首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
The vegetation near the summit of the volcano Usu was destroyed during eruptions in 1977 and 1978 by 1–3 m thick layers of volcanic deposits. Thereafter, the vegetation gradually recovered and by 1984 134 plant species were recognized of which 95 species had established by vegetative reproduction, 18 by seed immigration from elsewhere, 5 by artificial introduction for soil erosion control and 17 species from viable seeds buried in the former topsoil. The summit area was still covered by thick layers of volcanic ash, which were however rapidly eroded by rains. Vegetatively reproducing plants such as Petasites japonicus var. giganteus and Polygonum sachalense contribute more effectively to the revegetation process than plants of other types of origin.  相似文献   

2.
Vegetation dynamics were monitored from 1983 to 1987 near the summit of the volcano Usu which had almost completely been deforested by 1–3 m thick volcanic deposits in 1977–1978. A permanent quadrat survey for five years confirmed the high mortality of seedlings. Since seedling mortality appeared mostly due to the frequent erosion of the volcanic deposits, ephemeral annuals and well-rooted perennials or woody plants were successful here. The high mortality of seedlings resulted in intensive fluctuation of plant density in all habitats. However, owing to the expansion of perennials, once they became established, the plant cover increased from year to year. In particular, Polygonum sachalinense and Petasites japonicus var. giganteus, seeds of which were frequently provided from their community vegetatively recovered on the wall of the caldera rim soon after the eruptions, were remarkably contributive to the revegetation. The excavation of those perennial plants demonstrated that they were derived not only from the seeds but also vegetatively from the old stumps buried in the former topsoil by extending their rhizomes up to the present ground surface.  相似文献   

3.
In 1987, a study on buried seed populations was conducted in the crater basin of Mt. Usu, a volcano located in northern Japan, where the vegetation had beeen almost completely destroyed by eruptions in 1977 and 1978. The former vegetation had consisted of grassland and broad-leaved forest. In the areas formerly occupied by this grassland and forest, 2128.0 and 1985.3 seeds per square meter, respectively, were extracted from 12 blocks of the former topsoil using a floattion method. This revealed that many seeds were still viable even after ten years of burial under thick volcanic deposits. The seeds were distributed more in sandy soil than in rocky soil of the former topsoil. Twenty-five species, most of which favored grassland, were detected in both the former grassland and forest. From comparison of α-and β-diversities between the grassland and forest, the structure of the buried seed population was considered likely to have been more diverse in the forest than in the grassland. The determinants of composition of the buried seed populations were discussed with reference to the former vegetation and soil characteristics.  相似文献   

4.
The eruptions of 1977–1978 on Mount Usu in northern Japan resulted in the almost complete destruction of vegetation by a 1–3-m-thick accumulation of volcanic deposits. Erosion created gullies that removed these deposits and frequently exposed the old original soil. I previously confirmed that seedlings of 14 species (eight annual and six perennial herbs) emerged from seeds buried in the original topsoil. To clarify the role of the seed bank on volcanic succession, I monitored seedlings of seed bank species from 1983 to 1992. Nearly all the annuals, such as Polygonum longisetum and Rorippa islandica, originated from the seed bank. However, seed supply from the seed bank declined with time. Because seedling mortality was extremely high and reproductive success was low, due mostly to the instability of ground surface, these annuals emerged for several years but disappeared after 1989. The nitrogen-fixing and stoloniferous perennials, Trifolium repens and Lotus corniculatus var. japonicus, were derived only from the seed bank. They have gradually increased in cover and have become large enough to flower. The other perennials derived from the seed bank, most of which produce short rhizomes, did not increase in cover annually and thus contributed less to revegetation than nitrogen-fixing stoloniferous species. The fate of perennials seems to be dependent on the types of rhizome and stolon systems. Although recruitment from the seed bank was restricted to gullies, the seed bank was the major source of annuals and of nitrogen-fixing perennials in the gullies. Succession in the gullies was substantially different from that which occurred outside the gullies where plants mostly originated from seed immigration and vegetative reproduction from surviving plants, and annual and nitrogen-fixing plants were absent.  相似文献   

