Long‐term seed bank dynamics in a temperate forest under conversion from coppice‐with‐standards to high forest management

Questions: How do changes in forest management, i.e. in disturbance type and frequency, influence species diversity, abundance and composition of the seed bank? How does the relationship between seed bank and vegetation change? What are the implications for seed bank dynamics? Location: An ancient Quercus petraea — Carpinus betulus forest in conversion from coppice‐with‐standards to regular Quercus high forest near Montargis, France. Methods: Seed bank and vegetation were sampled in six replicated stand types, forming a chronosequence along the conversion pathway. The stand types represented mid‐successional stages of stands in transition from coppice‐with‐standards (to high forest (16 plots) and early‐ and mid‐successional high forest stands (32 plots). Results: Seed bank density and species richness decreased with time since last disturbance. Adjusting for seed density effects obscured species richness differences between stand types, but species of later seres were nested subsets of earlier seres, implying concomitant shifts in species richness and composition with time since disturbance. Later seres were characterized by species with low seed weight and high seed longevity. Seed banks of early seres were more similar to vegetation than to later seres. Conclusions: Abandonment of the coppice‐with‐standards regime altered the seed bank characteristics, as well as its relationship with vegetation. Longer management cycles under high forest yield impoverished seed banks. For their persistence, seed bank species will increasingly rely on management of permanently open areas in the forest landscape. Thus, revegetation at the beginning of new high‐forest cycles may increasingly depend on inflow from seed sources.     

Relationships among the seed rain,seed bank and vegetation of a Hawaiian forest

Abstract. Hawaiian ecosystems are prone to invasion by alien plant species. I compared the seed rain, seed bank, and vegetation of a native Hawaiian forest to examine the potential role that seed ecology plays in allowing alien species to invade native forest. Absolute cover of seed plants in the forest was 126 %, annual seed rain was 5 713 seeds m^-2 yr^-1, and the mean density of seedlings emerging from the seed bank averaged across four seasons was 1 020/m². The endemic tree Metrosideros polymorpha was the most abundant species in the vegetation, seed rain and winter seed bank. Overall, native seed plants comprised 95 % of the relative cover in the vegetation and 99 % of the seeds in the seed rain, but alien species comprised 67 % of the seeds in the seed bank. Alien species tended to form persistent seed banks while native species formed transient or pseudo-persistent seed banks. Dominance of the seed bank by alien species with persistent seed banks suggests that aliens are favorably placed to increase in abundance in the vegetation if the forest is disturbed.     

Soil seed bank composition along a forest chronosequence in seasonally moist tropical forest,Panama

Abstract. We used a forest chronosequence at the Barro Colorado Nature Monument (BCNM) to examine changes in the abundance and species composition of seeds in the soil during forest succession. At each of eight sites varying from 20 yr to 100 yr since abandonment, and at two old-growth (> 500 yr) forest stands, we established two 160-m transects and sampled the surface 0–3 cm of soil in cores collected at each 5 m interval. Seed densities were estimated from the number of seedlings germinated from the soil over a six-week period. Contrary to expectation, neither the density of the soil seed bank, nor species richness or diversity were directly related to age since abandonment, but the density of the soil seed bank was correlated with the abundance of seed-bank-forming species in the standing vegetation. In marked contrast to published studies, herbaceous taxa were rare even in the youngest stands, and the common tree species, which accounted for most seeds in the soil, were present in all stands. The pioneer tree Miconia argentea (Melastomataceae) was the single most common species in the seed bank, accounting for 62% of seeds and present in 92% of soil samples. Rapid recovery of the vegetation of young regrowth stands on BCNM, when compared to sites elsewhere may be partly due to allochthonous seed rain from nearby mature forest stands and the lack of seed inputs of weeds and grasses from agricultural and pasture lands which may inhibit forest succession.     

