Management effects on the vegetation and soil seed bank of calcareous grasslands: An 11-year experiment

Calcareous grasslands, most of which are man made and therefore depend on some kind of human interference for their maintenance, are among the most species-rich communities on Earth at a small scale. For many centuries, most of these grasslands have been used as extensive pasture. However, after 1900, and particularly from 1940 onwards, livestock grazing has declined throughout Europe leading to the abandonment of low intensity grasslands over large areas. To conserve the remaining grasslands or to restore recently abandoned grasslands, better insights about the effects of grassland management on above and belowground species diversity are needed. Here, we describe the results of an 11-year experiment to investigate the role of grassland management (grazing, mowing and abandonment) in determining species composition and diversity both in the aboveground vegetation and the seed bank of a calcareous grassland in Belgium. Species diversity declined by about 60% 11 years after abandonment, from 29 species m⁻² to as few as 12 species m⁻². Plots that were grazed remained constant in species richness, whereas mown sites lost about 20% of their original species. Abandoned plots were largely dominated by a few grass species, in particular Festuca rubra. Concomitant with changes in the aboveground vegetation, both the number of species found in the seed bank and seed density (number of seeds m⁻²) had changed significantly 11 years after abandonment. Species diversity and seed density were significantly lower in abandoned plots than in grazed or mown plots. We conclude that abandonment of calcareous grasslands may lead to rapid decline of plant species diversity both in the aboveground vegetation and in the seed bank. As a result, seed banks probably have a limited role to play in the restoration of recently abandoned grasslands.     

Seed germination and seedling survival of two threatened endemic species of the northwest Iberian peninsula

We examined germination and seedling survival of Petrocoptis grandiflora and Petrocoptis viscosa (Caryophyllaceae), two narrow endemic species from the northwest Iberian Peninsula. The experiments were carried out with seeds of three of eight populations of P. grandiflora and one of the three sole populations of P. viscosa. Under natural conditions, both P. grandiflora and P. viscosa produce very large numbers of seeds. However, the specific microhabitat of these species (cracks and crevices of limestone rockfaces) has very marked effects on seed germination, and subsequent seedling survival. In the present study, we examined the effects of light, cold treatment and seed weight on germination capacity. In the case of P. grandiflora, we also compared the germination of seeds of the different populations. In addition, we assessed seedling survival over a 1-year period. Seeds maintained in darkness showed higher germination percentages than seeds maintained with a 12:12 h photoperiod. The application of a short period of cold prior to germination had no significant effect in either species. In the case of P. grandiflora, population of origin had a significant effect on germination percentage. Of all the factors considered, seed weight was the most important source of variability, both in seed germination and subsequent seedling survival. In both species in the natural habitat, less than 10% of germinated seeds survived by the end of the year. Seedling survival was affected by microhabitat. Seedlings in non-rockface soil microhabitats were more likely to suffer herbivory or interspecific competition than seedlings in crevices in the rockface.     

Limiting factors in the restoration of UK grassland beetle assemblages

Grasslands restoration is a key management tool contributing to the long-term maintenance of insect populations, providing functional connectivity and mitigating against extinction debt across landscapes. As knowledge of grassland insect communities is limited, the lag between the initiation of restoration and the ability of these new habitats to contribute to such processes is unclear. Using ten data sets, ranging from 3 to 14 years, we investigate the lag between restoration and the establishment of phytophagous beetle assemblages typical of species rich grasslands. We used traits and ecological characteristics to determine factors limiting beetle colonisation, and also considered how food-web structure changed during restoration. For sites where seed addition of host-plants occurred the success in replicating beetle assemblages increased over time following a negative exponential function. Extrapolation beyond the existing data set tentatively suggested that success would plateau after 20 years, representing a c. 60% increase in assemblage similarity to target grasslands. In the absence of seed addition, similarity to the target grasslands showed no increase over time. Where seed addition was used the connectance of plant–herbivore food webs decreased over time, approaching values typical of species rich grasslands after c. 7 years. This trend was, however, dependent on the inclusion of a single site containing data in excess of 6 years of restoration management. Beetles not capable of flight, those showing high degrees of host-plant specialisation and species feeding on nationally rare host plants take between 1 and 3 years longer to colonise. Successful grassland restoration is underpinned by the establishment of host-plants, although individual species traits compound the effects of poor host-plant establishment to slow colonisation. The use of pro-active grassland restoration to mitigate against future environmental change should account for lag periods in excess of 10 years if the value of these habitats is to be fully realised.     

