Browsing by Author "ALLIENDE, MC"

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    INTERACTIONS IN THE PATTERNS OF VEGETATIVE GROWTH AND REPRODUCTION IN WOODY DIOECIOUS PLANTS
    (1984) HOFFMANN, AJ; ALLIENDE, MC
    Interactions between vegetative growth and reproduction were evaluated in Peumus boldus, Lithraea caustica and Laretia acaulis, woody dioecious species in central Chile. Phenological observations were made periodically on marked branches of male and female plants, and biomass allocation (dry weight) to vegetative and reproductive tissues was measured. The magnitude of flowering was evaluated in groups of plants in 3 successive seasons. The patterns of activities are species- and sex-dependent, and cycles of 2-4 yr were established. Branches that produce flowers either do not grow or grow less than branches without flowers, and males and females have differential resource allocation: male branches attain higher biomass values. Groups of plants show seasonal behavior that suggest synchrony in their reproductive activities.
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    PLANTS INTRUDING LARETIA-ACAULIS (UMBELLIFERAE), A HIGH ANDEAN CUSHION PLANT
    (1985) ALLIENDE, MC; HOFFMANN, AJ
    Several plants invade the cushions of L. acaulis in the high Andean communities of central Chile. Humus develop among the rosettes, and 42 different spp. settle on the cushions. Most of these species are also found outside the cushions. Semi-woody chamaephytes, hemicryptophytes and cryptophytes have a similar cover on both substrates, while the cover of woody chamaephytes and therophytes is smaller on the cushions. The diversity and cover of invading plants, which vary with altitude, result from interations among the environmental conditions, cushion morphology and the surrounding vegetation.
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    SHRUB CLUMPS OF THE CHILEAN MATORRAL VEGETATION - STRUCTURE AND POSSIBLE MAINTENANCE MECHANISMS
    (1984) FUENTES, ER; OTAIZA, RD; ALLIENDE, MC; HOFFMANN, A; POIANI, A
    Previous studies have claimed that the Chilean matorral is more open than the California [USA] chaparral and have attributed this dissimilarity largely to the role of man in Chile. 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 California chaparral. Evidence is presented that these clumps have been present for at least the last 26 yr 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. Differences between the California chaparral and Chilean matorral may be 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 2 areas.
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    VEGETATION CHANGE IN LARGE CLEARINGS - PATTERNS IN THE CHILEAN MATORRAL
    (1986) FUENTES, ER; HOFFMANN, AJ; POIANI, A; ALLIENDE, MC
    Previous 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 by Baccharis spp. or Acacia 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 [USA] chaparral.