•Soil aggregates were formed in the new top soil 5.5 yr. after the volcanic eruption.•Smaller size fractions of water-stable aggregates dominate the top soil with lower C and N content.•Larger size ...fractions of water-stable aggregates were lower but with higher C and N content.•Good grassland conditions (biological legacy) improved the soil aggregates quality compared to poor ones.•Meadows showed a fast soil C recovery and thus a potential to mitigate volcanic CO2.
Although volcanism may be perceived by the society as a phenomenon with mostly negative consequences, this is not always the case especially for natural systems. There is a limited knowledge on how the deposited pristine ash becomes immobilized and stabilized in the soil after the volcanic event. Here, we studied processes of soil aggregates formation in the buried ash layer in an early stage of the succession as well as the influence of the biological legacy (previous land management history) on these processes after the 2011 volcanic event of the Puyehue–Cordón Caulle Volcanic Complex. 5.5 years after the eruption we collected soil cores to a 10 cm depth in wet and mesic meadows with good and poor grassland conditions induced by light and heavy grazing intensity, respectively, in the East semiarid region of North Patagonia, Argentina. The ash layer was observed down to 5 cm from the soil surface, clearly differentiating a newly developed soil layer formed after the volcanic event. Accordingly, the top 5 cm were examined for the distribution of different size fractions of water-stable soil aggregates and their associated organic carbon (C) and total nitrogen (N) contents. We detected signs of physical and physicochemical changes in respect to the pristine ash collected at these sites in 2011. Soil neoformation processes were detected through the presence of large (4%) and small (21%) macroaggregates, although microaggregates (~45%) and silt + clay fractions (~29%) dominated the soil mass (ash-soil matrix: 0–5 cm depth). C and N contents decreased in a sequence: large macroaggregates ≥ small macroaggregates > microaggregates ≥ silt + clay, highlighting the importance of soil organic matter in the formation of larger-size aggregates and their quality (C and N contents). Biological legacy influenced soil aggregate formation and their quality, as reflected by a higher mass of small macroaggregates and a lower mass of microaggregates (only in mesic meadows) and by higher C and N contents under good grassland conditions. The seasonal hydrological conditions of meadow soils (i.e., soil water content, wetting and drying cycles) via effects on biological and physical processes likely resulted in a reduced aggregation in wet meadows. We noticed an incipient but present soil aggregation processes in these semiarid wetlands translated in the immobilization and stabilization of the buried ashes in the soil. The total C content in the new 0–5 cm soil layer increased at a rate of 1.0 Mg C ha−1 yr−1, on average. This indicates a functional recovery of the ecosystem along with a substantial CO2 mitigation potential in the ashes stabilized with soil organic matter, which might partially counterbalance CO2 emitted during the eruption.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Data on tree biomass are essential for understanding the forest carbon cycle and plant adaptations to the environment. We determined biomass accumulation and allometric relationships in the ...partitioning of biomass between aboveground woody biomass, leaves and roots in
Nothofagus antarctica. We measured above- and belowground biomass of
N. antarctica trees across different ages (5–220 years) and crown classes (dominant, codominant, intermediate and suppressed) in three site qualities. The biomass allocation patterns were studied by fitting allometric functions in biomass partitioning between leaves (
M
L), stem and branches (
M
S) and roots (
M
R). These patterns were tested for all pooled data and according to site quality and crown classes. Biomass accumulation varied with crown class and site quality. The root component represented 26–72% of the total biomass depending on age and site.
N. antarctica scaling exponents for the relationships
M
L
vs.
M
S,
M
A
vs.
M
R, and
M
S
vs.
