Rainfall, microhabitat, and small mammals influence the abundance and distribution of soil microorganisms in a Chilean semi-arid shrubland.
Aguilera, L., Armas, C., Cea, A., Gutiérrez, J., Meserve, P., & Kelt, D.
Patterns in rainfall and soil water availability are considered to be the main drivers governing arid and semiarid ecosystems. While the mechanisms by which water limits aboveground net primary production has been widely explored, few long-term studies have examined interactions between precipitation, soil resources, plant communities, and soil microbial communities; these may be critical to understanding soil biogeochemical cycles and above- and belowground interactions. We capitalized on a long-term biotic manipulation (exclusion of small mammal herbivores from replicate plots) and long-term variation in rainfall to assess how precipitation, small mammals, and shrub cover act directly and interactively to influence the spatial and temporal distribution of soil microorganisms, a key first step to understanding soil biogeochemical cycles. We measured the abundance of arbuscular mycorrhiza (AM), soil fungi, soil bacteria, and soil physicochemical characteristics over 10 consecutive years in a semiarid thorn scrub community in north–central Chile; we sampled two microhabitats (under shrub cover, and in open spaces between shrubs colonized by ephemeral plants), and in plots with or without the presence of native small mammals, the main herbivores in this environment. Annual rainfall ranged widely (11–356 mm) in this period and was the primary factor affecting abundance of AM root colonization and soil microbes. While the percentage of root length with AM was higher in dry compared to wet years, free-living soil bacteria and fungi were more abundant during wet years. All microorganisms were more abundant in the resource islands beneath the shrubs compared to open microhabitat between shrubs, although the relation between soil biota and the concentration of some particular nutrients was negative. These patterns were modulated by the presence of small mammals, which enhanced root colonization by AM fungi, particularly for ephemeral plants, but which were negatively associated with soil fungi abundance. The abundance of soil bacteria showed a more complex response to the presence of small mammals and was dependent on microhabitat and year. The spatial and temporal heterogeneity of soil resources and the activity of small mammals are important modulators of subterranean biotic responses to rainfall, the primary factor affecting soil microbiota abundance in this semiarid ecosystem.
Palabras claves: ENSO; LTSER; Plant-soil interactions; Mycorrhizal fungi; Soil filamentous fungi; Soil heterotrophic bacteria; Soil yeasts.
Referencia APA: Aguilera, L., Armas, C., Cea, A., Gutiérrez, J., Meserve, P., & Kelt, D. (2016). Rainfall, microhabitat, and small mammals influence the abundance and distribution of soil microorganisms in a Chilean semi-arid shrubland. Journal Of Arid Environments, 126, 37-46.
Shrub–ephemeral plants interactions in semiarid north-central Chile: Is the nurse plant syndrome manifested at the community level?.
Madrigal-González, J., Kelt, D., Meserve, P., Squeo, F., & Gutiérrez, J.
Models of plant–plant interactions suggest that nurse plants are critical for the maintenance of biodiversity and ecosystem functions in arid and semiarid lands. At the community scale, however, empirical support of this idea is limited and context-dependent. Following on a preliminary work which suggested that a dominant shrub in north-central Chile (Porlieria chilensis) had nurse plant effects, we tested the effects of this and two other shrubs (Adesmia bedwellii and Proustia cuneifolia) on community biomass production, species density, and species composition of ephemeral plants in the semiarid scrub of the Bosque Fray Jorge National Park (Chile) over four consecutive years. We tested for main and interactive effects of shrubs and precipitation on total biomass production and species density of ephemeral plant communities using Generalized Linear Mixed Models (GLMM). To analyze the effects of shrubs and precipitation on species composition we used Canonical Correspondence Analysis (CCA) and t-value biplot analysis. Total biomass production increased significantly with precipitation and was consistently lower beneath shrub canopies, particularly under A. bedwellii and P. chilensis. Although ephemeral plant species density generally was higher in open areas, differences between open and shrub canopy samples diminished with increasing precipitation. Finally, despite significant differences in ephemeral plant species composition between open areas and shrub canopies, we found no evidence of shrub species-specific effects. In conclusion, our results do not support a classical nurse plant syndrome in the semiarid scrub of the Bosque Fray Jorge National Park although shrubs can increase local diversity by favoring some ephemeral plant species that are absent in open areas.
