Seed Removal and Predation as Factors Affecting Seed Availability of Tree Species in Degraded Habitats and Restoration Plantings in Rainforest Areas of Queensland,Australia

The post‐dispersal removal or predation of seeds of native tree species was investigated in Queensland, Australia, at degraded habitats and rainforest restoration sites where direct seeding might be used to facilitate tree regeneration (old fields or open habitats, lantana thicket, rainforest edge, and 5‐ and 10‐year‐old restoration plantings). Seed removal/predation was assessed in relation to tree seed weight and canopy density of the habitats during the wet season period. Results indicated that seed removal/predation imposes limitations on seed availability, particularly for small seeded species. In most situations, larger seeds were less removed/predated, most likely due to the more limited range of large seed consumers. The use of large, hard‐coated seeds may potentially reduce seed loss in open situations (from both seed removal and desiccation), unless large seed consumers frequent the site. Canopy cover exerted an influence on seed removal/predation, though trends varied in relation to site and the time of season. Broadcast sowing of seed under planted tree canopies at the more advanced stages of closure may in some areas result in higher seed removal/predation. Likewise, seeding in areas dominated by woody weeds may result in high seed losses to consumers such as rodents. Results suggested that undertaking direct seeding to coincide with the maximal period of fruit production may in some situations be beneficial to minimize seed loss. Overall, site context, canopy cover, and species selection appear to be important considerations when aiming to reduce loss of seeds to animal seed consumers in restoration work.     

Seed bed treatment effects on vegetation and seedling establishment in a New Zealand pasture one year after seeding with native woody species

Summary Efforts to re‐establish indigenous forests in pastoral New Zealand have increased as the value of native biodiversity has been realized. Direct seeding of woody species is preferable to transplanting, as labour and material costs are less. However, the success rate of direct seeding in pasture has been variable due to intense competition from adventive species. We initiated an experiment in pasture plots adjacent to a forest fragment where seed bed treatments (increasing in degree of disturbance from herbicide application to turf removal and topsoil removal) in combination with mulch treatments (wood chip shavings with and without forest floor organic material) were seeded with a mixture of New Zealand lowland forest species. The objective of the study was to determine if early successional plant communities, and ultimately seedling establishment, differed as a result of seed bed preparation after 1 year. Coprosma robusta (Karamu) and Kunzea ericoides (Kanuka) seedlings established on plots in significant numbers: both species were most abundant on topsoil‐removed plots where bare substrate was greatest and plant cover least. Both seed bed treatments and mulching treatments led to measurable differences in overall composition of early successional plant communities. However, absence of plant cover and low soil fertility (both associated with the topsoil‐removed treatment) were the most important factors in seedling success.     

Recovery after African Olive invasion: can a ‘bottom‐up’ approach to ecological restoration work?

African Olive (Olea europaea ssp. cuspidata) is a densely crowned evergreen small tree, native to eastern Africa that is highly invasive in areas where it has been introduced, including Hawaii and Australia. Invasion by African Olive threatens Cumberland Plain Woodland, a critically endangered grassy eucalypt woodland from western Sydney, Australia, through the formation of a dense mid‐canopy excluding the regeneration of native species. We established a 3‐year field experiment to determine the effectiveness of direct seeding and fire, as techniques for early stage restoration of a 2 ha historically cleared and degraded Cumberland Plain Woodland site after the removal of African Olive. Direct seeding was able to re‐establish a native perennial grass cover which was resistant to subsequent weed invasion and could be managed as an important first stage in woodland restoration with fire and selective herbicide. Fire was able to stimulate some germination of colonising native species from the soil seed bank after 15 years of African Olive invasion; however, germination and establishment of native shrubs from the applied seed mix was poor. We propose a ‘bottom‐up’ model of ecological restoration in such highly degraded sites that uses a combination of direct seeding and stimulation of the soil seed bank by fire, which could be applicable to other degraded grassy woodland sites and plant communities.     

