Chilean Matorral Research Articles

Seasonal fluctuations of vegetative growth in roots and shoots of central Chilean shrubs.

Seasonal growth dynamics of the root and shoot systems of dominant shrubs of the Chilean matorral were studied. In some species root and shoot activity were synchronous, while in others production of fine roots was observed prior to bud burst and shoot elongation. Biomass production of new roots was significantly higher in spring than in autumn. Maximum biomass of dead roots was concomitant with the maximum amounts of litter under the canopy.

Temperature effect on autochory inColliguaya odorifera (Euphorbiaceae)

Colliguaya odorifera Mol. is the only species of the Chilean matorral which shows an active dispersion of its seeds (autochory). This mechanism is dependent on daily variation of temperatures. Other climatic variables (air humidity of vapor pressure deficit) appear as not having direct influences on seed dispersal.

Why are Native Herbs in the Chilean Matorral More Abundant Beneath Bushes: Microclimate or Grazing?

(1) Native perennial herbs in central Chile tend to be most abundant beneath bushes. This may be because the humid microclimate under bushes prevents desiccation (the absence of herbs from open spaces would then be explained by water stress), or it may be because herbivores which eat the herbs forage more in the areas between rather than under the bushes. (2) The problem was studied experimentally by removing half the canopy of eight individual bushes of the same species, and then preventing grazing of the herbs in one half of the removed section with an exclosure. This design allowed comparison of areas protected against desiccation and herbivores (the uncut half of the shrub), with areas protected against herbivores but not desiccation (inside the exclosure), and with unprotected areas exposed to both desiccation and grazing. (3) Results after 1 year showed that grazing (most likely by introduced rabbits) was the main cause of the scarcity of native herbs between bushes, and hence of their relative abundance beneath bushes.

Morphological Structure and Water Balance of Four Chilean Shrub Species

The morphological structure and water balance of two evergreens, Kageneckia oblonga and Lithraea caustica, and two deciduous shrubs, Trevoa trinervis and Satureja gilliesii, from the Chilean matorral, were studied. Deciduous species evade the drought by completely reducing their leafy evaporative surface. The maximum water stress was observed at fall and the plants showed a significant recovery after the first rains when vegetative growth started. T. trinervis is synchronic with the rains in initiating its vegetative growth. Transpiration loss is high in the deciduous shrubs throughout the vegetative period, owing to the lack of stomatal closure and to their mesomorphic foliar structure. Water loss was somewhat restricted in S. gilliesii thanks to the presence of trichomes and to the thickness of their cuticle. The leaves of both deciduous plants last only for one year. The evergreens tolerate fairly well the unfavourable period: K. oblonga - subjected to increasing water stress - recovers after the rains. When water is available transpiration loss is high in K. oblonga but is counteracted by its stomatal closure. L. caustica, whose water strfss is not too severe, controls water loss the year round. Both evergreens possess xeromorphic leaves. Major growth occurs in these plants during spring and summer.

Growth Dynamics of Chilean Matorral Shrubs

Seasonal patterns of leaf area increment and shoot elongation of six Chilean matorral shrub species were analyzed. The leaf area of individual shoots was measured weekly. The leaf area growth rates during the flushing period varied from 0.6 cm2/wk for Satureja gilliesii to 28.9 cm2/wk for Lithraea caustica. The six species had characteristic temporal growth patterns. Satureja gilliesii initiated growth shortly after the first winter rains in June while L. caustica, the last species to become vegetatively active, showed first leaf growth in November (late spring). Shoot elongation rates ranged from 0.06 cm/day for Colliguaya odorifera to 0.17 cm/day for the two summer-deciduous species, S. gilliesii and Trevoa trinervis. The species with low growth rates have long growth periods, and species with high growth rates have short but intensive flushing periods.

Seasonal Water Stress in Some Chilean Matorral Shrubs

Environmental and plant characteristics relating to plant water stress were measured in seven shrub species, Satureja gilliesii, Cryptocarya alba, Quillaja saponaria, Lithraea caustica, Colliguaya odorifera, Retanilla ephedra, and Proustia cinerea, growing on equator- (EFS) and pole-facing (PFS) slopes in the mediterranean region of central Chile. Midday air temperatures and vapor pressure deficits were greater on the EFS than on the PFS. Soil moisture was greater during the winter but less during the summer on the EFS. Midday xylem potentials in all species decreased during the summer, increased after the first rain, and were lower on the EFS. Mean leaf size was smaller on the EFS. Stomatal frequency differed only for Q. saponaria and C. odorifera. Species with shallow root systems had lower xylem potentials.

Root studies in the Chilean matorral.

The roots of matorral shrubs were excavated from an 18 m2 site of a mixed matorral stand located on a 27° NE facing slope at 1000 m elevation 40 km NNW from Santiago de Chile. The climate in this area is similar to that of the Southern Californian chaparral. The main species present were Lithraea caustica, Cryptocarya alba, Colliguaya odorifera, Mutisia retusa, and Satureja gilliesii. After harvesting the above ground biomass, the soil was washed out in 20 cm layers down to a depth of 60 cm. The roots were harvested according to their position in the site, separated into species and root size classes. Soil analysis indicated a fertile and deep reaching, clayish soil. L. caustica was a deep rooting species with many thick roots growing deeper than 60 cm. This species had a massive burl of 67 kg dry weight in the excavation site. Cryptocarya was less deep rooting, and C. odorifera had a shallow root system. It is thought that the root: shoot biomass ratios of 4.9 and 1.4 for L. caustica and C. alba respectively are indicative of the forest character of this site in the past. This forest would have been destroyed by continuous charcoal manufacture. The bulk of the fine roots was found in the 20-40 cm soil layer. The average distance between fine roots was calculated as 1.9 cm. The results were compared with an earlier excavation in the Californian chaparral.

Herbaceous vegetation in the Chilean matorral : Dynamics of growth and evaluation of allelopathic effects of some dominant shrubs.

The phenology, growth, and productivity of 7 species of the understory vegetation of the matorral zone of Central Chile were studied. The activity of the herb strata lasts about 6 months, starting soon after the first rain of the season: most of their vegetative growth occurs between early June and mid-September. Experimental plots designed in the field with leaf litter of some dominant shrubs showed no indication of the presence of allelopathic compounds that inhibit either germination or growth of the annual species in the matorral.

Morphology and Histology of Trevoa trinervis (Rhamnaceae), a Drougth Deciduous Shrub from the Chilean matorral

Summary The ramification system and the histological structures of Trevoa trinervis, a shrub from the Chilean matorral, are studied. The axilar bud system of the principal branches is constituted by a summer bud that originates a thorn-shoot in the first year, and a winter bud. This remains dormant, to sprout rapidly as soon as the soil humidity increases during the following winter. The winter bud originates a small branch, bearing most of the leaves; its growth is completed by the development of a terminal inflorescence. When humidity decreases, both the branches and the leaves dry and drop. The leaves present a mesophytic structure. Several of the characters described are interpreted as adaptations to drought.