Does seed retention potential affect the distribution of plant species in highly fragmented calcareous grasslands?

Long-distance dispersal is a crucial factor in the life-cycle of plants, especially in our modern, highly fragmented landscapes. Because natural herds of large animals have disappeared and grazing practices have been abandoned, important potential vectors for seed dispersal over large distances may have been lost. In the context of the re-establishment of grazing management for nature conservation purposes, it is therefore important to gain insight in the ability of grazing animals to act as seed dispersal vectors. Whereas local dispersal mainly occurs through standard vectors typically described based on morphological adaptations of the diaspore, large herbivores act as non-standard seed dispersers. Therefore, traditional dispersal classes are loosing scientific relevance and continuous predictors of dispersal potential have been proposed. Here, we explored whether dispersal related plant traits, including the "seed retention potential", could explain the distribution patterns of 180 plant species over 64 fragmented semi-natural calcareous grasslands in Belgium. The distribution of habitat specialist plant species was strongly determined by the degree of isolation of the grasslands. Interestingly, species distribution patterns were clearly linked with a species' potential to migrate through large grazers, as quantified by its retention potential: species producing seeds with high retention capacity were less affected by habitat isolation. Categorical dispersal classes based on seed morphology did not explain a species' response to fragment isolation. Although seed retention potential outperformed simple seed dimensional traits, plant height, which is an indicator of epizoochorous attachment potential, was even more important. Therefore we suggest further extension of the epizoochorous retention potential model by incorporating basic ecological mechanisms that effectively contribute to successful dispersal events.     

Epizoochory by large herbivores: merging data with models

The dispersal of plant seeds in the fur of large herbivores (epizoochory) is an important but complex long-distance dispersal mechanism. We developed a spatially explicit simulation model of epizoochorous seed dispersal, which was parameterized based on empirical studies of the movement and behaviour of donkeys, and the distribution, seed production, seed accessibility, seed adhesion, and seed retention on donkey fur of selected plant species in a coastal dune nature reserve in Flanders, Belgium. We compared predicted and observed seed numbers of the 14 plant species on donkey fur.

Modelled seed shadows indicate that for most species about half of all seeds dispersed by donkeys should travel a net distance of >100 m, and about 1% should travel >500 m within this more or less isodiametric 100 ha nature reserve. Seeds with longer retention times are expected to travel further than those with short retention times. Enlarging the reserve area had little impact on the forecasted dispersal distances.

Variation among plant species in the observed seed numbers found on donkey fur were well predicted by the model (R²=0.56, P=0.002), though the predictions relied on relatively crude estimates of seed production and accessibility to donkeys, indicating that more accurate estimates of these parameters are needed.

Our model confirms the important role of epizoochory in affecting long-distance seed dispersal, and provides a modelling framework for integrating the multiple components of the dispersal process.     

Epizoochorous seed dispersal in relation to seed availability – an experiment with a red fox dummy

Questions: Is the red fox a potential vector for epizoochorous seed dispersal? Can seed attachment and retention be predicted from plant and seed traits? Location: Grasslands in southern Norway. Methods: Epizoochorous seed attachment on the red fox was studied by walking a dummy fox through the vegetation and comparing seeds found on the dummy with the estimated seed availability in the vegetation. Seed retention, i.e. the ability of different seeds to stay on the fox, was estimated in a separate experiment. Seed attachment and retention were related to plant and seed traits using statistical models that account for heteroscedasticity and zero‐inflated data. Results: The majority of seeds attached to the fox originated from a few species, but also species without specific seed traits that are supposed to enhance epizoochory attached at least some seeds to the fox. The probability of seed attachment was positively related to plant height, bristle and hooked seed appendages, and negatively related to winged appendages, seed mass, and seed sphericity. Seed retention was positively related to the seed traits bristles, hooks and pappus. For several species, the results indicate a high potential for dispersal over long distances. Conclusions: In modern agricultural landscapes, large herbivores are often restricted in their mobility or are found at low densities, and other animal vectors may therefore be important for seed dispersal. In our study, a range of plant species were able to disperse by attaching seeds to, and having their seeds retained in, the fox fur some distance. We suggest that the red fox may be an important vector for epizoochorous seed dispersal in the agricultural landscape.     

