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1.
In a field dominated by Formica polyctena Foerst. ants, we examined the effect of seed aggregation on the seed-removal rates of two plant species: a large-seeded obligate myrmecochore Viola odorata L. and a small-seeded diplochore Chelidonium majus L., which was autochorous as well as myrmecochorous. The effect was statistically non-significant in V. odorata but significant in C. majus, with more closely aggregated seeds having higher removal rates. The large seeds of the obligate myrmecochore were more quickly discovered and repeatedly removed by ant workers than were the small seeds of the diplochore.  相似文献   

2.
Soil seed bank composition and vegetative spatial patterns were studied in four mountain meadow communities in the Broto Valley (N. Spain), in order to analyse the differences that might exists between the two life forms. Soil and vegetation samples were taken at 1 m intervals from 10 m × 10 m quadrats in each meadow in one-year study. The spatial distribution of species was analysed along with the calculation of an autocorrelation coefficient which takes account of the relative position of samples: (Moran’s I). The results indicate that the abundance of the majority of the species in the seed bank and in the vegetation are randomly distributed, the percentage of species with a clumped distribution only exceeds 35% in the vegetation of one meadow and none of the taxa identified showed a uniform spatial organisation. The species that were distributed in the seed bank in a clumped pattern in more than one meadow were those of the pioneer species (Anagallis arvensis, Centaurium erythraea, Lamium purpureum and Stellaria media). All of these formed long-term persistent seed banks but were absent in the established vegetation in these meadows. According to the results, there exist not only differences between the spatial distribution of the species present in the same community, but also, that some species change their pattern of distribution according to the life form and to the grassland type in which they are found.  相似文献   

3.
Abstract. The vegetation and soil seed bank in a limestone grassland in southern Sweden were studied in permanent 1-m2 subplots which had been either grazed or not grazed for 17 yr. Of the 92 species recorded, 18 were present only in the seed bank, 28 were more frequent and 24 were less frequent in the seed bank than in the vegetation and 22 were not detected in the seed bank. Among the species present in the seed bank, therophytes were over-represented. Species turnover in the vegetation was estimated from presence/absence data collected in 1980, 1986 and 1990. Turnover was high, but there were no differences between grazed and ungrazed subplots. The turnover for individual species was also high in many cases. There was no clear relationship between the turnover of a species and its presence in the persistent seed bank.  相似文献   

4.
5.
To determine the influence of the proximity of a forest edge on seed bank composition and diversity, we performed a seed bank sampling at ancient deciduous forests bordering intensive arable fields. Also vegetation patterns were taken into account. We hypothised that forest edges may facilitate the entrance of diaspores of invasive species into the forest and the successive incorporation of these species in the forest seed bank. We noticed a substantial influence of the proximity of an edge on seed bank composition at as well the forested side of the edge as the field side. The forest edge zone was limited to 3 m into the forest and the field edge zone extended 3m into the field. The seed bank samples of field and forest edge are characterised by a higher species diversity and seed density and a higher similarity between seed bank and vegetation, compared to field or forest samples. The forest edges contains fewer pioneer species in comparison with the forest interior and more competitive species and species of edges and clearings compared with field and forest samples. The seed longevity index increases towards the forest interior. We can conclude from our data that the forest and edge seed bank are composed by both seeds from recent dispersal processes and local seed set and by seeds originating from past vegetation on the site. Near the edge, actual seed input seems of primal importance. Further towards the forest interior seed input decreases and long-living seeds of past vegetation become more important. Ancient forest edges thus act as a barrier for seeds of species of the surrounding arable field.  相似文献   

6.
H.-J. Yin  H. He 《Plant biosystems》2013,147(3):314-322
Abstract

Dragon spruce (Picea asperata Mast.) is widely planted on clear-cuts from natural subalpine coniferous forests in western Sichuan. To assess the natural regeneration potential of this species in spruce plantations of different ages, field studies on the seed rain, seed bank, and seedling recruitment were conducted in 20-year, 30-year, and 60-year plantations, and in a retained natural forest ca. 150 years old for comparison. Moreover, a series of temperature and light regimes were also designed in March 2003 to test germination/dormancy responses of the P. asperata seeds to different conditions. In the plantations considered, both the densities of seed rain and soil seed bank increased with increasing stand age, whereas they were both low beneath the natural forest partially due to low adult density of P. asperata adult trees. P. asperata has a transient seed bank, and ca. 60% of seeds were found in the litter layer. Seed decay and seed predation were the two most important factors affecting soil seed bank dynamics, which caused a number of seed losses from the soil. Only a small fraction germinated and produced seedlings, and the indices of the losses from the seed bank via germination in the 30-year plantation, 60-year plantation and natural forest were 4.75, 5.10, and 2.80%, respectively. High seedling mortality was observed after seedling emergence, and most of the germinated seedlings died out within one growing season. The P. asperata seeds showed a high percent germination and no significant differences under most light and temperature regimes except for full sunlight or temperature below 5°C. In conclusion, despite a substantial number of seed produced, the high depletion of soil seed, the low seedling output, and high seedling mortality may obscure the natural regeneration potential of this tree species.  相似文献   

