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.     

Influence of land use history on seed banks in European temperate forest ecosystems: a review

This study summarises European research on seed banks in temperate forest systems and analyses for differences in seed bank composition between geographically scattered forests with a different land use history. Special attention is given to seed bank characteristics of ancient forest species. Results of Detrended Correspondence Analysis suggest that historical land use is a key factor in determining the seed bank composition. Particularly seed banks of forests on former heathland sites differ from seed banks of ancient forest due to a high contribution of early successional species. The effect of former land use decreases after 50 yr, due to seed senescence. Total seed density decreases with recent forest age. Seed bank composition of eastern European forests is different from northern or western European forests, a difference which is mainly caused by species with a higher Ellenberg indicator value for continentality, temperature and reaction. In general, ancient forest species are poorly represented. Only a limited number is mentioned to have a persistent seed bank, and their densities are relatively low, which means that restoration of typical ancient forest vegetation can not rely on the seed bank. However, there is still a considerable lack of knowledge concerning seed bank and germination characteristics of forest species.     

Environmental limitation contributes to the differential colonization capacity of two forest herbs

Question: The recovery of forest plant communities in post‐agricultural landscapes is largely determined by dispersal constraints, but can environmental legacies of former land use additionally limit the recolonization of recent forests by forest herbs? Location: Ancient forest and recent forest on former heavily fertilized agricultural land (Muizenbos, northern Belgium). Methods: Seeds and adults of two forest herbs with similar life‐history traits, but contrasting colonization capacity – the fast‐colonizing Geum urbanum and the slow‐colonizing Primula elatior– were introduced into both ancient and recent forest sites. Soil conditions and plant tissue nutrient concentrations were measured to characterize habitat quality. To determine whether the introduced species could successfully establish and persist, we monitored recruitment, longevity and adult performance during 8 years in permanently marked plots. Results: Phosphorus availability was ten times higher in recent forest soils and was also reflected in the plant tissue samples. Species longevity was clearly lower in recent forest sites indicating higher turnover. The fast‐colonizing G. urbanum counterbalanced this lower longevity by new establishment, while the slow‐colonizing P. elatior dropped below the number of originally introduced individuals. Additionally, G. urbanum performed better in recent forest sites in contrast to P. elatior. Conclusions: Even when dispersal constraints of the slow‐colonizing forest herb P. elatior are eliminated through introduction, environmental conditions in recent forest sites additionally restrict its recruitment, longevity and performance. These experimental results suggest that environmental constraints may strengthen the differences in colonization capacity among forest herbs if slow dispersers also tend to be less likely to establish.     

Seed bank and vegetation composition of forest stands of varying age in central Belgium: consequences for regeneration of ancient forest vegetation

Vegetation composition differs significantly between ancientand recent forest, due to slow colonization capacity of typical forest speciesand the higher abundance of early successional species in recent forest.However, little is known about differences in persistent seed bank compositionbetween ancient and recent forest and about the interaction between seed bankand vegetation in relation with forest age. We surveyed the seed bank and theunderstorey vegetationcomposition in transects from ancient to recent forest. Seed bank and fieldlayer vegetation characteristics and similarity between seed bank andvegetationwere analysed in relation to recent forest age and distance to the ancientforest. A total of 39 species and 14,911 seedlings germinated, whichcorresponds with a seed density of 12,426 seeds/m².Total seed density is significantly higher in the youngest recent forest parcel(55 years). Also the seed bank composition in the youngest forest parceldifferssignificantly from the other parcels. After a longer period of reforestation,the seed bank approaches that of the ancient forest, suggesting seed bankdepletion, although the seed bank is permanently replenished to some extent byseed bank forming species from local disturbances. Seed bank composition doesnot change significantly with distance to the ancient forest. Similaritybetween seed bank and vegetation composition, nomatter the forest age, is very low, but decreases with increasing forest age.The most frequent species in the vegetation are absent in the seed bank andvice versa. The contribution of forest species is highin the vegetation and they almost not occur in the seed bank, while species offorest edges and clearings, and species of disturbed environments are morefrequent in the seed bank. The seed bank is mainly composed of earlysuccessional species of former forest stages or species which temporary occurinsmall-scale disturbances. The seed bank may enhance the negative effects ofearlysuccessional, mainly competitive species to the forest species richness in therecent forest. In this respect, forest management should minimise forestdisturbances, to prevent germination of competitive species form buriedseeds.     