5.
The establishment success of woody plant species at 56 revegetation sites, four to 26 years old, across the Meandu open‐cut coal mine in south‐east Queensland was assessed. The revegetation process involved returning stockpiled topsoil, deep ripping and mechanical sowing of a mix of native seeds. Blakes Wattle (Acacia blakei) and less often Black Wattle (A. leiocalyx), both primarily derived from respread topsoil seed, dominate the vegetation canopy at 59% and 20% of revegetation sites, respectively. The additional sowing of seeds of many tree and shrub species within the sites has had limited success with most failing to persist or grow well. Revegetation management, for example selective thinning of acacias (Acacia spp.) saplings within the first 5 years is recommended to release the competition pressure on the poorly performing tree species. This will also allow opportunities for other less well represented shrub and herb species to persist. This study has shown that a range of tree and shrub species, including Eucalyptus spp., are performing poorly under the current revegetation regime, suggesting adjustments to revegetation species selection and/or methodologies are needed. The natural colonization of woody native species within the sites from nearby remnant vegetation is shown to be limited to only four species, and therefore is unlikely to significantly supplement the species diversity of the revegetation.  相似文献   

6.
Canonical correspondece analysis (CCA) was applied to explore revegetation patterns during early succession on Mt Usu. Vegetation was buried by deposits of ash and pumice from 1 to 3 m in depth from the 1977–78 eruptions. Three habitats were selected: tephra, tephra in gully and original surface. Plant density and plant cover data were analyzed separately. Environmental factors consisted of five quanticative variables (organic matter, elevation, distance from colonizing source, erosion and deposition of volcanic deposits) and three nominal variables (habitat types: tephra, tephra in gully and original surface). Canonical correspondence analysis showed that the original surface played a special role in vegetation development because the old topsoil supplied both nutrients and seed-bank species. The CCA also suggested that the environmental factors that influence plant density and cover differ. Distance from colonizing source affected plant density while erosion affected cover. Using CCA, factors could be distinguished that influenced seedling establishment from vegetation expansion and vegetation recovery dynamics could also be more clearly interpreted.  相似文献   

7.
The effects of plant‐derived smoke and of heat on the emergence of seedlings from seeds were assessed. Seeds had been stored in forest topsoil used for mine site rehabilitation. The study was carried out in a dry sclerophyll, spotted gum (Corymbia maculata), forest community at the Mount Owen open‐cut coal mine in the Hunter Valley region of New South Wales. Samples of the surface 2.5 cm of topsoil were either exposed to cool smoke from eucalypt foliage for 60 min, heated to 80°C, or left untreated. Seedling emergence from the seed bank in this soil was then monitored in a glasshouse. Within the first month, smoke alone promoted a 4.3‐fold increase in the density of seedlings relative to control. There were 540 emergents per m2 in the control and 2309 per m2 in the smoke treated topsoil. Many annual and perennial herbs emerged but grasses responded most strongly to smoke. Germination in seven of the 20 grass species was promoted by smoke. Smoke promoted the germination of some introduced species as well as native species, and accelerated the rate at which seedlings emerged, although these differences sometimes declined with time. Heat also stimulated germination but smoke and heat stimuli appeared to be complementary in their promotion of seedling emergence from the topsoil seed bank. Each treatment increased the density of different species, enhanced the species richness of different components of the seed bank, and had different effects on the rate of emergence. The results suggest that increased seed germination in the field immediately following a moderate intensity fire may sometimes be the result of smoke stimulation and sometimes the result of heat stimulation of the soil seed bank. These findings may have important implications for minesite revegetation programs where topsoils are replaced after mining and rapid germination of seeds stored in these soils is required during short periods when conditions are favourable for germination.  相似文献   

