Eduardo R. Fuentes

Shrub clumps of the Chilean matorral vegetation: structure and possible maintenance mechanisms

SummaryPrevious studies have claimed that the Chilean matorral is more open than the Califonia chaparral, and have attributed this dissimilarity largely to the role of man in Chile. In this paper we show that in general the Chilean matorral has a structure better described as shrub clumps that merge to form a continuous vegetation matrix only in very mesic habitats, where it is comparable to the Califonia chaparral. We also present evidence that these clumps have been present for at least the last 26 years and that even without human disturbance they are likely to maintain themselves. Evidence for the latter pertains to seed dispersal, seed germination and establishment, seedling survival, and the diameter size structure of shrub clumps. Finally, we propose that differences between the California chaparral and Chilean matorral are more profound than previously thought and are due not only to different degrees of human disturbance, but also to the presence of periodical natural fires in California and not in Chile, and to different shrub recruitment patterns and mammalian herbivore activity in the two areas.

Vegetation change in large clearings: Patterns in the Chilean matorral

SummaryPrevious studies have shown that in Chile the so called mature matorral can have the form of either a continuous matrix of shrubs (wet sites) or of multispecific clumps of shrubs (dry sites). After clearing, sites are known to be initially covered by annuals and then byBaccharis spp. orAcacia caven shrubs. Further vegetation changes are still not documented. In the first part of this contribution we show evidence indicating that the “seed rain” of plants dispersed by birds is important only around bird perches and that in general “seed shadows” of mature matorral shrubs are small. These results suggest that late recolonization of cleared areas occurs by a slow diffusion process in which the presence of perching sites for birds plays a significant role. Then we exhibit results regarding the importance of seasonal droughts and European rabbits in explaining transitions between the various types of plant cover. Here we conclude that nursing by older shrubs and not by rocks or fallen branches, is a requirement to insure the survival of seedlings belonging to mature matorral shrubs. Nurses are important regarding both summer desiccation and herbivory. These nurse effects seem to be more important at dry sites where rabbits are also more numerous, than at wet sites where conditions seem somewhat milder and vegetation change could be faster. In the last part we discuss a scheme of vegetation change that incorporates these processes and explains the relation between them, the vegetation types and the recolonization of wet and dry areas. Finally, a brief mention is made to the difference between these processes and the comparable ones in the California chaparral.

Tristerix tetrandrus (Loranthaceae) and its host-plants in the Chilean matorral: patterns and mechanisms

SummaryInteractions between a Chilean mistletoe, quintral (Tristerix tetrandrus, Loranthaceae) and its potential host plants were studied at a site with mediterranean type climate. The results show that the distribution of T. tetrandrus is related to the behavior of avian dispersers, which feed on its fruit, and evacuate the seeds at random in the field, but the distribution is also influenced bymicroenvironmental conditions, survival of seedlings is hampered at drier locations. The infection capacity of the seeds is increased after birds have eliminated the fruit coat.Survival of T. tetrandrus seeds differed depending on the species to which they were attached experimentally. Seeds germinated, and plants developed on Colliguaya odorifera and Kageneckia oblonga, previously reported as susceptible to infection. Survival was significantly higher on C. odorifera, although in the field it is infected less frequently than K. oblonga. In species on which no T. tetrandrus has been previously reported, resistance to infection might be ascribed to different mechanisms: in Quillaja saponaria, differentiation of cork layers apparently prevents penetration by haustoria; in Lithraea caustica haustoria enter the cortex and phloem, but no further development ensues. K. oblonga seldom bears more than one T. tetrandrus plant. Experimental inoculations showed that significantly more seeds developed into plants on K. oblonga individuals not previously infected with quintral, suggesting that they become resistant to infection.

Tree species regeneration in a mid-elevation, temperate rain forest in Isla de Chilo?, Chile

The regeneration of canopy and subeanopy species in a mid-elevation, primary rain forest in the Coastal Range of Isla de Chiloé (42°30′S), in the cold-temperate region of Chile, was studied by comparing seedling and sapling abundances under the forest canopy, and within 36 tree-fall gaps. The forest was dominated byAmomyrtus luma andLaurelia philippiana (33 and 32% of the main canopy individuals), and two subcanopy species (Myrceugenia ovata, andMyrceugenia planipes) were also important. Uncommon species in the canopy wereDrimys winteri, Amomyrtus meli, andRaphithamnus spinosus. Tree-fall gaps were created generally by the fall of several trees, and the main canopy species were the principal gap-makers. Gap sizes varied between 28 and 972 m2, with a mean of 197 m2. Seedling and sapling abundances indicate that the dominant species are capable of regenerating below the canopy, but they also germinate and show enhanced growth within small light gaps. For one of the common subcanopy species (M. planipes) and the two infrequent canopy species (D. winteri, andA. meli) regeneration seems to depend entirely on tree-fall gaps. Thus, in this forest, light gaps allow the persistence of infrequent canopy species, but seem less important for the regeneration and maintenance of dominant canopy species.

European rabbits versus native rodents in Central Chile: effects on shrub seedlings

SummaryThe importance of the introduced rabbit Oryctolagus cuniculus and of the native rodent Octodon degus (=degu) as browsers of shrub seedlings in the Central Chilean evergreen shrublands (=matorral) was experimentally assessed. Seedlings were planted in several spatial arrangements in two open successional stands and in two mature stands of different cover and exposure. The browsing impact of rabbits and degus was evaluated separately after about one year since the start of the experiments. It was found that degus cause important seedling mortality only within a 5 m-radius centered at the border of their retreats. Rabbits, on the other hand, cause heavier seedling mortality, forage more widely, and consequently have a greater impact than do degus. It is speculated that rabbits may be halting the secondary succession process, shifting the matorral composition toward less palatable shrub species, and/or broadening the spacing between shrub clumps.