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8.
Question: We explored the functional significance of seasonal aerial seed banks in two coexisting, heterocarpic annual Asteraceae with dormant (Chrysanthemum coronarium) and non‐dormant (Anacyclus radiatus) achenes. We hypothesised that the plant achene pool is a significant component of total seed reserves, and that within‐season seedling emergence timing is shaped by achene release patterns. Location: SW Spain. Methods: In an observational study, we established temporal achene release patterns. We also quantified the aerial and soil achene pools throughout the release season, and assessed seedling emergence timing. Sowing experiments were used to explore the influence of achene release dynamics on emergence timing, and to establish achene morph‐specific patterns of between‐year distribution of germination. Results: Achene release extended from late spring to late autumn (Chrysanthemum), or from early autumn to early winter (Anacyclus). Within species, achene morphs differed in release timing. Only in Chrysanthemum, a small achene fraction seemed to persist in the soil, and between‐year germination distribution differed among morphs. In coexisting populations, the Anacyclus plant achene pool was an order of magnitude higher than the soil pool throughout the release season, whereas in Chrysanthemum both pools were of the same magnitude during autumn. Within‐year seedling emergence was significantly staggered beneath parent plants compared with the pattern resulting solely from the germination response in soil, with the exception of Chrysanthemum in one of the two study years. Conclusions: Results suggest that seasonal aerial seed banks are effective within‐season, risk‐reducing traits in ruderal Mediterranean habitats characteristic of the study species.  相似文献   

9.
Pollination and seed dispersal determine the spatial pattern of gene flow in plant populations and, for those species relying on pollinators and frugivores as dispersal vectors, animal activity plays a key role in determining this spatial pattern. For these plant species, reported dispersal patterns are dominated by short-distance movements with a significant amount of immigration. However, the contribution of seed and pollen to the overall contemporary gene immigration is still poorly documented for most plant populations. In this study we investigated pollination and seed dispersal at two spatial scales in a local population of Prunus mahaleb (L.), a species pollinated by insects and dispersed by frugivorous vertebrates. First, we dissected the relative contribution of pollen and seed dispersal to gene immigration from other parts of the metapopulation. We found high levels of gene immigration (18.50%), due to frequent long distance seed dispersal events. Second, we assessed the distance and directionality for pollen and seed dispersal events within the local population. Pollen and seed movement patterns were non-random, with skewed distance distributions: pollen tended moved up to 548 m along an axis approaching the N-S direction, and seeds were dispersed up to 990 m, frequently along the SW and SE axes. Animal-mediated dispersal contributed significantly towards gene immigration into the local population and had a markedly nonrandom pattern within the local population. Our data suggest that animals can impose distinct spatial signatures in contemporary gene flow, with the potential to induce significant genetic structure at a local level.  相似文献   

10.
A nested sampling design was used to describe the spatial patterns for the species richness and composition in the seed bank and vegetation of three Mediterranean old-fields (1, 7, and 15 yr after the last ploughing). Three scales were examined hierarchically: sampling units within plots of 0.25 m2 for the vegetation and of 0.05 m2 for the seed bank, 100 m2 plots within fields, and fields of 1000 m2. In spite of the strong spatial variation among sampling units, species richness and composition of both seed bank and vegetation showed hierarchically structured patterns of heterogeneity, while each old-field was a homogeneous entity. These spatial patterns tended to be partially masked when the data were aggregated at the scale of the plot. Such results stress the use of a nested sampling design for studying variation in species richness and taxonomic composition in both vegetation and seed bank. This design, in combination with CCA, also showed that the vegetation showed a coarser grain than the seed bank, probably in relation to seed clumping.  相似文献   