Land‐use and fire history effects on post‐fire vegetation dynamics in eastern Spain

Question: Is post‐fire, medium‐term vegetation dynamics determined by land‐use or fire history prior to fire? Location: South‐facing slope in the Gallinera valley, Alicante province, eastern Spain. Methods: After mapping the land‐use and fire history of the study site using photo‐interpretation, we sampled vegetation structure on a set of plots representing the most frequent land‐use and fire history combinations on an area burned six years before sampling. We studied the effects of land‐use history, comparing the one‐fire land‐use trajectories. We analysed the effects of fire history; comparing one‐ and two‐fire plots for both previously cropped and uncropped areas. Results: Most variables were not significantly different between the earliest abandoned plots (abandoned at least 38 years before the fire) and the uncropped plots. On the most recently abandoned plots (abandoned between one and four years before the fire), the therophyte richness and the ratio of seeder: resprouter richness were significantly greatest. Different fire recurrences did not determine different post‐fire vegetation on either the uncropped or the early abandoned plots (all dominated by fire‐recruited seeder shrubs). The most recently abandoned plots had a lower resilience to fire. Conclusions: Land‐use history and recent pre‐fire land use, in particular, determined the post‐fire vegetation in the medium term. The vegetation composition converged during secondary succession among land‐use histories. Increasing fire recurrence had a small effect on mature plant communities, due to the combination of life‐history traits determining the response to fire of the dominant species.     

普洱市周边地区4种土地利用类型土壤种子库特征

通过对云南普洱市周边地区次生季风常绿阔叶林、针阔混交林、人工更新形成的针叶林及茶园等4种土地利用类型的野外调查及土壤种子库的萌发实验,探讨其土壤种子库的密度大小、物种丰富度和组成及与地上植被的关系。结果表明:干扰强度与频度不同导致土地利用类型之间土壤种子库密度与物种丰富度存在较大差异,土壤种子库密度大小顺序为:针叶林(248.67±116.86)粒·m-2>针阔混交林(186.00±43.27)粒·m-2>次生季风常绿阔叶林(107.33±16.48)粒·m-2>茶园(51.67±10.17)粒·m-2;茶园土壤种子库物种丰富度要显著低于其他类型。4种土地利用类型土壤种子库生活型组成差异极显著,主要以草本植物组成,以菊科与禾本科占优势;针阔混交林的草本植物种子密度最多,非森林的原生物种是草本植物的主要组成;针叶林外来物种的种子密度要显著高于其他类型,紫茎泽兰(Eupatorium adenophorum)是其主要组成。土壤种子库与地上植被的相似性系数较低,其大小顺序为:次生季风常绿阔叶林(0.175)<针阔混交林(0.176)<针叶林(0.215)。     

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.     

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.     

Immediate increase in plant species richness after clear‐cutting of boreal herb‐rich forests

Abstract. The flora of clear‐cuttings with soil scarification in forests was compared < 1–2 yr after cutting with that in mature herb‐rich forests in SW Finland. The total and mean numbers of vascular plant species both in the study areas and in the sample plots, were almost double in clear‐cut areas compared to mature forests. Clear‐cuttings and mature forests were distinctly separated by multivariate analyses (DCA). Several dozen species not found in forests were common in clear‐cut areas. Most of them probably belong to the neglected native species pool of early boreal forest succession and are dependent on the long‐term persistent seed bank or effective wind dispersal. It is emphasized that in forests many plant species are confined to the very early stages (< 2 yr) after disturbance. The storage effect of the long‐term persistent seed bank is crucial for the maintenance of plant diversity in boreal forests. Probably a considerable part of the flora of agricultural areas is composed of species that were originally disturbance dependent forest plants. Scarification is beneficial to disturbance dependent plants and may be useful in restoration of populations of species of early succession.     

