CEAZA
Antarctic macrolichen modifies microclimate and facilitates vascular plants in the maritime Antarctica – a reply to Casanova-Katny et al.
Molina-Montenegro, M., Torres-Díaz, C., & Gianoli, E.
In a current article in the Journal of Vegetation Science, Casanova-Katny et al. addressed a comment about an article by Molina-Montenegro et al., which demonstrated the climate modification induced by the macrolichen Usnea antarctica and its role as facilitator. They provided useful corrections concerning species identification and pointed out several issues that, in their view, weakened our study. They indicated that the role of U. antarctica as a facilitative species in the maritime Antarctica is merely philosophical and has no ecological relevance. In this commentary, we argue why these critiques are unsubstantial, and provide evidence that the macrolichen can modify the microclimate, ameliorating the harsh conditions prevailing in Antarctica, establishing positive interactions and eventually facilitating vascular species. Thus, the macrolichen U. antarctica would act as a ‘nurse species’, playing a key role in structuring the maritime Antarctic plant community.
Año: 2014
Palabras claves: Antarctica; Deschampsia Antarctica; Facilitation; Nurse effect; Positive interactions.
Referencia APA: Molina-Montenegro, M., Torres-Díaz, C., & Gianoli, E. (2014). Antarctic macrolichen modifies microclimate and facilitates vascular plants in the maritime Antarctica - a reply to Casanova-Katny et al. (2014). J Veg Sci, 25(2), 606-608.
Spatial variability in community composition on a granite breakwater versus natural rocky shores: Lack of microhabitats suppresses intertidal biodiversity.
Aguilera, M., Broitman, B., & Thiel, M.
Strong differences have been observed between the assemblages on artificial reefs and on natural hard-bottom habitats worldwide, but little is known about the mechanisms that cause contrasting biodiversity patterns. We examined the influence of spatial attributes in relation to both biogenic and topographic microhabitats, in the distribution and composition of intertidal species on both artificial and natural reefs. We found higher small-scale spatial heterogeneity on the natural reef compared with the study breakwater. Species richness and diversity were associated with a higher availability of crevices, rock pools and mussels in natural habitats. Spatial distribution of certain grazers corresponded well with the spatial structure of microhabitats. In contrast, the lack of microhabitats on the breakwater resulted in the absence of several grazers reflected in lower species richness. Biogenic and topographic microhabitats can have interactive effects providing niche opportunities for multiple species, explaining differences in species diversity between artificial versus natural reefs.
Año: 2014
Palabras claves: Artificial reefs; Biodiversity; Breakwater; Grazers; Spatial heterogeneity; Microhabitats.
Referencia APA: Aguilera, M., Broitman, B., & Thiel, M. (2014). Spatial variability in community composition on a granite breakwater versus natural rocky shores: Lack of microhabitats suppresses intertidal biodiversity. Marine Pollution Bulletin, 87(1-2), 257-268.
Geomorphology, internal structure, and successive development of a glacier foreland in the semiarid Chilean Andes (Cerro Tapado, upper Elqui Valley, 30°08′ S., 69°55′ W.).
Monnier, S., Kinnard, C., Surazakov, A., & Bossy, W.
We use geomorphological analysis, sedimentological survey, remote sensing, and ground penetrating radar (GPR) in order to understand the complex landform assemblage found in front of the Cerro Tapado glacier in the upper Elqui River catchment, semiarid Andes of Chile. The geomorphological analysis highlights prominent boundaries dividing the landform assemblage into (from the upper part to the lower part) an upper latero-frontal moraine complex, an upper debris-covered glacier, a lower debris-covered glacier, two rock glaciers, and a lower morainic complex. The sedimentological survey highlights the rather small size of the surface debris (in general < 20 cm) and the predominance of porphyritic rhyolite. Remote sensing data show that, between 1956 and 2010, considerable (> 400 m) receding of the glacier occurred, along with downslope displacements (dm–m·y− 1) of most of the landform units and a significant evolution of the thermokarst features on the debris-covered glaciers. Considerable surface lowering occurred in the upper part of the assemblage, while localized bulging is seen along the morphological boundaries in the lower units. The GPR profiles highlight spectacular internal structure in the upper debris-covered glacier with up to 80 m of buried ice. In the other landform units, the internal structure is less visible and more heterogeneous. The analysis of the radar wave velocity along the GPR profiles reveals the occurrence of air-filled and moist zones in the internal structure. The geomorphological assemblage is fundamentally characterized by its morphological, structural, and dynamical boundaries and defined as a young (probably < 2000 years) polygenetic construction with landform units having added to/overlapped one another. The rock glaciers do not derive from the present debris-covered glacier but preexist to it.