The fate of sheep-dispersed seeds: Plant species emergence and spatial patterns

Sheep epizoochory has often been proposed as an important vector which can help to overcome the dispersal limitation of plants in fragmented landscapes. In order to evaluate the contribution of herbivores to recruitment especially of target species, the dispersal and post-dispersal fate of such seeds must be known. In a field experiment sheep with seeds of mainly target species (experimentally attached to their coats) were present at three sand plots for 24 h. Natural epizoochorous dispersal was already shown for most of the species in our study area. Seed detachment, trampling intensity and seed shadow were measured; seedling emergence and survival were recorded over an 8-month period. In addition, the effect of sheep trampling on seedling emergence and survival of two threatened species, Jurinea cyanoides and Koeleria glauca, were studied.     

Herbivorous mammals as seed dispersers in a Mediterranean dehesa

Endozoochrous seed dispersal by herbivorous mammals has been verified repeatedly and its possible influence on the structure and function of herbaceous communities has been suggested. Quantitative studies, however, are lacking in the field of seed dispersal via the dung of herbivore guilds in little-altered environments. The present paper analyses seed dispersal via rabbit, fallow deer, red deer and cow dung in a Mediterranean dehesa (open woodland used for hunting and ranching) during the seeding season. Dung seed content was determined by the glasshouse cultivation of eight dung samples from each herbivore, collected fortnightly between February and August. The four herbivores disperse many seeds (spring averages are 6–15 seeds per gram of dry dung and maxima of 25–70) from a large number of species (totals between 52 and 78). Dispersal seems to be mainly determined by seed production of the plant comminity. This is reflected in (i) the dissemination of a high percentage of the species present in the dehesa, (ii) great seasonal variability, related to seed production, in the amount of seeds and number of species dispersed, and (iii) a high semi-quantitative similarity of seed content in the four types of herbivore dung throughout the year. There is also important quantitative variation that depends on animal traits and feeding habits. These results and the characteristics of species found in dung suggest the adaptation of plant species to the dispersal of their seeds via herbivore gut. This process may well have profound implications for vegetation dynamics and the evolution of plant traits.     

动物与植物种子更新的关系Ⅱ．动物对种子的捕食、扩散、贮藏及与幼苗建成的关系

植物的繁殖体总是面临来自各类生物（如昆虫、脊椎动物、真菌）的捕食风险。因动物捕食引起的种子死亡率影响植物的适合度、种群动态、群落结构和物种多样性的保持。种子被捕食的时间和强度成为植物生活史中发芽速度、地下种子库等特征的主要选择压力,而种子大小、生境类型等因素也影响动物对植物种子的捕食。捕食者饱和现象被认为是植物和种子捕食者之间的高度协同进化作用的结果,是限制动物破坏种子、提高被扩散种子存活率的一种选择压力。大部分群落中的大多数植物种子被动物扩散。种子扩散影响种子密度、种子被捕食率、病原体攻击率、种子与母树的距离、种子到达的生境类型以及建成的植株将与何种植物竞争,从而影响种子和幼苗的存活,最终影响母树及后代植物的适合度。种子被动物扩散后的分布一般遵循负指数分布曲线,大多数种子并没有扩散到离母树很远的地方。捕食风险、生境类型、植被盖度均影响动物对种子的扩散。植物结实的季节和果实损耗的过程也体现了其对扩散机会的适应。许多动物有贮藏植物种子的行为。动物贮藏植物繁殖体的行为,一方面调节食物的时空分布,提高了贮食动物在食物缺乏期的生存概率;另一方面也为种子萌发提供了适宜条件,促进了植物的扩散。于是,植物与贮食动物形成了一种协同进化关系,这种关系可能是自然界互惠关系（mutualism)的一种。影响幼苗存活和建成的因子包括种子贮蒇点的微生境、湿度、坡向、坡度、林冠盖度等。许多果食性动物吃掉果肉后,再将完好的种子反刍或排泄出来。种子经动物消化道处理后,发芽率常有所提高。     

Vegetation diversity influences endozoochoric seed dispersal by moose (Alces alces L.)