Effects of Selective Vegetation Thinning on Seed Removal in Secondary Forest Succession1

Seed removal was assessed for two tree species in three forest types: (1) secondary forest with and (2) without selective vegetation thinning, and (3) mature forest. Selective vegetation thinning meant the removal of all stems ≤3 cm in diameter of secondary‐forest species and was intended as a management technique to accelerate succession toward mature forest. Thinning did not have an effect on seed removal. One of the species showed lower seed removal in mature forest compared to secondary forest.     

Floristics of soil seed banks on agricultural and disturbed land cleared of tropical forests

Little is known about how soil seed banks vary in germination, composition, and density under different land uses after tropical forest conversion. Seed banks can potentially act as one source of regeneration for reforestation of old agricultural lands. Our study documents the composition and density of germinants in soil seed banks from four land uses types surrounding the Sinharaja forest in southwest Sri Lanka. These include: (1) kekilla fern lands; (2) pine plantations; and (3) tea. These were compared to the adjacent (4) mature rainforest. During the 6‐month period of monitoring, we recorded 1,674 germinants (0.036 germinants/cm³ soil), representing 46 species. Germinants of tree and shrub species were restricted to the pine and rainforest soils and all of them are considered pioneers. The soils of the rainforest had the lowest species richness, density, and diversity of germinants; tea lands comprised much higher richness, Shannon diversity, and density. However, almost all germinants in tea were grasses and herbs as compared with other land uses. A multivariate analysis of the germinants of soil seed banks revealed that the four land use types comprise very different compositions and abundances, some of which can be associated with differences in growth habit (trees, shrubs, vines, herbs, grasses). Our results suggest that pine plantations may facilitate some tree and shrub regeneration. However, the seed banks beneath tea and kekilla fern land do not comprise any woody plant species. This may explain why agricultural lands such as tea do not revert back to forest easily.     

Fire and regeneration: the role of seed banks in the dynamics of northern heathlands

Questions: How do species composition and abundance of soil seed bank and standing vegetation vary over the course of a post‐fire succession in northern heathlands? What is the role of seed banks – do they act as a refuge for early successional species or can they simply be seen as a spillover from the extant local vegetation? Location: Coastal Calluna heathlands, Western Norway. Methods: We analysed vegetation and seed bank along a 24‐year post‐fire chronosequence. Patterns in community composition, similarity and abundances were tested using multivariate analyses, Sørensen's index of similarity, vegetation cover (%) and seedling counts. Results: The total diversity of vegetation and seed bank were 60 and 54 vascular plant taxa, respectively, with 39 shared species, resulting in 68% similarity overall. Over 24 years, the heathland community progressed from open newly burned ground via species rich graminoid‐ and herb‐dominated vegetation to mature Calluna heath. Post‐fire succession was not reflected in the seed bank. The 10 most abundant species constituted 98% of the germinated seeds. The most abundant were Calluna vulgaris (49%; 12 018 seeds m^?2) and Erica tetralix (34%; 8 414 seeds m^?2). Calluna showed significantly higher germination the first 2 years following fire. Conclusions: Vegetation species richness, ranging from 23 to 46 species yr^?1, showed a unimodal pattern over the post‐fire succession. In contrast, the seed bank species richness, ranging from 21 to 31 species yr^?1, showed no trend. This suggests that the seed bank act as a refuge; providing a constant source of recruits for species that colonise newly burned areas. The traditional management regime has not depleted or destroyed the seed banks and continued management is needed to ensure sustainability of northern heathlands.     

Clear‐felling effects on colonization rates of shade‐tolerant forest herbs into a post‐agricultural forest adjacent to ancient forest