8.
Topsoil is a valuable resource for revegetation of mine sites as it contains seeds of plant species indigenous to the local environment. As mine site restoration is undertaken after the completion of mining, it is a common practice to stockpile topsoil in preparation for restoration activities. While many studies have found a decrease in seedling emergence with increasing stockpile age in temperate regions around the world, a few examine the effect of stockpile age on topsoil seed bank and seedling recruitment in arid environments. Seed longevity is promoted under dry conditions whereas viability loss is increased under warm and moist conditions. Here in a study in Australia's Great Sandy Desert, the effect of topsoil storage age and method of storing topsoil (under‐cover and exposed) on seedling recruitment was examined for a major gold mining site. There was a trend for lower seedling emergence (68% lower) and species richness (30% lower) from topsoil stored for 2 years than from topsoil direct returned and topsoil stored for 1 year. Seedling emergence from topsoil stockpiled for 2 years was more than 3.5‐fold higher from covered topsoil stockpiles than uncovered topsoil stockpiles. For two ecologically dominant species, after 2 years of storage, seedling emergence of the grass Triodia basedowii was 13% of direct returned topsoil and seedling emergence of the shrub Acacia stellaticeps was 68% of direct returned topsoil. The implication of the decline in seedling emergence from topsoil stockpiling on mine site revegetation in a biodiverse arid region is discussed.  相似文献   

9.
Seed dispersal and early revegetation processes were studied in an area devastated by a debris avalanche that occurred on volcano Ontake, Central Japan in 1984. The avalanche was initiated by a volcanic earthquake, and a 3.4 x 107 m3 land mass destroyed the vegetation over 700 ha. The revegetation of the first five years was slow in the area of higher elevation (subalpine area). Both the speed of revegetation and the species richness of trapped seeds varied with the elevation. The post-disturbance vegetation on the deposit with surface soil or plant fragments was richer in species than that without any surface soil. Almost all of the seeds caught by sticky traps and most of the species with frequent occurrence in the vegetation after disturbance were wind dispersed. Wind dispersal was especially important on the deposit without surface soil or plant fragments.  相似文献   

10.
Question: How do temporal changes in plant communities occur after volcanic eruptions? What characteristics determine successional divergence or convergence? Location: The summit area of Mount Usu, northern Japan, completely destroyed by 1‐3 m of thick ash and pumice during the 1977‐1978 eruptions. Habitats were classified into three types: gullies where the pre‐eruption topsoil was exposed due to the erosion of tephra (EG), gullies covered with tephra (CG), and outside of gullies covered with thick tephra (OG). Methods: Plant community structure was monitored for 15 years from 1983 to 1997 in 14 2 m × 5 m permanent plots. The data were summarized by species diversity, life form, and the detrended correspondence analysis. Results: The common species were perennial herbaceous plants, but habitat preferences differed between species. Seed bank species, including a nitrogen fixer Trifolium repens, were dominant in EG, and excluded the establishment of the later colonists. Pioneer trees slowly increased in cover. The detrended correspondence analysis indicated that species composition in the earlier stages did not differ greatly between plots. Thereafter, three patterns of temporal community changes were observed: seed bank species persisted in EG, and in OG and CG forest development proceeded or community structure did not change greatly. Conclusion: Pre‐eruption topsoil contributed to revegetation by the supply of seed bank and nutrients in the earliest stages, but resulted in the delay of forest development due to the persistence of seed bank species. Plant community divergence was driven by the persistence of earlier colonists.  相似文献   

11.
A survey of springtails was conducted in 1984 on Volcano Usu which suffered damage to it's ecosystem from eruptions in 1977 and 1978. The summit area, almost completely deforested by the eruptions, was still inhabited by many forest species such asDesoria notabilis, Willowsia sp. 2,Pseudachorutes sp. 2,Isotoma sp. 4,Tullbergia yosii, Onychiurus sp. 1,Entomobrya sp. 2,Isotomiella minor, Proisotoma sp. 2,Xenylla sp.,Neanura frigida, etc. These species preferred standing or fallen dead trees, mosses, bark chips, former topsoils and soil around the root of plants. The fauna in the summit area was most similar to that of coniferous or broad-leaved forests surveyed on the foot of the mountain. This suggests that the 1977–78 eruptions did not exterminate these springtail species which probably survived on the standing trees or in the former topsoil.  相似文献   