Should I plant or should I sow? Restoration outcomes compared across seven riparian revegetation projects

To revegetate native plant communities, it is often cheaper to direct seed than to plant nursery‐grown stock. However, the outcomes of direct seeding can be quite variable, and it is unclear whether direct seeding or planting is more likely to facilitate the restoration of diverse plant communities. To address this question, we compared the outcomes of each method across several recent riparian revegetation projects where both direct seeding and tube‐stock planting were used. We surveyed riparian revegetation projects at seven sites within the greater Melbourne area that had been revegetated between 1 and 4 years previously. Sites were all on land previously used for agriculture or degraded public land and ranged in environmental and climatic conditions. Woody plant density, establishment of target species, species richness, species diversity (evenness) and plant heights were assessed. Direct seeding tended to result in higher plant densities and similar species richness, but lower rates of species establishment and diversity compared with planting. A median of 67% of target species established via direct seeding compared with 100% for planting, with direct seeded areas often dominated by one or two species. In general, overall revegetation outcomes were often driven by climatic and site factors, rather than revegetation method. We suggest that to achieve good restoration outcomes from revegetation in riparian areas, a bet‐hedging or combined approach using both sowing and planting may be the best strategy.     

The Effect of Timing of Rehabilitation Procedures on the Establishment of a Jarrah Forest After Bauxite Mining

The restoration of the high botanical diversity of the premining jarrah (Eucalyptus marginata) forest is a major priority of rehabilitation following bauxite mining in southwestern Australia. This study investigated the effects of different ripping, seeding, and scarifying dates on the establishment of plants from propagules stored in the topsoil and from applied seed on areas being rehabilitated after mining. Seed stored in the topsoil, rather than applied seed, was the major contributor to plant diversity. Ripping late (April) or scarifying in June significantly reduced the number of species and numbers of individual plants that established from propagules in the topsoil. Species originating from broadcast seed were most numerous when the seed was broadcast in April or after scarifying in June. Scarifying before seeding, particularly in June, increased the establishment of species from the broadcast seed. To make best use of the applied seed, without jeopardizing the establishment of species from the topsoil, pits should be ripped and sown by April. We list a number of strategies that can help maximize plant numbers and botanical diversity on rehabilitated bauxite mines, which may also be of more general application for restoring the original native vegetation on disturbed sites.     

Effectiveness of seed sowing techniques for sloped restoration sites

Practitioners are challenged with choosing among many potentially effective methods for sowing seed in ecological restoration projects to achieve sufficient native plant establishment. We tested the effectiveness of seed sowing techniques on moderate and steep slopes in a Mediterranean climate by measuring native seedling density immediately following germination, as well as plant density, recruitment success, and soil movement through the second growing season. We calculated cost effectiveness of different methods as the native plant density per dollar spent sowing seed. While all sowing techniques resulted in significant native establishment compared with unseeded controls, hydro seeding on moderate slopes was the most cost effective (native seedlings established per dollar spent). Although all steep‐sloped seeding techniques resulted in high densities of native species, all methods also resulted in significant soil loss. Shrubs preferred hand seeding followed by jute netting on steep slopes, while forbs reached greatest densities with hydro seeding on moderate slopes. Seedlings of species with heavy seeds were present in greater densities than species with lighter seeds in imprint sowing treatments. The “best” seed sowing technique varied depending on slope and metric of success (native density, species richness, shrub density, or forb density). Different combinations of slope, technique, and success metric resulted in significantly different project costs, which implies opportunities for savings given careful decision‐making relative to mitigation needs on heterogeneous landscapes. Evaluations of techniques for restoring slopes are limited, yet critical for expanding the area capable of being restored and the application of limited conservation funding.     

轻型栽培技术对稻田潜杂草群落多样性的影响

为明确轻型栽培技术对稻田潜杂草群落多样性的影响,研究了旱直播、水直播、抛秧、机插秧、麦套稻5种轻型栽培稻作模式及传统手插秧模式下稻田杂草种子库的数量特征.结果表明：旱直播稻田种子库密度显著高于其他模式,达228416粒·m^-2,麦套稻模式其次.另外,旱直播稻田莎草类杂草与麦套稻稻田阔叶类杂草种子密度显著高于其他模式的各类杂草种子.传统手插秧稻田具有最高的物种丰富度,Margalef指数达1.86; 麦套稻与水直播模式中,Shannon-Wiener指数、Gini指数、Pielou群落均匀度指数明显高于旱直播和机插秧等模式.与传统手插秧相比,各轻型栽培稻作模式具有不同的潜杂草群落优势种.为防治稻田杂草的持续危害,应轮流实施不同轻型栽培稻作模式.     