Variation in soil seed bank species composition of a dry coniferous forest: spatial scale and sampling considerations

In order to assess the effects of disturbance on soil seed bank spatial structure, variation in seed bank species composition was analyzed at two spatial scales in mature (undisturbed) and recently disturbed stands of Interior Douglas-fir forest in south-central British Columbia. Coarse-scale analysis among stands 10–100 km apart using Multi-Response Permutation Procedures showed that individual mature stands were mainly characterized by unique seed bank species compositions. Disturbance had an homogenizing effect on seed bank species composition at the coarse scale––there was less variability among stands following disturbance by both low and high severity fires, and by non-salvage logging. In contrast, finer scale analysis among sampling units c. 10 m apart showed that heterogeneity in seed bank species composition was greater on severely burned and logged sites, commensurate with greater levels of soil disturbance, than on lightly burned and undisturbed sites. Despite the high intensity of seed bank sampling (sixty 25 cm² soil samples from each of 16 sites), species-area curves leveled off only when infrequent species were removed from the dataset. The number of seed bank samples required to account for the common species ranged from 84 on severely burned sites, to 196 on undisturbed sites; more than the 240 samples collected per disturbance class in this study would have been required to account for the remaining infrequent species. Overall, this study highlights the importance of sampling intensively within multiple stands to capture the variation in species composition inherent to these dry coniferous forest soil seed banks.     

Long-Term Effects of Forest Regrowth and Selective Logging on the Seed Bank of Tropical Forests in NE Costa Rica1.

To investigate long-term effects of land use on the soil seed bank, we compared the abundance/density, species richness, life form distribution, and species composition of seeds stored in the soil of four 15–20 yr-old second-growth stands, two old-growth stands, and two previously selectively-logged stands in the Caribbean lowlands of Costa Rica. Surface soil (10 cm deep, 4.7 cm diameter) was collected at 10 m intervals along three 120–160 m long transects in each stand (44–48 soil cores, 22–24 combined seed bank samples per site). Seed density was highest but variable in second-growth stands (8331–14535 seeds/m²), low and homogeneous in old-growth stands (2258–2659 seeds/m²), and intermediate and highly variable in selectively-logged stands (1165–6854 seeds/m²), which also had contrasting logging intensities. Species richness was strongly dependent on seed density, but showed less variation. Life form distribution did not differ statistically among or within land-use categories. In each stand, herbs-forbs, shrubs, and vines dominated the seed bank (> 75% of the species richness and abundance), whereas trees were a minor component (< 20% of the species richness and < 5% of the abundance) and were predominandy early successional. Shrubs and vines were most abundant in second-growth stands where regrowth vegetation was repeatedly cut before abandonment, whereas grasses and sedges were most abundant in the only forest stand that was completely surrounded by pastures. In terms of species composition, old-growth stands were more similar to selectively-logged stands than to second-growth stands, but across stands, selectively-logged forests were most distinct from the other two forest types. An inventory of the standing woody vegetation in each site showed little representation of the woody taxa found in the seed bank. We discuss these results in the context of the main factors that have been postulated to influence the abundance, life form, and species composition of tropical forest seed banks, and explore the role of the latter during intermediate phases of tropical forest succession and regeneration.     

Role of soil seed bank along a disturbance gradient in an alpine meadow on the Tibet plateau

We examined the role of the soil seed bank along a grazing disturbance gradient and its relationship with the vegetation of alpine meadows on the Tibet plateau, and discussed the implications for restoration. The seed bank had a high potential for restoration of species-rich vegetation; 62 species were identified in the vegetation and 87 in the seed bank, 39 species being common to both. Mean seed density was 3069–6105 viable seeds m⁻². The density of buried seeds increased significantly with increasing disturbance, indicating that restoration of disturbed areas is not seed limited. Seed density and species richness decreased with depth. The proportion of perennial species decreased with decrease in disturbance both in seed bank and in vegetation. A large portion of species with persistent seeds in the disturbed areas indicate that this seed type can be regarded a strategy of adaptation to current disturbances. Detrended correspondence analysis (DCA) showed significant differences of species composition between seed bank and vegetation, except for the seriously disturbed site. Our results suggest that the establishment of new species in severely disturbed areas is more dependent on the seed bank. By contrast, the restoration in less-disturbed and mature meadows does not rely on seed banks, and the establishment of the vegetation in these communities is more likely to rely on seed dispersal from the standing vegetation and on species with vegetative reproduction.     

