Changed Clonal Growth Form Induced by Sand Burial Facilitates the Acclimation of Carex brevicuspis to Competition

Both competition and burial are important factors that influence plant growth and structuring plant communities. Competition intensity may decline with increased burial stress. However, experimental evidence is scarce. The aim of this study was to elucidate the role of burial stress in influencing plant competition by investigating biomass accumulation, biomass allocation, and clonal growth performance of Carex brevicuspis, one of the dominant species in the Dongting Lake wetland in China. The experiment was conducted with two typical wetland species, C. brevicuspis (target plant) and Polygonum hydropiper (neighbor plant), in a target-neighbor design containing three densities (0, 199, and 398 neighbor plants m-2) and two burial depths (0 and 12 cm). The biomass accumulation of C. brevicuspis decreased with increment of P. hydropiper density in the 0 cm burial treatment. However, in the 12 cm burial treatment, biomass accumulation of C. brevicuspis did not change under medium and high P. hydropiper densities. The relative neighbor effect index (RNE) increased with enhancement of P. hydropiper density but decreased with increasing burial depth. The shoot mass fraction decreased with P. hydropiper density in the 12 cm burial treatments, but the root mass fraction was only affected by burial depth. However, the rhizome mass fraction increased with both P. hydropiper density and burial depth. The number of ramets decreased with increasing P. hydropiper density. With increasing burial depth and density, the proportion of spreading ramets increased from 34.23% to 80.44%, whereas that of clumping ramets decreased from 65.77% to 19.56%. Moreover, increased P. hydropiper density and burial depth led to greater spacer length. These data indicate that the competitive effect of P. hydropiper on C. brevicuspis was reduced by sand burial, which was reflected by different patterns of biomass accumulation and RNE at the two burial depth treatments. A change from a phalanx to a guerrilla growth form and spacer elongation induced by sand burial helped C. brevicuspis to acclimate to competition.     

The sediment burial depth and salinity control the early developments of Suaeda salsa in the Yellow River Delta

Sediment deposition is a common phenomenon in the estuary area. Pot control experiments were conducted to evaluate the interaction effects of sediment burial depth and salt stress on the seed germination and early seedling growth of Suaeda salsa (L.) Pall., an pioneer species of tidal wetland near the Yellow River Delta. The results showed that the percentage of seedling emergence, seedling emergence rate, seedling height, branch number, shoot biomass and root biomass were all significantly affected by salt stress and sediment burial depth. While the interaction of salt and burial depth significantly influenced the branch number, leaf biomass, shoot biomass and total plant biomass. Only 5 cm burial depth without salt stress should 6.25 ± 3.61% seedlings emergence. With the increasing of sediment burial depth and salt stress, percentage of seedling emergence, seedling emergence rate and plant height decreased significantly. However, under the salt treatment of 0 and 1%, the branch number increased dramatically with the increasing of sediment burial depth from 0 to 3 cm. The ratio of leaf to total biomass increased with increasing of burial depth, on the contrary, the ratio of root to total biomass decreased. 0–1 cm sediment burial depth was proved the suitable depths for seed germination of S. salsa in the coastal wetland of the Yellow River Delta. Our findings contribute to a better understanding of how to improve the seedling establishment of S. salsa under the dynamic changes of sediment deposition and salinity in the coastal wetland of the Yellow River Delta.     

Regeneration Capacity of Small Clonal Fragments of the Invasive Mikania micrantha H.B.K.: Effects of Burial Depth and Stolon Internode Length

