Variation in bradyspory and seedling recruitment without fire among populations of Banksia serrata (Proteaceae)

Abstract Long-term canopy storage of seeds in fruits (bradyspory) varies among species and is thought to be related to the fire regime experienced by the plant community. This study sought to quantify intraspecific variation in bradyspory among nine populations of Banksia serrata (Proteaceae) on the south coast of New South Wales. Marked differences were found between populations, ranging from more than 30% of follicles open at two coastal sites, to less than 5% of follicles open at two inland heath sites. Low levels of bradyspory occurred particularly in coastal sites which also had Banksia integrifolia, a non-bradysporous species, present. In addition to spontaneous follicle opening without fire, fall of infructes-cences to the ground after breaking of branches was observed to be a major contributor to seed release. At three sites where fire had not occurred for many years, the amount of seedling establishment since the last fire corresponded well with levels of bradyspory; there were no inter-fire recruits at the site with the strongest bradyspory, while at the site with the weakest bradyspory there were numerous inter-fire plants, some with lignotubers large enough to be able to tolerate the next fire. It is argued that populations of B. serrata exhibit variable patterns of recruitment, depending on the site characteristics, ranging from complete dependence on fire for population maintenance to bet-hedging (spreading potential recruitment between fire events and inter-fire periods). Variations in populations and reproductive characteristics among sites make the application of demographic models to management decisions habitat-specific.     

For everything a season: Smoke-induced seed germination and seedling recruitment in a Western Australian Banksia woodland

Abstract The influence of factors associated with fire on seed germination of Australian native species is generally well documented, but examples involving the use of smoke as a fire analogue for ecological research remain limited. The role of season of treatment in the efficacy of smoke as a promotive germination agent was investigated over two growing seasons using natural soil stored seedbanks in Banksia woodland near Perth, Western Australia. Smoke was applied to unburnt sites in the autumn, winter and spring of 1994. Germinant emergence and seedling survival of 37 species representing 18 families was monitored in both unburnt sites and in adjacent, recently burnt sites until the second spring after treatment (October 1995). Recruitment from seed was found to be profoundly affected by the season in which dormancy breaking treatment had been applied. The promotive effect extended beyond the initial year of application. For the majority of the species investigated, application of smoke to unburnt sites in autumn promoted a significantly greater germination response than treatment in winter or spring. In only three cases (introduced annuals, the Fabaceae and Hibbenia amplexicaulis) did autumn smoke treatment not yield better germination than in summer-burnt counterparts. However, in almost half of the cases examined, proportions of seedlings surviving past their first summer after emergence in burnt areas were consistently greater than those in smoked or untreated sites. Most notably, no seedlings emerging during the spring of the first year of study survived into the following summer. Implications of the results with respect to future seed bank research and management of native vegetation are discussed.     

Relationship between rate of crop growth at date of fertiliser N application and fate of fertiliser N applied to winter wheat

To investigate the relationship between the timing of fertiliser N applications and the N use efficiency of wheat, three field experiments with ¹⁵N were set up on winter wheat, on three different soils in France. Different crop N demands on the day of fertiliser application were obtained by varying either crop densities or date of fertiliser application. Labelled ¹⁵NH₄ ¹⁵NO₃ was applied at tillering and during stem elongation. The ¹⁵N recovered from plant and soil at different dates after ¹⁵N addition and at maturity of wheat was measured. The fate of fertiliser N was rapidly determined, most of the fertiliser N accumulated in the wheat at maturity having been taken up within a few days of application. ¹⁵N recovery by the crop at final harvest (%) varied greatly (19–55% N applied) according to crop density, soil type and date of application. It was linearly related to the instantaneous crop growth rate calculated at the day of ¹⁵N application. The amount of fertiliser N immobilised in the soil was constant at 20 kg N ha⁻¹, for all soil types and crop densities. Because residual mineral ¹⁵N in the soil at harvest was negligible and immobilisation was constant, the level of total ¹⁵N measured in the different N pools (soil+plant) reflected the% ¹⁵N uptake by the plant. There was consequently a negative linear relationship between the percentage of ¹⁵N not recovered for measurement, and crop growth rate (i.e. crop N demand) at date of fertiliser application. These results suggest that crop N demand at the time of N application determines the ability of the crop to compete for N with other processes, and may be a major factor determining the division of N between soil and crop. This revised version was published online in June 2006 with corrections to the Cover Date.     