Disturbance of suburban Fagus forests by recreational activities: Effects on soil characteristics,above‐ground vegetation and seed bank

Questions: How does recreational disturbance (human trampling) affect soil characteristics, the performance of the understorey vegetation, and the density and species composition of the soil seed bank in Fagus sylvatica forests? Location: Suburban forests near Basel, northwestern Switzerland. Methods: We compared various soil characteristics and the performance of the understorey vegetation in six beech forest areas frequently disturbed by recreational activities with those in six undisturbed control areas, in spring 2003. In the same forest areas, the soil seed bank was investigated using the seedling emergence method. Samples were obtained from soil cores in January 2003. Results: We found substantial changes in soil compaction, above‐ground vegetation and in the soil seed bank due to recreational activities. In frequently visited areas, soil compaction was enhanced which caused a decrease in cover, height and species richness of both herb and shrub layers. Compared with control areas, the number of trampling‐tolerant species of the seed bank was significantly higher in disturbed areas, and total species richness tended to be higher in disturbed than in control areas. Furthermore, the similarity in species composition between the above‐ground vegetation and seed bank was significant lower in disturbed than in control areas. Conclusions: The intensive use of suburban forests for recreational activities, mainly picnicking, affects the vegetation of natural beech forests. Our study indicates that a restoration of degraded forest areas from the soil seed bank would result in a substantial change of the vegetation composition.     

Seed survival of the tropical tree Cryptocarya aschersoniana (Lauraceae): Consequences of habitat disturbance

Seed survival in soil could be strongly influenced by habitat characteristics, but little is known about the behaviour of seeds sensitive to desiccation in seed banks installed in natural or disturbed habitats. Cryptocarya aschersoniana seeds disperse at the end of the rainy season but do not germinate immediately; thus, they may form seed banks in soil. This study evaluated the behaviour of C. aschersoniana seed banks induced in the natural environment of the species and in a disturbed area. Recently harvested C. aschersoniana germination units were characterized according to their water content, germination and viability. In 2011 and 2012, seed banks were established by burying samples of seeds in the understory of a semi‐deciduous forest. In 2012, samples were also buried in a disturbed area. The seed banks were sampled at certain time intervals, and the samples were characterized as described above. Precipitation and air temperature data were collected. As a result, seeds in the seed bank established in the natural environment form a transient seed bank and showed the same behaviour in both years studied. A germination peak was observed starting 210 days after burial (coinciding with the onset of the rainy season) and reached germination percentages higher than 80% at the end of the experiment for both years. Seed mortality did not exceeded 28% in the natural environment. However, in the disturbed environment, the seeds lost their viability more rapidly, with 90% of the seeds becoming unviable 240 days after burial. Germinated seeds in the disturbed environment (maximum 21%) were not able to establish seedlings. These results underscore the importance of maintaining a natural, undisturbed forest for the conservation of this species.     