The perennial stoloniferous herbaceous vine Mikania micrantha H.B.K. is among the most noxious exotic invaders in China and the world. Disturbance can fragment stolons of M. micrantha and disperse these fragments over long distances or bury them in soils at different depths. To test their regeneration capacity, single-node stolon fragments with stolon internode lengths of 0, 3, 6 and 12 cm were buried in soil at 0, 2, 5 and 8 cm depths, respectively. The fragments were growing for nine weeks, and their emergence status, growth and morphological traits were measured. The results indicated that increasing burial depth significantly decreased survival rate and increased the emergence time of the M. micrantha plants. At an 8-cm burial depth, very few fragments (2.19%) emerged and survived. Burial did not affect the total biomass and root to shoot ratio of the surviving M. micrantha plants that emerged from the 0- and 2-cm burial depths. Increasing internode length significantly increased survival rate and growth measures, but there was no interaction effect with burial depth for any traits measured. These results suggest that M. micrantha can regenerate from buried stolon fragments, and thus, disturbance may contribute to the spread of this exotic invader. Any human activities producing stolon fragments or facilitating dispersal should be avoided.     

Buried Alive: The Behavioural Response of the Mussels,Modiolus modiolus and Mytilus edulis to Sudden Burial by Sediment

Sedimentation in the sea occurs through natural processes, such as wave and tidal action, which can be exacerbated during storms and floods. Changes in terrestrial land use, marine aggregate extraction, dredging, drilling and mining are known to result in substantial sediment deposition. Research suggests that deposition will also occur due to the modern development of marine renewable energy. The response to individual burial under three depths of sediment, three sediment fractions and five burial durations was investigated in two mussel species, Modiolus modiolus and Mytilus edulis in specialist mesocosms. Both mussel species showed substantial mortality, which increased with duration of burial and burial by finer sediment fractions. M. modiolus was better able to survive short periods of burial than M. edulis, but at longer durations mortality was more pronounced. No mortality was observed in M. modiolus in burial durations of eight days or less but by 16 days of burial, over 50% cumulative mortality occurred. Under variable temperature regimes, M. edulis mortality increased from 20% at 8°C to over 60% at 14.5 and 20°C. Only M. edulis was able to emerge from burial, facilitated by increased byssus production, laid mostly on vertical surfaces but also on sediment particles. Emergence was higher from coarse sediment and shallow burials. Byssus production in M. edulis was not related to the condition index of the mussels. Results suggest that even marginal burial would result in mortality and be more pronounced in warm summer periods. Our results suggest that in the event of burial, adult M. modiolus would not be able to emerge from burial unless local hydrodynamics assist, whereas a small proportion of M. edulis may regain contact with the sediment water interface. The physiological stress resulting in mortality, contribution of local hydrodynamics to survival and other ecological pressures such as mussels existing in aggregations, are discussed.     

Assessment of Regeneration Potential in the Clonal Macrophyte Miscanthus sacchariflorus (Poaceae) after Burial Disturbance Based on Bud Bank Size and Sprouting Capacity

The demography of the bud bank and its sprouting capacity are important for understanding the population dynamics of clonal plants and their potential responses to disturbances. To this end, we investigated the size and composition of the bud bank of Miscanthus sacchariflorus (Maxim.) Hack. immediately after flooding (November), in winter (January), in spring (March), and before flooding (May) in the wetlands of Dongting Lake. We then examined the sprouting capacity of axillary buds after sediment burial at 0, 5, 10, 15, and 20 cm. Total bud density of M. sacchariflorus ranged from 2524 buds m^-2 in November to 4293 buds m^-2 in March. Rhizome segments with inactive axillary buds, which represented the majority of the bud population (88.7% in November, 93.3% in May), did not sprout during the 140 days of the experiment (n = 250). The sprouting ratio was the highest for active axillary buds buried at 0 cm (64%) and decreased when buried at 10–20 cm (34%–40%). Due to the large number of active axillary buds in the bud bank (211–277 buds m^-2 from November to the following March), M. sacchariflorus could completely replace its aboveground shoot population, except in May (142 buds m^-2). Increasing burial depth delayed bud emergence and reduced the growth period of shoots; however, burial depth did not affect the resulting plant height and only reduced the accumulated biomass at 20 cm. Therefore, the belowground bud bank and its strong sprouting capacity are important factors in the maintenance of local populations and colonization of new habitats for M. sacchariflorus after burial disturbances. The present methodology, which combined measurements of bud bank demography and sprouting capacity, may reflect the regeneration potential of clonal plants after burial disturbances.     

