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1.
Since only 12.6% of the Brazilian Araucaria Forest remains and timber tree monocultures are expanding, biological invasion is a potential threat to the conservation of natural forest remnants. Here, we test (1) the susceptibility of Araucaria Forest to invasion by Pinus taeda and Eucalyptus saligna, (2) the efficiency of different mechanisms controlling the early establishment of these two exotic timber tree species, and (3) the potential of the native timber tree Araucaria angustifolia to establish successfully in ecologically-managed monocultures of Araucaria, Pinus and Eucalyptus. In Araucaria Forest, more than a thousand Pinus seeds landed annually in a hectare; however, experimentally exposed seeds were 100% removed in only 6 days. Furthermore, all experimentally transplanted seedlings of Pinus taeda and Eucalyptus saligna died in less than a year in Araucaria Forest, but not in the monocultures. Correlative evidence suggests that this mortality was associated to plant community richness, plant abundance, and soil fertility. Araucaria angustifolia, in contrast, showed an establishment success in ecologically-managed tree monocultures as high as that exhibited in its natural habitat. The current resistance of Araucaria Forest to invasion by exotic timber trees is good news for the conservation of Araucaria Forest remnants and for its keystone species. The understanding of the mechanisms providing such resistance against invasion points towards management tools for minimizing future threats.  相似文献   

2.
Paternity analysis based on eight microsatellite loci was used to investigate pollen and seed dispersal patterns of the dioecious wind-pollinated tree, Araucaria angustifolia. The study sites were a 5.4 ha isolated forest fragment and a small tree group situated 1.7 km away, located in Paranalpha State, Brazil. In the forest fragment, 121 males, 99 females, 66 seedlings and 92 juveniles were mapped and genotyped, together with 210 seeds. In the tree group, nine male and two female adults were mapped and genotyped, together with 20 seeds. Paternity analysis within the forest fragment indicated that at least 4% of the seeds, 3% of the seedlings and 7% of the juveniles were fertilized by pollen from trees in the adjacent group, and 6% of the seeds were fertilized by pollen from trees outside these stands. The average pollination distance within the forest fragment was 83 m; when the tree group was included the pollination distance was 2006 m. The average number of effective pollen donors was estimated as 12.6. Mother-trees within the fragment could be assigned to all seedlings and juveniles, suggesting an absence of seed immigration. The distance of seedlings and juveniles from their assigned mother-trees ranged from 0.35 to 291 m (with an average of 83 m). Significant spatial genetic structure among adult trees, seedlings, and juveniles was detected up to 50 m, indicating seed dispersal over a short distance. The effective pollination neighborhood ranged from 0.4 to 3.3 ha. The results suggest that seed dispersal is restricted but that there is long-distance pollen dispersal between the forest fragment and the tree group; thus, the two stands of trees are not isolated.  相似文献   

3.
Abstract Araucaria laubenfelsii Corbasson and Araucaria montana Brongn et Gris are emergent conifers in maquis and forest communities which are subjected to a combination of fire and cyclonic disturbances. Both species are able to survive fire once stems reach a critical size, but most seedlings and saplings are killed. Both species were found to be clumped at most spatial scales for both saplings and trees in maquis, probably resulting from a combination of patchy fire and a limited ability to disperse seeds. Comparisons of burned and unburned A. montana sites suggest that clumping increases only slightly after fire. The degree of clumping in the A. laubenfelsii sites, suggested that fire disturbances may occur relatively frequently in the region. Cyclonic disturbances are infrequent but may result in blow‐down of large individuals within both maquis and forest. All of the individuals blown‐down during the study had been previously fire‐scarred. Around tree blow‐downs, seedling and sapling densities can be high. This likely reflects both the low dispersability of Araucaria seeds and enhanced moisture from the shading of the adult, when it was alive. Disturbance by fire and wind play an important role in the regeneration dynamics and spatial pattern of these species in maquis in New Caledonia.  相似文献   