Causes of arrested succession in coastal dune forest

Dispersal or recruitment limitation may arrest succession after disturbance. In north-eastern South Africa the Acacia karroo successional pathway is used to facilitate coastal forest recovery after strip-mining. However, although A. karroo establishes naturally, it forms monospecific stands, arresting forest succession for decades. This casts doubt on the efficacy of this restoration pathway. We investigated the causes of arrested succession. The seed and seedling banks of A. karroo stands and of forest at Cape Vidal, and three A. karroo stands (7–27 years old) on rehabilitated strip-mined dunes at nearby Richards Bay were examined. The establishment and growth of seedlings at Cape Vidal were also considered. The seed bank was larger and more diverse in forest, but the seedling bank was larger in Acacia stands. At Richards Bay, the size of the seed bank increased and the seedling bank decreased with Acacia stand age. Excluding mammalian herbivores in Acacia stands at Cape Vidal resulted in greater species richness and survival of naturally established seedlings, as well as two experimentally planted species. Neither seed dispersal nor seedling establishment limited recruitment of tree species in Acacia stands. Herbivory arrested forest succession by causing the differential mortality of seedlings. In contrast, at Richards Bay where there were few mammalian herbivores, the advanced regeneration in A. karroo stands converged on the diversity of nearby forests 29 years after restoration. Controlling herbivore access and seeding Acacia stands with forest species are site-specific options for preventing arrested succession when using the A. karroo successional pathway.     

A comparison of seed banks across a sand dune successional gradient at Lake Michigan dunes (Indiana,USA)

In habitats where disturbance is frequent, seed banks are important for the regeneration of vegetation. Sand dune systems are dynamic habitats in which sand movement provides intermittent disturbance. As succession proceeds from bare sand to forest, the disturbance decreases. At Indiana Dunes National Lakeshore, we examined the seed banks of three habitat types across a successional gradient: foredunes, secondary dunes, and oak savanna. There were differences among the types of species that germinated from each of the habitats. The mean seed bank density increased across the successional gradient by habitat, from 376 to 433 to 968 seeds m⁻², but with foredune and secondary dune seed bank densities being significantly lower than the savanna seed bank density. The number of seeds germinated was significantly correlated with soil organic carbon, demonstrating for this primary successional sequence that seed density increases with stage and age. The seed bank had much lower species richness than that of the aboveground vegetation across all habitats. Among sites within a habitat type, the similarity of species germinated from the seed banks was very low, illustrating the variability of the seed bank even in similar habitat types. These results suggest that restoration of these habitats cannot rely on seed banks alone.     

Açaí palm management disturbs seed rain and soil seed bank of an Amazonian estuarine forest

The exploitation of non-timber forest products has been proposed as a sustainable way to exploit tropical forests, but such an opportunity remains to be proved. Here, we examine the impact of intensive açaí palm (Euterpe oleracea) management on the seed rain and soil seed bank in an estuarine forest landscape with a long history of forest management by locals in the Amazon region. Seed rain (100 80 cm² collectors) and soil seed bank (100 30 cm² samples) were monitored through a year across 20 forest stands, covering a gradient of açaí stem density (50–3575 açaí stems per ha). Seed rain and bank were dominated by açaí seeds (85.5%–85.8%) and by excluding them, seed rain and bank were low density and species poor, capturing a tiny subset from the local (17.91%–19.40%) and landscape woody flora (11.82%–14.55%). Moreover, autochthonous and vertebrated-dispersed predominated as well as those from tree species considered useful by locals. Overall, açaí stem density positively affected açaí seed abundance in the seed rain and negatively affected seed pools in the bank in relation to abundance of seeds and vertebrated dispersed, while adult tree species richness and density and accessibility to forest stands were associated with more diversified seed pools. Thereby, forest stands are exposed to different levels of açaí management (high vs. low intensity) supported taxonomically distinct seed pools. Our results suggest that açaí intensification disturbs seed rain and soil seed bank with potential impacts on forest regeneration and the forest integrity standards required to consider açaí fruit production as sustainable according to current legislation.     

Effects of disturbance intensity on seasonal dynamics of alpine meadow soil seed banks on the Tibetan Plateau

Background and Aims

Information on soil seed bank processes is crucial for understanding vegetation dynamics. Despite the documented importance of soil seed banks in many ecosystems, their role is not fully understood in some sensitive habitats, such as the alpine meadows of the Tibetan Plateau.

Methods

We studied the seasonal dynamics of the germinable soil seed bank under four disturbance intensities in an alpine meadow on the Tibetan Plateau as well as seed size distribution relative to disturbance intensity. Composition of the seed bank was compared with that of the standing vegetation.

