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Fajardo A.,Austral University of Chile | Piper F.I.,Austral University of Chile | Piper F.I.,Institute Ecologia y Biodiversidad IEB | Pfund L.,University of Basel | And 2 more authors.
New Phytologist | Year: 2012

In low temperature-adapted plants, including treeline trees, light-saturated photosynthesis is considerably less sensitive to temperature than growth. As a consequence, all plants tested so far show increased nonstructural carbohydrate (NSC) tissue concentrations when exposed to low temperatures. Reduced carbon supply is thus an unlikely cause for low temperature range limits of plants. For altitudinal treeline trees there is, however, a possibility that high NSC genotypes have been selected. Here, we explored this possibility using afforestations with single-provenance conifers along elevational gradients in the Southern Chilean Andes and the Swiss Alps. Tree growth was measured at each of four approximately equidistant elevations at and below the treeline. Additionally, at the same elevations, needle, branch and stem sapwood tissues were collected to determine NSC concentrations. Overall, growth decreased and NSC concentrations increased with elevation. Along with previous empirical and experimental studies, the findings of this study provide no indication of NSC reduction at the treeline; NSC increased in most species (each represented by one common population) towards their upper climatic limit. The disparity between carbon acquisition and structural carbon investment at low temperature (accumulation of NSC) thus does occur even among genotypes not adapted to treeline environments. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.


Grubb P.J.,University of Cambridge | Bellingham P.J.,Landcare Research | Kohyama T.S.,Hokkaido University | Piper F.I.,Austral University of Chile | And 2 more authors.
Biological Reviews | Year: 2013

For tropical lowland rain forests, Denslow (1987) hypothesized that in areas with large-scale disturbances tree species with a high demand for light make up a larger proportion of the flora; results of tests have been inconsistent. There has been no test for warm temperate rain forests (WTRFs), but they offer a promising testing ground because they differ widely in the extent of disturbance. WTRF is dominated by microphylls sensu Raunkiaer and has a simpler structure and range of physiognomy than tropical or subtropical rain forests. It occurs in six parts of the world: eastern Asia, New Zealand, Chile, South Africa, SE Australia and the Azores. On the Azores it has been mostly destroyed, so we studied instead the subtropical montane rain forest (STMRF) on the Canary Islands which also represents a relict of the kind of WTRF that once stretched across southern Eurasia. We sought to find whether in these six regions the proportion of tree species needing canopy gaps for establishment reflects the frequency and/or extent of canopy disturbance by wind, landslide, volcanic eruptions (lava flow and ash fall), flood or fire. We used standard floras and ecological accounts to draw up lists of core tree species commonly reaching 5m height. We excluded species which are very rare, very localized in distribution, or confined to special habitats, e.g. coastal forests or rocky sites. We used published accounts and our own experience to classify species into three groups: (1) needing canopy gaps for establishment; (2) needing either light shade throughout or a canopy gap relatively soon (a few months or years) after establishment; and (3) variously more shade-tolerant. Group 1 species were divided according the kind of canopy opening needed: tree-fall gap, landslide, lava flow, flood or fire. Only some of the significant differences in proportion of Group 1 species were consistent with differences in the extent of disturbance; even in some of those cases other factors seem likely to have had a major determining influence during evolution. We also sought to determine whether the species that are at least 'short-term persistent' in the soil seed bank (lasting 2-4years) are all species needing canopy gaps for establishment. The answer was negative; large numbers of seeds of some shade-tolerants accumulate in the soil, and these species are able to benefit from soil disturbance in deep shade. We found a significant and strong positive relationship in Japan between mean seed mass and mature tree height, a weak positive relationship in New Zealand and no relationship in any of the other four regions. When comparing the seed mass values of Group 1 and Group 3 species we obtained different answers depending on whether or not we confined ourselves to taxonomically controlled contrasts. In only two of the four regions with an appreciable number of species in Group 1 is the mean seed mass of such species significantly lower than that of Group 3 species when taxonomic relatedness is ignored. © 2013 Cambridge Philosophical Society.