4.
Tree plantations for commercial use have been replacing native ecosystems all over the world. We investigated how forest conversion to plantations of exotic and native tree species may influence lichen diversity and composition in a southern Brazilian landscape. The lichen community from the National Forest of São Francisco de Paula was studied using three stands of each of the four vegetation types: native Araucaria forest and plantations of Araucaria, Pine and Eucalyptus trees. All plantation stands were surrounded by native Araucaria forest, were of smaller size and were allowed to endure longer than commercially managed plantations. Lichen species and their cover abundance were recorded on tree trunks from 30 to 150 cm above soil level in ten host-trees that were randomly selected in each replication. Seventy-eight lichen species, from 18 genera and 9 families, were registered. Conversion of native forest to plantations of exotic tree species altered species composition by reducing the occurrence of shade tolerant lichens. Plantations of Araucaria angustifolia sustained the highest lichen diversity measured, because this is an excellent host species. These results suggest that a greater diversity of lichens can be preserved in the landscape, if plantations of the exotic Pinus and Eucalyptus genera are replaced by plantations of this native species.  相似文献   

5.
In order to understand the impacts of forest fragmentation on Araucaria angustifolia populations, we evaluated the genetic diversity and mating system using SSR markers and open-pollinated seeds from four populations of varying sizes and spatial isolation, in and around one of the best-conserved Araucaria Forest remnants in Southern Brazil. The four population types of A. angustifolia include: (1) a continuous forest; (2) a physically isolated cluster located 2 km from the continuous forest; (3) an open population in a field located between the cluster and continuous forest; and (4) a fragment on a private property located 5 km from the cluster. Approximately 28 seeds were collected from ten reproductive trees in each population. We found higher amounts of alleles (113) and exclusive alleles (25) in the continuous forest than in the other populations. The multilocus paternity correlation was significantly higher and effective number of pollen donors was significantly lower in the private population, decreasing the diversity and consequently the variance effective size of families sampled from that population. However, despite its isolation from the other studied fragments, the private population had the second highest number of alleles as well as unique alleles from the other populations. Therefore, strategies for A. angustifolia conservation should focus not only on larger populations, such as those found in protected areas, but also include smaller and isolated fragments on private properties as these populations are able to maintain high levels of genetic diversity and functional connectivity between isolated stands across a landscape.  相似文献   

6.
Abstract. Land flatworms (Platyhelminthes: Terricola) are sensitive to environmental changes and might be used as biological indicators of the degree of disturbance of their habitats. Nevertheless, studies on the structure of land flatworm communities are rare. In the present study, we investigated the terrestrial flatworm communities in two types of ombrophilous forest, Atlantic forest and Araucaria forest, aiming to answer the following questions: (1) Is the community structure of the two types of ombrophilous forest different? (2) Are there differences, regarding community structure, among distinct fragments of Araucaria forest? (3) Are there indicators of edge effects in these communities? The study site, the National Park of Aparados da Serra, is mainly covered, at high altitudes, by fragments of Araucaria forest immersed in a matrix of open areas (grasslands) and, in low altitudes, by a continuous Atlantic forest. We conducted monthly surveys in the two types of forest with three replications per forest type over a period of 2 years. Results indicated that: (1) community structure is clearly distinct between the two types of forest, as well as among fragments of the Araucaria forest; (2) there are no apparent edge effects; (3) the diversity indices of the two types of ombrophilous forest are not significantly different (Atlantic forest—H′=2.87, Araucaria forest—H′=2.55; p>0.05); and (4) there are significant differences in diversity indices between two fragments of Araucaria forest (H′=2.92 and 2.47; p<0.001). The following factors could affect community structure: type of vegetation, degree of human disturbance, and abiotic factors, such as pH and temperature.  相似文献   