Results

Density of buried seeds increased with disturbance intensity, but species richness and species diversity decreased. Seed density and species richness of the seed bank varied seasonally in all layers (0–2, 2–7, 7–12 cm) and the whole (0–12 cm). The species composition of seed bank was not significantly influenced by season. There was no trend in seed size distribution as disturbance increased. Seasonal seed bank turnover rates increased with increase in disturbance. The result of the NMDS showed that species composition of seed bank and vegetation exhibited a fairly uniform pattern in each season.

Conclusions

Although as a whole the species composition of the vegetation and seed bank showed a relatively low degree of similarity in each season, similarity was highest in the most disturbed habitat. There was no alteration in species composition of seed bank regardless of disturbance intensity, but seed density decreased as disturbance increased. Disturbances in alpine plant communities might increase persistence of regeneration niches. Regeneration from the seed bank together with vegetative reproduction contributed to aboveground vegetation in highly disturbed habitats. Clonal species played an important role in regeneration of vegetation in slightly disturbed areas, where there was little contribution of ruderals from soil seed banks.     

Soil seed banks in different environments: initial forest,mature forest,Pinus and Eucalyptus abandoned stands

Abstract

Different environments (initial forest, mature forest, Pinus and Eucalyptus stands) found in Seasonal Semideciduous Forest fragments affect the density of viable seeds, as well as the floristic similarity, diversity, and richness of tree species in soil seed banks. This hypothesis was tested in the current study. Soil seed bank samples were collected in the aforementioned environments during rainy and dry seasons, and taken to a shade house, where they remained under favorable seed germination conditions. Tree seedling emergence was measured, and sample species were identified every 15?days, for six months, in each sampling period. In total, 97 individuals m^?2 and 23 species emerged in all environments and periods. The highest density of viable seeds of tree species in the soil seed bank was found in the initial forest stretch, mature forest stretch and abandoned Eucalyptus stand. Only the Pinus stand seed bank in the dry season had different floristic and lower viable seed density than the mature forest seed bank. Thus, all environments, except the abandoned Pinus stand, can preserved Seasonal Semideciduous Forest fragments.     

Soil seed bank dynamics of fire-prone wooded grassland, woodland and dry forest ecosystems in Ethiopia

In order to reveal the role of soil seed banks in vegetation recovery after fire in savanna, the spatial distribution and temporal changes in the soil seed banks of regularly burning savanna in Gambella, western Ethiopia, was studied. The seedling emergence technique was employed to determine the species composition and density of the soil seed bank of six sites ranging in fire severity from wooded grassland with frequent fires over woodland with intermediate fire frequency to forest with absence of fires. Species composition and density of seeds in the soil were compared between seasons, depths and sites with different types of standing vegetation. Fourteen plant species were recorded in the soil seed bank from the grassland and woodland sites and 6 from the dry forests; 60 % of the taxa in the soil seed bank were annuals and 40 % were perennials. The soil seed banks were largely dominated by graminoids and 48–97 % of the soil seed bank in the grasslands and woodlands was of a single grass species, Hyparrhenia confinis , which was absent from the dry forests. The soil seed pools ranged from less than 100 to 4700 seeds per m² depending upon the season. The soil seed bank of graminoids was nearly empty after the onset of the rainy season whereas seeds of broadleaved herbs and woody species able to germinate were still found after this time. Floristic composition, representation of life forms and density of seeds in soil did not correspond closely with that of the standing vegetation, but within graminoids there was a strong similarity between the soil seed bank and the standing vegetation. The current fire regime of Ethiopian savanna woodlands appears to maintain the dominance of graminoids over broadleaved herbs and woody plants both as seeds in the soil and in the standing vegetation.     