坝上草原退耕地植被不同恢复处理土壤种子库研究

采用野外调查取样和室内实验相结合的方法,研究坝上草原退耕地土壤种子库的物种组成、密度和物种多样性等特征.结果表明:自然恢复、浅耕处理和深耕处理3种不同恢复措施下,土壤种子库物种丰富度(种)大小为浅耕处理(18)>自然恢复(15)>深耕处理(14);自然恢复处理、浅耕处理和深耕处理土壤种子库密度分别为23 949粒·m-2、15746粒·m-2和10600粒·m-2,浅耕处理和深耕处理分别比自然恢复处理减少34.3%和55.7%;不同恢复方式下土壤种子库与地上植被的物种密度的对应关系可用三次曲线来表示.土壤种子库间有较高的相似系数,但随着干扰程度的增加而减少.     

Seed banks in plant conservation: Case study of Santa Cruz tarplant restoration

Although conservation and restoration practitioners have focused on maximizing aboveground population size and seed set of rare plants, a clear understanding of seed bank dynamics is crucial to managing these species. Santa Cruz tarplant (Holocarpha macradenia) is a threatened annual forb restricted to coastal prairie habitats in central California. Holocarpha produces disk achenes germinating within a year of production and ray achenes forming a persistent seed bank. We constructed both deterministic and stochastic demographic models for a restored Holocarpha population, using demographic rates measured separately for unmanipulated plants and plants growing in plots where vegetation was clipped. The deterministic models indicated that regardless of germination from the seed bank, the population would decline without clipping or similar treatments that enhance survival and reproductive output. Deterministic models showed only a slight positive effect of increased ray seed germination rates on population growth, which would need to be balanced against a potential loss of buffering against environmental variation as the dormant seed bank was reduced. Our stochastic simulations suggested that extinction risk for Holocarpha populations would be minimized by intermediate levels of ray seed germination. Thus, managers should focus on improving the performance of aboveground plants before considering actions to stimulate germination, since the former will yield a greater increase in deterministic population growth and not sacrifice any buffering effect of the seed bank. This case study emphasizes the importance of considering dormant seeds and seed banks in designing successful restoration and management strategies for plant species at risk of extinction.     

Historical influences on the vegetation and soils of the Martha’s Vineyard, Massachusetts coastal sandplain: Implications for conservation and restoration

Both disturbance history and previous land use influence present-day vegetation and soils. These influences can have important implications for conservation of plant communities if former disturbance and land use change species abundances, increase colonization of nonnative plant species or if they alter soil characteristics in ways that make them less suitable for species of conservation interest. We compared the plant species composition, the proportion of native and nonnative plant species, and soil biogeochemical characteristics across seven dominant land use and vegetation cover types on the outwash sandplain of Martha’s Vineyard that differed in previous soil tillage, dominant overstory vegetation and history of recent prescribed fire. The outwash sandplain supports many native plant species adapted to dry, low nutrient conditions and maintenance of native species is a management concern. There was broad overlap in the plant species composition among pine (Pinus resinosa, P. strobus) plantations on untilled soils, pine plantations on formerly tilled soils, scrub oak (Quercus ilicifolia) shrublands, tree oak (Q. velutina, Q. alba) woodlands, burned tree oak woodlands, and sandplain grasslands. All of these land cover categories contained few nonnative species. In contrast, agricultural grasslands had high richness and cover of nonnative plants. Soil characteristics were also similar among all of the woodland, shrubland and grassland land cover categories, but soils in agricultural grasslands had higher pH, extractable Ca²⁺ and Mg²⁺ in mineral soils and higher rates of net nitrification. The similarity of soils and significant overlap in vegetation across pine plantations, scrub oak shrublands, oak woodlands and sandplain grasslands suggests that the history of land use, current vegetation and soil characteristics do not pose a major barrier to management strategies that would involve conversion among any of these vegetation types. The current presence of high cover of nonnative species and nutrient-enriched soils in agricultural grasslands, however, may pose a barrier to expansion of sandplain grasslands or shrublands on these former agricultural lands if native species are not able to outcompete nonnative species in these anthropogenically-enriched sites.     