Research on moose-mediated seed dispersal is limited. However, its potential role in transferring seeds in patchy landscapes may be of great importance. In this work we examined how seasons and vegetation diversity influence the species richness and abundance of seeds dispersed endozoochorically by moose. Samples of moose faeces were collected year-round, fortnightly, from contrasting vegetation types, dominated by diverse, species-rich wetland or poor, dry pine forest. The viable seed content of dung was studied by the seedling emergence method. The mean number of emerged seedlings per 0.8 L sample and the mean number of plant species per 0.8 L sample were several times higher in the diverse wetland vegetation than in the poor pine forest vegetation. Maximum species richness and seed abundance was observed during the fructification period, and the minimum during spring. The species richness of samples did not differ between winter and the growing season, although the composition of plant species was different. The results of this study suggest that moose are efficient seed vectors, especially of grasses typical for grasslands and wetlands. The species richness and abundance of dispersed seeds coincides with the diversity of the vegetation of the animal’s habitat.     

Regeneration of Salix arbuscula and Salix lapponum within a Large Mammal Exclosure: The Impacts of Microsite and Herbivory

Over‐grazing or browsing by large herbivores may result in the loss of individual plant species or entire plant communities. Restoration schemes often involve exclusion of large mammals, but the resulting changes in vegetation may alter other important ecological processes such as regeneration, via changes in microsite availability for seed germination or increases in populations of seedling predators. Working within a large fenced area from which large mammals were excluded, we experimentally tested the effects of microsite, small herbivores, and their interactions on post‐dispersal seed and early seedling mortality of one nationally scarce (Salix arbuscula) and one nationally rare (S. lapponum) species of montane willow. Seeds were sown in three different microsites: natural vegetation, mown vegetation (mimicking grazed sward), and bare ground. Small exclosures and slug pellets were used to examine the effects of small mammal and slug predation, respectively. Survival of seedlings was monitored during the summer following planting. The presence of bare ground, rather than the absence of herbivores, was of over‐riding importance for early seedling survival and establishment. Protecting seedlings from small mammals made no difference to the levels of survival; however, protecting seedlings from slugs (Arion spp.) resulted in approximately 45% of seedlings surviving until the end of the summer compared to only 30% when seedlings were available to slugs. Although excluding large herbivores may increase seed production of existing individuals, the impacts of changes to plant communities on processes such as regeneration need to be considered if restoration projects are to be fully successful.     

Seed dispersal of alien and native plants by vertebrate herbivores

Seed dispersal is crucial for the success and spread of alien plants. Herbivores often establish a dual relationship with plants: antagonist, through herbivory, and mutualist, through seed dispersal. By consuming plants, herbivores may disperse large amounts of seeds, and can facilitate the spread of alien plants. However, seed dispersal of alien plants by herbivores has been largely uninvestigated. I studied factors associated with dispersal of alien and native seeds by the three most important vertebrate herbivores in SW Australia: emus (Dromaius novaehollandia), western grey kangaroos (Macropus fuliginosus) and European rabbits (Oryctolagus cuniculus). Overall frequencies of alien and native seeds dispersed by these herbivores were determined by differences among them in (1) the plant groups they predominantly disperse, that differed in frequencies of aliens versus natives, and (2) the predominant dispersal of aliens or natives within those plant groups. Emus and kangaroos (natives) tended to disperse predominantly alien seeds within plant groups (defined by life forms, dispersal syndromes, and diaspore size), whereas rabbits (alien) tended to disperse predominantly natives. This agrees with the hypothesis that herbivores will use predominantly plants that have evolved in different areas, because of less effective defences against new enemies. Overall frequencies were consistent with this pattern in kangaroos and rabbits, but not in emus. Kangaroos dispersed mostly plant groups that were mainly aliens (herbaceous species and small and medium sized dispersal units and seeds), which together with their predominant use of aliens over natives within groups resulted in the highest overall frequency of alien seeds (73%). Rabbits were similar to kangaroos in the type of plants dispersed, but their predominant use of natives over aliens within groups contributed to an overall predominance of native seeds in their pellets (88%). Emus dispersed mostly plant groups that were mainly natives (e.g. woody species with big diaspores), resulting in low overall frequency of alien seeds (11%), despite their predominant use of aliens over natives within plant groups. Thus, the within-groups trend pointed to a facilitative role of native herbivores of plant invasions through seed dispersal, but was obscured by the different use by herbivores of plant groups with different frequency of aliens.     

