Marcos Texeira | Universidad de Buenos Aires (original) (raw)

Papers by Marcos Texeira

Environmental Development

Journal of Arid Environments

Background: South America faces strong environmental transformations due to agriculture and infra... more Background: South America faces strong environmental transformations due to agriculture and infrastructure expansion and due to demographic growth, demanding immediate action to preserve natural assets by means of the deployment of protected areas. Currently, 7.1% of the (sub)continent is under strict conservation categories (I to IV, IUCN), but the spatial distribution of these 1.3 x 106 km2 is poorly understood. We evaluate protected area representativeness, map conservation priorities and assess demographic, productive or geopolitical causes of the existing protection spatial patterns using a random forest method. Methods: We characterized representativeness by two dimensions: the extent and the equality of protection. The first refers to the fraction of a territory under protection, while the second refers to the spatial distribution of this protection along natural conditions. We characterized natural conditions by 113 biogeographical units (specifically, ecoregions) and a seri...

Ecología Austral

What is the status of the Forest Law in the Chaco Region ten years after its enaction? Reviewing ... more What is the status of the Forest Law in the Chaco Region ten years after its enaction? Reviewing its past to discuss its future. In a complex environmental, productive and socioeconomic scenario, on November 28th, 2007, the National Act N°26.331 of "Minimum Standards for the Environmental Protection of Native Forests" (known as the "Forest Law") was sanctioned in Argentina with the purpose of protecting native forests at the national scale. In this article, we aim to critically synthesize the available information about this law ten years after its sanction from an approach that takes into account environmental, economic and social aspects. In particular, we characterize the performance of this law in the Chaco Region in different dimensions, identify its main challenges and describe a series of proposals that from the science and technology sector can contribute to its (re)design and implementation in the context of the revisions of the Provincial Native Forest Land Use Planning Programs. In order to accomplish these objectives, we integrated information available from different sources, such as laws and regulations (national and provincial), scientific literature, reports from government agencies and NGOs and newspaper articles. The Forest Law installed in the public opinion of our country the problems related to the loss of native forests and has positioned itself as the main national instrument for forest conservation. Although deforestation rates lowered in the Chaco Region, there is no clear evidence that this reduction was due to its application. The Forest Law in the Chaco Region presents a series of challenges to improve its performance in terms of its effectiveness, equity and social legitimacy. In this paper, we present ten observations that emerge from the review carried out. On the other hand, linked to these observations, we outline a series of research and action proposals for enhancing the performance of the law.

PLOS ONE, 2016

The dry subtropics are subject to a rapid expansion of crops and pastures over vast areas of natu... more The dry subtropics are subject to a rapid expansion of crops and pastures over vast areas of natural woodlands and savannas. In this paper, we explored the effect of this transformation on vegetation productivity (magnitude, and seasonal and long-term variability) along aridity gradients which span from semiarid to subhumid conditions, considering exclusively those areas with summer rains (>66%). Vegetation productivity was characterized with the proxy metric "Enhanced Vegetation Index" (EVI) (2000 to 2012 period), on 6186 natural and cultivated sampling points on five continents, and combined with a global climatology database by means of additive models for quantile regressions. Globally and regionally, cultivation amplified the seasonal and inter-annual variability of EVI without affecting its magnitude. Natural and cultivated systems maintained a similar and continuous increase of EVI with increasing water availability, yet achieved through contrasting ways. In natural systems, the productivity peak and the growing season length displayed concurrent steady increases with water availability, while in cultivated systems the productivity peak increased from semiarid to dry-subhumid conditions, and stabilized thereafter giving place to an increase in the growing season length towards wetter conditions. Our results help to understand and predict the ecological impacts of deforestation on vegetation productivity, a key ecosystem process linked to a broad range of services.