Vertical structure of seed banks and the impact of depth of burial on recruitment in two temporary marshes

The structure of the seed bank (including Chara oospores), in relation to depth within the sediment and disturbance, was studied in two Rhône delta temporary marshes for two years. The seeds of all species were concentrated in the top 2 cm of sediment with very low numbers beeing found below 4 cm. When an exclosure eliminated disturbances of the sediment by animals, the vertical repartition of seeds at site 2 was more pronounced than outside the exclosure.In experiment 1, the emergence capacity of seeds from different depths and buried under layers of sterile equivalent to those in the field was measured. Depending of the species, 22 to 98% of the seeds germinated from unburied seeds in the top 2 cm. Only 1% of the oospores of Chara (from site 2) at 2 to 4 cm depth in the sediment emerged.In experiment 2, surface seed bank samples were placed under 0, 2 or 4 cm sterile sediment depth. The samples contained numerous recent seeds and the emergence percentage reached 41% (for Ruppia maritima). Only the seeds of Zannichellia spp failed to germinate from a depth of 2 cm or more. The emergence percentage from 2 cm depth or more was always lower than at the surface. These experiments showed that both burial and ageing of seeds decrease germination capacity.The majority of the active seeds located at the surface germinate when the marsh is flooded. Seeds located between 2 and 4 cm can be brought back to the surface by disturbances and play the role of a reserve involved in maintenance of populations that go without seed production for one or some years.     

EFFECTS OF BURIAL BY SAND ON SEED GERMINATION AND SEEDLING EMERGENCE OF FOUR DUNE SPECIES

On the beach strand, seedlings of Cakile edentula, Elymus canadensis, and Corispermum hyssopifolium emerged from mean depths of 3.4, 3.5 and 3.0 cm, respectively. The frequency distribution of the depth of seedling emergence was 1) significantly leptokurtic for C. edentula and slightly platykurtic (not significant) for C. hyssopifolium and E. canadensis, and 2) significantly skewed to the right for C. edentula and E. canadensis but not for C. hyssopifolium. The total germination was not influenced by the burial of seeds at 2, 4, 6, 8, 10 and 12 cm depths except in Ammophila breviligulata in which the germination decreased with increasing depth of burial. The rate of emergence and total emergence decreased with increased sowing depth for all four plant species. Species with larger seeds emerged from deeper burial treatments than those with small seeds. The order of ED₅₀ (the planting depth from which 50% of the seedlings emerged) and ED_max (the maximum depth from which a seedling emerged) was C. edentula (upper seeds) > E. canadensis > C. edentula (lower seeds) ≖ C. hyssopifolium > A. breviligulata and it coincided with weight per seed.     

Sand burial effects on seed germination, seedling emergence and establishment of Panicum virgatum

Studies in the field and in a greenhouse were conducted to examine the effects of sand burial on seed germination, seedling emergence and establishment of Panicum virgatum L. on the foredunes of Lake Erie. Under natural conditions, the seedlings emerged from sand burial depths ranging from 0 to 11 cm, with a mean ± SD of 4.73 ± 1.82 cm. The frequency distribution of the depth of emergence of seedlings in the field was significantly skewed to the right and platykurtic. In the greenhouse, some seedlings emerged from a burial depth of as much as 16 cm. Although percent germination of seeds was not affected by sand burial, the percent emergence and the rate of emergence of seedlings were significantly reduced by excessive sand burial. Seedling mortality was found only among seedlings that emerged from sand burial depths of 10 cm or more. In the field, all the seedlings established in one growing season had originally emerged from sand burial depths of less than 12 cm. Within this burial range, seedlings from shallower burial depths had lower chances of establishment than expected, whereas those from deeper burial depths had higher probabilities of establishment than expected.     