Scale-dependent diversity effects of seed dispersal by a wild herbivore in fragmented grasslands

Dispersal limitation between habitat fragments is a known driver of landscape-scale biodiversity loss. In Europe, agricultural intensification during the twentieth century resulted in losses of both grassland habitat and traditional grassland seed dispersal vectors such as livestock. During the same period, populations of large wild herbivores have increased in the landscape. Usually studied in woodland ecosystems, these animals are found to disperse seeds from grasslands and other open habitats. We studied endozoochorous seed dispersal by roe deer (Capreolus capreolus) in fragmented grasslands and grassland remnants, comparing dispersed subcommunities of plant species to those in the established vegetation and the seed bank. A total of 652 seedlings of 67 species emerged from 219 samples of roe deer dung. This included many grassland species, and several local grassland specialists. Dispersal had potentially different effects on diversity at different spatial scales. Almost all sites received seeds of species not observed in the vegetation or seed bank at that site, suggesting that local diversity might not be dispersal limited. This pattern was less evident at the landscape scale, where fewer new species were introduced. Nonetheless, long-distance dispersal by large wild herbivores might still provide connectivity between fragmented habitats within a landscape in the areas in which they are active. Finally, as only a subset of the available species were found to disperse in space as well as time, the danger of future biodiversity loss might still exist in many isolated grassland habitats.     

Contrasting effects of grazing on the early stages of woody encroachment in a Neotropical savanna

Woody encroachment in savannas represents an ecological process of current global interest given its negative impact on ecosystem functioning, particularly on forage production. Traditional savanna models propose competition and niche differentiation as the main mechanisms allowing tree-grass coexistence. Demographic models, instead, propose abiotic and biotic factors as bottlenecks controlling vital rates and transitions from seeds to adult trees. The role played by domestic grazing on woody encroachment is yet controversial. Here, using a multistage tree life approach, we combine both models and evaluate the role of grazing and herbaceous vegetation on woody recruitment in a Neotropical savanna dominated by Vachellia caven, a successful and widely spread encroacher tree species. We performed three experiments to evaluate seed predation, seedling emergence and survival of V. caven by manipulating cattle grazing (grazed and ungrazed areas) and herbaceous vegetation presence (vegetated and unvegetated). Finally, we combined the results of the three experiments to estimate the probability of plant recruitment across these experimental factors. Grazing decreased seed predation by half, did not modify seedling emergence and decreased seedling survival. Herbaceous vegetation did not affect seed predation nor seedling emergence rate, but increased seedling survival. Overall, the net effect of grazing on V. caven recruitment was neutral since the increase in seed availability due to the reduction in seed predation rate was compensated by the negative effect of grazing on seedling survival. Our analysis revealed that cattle grazing and herbaceous vegetation had contrasting effects on the seed and seedling life stages. We propose that in order to restrain the early stages of encroachment, cattle grazing pressure could be managed following the seasonality of demographic tree transitions. Through rotational grazing amongst paddocks, stocking rates could be relaxed during the primary dispersal stage to maximize granivory, and then increased to enhance the chance of seedling consumption and trampling.     

Do plant-community-based grazing regimes lead to epizoochorous dispersal of high proportions of target species?

The contribution of large-herbivore epizoochory to the transfer of seeds within and between areas is thought to be significant. But often seeds of ubiquitous species are dispersed, which may enhance ruderalization processes. In order to study the dispersal of target species by sheep, we employed a community-based grazing approach followed by intra- and inter-area sheep transfers (maximum transfer distance 3 km). In case of inter-area transfers, well-developed target communities of an open inland sand ecosystem are used as “source”, linked to less-developed sand habitats (“sink”) via sheep. Also other factors determining which species become dispersed under field conditions were tested: seed surface structure, seed mass, plant seed-releasing height and animal behaviour. Finally the influence of animal movement on seed detachment and the actual arrival of seeds within a “sink” were studied.