沙埋对半灌木羊柴幼苗的存活、生长和生物量分配的影响

羊柴 (HedysarumlaeveMaxim .)是中国北方沙地飞播进行植被恢复与重建的主要植物种。在晚春与夏初的出苗期 ,羊柴幼苗经常遭受不同深度的沙埋。研究旨在探明沙埋对羊柴幼苗存活、生长和生物量分配格局的影响。6周的沙埋试验结果显示 :当沙埋深度达到其株高时 ,约有 70 %的幼苗死亡 ;沙埋深度达到其株高的 133%时 ,可使羊柴幼苗全部死亡 ;沙埋深度分别为株高的 33%和 6 7%时 ,羊柴幼苗的整株生物量、叶片生物量、根系生物量以及相对生长率都相应地高于非沙埋的对照 (即 :0 %沙埋 )。与非沙埋的对照相比 ,羊柴幼苗在 33%和 6 7%沙埋条件下并不显著地改变其生物量分配格局 ;并且羊柴幼苗的叶数和株高与对照无明显差异 ,但试验期内的新生叶数是沙埋处理 (即 :33%、6 7%和 10 0 %沙埋 )的幼苗明显地高于非沙埋的对照。     

Effects of Salinity on the Growth Rate and Survival of Juvenile Littorina saxatilis Gastropods from Habitats with Different Salinity Regimes

The effects of salinity on the growth rate and survival of juvenile Littorina saxatilis gastropods reared in the laboratory from the young of progenic females collected in estuarine, intermediate, and marine habitats were studied. The optimum growth conditions of juveniles were dependent on the salinity regime in their original habitat. The progeny of females from the marine site showed maximum survival at a salinity of 23, the value corresponding to the normal salinity in their native habitat during the breeding period, while at 14, the growth of juveniles from this population was strongly suppressed. Juveniles originating from the estuarine habitat were able to maintain equally high growth rates at 23 and 14; however, at 14, they grew significantly faster than juveniles from the marine site. The progeny of females from the intermediate habitat showed intermediate growth rates at 14. Fluctuating salinity (23–8–23) had an adverse effect on the growth of juvenile Littorina, irrespective of the parental habitat. The differences in survival, size, and growth rates of the progeny of L. saxatilis in habitats with different salinity regimes are discussed in relation to their potential adaptive significance to life in estuaries.     

Improving fertiliser efficiency on calcareous and alkaline soils with fluid sources of P,N and Zn

Alkaline calcareous or sodic soils represent an important proportion of the world's arable soils and are important for cereal production. For calcareous soils in general, despite high applications of P fertiliser for many years, P deficiency in cereals is common. Field experiments were conducted to test the relative ability of granular (e.g. DAP, MAP and TSP) and fluid fertilisers to supply P to wheat on grey calcareous and red brown calcareous sandy loam soils (Calcixerollic xerochrepts). A pot experiment was also conducted with these soils and with two non-calcareous alkaline soils to investigate the effects of placement on the efficiency of fertiliser performance. In 1998, fluid and granular sources of P, N and Zn were compared in the field by banding below the seed at sowing. In 1999, MAP applied as granular, and technical grade MAP applied as fluid, were compared as sources of P in rate response experiments. First year results showed that fluid sources of P, N and Zn produced significantly more grain than the granular product. In the following year, fluid fertilisers were found to produce significantly higher response curves for shoot dry weight, grain yield and P uptake in grain. At a commercial rate of 8 kg P ha^–1, fluid fertiliser produced between 22% and 27% more grain than the granular product. Soil moisture and fertiliser placement effects are implicated in the higher efficiency of fluid fertilisers.     