12.
Invasive expansion of Robinia pseudoacacia is a worldwide problem. A method to control existing R. pseudoacacia populations is urgently needed. In addition to plants above the ground, seed banks should be targets for the management of R. pseudoacacia. We targeted an old plantation of R. pseudoacacia and its surroundings in a headwater basin to determine the spatial characteristics of the distribution. We established 49 square plots in which the number of buried seeds and seeds dispersed by wind, and several other related environmental factors were surveyed. The relationship between the spatial extent of seeds dispersed by wind and the distribution of the seed bank was analyzed. Environmental factors that potentially influenced the density of buried seeds were also analyzed. We found that barochory and anemochory were the main factors that contributed to R. pseudoacacia forming seed banks. The greatest factor controlling the density of buried seeds was slope angle; thus, transfer of seeds by rolling is important for the formation of seed banks in headwater basins. From these results, some guidelines for the management of seed banks in headwater basin are presented. First, unnecessary soil disturbance within about a 100-m buffer area around seeding trees should be avoided. Second, plantation soil from gentle slopes should not be applied for revegetation of other locations. In situations where R. pseudoacacia populations are planted on steep slopes near streams, there is a chance that seeds will be carried away and form seed banks at lower or downstream sites.  相似文献   

13.
We explored different treatments to enhance the probability of sowed seeds of two early successional (ES, Cecropia obtusifolia and Ochroma pyramidale) and two late successional (LS, Brosimum costaricanum and Dialium guianense) species to escape predation and germinate in abandoned cattle‐raising pasture fields in Southeastern Mexico. ES species were sown in groups of 50 seeds under three treatments: invertebrate exclusion, burial, and exposition to seedeaters. LS species were sown in groups of 10 seeds under three treatments: vertebrate exclusion, burial, and exposition to seedeaters. We registered seed predation and germination 2, 4, 8, 16, 32, and 64 days after the initial sowing. Overall, ES showed higher predation rates (mean ± SE = 0.45 ± 0.07 seed seed?1 day?1; n = 3) than LS species (0.09 ± 0.02 seed seed?1 day?1). Cecropia obtusifolia was completely predated in all treatments after 8 days. Burial and exclusion treatments reduced final predation in circa 6% for O. pyramidale, relative to that of exposed seeds (85% after 8 days); most germination occurred in buried seeds (3.7%). In B. costaricanum, burial enabled germination by 10%; exposed and excluded seeds were removed 100%. Dialium guianense showed 12% germination in buried seeds and circa 20% of the seeds were not removed after 64 days. Direct sowing would be a recommended rainforest restoration practice for species with relatively large seeds if deposited in groups and buried. Studies which address variation across numerous sites are necessary in order to generate more consistent seed predation patterns and rainforest restoration principles in tropical pastures.  相似文献   

14.
Abstract Germinable seed stores were measured in jarrah forest soils at six sites during one year. The overall mean seed content to a depth of 5 cm was 292 seeds m?2. There was a significant seasonal difference, with a maximum of 435 seeds m?2 in summer, after the majority of species in this Mediterranean ecosystem had flowered and set seed, and a minimum of 207 seeds m?2 in winter. There were also large site differences in both the densities of seed present and the species represented in the soil seed store. More than 85 species were represented in the germinable seed store from a total sampling area of 17.28 m2. The germination of Acacia drummondii, Acacia pulchella, Bossiaea aquifolium, Kennedia coccinea, Lasiopeialum floribundum and Trymalium ledifolium were significantly increased by heating the soil. Smoke produced a significant positive germination response in one species (Trymalium ledifolium). To maximize the contribution of the soil seed store to mine rehabilitation, the ideal revegetation sequence is to collect the topsoil immediately after clearing the vegetation in summer, immediately return the soil to an area to be revegetated, and carry out all earthmoving, landscaping and seedbed preparations prior to the onset of the autumn rains.  相似文献   