Año: 2014
Palabras claves: Landform assemblage; Debris-covered glacier; Rock glacier; Moraines; Ground-penetrating radar; Subsurface ice.
Referencia APA: Monnier, S., Kinnard, C., Surazakov, A., & Bossy, W. (2014). Geomorphology, internal structure, and successive development of a glacier foreland in the semiarid Chilean Andes (Cerro Tapado, upper Elqui Valley, 30°08′ S., 69°55′ W.). Geomorphology, 207, 126-140.
Formulation, calibration and validation of the DAIS model (version 1), a simple Antarctic Ice Sheet model sensitive to variations of sea level and ocean subsurface temperature.
Shaffer, G.
The DCESS (Danish Center for Earth System Science) Antarctic Ice Sheet (DAIS) model is presented. Model hindcasts of Antarctic ice sheet (AIS) sea level equivalent are forced by reconstructed Antarctic temperatures, global mean sea level and high-latitude, ocean subsurface temperatures, the latter calculated using the DCESS model forced by reconstructed global mean atmospheric temperatures. The model is calibrated by comparing such hindcasts for different model configurations with paleoreconstructions of AIS sea level equivalent from the last interglacial, the last glacial maximum and the mid-Holocene. The calibrated model is then validated against present estimates of the rate of AIS ice loss. It is found that a high-order dependency of ice flow at the grounding line on water depth there is needed to capture the observed response of the AIS at ice age terminations. Furthermore, it is found that a dependency of this ice flow on ocean subsurface temperature by way of ice shelf demise and a resulting buttressing decrease is needed to explain the contribution of the AIS to global mean sea level rise at the last interglacial. When forced and calibrated in this way, model hindcasts of the rate of present-day AIS ice loss agree with recent, data-based estimates of this ice loss rate.
Año: 2014
Palabras claves:
Referencia APA: Shaffer, G. (2014).Formulation, calibration and validation of the DAIS model (version 1), a simple Antarctic ice sheet model sensitive to variations of sea level and ocean subsurface temperature. Geoscientific Model Development, 7(4), 1803-1818.
Genetic diversity of Colobanthus quitensis across the Drake Passage.
Acuña-Rodríguez, I., Oses, R., Cortés-Vasquez, J., Torres-Díaz, C., & Molina-Montenegro, M.
The Drake Passage arises as a likely route for gene flow into Antarctica, as it is the shortest path between this continent and the rest of the world. Despite this, long-distance dispersion into Antarctica could be particularly complex for terrestrial biota. To compare the levels of genetic diversity between Antarctic and South American populations of the Antarctic pearlwort, Colobanthus quitensis, we conducted the first estimation of genetic diversity in this species using amplified fragment length polymorphism. Four populations across the Drake Passage were selected and their genetic composition was characterized. Differences among the levels of genetic diversity were found between the populations analysed as well as between their allelic identities. However, interestingly, their spatial distribution across the Drake Passage suggests a north-to-south gradient of increasing genetic diversity.
Año: 2014
Palabras claves: AFLP, Antarctic vascular plants, Colobanthus quitensis, genetic diversity.
Referencia APA: Acuña-Rodríguez, I., Oses, R., Cortés-Vasquez, J., Torres-Díaz, C., & Molina-Montenegro, M. (2014). Genetic diversity of Colobanthus quitensis across the Drake Passage. Plant Genetic Resources, 12(01), 147-150.
Effect of grazing on distribution and recovery of harvested stands of Lessonia berteroana kelp in northern Chile.