Araujo M.B.,CSIC - National Museum of Natural Sciences | Araujo M.B.,University of Évora | Araujo M.B.,Copenhagen University | Ferri-Yanez F.,CSIC - National Museum of Natural Sciences | And 6 more authors.
Ecology Letters | Year: 2013

Climate change is altering phenology and distributions of many species and further changes are projected. Can species physiologically adapt to climate warming? We analyse thermal tolerances of a large number of terrestrial ectotherm (n = 697), endotherm (n = 227) and plant (n = 1816) species worldwide, and show that tolerance to heat is largely conserved across lineages, while tolerance to cold varies between and within species. This pattern, previously documented for ectotherms, is apparent for this group and for endotherms and plants, challenging the longstanding view that physiological tolerances of species change continuously across climatic gradients. An alternative view is proposed in which the thermal component of climatic niches would overlap across species more than expected. We argue that hard physiological boundaries exist that constrain evolution of tolerances of terrestrial organisms to high temperatures. In contrast, evolution of tolerances to cold should be more frequent. One consequence of conservatism of upper thermal tolerances is that estimated niches for cold-adapted species will tend to underestimate their upper thermal limits, thereby potentially inflating assessments of risk from climate change. In contrast, species whose climatic preferences are close to their upper thermal limits will unlikely evolve physiological tolerances to increased heat, thereby being predictably more affected by warming. © 2013 The Authors.


Hune M.,Fundacion Ictiologica | Hune M.,Institute Ecologia y Biodiversidad IEB | Vega R.,Institute Fomento Pesquero
Polar Biology | Year: 2015

The black southern cod, Patagonotothen tessellata, is the most important notothenioid fish species in terms of abundance in southern Chilean Patagonia. However, studies on its trophic ecology are scarce. Here we assessed the spatial variation in the diet of P. tessellata between two localities, one with oceanic influence (Staples Strait) and another with continental influence (Puerto Bories). We used permutation analysis combined with non-metric multi-dimensional scaling to evaluate spatial differences in diet. In addition, generalized additive models were used to identify the most significant environmental, biological and spatial predictors of variability in diet. The black southern cod presents spatial differences in diet composition among contrasting environmental localities. The diet in Staples Strait was characterized by the dominance of the polychaete Platynereis australis, whereas diet in Puerto Bories was characterized by crustaceans, mainly ostracods, gammarids and algae, mainly the filamentous green alga Rhizoclonium sp. and the red algae Polysiphonia sp. Diet composition did not show significant difference between sexes, whereas diet of small, medium and large fish differed to some degree. Smaller-sized P. tessellata were most likely to contain food. Salinity and temperature had significant influence on diet variability, suggesting that P. tessellata showed a greater diversity of prey items in environmental conditions with greater temperature and lower salinity. The results provide evidence of two dietary patterns depending on the type of environment in which they are distributed, highlighting the potential role of the environmental variables on the availability and abundance of potential prey and in structuring diet. © 2015, Springer-Verlag Berlin Heidelberg.


Fajardo A.,Center for Ecosystem Research in Patagonia | Piper F.I.,Center for Ecosystem Research in Patagonia | Piper F.I.,Institute Ecologia y Biodiversidad IEB | Cavieres L.A.,University of Concepción | Cavieres L.A.,Institute Ecologia y Biodiversidad IEB
Global Ecology and Biogeography | Year: 2011

Aim Two alternative hypotheses attempt to explain the upper elevation limit of tree lines world-wide, the carbon-limitation hypothesis (CLH) and the growth-limitation hypothesis (GLH); the altitudinal decrease of temperature is considered the driver constraining either carbon gain or growth. Using a widely distributed tree line species (Nothofagus pumilio) we tested whether tree line altitude is explained by the CLH or the GLH, distinguishing local from global effects. We elaborated expectations based on most probable trends of carbon charging with altitude according to both hypotheses, considering the alternative effects of drought. Location Two climatically contrasting tree line ecotones in the southern Andes of Chile: Mediterranean (36°54' S) and Patagonia (46°04' S). Methods At both locations, 35-50 trees of different ages were selected at each of four altitudes (including tree line), and stem and root sapwood tissues were collected to determine non-structural carbohydrate (NSC) concentrations. NSC accumulates whenever growth is more limited than photosynthesis. An altitudinal increase in NSCs means support for the GLH, while the opposite trend supports the CLH. We also determined stable carbon isotope ratios (δ13C) to examine drought constraints on carbon gain. Results NSC concentrations were positively correlated with altitude for stem tissue at the Mediterranean and root sapwood tissue at the Patagonia site. No depletion of NSC was found at either site in either tissue type. For both tissues, mean NSC concentrations were higher for the Patagonia site than for the Mediterranean site. Mean root sapwood NSC concentration values were five times higher than those of the corresponding stem sapwood at all altitudes. Values for δ13C were positively correlated with altitude in the Mediterranean site only. Main conclusions We found support for the GLH at the site without drought effects (Patagonia) and no support for the CLH at either site. It is suggested that drought moderated the effects of low temperature by masking the expected trend of the GLH at the Mediterranean site. © 2010 Blackwell Publishing Ltd.


