Alejandra Zuñiga - Academia.edu (original) (raw)

Papers by Alejandra Zuñiga

Journal of Hydrology and Hydromechanics, 2017

During hydrological research in a Chilean swamp forest, we noted a pattern of higher streamflows ... more During hydrological research in a Chilean swamp forest, we noted a pattern of higher streamflows close to midday and lower ones close to midnight, the opposite of an evapotranspiration (Et)-driven cycle. We analyzed this diurnal streamflow signal (DSS), which appeared mid-spring (in the growing season). The end of this DSS coincided with a sustained rain event in autumn, which deeply affected stream and meteorological variables. A survey along the stream revealed that the DSS maximum and minimum values appeared 6 and 4 hours earlier, respectively, at headwaters located in the mountain forests/ plantations than at the control point in the swamp forest. Et in the swamp forest was higher in the morning and in the late afternoon, but this process could not influence the groundwater stage. Trees in the mountain headwaters reached their maximum Ets in the early morning and/or close to midday. Our results suggest that the DSS is a wave that moves from forests high in the mountains towards ...

Intraespecific variation in drought resistance of Nothofagus antarctica

Environmental factors affect the spatial arrangement of survival and damage of outplanted Nothofa... more Environmental factors affect the spatial arrangement of survival and damage of outplanted Nothofagus dombeyi seedlings in the chilean andes Interciencia, vol. 34, núm. 2, febrero, 2009, pp. 100-105

Plant and Soil, 2020

Aims Gevuina avellana and Lomatia dentata are Proteaceae species from evergreen temperate forests... more Aims Gevuina avellana and Lomatia dentata are Proteaceae species from evergreen temperate forests, but only G. avellana can colonize nutrient deprived volcanic depositions. We hypothesized that under nutrient deprivation, G. avellana would present higher survival, physiological performance, and adjustment regarding cluster root (CR) formation and carboxylate exudation rate than L. dentata. Methods We evaluated relative growth rate, maximal photosynthetic rate, photochemical performance, nitrogen (N) and phosphorus (P) leaf concentrations, specific leaf area, photosynthetic P and N use efficiency (PPUE and PNUE), CR formation and carboxylate exudation rate. Plants were grown in a greenhouse, using recent volcanic substrate and watered with different nutrient Hoagland (H) solutions: modified full Hoagland, without P, without N, or tap water. Results Both species showed high survival. G. avellana exhibited higher growth rates (RGR), and higher CR number and biomass allocation under nutrient deprivation, but lower carboxylate exudation rates than L. dentata. Malate, oxalate and succinate were detected in root exudates of G. avellana but only oxalate in L. dentata. However, PPUE and PNUE were higher in L. dentata than in G. avellana. Conclusions Our hypothesis was not entirely accepted, CR formation was more "constitutive" in G. avellana, and composition of carboxylates was more diverse, with lower exudation rates than L. dentata. Moreover, L. dentata showed higher PNUE and PPUE, partly explained by thinner leaves. Different responses are related with edaphic conditions, where both species inhabit: more diverse to G. avellana and restricted to developed soils to L. dentata.

Journal of Plant Ecology, 2020

Bosque (Valdivia), 2019

Efecto de mallas raschel de colores en el crecimiento de plántulas de Eucalyptus globulus, Eucaly... more Efecto de mallas raschel de colores en el crecimiento de plántulas de Eucalyptus globulus, Eucalyptus nitens y Pinus radiata en condiciones de vivero Colored raschel mesh effect on growth of Eucalyptus globulus, Eucalyptus nitens and Pinus radiata seedlings under nursery conditions

Plant and Soil, 2019

Aims Southern South American Proteaceae can occupy soils that are rich in total phosphorus (P) bu... more Aims Southern South American Proteaceae can occupy soils that are rich in total phosphorus (P) but poor in available P (for example volcanic soils) thanks to their cluster roots (CR), which mine soil P. However, some southern South American Proteaceae occur in a wide range of soil nutrition. We hypothesized that CR formation and function are more responsive to nutrient soil availability in the widely-distributed Embothrium coccineum than in the narrowly-distributed Orites myrtoidea, which exclusively occurs in recent volcanic depositions. Methods Survival, growth rate, CR formation (number, biomass) and function (carboxylate exudation, phosphatase activity) were evaluated in seedlings of both species after five months of growth in either a volcanic or organic substrate. Results E. coccineum exhibited full survival in both substrates, but had significantly lower growth, higher CR formation, higher CR citrate and malate exudation, and higher phosphatase activity in the volcanic substrate. By contrast, O. myrtoidea had similar growth rate in both substrates but 73% lower survival and null CR formation in the organic compared to the volcanic substrate. Conclusions Variation in soil nutrient availability caused variation in growth and CR formation and function in a southern South American Proteaceae species of wider distribution, but not in a narrowly-distributed counterpart.