Oróstica, M., Aguilera, M., Donoso, G., Vásquez, J., & Broitman, B.
Understanding the ecological factors regulating exploited natural communities is important in establishing conservation and management strategies. Since the 1960s, artisanal fishermen have harvested up to 300000 dry tons yr-1 of wild populations of Lessonia spp. kelps. Adult kelps form a key habitat on the rocky shores of Chile, and benthic grazers regulate kelp populations by grazing or bulldozing microscopic and juvenile stages. To establish the role of the grazer assemblage in the recovery of kelp stands following harvesting, we conducted a manipulative experiment simulating artisanal kelp extraction and then manipulating the presence of grazers. We followed community succession and spatial distribution of L. berteroana recruits in manipulated and control rocky shore platforms for ca. 12 mo. Inter-individual distances of recruits and spatial autocorrelation analyses showed that the presence of grazers determined a patchy distributional pattern of L. berteroana. The aggregated spatial pattern of kelp recruits in the presence of grazers was followed by numerous coalescence events between small holdfasts, but no coalescence events were observed between recruits in the grazer removal areas. Our results suggest that grazing and recruit coalescence play an important role in the recovery of kelp stands following artisanal harvesting. Incorporating these processes into conservation and management strategies may bolster current strategies, which are based solely on the spatial structure of kelp stands.
Año: 2014
Palabras claves: Algae-herbivore, Harvesting, Grazers, Kelp communities, Spatial structure.
Referencia APA: Oróstica, M., Aguilera, M., Donoso, G., Vásquez, J., & Broitman, B. (2014). Effect of grazing on distribution and recovery of harvested stands of Lessonia berteroana kelp in northern Chile. Marine Ecology Progress Series, 511, 71-82.
Unusual forest growth decline in boreal North America covaries with the retreat of Arctic sea ice.
Girardin, M., Guo, X., De Jong, R., Kinnard, C., Bernier, P., & Raulier, F.
The 20th century was a pivotal period at high northern latitudes as it marked the onset of rapid climatic warming brought on by major anthropogenic changes in global atmospheric composition. In parallel, Arctic sea ice extent has been decreasing over the period of available satellite data records. Here, we document how these changes influenced vegetation productivity in adjacent eastern boreal North America. To do this, we used normalized difference vegetation index (NDVI) data, model simulations of net primary productivity (NPP) and tree-ring width measurements covering the last 300 years. Climatic and proxy-climatic data sets were used to explore the relationships between vegetation productivity and Arctic sea ice concentration and extent, and temperatures. Results indicate that an unusually large number of black spruce (Picea mariana) trees entered into a period of growth decline during the late-20th century (62% of sampled trees; n = 724 cross sections of age >70 years). This finding is coherent with evidence encoded in NDVI and simulated NPP data. Analyses of climatic and vegetation productivity relationships indicate that the influence of recent climatic changes in the studied forests has been via the enhanced moisture stress (i.e. greater water demands) and autotrophic respiration amplified by the declining sea ice concentration in Hudson Bay and Hudson Strait. The recent decline strongly contrasts with other growth reduction events that occurred during the 19th century, which were associated with cooling and high sea ice severity. The recent decline of vegetation productivity is the first one to occur under circumstances related to excess heat in a 300-year period, and further culminates with an intensifying wildfire regime in the region. Our results concur with observations from other forest ecosystems about intensifying temperature-driven drought stress and tree mortality with ongoing climatic changes.
Año: 2014
Palabras claves: Bayesian; Canada; carbon; climate change; multivariate adaptive regression splines; process-based model 3PG; Quebec; regime shifts; satellite imagery; wavelet coherency.
Referencia APA: Girardin, M., Guo, X., De Jong, R., Kinnard, C., Bernier, P., & Raulier, F. (2014). Unusual forest growth decline in boreal North America covaries with the retreat of Arctic sea ice. Glob Change Biol, 20(3), 851-866.
Rivers as a source of marine litter – A study from the SE Pacific.
Rech, S., Macaya-Caquilpán, V., Pantoja, J., Rivadeneira, M., Jofre Madariaga, D., & Thiel, M.