Window of opportunity: an episode of recruitment in a Banksia hybrid zone demonstrates continuing hybridization and phenotypic plasticity

Background and Aims

In perennial plants (especially post-fire resprouters), extant populations may reflect recruitment events in the distant past. This is true of hybrid zones formed by two Banksia species of swamps and woodlands in south-eastern Australia, Banksia robur and B. oblongifolia. Both resprout after fire but recruitment is dependent on periodic fires. Although plants of intermediate morphology have also been identified as hybrids using allozyme markers, the extent of ongoing hybridization is unknown. This study investigates whether both microsatellite markers and morphological measurements can be used to distinguish between the two species and their hybrids. A recent recruitment event and microsatellite markers allow the frequency of ongoing hybridization to be estimated, and also the effects of environmental variation on the morphology of plants and seedlings to be tested.

Methods

Variation at seven microsatellite loci was scored and seven leaf characteristics within putatively pure stands and mixed stands of both species were measured, revealing that the two species were genetically and morphologically distinct and that mixed stands also contained genetically and sometimes morphologically distinct hybrids. An opportunity created by wildfires was used to analyse the genetics and morphometrics of adults and seedlings from two hybrid zones.

Key Results

Approximately 9 % of adults and 21 % of seedlings were identified as genetic hybrids in both hybrid zones. Within these sites, the genotype of mature plants correlated well with morphology, except for some hybrid plants that had parental morphology. However, seedling morphology was highly variable and insufficient to describe the composition of the hybrid zone in this cohort. Greater phenotypic plasticity was evident among seedlings growing within the hybrid zones than seedlings growing in pots.

Conclusions

The hybrid zones are complex and the range of genotypes detected in seedlings reveals both continuing hybridization and introgression.     

提高大岩桐试管苗移栽成活率的实验

取芽或茎尖经HgCl消毒后获得无菌外植体,将其接种于不同组合的培养基上并获得小植株,将小植株进行继代、生根培养,经炼苗后移栽,成活率很高。     

Basal fertiliser application method, tuber initiation nitrogen, foliar NPK and the tolerance of potatoes to infection by the potato cyst nematodes Globodera rostochiensis and G. pallida

The effects of broadcast granular, placed liquid and foliar fertilisers on the tolerance of potatoes to infection by potato cyst nematodes were investigated. The tolerance of the potato cv. Pentland Dell was not significantly improved by fertiliser application type but placed liquid fertiliser, with or without foliar applications, increased the concentrations of N, P and K measured in whole plant dry matter of PCN infected plants. The tolerance of the potato cv. Sante was not statistically improved by altering the balance of fertiliser nitrogen applications between planting and tuber initiation or by applying foliar nitrogen. Nitrogen applications of 120 kg N ha^-1 at planting and a further 120 kg N ha^-1 at tuber initiation supplemented with foliar N, however, achieved a larger tuber yield than the same nitrogen programme without foliar N and gave a significantly greater yield than the application of 240 kg N ha^-1 at planting plus foliar N. The emergence of both cultivars was delayed in the absence of oxamyl. N, P and K concentrations within whole plant dry matter were significantly higher in plants from oxamyl treated plots and both N and K concentrations were significantly increased by increasing the quantity of N at planting, at 56 DAP. Splitting the fertiliser N between planting and tuber initiation appears to be important in maintaining the availability of this nutrient to PCN infected plants throughout the season.     