Latitudinal Size Variation of Chilean Foxes: Tests of Alternative Hypotheses

There are only 2 species of canids in mainland Chile: the foxes Dusicyon (ulpaeus and Dusicyon griseus. These 2 species are shown to diverge in body size with increasing latitude: body size of D. culpaeus increases whereas the size of D. griseus decreases south of 330 south latitude (SL). The variables latitude, temperature, annual actual evapotranspiration, and mean size of potential prey species have been previously proposed as correlates of body size in carnivores, but they do not explain the size trends exhibited by the 2 Dusicyon. Instead we found that constancy of mean size of potential prey species throughout the range, and increased habitat overlap between D. culpaceus and D. griseus south of 33? SL, are most likely to explain the size trends of these congeners. Our results suggest a trade-off between habitat and food overlap: progressive increments of interspecific habitat overlap south of 33? SL are compensated by progressively larger differences in body size and in mean prey size.

Does fire induce shrub germination in the Chilean matorral

We tested the hypothesis that fire enhances the germination of shrubs of the Chilean evergreen shrublands (matorral), as shown for other areas with Mediterranean-type climates. We did laboratory tests in which we heated seeds for 5 min to 100°C. These results suggest enhancement of germination. However, field measurements and experiments indicated that at depths where the seed bank is located temperatures are high enough to kill all seedlings and there are no places where temperatures are comparable to those usually used in laboratory to verify germination enhancement by high temperatures. These results are discussed in the perspective of selective pressure of fires for the induction of germination in the Chilean matorral species.

High-latitude rainforests and associated ecosystems of the West Coast of the Americas: climate, hydrology, ecology and conservation.

Section 1. Climate, Hydrology, and History.- 1. North-South Variations in West Coast Hydrometeorological Parameters and Their Significance for Earth Systems.- 2. Factors Controlling the Climate of the West Coast of North America.- 3. Sulfur Cycling in Coastal Upwelling Systems and Its Potential Effects on Climate.- 4. Atmospheric and Geologic Constraints on the Biogeochemistry of North and South American Temperate Rainforests.- 5. Past Changes in Climate and Tree Growth in the Western Americas.- 6. Constraints on Terrestrial Primary Productivity in Temperate Forests Along the Pacific Coast of North and South America.- Section 2. Biotic Patterns.- 7. Biodiversity Patterns in Relation to Climate: The Coastal Temperate Rainforests of North America.- 8. Phytogeographic Relationships and Regional Richness Patterns of the Cool Temperate Rainforest Flora of Southern South America.- 9. A Comparative Review of Forest Dynamics and Disturbance in the Temperate Rainforests of North and South America.- 10 Patterns of Terrestrial Vertebrate Diversity in New World Temperate Rainforests.- 11. Avian Communities in Temperate Rainforests of North and South America.- 12. The Importance of Plant-Bird Mutualisms in the Temperate Rainforest of Southern South America.- 13. The Temperate Rainforest Lakes of Chile and Canada: Comparative Ecology and Sensitivity to Anthropocentric Change.- Section 3. Forest System Responses to Human Activities.- 14. Implications of Patch Dynamics for Forested Ecosystems in the Pacific Northwest.- 15. Assessing and Responding to the Effects of Climate Change on Forest Ecosystems.- 16. A Comparison of the Ecology and Conservation Management of Cool Temperate Rainforest in Tasmania and the Americas.- 17. Logging Effects on the Aquatic Ecosystem: A Case Study in the Carnation Creek Experimental Watershed on Canadas West Coast.- 18. Biodiversity of Canadian Forests, with Particular Reference to the West Coast Forests.- Section 4. Conclusion.- 19. Afterword.

Landscape change under indirect effects of human use: the Savanna of Central Chile

The Chilean Intermediate Depression to the north of Santiago has experienced a physiognomical transformation from a Prosopis chilensis woodland to an Acacia caven savanna. Today P. chilensis trees are scarce and belong mostly to the larger size classes. By contrast A. caven seems to reproduce frequently and its populations consist of individuals of all size classes. In this paper we document these changes and report the results of tests aimed at determining the causes of these physiognomical changes. We found that livestock, leporids, introduced Mediterranean forbs and agriculture account for differences in seed dispersal and survival of A. caven and P. chilensis, which can explain the documented changes in the Chilean landscape.

Correlates of tail losses in twelve species of Liolaemus lizards.

The relative frequencies of naturally occurring tail losses in twelve species of central Chile Liolaemus are reported. It was found that percentages vary between 23.8% and 77.2%. In an attempt to explain these differences, percent tail losses was correlated with an estimate of time exposed to predators (size of the lizards), with an estimate of intraspecific susceptibility to predators (sexual dimorphism), and with percent occupation of conspicuous perches. Partial correlation analysis exhibited statistical significance only with the latter variable, thus suggesting that visibility to predators could be causally related to tail losses. A last cautionary word is offered, indicating that frequency of tail losses is not a measure of predation pressure, but of successful escapes after at least one close encounter with a predator.