein et al. 2002), the Patagonian steppe (Austin and Sala 2002; Jobbagy et al. 2002), African grasslands and savannas (Breman and de Wit 1983; McNaughton et al. 1993; Scanlon et al. 2002), and grasslands and shrublands of Inner Mongolia and northeastern China (Gao and Yu 1998; Yu et al. 2004).

We analyzed data sets on phytomass production, basal cover, and monthly precipitation of a semiarid grassland in South Africa for good, medium, and poor rangeland condition (a) to investigate whether phytomass production per unit of basal cover differed among rangeland conditions, (b) to quantify the time scales of a carryover effect from production in previous months, and (c) to construct predictive models for monthly phytomass. Finally, we applied the best models to a 73-year data set of monthly precipitation data to study the long-term variability of grassland production. Our results showed that mean phytomass production per unit of basal cover did not vary significantly among the rangeland conditions—that is, vegetated patches in degraded grassland have approximately the same production as vegetated patches in grassland in good condition. Consequently, the stark decline in production with increasing degradation is a first-order effect of reduced basal area. Current-year precipitation accounted for 64%, 62%, and 36% of the interannual variation in phytomass production for good, medium, and poor condition, respectively. We found that 61%, 68%, and 33%, respectively, of the unexplained variation is related to a memory index that combines mean monthly temperature and a memory of past precipitations. We found a carryover effect in production from the previous 4 years for grassland in good condition and from the previous 1 or 3S month for grassland in medium and poor condition. The memory effect amplified the response of production to changes in precipitation due to alternation of prolonged periods of dry or wet years/months at the time scale of the memory. The interannual variability in phytomass production per unit basal cover (coefficient of variation [CV] = 0.42–0.50 for our 73-year prediction, CV = 0.57–0.71 for the 19-year data) was greater than the corresponding temporal variability in seasonal rainfall (CV = 0.29).