11.
Gaps in grassland created by animals are often sites for species regeneration. The persistent seed banks of ant-hills and surrounding soils in a calcareous grassland in southern Britain were compared and analysed in terms of seed mass and longevity. The relative abundance of species on ant-hills compared to the pasture was highly correlated with seed abundance in ant-hill soil. The abundance of plant species on ant-hills compared to the pasture was significantly negatively correlated with seed mass, and positively correlated with seed longevity. These results suggest that germination from the seed bank in ant-hill soils, as well as limited seed dispersal and vegetative invasion, contributes to the distinctive ant-hill vegetation. The same may apply to other gaps created by animals in grasslands.  相似文献   

12.
啮齿动物和鸟类对东灵山地区辽东栎种子丢失的影响   总被引:12,自引:4,他引:12  
20 0 0年 8月中旬至 10月上旬 ,在北京东灵山地区小龙门林场选取两块辽东栎分布近似而坡向不同的样地 ,并对样地内种子库与啮齿动物的种群数量变化进行了调查。结果表明 ,两块样地种子雨持续 4 0天左右 ,且种子下落趋势基本一致 ,高峰期都集中在 9月中旬 ,不同坡向的种子产量差异显著。在两样地随机各设置 2 4个种子方形收集器 (0 5m2 )和 2 0个地表样方 (1 0× 0 5m2 )调查种子产量。通过比较收集器内壳斗和种子数量 ,发现二者无显著差异 ,说明鸟类对林冠层种子丢失作用不明显 ;而收集器和地表样方种子数量差异显著 ,表明辽东栎种子库扩散主要由林中啮齿动物完成。标记重捕发现辽东栎林中啮齿动物群落包括大林姬鼠 ,社鼠 ,棕背鼠平和花鼠 ,其中大林姬鼠为优势种 ,占群落的 77.2 %。  相似文献   

13.
Large seed banks have been found in tropical dry forests and also in habitats with high seasonality in rainfall. However, patchily structured vegetation could induce great spatial variation in the seed bank. We characterized the seed bank in a patchy vegetation of restinga, a common type of coastal vegetation found in the Atlantic forest biome. We also evaluated whether there is any spatial variation between the litter and soil layer, bare sand, and the edge and center of vegetation patches with distinct species dominance. We found 104 seeds/m2 in the seed bank using a 5‐cm‐depth sampling. Seven out of 16 species found in the restinga seed bank germinated; two of these were found in the early stages of vegetation patches. We found a higher number of seeds at the edge than in the center of vegetation patches. However, there were no significant differences in the number of seeds in the seed bank between the litter and soil layer, and between vegetation patches with distinct species dominance. Bare sandy soils had lower seed bank densities than vegetation patches. A small seed bank size might be explained by the low proportion of seeds from herbaceous and woody species, which are pioneers in the Atlantic forest. However, seed bank might play an important role in the early stages of the successional process, due to the occurrence of the few species that are able to colonize new young vegetation patches.  相似文献   

14.
Cistus species are obligate seeding, early colonizers that follow disturbance, particularly fire, in Mediterranean ecosystems. We studied seed release, seed dispersal and soil seed populations in stands of Cistus ladanifer and C. libanotis. Seed release started in mid- to late summer (C. ladanifer) or in early autumn (C libanotis), and continued for a very extended period: 8-10 months in C. ladanifer, and for a mean of 16 months in C. libanotis. The xerochastic capsules of both species released seeds by successive dehiscence of the locules. All capsules begin to dehisce simultaneously at the start of the seed release period, but in C. libanotis capsule fragmentation replaced dehiscence early in the seed release period. In plants of both species, seed shadows were characterized by a peak of density beneath the plant canopy and a very short tail of much lower densities, indicating that seeds are concentrated beneath mother plants when dispersed. Nevertheless, in late May, at the onset of the fire season, soil seed densities beneath plant canopies were low compared with densities expected from seed shadows, but were apparently high enough to allow recovery of the stands if a disturbance, such as fire, had taken place. Seed-eating Bruchidae in summer and granivorous ants during the seed release period were apparently the main causes of seed losses. Results suggest that in both Cistus species, the staggered seed release could constitute an efficient risk-reducing trait. The plant pool of seeds existing throughout most of the year could be a relevant component of Cistus seed banks.  相似文献   

