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.
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.
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.
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.
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.
Functional traits determine plant co-occurrence more than environment or evolutionary relatedness in global drylands.
Soliveres, S., Maestre, F., Bowker, M., Torices, R., Quero, J., & García-Gómez, M., Cabrera, O., Ceag, A.P., Coaguila, D., Eldridge D.J., Espinosa, C.I., Hemmings, F., Monerris, J.J., Tighe, M., Delgado-Baquerizo, M., Escolar, C., García-Palacios, P., Gozalo, B., Ochoa, V., Blones, J., Derak, M., Ghiloufi, W., Gutiérrez, J.R., Hernández, R.M., Noumi, Z.
Plant–plant interactions are driven by environmental conditions, evolutionary relationships (ER) and the functional traits of the plants involved. However, studies addressing the relative importance of these drivers are rare, but crucial to improve our predictions of the effects of plant–plant interactions on plant communities and of how they respond to differing environmental conditions. To analyze the relative importance of – and interrelationships among – these factors as drivers of plant–plant interactions, we analyzed perennial plant co-occurrence at 106 dryland plant communities established across rainfall gradients in nine countries. We used structural equation modelling to disentangle the relationships between environmental conditions (aridity and soil fertility), functional traits extracted from the literature, and ER, and to assess their relative importance as drivers of the 929 pairwise plant–plant co-occurrence levels measured. Functional traits, specifically facilitated plants’ height and nurse growth form, were of primary importance, and modulated the effect of the environment and ER on plant–plant interactions. Environmental conditions and ER were important mainly for those interactions involving woody and graminoid nurses, respectively. The relative importance of different plant–plant interaction drivers (ER, functional traits, and the environment) varied depending on the region considered, illustrating the difficulty of predicting the outcome of plant–plant interactions at broader spatial scales. In our global-scale study on drylands, plant–plant interactions were more strongly related to functional traits of the species involved than to the environmental variables considered. Thus, moving to a trait-based facilitation/competition approach help to predict that: (1) positive plant–plant interactions are more likely to occur for taller facilitated species in drylands, and (2) plant–plant interactions within woody-dominated ecosystems might be more sensitive to changing environmental conditions than those within grasslands. By providing insights on which species are likely to better perform beneath a given neighbour, our results will also help to succeed in restoration practices involving the use of nurse plants.
Palabras claves: Aridity; Competition; Facilitation; Phylogenetic distance; Semi-arid; Soil fertility.
Referencia APA: Soliveres, S., Maestre, F., Bowker, M., Torices, R., Quero, J., & García-Gómez, M., Cabrera, O., Ceag, A.P., Coaguila, D., Eldridge D.J., Espinosa, C.I., Hemmings, F., Monerris, J.J., Tighe, M., Delgado-Baquerizo, M., Escolar, C., García-Palacios, P., Gozalo, B., Ochoa, V., Blones, J., Derak, M., Ghiloufi, W., Gutiérrez, J.R., Hernández, R.M., Noumi, Z. (2014). Functional traits determine plant co-occurrence more than environment or evolutionary relatedness in global drylands. Perspectives In Plant Ecology, Evolution And Systematics, 16(4), 164-173.
Seed predation by rodents results in directed dispersal of viable seed fragments of an endangered desert shrub.
Loayza, A., Carvajal, D., García-Guzmán, P., Gutierrez, J., & Squeo, F.
Seed predation and seed dispersal are important ecological processes with antagonistic effects on plant recruitment. In the southern edge of the Atacama Desert in Chile, Myrcianthes coquimbensis is an endangered, large-seeded, vertebrate-dispersed shrub that in the present-day has no known dispersers. Native rodents hoard and eat the seeds of M. coquimbensis but leave viable seed fragments at the hoarding sites; soil interspaces within rock outcrops where seedlings recruit. Here we examined whether rodents act as effective dispersers of M. coquimbensis by discarding viable seed fragments in sites suitable for recruitment. We simulated different levels of endosperm loss to determine if seedlings could develop from seed fragments. We assessed how frequently rodents discarded fragments, and the probability that these fragments produced seedlings. Finally, we compared emergence and seedling survival at the hoarding sites and in two other habitats where seeds arrive to evaluate the suitability of the hoarding sites. Seeds of M. coquimbensis developed seedlings even after 87% of their storage tissue was removed. Rodents left seed fragments in more than 50% of the trials; almost 60% of the discarded fragments produced seedlings. Seedlings did not emerge from open ground habitats, and emergence was higher under M. coquimbensis shrubs than in rock habitats. Survival of two-year-old seedlings was higher in rock habitats than under conspecific adult shrubs. Our results suggest that rodents may play a dual role in the recruitment dynamics of M. coquimbensis, acting simultaneously as seed predators and effective dispersers. Therefore, though seed predators impose costs, their net effect on plant fitness in this system—where dispersers of large-seeded species have been lost—is likely positive.
Palabras claves: Anachronism; Atacama; captive feeding trials; hoarding; Myrcianthes coquimbensis; rodent; seedling establishment.
Referencia APA: Loayza, A., Carvajal, D., García-Guzmán, P., Gutierrez, J., & Squeo, F. (2014). Seed predation by rodents results in directed dispersal of viable seed fragments of an endangered desert shrub. Ecosphere, 5(4), art43.