新疆伊犁荒漠草原恢复措施下植物群落生态位特征分析

以禁牧2 年、休牧(每年5 月底至10 月初)、补播杂花苜蓿2 年3 种恢复措施及处于自由放牧状态下的荒漠草原退化草地为研究对象, 分析了伊犁荒漠草原植物群落的生态位特征。结果表明: 在对照、禁牧、休牧样地中, 建群种伊犁绢蒿(Seriphidium transiliense)生态位宽度值最大, 分别为1.037、1.101 和1.070, 在补播样地中针茅(Stipa sp.)的生态位宽度值最大, 为0.798。较高的生态位重叠发生在生态位宽度较大的物种之间,但最大的生态位重叠发生在生态位宽度较小的物种之间。在4 种样地中, 伊犁绢蒿-角果藜(Ceratoides arenarius)之间存在较高的生态位重叠和较大的生态位相似比例, 证明2 个种群之间在资源利用上存在激烈的种间竞争。     

The ant Lasius flavus alters the viable seed bank in pastures

The creation of small-scale vegetation mosaics by mound building is an important aspect of ant activity in grasslands. The consequences of this process for the composition of the viable soil seed bank are poorly understood. In this study we quantified the impact of the yellow ant Lasius flavus on both aboveground vegetation and seed bank of a low-intensity pasture located in the Vogelsberg area (Hesse, Germany). A few species of the mound vegetation (mainly therophytes) were restricted to the mounds, but most species also occurred in the surrounding area. The seed bank of ant mounds differed from that of the pasture soil between the mounds, with the abundance of germinating seeds being twice as high in the mounds. This was mainly due to the very large number of seeds originating from winter annuals and Thymus pulegioides. Seed abundance of most other species was lower in the mounds. Our results showed that this is partly due to dispersule weight limiting dispersal of seeds from the surrounding vegetation onto the mounds.     

Effects of experimental restoration on the diaspore bank of an upland moor degraded by Pteridium aquilinum invasion

We assessed the effects of a range of experimental restoration treatments on the diaspore bank (seed and spores) on an upland moor infested by dense Pteridium aquilinum, 9 years after implementation. Experimental treatment included both Pteridium control (cutting, spraying and combinations) and restoration treatments (grazing, seeding); both univariate and multivariate analyses of variance were used to assess significant effects. The seed bank was made up largely of Calluna vulgaris, Juncus effusus and Agrostis capillaris with the majority germinating from the litter (38 per cent) and upper soil layer (53 per cent). Soil depth influenced species composition and density, with greatest numbers near the surface, in keeping with a negative exponential response. In the lowest soil depth only ferns were abundant. A. capillaris seed density was greater in the most disturbed treatment (cut twice yearly with grazing), whereas C. vulgaris was greater in the low‐disturbance treatment (herbicide application only). The diaspore bank composition response identified that certain treatment combinations had a grass‐heath composition in the upper soil layer, which may assist future restoration. There was a significant effect of C. vulgaris seed addition detected in the Pteridium litter layer suggesting that this litter acted as a barrier to seed transfer to the soil. There was little evidence of coupling developing between the diaspore bank and vegetation. The most successful treatment combination was cutting twice per yr with low grazing plus C. vulgaris addition as brash. Where seed is added the Pteridium litter should be disturbed. Copyright © 2007 John Wiley & Sons, Ltd.     

Responses of butterfly and moth species to restored cattle grazing in semi-natural grasslands

The effects of restorative grazing on the abundance of butterfly and moth species were studied in mesic semi-natural grasslands of SW Finland differing in management history: (1) old continuously grazed, (2) restored (with ca 5 years of reinitiated grazing), and (3) abandoned former pastures.Generalized linear modelling of species abundances and indicator species analysis produced qualitatively similar results. Only three species (Polyommatus icarus, Lycaena hippothoe and Camptogramma bilineatum) were most abundant in old pastures, whereas 12 species (Polyommatus semiargus, Polyommatus amandus, Brenthis ino, Aphantopus hyperantus, Scopula immorata, Idaea serpentata, Scotopteryx chenopodiata, Epirrhoe alternata, Cybosia mesomella, Polypogon tentacularius, Hypena proboscidalis and Cryptocala chardinyi) were most abundant in abandoned pastures. None of the old-pasture species had become more abundant in restored pastures. Three species, Epirrhoe hastulata, Xanthorhoe montanata and Chiasmia clathrata, occurred equally abundantly in abandoned and in restored pastures indicating a slow progress of restoration.Species associated with old pastures differed from species associated with abandoned pastures in their recent distributional changes in Finland. The species of old pastures showed decreasing trends, whereas those of abandoned pastures showed mainly increasing trends in their distribution. In five out of 11 species, the preferred successional stage differed markedly between this study and previous studies conducted in Central Europe.We conclude that (1) ca 5 years of restorative grazing in mesic grasslands has been insufficient for the colonisation of old-pasture species in the restored sites, (2) different management intensities are needed regionally for the maintenance of grassland insect diversity and (3) application of the knowledge on successional preferences of different species in conservation management, even in climatically similar regions, should be made with caution.     

