Leaf traits in Chilean matorral: sclerophylly within,among, and beyond matorral,and its environmental determinants

Studies of leaf traits often focus on tradeoffs between growth and resource conservation, but little is known about variation in the mechanical traits that influence resource conservation. This study investigates how leaf mechanical traits vary across matorral vegetation in central Chile, how they correlate with environmental factors, and how these trends compare at a broader geographic scale. Leaf toughness, strength, stiffness, and associated traits were measured in five matorral types in central Chile, and relationships with soil N and P and climate variables were assessed. Trends with soil and climate were then analyzed across shrubland and woodland in Chile, Western Australia, and New Caledonia. Chilean species varied in leaf mechanics and associated traits, both within and among matorral types, with more species in sclerophyll matorral having strong, tough, and stiff leaves than in arid and littoral matorral. Overall, leaves with high leaf dry mass per area were stiffer, tougher, stronger, thicker, denser, with more fiber, lignin, phenolics and fiber per unit protein and less protein: tannin activity and N and P per mass, forming a broad sclerophylly syndrome. Mechanical traits of matorral species were not correlated with soil N or P, or predictably with climate variables, except flexural stiffness (EI_W) which correlated positively with annual reference evapotranspiration (ET₀). However, soil P made strong independent contributions to variation in leaf mechanics across shrublands and woodlands of Chile, Western Australia, and New Caledonia, either separately (strength) or together with ET₀ (toughness) explaining 46–90% of variation. Hence ET₀ was predictive of EI_W in Chilean matorral, whereas soil P was highly predictive of variation in leaf strength, and combined with ET₀ was highly predictive of toughness, at a broader geographic scale. The biological basis of these relationships, however, may be complex.     

Afforestation causes changes in post‐fire regeneration in native shrubland communities of northwestern Patagonia,Argentina

Question: What are the effects of fire in native shrubland communities and in pine plantations established in these shrublands? Location: Northern Patagonia, Argentina. Methods: We surveyed four sites in Chall‐Huaco valley, located in northwest Patagonia. Each site was a vegetation mosaic composed of an unburned Pinus ponderosa plantation, a plantation burned in 1996, and an unburned matorral and a matorral burned by the same fire. We recorded the cover of all vascular plant species. We also analysed species richness, total cover, proportion of exotic species, abundance of woody species and herb species, cover of exotic species, abundance of woody and herb species and differences in composition of species. For both shrubs and tree species we recorded the main strategy of regeneration (by resprouting or by seed). Results: We found that fire had different effects on native matorral and pine plantations. Five years after fire, plantations came to be dominated by herbs and exotic species, showing differences in floristic composition. In contrast, matorral communities remained very similar to unburned matorral in terms of species richness, proportion of woody species, and herb species and proportion of exotics. Also, pine plantations were primarily colonized by seedlings, while matorrals were primarily colonized by resprouting. Conclusions: Matorrals are highly fire resilient communities, and the practice of establishing plantations on matorrals produces a strong reduction in the capacity of matorral to return to its original state. The elimination of shrubs owing to the effect of plantations can hinder regeneration of native ecosystems. Burned plantations may slowly develop into ecosystems similar to the native ones, or they may produce a new ecosystem dominated by exotic herbs. This study shows that plantations of exotic conifers affect native vegetation even after they have been removed, as in this case by fire.     

Food preferences by Octodon degus (Rodentia caviomorpha): Their role in the chilean matorral composition

Summary The food preferences of Octodon degus are examined in laboratory test. Results indicate that degus prefer new rather than mature leaves of Chilean matorral shrubs, and that degus do not discriminate between new leaves (equivalents of shrub seedlings) of different shrub species. The significance of degus preferences in relation to matorral composition is discussed.     

Vegetative responses to defoliation of two Chilean matorral shrubs

Summary 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.     

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

Summary 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.     

Importance of the soil seed bank of disturbed sites in Chilean matorral in early secondary succession

Abstract. The dynamics of the seed bank may provide clues to the process of recovery of the vegetation of disturbed sites. The role of the seed bank may be more important in areas with a seasonal climate than in areas where seedling recruitment is not limited to one season. We studied the seed bank and the seed rain in three sites of the Chilean mediterranean-climate region (33° 48'S) which differed in the degree of anthropic disturbance: a closed-canopy, second-growth forest; an open matorral; and an old-field. Additionally, we tested the germination of seeds from the soil and from the current-year seed crop. The seed bank varied considerably between the two years of study, although no change in the vegetation could be observed. Seed density and species richness were lower in 1989 than in 1988. The seed bank of the second-growth forest changed less between years, while the old-field showed the largest change. The highest seed rain occurred under shrub patches in the open matorral, while few seeds fell in the spaces between shrub clumps or in the old-field. In the forest, seed rain was low and correlated with species cover. Germination was low (0 - 15%) in tests using either soil samples or fresh seeds. These results indicate that matorral succession is a very slow process, limited mainly by low germination and low arrival of propagules to open areas. Most woody species have animal-disseminated fleshy propagules. The presence of established shrubs which may serve as perches or refuges for animals increases species richness in the seed rain and the seed bank.     

