Colliguaya Odorifera Research Articles

Spatio-temporal variation in the effect of herbaceous layer on woody seedling survival in a Chilean mediterranean ecosystem

Questions: What is the effect of herbaceous layer on seedling establishment of three woody pioneer species in open areas of central Chile under a semi-arid mediterranean climate? How do inter-annual and habitat conditions (slope aspect) modulate this effect? Under high stress conditions such as the drier year and habitat (north-facing slope) do herbs reach low abundance and have neutral effects on woody seedlings? Under medium stress conditions for these woody species, such as the wetter year and south-facing slope, does the herbaceous layer reach greater abundance and have positive effects on woody seedlings due to increasing soil water content? Location: A watershed on the outskirts of Santiago, Chile, subjected to clearing of woody vegetation through firewood extraction and human-set fires. Methods: In spring 2007, we set up 20 plots (3 m × 2 m). Half of each plot had herbs removed manually and by application of herbicide. In both halves of each plot, one seedling (8 months old) of each of the three native woody species (Colliguaya odorifera, Schinus polygamus and Quillaja saponaria) was planted and survival monitored subsequently. The experiment was repeated in two consecutive growing seasons (2007–2008 and 2008–2009) that differed significantly in total precipitation (152 and 256.5 mm, respectively), and replicated in two sites that differed in aspect and abiotic conditions: a moister south- and a drier north-facing slope. Results: In the first and drier year, the herbaceous layer had low cover and no significant effect on seedling survival of woody species. During the second year, herbs had greater cover and a significant positive effect on spring survival of C. odorifera in the north-facing slope, which was lost after summer. During this wetter year on the south-facing slope, herb cover had a positive effect on survival of S. polygamus (mainly during summer). Conclusions: The role of mostly ruderal herbs on woody seedling establishment depended on the species, rainfall of the current year and slope aspect, and may be explained by soil moisture patterns. This suggests that the effect of ruderal herbs on woody seedlings shifts from neutral under high stress conditions produced by drought to positive under moderate stress conditions. Our results contribute to understand interactions between ruderal herbs and woody species under contrasting abiotic conditions. Therefore, control of the herbaceous layer may not be needed in restoration programmes for this region. Moreover, herbs may benefit restoration of woody cover in mesic habitats.

A Long-Term Study of a Small-Mammal Assemblage in the Central Chilean Matorral

We livetrapped small mammals for 18 months with Sherman traps, and for 13 (simultaneous) months with Tomahawk traps, in a central Chilean matorral (chaparral-like shrub-land) locality near Santiago. Eight species (the marsupial Marmosa elegans , the lagomorph Oryctolagus cuniculus , the cricetids Akodon longipilis, Akodon olivaceus, Oryzomys longicaudatus , and Phyllotis darwini , and the caviomorphs Octodon degus and Abrocoma bennetti ) were captured, with total mean densities of 57.9 and 12.4 individuals per ha in the Sherman and Tomahawk grids, respectively. Tomahawk traps provided the same estimates of density for the two largest rodents, but did not capture small species or adult rabbits. Weights of adult individuals of four species were 20–30% smaller than those reported previously. Octodon and Oryctolagus used shrub cover as available; Abrocoma avoided dense patches, whereas the remaining five species avoided sparse patches. Six mammal species were associated with the six principal shrub species in proportion to their availability, but A. longipilis and Octodon both associated with Colliguaya odorifera more frequently than expected, while apparently avoiding two other shrubs. Stopwatch-timed captures allowed categorization of one small mammal as diurnal and diurnal-crepuscular, two as nocturnal, four as nocturnal and nocturnal-crepuscular; one species was active all day, except at dawn. Comparisons with similar assemblage studies conducted in neighboring matorral areas demonstrate marked differences in population densities of particular mammal species, apparently related to levels of habitat disturbance and associated reductions of shrub cover.

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

Interactions 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.

Effects of feeding by mealybugs (Planococcus citri, homoptera: pseudococcidae) on the growth of Colliguaya odorifera seedlings

Mediterranean-type ecosystems are characterized by their capacity to recover after extended droughts and wildfires. Much of this resilience is attributable to underground storage tissue combined with the capacity for crown sprouting from root burls (Specht 1981; Kummerow and Mangan 1981). Some of the dominant shrubs, however, are poor crown sprouters or obligate seeders. Declining soil moisture typically limits the growing season to spring and early summer months. Only those seedlings which develop a deeply penetrating root system in the season following germination will survive the first summer. First-year shrub seedling survivorship in the southern California chaparral has been measured at 3-10% (Ellis 1983). Thus, seedlings must pass through a critical and very vulnerable establishment phase after fire. The effect of herbivores during this phase may be of great importance. Mills (1983) found that approximately 50% of seedlings of Ceanothus greggii, an obligate-seeding shrub in the southern California chaparral, were lost to small-mammal herbivores during the first growing season after fire. The effects of chewing insects and mammals are relatively easy to observe and quantify (Fuentes et al. 1981, 1983). Louda (1983) has cautioned, however, that assessing damage from estimates of the percent of missing leaf area may seriously underestimate the total herbivore effect and recommends an experimental approach which compares plants with herbivores to plants kept free of herbivores. The effects of sucking insects, although much more difficult to measure, can be significant. About 10% of the one-yearold Ceanothus greggii seedlings were killed by a psyllid infection in a post-burn area in the southern California chaparral (Mills, unpublished data). If seedlings are not killed, however, the relative damage to the plant is difficult to estimate. It would be valuable to correlate a particular level of infection by sap feeders with the growth reduction caused by these insects. The effects of phloem-feeding insects differ from those of chewing herbivores in several respects. Chewing insects or mammals often damage or remove the apical meristems and release axillary buds from apical dominance, causing the sprouting of new shoots which represent competitive sinks for photosynthate and increase the demand for water. Thus, the relative magnitude of the belowground sink may be decreased and relatively less photosynthate would reach the root system. Because phloem feeders do not stimulate axillary growth, the relative magnitude of the belowground sink should remain high and the immediate effect on root growth should be less severe. In fact, reallocation of assimilate from belowground to aboveground meristems has been observed due to feeding of chewing insects (Ryle and Powell 1975; Youngner 1972). On the other hand, increased root or shoot growth, or both, may result from feeding by chewing or sucking herbivores (Bardner and Fletcher 1974; Harris 1973, 1974; Howe et al. 1982; Owen 1980; Owen and Wiegert 1981). A second difference is that phloem feeders do not damage the existing photosynthetic structure but remove photosynthate. Thus all feeding effects would be manifest in decreased growth rates of aboveground and/or belowground plant organs. Regardless of the cause, however, reduction of the flow of carbohydrate to the roots of seedlings in summer-dry ecosystems might prevent establishment of the deep tap root system needed to survive the first summer. The purpose of this study is to assess the damage sustained by seedlings of a sclerophyllous shrub species from a Mediterranean ecosystem under three levels of infection by a phloem-feeding insect. The relative growth of root and shoot systems will be compared. The organisms involved were chosen for convenience. My goal was not to define a specific interaction, but to provide a general model which may be tested by more specific applications. The results should also facilitate estimates of damage to seedlings in the field.