檀香的自然更新与直播造林技术

<正> 檀香(Santalum album L.)在印度的自然分布主要在温迪亚山脉(Vindhya ranye)以南,以后才被引种到奥里萨邦、中央邦、拉贾斯坦邦和北方邦的部分地区,并在那里归化,自然繁殖生长。有的学者认为,现在印度虽是檀香的主要产区,但不是檀香的原产地;檀香的原产地应是印度尼西亚的帝汶岛(Timor),大约于二千多年前引入印度,然后逸为野生状态,分布区不断扩大。 华南植物园引种檀香初步取得成功后,自1968年以来,先后在广东的海南、湛江、佛山、肇庆、韶关、汕头等地区,以及广西、云南、四川、浙江、福建等省区进行区域性试     

Direct seeding of indigenous tree and shrub species into New Zealand hill country pasture

Summary Our study aimed to examine the applicability of a native plant restoration technique involving close grazing, blanket herbicide spraying and mob stocking (to trample the seed into the soil) for establishing New Zealand native tree and shrub species into exotic hill country pasture. This approach represents an alternative to the usual spaced-planting of seedlings in the context of an indigenous vegetation restoration programme. Field-collected seed of Cabbage Tree ( Cordyline australis ), Kahikatea ( Dacrycarpus dacrydioides ), Kanuka ( Kunzea ericoides ), Karamu ( Coprosma robusta ), Kohuhu ( Pittosporum tenuifolium ), Koromiko ( Hebe stricta ), and Manuka ( Leptospermum scoparium ) were germination tested in the laboratory, and broadcast sown in two field experiments in spring 2001 and autumn 2002. The spring-sown experiment tested the effect of mob stocking and the autumn-sown experiment tested the effect of mob stocking and sowing rate. Laboratory germination varied widely among species (0–88%). In the field, the two shrubs, Koromiko and Karamu, established densities of up to 5 and 1.2 plants/m², respectively, after 2.5 years. Autumn emergence for these two species strongly related to sowing rate. Three tree species, Cabbage Tree, Kahikatea and Manuka, emerged in the field but did not survive beyond 6 months. Mob stocking was effective in spring but not autumn sowing, implicating soil moisture content as an important factor in germination success. The study demonstrated that the direct seeding technique was successful for two shrub species, highlighting the potential for development of a cost-effective native plant restoration approach.     

Masting,seed dispersal and seed predation in the cycad Macrozamia communis

Summary Little is known about the adaptive value of mast seeding, a common phenomenon in temperate trees and shrubs. Masting is likely to affect both seed dispersal and seed predation. In systems where similar taxa of animals are involved in these two processes, the consequences of mast seeding are likely to be particularly complicated. This study examined the effects of mast seeding in a cycad, Macrozamia communis, on the dispersal of seeds, the pattern of dispersion of seeds and post-dispersal predation on seeds. Dispersal of seeds by possums was poorer from source plants in a masting population than from source plants in an adjacent, non-masting population. This resulted in fewer seeds per seeding female plant in the masting plot being dispersed to favourable sites. We conclude that this is caused by the feeding behaviour and movements of possums in the masting site. The abundance of seeds in this site did not satiate the post-dispersal predators, native rats. In fact, more seeds in this site were eaten than in the nonmasting site. We suggest that the mast seeding observed in M. communis may not be adaptive, but is more likely a consequence of other factors which synchromize flowering within local populations.     