Anthropogenic fires increase alien and native annual species in the Chilean coastal matorral

Aim We tested the hypothesis that anthropogenic fires favour the successful establishment of alien annual species to the detriment of natives in the Chilean coastal matorral. Location Valparaíso Region, central Chile. Methods We sampled seed rain, seedbank emergence and establishment of species in four paired burned and unburned areas and compared (using GLMM) fire resistance and propagule arrival of alien and native species. To assess the relative importance of seed dispersal and seedbank survival in explaining plant establishment after fire, we compared seed rain and seedbank structure with post‐fire vegetation using ordination analyses. Results Fire did not change the proportion of alien species in the coastal matorral. However, fire increased the number of annual species (natives and aliens) of which 87% were aliens. Fire reduced the alien seedbank and not the native seedbank, but alien species remained dominant in burned soil samples (66% of the total species richness). Seed rain was higher for alien annuals than for native annuals or perennials, thus contributing to their establishment after fire. Nevertheless, seed rain was less important than seedbank survival in explaining plant establishment in burned areas. Main conclusions Anthropogenic fires favoured alien and native annuals. Thus, fire did not increase the alien/native ratio but increased the richness of alien species. The successful establishment of alien annuals was attributable to their ability to maintain rich seedbanks in burned areas and to the greater propagule arrival compared to native species. The native seedbank also survived fire, indicating that the herbaceous community has become highly resilient after centuries of human disturbances. Our results demonstrate that fire is a relevant factor for the maintenance of alien‐dominated grasslands in the matorral and highlight the importance of considering the interactive effect of seed rain and seedbank survival to understand plant invasion patterns in fire‐prone ecosystems.     

Mycorrhizal perennials of the "matorral xerófilo" and the "selva baja caducifolia" communities in the semiarid Tehuacán-Cuicatlán Valley,Mexico

We investigated the mycorrhizal status of perennial xeric plant species occurring in the "matorral xerófilo" (arid tropical scrub) and the ecotone of the "selva baja caducifolia" (tropical deciduous forest) communities in the semiarid valley of Tehuacán-Cuicatlán, south-central Mexico. The perennial species examined are dominant/codominant elements within the "matorral xerófilo" and the "selva baja caducifolia", both endangered communities in the Biosphere Reserve Tehuacán-Cuicatlán Valley. Of the 50 sampled species, 45 were mycorrhizal. To our knowledge, we report arbuscular mycorrhizae (AM) for the first time in 37 species, of which 21 are endemic to Mexico and nine are endemic to the Valley. We also report AM for the first time in three genera, Buddleja, Hechtia and Zornia, and in one plant family, Buddlejaceae. Beaucarnea gracilis, a threatened species, and Mimosa purpusii, a potentially rare species, are both mycorrhizal. This is the first study of the mycorrhizal status of plant species within the Valley.     

Relationship between topography and the distribution of matorral plant species in the Saharan Atlas: Case of Djebel Amour,Algeria

One of the primary goals in community ecology is to determine the relative importance of processes and mechanisms that control biodiversity. The reduced coverage of vegetation and the severe losses of biodiversity in semiarid matorrals have recently become serious concerns in the Saharan Atlas in southern Algeria. In terms of research, the control of the spatial distribution of vegetation by the topographic factors has not received the attention it merits in Djebel Amour's region. This study combined several multivariate analyses to assess quantitatively the extent and nature of the topographic influence on the distribution of matorral plant species. Thirty plots (20 m × 20 m) were selected according to their physiognomy for the field survey of vegetation and topography in a semiarid mountainous region. The distributions of vegetation differed significantly amongst topographies, indicating different environmental conditions and determine a turnover of important species. Most species colonize downslopes, and only some persist on steep-slopes and summits. The low coverage of vegetation (36.98%) on steep-slopes was due to the serious soil erosion and rockiness 66.5–83.1%. The low average richness in summits (39.67) was due to elevation and negative effect of trees. Elevation, then rockiness and slope were respectively the main topographic factors influencing the distribution of matorral plants. The relationship between topography and distribution could be described by a linear model. Seventeen linear models were built for eleven floristic variables with three topographic factors, elevation, rockiness and slope explained 26–83% of the variance in distribution, also four groups of plant species were listed according to topographic positions. The suitability of plant species to the topographic factors should be considered in the restoration of matorrals in the study area. The results of this study will be useful for selecting the appropriate species and the potential sites for seeding to improving damaged matorral ecosystems in this area. However, additional investigations on soils, water availability and microclimate are required to clarify the mechanism of distribution of plant species in these ecosystems.     