15.
16.
To clarify the factors affecting the seedling establishment of the subalpine stone pine (Pinus pumila Regl.) from nutcracker-cached seeds, subsequently emerged seedlings were examined in two plots on Mt Akitakomagadake, northern Japan. The survivorship of older seedlings (2–20years old) was also monitored during six seasons at nine different sites. In one plot with 18 caches, seed germination occurred between June and mid-July. During this period, nutcrackers retrieved the stored pine seeds from 16 caches and ate some seeds immediately. Simultaneously, this nutcracker behavior caused mechanical damage to newly emerging seedlings (e.g. uprooting and tearing off cotyledons). Such initial loss to in situ harvesting and mechanical damage accounted for 75% of the total seeds remaining in the caches. The number of established current seedlings sharply declined during the first 2years, and the survival rate was 4.4% over four winters. Two major mortality factors were identified: uprooting by frost-heave soil disturbance in the spring of the second year and standing death by drought or other physiological stresses in early summer. In another plot with 13 caches, survivorship of newly emerged seedlings was also low (4.2%), but mortality was mostly due to summer drought, indicating that the frost-heave event was a site-specific disturbance factor. For older seedlings, survival rates reached approximately 90% even after six seasons and summer drought stress was a major mortality factor. My findings suggest that seedling recruitment of P.pumila was largely limited by both nutcracker disturbance and external disturbance (and/or stresses) at an early stage. However, after the critical first few years, pine seedlings were highly likely to survive and grow to the sapling stage despite the harsh environment of the high mountains.  相似文献   

17.
To clarify responses of plant and soil carbon (C) and nitrogen (N) pools in grassland ecosystem to N addition, a field experiment was performed in a grassland in Keerqin Sandy Lands, Northeast China. We investigated vegetation composition and C and N pools of plant and soil (0–30 cm) after five consecutive years of N addition at a rate of 20 g N m?2 y?1. Vegetation composition and species diversity responded dramatically to N addition, as dominance by C4 perennials was replaced with C3 annuals. Carbon in aboveground pool increased significantly (over two-fold), mainly due to the increase of the C in aboveground living plants and surface litter, which increased by 98 and 134%, respectively. Although soil C did not change significantly, the root C pool decreased in response to 5 years of N addition. The total ecosystem C pool was not significantly impacted by N addition because the large soil pool did not respond to N addition, and the increase in aboveground C was offset by the decrease in root C pool. Moreover, N addition significantly increased the aboveground N pool, but had no significant effects on belowground and total ecosystem N pools. Our results suggest that in the mid-term N addition alters the C and N partitioning in above- and belowground pools, but has no significant effects on total ecosystem C and N pools in these N-limited grasslands.  相似文献   

18.
19.
Cai L  Liu XL  He F  Fan H  Pan HL  Pan YZ 《应用生态学报》2011,22(11):2822-2828
采用野外调查方法,研究卧龙巴郎山高山及亚高山草甸不同海拔梯度下花卉植物生物量的变化格局,并进行土壤因子分析,结果表明:花卉植物地上生物量随海拔的升高呈单峰曲线变化,在3500 m处达到峰值,花-果、茎、叶生物量的变化趋势与地上生物量一致;地下生物量随海拔的升高呈U型曲线变化.随海拔的升高,土壤酸性增强,水解氮和全钾含量显著升高,土壤有机质、全氮和有效磷的含量显著降低,花卉植物地上生物量随土壤pH值及全氮、速效钾含量的升高显著增大;地下生物量随土壤有机质、有效磷含量的升高显著增大,随全钾、水解氮含量的升高显著减小.  相似文献   

20.
鸟类取食中国沙棘果实的方式及其对种子的传播作用   总被引:7,自引:1,他引:7  
2003年9月~2004年3月,定期观察取食中国沙棘果实的鸟类及其取食方式。共记录取食中国沙棘果实的鸟类18种,其取食果实的方式主要有:1)直接在树冠上吞食果实,有时候在吞食后将种子呕出;2)将果实从树上衔走后,在栖息处吞食或啄食;3)将果实啄落至地面,然后取食果肉和种子,留下果皮;4)啄破果皮,吸食果肉,留下果皮及种子;5)从顶端将果皮啄破后,仅取食里面的种子。不同的取食方式决定了它们对沙棘种子的传播作用不同。收集鸟粪便中的种子与完整的干果实及人工剥离果肉和内果皮的种子做萌发对比实验,结果表明,鸟类消化道过程对种子的萌发有一定影响,但萌发率仍较高。沙棘为多种鸟类提供食物,而鸟类则为沙棘传播种子,它们之间形成一种互利关系。  相似文献   

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