Importance of Seed and Microsite Limitation: Native Wildflower Establishment in Non‐native Pasture

Barriers to establishing native plant communities on former pasture include dominance by a single planted species, hydrologic and edaphic alteration, and native species propagule limitation. Establishment may be dispersal‐limited (propagules do not arrive at the site), microsite‐limited (areas suitable for seedling emergence and survival do not exist), or both. Successful restoration strategies hinge on identifying and addressing critical limitations. We examined seed and microsite limitation to establishment of a native wildflower (Coreopsis lanceolata ) in a former pasture dominated by Paspalum notatum (bahiagrass). We determined the relative and interactive effects of microsite (irrigation and disturbance) and seed limitation on C. lanceolata establishment. We tested (1) irrigation (none, pre‐seeding, and pre‐ and post‐seeding), (2) disturbance (none, sethoxydim, glyphosate, and topsoil removal), and (3) C. lanceolata seeding rate (three seeding densities). Applying glyphosate before seeding increased C. lanceolata establishment compared to other disturbance treatments. Ultimately, C. lanceolata establishment was not affected by irrigation. Coreopsis lanceolata establishment was limited when seeded at 100 live seeds/m² but not at 600 or 1100 live seeds/m². Seed and microsite availability interactively affected C. lanceolata establishment, in that microsite limitation was biologically relevant only when a minimum number of seeds were present. In practice, both seed and microsite requirements must be met for successful establishment, and increasing the availability of seeds or microsites does not compensate for limitations of the other. Here, it is the relative importance of seed and microsite limitations that drives plant establishment; these limitations do not represent a simple dichotomy.     

Adaptation of plant‐mycorrhizal interactions to moisture availability in prairie restoration

The strength and direction of plant response to inoculation with arbuscular mycorrhizal fungi (AM fungi) is dependent on both abiotic and biotic contexts, often generating patterns of AM fungal mediation of plant adaptation. However, knowledge of plant‐community level effects of these interactions in grassland restoration is limited. We conducted a field inoculation experiment by inoculating five plant species native to a drier prairie and five plant species native to a moister prairie with mycorrhizal fungal communities from each prairie type. Species were paired by genus or family to account for phylogenetic effects. The inoculated plants were transplanted to study plots seeded with a restoration seed mix. Plots were manipulated to create either moister or drier conditions similar to environments of the plant species and mycorrhizal communities. In both transplanted and seeded plant species, we found that only drier prairie‐range species benefited from moisture‐regime matched AM fungal inoculum. Other seeded prairie plant species demonstrated a negative response to inoculation, likely due to the earlier successional stage of these species. Additionally, nonseeded plants benefited from inoculation in different ways: native nonseeded plants had highest cover with drier prairie inoculum in drier conditions, while nonnative plants had highest cover with moister prairie‐origin inoculum. These results suggest that use of local AM fungi may be particularly important in restorations at drier sites, even at relatively small differences in moisture availability. Further, specific knowledge of relative responsiveness of seeded plant species and nonseeded plant species to AM fungal inoculation will be useful in planning restorations.     

Native Consumers and Seed Limitation Constrain the Restoration of a Native Perennial Grass in Exotic Habitats

Native consumers and seed limitation may be particularly important in the restoration of native plants where they have been displaced by exotic plants. We used experimental exclosures and seed additions to examine the role of native mammalian consumers and seeding density (500 or 1,000 seeds/m²) in affecting the establishment of a native perennial grass, Purple needlegrass ( Nassella pulchra ), in the grasslands of California. To focus solely on consumers and propagule density, experimental areas were tilled and weeded. Consumers were important determinants of restoration success: averaged across propagule density, consumers reduced N. pulchra seedling recruitment by nearly 30%, reduced seedling height by 44%, reduced plant establishment by 52%, and reduced reproductive tiller length by 43%. Small rodents affected seedling establishment, especially where seeding density was high but did not affect seedling height. Plots accessible by squirrels and rabbits exhibited significantly decreased seedling height and plant establishment, whereas there was no additional impact of allowing large consumers (i.e., deer) access. Despite strong, spatially variable effects of consumers, doubling seed density led to nearly doubled N. pulchra establishment on average. Consumer effects were persistent, shaping N. pulchra abundance in the subsequent growing season and remaining evident over 18 months after the experiment was initiated. Our work suggests that, despite strong consumer effects, seed addition may be a viable strategy for restoration of N. pulchra in invaded areas where it has been displaced by exotic plants, especially when combined with restoration strategies that reduce competition with exotic plants.     