Extraction and characterization of volatile compounds and fatty acids from red and green macroalgae from the Romanian Black Sea in order to obtain valuable bioadditives and biopreservatives

Three species of macroalgae, Ceramium virgatum (Rhodophyta), Ulva intestinalis, and Cladophora vagabunda (Chlorophyta), harvested from the Romanian Black Sea coast, were studied as sources of valuable compounds that could be used as additives and biopreservatives. Volatile compounds including hexanal (11.2 %), octane (9.8 %), nonanal (7.0 %), octanal (6.7 %), 2,5,5-trimethyl-2-hexene (4.7 %), 3-hexen-2-one (4 %), and o-cymene (3.6 %) were identified as the major components in the biomass extract of C. vagabunda. In C. virgatum, the major volatile components were 3-hexen-2-one (27.9 %), acetone (12.4 %), hexanal (3.4 %), and o-cymene (2.7 %). The major volatile compounds of U. intestinalis were hexanal (14.6 %), trichloromethane (7.3 %), nonanal (5.6 %), 3-hexen-2-one (5.3 %), and octanal (3.1 %). Some of these compounds have industrial applications as additives in the food, pharmaceutical, or cosmetics industries. The U. intestinalis extract had a greater content of mono- and polyunsaturated fatty acids around 46.0 % as compared with 42.0 % for C. vagabunda and 31.9 % for C. virgatum. The most abundant fatty acids were palmitic acid (C16:0), arachidonic acid (C20:4n-6), and oleic acid (C18:1ω-9cis). The antimicrobial effect of fatty acid extracts was tested against four pathogenic bacteria. The minimum inhibitory concentrations of C. vagabunda, C. virgatum, and U. intestinalis fatty acids extracts were 1.8, 3.8, and 3.8 mg mL^?1, respectively, for all bacterial strains. This study can help the efforts of finding new, value-added uses for natural marine resources.     

沙埋对六种沙生植物种子萌发和幼苗出土的影响

研究了沙埋对科尔沁沙地6种优势植物的种子萌发和幼苗出土的影响．进行0．2、4、6、8、10和12cm等7个深度沙埋处理．结果表明,在不同沙埋处理时,沙蓬萌发差异显著。而差不嘎蒿2锄埋深与其他埋深的发芽差异显著,其他4种植物0cm埋深与其他埋深的发芽差异显著;沙埋对所有植物幼苗出土均有显著影响,埋深增加,出苗率减小;繁殖体大的物种与繁殖体小的物种相比,能从更深沙层中出苗,幼苗出土最大深度排序为苦参>东北木蓼≥沙蓬>山竹子>雾冰藜>差不嘎蒿．     

Soil nitrification and foliar δ15N declined with stand age in trembling aspen and jack pine forests in northern Alberta,Canada

Aims

Seed germination and seedling emergence are vulnerable to water stress in arid environments. When precipitation is low and unpredictable during the early growing season, seeds near the sand surface often suffer from hydration/dehydration during germination. We investigated the responses of seedling emergence and survival of a sand dune grass with high sand stabilization value to amount and frequency of precipitation and depth of burial in sand.

Methods

Effects of amount and frequency of precipitation, burial and hydration/dehydration on seedling emergence of Leymus secalinus, were examined using standard procedures.

Results

Seedling emergence was affected by amount and frequency of monthly precipitation and depth of burial, and it decreased as precipitation frequency decreased with same amount of precipitation. Highest emergence percentage was obtained with 100 or 150 mm precipitation at 1–4 cm depth. Hydration/dehydration treatments decreased germination and increased dormancy percentage. Young seedlings with root lengths of 0–1 mm desiccated up to 30 days revived after rehydration.

Conclusions

Seedling emergence of L. secalinus is adapted to 150 mm monthly precipitation with frequency of 10–30 times per month, 1–4 cm burial depth and dehydration interval of 1–2 days. Alteration of amount and/or frequency of precipitation caused by climate change could markedly affect seedling emergence and population regeneration of this species.     