Palabras claves: Ephemeral plant communities; Facilitation; Nurse plant syndrome; Precipitation; Semiarid scrub; Biomass production; Diversity.
Referencia APA: Madrigal-González, J., Kelt, D., Meserve, P., Squeo, F., & Gutiérrez, J. (2016). Shrub–ephemeral plants interactions in semiarid north-central Chile: Is the nurse plant syndrome manifested at the community level?. Journal Of Arid Environments, 126, 47-53.
Resource economics and coordination among above- and below-ground functional traits of three dominant shrubs from the Chilean coastal desert.
Morales, J., Squeo, F., Tracol, Y., Armas, C., & Gutierrez, J.
Plant functional traits determine how plants respond to environmental factors and influence ecosystem processes. Among them, root traits and analyses of relations between above and below-ground traits in natural communities are scarce. Methods we characterized a set of above- and below-ground traits of three dominant shrub species in a semiarid shrub-steppe that had contrasting leaf phenological habits (deciduous, semideciduous and evergreen). We analysed if there was coordination among above- and below-ground resource economics patterns: i.e. patterns of biomass allocation, construction costs and lifespan.
Palabras claves: Drought, functional diversity, mass fractions, root distribution, specific leaf area.
Referencia APA: Morales, J., Squeo, F., Tracol, Y., Armas, C., & Gutierrez, J. (2015). Resource economics and coordination among above- and below-ground functional traits of three dominant shrubs from the Chilean coastal desert. Journal Of Plant Ecology, 8(1), 70-78.
Energetic compensation is historically contingent and not supported for small mammals in South American or Asian deserts.
Kelt, D., Aliperti, J., Meserve, P., Milstead, W., Previtali, M., & Gutiérrez, J.
Understanding the nature of faunal assembly and community structure remains central to ecology. Research in North American deserts and some tropical forests provides evidence of energetic compensation and zero-sum dynamics, suggesting that species in some natural assemblages may be replaced with limited impact on ecosystem function. Experimental removal of a dominant small mammal (degu, Octodon degus) from replicate plots in semiarid coastal thorn-scrub habitat in north-central Chile revealed no evidence for energetic or functional compensation; energy consumption remained significantly lower on degu exclusions relative to control plots after 17 years of exclusion. This occurred in spite of the fact that the geographic species pools for South American sites generally are similar in size to those of most North American sites (mean and median number of species, 16.3 and 21.5 vs. 21.0 and 20, respectively). A macroecological assessment of energetically equivalent species at 394 arid sites in North America, the Gobi Desert, and South America indicated that the number of potentially equivalent species was lower than (Gobi) or similar to (South America) that found in North America, but when segregated by trophic groups, these faunas differed markedly. North American sites included large numbers of granivorous species whereas South American sites were dominated by omnivores. The more general trophic strategy in the latter sites would be expected to facilitate compensatory responses within local faunas, suggesting either that our site is anomalous or that other factors are governing local dynamics. Further research is needed to understand the generality of compensatory dynamics within natural systems, as this mechanism has direct relevance to discussions on ecological resilience in the face of ongoing environmental change.
Palabras claves: Community ecology; degu; deserts; energetic compensation; functional redundancy; historical contingency; north-central Chile; Octodon degus; species coexistence; species redundancy; trophic strategy; zero-sum dynamics.
Referencia APA: Kelt, D., Aliperti, J., Meserve, P., Milstead, W., Previtali, M., & Gutiérrez, J. (2015). Energetic compensation is historically contingent and not supported for small mammals in South American or Asian deserts. Ecology, 96(6), 1702-1712.
Assessing groundwater recharge in an Andean closed basin using isotopic characterization and a rainfall-runoff model: Salar del Huasco basin, Chile.
Uribe, J., Muñoz, J., Gironás, J., Oyarzún, R., Aguirre, E., & Aravena, R.