Question: Does clear‐felling influence forest herb colonization into post‐agricultural forest? Location: A stand of poplar cultivars with a dense understorey of Acer pseudoplatanus in Muizen forest (northern Belgium), planted in 1952 on farmland adjacent to ancient forest and clear‐felled in 1997. Methods: Shade‐tolerant forest herbs were surveyed in 112 grid‐based sample plots: just before clear‐felling, and 5 and 10 yr afterwards. Shade‐tolerant herbs were subdivided into ancient forest species (AFS) and other shade‐tolerant species (OSS). Effects of clear‐felling on species number per plot, total cover per plot and colonization rate of species groups were compared using non‐parametrical tests. Species number per plot was modelled by means of generalized linear mixed models (GLMMs), with inventory time, distance to the nearest parcel edge, and cover of light‐loving species (LS) as explanatory variables. The C‐S‐R signature (competitive, stress‐tolerant and ruderal strategies, respectively) shift of sample plots was calculated on the selected shade‐tolerant species. Results: Frequency of most species increased during the 10‐yr period. Number of OSS increased more and faster than that of AFS. OSS increased to the level of the adjacent forest, but was lower where LS cover remained high. There was a positive correlation between the change of the colonization rate and the competitive plant strategy. Conclusions: We assume that clear‐felling stimulated generative reproduction of shade‐tolerant herbs, whereas quickly emerging woody species controlled competitive exclusion by LS. Succession of dark and light phases, such as provided by an understorey managed as a coppice, could promote colonization of shade‐tolerant herbs into post‐agricultural forest.     

山西文峪河上游河岸林的土壤种子库与树种更新特征

以山西文峪河上游13种典型的河岸林为研究对象,通过土壤种子库和树种更新研究,分析群落种子库与林下更新随演替进展的变化趋势,以及该区河岸树种的繁殖对策。结果表明：13种群落的土壤种子库密度间于1290±103～3950±154粒/m2,63.5%的种子留存于0～5 cm的层次;种子库包含49种植物,以多年生草本为主,存在耐干扰种和湿地植物的种子;处于相同或相邻演替阶段的群落,种子库相似性较高;随演替进展,种子库密度、丰度、Shannon-Wiener指数及种子库与地上植被的相似性均呈降低趋势;处于演替后期的青杄Picea wilsonii林存在丰富的＂青杄幼苗库＂;先锋种白桦Betula platyphylla的种子存在于演替各阶段的群落中,储量丰富,其更新主要依赖于风媒种子,并存在少量萌蘖;青杄、白杄P.meyeri、华北落叶松Larix principis-rupprechtii、油松Pi-nus tabulaeformis和辽东栎Quercus liaotongensis的种子库损耗严重,没有或仅存少量种子,其中云杉和油松的更新幼苗幼树多,属持久幼苗库更新;华北落叶松幼苗幼树少,且仅出现于林缘或林窗等开阔地,属植被空隙中季节性更新;辽东栎主要依赖丰富的幼苗库进行更新,同时存在一定的萌蘖;青杨Populus cathayana以大量风媒种子更新结合营养扩展。     

Fire,aridity and seed banks. What does seed bank composition reveal about community processes in fire‐prone desert?

Questions: The relationship between fire, aridity and seed banks is poorly understood in plant community ecology. We tested whether there was a close correspondence between the seed bank and standing vegetation composition with time‐since‐fire in a desert. We also examined whether longer‐lived species showed seed limitation relative to more ephemeral species, as this could influence grass‐woody ratios in a major biome. Location: Dune hummock grasslands/shrublands of central Australia. Methods: The effects of time‐since‐fire on floristic and functional group composition were examined by comparing plots unburned since 1984 against plots that had been burned in 2002. Three methods were used to quantify seed abundances: a germination trial using heat and smoke application, a flotation method, and a sieving method. Results: Seed bank densities were very low (<3000 m^?2). Species similarity between the seed bank and standing vegetation was high at sites recently burned (0.86) and low in sites long‐since burned (0.52). The relative abundance of ephemeral species in the seed bank peaked in recently burned plots, but the relative abundance of seeds of woody species did not match the pattern of abundance in the standing vegetation. Remarkably, the dominant perennial grasses and woody species were either absent from the seed bank or present at extremely low abundances. Discussion: Differences in the relative abundance of ephemeral species between standing vegetation and seed bank relate to the post‐fire succession process. The small soil pool of seed from woody species may be explained by allocation to belowground carbohydrate storage over seed production. Field observations suggest, however, that production of strongly dormant seed can be prolific and that high levels of seed predation make this system strongly seed‐limited. The discovery of this seed bank syndrome indicates that shifts in grass‐woody ratios can be driven by the juxtaposition of unpredictable seed rain and fire events in these desert dunes. However, estimates of grass‐woody ratios due to changing fire regimes will be difficult to predict.     

