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Land use change is a key component of regional environmental change. In mountain regions, where conditions for agriculture and human life are often difficult, land use trends are dominated by changes in the population's distribution across rural and urban areas and shifts in the main human activities. In the Argentinian puna—a high-elevation subtropical plateau of about 95,000 km2 situated above 3200 masl—land is chiefly used for grazing, mining, and tourism. In this article, we analyze trends in these land uses over the last 57 years in the context of climatic changes toward drier and warmer conditions. Since 1960, the human population grew from 80,000 to 130,000; but this increase largely occurred in the scattered urban centers, while the rural population decreased. The main livestock— sheep—showed a net decrease of around 100,000 animals (–18.5%), with numbers increasing between 1960 and 1980 and then dropping markedly. The number of mining operations declined during the 1970s and 1980s and then rose sharply, reaching a 30% increase since the 1990s. Simultaneously, structural wild vicuña populations increased from a few thousand to around 130,000. These results show that environmental changes over the past half century involved a major wildlife recovery associated with a change from widespread extensive grazing to intensive but spatially limited impacts around mining operations and growing urban centers. Tourism emerged as a new activity over the last decades, but the environmental impacts have been poorly studied. To promote local development and regional conservation, research priorities should include (1) empirical assessments of the ecological consequences of land use changes, such as grazing regimes shifting from domestic to wild herbivores, as well as the impacts of mining, tourism, and urbanization on wetlands and hydrological regimes; (2) modeling of future scenarios of mining and tourism expansion and resulting conflicts with environmental conservation; and (3) coproduction of knowledge about interactions among land uses, climate change, and the different decision-making agents.

Size fluctuations in endorheic lakes in northwestern Argentina (NWA) and southwestern Bolivia (SWB) are very sensitive to basin hydrological balances, and consequently, very vulnerable to deleterious effects from climatic changes. The management of these water resources and their biodiversity requires a comprehensive knowledge of their natural variability over multiple timescales. In this study, we present a multi-century reconstruction of past lake-area fluctuations in NWA and SWB. The evidence used to develop and validate this reconstruction includes satellite images and a century-long tree-ring record from P. tarapacana. Inter-annual fluctuations in lake area of nine lakes were quantified based on Landsat satellite images over the period 1975 to 2009. A regional P. tarapacana tree-ring chronology, composite from two sampling sites, was used as predictors in a regression model to reconstruct the mean annual (January–December) lake area from the nine lakes. The reconstruction model captures 62 % of the total variance in lake-area fluctuations and shows adequate levels of cross-validation. This high-resolution reconstruction covers the past 601 years and characterizes the occurrence of annual to multi-decadal lake area fluctuations and its main oscillation modes of variability. Our reconstruction points out that the late 20th century decrease in lake area was exceptional over the period 1407–2007; a persistent negative trend in lake area is clear in the reconstruction and consistent with glacier retreat and other climate proxies from the Altiplano and the tropical Andes. Since the mid 1970s, the Vilama-Coruto lake system recorded an accelerated decrease in area consistent with an increasing recurrence of extremely small lake-area events. Throughout the 601 years, the reconstruction provides valuable information about spatial and temporal stabilities of the relationships between changes in lake area, ENSO, and PDO, highlighting the Pacific influence over most modes of lake area variability. Global and regional climate models for the Altiplano project a marked reduction in precipitation to the end of the 21st century, exacerbating presently dry conditions. These results provide a baseline for the historical range of variability in lake fluctuations and thus should be considered for the management of biodiversity and water resources in the Central Andes during the next decades.

Despite the negative impact on human, animal and environmental health, synthetic fungicides are the most common agrochemicals used to control Botrytis cinerea, the causal agent of grey mold disease. Strawberry plants are very susceptible to many pathogens, especially the necrotrophic fungus B. cinerea. In this work, we show that two fungal extracts obtained from a local isolate of Colletotrichum acutatum (M11) can protect strawberry plants against grey mold. Fungal culture filtrate (CF), and the axenic semi-purified culture filtrate (ACF) induce local and systemic acquired resistance against B. cinerea , and reduce fungal virulence. These results suggest that CF and ACF can be used as effective ingredients of bioproducts to control grey mold in strawberry crop. We also show that the elicitor peptide flg22 is effective to confer strawberry plants local and systemic protection against B. cinerea but only when applied 24 h prior to the infection.