7.
Abstract Araucaria Forest expansion over grassland takes place under wet climate conditions and low disturbance and it is hypothesized that isolated trees established on grassland facilitate the establishment of forest woody species beneath their canopies. Forest with Araucaria angustifolia is a particular type of Brazilian Atlantic Forest and the main forest type on the highland plateau in south Brazil, often forming mosaics with natural Campos grassland. The objectives of this paper were to evaluate the role of isolated shrubs and trees as colonization sites for seedlings of Araucaria Forest woody species on grassland, to determine which species function as preferential nurse plants in the process and the importance of vertebrate diaspore dispersal on the structure of seedling communities beneath nurse plants. The study was conducted in São Francisco de Paula, Rio Grande do Sul State, where we sampled isolated shrubs and trees in natural grassland near Araucaria Forest edges. Seedlings were counted and identified, and seedling diaspore dispersal syndromes, size and colour were registered. We detected 11 woody species with a potential role in nucleating grassland colonization by forest species. Beneath the canopies of nurse plants more forest species seedlings were found compared with open field grassland and the seedlings had diaspores mostly dispersed by vertebrates. Also, more seedlings were found under the canopy of A. angustifolia than beneath other nurse plant species. We conclude that A. angustifolia trees established on grassland act as nurse plants, by attracting disperser birds that promote colonization of the site by other forest species seedlings, and that under low level of grassland disturbance, conservation of frugivorous vertebrate assemblages may increase forest expansion over natural grassland and also facilitate the regeneration of degraded forest areas.  相似文献   

8.
We examine the effects of forest fragmentation on the structure and composition of tree assemblages within three seasonal and aseasonal forest types of southern Brazil, including evergreen, Araucaria, and deciduous forests. We sampled three southernmost Atlantic Forest landscapes, including the largest continuous forest protected areas within each forest type. Tree assemblages in each forest type were sampled within 10 plots of 0.1 ha in both continuous forests and 10 adjacent forest fragments. All trees within each plot were assigned to trait categories describing their regeneration strategy, vertical stratification, seed-dispersal mode, seed size, and wood density. We detected differences among both forest types and landscape contexts in terms of overall tree species richness, and the density and species richness of different functional groups in terms of regeneration strategy, seed dispersal mode and woody density. Overall, evergreen forest fragments exhibited the largest deviations from continuous forest plots in assemblage structure. Evergreen, Araucaria and deciduous forests diverge in the functional composition of tree floras, particularly in relation to regeneration strategy and stress tolerance. By supporting a more diversified light-demanding and stress-tolerant flora with reduced richness and abundance of shade-tolerant, old-growth species, both deciduous and Araucaria forest tree assemblages are more intrinsically resilient to contemporary human-disturbances, including fragmentation-induced edge effects, in terms of species erosion and functional shifts. We suggest that these intrinsic differences in the direction and magnitude of responses to changes in landscape structure between forest types should guide a wide range of conservation strategies in restoring fragmented tropical forest landscapes worldwide.  相似文献   

9.
Araucaria araucana seeds and seedlings respond to wounding after48 h with a 3- to 4-fold increase of hydroxyproline-rich glycoproteins(HRGP) in the cell walls of the embryo and with a 15-fold increasein the cell walls of the megagametophyte. The megagametophytewalls accumulate six times more hydroxyproline per µgof cell wall protein than the embryo in this wound response.Tissue immunoprints of different parts of seeds and seedlingsobtained with polyclonal antibodies raised against HRGP fromcarrot roots or soybean seed coats indicate that the responseis due to an increase in a protein similar to the ones seenin carrot roots or soybean seed coats. Western blots of embryoand megagametophyte cell wall proteins subjected to SDS-PAGEshow three bands that cross-react with these antibodies. Ina native cationic gel system followed by Western blot analysis,only two bands react with these antibodies. Expression of suchproteins in Araucaria araucana seeds seems to be developmentallyregulated and tissue specific, since they are present mainlyin the megagametophyte and the root cap of the embryo. Key words: Araucaria araucana, seeds, seedlings, cell walls, hydroxyproline-rich glycoproteins  相似文献   

10.
Summary The growth ofAraucaria cunninghamii Ait. planted in lateritic podzolic soils on dry sclerophyll forest sites in southern Queensland is known to be limited primarily by lack of nitrogen; phosphorus is a secondary deficiency. However, Araucaria can be grown without fertilizers on these sites by underplanting to Pinus.A factorial fertilizer trial was used to establish critical levels of foliage nitrogen and phosphorus in Araucaria. The critical level of nitrogen depends  相似文献   