Closed basins are catchments whose drainage networks converge to lakes, salt flats or alluvial plains. Salt flats in the closed basins in arid northern Chile are extremely important ecological niches. The Salar del Huasco, one of these salt flats located in the high plateau (Altiplano), is a Ramsar site located in a national park and is composed of a wetland ecosystem rich in biodiversity. The proper management of the groundwater, which is essential for the wetland function, requires accurate estimates of recharge in the Salar del Huasco basin. This study quantifies the spatio-temporal distribution of the recharge, through combined use of isotopic characterization of the different components of the water cycle and a rainfall-runoff model. The use of both methodologies aids the understanding of hydrological behavior of the basin and enabled estimation of a long-term average recharge of 22 mm/yr (i.e., 15 % of the annual rainfall). Recharge has a high spatial variability, controlled by the geological and hydrometeorological characteristics of the basin, and a high interannual variability, with values ranging from 18 to 26 mm/yr. The isotopic approach allowed not only the definition of the conceptual model used in the hydrological model, but also eliminated the possibility of a hydrogeological connection between the aquifer of the Salar del Huasco basin and the aquifer that feeds the springs of the nearby town of Pica. This potential connection has been an issue of great interest to agriculture and tourism activities in the region.
Palabras claves: Groundwater recharge, Stable isotopes, Closed basinHigh plateau,Chile.
Referencia APA: Uribe, J., Muñoz, J., Gironás, J., Oyarzún, R., Aguirre, E., & Aravena, R. (2015). Assessing groundwater recharge in an Andean closed basin using isotopic characterization and a rainfall-runoff model: Salar del Huasco basin, Chile. Hydrogeol J, 23(7), 1535-1551
Increasing aridity reduces soil microbial diversity and abundance in global drylands.
Maestre, F., Delgado-Baquerizo, M., Jeffries, T., Eldridge, D., Ochoa, V., & Gozalo, B. Quero, J.L., García-Gómez, M., Gallardo, A., Ulrich, W., Bowker, M.A., Arredondo, T., Barraza-Zepeda, C., Bran, D., Florentino, A., Gaitán, J., Gutiérrez, J.R. et al.
Soil bacteria and fungi play key roles in the functioning of terrestrial ecosystems, yet our understanding of their responses to climate change lags significantly behind that of other organisms. This gap in our understanding is particularly true for drylands, which occupy ∼41% of Earth´s surface, because no global, systematic assessments of the joint diversity of soil bacteria and fungi have been conducted in these environments to date. Here we present results from a study conducted across 80 dryland sites from all continents, except Antarctica, to assess how changes in aridity affect the composition, abundance, and diversity of soil bacteria and fungi. The diversity and abundance of soil bacteria and fungi was reduced as aridity increased. These results were largely driven by the negative impacts of aridity on soil organic carbon content, which positively affected the abundance and diversity of both bacteria and fungi. Aridity promoted shifts in the composition of soil bacteria, with increases in the relative abundance of Chloroflexi and α-Proteobacteria and decreases in Acidobacteria and Verrucomicrobia. Contrary to what has been reported by previous continental and global-scale studies, soil pH was not a major driver of bacterial diversity, and fungal communities were dominated by Ascomycota. Our results fill a critical gap in our understanding of soil microbial communities in terrestrial ecosystems. They suggest that changes in aridity, such as those predicted by climate-change models, may reduce microbial abundance and diversity, a response that will likely impact the provision of key ecosystem services by global drylands.
Palabras claves: Bacteria, fungi, climate change, arid, semiarid .
Referencia APA: Maestre, F., Delgado-Baquerizo, M., Jeffries, T., Eldridge, D., Ochoa, V., & Gozalo, B. Quero, J.L., García-Gómez, M., Gallardo, A., Ulrich, W., Bowker, M.A., Arredondo, T., Barraza-Zepeda, C., Bran, D., Florentino, A., Gaitán, J., Gutiérrez, J.R. et al. (2015). Increasing aridity reduces soil microbial diversity and abundance in global drylands. Proceedings Of The National Academy Of Sciences, 201516684.
Seed bank of desert annual plants along an aridity gradient in the southern Atacama coastal desert.
Sotomayor, D. & Gutiérrez, J.
This study represents the first report on seed banks via direct counting for the southern part of the Atacama coastal desert. The level of aridity mainly determines annual plant communities in this desert, including exotic species. Their responses to the aridity level and soil nutrient content are species-specific, which allows for species co-existence under extreme abiotic conditions.
Palabras claves: Chile; Coastal desert; Ephemeral plants; Soil seed bank; Species co-existence.
Referencia APA: : Sotomayor, D. & Gutiérrez, J. (2015). Seed bank of desert annual plants along an aridity gradient in the southern Atacama coastal desert. J Veg Sci, 26(6), 1148-1158.
High hydrostatic pressure effect on chemical composition, color, phenolic acids and antioxidant capacity of Cape gooseberry pulp (Physalis peruviana L.).