Limiting mechanisms in the regeneration of the Chilean matorral – Experiments on seedling establishment in burned and cleared mesic sites

The Chilean matorral is characterized by multispecific shrub clumps in dry areas but has a continuous canopy in wetter sites. It has been hypothesized that this difference is due to easier recolonization of open patches by shrub seedlings under more mesic conditions. Within the mesic range of the matorral we designed a field experiment to compare shrub seedling emergence, growth, and survival under the closed canopy of a secondary forest versus three types of open patches: burned, cleared of shrubs but with a herbaceous layer present, and clear without a herbaceous layer. After the first summer, survival of Quillaja saponaria seedlings was 75% in the burned site, 30% in the cleared patch without herbaceous vegetation, and 15% with herbaceous vegetation present, whereas there was 0% survival under the secondary forest canopy. After eight years, the percentages had dropped to: 22%, 12% and 3%, respectively. These results contrast strongly with the seedling establishment patterns in drier areas of the matorral where early seedling survival is higher under the shade of large shrubs. In the experimental mesic sites, seedlings did best on the burned site, not only in terms of survival, but also in terms of growth. After one year, seedling mean height was 10.2 cm in the burned site, whereas 3.8 cm and 5.3 cm in the cleared patches without and with herbaceous respectively. After eight years, mean height differences between treatments had increased further: 147.7 cm in the burned site, 40.3 cm in the cleared patch without herbaceous cover and 13 cm in the cleared patch with herbs. Our results indicate that the facilitative effect of nurse shrubs on seedling establishment found in dry ranges of the matorral is less important in more mesic sites. This difference may explain the continuous shrub cover in relatively mesic areas as opposed to the characteristic patchy structure of the matorral in its drier range.     

Phylogenetic relationships and ecological speciation in the mistletoe Tristerix (Loranthaceae): the influence of pollinators, dispersers, and hosts

Phylogenies can provide valuable information on biotic and abiotic factors associated with speciation. We examined species relationships in Tristerix (Loranthaceae), a genus of 11 species with an Andean distribution from Colombia to Chile. A previous classification divided Tristerix into subgenera Tristerix (two species) and Metastachys (nine species). We tested this classification by generating a molecular phylogeny of the genus using nuclear ribosomal DNA ITS and chloroplast atpB-rbcL intergenic spacer and trnL-F regions. All partitions generally gave congruent trees, thus a combined analysis was conducted. Tristerix was composed of a northern clade (six species) and a southern clade (four species). Tristerix verticillatus and T. penduliflorus (Metastachys) were strongly supported as members of the (southern) subgenus Tristerix clade. Speciation appears to be correlated with the emergence of matorral and cloud forest biomes and is driven by interactions with pollinators and seed dispersers. Tristerix aphyllus is sister to T. corymbosus of the matorral, not to neighboring temperate forest populations, thus rendering the latter species paraphyletic. This ecological speciation event may have occurred in sympatry. Tristerix provides excellent examples of how, during the orography of the Andes, many dynamic and interacting ecological factors have influenced their speciation.     

THE ANNUAL RHYTHM OF CAMBIAL ACTIVITY IN TWO WOODY SPECIES OF THE CHILEAN “MATORRAL”

The annual rhythm of cambial activity is compared in Proustia cuneifolia and Acacia caven, two typical shrubs of the “matorral” in the semiarid region of central Chile. Proustia, a drought deciduous shrub, shows a typical desert cambial rhythm, highly sensitive to rainfall. The growth activity of this species is limited to the periods of adequate moisture. Acacia is an evergreen whose cambial activity is observed almost throughout the year; it is not synchronous with rainfall. Adaptation in this species seems to consist in developing long roots able to tap underground water. These results indicate that both shrubs, although growing together, have different adaptive strategies to the same xerophytic conditions.     