Effects of sediment burial disturbance on the vegetative propagation of Phalaris arundinacea with different shoot statuses

Shoot status, such as orientation and connection to the root system, and sediment burial depth after flooding disturbances have important ecological consequences on the post-flooding growth and vegetative reproduction of emergent macrophytes in wetlands. In the present study, we investigated the effect of shoot status (vertical, prostrate, or detached) and sediment burial depth (0.5 or 10 cm) on biomass accumulation and propagule production in Phalaris arundinacea (Poaceae) using an outdoor mesocosm system. In contrast to our prediction that shallow sediment burial would activate the axillary buds on prostrate shoots and regenerate more ramets, significantly fewer new ramets, rhizomes, buds, and biomass accumulation formed in P. arundinacea as the shoots changed from vertical to prostrate. Deeper sediment burial resulted in lower biomass and propagule production in plants with prostrate shoots, whereas vertical shoots increased the number of ramets. P arundinacea with detached shoots also produced a number of propagules after shallow or deep sediment burial, which might be important for the long-distance dispersal of P. arundinacea. These results suggest that P. arundinacea is a potentially invasive species in many lacustrine wetlands, particularly those with a high sedimentation rate, due to its high capacity for vegetative propagation.     

Effects of Planting Depth,Sediment Grain Size,and Nutrients on Ruppia maritima and Potamogeton perfoliatus Seedling Emergence and Growth

Protocols are now available for seed harvest, storage and germination of several mesohaline and polyhaline species; however, low seedling survival rates point to the need for an increased understanding of factors affecting seedling establishment. Depth of seed burial in sediments and initial seedling growth rates are shown to be limiting factors for photosynthetic competency of Ruppia maritima and Potamogeton perfoliatus. Seedling emergence is inversely proportional to planting depth on sediments ranging in grain size from coarse sands (850 μm) to silt (63 μm). Less than 6% of the seeds of either species emerged when buried to a depth of 3 cm in test sediments. Germination was greatest for seeds placed on the surface of sediments; however, these seedlings were subject to displacement because of the weak and fragile roots produced during early growth. Fine sediments may be more favorable for R. maritima seedling establishment, because seedling emergence and height decreased with increasing sediment grain size. Potamogeton perfoliatus seedlings seem to be more tolerant of a wider range of sediment grain sizes than R. maritima as indicated by the lack of an effect of sediment grain size on P. perfoliatus seed emergence, seedling height, and biomass. Increasing nutrients stimulated seedlings of both species; however, even at the highest concentrations tested, growth, as determined by shoot elongation and leaf and root formation, slowed within 7–10 days. This suggests factors other than mineral nutrients and light limit growth or that growth shifts from aboveground biomass production to belowground vegetative spread.     

Environmental variability at the phosphoglucose isomerase locus in the genus Chlamys

Two geographically and reproductively isolated populations each of Chlamys opercularis and of Chlamys varia are compared with respect to polymorphism at the phosphoglucose isomerase (PGI) locus. One population of C. varia is further sub-divided into sub-littoral and inter-tidal samples. From the results it is inferred that PGI is a dimeric molecule, controlled by five alleles in C. varia and by at least four alleles in C. opercularis. acting at a single locus. The alleles recognised for C. opercularis have identical electrophoretic mobility as four of those seen in C. varia. The two populations of C. varia are remarkably similar, as were their habitats. However, the sub-littoral sample does show a lesser degree of homozygosity than the inter-tidal sample of the same population. The two populations of C. opercularis differ significantly and represent two separate and identifiable ‘races’. C. varia exhibits a much greater degree of genetic variability than the deep sub-littoral species, C. opercularis indicating that a more stable environment regulates a more monomorphic species.     