Sheep transfers resulted in the dispersal of 56 seed species, dominated by Red List (seven species) and other target species. Quantitatively, most transported seeds belonged to target species, whereas graminoid competitors were highly under-represented. Morphological traits enhance the attachment probability regardless of seed mass. But for seeds without these epizoochory-facilitating traits, mass seems to affect attachment negatively. Plant height affected the number of species present in sheep coats but not the seed quantities. Probably certain species in the vegetation produced large numbers of seeds, e.g. low-growing Medicago minima with seed surface structures and high-growing species Verbascum phlomoides without seed surface structures. Also, although transfer half-times were three times lower than grazing half-times, naturally attached Stipa capillata and Agrimonia procera seeds showed no significant detachment rates during transfer, whereas considerable losses were found during grazing. Other 3-km sheep transfers did not result in significant losses of either epizoochorously transported seed or species quantities. Our study shows that community-based grazing can lead to the dispersal of especially target species. Besides that, different habitat fragments can be connected to each other via sheep without significant seed losses along the way.     

Seed dispersal in the dung of large herbivores: implications for restoration of Renosterveld shrubland old fields

Species-rich, winter-rainfall, microphyllous Renosterveld vegetation in the Western Cape Province of South Africa has largely been transformed for production of wheat and wine. Remaining fragments thus have high conservation value. Abandoned old fields adjacent to natural vegetation fragments could potentially be restored as corridors and habitat for indigenous flora and fauna. We hypothesised that indigenous antelope maintained in a matrix of natural vegetation and abandoned field could play a role in restoration of Renoserveld via seed dispersal.We collected dung of indigenous ungulates in an abandoned field at various distances from natural Renosterveld vegetation, in order to assess the potential of large herbivores to contribute to restoration of plant diversity through seed dispersal. Emerged seedlings from the collected dung represented 29 forb, 13 grass, four sedge, four geophyte and one shrub species. The most abundant emerging seedlings were lawn grass Cynodon dactylon (38%), alien pasture grasses (31%) and indigenous geophyte Romulea rosea (12%). Whereas seeds of annual forbs and grasses were dispersed, only one shrub species was dispersed at very low density. We concluded that large herbivores could retard the rate of recovery of Renosterveld vegetation because viable seeds of herbaceous plants, particularly alien annual grasses and lawn-grasses were more abundant in the dung than the shrub, geophyte or perennial tussock grass species that characterise this vegetation type.     

Seed dispersal in red deer (Cervus elaphus L.) dung and its potential importance for vegetation dynamics in subalpine grasslands

Free-ranging large herbivores can influence vegetation dynamics through seed dispersal within and among habitats. We investigated the content of germinable seeds in the dung (endozoochory) of red deer (Cervus elaphus L.), the most ubiquitous wild ungulate throughout the European Alps, and compared the results with the species composition of the vegetation type in which the dung was dropped. The study was conducted in the subalpine zone of the Swiss National Park and included the three most important vegetation types for red deer: (i) intensively grazed short-grass vegetation, (ii) less intensively grazed tall-grass vegetation, and (iii) adjacent conifer forest understory vegetation. Seeds of 47 species, mostly from small-seeded herbaceous species, were recorded in dung samples with three species accounting for 65% of germinated seeds. Our results confirmed the hypotheses that (H1) small-seeded species were more likely to occur in red deer dung than larger-seeded species, though seed size was unrelated to seed density, (H2) red deer dung contained mostly seeds from short-grass vegetation, with seed species composition in dung collected from any vegetation type being most similar to species composition of relevés from short-grass vegetation, and (H3) seeds were less likely to be dispersed between vegetation types than within vegetation types, with dung dropped in short-grass vegetation having a different species composition and containing over twice as many seeds as dung dropped in the other two vegetation types. These results collectively support the hypothesis that red deer endozoochory contributes to maintaining short-grass vegetation, the favoured grazing sites of hinds in the Swiss National Park, by increasing propagule pressure of seeds from herbaceous forage species adapted to endozoochory relative to other species and especially those from later stages of secondary succession.     