Vega-Gálvez, A., López, J., Torres-Ossandón, M., Galotto, M., Puente-Díaz, L., Quispe-Fuentes, I., & Di Scala, K.
The aim of this study was to evaluate the effects of high hydrostatic pressure (HHP) at 300, 400 and 500 MPa/1, 3 and 5 min on nutritional and antioxidant properties of Cape gooseberry pulp after immediate application and after 60 days of storage. Proximal analysis, color, phenolic acids content and antioxidant capacity were determined. When analyzing the immediate effect of different treatments, a clear influence of HHP was observed in all the components of the proximal analysis. Regarding color, none of the three chromatic parameters showed significant differences with control leading to a minimum ΔE at 300 MPa/3 min. Changes in bound and free phenolic acids were evidenced after treatments. The maximum levels of TPC as well as antioxidant capacity were observed at 500 MPa/5 min. By the end of storage, all treated samples discolored leading to ΔE = 14.9 at 500 MPa/5 min. The profile of free and bound phenolic acids presented differences compared to Day 0. The antioxidant capacity by means of ORAC increased for treatments above 300 MPa/5 min indicating the effectiveness of these treatments for the production of functional products based on gooseberry pulp. For treatments above 400 MPa/3 min, molds and yeasts were not detected.
Palabras claves: High hydrostatic pressure; Antioxidant capacity; Phenolic compounds; Functional foods; Cape gooseberry.
Referencia APA: Vega-Gálvez, A., López, J., Torres-Ossandón, M., Galotto, M., Puente-Díaz, L., Quispe-Fuentes, I., & Di Scala, K. (2014). High hydrostatic pressure effect on chemical composition, color, phenolic acids and antioxidant capacity of Cape gooseberry pulp (Physalis peruviana L.). LWT - Food Science And Technology, 58(2), 519-526.
Geomorphologic Hazards And Disasters In The South American Andes.
Lebedeva, E., Mikhalev, D., Novoa Jerez, J., & Kladovschikova, M.
Geological-and-tectonic and physiographical features of the South American Pacific coast caused high intensity of morpholitogenesis including disaster-like way of some geomorphologic processes. Their complex, interaction, and intensity of conductive factors increase the risk of disaster. The Andean terrain morphology and rock lithology, precipitation type, and vegetation status are the main drivers that influence the character and high potential intensity of the geomorphologic processes. The enormous hydrometeorological events, frequent seismic shocks, volcanic eruptions, and human impact cause disasters development. A schematic map of disaster and hazardous processes for the Central sector of Andes was compiled. 16 areas with different spectra of the dominant catastrophic processes were identified. The South American Andes extension allows drawing out principles of geomorphologic disasters of these continental marginal mountains in various natural zones – from temporal to subequatorial latitudes, which are characterized by the individual unique heat-moisture rate, which governs both typical and extreme geomorphologic processes. An important feature of the study area is the asymmetric distribution of geomorphologic processes within coastal and inland slopes of the mountain system, as well as latitudinal zoning of this distribution.
Palabras claves: Geomorphologic hazard and disasters, South American Andes, intensity of geomorphologic processes, seismic and volcanic activity, unbalanced precipitation, mass movements of debris
Referencia APA: Lebedeva, E., Mikhalev, D., Novoa Jerez, J., & Kladovschikova, M. (2014). Geomorphologic Hazards And Disasters In The South American Andes. Ges, 7(1), 80-98.
Recession flow analysis as a suitable tool for hydrogeological parameter determination in steep, arid basins.
Oyarzún, R., Godoy, R., Núñez, J., Fairley, J., Oyarzún, J., Maturana, H., & Freixas, G
The analysis of baseflow recession of streamflow has been widely used in the evaluation of basin scale parameters because the required data are inexpensive to acquire, and the method is easy to use and generally gives good results. A literature review, however, shows that few studies have examined the applicability of recession methods to arid basins, particularly those set in mountainous landscapes. In this study, we apply a recession method that uses a non-dimensional theoretical curve matching technique to evaluate basin-wide, spatially-averaged hydraulic parameters for several watersheds (Culebrón, Punitaqui, Valle Hermoso, Hurtado, Chalinga, and Camisas), taking as case of study the Coquimbo Region, an arid, mountainous territory with steep topography in North-Central Chile. The studied watersheds range from 200 to 1500 km2. Results show hydraulic conductivity values in a reasonable range, i.e., 10−4 to 10−6 m s−1, rather close to those reported in the few existing studies for some of the basins. The method also yields estimates on the order of 10−5 for drainable porosity, with no major differences between the basins. The recession flow analysis provides a cost-effective approach to obtaining bulk hydrological parameters in arid and semi-arid steep basins such as those of the Coquimbo Region and elsewhere.