埋深和播种密度对豚草种子出苗及幼苗生长的影响

豚草是一种全球性的恶性入侵杂草,给我国生物多样性及经济发展造成了巨大威胁。为研究豚草种子出苗和幼苗生长的影响因素,采用盆栽实验分析了种子大小（L、M、S）与埋深（2、4 cm和6 cm）或播种密度（2、4粒/盆和8粒/盆）对豚草（Ambrosia artemisiifolia）种子的出苗和幼苗生长的影响。研究结果表明,埋深对豚草种子出苗的影响高于播种密度及种子大小的影响,较浅的埋深有利于豚草种子出苗;出苗率在不同播种密度下均具有较高水平,达到67.9%-100%,这种高出苗率是豚草在不同生境成功定植的原因之一。豚草的幼苗生长受埋深或播种密度的影响大于种子大小的影响,且小种子更易受埋深或播种密度的影响。种子大小显著影响豚草幼苗的株高和基径（P<0.05）,总体上较大种子的株高和基径高于小种子,此外更小的种子会将生物量更多的分配给根以促进幼苗的生长。幼苗的株高和基径在较浅的埋深下更高,而豚草幼苗的单株生物量、单株地上和地下生物量随埋深的增加而增加。播种密度的增加会加剧豚草幼苗之间对水分、营养、光照等资源的竞争,导致其单株地上、地下及总生物量显著降低（P<0.05）。研究发现豚草在浅埋深、低密度生境中更容易入侵成功,因此可以通过对土壤进行深翻,采取替代控制,种植竞争能力强的本地植物等手段有效管理和防治豚草。     

Habitat choice and seed–seedling conflict of Spartina alterniflora on the coast of China

To elucidate the seed–seedling conflict and the process of habitat choices during the expansion of S. alterniflora, densities of seeds and seedlings in three different habitats, foreland, Spartina meadow, and canopy gap patch, were measured. Statistical analyses of these measurements were performed to investigate the interaction between seeds or seedlings and environmental factors. Also, the process of habitat choice during the expansion of S. alterniflora was explored. The results show that, in the upper soil seed bank (0–5 cm), both the ratio of germinated seeds and the ratio of survival seedlings to total seeds do not differ significantly among the three habitats. However, in the lower soil seed bank (5–10 cm), these ratios differ significantly, suggesting the seed–seedling conflict of S. alterniflora generally occurs in the lower soil seed bank. The remarkable conflict occurs in the meadow habitat. Greenhouse experiments indicate that the germination rate decreases significantly and the mortality of pre-emerged seedlings increases significantly with increasing burial depth. The maximal burial depth of emerged seedlings varies with sediment types. Comparisons of burial depth effects on seedling height, mesocotyl length, coleoptile length, and root length show that the major responses of S. alterniflora pre-emerged seedlings to the burial treatments are the elongation of coleoptiles and mesocotyls, which favor seedling survival by enhancing aeration and accelerating emergence. These results suggest that burial treatment is a key selection factor, which leads to the seed–seedling conflict in recruitment of S. alterniflora population, and directly affects the expansion rate and the area infected by S. alterniflora. Handling editor: S. M. Thomaz Ziwang Deng: co-first author.     

Effects of sand burial depth and seed mass on seedling emergence and growth of Nitraria sphaerocarpa

A greenhouse experiment was conducted to test the effects of sand burial depth and seed mass on seedling emergence and growth of Nitraria sphaerocarpa. Seeds of Nitraria sphaerocarpa were sorted into three size-classes (large, medium, small) and artificially buried at 0, 1, 2, 3, 4, 5 and 6 cm depths in plastic pots filled with unsterilized sand. In the seven treatments, the percent emergence, seedling mass and seedling height, significantly affected by both burial depth and seed size, were highest at the optimal burial depth of 2 cm burial depth, and decreased with increasing burial depth in each seed size-class. Although seedling mass was usually greatest for large seeds and least for small seeds at each burial depth, little difference was observed in seedling height at shallow burial depths of 0–3 cm. In each seed size-class, with increasing burial depth, both root-mass ratio and aboveground stem-mass ratio decreased, while belowground stem-mass ratio increased. In each burial depth, with decreasing seed size, belowground stem-mass ratio increased, while root-mass ratio decreased.     