Development of a sustainable agriculture is a current trend searching for alternative and more environmentally friendly strategies to control crop diseases. The necrotrophic fungus Botrytis cinerea, the causal agent of grey mould, affects crops pre- and post-harvest and cause huge economical losses. Microorganisms and microbially-derived elicitors are known to induce plant defences. Here, we study two fungal extracts derived from Colletotrichum acutatum (isolate M11). The crude extract, called CF (culture filtrate) and the semi-purified fraction ACF (axenic culture filtrate) consist in a blend of fungal-derived elicitors. Their activities were evaluated in the plant-pathogen system Arabidopsis thaliana-B. cinerea. Both CF and ACF induced local and systemic resistance, rendering A. thaliana resistant against grey mould disease. The extracts showed no antifungal activity since no inhibition of mycelium growth, changes in hyphal ultrastructure or damage in cell membrane permeability were observed. These findings would indicate that the protective effect was indirect and it was found that CF and ACF induced up-regulation of the defence-related genes PR1, WRKY70 and ERF6, as well as giving local callose deposition in treated leaves. Both fungal extracts have the potential to be used as a main component of a biologically based disease control product with activity against grey mould, with the advantage that the purification process of CF is simpler than for ACF.

A global analysis shows that for most tree species the largest trees are the fastest-growing trees, a finding that resolves conflicting assumptions about tree growth and that has implications for understanding forest carbon dynamics, resource allocation trade-offs within trees and plant senescence. The importance of old trees Old forests and their leaves fix less carbon than do new forests, but does this apply at the individual tree level? This study uses a global analysis of more that 400 tree species to show that it does not. Rather, larger and older trees accumulate carbon more rapidly than do younger, smaller ones. This can be reconciled with the effects at other levels by taking into account increases in leaf number and reductions in forest density with age. The rapid growth of large trees means that, relative to their numbers, they could have a disproportionately important role in forest feedbacks to the terrestrial carbon cycle and global climate system. Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations 1 . Our ability to understand and predict changes in the forest carbon cycle—particularly net primary productivity and carbon storage—increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands 2 , 3 . Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree 4 , 5 , 6 , 7 , in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level 8 , 9 , 10 and stand-level 10 productivity can be explained, respectively, by increases in a tree’s total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation 11 and plant senescence 12 .

1. To investigate life-history differentiation and an objective functional classification of tree species we analysed the demography of 29 species in subtropical montane forests in north-western Argentina. 2. We computed 13 growth, demographic, abundance and distribution variables based on: (i) two 5-year re-measurements of stems >= 10 cm diameter at breast height (d.b.h.) in 8 ha of old growth forest and 4 ha of secondary forest; (ii) assessments of tree crown illumination; and (iii) sapling counts under shade and on landslides. 3. We assessed the potential confounding effects of stem size and crown illumination on absolute stem diameter growth rate for the 24 most abundant species. As diameter increased, one species showed significant increases in growth rate and five showed significant reductions. Seventeen species grew significantly faster with increased exposure to light and we controlled for this confounding effect in the computation of diameter growth rates for subsequent analyses. 4. A principal component analysis resulted in three meaningful and interpretable axes of demographic variation across species. The first axis (interpreted as shade tolerance) indicates that trees of species with inherently high growth rates tend to have well-exposed crowns at 10-30 cm d.b.h., have high density of trees in secondary forest and are less tolerant of shade. 5. The second axis (turnover) shows that in old-growth forest short-lived species, with high mortality rates, size-class distributions with a steep negative slope and low dominance, persist due to high rates of recruitment (to >= 10 cm d.b.h.). 6. The third axis indicates that species that colonize landslides have lower tree recruitment rates and greater growth variability in secondary forest, reflecting spatio/temporal differences in species' recruitment linked to differences in their substrate requirements for regeneration. 7. Maximum height and diameter are correlated with the first and second axes, indicating that higher rates of both growth and survival permit some species to attain large size. 8. All three demographic axes depict separate trade-offs that confer competitive advantage to each 'demographic type' under contrasting ecological conditions (of light availability, disturbance frequency and disturbance intensity), thus underpinning species' coexistence in dynamic forest landscapes.