Composition and abundance of persistent buoyant litter (plastics, polystyrene and manufactured wood) were investigated at riversides and on adjacent coastal beaches of four rivers flowing into the SE Pacific Ocean. Persistent buoyant litter made up the main share of litter at riversides (36–82%) and on coastal beaches near the river mouths (67–86%). The characteristic litter composition of each river is attributable to human influences along its course. Riverine litter items were deposited to both sides of the river mouths on coastal beaches, and their abundance generally declined with distance from the river mouth. However, maximum litter accumulations were often found on beaches north of the river mouth, suggesting a long-term influence of the prevailing equatorward low-level jet along the Chilean coast. The results confirm that riverine transport has an important impact on litter abundances on coastal beaches.
Año: 2014
Palabras claves: Riverine litter; Litter composition; Litter abundance; Marine beaches; Riversides.
Referencia APA: Rech, S., Macaya-Caquilpán, V., Pantoja, J., Rivadeneira, M., Jofre Madariaga, D., & Thiel, M. (2014). Rivers as a source of marine litter – A study from the SE Pacific. Marine Pollution Bulletin, 82(1-2), 66-75
Environmental tolerance of the two invasive species Ciona intestinalis and Codium fragile: their invasion potential along a temperate coast.
Jofré Madariaga, D., Rivadeneira, M., Tala, F., & Thiel, M.
Ciona intestinalis and Codium fragile are among the most successful invasive species in marine systems worldwide, and they are currently in the process of expanding their distributional ranges along the Chilean coast. Herein we evaluated whether their tolerance to a wide range of environmental conditions contributes to the invasion potential of these two species. To examine the environmental tolerance and performance (e.g., growth) of these non-indigenous species, unifactorial experiments (8–10 days) were conducted with different environmental factors (solar radiation, salinity and temperature). Based on the results, the potential risk of invasion along the Chilean coast was evaluated for both species using a mechanistic niche modeling approach. Both species can tolerate extensive ranges of the abiotic factors salinity and temperature, with C. intestinalis being more tolerant to cold-temperate waters. Also, C. intestinalis was more susceptible to high light intensities than C. fragile. These results confirm those of other experiments, and the outcome of the niche modeling shows that both species can potentially invade most regions of the Chilean coast with the exception of the Magellan region. The results suggest that physiological capacity to tolerate and perform in a wide range of physical conditions is a pre-requisite for successful invasions by littoral biota, but predation and possibly competitive exclusion can slow down the invasion success of C. intestinalis, which in contrast to C. fragile, is consumed by many benthic predators. Sexual and asexual reproduction as well as buoyancy of its thalli further contribute to the dispersal and colonization success of C. fragile. Based on these considerations, it is concluded that the invasion risk of C. fragile along the Chilean coast is substantially higher than that of C. intestinalis.
Año: 2014
Palabras claves: Invasive species, Environmental tolerance, Chilean coastInvasion risk, Niche modeling.
Referencia APA: Jofré Madariaga, D., Rivadeneira, M., Tala, F., & Thiel, M. (2014). Environmental tolerance of the two invasive species Ciona intestinalis and Codium fragile: their invasion potential along a temperate coast. Biol Invasions, 16(12), 2507-2527.
Albedo variations and the impact of clouds on glaciers in the Chilean semi-arid Andes.
Abermann, J., Kinnard, C., & MacDonell, S.
Albedo variations are presented at two on-glacier sites in the semi-arid Andes, Chile, with >3 years of continuous measurements. Although <2 km apart and at similar elevations, the sites show significantly different albedo cycles. Whereas Toro 1 exhibits a clear seasonal cycle, Guanaco reveals a more complicated pattern, as exposed ice can occur in any month of the year. Daily albedo values are as low as 0.18 for debris-covered Toro 1, while minima are higher on Guanaco (0.38). A method is presented to discern cloud-free from cloudy conditions using measured incoming shortwave radiation only. A cloud climatology is provided showing very low cloudiness values. We see that effective cloud cover relates inversely to cloud occurrence (i.e. either more but thin or fewer but thick clouds). The cloud-free diurnal albedo cycle is pronounced, with lowest values around noon. Clouds increase albedo by 0.04 as a median hourly value, and 0.20 for the 95% quantile. There is a positive relationship between effective cloud cover and resulting albedo rise. Calculations as to whether the diurnal albedo cycle or the effect of clouds on albedo should be considered in energy-balance estimations show that the former is necessary whereas the latter can be neglected in the semi-arid Andes.