The feasibility of using soil seed bank for natural regeneration of degraded sandy grasslands

Desertification in degraded grasslands is manifested through the development of bare sandy patches, which eventually lead to habitat fragmentation. The ability of these bare sandy patches to regenerate naturally through in-situ soil seed banks is not well understood. To fill this knowledge gap, we randomly selected 24 bare sandy patches with areas ranging from 19 to 898 m² in a desertified grassland of the Horqin sandy land, Northern China to determine whether soil seed bank can be used for natural regeneration of bare sandy patches. Species composition and density of soil seed bank as well as aboveground vegetation composition, abundance and coverage were investigated. We then determined their relationships with in-situ habitat characteristics. Our observations showed that the studied area had low soil seed bank density and species richness, as well as depauperate soil seed bank communities. Consequently, local soil seed bank was not able to provide sufficient seed source for natural regeneration. This was indicated by the relationships between aboveground vegetation, soil seed bank and the in-situ habitat characteristics. For bare patches with an area between 300 m² and 900 m², increase the soil seed bank density and species richness should be the main restoration measures. For bare patches with a small area of less than 50 m², restoration of vegetation density should be the main measure. Our data highlighted that different extents of desertification, indicated by different bare patches, are requiring distinct restoration measures.     

Genetic consequences of using seed mixtures in restoration: A case study of a wetland plant Lychnis flos-cuculi

Sowing with seed mixtures is a common practice in restoring species-rich communities in areas with impoverished species pools. The potential genetic consequences of using these mixtures, however, are poorly understood and often not considered in practical restoration. We investigated genetic diversity, inbreeding and genetic structure of samples collected from 26 populations of the common wetland plant species Lychnis flos-cuculi in an agricultural region in Switzerland. Some of these populations were natural, while others had been sown several years ago. This enabled us to compare the genetic composition of populations of indigenous origin with those originating from commercially produced seed mixtures. Gene diversity and allelic richness were similar in natural and sown populations. In contrast, inbreeding coefficients were three times higher in sown than in natural populations. The sown populations were genetically distinct from the native populations. We distinguished two homogeneous gene pools that presumably originated from different source populations used to produce seed mixtures. The use of commercially produced seeds may alter the genetic diversity and structure of plant populations. The observed higher inbreeding coefficients of sown populations could lead to reduced population viability. To restore genetically diverse populations, the seeds for further propagation should be collected from numerous individuals in large and non-isolated populations nearby restored sites. Ex situ stocks for the production of commercial seed mixtures should only be propagated for a few generations to avoid negative effects such as inbreeding or loss of local adaptation.     

元谋干热河谷山地植被修复区土壤种子库研究

 为了解干热河谷不同植被修复方法的土壤种子库的变化模式,采用对不同处理地段(包括水平阶间坡面、自然坡面、沟底)和对照(放牧地)的土壤种子库组成、大小进行比较研究的方法,研究元谋干热河谷山地植被修复区的土壤种子库。结果表明:1)植被修复区土壤种子库密度、丰富度均大于对照区;2)修复区内第2年土壤种子库密度、丰富度均大于第1年;3)水平阶间坡面和各类型间的土壤种子库密度差异显著;4)种子库中草本植物占很大比例;5)孔颖草和扭黄茅是种子库2大优势种。研究项目所采取植被修复措施在很大程度上改善土壤种子库的数量结构和物种组成。     