11.
Abstract. Araucaria forests are among the most threatened biomes of one of the world's 25 biodiversity hotspots, the south Brazilian Atlantic Rain Forest. This study was focused on flatworm community structure in three protected areas located on the eastern border of the Araucaria Plateau in south Brazil. We addressed three main questions: (1) How species‐rich are Araucaria forests? (2) Are there any differences in the community structure within the three areas? (3) What is the distribution pattern of land flatworms in this type of forest? A total of 51 flatworm species in ten genera and two subfamilies were found. Non‐metric multidimensional scaling analysis showed that the assemblage structure differed within the three areas. The abundance and richness varied in time, being affected by an interaction between season and areas. Araucaria forests on the eastern border of the Araucaria Plateau should be considered a hotspot of land planarian diversity, harboring an estimated 64 species. The high combined species richness in the protected areas studied emphasizes the importance of their preservation. Notwithstanding their close proximity, they are not redundant in maintaining regional biodiversity.  相似文献   

12.
TOMPSETT  P. B. 《Annals of botany》1982,50(5):693-704
Seeds of Araucaria hunsteinii K. Schum. dried quicker at 29°Cthan at 19°C and quicker with the seed-coat removed thanwhen intact; seeds enclosed in polyethylene bags increased inmoisture content. At 15°C, seeds in a flow of air driedquicker than seeds in a box with silica gel, which in turn driedquicker than seeds in a box with no desiccant. No loss of germinationability occurred on drying fresh seed from 53 to about 32 percent moisture content (fresh weight basis); during further desiccationthe percentage germination was related to percentage moisturecontent in the form of a sigmoid curve, culminating in a completefailure to germinate at approximately 14 per cent moisture content.A consistent relationship was observed for all treatments andthe mean critical moisture content for seed death (failure togerminate) was near 23 per cent. Excised embryos grew on 1 percent agar but died if previously subjected to 14 h of desiccationat 15°C. In contrast, no relationship was found between germination andmoisture content of A. cunninghamii D. Don on desiccation from21 to 7 per cent moisture content. Possible causes for the observeddifference in response to desiccation are discussed and methodsfor seed storage are considered. Araucaria hunsteinii, Klinkii pine, Araucaria cunninghamii, Hoop pine, desiccation, seed longevity, storage of seeds  相似文献   

13.
Abstract: Tropical and subtropical forests once covered large areas of Central and South America. An important member of forests of the southern hemisphere is the genus Araucaria. Because of clear cutting only small remnants of Araucaria angustifolia forests still exist in Southern Brazil. Attempts at reforestation have had only limited success because of lack of knowledge about the environmental requirements of this species. This is especially true with respect to the root/fungus symbiosis (mycorrhiza) which is necessary for enhanced water and nutrient uptake and present in more than 90 % of land plants. Analysis of the root systems of Araucaria trees from forest and grassland (campo) sites revealed mycorrhizal structures (appressoria, penetration and coiled hyphae, vesicles, arbuscules, spores) which are characteristic for the arbuscular mycorrhiza (AM) type. The spores of AM fungi at both sites - forest and campo - were identified. The biodiversity at the forest site was much higher, with 13 species, whereas only 6 different species could be identified at the campo site. Glomus and Acaulospora were the only genera present at the campo. The forest, however, also contained spores of Entrophospora and Scutellospora. In addition to the greater biodiversity, the spore number in soil as well as the percent mycorrhizal colonization in roots were significantly higher at the forest site than at the campo site. Because of the low frequency of hyphal coils and the dominating intercellular growth of hyphae, these mycorrhizas can be classified as an Arum -type, which is the first report of this kind in gymnosperms.  相似文献   