Fruit colour polymorphism in Acacia ligulata: seed and seedling performance, clinal patterns, and chemical variation

Fruit colour polymorphisms are widespread in nature, but their ecological and evolutionary dynamics remain poorly understood. Here we examine Acacia ligulata, a shrub of the Australian arid zone which exhibits a red/orange/yellow aril colour polymorphism. We asked whether the polymorphism had a genetic basis; whether selection acted differentially on morphs during the seed and seedling stages; whether geographic variation in morph frequencies was correlated with environmental factors; and whether morphs differed in physical or chemical characteristics that might influence selection on them. When grown to maturity in a common greenhouse environment, maternal families of seeds showed phenotypic patterns consistent with biparental genetic control of the polymorphism. In contrast to other fruit-colour polymorphic species, progeny of A. ligulata morphs did not vary in rates of seedling emergence or survival in a common garden. Sampling along a 580 km transect revealed clinal variation in morph frequencies. Frequencies of the yellow morph decreased, and frequencies of the red morph increased, across a gradient of decreasing temperature and increasing rainfall. Morphs did not differ in seed mass, aril mass, or in profiles of fatty acids and flavonoids in either arils or seeds. However, morphs showed consistent differences in carotenoid profiles' and elemental content of arils, suggesting that selection by avian and insect seed dispersers, seed predators and herbivores should be investigated. These patterns indicate that both abiotic and biotic factors may contribute to selection on the A. ligulata polymorphism. This revised version was published online in August 2006 with corrections to the Cover Date.     

不同地理种源桔梗种子性状及苗期生长分析

对来源于不同产地的43份桔梗[Platycocon grandiflorus（Jaeq．）A．DC．]种子的地理变异、种子特性及幼苗生长状况进行了分析。根据不同种源桔梗种子的特性、发芽率及幼苗的生长状况,利用聚类分析方法可将供试的桔梗种源大致分为南方和北方2个地理种源,其中北方种源的种子颗粒较大,千粒重达1．21～1．35g;南方种源的种子发芽率高（65％～71％）,种子千粒重为1．15～1．20g,幼苗生长健壮,根系较发达。此外,桔梗种子的发芽率与纬度呈明显的负相关,桔梗幼苗地上部分的生长与根茎的生长存在显著的相关性,可作为早期间苗及幼苗筛选的标准。研究结果表明,来源于安徽毫州及安徽太和的桔梗种源适合在浙江富阳地区栽培。     

Banksia nectar and pollen: Dietary items affecting the abundance of the common blossom bat,Syconycteris australis,in southeastern Australia

Abstract The relationship between the abundance of the common blossom bat (Syconycteris australis), a nectar/pollen specialist, and the availability of its food sources was investigated across nine Banksia integrifolia heathland sites in coastal New South Wales, Australia. An index of bat abundance was more highly correlated with direct estimates of food density (productive inflorescences) than indirect estimates of food (Banksia trees and total inflorescences). Furthermore, standing crops of nectar-energy per hectare were better predictors of bat abundance than pollen-nitrogen per hectare. Adult male mass did not differ significantly across sites of differing food availability, suggesting that the corresponding increase in bat abundance with food reduces the amount of fat an individual can deposit. Although males and females responded similarly to food, adult numbers were more strongly correlated with food supply and they were more likely to be recaptured than juveniles. Energy requirements of blossom bats exceeded availability in four out of nine sites. Flying foxes were heard feeding in large numbers at the remaining five sites, where energy was superabundant for S. australis. In contrast to the conclusions of previous studies of megabats, these results provide the basis for a prediction that nectar-energy, rather than pollen-nitrogen, is the primary limiting factor for populations of the blossom bat.     