Establishment of Transplants on Machine-Graded Ski Runs Above Timberline in the Swiss Alps

The suitability of 24 native species for restoration above the timberline in Switzerland was assessed with demographic monitoring of their populations after transplanting. The plots were laid out in 1985–1986 and 1995–1996 on machine‐graded ski runs using a total of 8,603 transplants of native grasses, legumes and forbs. Establishment conditions were improved with biodegradable wood‐fiber mats and a small addition of garden soil. Transplant survival rates were generally good after 12 years. The regeneration of mixed stands was clearly recognizable because some transplants successfully reproduced by seed, and colonizers immigrated from the adjacent natural vegetation and neighboring restoration plots. Comparative studies of reproductive parameters in transplants and their donor population revealed that differences in seed production may become nonsignificant within a short time span. These fitness features have important diagnostic value for assessing restoration success and provide information on the performance of the same or closely related genotypes in their natural populations and in the restoration site. The plants studied showed species‐specific traits in establishment after transplanting. Most species can be recommended for restoration in the alpine vegetation belt. The risk of restoration failure can be considerably reduced by using species with different life‐history characteristics. From an ecological point of view, this method is a valid alternative to commercial revegetation using seed mixtures of non‐native species and large amounts of fertilizers.     

Effect of fire on the topsoil seed banks of rehabilitated bauxite mine sites in the jarrah forest of Western Australia

Summary Germinable seed stores of 5- and 8-year-old rehabilitated bauxite mine pits in south-west Western Australia were assessed before and after burning. These seed stores were compared to those of adjacent unmined Jarrah ( Eucalyptus marginata ) forest, to identify at what age fire can be reintroduced, in order to measure restoration success and reduce fire hazard. Soils were sampled in early summer (before fire) and late autumn (after fire). Before fire, the mean topsoil seed bank of 5-year-old sites was 2121 seeds per m² while 8-year-old sites had a mean of 1520 seeds per m². Only the 5-year-old sites were significantly different from the forest mean of 1478 seeds per m² for the same season. After summer burns (and possibly due to seasonal effects) topsoil seed banks of rehabilitated areas (sampled in autumn) decreased by an average of 53 per cent. Topsoil seed banks of 5–8-year-old sites were resistant to lower intensity burns, with 362 seeds per m² of native species surviving mild burns and 108 seeds per m² of native species surviving after an intense summer fire. The topsoil seed reserve of 5–8-year-old rehabilitated areas had a high proportion of annual weed species while the forest sites had high levels of subshrubs and native annuals. Low-intensity burns did not alter the composition of life-forms in the soil seed bank, while intense burns favoured annual weed and shrub species. The results indicate that it is not appropriate to introduce fire to rehabilitated areas before 8 years, due to limited fuel reduction benefits and possible adverse effects on obligate seeding species. The large proportion of weed species in the soil seed bank of young rehabilitated areas is a concern, and remains a major consideration for future disturbance of these areas.     

Seeding conditions of the halophyte Atriplex patula for optimal growth on a salt impacted site

Salt-impacted soils resulting from oilfield brine spills are increasingly becoming a significant problem in oil-producing areas of Canada such as Alberta and Saskatchewan. The native halophyte Atriplex patula is being considered a potential species for phytoremediation of brine-impacted sites in these hemiboreal climactic zones. The objective of this study was to investigate the optimal seeding conditions under field conditions (with no irrigation) of A. patula for phytoremediation of salt from a brine-impacted site. Atriplex patula was identified in preliminary greenhouse trials to have one of the highest salt accumulations in relation to plant yields. Different seeding methods of A. patula were assessed in an attempt to achieve reproducible growth of this species. While plant yields for A. patula were improved on compacted soil by approximately 30-50%, growth was uneven with regard to density and height. The uneven growth may be due to seed quality and low precipitation during the field season, while improvements in plant yield on compact soil might be due to a lack of competition with other species.     