15.
The production, density and environment of buried seeds and the temperature response of germinating seeds in Trapa natans var. japonica Nakai were ascertained. The mechanism of high reproductivity, tolerance of the plant for eutrophication and the stability of the stand in an eutrophic lake are discussed. The mean fresh weight of seeds was about 7.2 g, and the density of liver and dead seeds in April ranged 66.7 to 80.0 m-2 and 26.7 to 97.8 m-2, respectively. The threshold temperature that breaks dormancy and promotes germination in the lake was the low temperature, 8°C. The dormancy of buried seeds was almost broken under the field condition in January. The rate of germination obtained by the field experiment, and the estimation from the density of buried seed and the number of seeds germinated at the stand, were 87% and 60%, respectively. It was estimated that about 30% of the seedlings died before the floating leaf reached water surface. A rosette produced less than three seeds a year, which were fewer than for another Trapa, but the size of the former was larger. The number of seeds changed year by year, but the size-distribution pattern of seeds did not change with years, nor was it affected by the density of rosettes. The reason why T. natans var. japonica could succeed in eutrophic waters was attributed to reproductive strategy. The stand could recover by increasing the number of rosettes through the great branching ability of the main stem, even when the density of buried seeds was greatly decreased in the previous year.  相似文献   

16.
The goal of the present study was to assess a soil seed bank as an input seed source for revegetating lead/zinc (Pb/Zn) mine tailings. The seed bank source was abandoned farmland, whose top 10‐cm layer of topsoil contained 6,850 ± 377 seeds/m2 from 41 species. The seeds in the soil were principally distributed in the upper 0–2 cm, which held 75.8% of total seeds and 92.7% of species composition. The top 2‐cm layer of topsoil may be sufficient to serve the purpose of providing a seed source for revegetation on derelict lands, including mined lands. Four different thicknesses of topsoil (1, 2, 4, and 8 cm, redistributed from the total 0–10‐cm layer from the farmland) were field‐tested on the Pb/Zn mine tailings. There was no significant difference in seedling density among the 4 thickness treatments. Many seeds in the treatments with more than 1‐cm of topsoil were unable to emerge from the deeper layer. Seedlings in plots with topsoil of 1‐, 2‐ and 4‐cm failed to establish within 1 year due to the extremely high acidity (pH 2.39 to 2.76). A shallow layer of topsoil cannot neutralize the sulfuric acid generated from oxidation of pyrites in the tailings. For establishment of seedlings on metalliferous lands, an insulating layer such as subsoil, building rubble, or domestic refuse is necessary before covering with valuable topsoil. The woody legume Leucaena leucocephala grown on the tailings with a topsoil cover of 8‐cm was the most dominant species. Lead was accumulated in root, branch, stem bark, and xylem, which accounted for more than 80% of the total metal concentration in the plant. This portion of Pb will reside in the plant for a long period, while the smaller portion of Pb in the leaf (about 15%) could be returned to the environment as litter during growth. Woody plants may have an advantage in metal‐phyto‐remediation over herbaceous plants.  相似文献   

17.
The topsoil that contained the seed bank became buried under thick tephra after the eruptions of Mount Usu during 1977 and 1978. To determine the seed bank potential of the topsoil 20 yr after the eruptions, i.e., in 1998, 408 100-cm(3) samples were excavated under 115-185 cm of volcanic deposits. The topsoil was collected at 10-cm intervals along the horizontal scale and was divided into a 0-5 cm deep upper layer and a 5-10 cm deep lower layer. The seed bank was estimated by both the germination (GM) and flotation (FM) methods. In total, 23 species with an average seed density of 1317 seeds/m(2) were identified by GM, and 30 species with a density of 2986 seeds/m(2) were extracted by FM. The dominant species was Rumex obtusifolius, and perennial herbs, such as Carex oxyandra, Viola grypoceras, and Poa pratensis, were common. For nine species this study provided the first records for field seed longevity >20 yr. The seed density in the upper layer was double that in the lower layer, and the horizontal distribution was heterogeneous even at 10-cm intervals. We concluded that the seed bank has retained the original structure of the seed bank under the tephra and will persist longer with soil water content between 20 and 40%, no light, and low temperature fluctuations (±0.17°C of standard deviation in a day).  相似文献   

