ULS-CEAZA
Biotic interactions and community dynamics in the semiarid thorn scrub of Bosque Fray Jorge National Park, north-central Chile: A paradigm revisited.
Meserve, P., Kelt, D., Gutiérrez, J., Previtali, M., & Milstead, W.
In 1989, we initiated a long-term field experiment in a semiarid thorn scrub community in north-central Chile. We posited that biotic interactions, particularly predation, interspecific competition, and herbivory assumed a primary top-down role in affecting small mammals and annual plants here. Using a multi-factorial design we selectively excluded vertebrate predators (principally carnivores and raptors) and a large small mammal herbivore, the degu (Octodon degus), from replicated 0.56 ha exclosures located in a valley near the coast in Bosque Fray Jorge National Park. Evidence initially supported effects of predator exclusion on O. degus but not for other small mammals in the assemblage (e.g., Phyllotis darwini, Abrothrix olivaceus). Subsequent years of monitoring have documented that predation has temporary effects on degu numbers, but that populations of this and other small mammals are much more strongly influenced by environmental bottom-up factors (i.e., rainfall). Further, our experimental manipulation has provided no evidence for negative interspecific competition effects on numbers of any small mammal in this assemblage. Degu exclusions, however, have had negative indirect effects on exotic annuals; native annuals appear to outcompete exotics especially during drought years The effect is magnified in all-small mammal exclusions. Since about 2002, selective exclusions of lagomorphs and small mammals have resulted in changes in cover of some perennial shrubs. Also notable has been a fundamental shift in the small mammal composition following the last major El Niño Southern Oscillation (ENSO) event in 2000–2002; degus now comprise a majority of small mammal biomass in the assemblage, and their numbers have become more stable and less temporally variable. This appears to have been caused by a shift in rainfall periodicity from strong interannual fluctuations in response to periodic ENSOs, to a more equitable pattern with more consistent annual rainfall. This represents one of the first documented cases of system-wide biotic phase shifts to a relatively modest change in rainfall regime. This may be indicative of ongoing climate change in the Chilean semiarid region, and we expect that further changes in the community will occur if those trends continue.
Año: 2016
Palabras claves: Long-term studies; Population; Community ecology; Small mammals; Chile.
Referencia APA: Meserve, P., Kelt, D., Gutiérrez, J., Previtali, M., & Milstead, W. (2016). Biotic interactions and community dynamics in the semiarid thorn scrub of Bosque Fray Jorge National Park, north-central Chile: A paradigm revisited. Journal Of Arid Environments, 126, 81-88.
Where does the water go? Understanding geohydrological behaviour of Andean catchments in south-central Chile.
Arumí, J., Maureira, H., Souvignet, M., Pérez, C., Rivera, D., & Oyarzún, R.
Upper Diguillín and Renegado are two neighbouring Andean basins of south-central Chile, with different specific discharges that cannot be explained solely by their difference in size. To address this issue, this study considers three separate but complementary approaches: (a) long-term analysis of rainfall and flow trends; (b) determination of hydrogeological properties at the watershed scale; and (c) analysis of the temporal evolution of groundwater storage. First, a trend test detected a statistically significant discharge decrease for Renegado in summer, unrelated to a coincidental precipitation trend, which seems to be associated with an increased use of water in that season related to tourism activity in the area. Second, there were no important differences in hydraulic conductivity or drainable porosity between the two study areas. However, it was found that there is a long-term negative trend in groundwater storage for Renegado; that is, water that contributes to the lower Diguillín streamflow through numerous springs.
Año: 2016
Palabras claves: Basin-scale hydrology, Brutsaert analysis, trend analysis, baseflow.
Referencia APA: Arumí, J., Maureira, H., Souvignet, M., Pérez, C., Rivera, D., & Oyarzún, R. (2016). Where does the water go? Understanding geohydrological behaviour of Andean catchments in south-central Chile. Hydrological Sciences Journal, 1-12.
Twenty-five years of research in the north-central Chilean semiarid zone: The Fray Jorge Long-Term Socio-Ecological Research (LTSER) site and Norte Chico.
Armas, C., Gutiérrez, J., Kelt, D., & Meserve, P.
This special issue of the Journal of Arid Environments includes papers addressing diverse aspects of the abiotic and biotic environment of the Mediterranean semiarid drylands in north-central Chile (29–32°S, the Norte Chico), as well as a review and recent research findings on one of the longest-running field experiments in global drylands, the Fray Jorge Long-Term Socio-Ecological Research site (LTSER), located in Bosque Fray Jorge National Park. The Fray Jorge LTSER started in 1989 and has become a sentinel site for monitoring effects of resource variability, climate change, and extreme climatic events on diverse groups including plants, small mammals, and their predators, and more recently arthropods and songbirds. This special issue takes a multidisciplinary approach that includes reviews, new data, and research ideas grouped into two sections: (i) climate, vegetation and avifauna of the national park and semiarid drylands of north-central Chile, and; (ii) focal papers summarizing some of the research performed in Fray Jorge LTSER. This effort include the long-term monitoring of different aspects and components of the biotic community: e.g., soil microorganisms, shrub and ephemeral plant species, arthropods, native small mammals (including the main herbivores in the system), and their vertebrate predators; analysis of the interactions among these components across trophic levels; and finally, analyses of the biotic responses to rainfall, the main abiotic factor governing these communities. This special issue ends with a review of the research performed over 25 years on biotic interactions including predation, herbivory, and interspecific competition and community dynamics in the semiarid Fray Jorge LTSER ( Meserve et al., 2016a).