Presence and development of lignotubers in shrubs of the Chilean matorral

The development of lignotubers was analyzed in seedlings of representative shrub species of the matorral in central Chile. The lignotuber is evident 3 months after germination in Cryptocarya alba and 4–5 months after germination in Colliguaya odorifera, Satureja gilliesii, and Lithraea caustica. Top removal in adult specimens soon produced formation of shoots as a result of the activation of the root-crown buds. The leaf area growth rates of shoots arising from lignotubers are significantly higher than those of seedlings and normally growing shrubs. The adaptive significance of lignotubers in matorral shrubs is discussed.

Effect of Fertilizer on Fine Root Density and Shoot Growth in Chilean Matorral

The effect of a fertilizer dose of 20 g nitrogen (N), 16 g phosphorus (P), and 20 g N + 16 g P m-2 on fine root growth and shoot development of four common shrubs was tested in the Chilean matorral, a typical mediterranean-type shrub vegetation. The fine root density (root diameter ~< 2 mm) was highest in late spring and lowest in late summer. The mean fine root length for the 6 mo research period reached 2 km m-2 in Lithraea caustica in the unfertilized controls and 7 km m-2 with N fertilization. Colliguaya odorifera responded similarly. In Cryptocarya alba, fertilizer reduced total fine root length. The fine roots of Trevoa trinervis, a N2-fixing shrub, did not respond to N addition, but enhanced fine root growth with P was observed. The effect of P and N + P on the other shrubs was erratic. In general, fertilizer application shifted the time of the peak of fine root biomass production from spring toward summer. Shoot response to fertilizer became visible only in the second growing season. Nitrogen enha...

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.

Vegetative responses to defoliation of two Chilean matorral shrubs.

This paper reports the results of experimental defoliation of two common matorral species: Lithraea caustica and Colliguaya odorifera. L. caustica and C. odorifera are the matorral species previously shown to exhibit the highest and lowest levels of natural defoliation by browsing. Experimental defoliation was performed at four levels: 0% (controls), 25%, 66%, and 100%. C. odorifera exhibited vegetative responses stronger than controls only in the two highest levels of defoliation (66% and 100%), whereas L. caustica responded vigorously at the 25% and 100% levels. The results are related to the observed position of both species in the matorral community and their relative defoliation risks by natural and introduced herbivores.

Interactions between chilean matorral shrubs and phytophagous insects.

Lithraea caustica (Mol.) H. et Arn. and Colliguaya odorifera Mol. are two sclerophyllous shrubs of the scrub vegetation in Central Chile. These two species commonly grow in close association on equator-facing slopes. Leaves of L. caustica are severely predated upon by phytophagous insects while those of C. odorifera are rarely attacked. Leaf growth dynamics, leaf loss, and leaf predation by insects were correlated through the year with leaf phenolic compounds. Leaf structural properties (cuticle thickness, density, sclerenchymatic fibers, leaf thickness) were similar between the two species, while leaf phenol content differed significantly. The higher phenol content in C. odorifera may influence leaf palatability, and thus account for the observed lower leaf area loss in that species due to insect damage.

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.

Growth pattern and seasonal behavior of buds of Colliguaya odorifera, a shrub from the Chilean mediterranean vegetation

Colliguaya odorifera Mol., an euphorbian shrub, grows among the sclerophyllous scrub of central Chile. The growth pattern and seasonal behavior of the floral and vegetative buds are analyzed, with special reference to the climatic conditions (cool humid winters and dry hot summers). Observations were conducted on marked twigs and in sections of embedded material.The branching system is of a Y-shaped sympodial type. The growth season of C. odorifera extends from early winter to the beginning of summer. When the dry season starts, the vegetative apical meristem is converted into a floral bud, and in the leaf axils partly predetermined, unprotected vegetative buds develop. Both types of buds remain dormant during the drought period. Soon after the first winter rains begin, activity is resumed: the preformed flowers and leaf buds unfold and grow, and a few more leaf pairs develop during the current year. Thus, buds are influenced partially by the climate of the previous and of the next year.