Cryptic genetic bottlenecks during restoration of an endangered tropical conifer

Forest restoration programmes aim to use material for re-planting that is genetically diverse and not inbred. However, restricted seed sampling, high variance in reproductive output, and the production of inbred seeds that survive in the nursery but not in the wild can lead to forest restoration stock being genetically compromised. The aim of this study was to evaluate whether the reproductive biology of the New Caledonian endemic conifer Araucaria nemorosa makes it susceptible to these genetic problems and to assess whether there is evidence for genetic bottlenecks and elevated inbreeding in nursery stock compared to seedlings and adults from wild source populations. Reproductive output was low with high variance among trees (only 14% of adult trees surveyed produced mature cones, >50% of examined cones had <10 viable seeds). Evidence for an extreme genetic bottleneck was detected in a nursery population established from cones collected from adult trees. A second nursery population established with seed collected from the forest floor showed no evidence of a genetic bottleneck, but was inbred compared to its wild source population. In light of these results, we do not recommend collecting cones directly from A. nemorosa as an efficient means of establishing genetically diverse stock for restoration programmes. Collecting seed from the forest floor is likely to be more effective, but the planting stock may contain a high proportion of inbred individuals. Collecting established wild seedlings already subjected to natural selection is suggested as an alternative method of maximising the diversity captured, whilst minimising sampling effort and proportion of inbred individuals.     

Future prospects for the rare, late-flowering Gentianella germanica and Gentianopsis ciliata in Dutch nutrient-poor calcareous grasslands

We discuss the population biology of two calcareous grassland gentians, Gentianella germanica and Gentianopsis ciliata, in relation to the habitat management currently practiced in The Netherlands. There, at the margin of their range, both species are rare. Gentianella germanica persists on six remaining locations, whereas Gentianopsis ciliata, with two populations, is nearly extinct. Gentianella germanica is a strict biennial, Gentianopsis ciliata an iteroparous perennial. Both species depend on insects for seed production and suffer from low insect visitation. Pollination experiments in one Dutch population demonstrated that Gentianopsis ciliata is self-compatible, but hardly sets any seed under natural conditions due to pollen limitation. The low reproductive success of both species is partly due to the low pollinator densities at their late flowering time, partly caused by the small population size of the gentians themselves, and partly a result of mowing too early. The latter has destroyed the seed crop of several subsequent years in one population of Gentianopsis ciliata and some of Gentianella germanica. In Gentianella germanica, the early mowing and low insect visitation seems to have resulted in selection of less herkogamous and consequently more autofertile individuals. The perspectives for Gentianopsis ciliata are currently extremely poor in The Netherlands. Under the present circumstances, extinction will most likely occur within 10-20 years. Population reinforcement (seeding, artificial cross-pollination with nearby populations) should be considered if we want to conserve this species. For both gentians, but also of other flagship species of nutrient-poor calcareous grasslands, the total grassland area needs to be enlarged and must constitute an interconnected network of reserves. The traditional management method, sheep grazing, is to be preferred over mowing, but only if the flock visits each grassland patch or reserve for only a short time of less than a day, and with intervals of more than 2 weeks between visits. If mowing is preferred for other reasons, it should be done rotationally, and not before October.     

Hay strewing, brush harvesting of seed and soil disturbance as tools for the enhancement of botanical diversity in grasslands

Since the middle of the last century agricultural intensification within Europe has led to a drastic decline in the extent of botanically diverse grasslands. Whilst measures to enhance the diversity of agriculturally-improved grasslands are in place, success has often been limited. One of the primary factors limiting success is the paucity of sources of propagules of desirable species in the surrounding landscape. The restoration of two contrasting grassland types (lowland hay meadow and chalk grassland) was examined using a replicated block experiment to assess the effectiveness of two methods of seed application (hay strewing and brush harvesting) and two methods of pre-treatment disturbance (power harrowing and turf stripping). The resulting changes in botanical composition were monitored for 4 years. Seed addition by both methods resulted in significant temporal trends in plant species composition and increases in plant species richness, which were further enhanced by disturbance. Power harrowing increased the effectiveness of the seed addition treatments at the lowland hay meadow site. At the chalk grassland site a more severe disturbance created by turf stripping was used and shown to be preferable. Whilst both hay strewing and brush harvesting increased plant species richness, hay strewing was more effective at creating a sward similar to that of the donor site. Soil disturbance and seed application rate at the recipient site and timing of the hay cut at the donor site are all factors to be considered prior to the commencement of restoration management.     