PeerJ, 2017

BackgroundProtected areas, regarded today as a cornerstone of nature conservation, result from an... more BackgroundProtected areas, regarded today as a cornerstone of nature conservation, result from an array of multiple motivations and opportunities. We explored at global and regional levels the current distribution of protected areas along biophysical, human, and biological gradients, and assessed to what extent protection has pursued (i) a balanced representation of biophysical environments, (ii) a set of preferred conditions (biological, spiritual, economic, or geopolitical), or (iii) existing opportunities for conservation regardless of any representation or preference criteria.MethodsWe used histograms to describe the distribution of terrestrial protected areas along biophysical, human, and biological independent gradients and linear and non-linear regression and correlation analyses to describe the sign, shape, and strength of the relationships. We used a random forest analysis to rank the importance of different variables related to conservation preferences and opportunity driv...

Journal of Arid Environments, 2016

Proceedings of the Royal Society B: Biological Sciences, 2008

Persistence and ubiquity of vertically transmitted Neotyphodium endophytes in grass populations i... more Persistence and ubiquity of vertically transmitted Neotyphodium endophytes in grass populations is puzzling because infected plants do not consistently exhibit increased fitness. Using an annual grass population model, we show that the problems for matching endophyte infection and mutualism are likely to arise from difficulties in detecting small mutualistic effects, variability in endophyte transmission efficiency and an apparent prevalence of non-equilibrium in the dynamics of infection. Although endophytes would ultimately persist only if the infection confers some fitness increase to the host plants, such an increase can be very small, as long as the transmission efficiency is sufficiently high. In addition, imperfect transmission limits effectively the equilibrium infection level if the infected plants exhibit small or large reproductive advantage. Under frequent natural conditions, the equilibrium infection level is very sensitive to small changes in transmission efficiency and host reproductive advantage, while convergence to such an equilibrium is slow. As a consequence, seed immigration and environmental fluctuation are likely to keep local infection levels away from equilibrium. Transient dynamics analysis suggests that, when driven by environmental fluctuation, infection frequency increases would often be larger than decreases. By contrast, when due to immigration, overrepresentation of infected individuals tends to vanish faster than equivalent overrepresentation of noninfected individuals.

Journal of Vegetation Science, 2012

Abbreviations ANPP = aboveground net primary production; APARg = absorbed photosynthetic radiatio... more Abbreviations ANPP = aboveground net primary production; APARg = absorbed photosynthetic radiation by green vegetation; CV = coefficient of variation; EVI = enhanced vegetation index; fAPARg = the fraction of photosynthetically active radiation absorbed by green vegetation; MODIS = Moderate Resolution Imaging Spectroradiometer; NDVI = normalized difference vegetation index; PAR = incoming photosynthetically active radiation.

Journal of Arid Environments, 2012

Climate variability affects both animal and plant populations. Understanding how this variability... more Climate variability affects both animal and plant populations. Understanding how this variability is modulated by topography, vegetation and population densities and how this impact on ungulate demography is an important step in order to forecast consequences of alternative management scenarios or the effects of climate change.

Ecological Modelling, 2008

Artificial neural networks Environmental controls Herbivore reproductive performance NDVI Patagon... more Artificial neural networks Environmental controls Herbivore reproductive performance NDVI Patagonia Sheep a b s t r a c t Environmental variability affects life history and fitness of both animal and plant species. For herbivores in particular, climate can have strong direct and indirect effects on demography,

Austral Ecology, 2009

We explored the small-scale plant species mobility in a subhumid native grassland subjected to gr... more We explored the small-scale plant species mobility in a subhumid native grassland subjected to grazing by cattle in south-western Uruguay. We established four permanent plots of 40 ¥ 40 cm, divided in 16 ¥ 16 cells. In each cell, the presence of species was seasonally recorded for 2 years and annually recorded for 4 years. By nesting the cells, we studied the mobility at different scales, from 6.25 cm 2 to 400 cm 2 . At each scale we measured species richness, cumulative richness and the turnover rates of the dominant species. We found that the cumulative species richness was an increasing power function, with higher accumulation rates with smaller spatial scale. Although species richness showed seasonal fluctuations, the mean species richness was constant during the study period. We detected significant spatio-temporal variability in mobility patterns among species. Certain species showed a high capacity to colonize new sites, whereas other species rotate among sites that they previously occupied. Grazed communities in Uruguayan Campos are structured as a dense matrix of perennials grasses and forbs, where vegetative propagation is the main form of growth of the species. The small-scale dynamics and the high variability in the mobility characteristics could be linked with the diversity of growth forms and spatial strategies of the species in this community. We believe that a high degree of small-scale spatial dynamics contribute to explain the species coexistence and the apparent stability of communities at local scales.