Palabras claves: Boussinesq equation; Coquimbo Region; Drainable porosity; Hydraulic conductivity; Hydrogeology.
Referencia APA: Oyarzún, R., Godoy, R., Núñez, J., Fairley, J., Oyarzún, J., Maturana, H., & Freixas, G. (2014). Recession flow analysis as a suitable tool for hydrogeological parameter determination in steep, arid basins. Journal Of Arid Environments, 105, 1-11
On the use of Standardized Drought Indices under decadal climate variability: Critical assessment and drought policy implications.
Núñez, J., Rivera, D., Oyarzún, R., & Arumí, J.
Since the recent High Level Meeting on National Drought Policy held in Geneva in 2013, a greater concern about the creation and adaptation of national drought monitoring systems is expected. Consequently, backed by international recommendations, the use of Standardized Drought Indices (SDI), such as the Standardized Precipitation Index (SPI), as an operational basis of drought monitoring systems has been increasing in many parts of the world. Recommendations for the use of the SPI, and consequently, those indices that share its properties, do not take into account the limitations that this type of index can exhibit under the influence of multidecadal climate variability. These limitations are fundamentally related to the lack of consistency among the operational definition expressed by this type of index, the conceptual definition with which it is associated and the political definition it supports. Furthermore, the limitations found are not overcome by the recommendations for their application. This conclusion is supported by the long-term study of the Standardized Streamflow Index (SSI) in the arid north-central region of Chile, under the influence of multidecadal climate variability. The implications of the findings of the study are discussed with regard to their link to aspects of drought policy in the cases of Australia, the United States and Chile.
Palabras claves: Multidecadal climate variability; Drought; Standardized Precipitation Index; Drought policy; Pacific Decadal Oscillation; Arid zones.
Referencia APA: Núñez, J., Rivera, D., Oyarzún, R., & Arumí, J. (2014). On the use of Standardized Drought Indices under decadal climate variability: Critical assessment and drought policy implications. Journal Of Hydrology, 517, 458-470.
Climate and soil attributes determine plant species turnover in global drylands.
Ulrich, W., Soliveres, S., Maestre, F., Gotelli, N., Quero, J., & Delgado-Baquerizo, M. Bowker, M.A., Eldridge, D.J., Ochoa, V., Gozalo, B., Valencia, E., Berdugo, M., Escolar, C., García-Gómez, M., Escudero, A., Prina, A., Alfonso, G., Arredondo, T., Bran, D., Cabrera, O., Cea, A.P., Chaieb, M., Contreras, J., Derak, M., Espinosa, C.I., Florentino, A., Gaitán, J., García Muro, V., Ghiloufi, W., Gómez-González, S., Gutiérrez, J.R., et al.
Geographical, climatic and soil factors are major drivers of plant beta diversity, but their importance for dryland plant communities is poorly known. The aim of this study was to: (1) characterize patterns of beta diversity in global drylands; (2) detect common environmental drivers of beta diversity; and (3) test for thresholds in environmental conditions driving potential shifts in plant species composition.
Palabras claves: Aridity; beta diversity; climatic variability; global environmental change; habitat filtering; latitudinal gradient; plant community assembly; regression analysis; soil fertility; spatial soil heterogeneity.
Referencia APA: Ulrich, W., Soliveres, S., Maestre, F., Gotelli, N., Quero, J., & Delgado-Baquerizo, M. Bowker, M.A., Eldridge, D.J., Ochoa, V., Gozalo, B., Valencia, E., Berdugo, M., Escolar, C., García-Gómez, M., Escudero, A., Prina, A., Alfonso, G., Arredondo, T., Bran, D., Cabrera, O., Cea, A.P., Chaieb, M., Contreras, J., Derak, M., Espinosa, C.I., Florentino, A., Gaitán, J., García Muro, V., Ghiloufi, W., Gómez-González, S., Gutiérrez, J.R., et al. (2014). Climate and soil attributes determine plant species turnover in global drylands. Journal Of Biogeography, 41(12), 2307-2319.