The significance of fire intensity in creating local patchiness in the Chilean matorral

The hypothesis that high and low intensity human-made fires can produce ecologically different effects in the Chilean matorral is examined. We compared the abundance of naturally established seedlings under shrubs burned by low and high intensity fires on five north and five south facing slopes. On south facing slopes, we found 54 shrubs burned by low intensity fires and only 4 shrubs burned by high intensity fires. In contrast, north facing slopes had approximately the same number of shrubs burned by low and high fire intensity fires (24 versus 19, respectively). We only found seedlings under shrubs burned by low intensity fires and most of them were of Muehlenbeckia hastulata and Trevoa trinervis. Also viable seeds were only found under shrubs burned by low intensity fires. Results indicate that fire intensity can be an important factor determining species distribution patterns in the matorral.     

Community structure of endemic Mimosa species and environmental heterogeneity in a semi‐arid Mexican valley

Abstract. In this paper we analyse six communities with seven Mimosa species in the Tehuacán‐Cuicatlán valley, Mexico. All species are endemic to Mexico and four are endemic to the valley. Mimosa species are found in (1) the ‘matorral xerófilo’ (arid tropical scrub): Mimosa calcicola, M. lacerata, M. luisana, M. polyantha and M. purpusii, and (2) the ‘selva baja caducifolia’ (tropical deciduous forest): M. adenantheroides, Mimosa texana var. filipes. Most of them occur in similar soil environments, while M. polyantha and M. calcicola establish in particular soil conditions and only M. luisana establishes in two different sites showing a wider range of adaptation to soil characteristics. The communities studied include 24 plant families, 51 genera and ca. 70 species (5% of the total flora estimated in the valley). Heterogeneity was found among the communities. Our results point to the replacement of ‘matorral xerófilo’ and ‘selva baja caducifolia’ by ‘matorral espinoso’ (thorny scrub). Thorny species (e.g. Acacia cochliacantha, Mimosa spp.) are becoming the dominant/codominant elements in the communities. Within the communities, Mimosa species have a significant influence on soil pH, organic matter and electrical conductivity values. These species contribute to ameliorate soil nutrient conditions (OM, N_tot, P, Ca, Mg, Na and K contents) as well as other environmental factors (e.g. temperature, shade) under their canopy in degraded plant communities and may serve as ‘resource islands’.     

Plant species richness in a natural Argentinian matorral shrub-land correlates negatively with levels of plant phosphorus

The aim of this study was to ascertain whether there is a relationship between plant species richness and plant-available N, P and water in an environment subject to little anthropogenic disturbance. To accomplish this we studied the vegetation in matorral shrub-lands in northern Patagonia, Argentina. Due to the variation in slope, precipitation and aspect between the sites water status was determined using the ¹²C/¹³C fraction, ??¹³C, to investigate whether this was a confounding factor. The numbers of herb, shrub, liana and tree species were determined at 20 sites along an estimated precipitation gradient. Leaf P and N content and the ??¹³C of Berberis buxifolia were determined, as well as the soil P and N content at the different sites. A negative correlation was found between species richness and Berberis buxifolia foliar P concentration (52% of the species richness variation was accounted for), and a positive correlation was found between plant species richness and Berberis buxifolia foliar N: P ratios (54% of the species richness variation was accounted for). The relationship between species richness and foliar P was seen when all layers of vegetation were included (trees, lianas, shrubs and herbs). Foliar N showed no correlation with species richness, while soil extractable NH₄ showed a weak positive correlation with the number of shrub layer species (lianas, shrubs and trees). The species richness of the shrub layer increased with decreasing values of ??¹³C. Low soil P availability thus affects local species richness in the matorral shrub-lands of Patagonia in Argentina although the growth of vegetation in the area has been shown to be limited by N. We suggest that low P levels increase plant species richness because low soil P concentration is associated with a high P partitioning and high potential for niche separation.     