Mobility, solubility and lability of fluid and granular forms of P fertiliser in calcareous and non-calcareous soils under laboratory conditions

Despite a long history of application of phosphorus fertilisers, P deficiency is still a major limitation to crop production on calcareous soils. Recent field research conducted in highly calcareous soils in southern Australia has demonstrated that both grain yield and P uptake of wheat (Triticum aestivum L.) is greater when fluid forms of P are used compared to granular forms. To improve our understanding of the mechanisms underlying this response to P in the field, we compared the lability, solubility and mobility of P applied as either a fluid (3 products) or granular (3 products) form to two calcareous and one alkaline non-calcareous soils in the laboratory. Over a five-week period, between 9.5 and 18 % of the P initially present in the fertiliser granules did not diffuse into the surrounding soil. The degree of granule dissolution was independent of the soil type. In contrast, P solubility, lability and diffusion were significantly greater when fluid products were applied to the calcareous soils, but not to the alkaline non-calcareous soil. These findings are discussed in relation to field trials results where fluid products outperformed granular fertilisers.     

Seed germination and seedling survival in a colony of the common cormorant,Phalacrocorax carbo

Germination and seedling survival of some woody plants were examined in a colony of the common cormorant at Unoyama, central Japan. The germination ofQuercus serrata andPinus densiflora was less successful in the colony than outside the colony. The percentage of germination success was negatively correlated with the amount of cormorant faeces scattered on the ground and also with the soil water conent. Most of the germinated seedlings inside of the colony died with symptoms such as necrosis spreading from the edge of leaves. Saplings ofQ. serrata also tended to die more in the colony than outside the colony. The survival rate ofQuercus glauca seedlings with scattered faeces on their leaves and/or on the the surrounding soil was significantly lower than the rate of those free of faeces. These results suggest that in the cormorant colony, germination of seeds and seedling survival are greatly inhibited due to both the direct and indirect effects of cormorant faeces.     

温度对拟目乌贼幼体日生长率和存活率的影响

以温度为单因素变量,在人工饲养环境中,分析水温对拟目乌贼幼体日生长率与存活率的影响。实验结果表明,当水温处于28.1～32℃之间时,拟目乌贼幼体的日生长率与水温呈正相关关系;当水温处于32～32.67℃时,拟目乌贼幼体的日生长率与水温呈负相关关系;当水温处于29.5～32.6℃时,拟目乌贼幼体不易出现幼体死亡(死亡率<6.25%),适宜拟目乌贼幼体的存活;而当水温处于32.3～34℃之间时,拟目乌贼幼体出现了13.16%～61.16%的幼体死亡,不适宜拟目乌贼幼体的存活。实验结果表明,当水温处于29.5～32℃之间时,拟目乌贼幼体的存活率高(存活率>93.75%),且日生长率处于0.24%～1.76%,适宜拟目乌贼幼体的存活。     

Interspecific and intraspecific variation in tree seedling survival: effects of allocation to roots versus carbohydrate reserves

We examined interspecific and intraspecific variation in tree seedling survival as a function of allocation to carbohydrate reserves and structural root biomass. We predicted that allocation to carbohydrate reserves would vary as a function of the phenology of shoot growth, because of a hypothesized tradeoff between aboveground growth and carbohydrate storage. Intraspecific variation in levels of carbohydrate reserves was induced through experimental defoliation of naturally occurring, 2-year-old seedlings of four northeastern tree species –Acer rubrum, A. saccharum, Quercus rubra, and Prunus serotina– with shoot growth strategies that ranged from highly determinate to indeterminate. Allocation to root structural biomass varied among species and as a function of light, but did not respond to the defoliation treatments. Allocation to carbohydrate reserves varied among species, and the two species with the most determinate shoot growth patterns had the highest total mass of carbohydrate reserves, but not the highest concentrations. Both the total mass and concentrations of carbohydrate reserves were significantly reduced by defoliation. Seedling survival during the year following the defoliation treatments did not vary among species, but did vary dramatically in response to defoliation. In general, there was an approximately linear relationship between carbohydrate reserves and subsequent survival, but no clear relationship between allocation to root structural biomass and subsequent survival. Because of the disproportionate amounts of reserves stored in roots, we would have erroneously concluded that allocation to roots was significantly and positively related to seedling survival if we had failed to distinguish between reserves and structural biomass in roots. Received: 14 December 1999 / Accepted: 2 June 1999