14.
In an intermast year of very low seed production, we studied seed handling in an Araucaria araucana (Araucariaceae) forest in Neuquén Province, Argentina. Rodents identified in 844 photographs from automatic cameras removed 589 seeds marked with small embedded magnets. Within 12 days of removal, 460 were recovered using a magnetic field locator; 79% of recoveries were from burrows and caches in litter or soil. Rodents exhibited a diversity of seed‐handling strategies and differed in their potential as dispersal agents. Seed removal was most likely between 15.00 hours and 21.00 hours, but diurnal and nocturnal visits were recorded for all species. Oligoryzomys longicaudatus (Cricetidae) was a seed predator that took 8% of marked seeds and left none whole. Chelemys macronyx (Cricetidae) and Rattus norvegicus (Muridae) removed 25% and 19% of marked seeds respectively. These two species deposited the majority of seeds in groups of 10 or more in burrow larders that were unfavourable seedling establishment sites far from daylight. Abrothrix longipilis (Cricetidae) removed 43% of seeds, scatter‐hoarded the largest percentage of whole seeds (37%), moved some seeds farther than 40 m, and left them in favourable seedling establishment sites near daylight. For all species, the number and proportion of seeds cached whole increased as more seeds were removed. Rodents, especially A. longipilis, may play an important role in regeneration of A. araucana. Seed‐handling strategies and potentially effective dispersal are discussed in terms of masting seed production.  相似文献   

15.
Araucaria bidwillii Hook. and Araucaria cunninghamii Don D. are two species of conifers whose seeds belong to different physiological categories: A. bidwillii seeds are recalcitrant, while A. cunninghamii seeds are orthodox. The extraction of enzymes and storage proteins was carried out from A. bidwillii and A. cunninghamii megagametophytes. The endopeptidase activities of both species were assayed with azocasein and with haemoglobin; the exopeptidase activities were detected by various N-carbobenzyloxy-dipeptides and L-leucine p-nitroanilide. The use of appropriate proteinase inhibitors, i.e. pepstatin A, ethylenediaminetetraacetic acid and trans-epoxysuccinyl-L-leucylamido-(4-guanidino)butane, showed the presence of aspartic and metallo proteinases and the absence of the cysteine ones both in A. bidwillii and in A. cunninghamii ungerminated seeds. Since the results do not show differences between the types of enzymes in the ungerminated araucarian seeds and those present in some ungerminated angiosperm seeds (barley, wheat, maize, rice, buckwheat), we conclude that their physiological role is similar. The electrophoretical analyses of soluble and insoluble storage proteins of A. cunninghamii showed patterns similar to those found in other gymnosperms, while the storage protein patterns of A. bidwillii seeds were rather atypical.  相似文献   

16.
This study compares demographic parameters and population dynamics for high disturbance (maquis) and low disturbance (rain forest) environments of the montane conifer, Araucaria laubenfelsii, in New Caledonia. The establishment, growth, survival and reproduction of ca 2500 individuals were followed in permanent plots over 10 yr. Growth and survival rates for A. laubenfelsii show that it is a long-lived, slow growing tree, with evidence of suppression in the sapling size classes in mature rain forest. Growth rates for all size classes are generally faster in maquis than rain forest. Transition matrix analyses estimated positive rates of population increase (λ values>1), with populations expanding in maquis, and stable in mature forest. Araucaria laubenfelsii is able to regenerate continuously in maquis and early successional rain forest, but recruitment is limited in older stands. Life table response experiment analyses showed that reproduction, and transitions from sapling to mature tree stage, contributed positively to λ in maquis, but negatively in forest. Araucaria laubenfelsii on Mont Do can be considered a long-lived pioneer, with early maquis colonizers helping to drive succession from maquis to forest. While opportunities for recruitment decline with time as rain forest sites develop a closed canopy, occasional gap phase recruitment, combined with disturbance by cyclones, landslides and fire, provide opportunities to ensure species persistence. Understanding contrasting population dynamics of A. laubenfelsii in maquis and rain forest will better facilitate conservation management of this species, particularly given current high rates of land conversion and degradation in New Caledonia. Abstract in French is available at http://www.blackwell-synergy.com/loi/btp  相似文献   