Geographic variation in fruit colour is associated with contrasting seed disperser assemblages in a south‐Andean mistletoe

Fruit colour influences fruit choice by seed dispersers. The mistletoe Tristerix corymbosus (Loranthaceae) produces mature fruits of two different colours in two different biomes: yellow in the Chilean matorral and green in the temperate forest of southern South America. We conducted field surveys to establish the association between fruit colour and disperser identity throughout the entire geographical range of T. corymbosus. We selected 22 populations, eight of which were located in the Chilean matorral and 14 in the temperate forest south of the matorral. To identify the seed dispersers of the mistletoe we used direct observation, camera traps, and live‐trapping of small mammals. We also report experiments to assess fruit selection by seed dispersers based on differences in colour. The assemblages of dispersers of T. corymbosus differ between the two biomes: yellow fruits in Chilean matorral are exclusively dispersed by three bird species while green fruits in the temperate forest are exclusively dispersed by a marsupial. The differences in the assemblages of seed dispersers can be explained by differences in food‐finding strategies between the two assemblages. Green fruits in temperate forest are not easily detected by birds, while colour might not be an important cue for the marsupial because it is nocturnal and uses other senses to locate food. We propose that the association between the marsupial and the green‐fruited mistletoe constitutes an ecological fitting rather than the outcome of a co‐evolutionary process. The marsupial might have allowed the mistletoe T. corymbosus to retain green coloration in mature fruit, a condition to which it is preadapted by a slower ripening process in temperate forest populations.     

Exotic Herbivores as Drivers of Plant Invasion and Switch to Ecosystem Alternative States

This paper discusses the evidence of the way in which coupled herbivore and plant invasions altered the structure and functioning of ecosystems in central Chile, and compares these patterns to results from other Mediterranean ecosystems around the world. In pre-Columbian times, sclerophyllous matorral forests largely covered mediterranean Chile. Remnants of the original, continuous matorral can now be found only on relatively humid slopes of the Coastal Range. In the Intermediate Depression, a long central valley, it has been replaced by extensive savannas dominated by the exotic Acacia caven, whereas the matorral remains on dry slopes as isolated shrub clumps. Experimental work suggests that introduced cattle have played a major role in promoting the shift to Acacia savanna, whereas introduced European rabbits prevent the recolonization of clearings by matorral on the slopes. As in other regions of the world, the loss of woodlands in Chile is likely to have resulted in reduced carbon storage capacity and nutrient recycling, and in increased erosion and climatic aridity within the region. Numerous exotic herbs and grasses now dominate the open areas, and experiments indicate that the dry conditions in the absence of woodland cover in combination with loss of soil fertility and severe grazing by introduced mammals has pushed the competitive balance from native to exotic species. These changes are probably very difficult to reverse. Even if grazing is drastically reduced, drought may prevent the recovery of matorral species in much of the region. However, recent theoretical work suggests that if such grazer reduction is timed to coincide with wet El Niño episodes, recovery of the original woodlands may be triggered.     

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.     

Nitrogen utilization efficiencies in mediterranean-climate shrubs of California and Chile

Summary Comparative studies of nitrogen utilization efficiencies (g assimilation mg^-1 leaf nitrogen expended) for dominant chaparral shrubs of California and matorral shrubs of central Chile indicate varying relationships of these efficiencies to total shrub productivity and community dominance. In California where nitrogen is limiting for shrub growth, increasing nitrogen utilization efficiency is correlated with increased productivity, and species with the highest values are dominant on polar (north-facing) slopes. In Chile where soil nutrients are not strongly limiting, increased nitrogen utilization efficiency beyond a low threshold has little or no effect on productivity. This may be an important aspect of the relative ecological success of deciduous shrubs in Chile. High nitrogen utilization efficiency in Chile is associated with broad ecological amplitude rather than increased competitive ability through higher productivity.     

Population structure and phylogeography of the mistletoes Tristerix corymbosus and T. aphyllus (Loranthaceae) using chloroplast DNA sequence variation

The mistletoe Tristerix corymbosus (Loranthaceae) is present in the temperate forest and Chilean matorral biomes of Chile and northwest Patagonia. The closely related cactus-specific species, T. aphyllus, occurs only in the matorral biome. The population structure of these mistletoes was examined to determine whether the distribution of haplotypes corresponds mostly to geographic zone, biome, or other biotic factors. Samples from 108 individuals in 26 localities of T. corymbosus and 13 individuals in four localities of T. aphyllus were collected. Sequences were obtained from two chloroplast genome regions: the atpB-rbcL spacer and the trnL-F region. Haplotypes were analyzed using parsimony and Bayesian trees as well as parsimony networks. All methods placed the haplotypes in four clades, one of which corresponded to T. aphyllus and the others to T. corymbosus. Within T. corymbosus, the different clades did not correlate with biome, geographical region, host, or any apparent morphological feature of the mistletoe. The morphologically distinct cactus parasite T. aphyllus likely arose in sympatry from an unspecialized tree parasite, T. corymbosus, after a host switch. The present day haplotype distribution is complex and resulted from post-glaciation migrations from multiple Pleistocene refugia.