Comparison of three seed trap types in a chalk grassland: toward a standardised protocol

In a chalk grassland in north-western France, vegetation and seed rain were studied along two transects. We compared the efficiency of three types of seed traps (funnel traps, sticky traps, pots exposed in the field) to estimate the annual seed rain and to reveal various processes involved in plant community regeneration. Data were analysed to compare seed density, species richness and composition across seed traps and vegetation. Geostatistical analyses (semivariograms. were used to detect possible autocorrelation and to examine patterns of spatial variation in seed rain and vegetation. The results show that (1) funnel traps are most efficient (56 species, 8079 seeds.m^–2). (2) Each type of seed traps brings different information about the processes involved in seed dispersal and seedling establishment. Sticky traps help to understand import and export of seeds in a community through anemochory. Funnel traps may provide a measure of the auto-regeneration capacity of the vegetation through its local seed production. Pot traps integrate various processes involved between seed dispersal and seedling emergence. (3.) The exposition to environmental conditions generates marked spatial patterns in species richness measured in pots and in vegetation, selecting species able to survive. Pot traps indicate that numerous species producing seeds in standing vegetation are unable to establish in the field through seedling recruitment. Our study emphasizes the need of using different types of seed traps and spatial sampling configurations to assess the regenerative potential of standing vegetation and the various mechanisms involved in seed dispersal. A standardised protocol for seed rain sampling was finally developed.     

Fire season and intensity affect shrub recruitment in temperate sclerophyllous woodlands

The season in which a fire occurs may regulate plant seedling recruitment because of: (1) the interaction of season and intensity of fire and the temperature requirements for seed release, germination and growth; (2) post-fire rainfall and temperature patterns affecting germination; (3) the interaction of post-fire germination conditions and competition from surrounding vegetation; and (4) the interaction of post-fire germination conditions and seed predators and/or seedling herbivores. This study examined the effects of different fire intensities and fire seasons on the emergence and survival of shrubs representing a range of fire response syndromes from a summer rainfall cool climate region. Replicated experimental burns were conducted in two seasons (spring and autumn) in 2 consecutive years and fuel loads were increased to examine the effects of fire intensity (low intensity and moderate intensity). Post-fire watering treatments partitioned the effects of seasonal temperature from soil moisture. Higher intensity fires resulted in enhanced seedling emergence for hard-seeded species but rarely influenced survival. Spring fires enhanced seedling emergence across all functional groups. Reduced autumn recruitment was related to seasonal temperature inhibiting germination rather than a lack of soil moisture or competition. In Mediterranean-type climate regions, seedling emergence has been related to post-fire rainfall and exposure of seeds to seed predators. We think a similar model may operate in temperate summer rainfall regions where cold-induced dormancy over winter exposes seeds to predators for a longer time and subsequently results in recruitment failure. Our results support the theory that the effect of fire season is more predictable where there are strong seasonal patterns in climate. In this study seasonal temperature rather than rainfall appears to be more influential.     

Plant traits: Their role in the regeneration of alpine plant communities in sub‐arctic Finland

Abstract. Question: How do the relative frequencies of plant traits (clonality, growth form, seed weight, diaspore morphology) vary during the life cycle and how does this affect regeneration? Location: Alpine meadow and heath communities at Kilpisjärvi, sub‐Arctic Finland. Methods: Control plots and three treatments were used to measure relative species abundances for five life cycle stages: standing vegetation, seed rain, seed bank and seedlings emerging in gaps and in closed vegetation. Results: The relative frequencies of plant traits varied between the life cycle stages. The meadows were dominated by weakly clonal herbs, small or intermediate seeds and unappendaged diaspores, while the heaths were dominated by clonal dwarf shrubs, small seeds and fleshy fruits. In the meadows, species with small seeds dominated during the seed rain and in the seedling stage in gaps, while species with intermediate seeds dominated the seed bank and the seedling stage in closed vegetation. Species with unappendaged diaspores dominated throughout the life cycle. In the heaths, seed bank and seedling stage were practically absent. Conclusions: The observed differences in plant trait spectra between life cycle stages indicate that important environmental factors differ among the stages. Small seeds are advantageous for dispersal, whereas intermediate seeds have a greater probability of germinating and establishing in closed vegetation. Appendages facilitate dispersal, whereas unappendaged diaspores favour seed burial. Although the plant growth form spectrum largely reflects environmental constraints during the regeneration cycle, information on seed weight and diaspore morphology improves our knowledge of the relative importance of morphological adaptations of sexual structures in different stages during the life cycle.     