Burning and Grazing Management in a California Grassland: Effect on Bunchgrass Seed Viability

Prescribed fire is an important management tool for reducing the dominance of non‐native species in annual grasslands; both annual and perennial native species show strong vegetative responses in the subsequent growing season. However, although the post‐fire contribution of native species to the seed bank is assumed to be larger than in pretreatment years, the effects on seed quality, particularly viability and longevity, are not well understood. In this study, I germinated Nassella pulchra (purple needlegrass) seed that had been stored for 10 years after collection from target plants receiving treatment combinations of summer burning and grazing by sheep. Seeds from burned plants were larger and had higher germinability than seed from unburned plants. Seeds from plants that were both burned and grazed had the highest germination. The strong relationship between long‐term viability and seed size suggests greater maternal provisioning and increased seed quality subsequent to burning and grazing. I conclude that managing for seed quality may be a useful approach for conservation of native species in California's critically endangered grassland habitats.     

A 10-year study of changes in forest vegetation on Silhouette island, Seychelles

A 10 year study of forest communities on Silhouette island, Seychelles demonstrates stability of forest composition in most areas over this time-scale. Areas with heavy invasion by alien species were found to be regenerating, particularly with the rapid loss of Clidemia hirta. This is attributed to the abundance of well-adapted native plants allowing competitive exclusion to take place, throughout competition for light. It was noted that invasive plant species tend to be unstable on the rocky slopes covered by native high forest. A high rate of tree fall and limited seed dispersal may reduce the impact of the invasive tree Paraserianthes falcataria in the future. Other species such as Cinnamomum verum and Psidium cattleianum may persist as major invaders due to wider seed dispersal.     

Integration of Biological Control and Native Seeding to Restore Invaded Plant Communities

Disturbed natural areas frequently experience invasion by introduced plant species that can reduce native biodiversity. Biological control can suppress these introduced species, but without restoration another introduced species can invade. Integration of biological control with concurrent revegetation can both aid in weed reduction via interspecific plant competition and establish a restored native plant community. This 3‐year study investigated an integrated approach to controlling the introduced annual Mile‐a‐minute weed (Persicaria perfoliata [L.] H. Gross [Polygonaceae]) using the biocontrol weevil Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae) and restoration planting using a native seed mix. A fully factorial design tested weevils and seeding, separately and together, using insecticide to eliminate weevils. The weevils together with the native seed mix reduced P. perfoliata percent cover in 2009 and 2010, and peak seed cluster production in 2010, compared to the insecticide ? no seed control treatment. Persicaria perfoliata final dry biomass was reduced by 75% in 2010 and by 57% in 2011 in the weevils plus seed treatment compared to the control, with weevils having the greatest effect in 2010 and the seed treatment having the greatest impact in 2011. Results suggest an additive effect of biocontrol and seeding in suppressing P. perfoliata. Seeded treatments also developed the highest native plant species richness and diversity, comprised of spontaneous recolonization in addition to species from the seed mix. Results support the use of integrated management of this invasive weed, with suppression through biological control and native revegetation together helping prevent reinvasion while restoring native plant biodiversity.     

Invasion resistance and persistence: established plants win,even with disturbance and high propagule pressure

Disturbances and propagule pressure are key mechanisms in plant community resistance to invasion, as well as persistence of invasions. Few studies, however, have experimentally tested the interaction of these two mechanisms. We initiated a study in a southwestern ponderosa pine (Pinus ponderosa Laws.)/bunch grass system to determine the susceptibility of remnant native plant communities to cheatgrass (Bromus tectorum L.) invasion, and persistence of cheatgrass in invaded areas. We used a 2 × 2 factorial design consisting of two levels of aboveground biomass removal and two levels of reciprocal seeding. We seeded cheatgrass seeds in native plots and a native seed mixture in cheatgrass plots. Two biomass removal disturbances and sowing seeds over 3 years did not reverse cheatgrass dominance in invaded plots or native grass dominance in non-invaded native plots. Our results suggest that two factors dictated the persistence of the resident communities. First, bottlebrush squirreltail (Elymus elymoides (Raf.) Swezey) was the dominant native herbaceous species on the study site. This species is typically a poor competitor with cheatgrass as a seedling, but is a strong competitor when mature. Second, differences in pretreatment levels of plant-available soil nitrogen and phosphorus may have favored the dominant species in each community. Annual species typically require higher levels of plant-available soil nutrients than perennial plants. This trend was observed in the annual cheatgrass community and perennial native community. Our study shows that established plants and soil properties can buffer the influences of disturbance and elevated propagule pressure on cheatgrass invasion.