17.
Southern Chile experienced serious deforestation during the past century and it is projected that by the year 2025 Chile will be devoid of native forests. One of the most important endemic tree species of the country and at the same time one of the most endangered ones is Araucaria araucana (Mol.) C. Koch, the monkey-puzzle tree. It grows in the Andes Mountains, homeland of the indigenous Mapuche Pewenche people who depend on this tree. This paper is based on participatory field research with a Mapuche Pewenche community in the southern Chilean Andes on their ecological knowledge, values, use and management of the Araucaria araucana forest. It attempts to reveal how indigenous people and their knowledge contribute to the sustainable management of these forests. The paper (1) illustrates the complexity of indigenous ecological knowledge of Araucaria araucana and its efficacy in native forest management, (2) explores the link between the conservation and use of biodiversity by the indigenous people, and (3) provides answers relevant to native forest management and conservation strategies ex-situ and in-situ incorporating indigenous and scientific knowledge, thus providing a contribution towards integrated natural resource management.  相似文献   

18.
Firn J  Erskine PD  Lamb D 《Oecologia》2007,154(3):521-533
We investigated the relationship between plant diversity and ecological function (production and nutrient cycling) in tropical tree plantations. Old plantations (65–72 years) of four different species, namely Araucaria cunninghamii, Agathis robusta, Toona ciliata and Flindersia brayleyana, as well as natural secondary forest were examined at Wongabel State Forest, in the wet tropics region of Queensland, Australia. Two young plantations (23 years) of Araucaria cunninghamii and Pinus caribaea were also examined. The close proximity of the older plantations and natural forests meant they had similar edaphic and climatic conditions. All plantations had been established as monocultures, but had been colonised by a range of native woody plants from the nearby rainforest. The extent to which this had occurred varied with the identity of the plantation species (from 2 to 17 species in 0.1 ha blocks). In many cases these additional species had grown up and joined the forest canopy. This study is one of the few to find a negative relationship between overstorey plant diversity and productivity. The conversion of natural forest with highly productive, low-diversity gymnosperm-dominated plantations (young and old Araucaria cunninghamii and Pinus caribaea) was found to be associated with lower soil nutrient availability (approximately five times less phosphorus and 2.5 times less nitrogen) and lower soil pH (mean = 6.28) compared to the other, less productive plantations. The dominant effects of two species, Araucaria cunninghamii and Hodgkinsonia frutescens, indicate that ecosystem functions such as production and nutrient availability are not determined solely by the number of species, but are more likely to be determined by the characteristics of the species present. This suggests that monoculture plantations can be used to successfully restore some functions (e.g. nutrient cycling and production), but that the level to which such functions can be restored will depend upon the species chosen and site conditions. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

19.
Biodiversity and Conservation - One of Brazil’s most threatened tropical biome is the Atlantic Forest. This biome has distinct forest formations, as the Araucaria Mixed Forest, a sub-tropical...  相似文献   

20.
We examined the effect of thermal shock on the germination of seeds of three conifers, two introduced (Pseudotsuga menziesii and Pinus ponderosa), and one native to Patagonia (Araucaria araucana). Previous research has suggested increased susceptibility to invasions in burnt areas, and therefore, the effect of simulated fire (heat) on seed germination in these native and introduced species was compared. Seeds were heated to two different heat intensities (50°C and 100°C) for 1 or 5 min, which is within the temperature range reached in the upper soil layers during forest fires. Germination tests were then carried out in a growth chamber. The heat treatments had a negative effect on the germination of P. menziesii at temperatures of 100°C, and a negative effect on the germination of P. ponderosa at the temperature of 100°C and the exposure of 5 min. The heat treatments had no affect at all on A. araucana. The species with larger seeds (A. araucana) had higher survival rates after the thermal shocks. Also intraspecific differences in seed sizes possibly point at larger seeds surviving thermal shocks better than smaller seeds. In addition, thermal shock caused a delay in the onset of germination in the two introduced species, while it did not change the time for germination in A. araucana.  相似文献   

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