18.
Izumi Washitani 《Oecologia》1985,66(3):338-342
Summary The germination of seeds of Amaranthus patulus Bertol., is known to be sensitive to leaf-transmitted light. Seeds were enclosed in transparent polyester-mesh envelopes and placed horizontally in 10-cm deep soil or on the soil surface, beneath a closed vegetation cover in the field. Changes in the numbers of firm intact seeds and of germinable seeds were traced for up to 3 years by periodical retrievals and germination tests. Rapid loss of germinable seeds, mainly due to germination, was observed in the buried seed population, in which only 20% of seeds maintained their germinability after 1 year, and a negligible number after 3 years. In contrast, the seeds placed on the soil surface maintained germinability relatively well: over 80% of seeds remained germinable after 1 year and a low percentage still preserved their germinability after 3 years. Assuming exponential decay in germinability, the decay rates on and in the soil were calculated from the data of the 1-year experiment to be 0.21 and 0.84 year-1 respectively. The fate of seeds that were exposed to canopy light on the soil for a month and then buried was shown to be almost the same as that of the seeds which had been continuously in 10-cm deep soil. Correspondingly, the possibility of the induction of secondary (induced) dormancy by exposure to canopy light was excluded in a laboratory experiment, in which it was found that the imbibed seeds suffering leaf-canopy inhibition of germination exuded some diffusible germination inhibitor responsible for apparent dormancy. Estimation of numbers of A. patulus in the seed bank of an early successional field showed that 3,500 seeds/m2 remained in the soil to the depth of 10 cm after 3 years' exclusion of the species following the production of 700,000 seeds/m2, by a population explosively established after experimental induction of secondary succession.  相似文献   

19.
Abstract Germinable seed stores were estimated for 12–13 year old rehabilitation sites in the jarrah forest over two seasons (autumn and spring). Collected soils were subjected to combinations of smoking and heating treatments before the germination procedure was commenced. The mean topsoil seed reserve to a depth of 10 cm was 1938 seeds m?2. Of this total reserve, more than 80% was found in the upper 5 cm of soil. The topsoil seed reserve of these rehabilitation areas was almost seven times that of the adjacent native jarrah forest (292 seeds m?2; Ward et al. 1997). There was a seasonal effect with autumn-collected soils having significantly more germinable seeds (2723 seeds m?2) than soils collected in spring (1153 seeds m?2). More than half (53%) of the topsoil seed reserve in rehabilitated areas was composed of annual weed species, dominated by Aira caryophyllea, Centaurium erythraea and the native Levenhookia pusilla. Of the total of 70 species identified, 13 species showed significantly higher germination in smoked trays while 11 species exhibited significantly higher germination in heated trays. Species responding to the smoking treatment tended to be annuals while those responding to the heating treatment were typically legume shrub species. Examination of the topsoil seed reserve and the vegetation present in these areas showed that while the species composition was similar between the seed store and the vegetation, there was a large difference in densities, with species occurring at much higher densities in the topsoil than in the vegetation. However, the rankings of species were significantly correlated between the topsoil seed reserve and the vegetation present at the site. The implications of these results to prescribed burning of these rehabilitated areas is discussed.  相似文献   

20.
The extreme species richness of native shrubland vegetation (kwongan) near Eneabba, Western Australia, presents a major problem in the restoration of sites following mineral sand mining. Seed sources available for post-mining restoration and those present in the native kwongan vegetation were quantified and compared. Canopy-borne seeds held in persistent woody fruits were the largest seed source of perennial species in the undisturbed native vegetation and also provided the most seeds for restoration. In undisturbed vegetation, the germinable soil seed store (140–174 seeds · m?2) was only slightly less than the canopy-borne seed store (234–494 seeds · m?2), but stockpiled topsoil provided only 9% of the germinable seeds applied to the post-mining habitat. The age of stockpiled soil was also important. In the three-year-old stockpiled topsoil, the seed bank was only 10.5 seeds · m?2 in the surface 2.5 cm, compared to 56.1 to 127.6 seeds · m?2 in fresh topsoil from undisturbed vegetation sites. In the stockpiled topsoil, most seeds were of annual species and 15–40% of the seeds were of non-native species. In the topsoil from undisturbed vegetation, over 80% of the seeds were of perennial species, and non-native species comprised only 2.7% of the seed bank. Additional seeds of native species were broadcast on restoration areas, and although this represented only 1% of the seed resources applied, the broadcast seed mix was an important resource for increasing post-mining species richness. Knowledge of the life-history characteristics of plant species may relate to seed germination patterns and assist in more accurate restoration where information on germination percentages of all species is not available.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号