Geringe Samenbank von beweidbaren Arten für die Etablierung von Waldweiden im Schweizer Mittelland

Kipfer T. and Bosshard A. 2007. Low seed bank of herb species suitable for grazing hampers the establishment of wood pastures in the Swiss lowlands. Bot. Helv. 117: 159 – 167. Controlled forest grazing is expected to yield benefits for biodiversity conservation, landscape quality, and in some cases also for land use economy. In the Swiss lowlands, first attempts are being made to reintroduce forest grazing in productive beech forests, but methodic experience is still limited. One main issue concerns the development of the vegetation after forest stands have been thinned to improve light conditions: Will grassland vegetation establish spontaneously? The present study analyses the composition of the soil seed bank of four beech forest stands. The seed bank density ranged from 1’244 to 28’651 seeds m⁻². Seed banks mainly consisted of forest and ruderal species; most abundant were Juncus effusus, Carex sylvatica, Rubus spp. and Clematis vitalba. Seeds of grassland plants were restricted to a few species, and their abundance in the seed bank decreased rapidly with increasing distance from the forest edge. These results reveal that there is little potential for grasslands to develop spontaneously from the seed bank. The introduction of grassland species of local origin using the green hay method is therefore recommended to prevent soil degradation during the first years of grazing, to fulfil minimal biodiversity requirements and to lower the risk of an establishment of neophytes and other problematic plant species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Manuskript angenommen am 2. September 2007     

The role of the soil seed bank in vegetation recovery on an oceanic island severely damaged by introduced goats

Question: Are the seed banks of an isolated subtropical oceanic island capable of naturally regenerating vegetation either with species of the historical forest community or with the existing grassland community after severe damage to the vegetation by goats? Location: Nakoudojima Island, Bonin Archipelago (Ogasawara Shoto), Japan. Methods: Soil samples were collected at 0–5 cm and 5–10 cm depths from seven plots in forests, grasslands, artificially matted areas and bare land. Soil seed banks were assessed using the seedling emergence method followed by the hand‐sorting of ungerminated seeds. We determined the size and composition of the seed banks in upper soil layers of plots and compared the seed banks to the standing vegetation. Results: A total of 12 220 seedlings belonging to 42 species from 20 families germinated. Total mean seed density (0–5 cm depth) was low in all plots within forest, grassland, and heavily degraded vegetation types (34.7 ± 8.6 to 693.5 ± 123.6, 58.6 ± 7.8 to 107.1 ± 10.0, and 1.1 ± 0.5 to 7.2 ± 2.3 seeds/m², respectively). Forbs and graminoids dominated the seed banks of grassland and forest plots including Cyperus brevifolius, Gnaphalium pensylvanicum, Oxalis corniculata and Solanum nigrum, and these alien species comprised 90% of the density of the seed bank. There was little correlation between seed banks and standing vegetation of the island (Sørensen similarity coefficient values 0.26 to 0.45). Conclusions: If natural regeneration occurs from the seed bank of the island, future vegetation will not move toward the original forest community, because the seed bank is dominated by non‐native herbaceous grassland species. Though isolated, a few forest remnants with low species richness could be an important source for the natural re‐establishment of forest on the island; however, seed availability may be limited by either poor dispersal or pollination so that woody species will probably recover very slowly on this goat‐impacted island.     

The relationship between soil seed bank,above‐ground vegetation and disturbance intensity on old‐field successional permanent plots

Questions: How does disturbance and successional age influence richness, size and composition of the soil seed bank? What is the potential contribution of the soil seed bank to the plant community composition on sites differing in their successional age or disturbance intensity? Location: Experimental Botanical Garden of Göttingen University, central Germany. Methods: Above‐ground vegetation and soil seed bank were studied on formerly arable fields in a 36‐year‐old permanent plot study with five disturbance intensities, ranging from yearly ploughing via mowing to long‐term uninterrupted succession. We compared species compositions, seed densities and functional features of the seed bank and above‐ground vegetation by using several methods in parallel. Results: The seed bank was mainly composed of early successional species typical of strongly disturbed habitats. The difference between seed bank composition and above‐ground vegetation decreased with increasing disturbance intensity. The species of greatest quantitative importance in the seed bank was the non‐native forb Solidago canadensis. Conclusions: The ability of a plant community to regenerate from the soil seed bank dramatically decreases with increasing time since abandonment (successional age) and with decreasing disturbance intensity. The present study underlines that plant species typical of grasslands and woodlands are limited by dispersal capacity, owing to low capacity for accumulation of seeds in the soil and the fact that most species do not build up persistent seed banks. Rare and target species were almost absent from the seed bank and will, after local elimination, depend on reintroduction for continuation of their presence.     