M
R were close to those predicted by the allometric biomass partitioning model. However, when biomass allocation was analyzed by site quality the scaling exponents varied following the optimal partitioning theory which states that plants should allocate more biomass to the part of the plant that acquires the most limiting resource. In contrast, the crown class effect on biomass partitioning was almost negligible. In conclusion, to obtain accurate estimations of biomass in
N. antarctica trees the allometric approach appears as an useful tool but the site quality should be taken into consideration.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The availability of soil-stored seed determines initial plant functional types in post-fire landscapes. We evaluated the post-fire regeneration of Nothofagus pumilio forests, in Patagonia, Argentina, ...analyzing the soil seed bank (SSB) and the above-ground vegetation (AV). At three sites: La Colisión, Río Turbio and Monte Zeballos, burned in 2008, 1980 and 1941, respectively, we sampled the SSB and AV in two transects from the edge of the remaining forest, up to 90 m within the burned area, and recorded the emergence (198 soil samples) and presence of vascular species. To determine the effect of the distance to the remnant forest on the germinable seed bank, we performed simple linear regression analysis through the use of linear mixed-effect models, and we analyzed the similarity between the composition of SSB and AV with PERMANOVA. The emergence of plant growth forms had different patterns in relation to the distance from the forest in the three sites, which might be associated with the time of fire occurrence, and specific characteristics of each site. The emergence of N. pumilio was registered at more than one distance at the recent burning site. Herbs constituted the main source of cover with 69% of the composition, and native/endemic species represented 71%. This study contributes to the understanding of the relationship between the seed bank and standing vegetation and a better understanding of the resilience of post-fire N. pumilio forests. Our findings suggest that from 15–20 m from the edge, the SSB would be insufficient to ensure the spontaneous recovery of the forest, making active restoration necessary in order to tend to a recovery of the structure and functionality of the original community.
•Stakeholder choices on ecosystem use are central in ES trade-off analysis.•ES trade-offs analysis needs to embrace the full complexity to be useful for spatial planning.•The impact of trade-offs is ...often related to the intensity of use of ecosystem.•Regulating ES are rarely the main focus of trade-offs, but often are more impacted than provisioning and cultural ES.•Responses to trade-offs depend on the level of influence and concern of stakeholders.
Spatial planning has to deal with trade-offs between various stakeholders’ wishes and needs as part of planning and management of landscapes, natural resources and/or biodiversity. To make ecosystem services (ES) trade-off research more relevant for spatial planning, we propose an analytical framework, which puts stakeholders, their land-use/management choices, their impact on ES and responses at the centre. Based on 24 cases from around the world, we used this framing to analyse the appearance and diversity of real-world ES trade-offs. They cover a wide range of trade-offs related to ecosystem use, including: land-use change, management regimes, technical versus nature-based solutions, natural resource use, and management of species. The ES trade-offs studied featured a complexity that was far greater than what is often described in the ES literature. Influential users and context setters are at the core of the trade-off decision-making, but most of the impact is felt by non-influential users. Provisioning and cultural ES were the most targeted in the studied trade-offs, but regulating ES were the most impacted. Stakeholders’ characteristics, such as influence, impact faced, and concerns can partially explain their position and response in relation to trade-offs. Based on the research findings, we formulate recommendations for spatial planning.
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Alpine environments and their temporal changes are rarely studied at high latitudes in the southern hemisphere. We analyzed alpine plants, soil temperatures, and growing-season length in mountains of ...two landscapes of South Patagonia (46° to 56° SL): three summits (814–1085 m a.s.l) surrounded by foothill grasslands in Santa Cruz province (SC), and four summits (634–864 m a.s.l.) in sub-Antarctic forests of Tierra del Fuego province (TF). Sampling followed the protocolized methodology of the Global Observational Research Initiative in Alpine Environments (GLORIA). Factors were topography (elevation and cardinal aspect) and time (baseline vs. re-sampling for plants, five annual periods for temperatures), assessed by univariate and multivariate tests. Plant composition reflected the lowland surrounding landscapes, with only 9 mountain species on 52 totals in SC and 3 on 30 in TF. Richness was higher in re-sampling than baseline, being assemblages more influenced by aspect than elevation. Mean annual soil temperature and growing-season length, which varied with topography, were related to the Multivariate El Niño Southern Oscillation Index (MEI) but did not show clear warming trends over time. We highlight the importance of long-term studies in mountainous regions of extreme southern latitudes, where factors other than warming (e.g., extreme climate events) explain variations.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
•Ecosystem service knowledge did not serve asan impartial arbiter between policy options.•Close interaction between researchers, practitioners and stakeholders contributed to conceptual ...learning.•Competing interests and political agendas and scientific disputes constrained knowledge uptake.•Other constraints were professional norms and competencies, and lack of vertical and horizontal integration.•Transparent participatory methods, social capital, policy champions facilitated knowledge uptake.