Año: 2014
Palabras claves: Energy Balance; Glacier Mass Balance; Glacier Meteorology; Ice/atmosphere Interactions
Referencia APA: Abermann, J., Kinnard, C., & MacDonell, S. (2014). Albedo variations and the impact of clouds on glaciers in the Chilean semi-arid Andes. Journal Of Glaciology, 60(219), 183-191.
Climatic drivers of tree growth in a swamp forest island in the semiarid coast of Chile.
Peña, M., Barichivich, J., & Maldonado, A.
Isolated patches of swamp forests surrounded by xerophytic vegetation occur along the semiarid coast of Chile. Supported by shallow groundwater, these unique ecosystems have endured a long-term aridity trend during the Holocene and historical land use change. In this study, we investigated the patterns and climate drivers of annual tree growth in a coastal swamp dominated by the hygrophilous tree Myrceugenia exsucca. A tree-ring width chronology spanning the period 1864–2007 was developed and compared with long-term precipitation, temperature and soil moisture dynamics. There is a general lack of significant climate response during the earlier part of the 20th century, but a time-dependent positive growth response to temperature and moisture variability took place following partial drainage of the forest (1930s). Furthermore, a shift from a concurrent to a lagged growth response to moisture occurred around 1980, coinciding with increased frequency of ENSO-related moisture extremes. These results suggest that the ecological functioning of swamp forests in this region is very resilient to short-term climate variability, but even slight drainage disturbance can trigger very dynamic growth responses to climate variability. The degree of anthropogenic disturbance of these ecosystems will likely influence their response to projected increases in regional aridity during the coming decades.
Año: 2014
Palabras claves: Dendrochronology; Drought; ENSO; Groundwater; Swamp forest.
Referencia APA: Peña, M., Barichivich, J., & Maldonado, A. (2014). Climatic drivers of tree growth in a swamp forest island in the semiarid coast of Chile. Journal Of Arid Environments, 109, 15-22.
Geographical Variation of Shell Thickness in the Mussel Perumytilus purpuratus Along the Southeast Pacific Coast.
Briones, C., M.m., Rivadeneira, M., Fernández, R., Guiñez.
At broad geographical scales, the variation in bivalve shell thickness can be modulated by environmental factors that vary with latitude, such as sea surface temperature (SST), seawater pH, or calcium carbonate availability. Mussels usually form multilayered beds, and shell thickness is also expected to be affected by density and layering due to intraspecific competition. In this work, we explored the geographical variation of shell thickness in the intertidal mussel Perumytilus purpuratus between 18° and 42°S along the southeastern Pacific coast. We tested the hypothesis that there was a positive relationship between shell thickness and SST, and then we explored other variables that could have an effect on thickness, such as density, number of layers, and others environmental variables (pH and calcite concentration). The expected positive linear relationship between shell thickness and sea surface temperature was not found, but when the other population variables were included in the analysis, an unexpected inverse SST-thickness relationships appeared as significant, probably because this species could be adapted to colder and more acid seawater as are those of the tips of South America. Thickness was also negatively affected by density, which was expected for a gregarious species howing high intraspecific competition.Finally, our results highlight the importance of including density and crowding effects when macroscale patterns are explored, particularly in gregarious species, since these patterns could also be modulated by density-dependent processes, which might then override latitudinal trends of shell thickness when they are not included in the analyses.
Año: 2014
Palabras claves:
Referencia APA: Briones, C., M.m., Rivadeneira, M., Fernández, R., Guiñez. (2014). Geographical Variation of Shell Thickness in the Mussel Perumytilus purpuratus Along the Southeast Pacific Coast. Biol. Bull. 227: 221–231.