Cavieres L.A.,University of Concepción | Cavieres L.A.,Institute Ecologia y Biodiversidad IEB | Penaloza A.,Poch Ambiental S.A.
Perspectives in Plant Ecology, Evolution and Systematics | Year: 2012

Most of the studies that have evaluated the interplay between interference and facilitation have been done at the interspecific level, whereas studies at the intraspecific level are scarce. The montane sclerophyllous forests of central Chile are dominated by the tree Kageneckia angustifolia, a semi-deciduous species that lose part of its foliage during summer. It has been reported that during winter snow accumulates in lower amounts beneath the canopy of K. angustifolia favoring the recruitment of new individuals compared to open areas (i.e., facilitation effect). However, it has also been reported that the leaf litter accumulated beneath parental trees contains allelopathic compounds that decrease seed germination, suggesting that recruitment beneath parental plants can be disfavored (i.e., interference effect). Hence, this system seems appropriate to assess the net-outcome between facilitative and negative effects during the emergence and survival of seedlings during the first year. In this study, we asked (i) what is the net-outcome between facilitative and interfering effects for K. angustifolia? (ii) does this net-outcome varies with the distance to parental trees? (iii) are positive and negative effects consistent through the seedling emergence and first year seedling survival phases? (iv) what are the main mechanisms behind the observed net-outcome? and (v) which is the optimal microhabitat for successful recruitment of this species? In an experimental plot of 10,000m 2, we selected ten K. angustifolia trees and evaluated the effect of leaf litter on the emergence and survival of seedlings produced by experimentally sown seed seeds in three different microhabitats: beneath adult trees, edge of canopy and in open areas. In addition, we sampled three K. angustifolia stands to evaluate the microhabitat where the natural recruitment of this species actually occurring. Results showed that (1) seedling emergence was greater beneath canopy, intermediate in canopy edge and low in open areas, (2) whilst leaf litter significantly reduced seed germination, the magnitude of this negative effect was lower than the positive effect of beneath canopy microhabitat, (3) seedling survival was affected by microhabitats but not by the presence of leaf litter, (4) that the main mechanisms behind the observed patterns are the lower and delayed emergence of seedlings in open areas due to the longer duration of snow cover, decreasing the time to growth before the onset of summer drought, and (5) the greatest natural recruitment of K. angustifolia seedlings occurs beneath parental plants. Therefore, our findings suggest that the net-outcome between facilitative and interfering effect during the first year is mostly facilitative, indicating that adult trees of K. angustifolia are exerting a conspecific nurse effect on the recruitment of new individuals, a form of parental care in plants. © 2011 Perspectives in Plant Ecology, Evolution and Systematics.


Cavieres L.A.,University of Concepción | Cavieres L.A.,Institute Ecologia y Biodiversidad IEB | Sierra-Almeida A.,University of Concepción | Sierra-Almeida A.,Institute Ecologia y Biodiversidad IEB
Oecologia | Year: 2012

Positive interactions between species are known to play an important role in the structure and dynamics of alpine plant communities. The balance between negative and positive interactions is known to shift along spatial and temporal gradients, with positive effects prevailing over negative ones as the environmental stress increases. Thus, this balance is likely to be affected by climate change. We hypothesized that increases in temperature (a global warming scenario) should decrease the importance of positive interactions for the survival and growth of alpine plant species. To test this hypothesis, we selected individuals of the native grass species Hordeum comosum growing within the nurse cushion species Azorella madreporica at 3,600 m. a. s. l. in Los Andes (Chile), and performed nurse removal and seedling survival experiments under natural and warmer conditions. For warmer conditions, we used open-top chambers, which increased the temperature by 4 °C. After two growing seasons, we compared the effect of nurse removal on the survival, biomass, and photochemical efficiency of H. comosum individuals under warmer and natural conditions. Nurse removal significantly decreased the survival, biomass, and photochemical efficiency of H. comosum, demonstrating the facilitative effects of nurse cushions. Seedling survival was also enhanced by cushions, even under warmer conditions. However, warmer conditions only partially mitigated the negative effects of nurse removal, suggesting that facilitative effects of cushions do not wane under warmer conditions. Thus, facilitative interactions are vital to the performance and survival of alpine species, and these positive interactions will continue to be important in the warmer conditions of the future in high-alpine habitats. © 2012 Springer-Verlag.