The promise that ecosystem service assessments will contribute to better decision-making is not yet proven. We analyse how knowledge on ecosystem services is actually used to inform land and water management in 22 case studies covering different social-ecological systems in European and Latin American countries. None of the case studies reported instrumental use of knowledge in a sense that ecosystem service knowledge would have served asan impartial arbiter between policy options. Yet, in most cases, there was some evidence of conceptual learning as a result of close interaction between researchers, practitioners and stakeholders. We observed several factors that constrained knowledge uptake, including competing interests and political agendas, scientific disputes, professional norms and competencies, and lack of vertical and horizontal integration. Ecosystem knowledge played a small role particularly in those planning and policy-making situations where it challenged established interests and the current distribution of benefits from ecosystems. The factors that facilitated knowledge use included application of transparent participatory methods, social capital, policy champions and clear synergies between ecosystem services and human well-being. The results are aligned with previous studies which have emphasized the importance of building local capacity, ownership and trust for the long-term success of ecosystem service research.
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1. Reductions in community evenness can lead to local extinctions as dominant species exclude subordinate species; however, herbivores can prevent competitive exclusion by consuming otherwise ...dominant plant species, thus increasing evenness. While these predictions logically result from chronic, gradual reductions in evenness, rapid, temporary pulses of dominance may also reduce species richness. Short pulses of dominance can occur as biotic or abiotic conditions temporarily favour one or a few species, manifested as increased temporal variability (the inverse of temporal stability) in community evenness. Here, we tested whether consumers help maintain plant diversity by reducing the temporal variability in community evenness. 2. We tested our hypothesis by reducing herbivore abundance in a detailed study of a developing, tallgrass prairie restoration. To assess the broader implications of the importance of herbivory on community evenness as well as potential mechanisms, we paired this study with a global herbivore reduction experiment. 3. We found that herbivores maintained plant richness in a tallgrass prairie restoration by limiting temporary pulses in dominance by a single species. Dominance by an annual species in a single year was negatively associated with species richness, suggesting that short pulses of dominance may be sufficient to exclude subordinate species. 4. The generality of this site-level relationship was supported by the global experiment in which inter-annual variability in evenness declined in the presence of vertebrate herbivores over timeframes ranging in length from 2 to 5 years, preventing declines in species richness. Furthermore, inter-annual variability of community evenness was also negatively associated with pre-treatment species richness. 5. Synthesis. A loss or reduction of herbivores can destabilize plant communities by allowing brief periods of dominance by one or a few species, potentially triggering a feedback cycle of dominance and extinction. Such cycles may not occur immediately following the loss of herbivores, being delayed until conditions allow temporary periods of dominance by a subset of plant species.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
Entre los años 2022 y 2023 se inició la producción de vegetales en módulos de hidroponia instalados en las Bases Antárticas Conjuntas argentinas Marambio y Esperanza, cuyo objetivo principal es el ...abastecimiento continuo de alimento fresco para su personal. En este sentido, para el consumo humano y para la producción hidropónica se requiere de un conocimiento y control preciso de la calidad del agua. Durante el invierno de 2022 se realizaron análisis de parámetros de la calidad de agua en fuentes de abastecimiento y circuitos de distribución de ambas Bases. Se evaluaron analitos de interés para la caracterización de la aptitud para consumo humano y para el desarrollo de soluciones nutritivas. Ambas Bases cuentan con un abastecimiento de agua de buena aptitud general, con escasos parámetros por fuera de los estándares de calidad vigentes en el país. Los circuitos de potabilización implementados aseguran la atenuación de riesgos para la elaboración de alimentos y la bebida. Mientras que en la Base Esperanza no se presentaron restricciones para la hidroponia, con un agua disponible de baja mineralización, baja dureza, baja alcalinidad, baja conductividad y pH apropiado, en la Base Marambio ha resultado necesario incorporar una planta de ósmosis inversa para atenuar concentraciones altas en algunas sales que, sin representar riesgo alguno para el consumo humano, imposibilitaban la formulación de soluciones apropiadas para la hidroponia.