Light and Temperature Requirements during Germination of Potential Perennial Grasses for Rehabilitation of Degraded Sandy Arabian Deserts

Few plants can tolerate the loose sandy‐soils of the arid deserts. Selection of native plants that could be used in rehabilitation of degraded deserts necessitates information about their seed dormancy and germination requirements. This study assessed the effects of light and temperature requirements during germination for eight common perennial grasses that have the potential to rehabilitate the arid Arabian deserts. The selected grasses vary considerably in seed mass. Germination of clonally propagated grasses (six species) was significantly greater, but slower, than that of two non‐clonal grasses. Four of these six species (Lasiurus scindicus , Panicum turgidum , Aeluropus lagopoides and Halopyrum mucronatum ) produce larger seeds and attained greater germination in both light and darkness at a wide range of temperatures. However, the other two (Centropodia forsskaolii and Coelachyrum piercei ) produce medium‐sized seeds with higher dormancy. Smaller seeds of Sporobolus arabicus were positively photoblastic at all temperatures, but those of Sporobolus spicatus were neutrally photoblastic at lower temperatures and positively photoblastic at higher temperatures. There was a significant negative relationship between seed mass and relative light germination, indicating that small seeds require more light during germination. It is recommended to use seeds of the six clonal grasses for restoration of degraded arid deserts. The ability of these grasses to germinate in different light and temperature regimes indicates their ability to germinate at any time of the year, even when seeds are buried. The light and temperature requirements of the different grasses are explained in the light of their adaptation and distribution in natural habitats. Copyright © 2017 John Wiley & Sons, Ltd.     

Fat but slim: Criteria of seed attractiveness for earthworms

Earthworms were shown to significantly affect seeds and seedlings survival via their ingestion and digestion for nutritive purposes. Such selective feeding of earthworms on plant seeds is likely to favour certain plant species and to affect seed bank composition, plant recruitment and plant community structure. Relationships between earthworms and seeds, particularly seed traits that determine attractiveness of seeds for earthworms, are yet to be determined. In this study, the influence of six seed traits was tested on the ingestion, digestion and germination of seeds by two earthworm species (Lumbricus terrestris, anecic and Satchellius mammalis, epigeic). The seed traits tested were their length, width, weight, shape, oil content and the presence of trichomes on their surface. Each earthworm species was introduced into a microcosm with eleven seed species from a chalk grassland that represented those different traits. Ingested, digested and germinated seeds were counted after voiding the guts of the earthworms. Univariate and multivariate analyses showed that seed length, width, weight and seed oil content could significantly affect the ingestion of seeds for both earthworm species. Seed width and seed oil content were the two traits that influenced the digestion of seeds the most, but only for L. terrestris. We also found that seed ingestion was earthworm species-specific but we found no correlation between earthworm traits and number of ingested or digested seeds. Few seeds germinated from L. terrestris casts and no seeds germinated from S. mammalis casts. Implications in terms of plant evolution strategies are further discussed.     

SOIL SEED BANK CHARACTERISTICS BENEATH AN AGE SEQUENCE OF CARAGANA MICROPHYLLA SHRUBS IN THE HORQIN SANDY LAND REGION OF NORTHEASTERN CHINA

To understand how shrub cover affects the spatiotemporal patterns of the soil seed bank and to assess the role of vegetation in the restoration of desertified land in a semi‐arid region of China, we investigated the species composition and seed density of the soil seed bank under and outside the canopies over two seasons for an age sequence of Caragana microphylla shrubs in the Horqin Sandy Land region, Inner Mongolia. The results showed that a total of 24 plant species seeds were present in the soil seed bank, of which 20 were annuals or biennials. The seed densities in the soil seed bank were in the range of 830 – 13882·5 seeds m⁻² at 10 cm depth. Species richness in the soil seed bank did not increase as the shrubs aged, whereas the seed densities increased significantly. Five annual species: Setaria viridis, Eragrostis pilosa, Chenopodium acuminatum, Chenopodium glaucum and Corispermum acuminatum, contributed above 90 per cent of the seeds to the soil seed bank. On the basis of seed characteristics and seed reduction amount during the growing season, we concluded that it represents a mixture of persistent and transient seeds in different proportions. More seeds accumulated under the canopies than outside the mature shrub cover, but no significant difference was found the younger cover. These results suggest that shrub size and age had an important role in augmenting seed abundance of the soil seed bank but not the species richness. We confirmed the important effects of shrub cover on seed accumulation and vegetation recovery, especially the value of more mature age vegetation for countering land degradation. Copyright © 2012 John Wiley & Sons, Ltd.