Seed bank dynamics and tree‐fall gaps in a northwestern Mexican Quercus‐Pinus forest

Questions: How does the seed bank respond to different types of tree‐fall gaps and seasonal variations? How does the soil seed bank influence recovery of the standing vegetation in the mature forest and tree‐fall gaps? Location: 1800 — 2020 m a.s.l., Quercus‐Pinus forest, Baja California Sur, Mexico. Methods: Seed size, species composition and germination were estimated under different environmental conditions during dry and rainy seasons: a mature forest plot and gaps created by dead standing trees, snapped‐of f trees and uprooted trees. The soil seed bank was investigated using direct propagule emergence under laboratory conditions, from soil cores obtained during both seasons. Results: 21 species, 20 genera and 14 families constitute the seed bank of this forest community. Fabaceae, Asteraceae, Euphorbiaceae and Lamiaceae were the most frequently represented families in the seed bank. Floristic composition and species richness varied according to the different modes of tree death. Species composition of seed banks and standing vegetation had very low similarity coefficients and were statistically different. Seed bank sizes varied between 164 and 362 ind.m^‐2 in the mature forest plot for the dry and rainy seasons, respectively, while soil seed bank sizes for gaps ranged between 23–208 ind.m^‐2 forthe dry season and between 81–282 ind.m^‐2 for the rainy season. Conclusions: Seed bank sizes and germination response were always higher in the rainy season under all the environmental conditions analysed. Results suggest that timing responses to gap formation of the soil seed bank could be more delayed in this temperate forest than expected.     

Resilience,persistence and relationship to standing vegetation in soil seed banks of semi‐arid Australian old fields

Questions: Do soil seed banks of semi‐arid grasslands reassemble after abandonment from cultivation? Do seeds of native and exotic species persist in the soil? Does time since abandonment affect compositional similarity between the vegetation and seed bank? Does the seed bank contribute to resilience in the vegetation? Location: Native grasslands in northern Victoria, Australia. Methods: Seed bank sampling was conducted in spring and autumn over 3 yrs, across a 100‐yr chronosequence. Species richness, composition and germinant density were determined using the seedling emergence method. Seed persistence was assessed by comparing seed densities in spring and autumn. Seed bank composition was compared with the vegetation. Results: The spring seed bank was dominated at all stages by sedges and rushes; hence, native species richness and seed density were largely unaffected by abandonment. In autumn, grassland species contributed more to the seed bank, but richness was reduced after abandonment and showed little recovery, although seed density partially recovered. Seed bank composition showed some recovery in both seasons. Most species had low persistence in the soil. Compositional similarity between the vegetation and seed bank was greater in old fields than uncultivated grasslands in spring, but not autumn. Conclusions: Resilience varied among seed bank parameters and seed banks had low functional importance. Patterns in the seed bank followed, rather than caused, those in the vegetation. Thus, vegetation recovery cannot rely on the seed bank and persistent seeds were not the key mechanism of resilience in the vegetation.     

Afromontane old-field vegetation: secondary succession and the return of indigenous species

South‐west Uganda primarily holds afromontane forests within three protected areas: Mgahinga Gorilla National Park, Echuya Forest Reserve and Bwindi Impenetrable National Park. All forests contain portions of old‐field vegetation. The central question of this study, then, is whether and how natural regeneration of afromontane vegetation would take place. A successional pathway consisting of nine plant communities was found for the first 2 years after cessation of agricultural use. A return of afromontane species despite of an initial dominance of neophytes, a diversification of life form spectra and a growing importance of endozoochory with time belonged to the conspicuous characteristics of this secondary succession. To obtain an insight into the role of birds and buffaloes as possible vectors for seed input, I examined their faeces with regard to germinable seeds. Both, bird faeces, as well as buffalo faeces contained germinable seeds originating from the forest flora. Thus, animal dispersal from the forest into the regenerating zones could be documented. The regeneration potential of the soil‐seed bank seems to be limited in its time scale, and only an initial regeneration capacity could be found. A further progressive succession into a secondary afromontane forest depends on an input of diaspores from undisturbed forest sites. Zoochory appears to be one of the most important dispersal mechanisms.     