Aquatic plant shows flexible avoidance by escape from tuber predation by swans

Deeper burial of bulbs and tubers has been suggested as an escape against below-ground herbivory by vertebrates, but experimental evidence is lacking. As deep propagule burial can incur high costs of emergence after dormancy, burial depth may represent a trade-off between sprouting survival and herbivore avoidance. We tested whether burial depth of subterraneous tubers is a flexible trait in fennel pondweed (Potamogeton pectinatus), facing tuber predation by Bewick's swans (Cygnus columbianus bewickii) in shallow lakes in winter. In a four-year experiment involving eight exclosures, winter herbivory by swans and all vertebrate summer herbivory were excluded in a full-factorial design; we hence controlled for aboveground vertebrate herbivory in summer, possibly influencing tuber depth. Tuber depth was measured each September before swan arrival and each March before tuber sprouting. In accordance with our hypothesis, tuber depth in September decreased after excluding Bewick's swans in comparison to control plots. The summer exclosure showed an increase in tuber biomass and the number of shallow tubers, but not a significant effect on the mean burial depth of tuber mass. Our results suggest that a clonal plant like P. pectinatus can tune the tuber burial depth to predation pressure, either by phenotypic plasticity or genotype sorting, hence exhibiting flexible avoidance by escape. We suggest that a flexible propagule burial depth can be an effective herbivore avoidance strategy, which might be more widespread among tuber forming plant species than previously thought.     

Edaphic constraints on seed germination and emergence of three <Emphasis Type="Italic">Acacia</Emphasis> species for dryland restoration in Saudi Arabia

In situ edaphic factors affecting seed germination and seedling emergence of three framework species of Acacia were investigated with the intent of developing fundamental and scalable restoration capacity for Arabian dryland restoration. Direct seeding represents the most efficient means to restore vegetation at the landscape scale and this study provides insight into edaphic and ecological limitations, as well as effective protocols governing the use of native seeds for restoration in hyper-arid environments. The study was conducted in extant Acacia woodland habitat on conserved land (Thumamah Nature Park) in close proximity to Riyadh, Saudi Arabia. Broad-scale direct seeding using un- and pretreated Acacia gerrardii, A. tortilis, and A. ehrenbergiana seed, and two seed burial depths were implemented across three sites with distinct soil surface characteristics. Eight weeks post-sowing, random samples for each species × seed treatment × burial depth combination were excavated, sieved, and categorized as follows: failed to germinate, germinated but died prior to emerging, or successfully emerged. We show that germination and emergence of Acacia gerrardii, A. tortilis, and A. ehrenbergiana were driven by a three-way interaction among species, site, and seed burial depth. Treating seed with the signaling compound Moddus did not have a definitive effect, positive or negative, on any of the species investigated. Acacia gerrardii was the only species that exhibited widespread emergence, though emergence was not consistent across sites or burial depths. Germination was highest in disturbed soil (up to 69% for A. gerrardii), but very few (<2%) successfully emerged; a greater proportion of germinants in sandy soil emerged (up to 44% for A. gerrardii) even though the overall germination was less. Though species-dependent, a 2-cm sowing depth was most effective in sand; while in disturbed soil, sowing depths of 1 and 2 cm were comparable; and no germination was observed in gravelly clay soil. Sandy soil exhibited rapid water infiltration (107.6 mm min^?1), and post-sowing surface crusting was a non-factor (0.44 kg cm^?2). Disturbed soil exhibited moderate water infiltration (1.46 mm min^?1) and post-sowing surface crusting was double that of sand (0.88 kg cm^?2) and restrictive on seedling emergence. Gravelly clay exhibited extremely poor water infiltration (0.12 mm min^?1), and surface crusting was severe (4.49 kg cm^?2) and an order of magnitude greater than sand. The medium-coarse sand fraction, a key driver of the observed soil surface processes, was greatest in sand (55%) and significantly less and uniform in the disturbed (22%) and gravelly clay (22%) soils. Our findings demonstrate that soil surface characteristics and associated processes can dictate ecological processes at depths as shallow as 1–2 cm, and that soil crusts that slow water infiltration and impede seedling emergence rapidly reconstitute after disturbance; both are important considerations for restoring dryland vegetation.