Journal of soil science and plant nutrition, 2018

The The hypothesis that Embothrium coccineum, a species able to solubilize P through cluster root... more The The hypothesis that Embothrium coccineum, a species able to solubilize P through cluster roots (CR) carboxylate exudation, makes P more available in volcanic depositions, thus facilitating the growth of other plant species such as the N-fixing Sophora cassioides was tested. In this work, seedlings of these two tree species were grown alone or co-cultivated for six months in greenhouse conditions with either pumice, a recent volcanic deposition with low P availability, or an organic commercial mix. Upon analyzing the aboveground growth of the two substrate treatments, we found no clear evidence of facilitation. Despite this, substrate type did influence the relative growth and some characteristics of CR and nodules. On the other side, the number of total soil bacteria, but not Rhizobium spp, was greater when E. coccineum and S. cassioidea were grown together than when only one species was grown alone. Nutritional parameters, such as the concentration of nitrogen (N) and phosphorous (P) in roots and total leaf protein content in leaves, indicated that the nutritional content of S. cassioides was greater when co-cultivated with E. coccineum in pumice. Specifically, co-cultivation tended to reduced P limitation and improved N acquisition by S. cassioides. Based on these results, our hypothesis is partially accepted.

Austral Ecology, 2017

Our goal was to establish the tolerance to flooding and drought of seedlings from a hydric gradie... more Our goal was to establish the tolerance to flooding and drought of seedlings from a hydric gradient of different seed sources to provide recommendations for forest restoration in the face of climate change. We used Drimys winteri var. chilensis, a tree species that grows from extreme arid zones to wetlands along Chile, as the study subject. We expected that seedlings of xeric origin would perform better in drought conditions than populations from moist environments, and vice versa for flooding tolerance. We collected D. winteri seeds from xeric, mesic and wet environments. Seedlings at two development stages were submitted to an extreme flooding and drought treatment during 2 or 4 months in a common garden. After the flooding and drought assays finished, the number of surviving and damaged seedlings, lenticels and adventitious root presence, height, new leaves and specific leaf area, shoot/root ratio, water potential and/or chlorophyll fluorescence (Fv/Fm), were recorded. We found that flooding and drought affected almost all the parameters studied negatively. The xeric population seedlings, at both development stages studied, were the most tolerant to the drought and, unexpectedly, also to the flooding treatment. We recommend restoring with seedlings of xeric origin especially in arid areas where sudden flooding is frequent, as occurs in the Andes Mountains. In the face of climate change, we recommend carrying out common garden and field studies before advising which population origin should be used for restoration, since they do not always respond in accordance with expected patterns of local adaptation.

Australian Journal of Botany, 2018

Deep shade and waterlogging are two common stressors affecting seedling performance in the unders... more Deep shade and waterlogging are two common stressors affecting seedling performance in the understorey of evergreen rainforests. It has been hypothesised that high levels of carbon storage confer shade- and waterlogging tolerances by preventing carbon limitation under such stresses. Whether the tolerance to both stresses is positively or negatively related remains unclear. To explore the role of carbon storage in the relationships of waterlogging and shade tolerance, we investigated the responses to waterlogging and the levels of carbon storage in two species pairs with contrasting shade tolerance: Embothrium coccineum J.R.Forst.&G.Forst. and Gevuina avellana Mol. (Proteaceae) and Nothofagus dombeyi (Mirb.) Oerst. and Nothofagus nitida (Phil.) Krasser (Nothofagaceae). We subjected seedlings to waterlogging or control conditions for 30 days and evaluated survival, relative growth rate (RGR), biomass distribution, leaf chlorophyll fluorescence (Fv/Fm), and concentrations of total solu...