Año: 2016
Palabras claves:
Referencia APA: Armas, C., Gutiérrez, J., Kelt, D., & Meserve, P. (2016). Twenty-five years of research in the north-central Chilean semiarid zone: The Fray Jorge Long-Term Socio-Ecological Research (LTSER) site and Norte Chico. Journal Of Arid Environments, 126, 1-6.
Vegetation of Bosque Fray Jorge National Park and its surrounding matrix in the Coastal Desert of north-central Chile.
Squeo, F., Loayza, A., López, R., & Gutiérrez, J.
Within its almost 9000 ha, Bosque Fray Jorge National Park (BFJNP) possesses a natural mosaic of vegetation formations dominated by thorn scrub (63.3% of the park) and scrub with cacti and other succulents (34.1%); these formations, whose plant covers are above 40%, are representative of the Coastal Desert vegetation. Additionally, BFJNP has 230 ha (2.6%) of a relict fog forest. This unique combination of vegetation formations, partly explains the high plant species richness of the park. We discuss the climatic and topo-edaphic factors associated with each type of vegetation formation.
Compared to BFJNP, the surrounding vegetation matrix shows evidence of changes in both the dominant vegetation and their plant covers; moreover, it is floristically depauperate relative to the park. This territory also includes agricultural land and plantations of non-native shrubs, as well as goat herding and small, inter-dispersed human settlements. Its main land cover types are: scrub (50%), scrub with succulents (34%), agricultural land (8%), secondary prairies (3.5%), and plantations of non-native shrubs (1.6%). Approximately 22% of this area presents high levels of anthropization. Additionally, two wind farms (217 wind turbines) have begun operating within the vicinity of BFJNP within the past two years.
BFJNP provides more than a mere representative sample of the current vegetation; it constitutes a remnant of the natural vegetation that once dominated the Coastal Desert before European colonization. Whereas the relict fog forest has been historically isolated, the desert vegetation is increasingly losing connectivity outside the park. We discuss the consequences of this isolation in terms of long-term maintenance of biodiversity. We argue that plant communities at BFJNP are the best available model for ecological restoration projects in this region of Chile.
Año: 2016
Palabras claves: Plant diversity; Plant community; Land cover; Relict fog forest; Conservation.
Referencia APA: Squeo, F., Loayza, A., López, R., & Gutiérrez, J. (2016). Vegetation of Bosque Fray Jorge National Park and its surrounding matrix in the Coastal Desert of north-central Chile. Journal Of Arid Environments, 126, 12-22.
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.
Año: 2016
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.
Año: 2016
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.
Bet-hedging strategies of native and exotic annuals promote coexistence in semiarid Chile.
Jiménez, M., Gaxiola, A., Armesto, J., González-Browne, C., Meserve, P., & Kelt, D., Gutierrez, J.R., Jaksic, F.M.
Scientists are increasingly interested in the evolutionary responses of organisms to unpredictable, variable, and extreme climate changes. In semiarid environments, inter-annual variability in the frequency and amount of rainfall affects both the growth and recruitment of plant species, especially annuals. In these inherently variable environments, individual selection should favor demographic responses that spread the risk of mortality over time and enhance long-term reproductive success (i.e., bet-hedging strategies). However, the same processes that allow the persistence and recruitment of native species could facilitate the introduction and establishment of exotics. We assessed whether native and exotic annuals in semiarid Chile displayed similar or contrasting bet-hedging traits, and discuss mechanisms of coexistence of both types of species and their demographic variation under interannual rainfall variability driven by El Niño Southern Oscillation (ENSO). We analyzed a proxy of long-term fitness, i.e., the variability of seed density over 17 years, for the two most common native and two exotic annual plant species present in the study area. We experimentally tested whether the quality of the maternal environment (soil water supply in a given year) had an extended effect (e.g. the next year) on the proportion of seed germination or on the mean and/or variability of seed size and seed dormancy. Results showed that native and exotic species in this annual plant assemblage displayed contrasting bet-hedging strategies as evolutionary responses to variable rainfall. Although rainfall variability promotes the evolution of bet-hedging strategies, the nature of these strategies varies across species, presumably to minimize competitive exclusion. In semiarid Chile, the success of two exotic ephemerals that are components of a diverse community of native annual species seems to reflect bet-hedging germination strategies that complement rather than compete with those expressed in dominant natives.
Año: 2016
Palabras claves: Bromus; Coexistence; Germination; Long-term fitness; Storage effect.
Referencia APA: http://dx.doi.org/10.1016/j.jaridenv.2015.10.014
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.
Año: 2015
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.
Año: 2015
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.
Año: 2015
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.
Año: 2015
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.
Año: 2015
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.