Soil seed banks of two montane riparian areas: implications for restoration

Understanding the role of seed banks can be important for designing restoration projects. Using the seedling emergence method, we investigated the soil seed banks of two montane, deciduous riparian forest ecosystems of southeastern Arizona. We contrasted the seed banks and extant vegetation of Ramsey Canyon, which is the site of riparian restoration activities, with that of Garden Canyon, which has been less affected by human land uses. Fewer plant species were found at Ramsey Canyon than Garden Canyon, for both the seed bank and extant vegetation, and the vegetation at Ramsey Canyon (seed bank and extant) had consistently drier wetland indicator scores. As well, vegetation patterns within sampling zones (channel margins and adjacent riparian forests) differed between canyons. At Garden Canyon channel margins, the seed bank and extant vegetation had relatively high similarity, with herbaceous wetland perennial species dominating. Extant vegetation in the floodplain riparian forest zone at Garden Canyon had a drier wetland indicator score than the seed bank, suggesting that the floodplains are storing seeds dispersed from wetter fluvial surfaces. Vegetation patterns for Ramsey Canyon channel margins were similar to those for Garden Canyon floodplains. Vegetation patterns in the Ramsey Canyon riparian forest zone were indicative of non-flooded conditions with an abundance of upland species in the soil seed bank and extant vegetation. Channel geomorphology measurements indicated that much of the riparian forest zone at Ramsey Canyon is functionally a terrace, a condition that may be a legacy of channel erosion from historic land uses. Steep, erodible channel slopes may contribute to the low seed bank germinant density at Ramsey Canyon channel margins, and narrower flood-prone area may explain the greater terrestrialization of the vegetation in both sampling zones. We recommend testing the use of donor soils from more diverse stream reaches to restore biodiversity levels at Ramsey Canyon, following restoration activities such as channel-widening. Seed banks from Garden Canyon, for example, although predominantly consisting of herbaceous perennials, would supply species with a range of moisture tolerances, life spans, and growth forms. We also recommend that restorationists take care not to harm seed banks exposed during removal of introduced species; at Ramsey Canyon, soil seed banks were equally diverse in areas with high and low cover of the introduced Vinca major (a legacy of Ramsey Canyon land use).     

Seed bank,seed dispersal and vegetation cover: Colonization along a newly‐created river channel

Question : What is the relative importance of the initial seed bank and subsequent seed dispersal for floristic composition of bank vegetation two years after creation of a newly‐cut reach of a river channel? Location : River Cole, West Midlands, United Kingdom. Methods : We took bank and bed sediment samples from a 0.5‐km reach of a new river channel cut into intact flood‐plain. After river diversion, seed samples deposited on artificial turf mats placed on the river banks and flood‐plain edge were taken in summer and winter 2002 and 2003. Seed rain samples from funnel traps were taken during summer 2002 and 2003. We undertook greenhouse germination trials to assess viable seed species within these samples. In summer 2004, we surveyed river bank vegetation. Agglomerative cluster analysis was used to investigate floristic similarity between seed bank, seed rain, seed deposition samples and final bank vegetation cover. DCA was used to explore contrasts between the samples and to assess whether these reflected interpretable environmental gradients. Results : Seed rain samples contained a small subset of species in the summer depositional samples. 38 species were found within the final vegetation, the seed bank, and at least one of the four sets of depositional samples; a further 30 species not present in the seed‐bank samples were present in at least one of the four sets of depositional samples and the final vegetation. Floristic composition of the vegetation was most similar to the depositional samples from winter 2002 and 2003 and summer 2003. DCA axis 1 reflected a time sequence from seed‐bank samples through depositional samples to the final vegetation. Conclusions : Newly cut river banks were colonized rapidly. Seed remobilization and hydrochorous transport from the upstream catchment are important for colonization. Species richness was highest in samples deposited during winter when high river flows can remobilize and transport viable seeds from upstream. This process would also have enhanced the species richness of seed production along the banks during the second summer (2003).