Frontiers in plant science, 2018

Plants from the Proteaceae family can thrive in old, impoverished soil with extremely low phospho... more Plants from the Proteaceae family can thrive in old, impoverished soil with extremely low phosphorus (P) content, such as those typically found in South Western Australia (SWA) and South Africa. The South Western (SW) Australian Proteaceae species have developed strategies to deal with P scarcity, such as the high capacity to re-mobilize P from senescent to young leaves and the efficient use of P for carbon fixation. In Southern South America, six Proteaceae species grow in younger soils than those of SWA, with a wide variety of climatic and edaphic conditions. However, strategies in the nutrient use efficiency of Southern South (SS) American Proteaceae species growing in their natural ecosystems remain widely unknown. The aim of this study was to evaluate nutrient resorption efficiency and the photosynthetic nutrients use efficiency by SS American Proteaceae species, naturally growing in different sites along a very extensive latitudinal gradient. Mature and senescent leaves of the...

American Journal of Botany, 2017

A prevailing hypothesis in forest succession is that shade-tolerant species grow more slowly than... more A prevailing hypothesis in forest succession is that shade-tolerant species grow more slowly than shade-intolerant species, across light conditions, because they prioritize carbon (C) allocation to storage. We examined this hypothesis in a confamilial pair of species, including one of the fastest-growing tree species in the world (Eucalyptus globulus) and a shade-tolerant, slow-growing species (Luma apiculata). METHODS: Seedlings were subjected to one out of four combinations of light (high vs. low) and initial defoliation (90% defoliated vs. nondefoliated) for four months. Growth, C storage concentration in diff erent organs, leaf shedding, and lateral shoot formation were measured at the end of the experiment. KEY RESULTS: Eucalyptus globulus grew faster than L. apiculata in high light, but not in low light. Both species had lower C storage concentration in low than in high light, but similar C storage concentrations in each light condition. Defoliation had no eff ect on C storage, except in the case of the old leaves of both species, which showed lower C storage levels in response to defoliation. Across treatments, leaf shedding was 96% higher in E. globulus than in L. apiculata while, in contrast, lateral shoot formation was 87% higher in L. apiculata. CONCLUSIONS: In low light, E. globulus prioritized C storage instead of growth, whereas L. apiculata prioritized growth and lateral branching. Our results suggest that shade tolerance depends on effi cient light capture rather than C conservation traits.

Most Proteaceae in Mediterranean high-biodiversity ecosystems on old P-impoverish soils produce c... more Most Proteaceae in Mediterranean high-biodiversity ecosystems on old P-impoverish soils produce cluster roots (CR) that improve phosphorus (P) acquisition through carboxylate exudation. In contrast, South American Proteaceae show lower biodiversity and the role of CR is not fully understood. Embothrium coccineum, Orites myrtoidea and Gevuina avellana grow on volcanic soils in Chile. These soils show high total P concentrations, but low P availability. In order to study functioning of CR, we carried out two experiments to determine a) the effect of soil P availability on CR formation and b) the CR effect on P soil availability. Seedlings of E. coccineum and O. myrtoidea were grown in soils with contrasting P availability (high: organic; low: volcanic). Survival, growth rate, photosynthesis rate, cluster-root number, root phosphatase activity and root acid exudation were evaluated. Only E. coccineum showed complete survival in both soils. Both species had higher cluster-root numbers a...

Gayana. Botánica, 2012

Intraespecific variation in drought resistance of Nothofagus antarctica (G. Forst.) Oerst. (Notho... more Intraespecific variation in drought resistance of Nothofagus antarctica (G. Forst.) Oerst. (Nothofagaceae) Variación intraespecífica en resistencia a la sequía de Nothofagus antarctica (G. Forst.) Oerst.

Polar Biology, 2008

Deschampsia antarctica and Colobanthus quitensis are usually covered by snow from April to Novemb... more Deschampsia antarctica and Colobanthus quitensis are usually covered by snow from April to November. It is unknown whether the leaves survive ice encasement. This study proposes that day length influences sugar distribution in C. quitensis and that sugar accumulation favors re-growths after an ice encasement period. The objectives of this work were: (1) to study the effect of day length