Buried germinative seeds in mature beech forests with different herbaceous vegetation and soil types

The seed banks in the soils of seven mature beech forests in southern Sweden were examined using the seedling-emergence method. Seedling emergence in the field was also studied. In the studied forests, covering a wide range of vegetation and soil types, between 1020 and 4500 germinating seeds m⁻² were found in the seed bank. Seed abundance showed no apparent relationship with the type of soil or vegetation at the sites, but the highest number of species in the seed bank was found on the mull sites. The species diversity of germinative seeds increased strongly with increasing soil fertility.
Only a minor part (10–35%) of the species in the germinable part of the seed bank were represented in the vegetation. Soil samples from the oligotrophic sites mainly contained graminoids, notably Carex spp., while herbs dominated the seed banks of the rich mull sites. Seeds of e.g. Stellaria nemorum, Oxalis acetosella, Moehringia trinervia, Viola rivinianalreichenbachiana, Melica uniflora , and Milium effusum were especially abundant in the mull soils. Woody species were infrequent on all sites, and no representatives of the early spring flora were noted in the germination tests.
In the mor and moder soils most seeds were recovered from the mineral soil, and they were believed to originate from early stages in the succession of the forest. Several sites had comparatively large seed banks of species that typically occur in disturbed forests, e.g. Juncus effusus and Rubus idaeus , but very few germinating seeds belonged to species restricted to non-forest habitats. Emerging seedlings in the field were only observed on the mull and moder sites. With few exceptions they belonged to species, which were common both in the seed banks and in the vegetation.     

Soil seed bank in different vegetation types in the Loess Plateau region and its role in vegetation restoration

In the Loess Plateau region, soil erosion is a serious problem. Vegetation restoration is an effective approach to control soil erosion and improve ecosystems. The soil seed bank generally plays an important role in vegetation restoration after disturbance. Thus, we reviewed soil seed bank studies to reveal the soil seed bank characteristics and its role in vegetation restoration in three vegetation types (forest, forest‐steppe, and steppe). We selected 38 seed bank studies and analyzed several seed bank characteristics, such as seed density, species composition, and the relationship between seed size and seed bank. We also assessed the role of the soil seed bank in vegetation restoration. The soil seed bank density ranged from 2,331 ± 1,993 to 6,985 ± 4,047 seeds/m² among the different vegetation types. In the soil seed bank, perennial herbs and grasses accounted for 51.5% of the total species. Native species that were dominant or common in the standing vegetation usually had relatively high seed bank densities. Moreover, species with smaller seeds generally had higher soil seed bank densities. The present study indicates that the soil seed bank plays a significant role in spontaneous vegetation restoration, especially during the early successional stages in abandoned slope farmlands and grazing‐excluded grasslands. However, species with large seeds or transient soil seed banks should be reintroduced through seeding to accelerate target species restoration. More studies on soil seed banks need to be conducted to comprehensively reveal their characteristics.     

西双版纳热带森林土壤种子库与地上植被的关系

通过实验研究探讨了西双版纳几类热带森林的土壤种子库与地上植被的关系．结果表明,在森林演替的初期,土壤种子库与地上植被共有的种类和种子储量较多,随着林龄的增大,外来种子的比例逐渐增加,到季节雨林阶段,土壤种子库中的种子大部分为来自群落外的先锋种类．这些种子在郁闭的林冠下很难萌发,一旦森林受到干扰出现林窗或空旷地,这些潜在的种源将迅速萌发,参与植被的恢复或演替