Contrary to the general trend in the tropics, forests have recovered in Puerto Rico from less than 10% of the landscape in the late 1940s to more than 40% in the present. The recent Puerto Rican history of forest recovery provides the opportunity to study the ecological consequences of economic globalization, reflected in a shift from agriculture to manufacturing and in human migration from rural to urban areas. Forest structure rapidly recovers through secondary succession, reaching mature forest levels of local biodiversity and biomass in approximately 40 years. Despite the rapid structural recovery, the legacy of pre-abandonment land use, including widespread abundance of exotic species and broadscale floristic homogenization, is likely to persist for centuries.

The landscape configuration of socio-ecological land systems results from the interaction between the environmental conditions (relatively homogeneous within ecoregions) and country-level management and land-use decisions. However, social, land-use and sustainability research disciplines often study each independently. We used Euclidean distance analyses of five indicators of land systems functioning to explore the geographical patterns of across-border human-induced asymmetries in transnational ecoregions of South America. The most asymmetric transnational ecoregions occurred in the tropical rainforest biome which also showed the widest range of asymmetry values compared to other biomes. In contrast, transnational ecoregions in montane grasslands showed comparatively little asymmetries, and tropical dry forests showed intermediate asymmetry values. This pattern indicates that major asymmetries occur in land systems located in productive biomes with a comparatively recent history of development, whereas mature socio-ecosystems with a long history of human land use are more homogeneous across borders. In some cases, asymmetries may stabilize as a consequence of reinforcing feedbacks that promote contrasting land-use decisions across borders, including, for example, the establishment of protected areas, or the promotion of agro-industrial activities. Transnational socio-ecological land systems can be used to evaluate alternatives for sustainable development because they highlight the influence of institutions under different governance regimes in defining the spatial configuration and ecological properties of regions. We invite land-use and sustainability scientists to consider political border interactions as valuable “natural experiments” to better understand the interrelations between biophysical and political systems in defining planetary geographical-ecology in the Anthropocene.

In Argentina, deforestation due to agriculture expansion is threatening the Semi-arid Chaco, one of the largest forested biomes of South America. This study focuses on the north-west boundary of the Argentine Semi-arid Chaco, where soybean is the most important crop. Deforestation was estimated for areas with different levels of soil and rainfall limitation for agriculture between 1972 and 2001, with a finer analysis in three periods starting in 1984, which are characterized by differences in rainfall, soybean price, production cost, technology-driven yield and national gross domestic product. Between 1972 and 2001, 588 900 ha (c. 20% of the forests) were deforested. Deforestation has been accelerating, reaching >28 000 ha yr−1 after 1997. The initial deforestation was associated with black bean cultivation following an increase in rainfall during the 1970s. In the 1980s, high soybean prices stimulated further deforestation. Finally, the introduction of soybean transgenic cultivars in 1997 reduced plantation costs and stimulated a further increase in deforestation. The domestic economy had little association with deforestation. Although deforestation was more intense in the moister (rainfall >600 mm yr−1) areas, more than 300 000 ha have already been deforested in the drier areas, suggesting that climatic limitations are being overcome by technological and genetic improvement. Furthermore, more than 300 000 ha of forest occur in sectors without major soil and rainfall limitations. If global trends of technology, soybean markets and climate continue, and no active conservation policies are applied, vast areas of the Chaco will be deforested in the coming decades.