El carbono y el nitrógeno de la biomasa microbiana (CBM y NBM) del suelo son bioindicadores que tienen el potencial de mostrar cambios en el suelo de los ecosistemas, y están condicionados por la ...humedad disponible en el suelo. Se evaluó como varían CBM, NBM y la respiración heterotrófica (RH) en función de la cantidad de humedad en suelos de la Estepa Magallánica Seca de Santa Cruz, Argentina. El ensayo consistió en 3 tratamientos: a) Control, conteniendo la precipitación normal caída, como testigo, b) Riego, equivalente a un aumento del 54% en las precipitaciones respecto a la media anual, y c) Sequía, con una disminución del 54% en las precipitaciones respecto a la media anual. Se estimó el CBM mediante el método de fumigación-extracción. Se encontraron diferencias significativas en el CBM entre los tratamientos, el riego obtuvo la mayor cantidad de CBM. Los valores fueron: 505,3 (±81,4), 406,7(±39,2) y 380,4 (±98,4) µg de C g-1 para riego, sequía y control, respectivamente. No se encontraron diferencias en el NBM entre los tratamientos, siendo los valores 93,3 (±13,5), 82,8 (±68,9) y 80,7 (±31,1) µg de N g-1 de suelo seco para sequía, control y riego, respectivamente. La RH diaria por su parte, presentó valores de 13,04 (±3,32), 11,17 (±1,47) y 10,60 (±1,29) mg C-CO2Kg-1 de suelo seco día-1 para el tratamiento control, riego y sequía, respectivamente. Solo el CBM evidenció un cambio relevante frente a la sequía, las demás variables no presentaron diferencias significativas. Los resultados denotan que la humedad es un factor importante para el C en BM, por lo que es importante seguir monitoreando y establecer como cambios en la precipitación alterar la biomasa microbiana en estos ambientes australes.
Fertile islands are an important determinant of ecosystem functioning in drylands. These resource‐rich patches are maintained by complex interactions among biotic and abiotic factors. Soil ...microorganisms are responsible for essential ecosystem processes and could affect the ability of fertile islands to capture and cycle nutrients, both directly and indirectly enhancing the fertile island effect. In this context, we aimed to evaluate the attributes of soil microbial communities (abundance and activity), elucidate key drivers of the fertile island effect and analyze relationships with a range of soil parameters (physicochemical). The soils under shrub canopies had higher values of microbial biomass carbon (MBC) and soil basal respiration (SBR) rates than soils from intercanopy spaces. However, no differences were observed in Soil Organic Carbon (SOC) or in fungal and bacterial abundances between the microhabitats. Soil nutrient stocks (NPK) and pH values had a positive correlation with MBC and SBR. Also, a positive correlation was observed for fungi abundance and the K content of the soil. We also observed a positive correlation between the bacterial abundance and soil N content. This study suggests that M. tridens can be considered a keystone species that generates fertility islands, critical for biodiversity and ecosystem functioning. The keystone role that M. tridens plays in this system underscores the importance of improving our understanding of these interactions (plant–soil‐microorganisms), especially important as drylands expand and aridity increases due to climate change in the second half of this century.
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