Publicaciones
Nurse effect and soil microorganisms are key to improve the establishment of native plants in a semiarid community.
Molina-Montenegro, M., Oses, R., Atala, C., Torres-Díaz, C., Bolados, G., & León-Lobos, P.
Facilitation by the nurse effect can occur through an amelioration of environmental stress. Plant-microorganism interaction, however, is another key facilitation mechanism of the nurse effect, but is by far the least documented. Here we tested if microclimatic mitigation and soil microorganisms isolated from the root-zone of the nurse shrub Porlieria chilensis can increase the establishment of other native plants in a semiarid community. We conducted field and greenhouse experiments to evaluate the direct and indirect effects of the presence of P. chilensis on the survival and growth of three native plants. In the field experiment, we compared the survival and growth of transplanted individuals beneath nurses and outside of them in pots filled with soil from both microsites (beneath and outside nurses). Finally, in the greenhouse experiment we grew native plants in soil taken from both microsites (below and outside nurses) and with and without soil microorganisms (sterilization process). We found a clear and significant nurse effect of P. chilensis on the tested species through of amelioration of climatic (air temperature, soil moisture, and solar radiation) and edaphic (nitrogen availability) conditions, increasing the performance of these native species. Moreover, performance and establishment were enhanced when soil was kept with microorganisms. Thus, nurse effect mediated by microclimatic amelioration, edaphic improvement and presence of soil microorganisms could be key mechanisms to increase the establishment of native plant species in semiarid communities of central Chile.
Año: 2016
Palabras claves: Nurse effect; Facilitation; Chile; Microorganisms; Symbiosis; Positive interactions.
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.
El Niño Southern Oscillation drives conflict between wild carnivores and livestock farmers in a semiarid area in Chile.
Acosta-Jamett, G., Gutiérrez, J., Kelt, D., Meserve, P., & Previtali, M.
The warm phase of El Niño-Southern Oscillation (ENSO) events results in greatly elevated rainfall in north-central Chile, with dramatic effects on small mammals and vertebrate carnivore abundances. In ensuing cool phases of ENSO, plant cover decreases, followed by small mammal densities, in turn affecting the resource availability for their predators. Wild carnivores such as foxes are one of the main predators of small mammals; when the latter decline, foxes could exhibit functional responses, increasing their consumption of domestic livestock. To our knowledge, the influence of native prey abundance on livestock predation has not been assessed. We hypothesize that periods of scarce native prey increases conflicts between carnivores and farmers outside protected areas, especially during drought years. From 1990 to 2005 we used live trapping to determine monthly density of small mammals in a national park (Bosque Fray Jorge National Park, BFJNP) in north-central Chile; rainfall was also monitored. We calculated an index of predation as the number of sheep predated by foxes annually on one farm (encompassing ca. 45,000 ha) located in the vicinity of BFJNP. Path analysis was carried out to assess factors influencing sheep predation by wild foxes. Factors included precipitation and small mammal density. Small mammal density correlated positively with two years moving average of rainfall. Sheep predation by foxes increased after of two years of low rainfall. Our findings suggest that wild carnivores employ functional responses in response to varying prey availability, shifting from wild to domestic prey during periods of drought, which could have important conservation and management implications.
Año: 2016
Palabras claves: Wild foxes; Livestock predation; Drought; Coquimbo region; Chile.
Patterns in arthropod abundance and biomass in the semiarid thorn scrub of Bosque Fray Jorge National Park, north-central Chile: A preliminary assessment.
Meserve, P., Vásquez, H., Kelt, D., Gutiérrez, J., & Milstead, W.
In 2003, we initiated a sampling protocol for arthropods as part of long-term field experiment in a semiarid thorn scrub community in north-central Chile. We utilized pitfall and Malaise traps to sample terrestrial and volant arthropods, respectively. Inventories were conducted for 4 days and nights monthly. We posited that arthropod abundance and biomass would track environmental changes such as high rainfall often due to El Niño Southern Oscillations (ENSOs). Peaks in both abundance and biomass for terrestrial and volant arthropods were in similar months (spring–early summer; August–November); arthropods also tracked high rainfall years in 2004, 2006, and 2011, due mostly to increases in a few dominant groups, i.e., tenebrionid beetles (Coleoptera) in terrestrial sampling, and moths (Lepidoptera: Noctuidae, microlepidoptera) in aerial sampling. However, the same groups increased dramatically in 2008 which was a below-average rainfall year. Numerical decreases in late summer-fall months (January–April) were more abrupt for terrestrial arthropods than for volant ones. Both terrestrial and volant arthropods reached their lowest levels in winter months (June–July). Some evidence suggests long-term shifts in the composition of volant taxa. Arthropods likely are important prey items for insectivorous reptiles (i.e., lizards), birds, and an insectivorous small mammal, the elegant mouse opossum (Thylamys elegans), and future efforts are being directed towards examining the evidence for correlated changes in those consumers with arthropod abundance and biomass.
Año: 2016
Palabras claves: Long-term studies; Climate change; Arthropods; Semiarid systems; Chile.
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.
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.
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.
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.
Climatic characteristics of the semi-arid Coquimbo Region in Chile.
Montecinos, S., Gutiérrez, J., López-Cortés, F., & López, D.
The climate of the Coquimbo Region, north-central Chile is driven by atmospheric, oceanic and orographic factors. The southeast Pacific anticyclone, the cold Humboldt Current and the rugged topography that characterize the zone, determine thermally induced wind regimes and the formation of low stratocumulus along the coastline. Low precipitation and high solar radiation cause important climatic altitudinal gradients, especially on temperature and humidity, thus different climatic areas can be identified in the region. We summarized the general climatic characteristics of the study area and analyzed meteorological data to understand the behavior of the environmental variables. We used mesoscale modeling to evaluate the spatial characteristics of the mean air temperature, humidity and wind. These atmospheric variables present a strong elevation gradient. The particular topographic characteristics of the region favor the development of a thermally induced wind regime, where land and sea breezes and valley winds are observed.
Año: 2016
Palabras claves: Atmospheric modeling; Semi-arid zones; Desert.
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
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