Austral Ecology, 2014

At micro-site scale, the spatial pattern of a plant species depends on several factors including ... more At micro-site scale, the spatial pattern of a plant species depends on several factors including interactions with neighbours. It has been seen that unfavourable effects generate a negative association between plants, while beneficial effects generate a positive association. In grasslands, the presence of shrubby species promotes a particular microenvironment beneath their canopy that could affect differently the spatial distribution of plants with different tolerance to abiotic conditions. We measured photosynthetic active radiation, air temperature and wind speed under shrub canopies and in adjacent open sites and analysed the spatial distribution of four grass species (two C3 and two C4) in relation to shrub canopy in a grazed sub-humid natural grassland in southern Uruguay. Radiation, air temperature and wind speed were lower under shrubs than in adjacent open sites. The spatial distribution of grasses relative to the shrub canopy varied depending on the photosynthetic metabolism of grasses. C4 grasses showed a negative association or no correlation with the shrubs, whereas C3 grasses showed a positive association. Our results highlight the importance of the photosynthetic metabolism of the grasses in the final outcome of interactions between grasses and shrubs. Micro-environmental conditions generated underneath shrubs create a more suitable site for the establishment of C3 than for C4 grasses. These results show that facilitation could be more important than previously thought in sub-humid grasslands.

Agricultural Systems, 2006

Sheep production is the main agricultural activity in Patagonia. Since the middle of the 20th cen... more Sheep production is the main agricultural activity in Patagonia. Since the middle of the 20th century, sheep numbers have declined steadly. We used historical records of stock numbers in four ranches to analyze the importance of regional factors so as to explain the decline of the Patagonian sheep flocks. We found that the stocks of all the four ranches declined with a similar trend but fluctuated independently, thus reflecting a complex interaction between regional and local factors. Aboveground net primary production (ANPP) and vegetation physiognomy explained most of the differences in the flocks declining rates. We estimated demographic parameters for two ranches differing in their average annual growth rates. From these demographic parameters, we constructed deterministic and stochastic matrix models to establish the relative contribution of demographic processes to the observed decline. Matrix models projected a faster decline than that observed in the ranch used to calibrate the model. This suggests that the recorded demographic parameters could drive most stocks to extinction in less than 100 years. We concluded that the observed dynamics would be generated by demographic processes, but extinction is delayed or avoided by a continuous intake of animals. Ewe survival was the most important parameter in controlling the growth rate of the flocks. The environmental stochastic model showed that the growth of the stocks was highly sensitive 0308-521X/$ -see front matter Ó

Landscape Ecology, 2011

Diversity often increases ecosystem functioning and enhances stability, but this relationship has... more Diversity often increases ecosystem functioning and enhances stability, but this relationship has been evaluated at the community scale and considering, for the most part, only species richness. Here, we explored the relationship between landscape diversity and either the coefficient of variation or the interannual standard deviation of greenness in Pampean grasslands and Patagonian meadows, and tried to elucidate the mechanisms responsible for the resulting patterns. The coefficient of variation decreased with increasing landscape richness in Pampas but remained constant in Patagonia, while the interannual standard deviation of greenness decreased in both regions. The diversity-variability relationship in Pampean grasslands was largely accounted for by the mechanism of statistical averaging, while in Patagonian meadows, it was accounted for by a combination of statistical averaging, mean-variance rescaling and positive covariation of landscape units. There were no cases of negative covariance among landscape units. This is the first demonstration that landscape diversity increases stability of ecosystem functioning.