Angelica Casanova-Katny M.,University of Concepción | Cavieres L.A.,University of Concepción | Cavieres L.A.,Institute Ecologia y Biodiversidad IEB
Polar Biology | Year: 2012

The vegetation of the Antarctic tundra is dominated by mosses and lichens. Deschampsia antarctica, the Antarctic hairgrass, is one of two vascular plant species which grow along the west coast of the Antarctic Peninsula. However, little is known about its recruitment and interaction with non-vascular tundra plants. Although several authors propose that tolerance and/or competition should be the main forms of interaction between moss carpets and D. antarctica, no relevant studies exist so far. We investigated whether positive interactions are predominant at the Shetland Islands and the west coast of the Antarctic Peninsula and focussed on the role that moss carpets play in the recruitment of D. antarctica. Across the studied zone, D. antarctica showed a significant association with moss carpets, with higher frequencies as well as more and larger individuals than on bare ground. At one site, we conducted moss removal and seedlings transplant experiments to assess the relevance of the moss carpets for different life stages of hairgrass. All experimental individuals survived until the following summer whether the moss carpet was removed or not, but growth rate was significantly lower in tussocks with moss carpets removed. Likewise, tiller size was higher in plants growing in moss carpets than on bare ground. The detected positive interactions with mosses seem to be important for the expansion of D. antarctica, raising the question about their importance under future climate change scenarios. © 2012 Springer-Verlag.


Sierra-Almeida A.,University of Concepción | Sierra-Almeida A.,Institute Ecologia y Biodiversidad IEB | Cavieres L.A.,University of Concepción | Cavieres L.A.,Institute Ecologia y Biodiversidad IEB
Oecologia | Year: 2010

Alpine habitats have been proposed as particularly sensitive to climate change. Shorter snow cover could expose high-elevation plants to very low temperatures, increasing their risk of suffering damage by freezing, hence decreasing their population viability. In addition, a longer and warmer growing season could affect the hardening process on these species. Thus, understanding the ability of these species to withstand freezing events under warmer conditions is essential for predicting how alpine species may respond to future climate changes. Here we assessed the freezing resistance of 11 species from the central Chilean Andes by determining their low temperature damage (LT 50) and freezing point (FP) after experimental warming in the field. Plants were exposed during two growing seasons to a passive increase in the air temperature using open top chambers (OTCs). OTCs increased by ca. 3 K the mean air and soil daytime temperatures, but had smaller effects on freezing temperatures. Leaf temperature of the different species was on average 5. 5 K warmer inside OTCs at midday. While LT 50 of control plants ranged from -9.9 to -22.4, that of warmed plants ranged from -7.4 to -17.3°C. Overall, high-Andean species growing inside OTCs increased their LT 50 ca. 4 K, indicating that warming decreased their ability to survive severe freezing events. Moreover, plants inside OTCs increased the FP ca. 2 K in some studied species, indicating that warming altered processes of ice crystal formation. Resistance of very low temperatures is a key feature of high-elevation species; our results suggest that current climate warming trends will seriously threaten the survival of high-elevation plants by decreasing their ability to withstand severe freezing events. © Springer-Verlag 2010.


Perez F.,University of Santiago de Chile | Perez F.,Institute Ecologia y Biodiversidad IEB
Plant Systematics and Evolution | Year: 2011

In this study I have examined the patterns of morphological and genetic differentiation between two species of the Andean genus Schizanthus that differ in their pollination and mating systems. Schizanthus hookeri has a bee pollination syndrome and is strongly dependent on pollinators for seed set. In contrast, S. grahamii has a hummingbird pollination syndrome and exhibits late autonomous selfing. Southern populations of the latter species have red flowers (reddish morph), while northern populations have yellow (yellowish morph) or pink flowers (pinkish morph). I used two noncoding chloroplast DNA (cpDNA) regions to investigate the genetic affinities between S. hookeri and the three morphs of S. grahamii. I also performed intra- and interspecific crosses to assess whether gene flow between species was possible. Phylogenetic analyses supported the existence of two differentiated clades that did not match currently accepted taxonomic classification. Accordingly, genetic distance did not correlate significantly with morphological distance. No fruits were produced from interspecific crosses, and there were no individuals with intermediate morphology that could indicate current and frequent hybridization events between species. I propose that the discordance between cpDNA data and conventional taxonomy could be explained by parallel evolution, or alternatively, by a very sporadic hybridization. © 2011 Springer-Verlag.

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