Endozoochorous seed dispersal by cattle and horse in a spatially heterogeneous landscape

Seed dispersal has become an important issue in plant ecology and restoration management. In this paper we examined dung germinating seed content and seed deposition patterns of horses (Shetland and Konik breeds) and Scottish Highland cattle grazing two coastal dune nature reserves. Two times 2.5 l of fresh dung from each type of herbivore were collected during seven sessions in the main fruiting season. Dung samples were placed under greenhouse conditions after drying and cooling. Animal defecation patterns were derived from a study of herbivore activities during 6 h observation sessions 8 times a month. One hundred and seventeen plant species i.e. 27% of all species occurring in the study area, were recorded as seedlings emerging from the dung samples. The most abundantly and frequently recorded plant species were Urtica dioica, Juncus spp. and different species of Poaceae and Caryophyllaceae. In general seedling density is high (1158 seedlings/dung sample). Seedling density and species richness were further analysed in order to detect temporal variability and possible animal and site related characteristics. Dung deposition patterns reflect a non-random use of habitats and hence a non-random seed deposition among habitats. Calculated seed deposition per square meter ranged from a few (<10 germinating seeds) to more than 100 in the most frequently selected habitats. From the herbivores’ selective habitat use and their estimated mean retention time we can further assume their ability for inter-habitat endozoochorous seed dispersal. This characteristic of large herbivores is further discussed in the light of nature management and restoration.Indra Lamoot is an aspirant of FWO-Flanders.     

Role of plant functional traits in determining vegetation composition of abandoned grazing land in north‐eastern Victoria,Australia

Question: In the Northern Hemisphere, species with dispersal limitations are typically absent from secondary forests. In Australia, little is known about dispersal mechanisms and other traits that drive species composition within post‐agricultural, secondary forest. We asked whether mode of seed dispersal, nutrient uptake strategy, fire response, and life form in extant vegetation differ according to land‐use history. We also asked whether functional traits of Australian species that confer tolerance to grazing and re‐colonisation potential differ from those in the Northern Hemisphere. Location: Delatite Peninsula, NE Victoria, Australia. Methods: The vegetation of primary and secondary forests was surveyed using a paired‐plot design. Eight traits were measured for all species recorded. ANOSIM tests and Non‐metric Multi‐dimensional Scaling were used to test differences in the abundance of plant attributes between land‐use types. Results: Land‐use history had a significant effect on vegetation composition. Specific leaf area (SLA) proved to be the best predictor of response to land‐use change. Primary forest species were typically myrmecochorous phanerophytes with low SLA. In the secondary forest, species were typically therophytes with epizoochorous dispersal and high SLA. Conclusions: The attributes of species in secondary forests provide tolerance to grazing suggesting that disturbance caused by past grazing activity determined the composition of these forests. Myrmecochores were rare in secondary forests, suggesting that species had failed to re‐colonise due to dispersal limitations. Functional traits that resulted in species loss through disturbance and prevented re‐colonisation were different to those in the Northern Hemisphere and were attributable to the sclerophyllous nature of the primary forest.     

花楸树种子散布、萌发与种群天然更新的关系

花楸树是我国东北林区重要的非木质资源树种,其实生天然更新不良.本文通过研究花楸树种子散布、土壤种子库及种子萌发出土过程,分析花楸树实生天然更新的影响因素.结果表明：自然散落的花楸树果实96.1%分布于母株2 m范围内,凋落物层和土壤表层（0～2 cm）的种子数占土壤种子库总数的97.0%;不同季节花楸树土壤种子库种子数量差别很大,当年11月上旬种子数量最多,达(257.7±69.2)粒·m^-2;翌年7月下旬种子数量最少,仅为(2.9±2.9)粒·m^-2;温度不是花楸树种子萌发出土过程的限制因子,0 ℃～5 ℃时幼苗出苗率达(67.5±6.6)%,但对其出苗速率影响显著.土壤含水量为50%时,花楸树出苗率最高,达(74.7±4.2)%;含水量为60%时,幼苗死亡率最低,为(32.6±0.6)%.花楸树种子的散布格局和土壤种子库的时空分布格局影响种子的萌发出土过程,进而影响其种群的天然更新.