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1.
Pinus halepensis is a widely distributed species in the Mediterranean basin. It is generally well adapted to regenerate after wildfire, except when fire intervals are too short (≤15 years). In these latter situations, direct seeding could be a good alternative for restoring pine woodland after fire. Under dry climate, low seedling growth and survival can greatly limit the use of seeding. Early studies have shown that seedlings grown from large seeds have higher seedling establishment, growth and survival. Seed size grading may however reduce the genetic diversity of a seed lot by eliminating part or all of the families with relatively small seeds. An alternative to improve seed lot quality without losing genetic variability could be collecting and sieving seeds from each family separately. In order to explore the influence of seed mass on P. halepensis seedling performance, seeds from five half-sib families differing in mean seed mass were sown under greenhouse and field conditions. Final seedling emergence was unrelated to seed mass and half-sib family. The time of emergence was also unrelated to seed mass but it varied among families. Seed mass showed a positive effect on seedling height and diameter, both at population level and within family throughout the study period (9 months under greenhouse conditions and 20 months under field conditions). We also observed a negative relationship between seed mass and relative growth rate for seedling diameter, but it was not high enough to fully compensate the initial differences due to seed mass at the end of the 20-month study period. Seedling predation had a considerable impact on seedling survival, and it was not related to seed mass. When seedlings killed by predation were excluded from the survival analysis, larger seedlings, coming from larger seeds, showed slightly better survival, but only during the first growing period. The small advantages obtained from large seed mass in seedling development do not seem to justify the increased operational costs derived from seed mass selection for each family.  相似文献   

2.
The establishment of invasive plant populations is controlled by seed input, survival in the soil seed bank, and effects of soil surface disturbance on emergence, growth, and survival. We studied the invasive vine Celastrus orbiculatus Thunb. (Oriental bittersweet) to determine if seedlings in forest understory germinate from the seed bank or from seed rain. We also conducted a greenhouse experiment to investigate the role of leaf litter mass and physical texture on seedling survival, growth, and allocation. In the understory of an invaded mixed hardwood forest, we measured seed input, seedling emergence with seed rain, and seedling emergence without seed rain. Mean seed rain was 168 seeds m−2: mean seedling emergence was 107 m−2, and there was a strong correlation between seed rain and seedling emergence. The ratio of seedlings to seed input (0.61) was close to the seed viability (0.66) leaving very few seeds to enter the seed bank. Seed bank germination under field conditions was low (1 seedling m−2). Soil cores were incubated in a greenhouse to determine seed bank viability, and germination from these soil cores did not occur. To determine how litter affects seedling establishment and growth, we measured seedling emergence and biomass allocation in a greenhouse experiment. Seeds were placed below intact and fragmented deciduous leaf litter in amounts ranging from zero to the equivalent of 16 Mg ha−1. Seedling emergence was not affected by fragmented litter, but decreased to <20% as intact litter increased to 16 Mg ha−1. Increasing litter resulted in greater allocation to hypocotyl and less to cotyledon and radicle, and this effect was greater in intact litter. C. orbiculatus seedlings achieve emergence through forest floor litter through plasticity in allocation to hypocotyl growth. The low survival of C. orbiculatus in the seed bank suggests that eradication of seedling advance regeneration and adult plants prior to seed rain may be an effective control strategy. However, the intact forest floor litter of an undisturbed forest will not prevent seedling establishment.  相似文献   

3.
The effects of litter cover on the germination of seeds of three tropical rainforest, pioneer tree species (Cecropia obtusifolia, Heliocarpus appendiculatus and Piper auritum) was investigated. Germination of seeds of all tree species was partially or totally inhibited when the seeds were covered with litter, whereas uncovered seeds or seeds covered with paper instead of litter germinated. Seed size was directly correlated with the capacity of the germinated seeds to emerge through the litter. In soil experiments in the greenhouse, seedling emergence from the soil was inhibited by the presence of litter on the soil surface.  相似文献   

4.
Cordia africana is a very important indigenous tree species for timber and other products and services in Ethiopia.Seed traits and seedling vigour of seeds from 12 provenances of the species were compared.Mean seed mass for each provenance was assessed for 1000 seeds in10 replications,and seed length and width were measured for 100 seeds in four replications per provenance.Germination was assessed in a glasshouse taking 400 seeds from each provenance.Root collar diameter and height of 440 seedlings grown in a nursery for 290 days in Addis Ababa were measured.Seed length,seed width,seed mass,and shoot height and root collar diameter of seedlings showed significant differences(P0.001) among provenances.Correlation analysis between seed and seedling traits and environmental variables revealed significant positive correlations between seed width and germination percentage,seed width and altitude,seed width and longitude and seed length and latitude.Negative correlations were obtained between seed width and temperature,seed width and rainfall,seed mass and temperature,and germination and temperature of the seed source.As expected,differences in seed trait did not explain the variability in seedling vigour.Determining quantitative variations in seed traits and seedling vigour among provenances and the patterns along environmental gradients are essential for informing decisions on the tree improvement programme of the species.  相似文献   

5.
JINKS  R. L.; JONES  S. K. 《Forestry》1996,69(4):335-345
Sitka spruce seeds which had been: (1) untreated (U), (2) prechilled(P), or (3) prechilled and then redried and stored for 16 months(R), were sown into progressively warmer seed beds on four datesat monthly intervals from March to June. At each sowing date,samples of seed were germinated in the laboratory at optimum(20°C) and sub-optimum (10°C) temperatures. Prechillingand prechilling + redrying both increased the rate and totalamount of germination compared with untreated seed at each testtemperature. However in the nursery, the beneficial effectsof pretreating Sitka spruce seed were restricted to sowing inMarch and April when soil temperatures were sub-optimal forthe germination of untreated seeds. Pretreatment resulted inrapid seedling emergence at soil temperatures between 10°Cand 15°C, whereas untreated seed germinated slowly and seedlingemergence continued until high soil temperatures in June killedungerminated seeds. The pattern of seedling emergence from theredried seed was similar to that from the prechilled seed, exceptfor a lag in the start of seedling emergence probably due tothe extra time needed for redried seed to imbibe water in theseed beds. Thus redrying caused insignificant loss of seed performanceon the nursery. Seed sown in May and June experienced average temperatures closeto the optimum for germination of 20°C, however daily maximaregularly exceeded 35°C resulting in the cessation of seedlingemergence in all three seed treatments, and the loss of newlyemerged seedlings. Periods of warm weather from June onwardswere the main factors limiting the final number and size ofseedlings.  相似文献   

6.
Cordia africana is a very important indigenous tree species for timber and other products and services in Ethiopia. Seed traits and seedling vigour of seeds from 12 provenances of the species were compared. Mean seed mass for each provenance was assessed for 1000 seeds in 10 replications, and seed length and width were measured for 100 seeds in four replications per provenance. Germination was assessed in a glasshouse taking 400 seeds from each provenance. Root collar diameter and height of 440 seedlings grown in a nursery for 290 days in Addis Ababa were measured. Seed length, seed width, seed mass, and shoot height and root collar diameter of seedlings showed significant differences (P < 0.001) among provenances. Correlation analysis between seed and seedling traits and environmental variables revealed significant positive correlations between seed width and germination percentage, seed width and altitude, seed width and longitude and seed length and latitude. Negative correlations were obtained between seed width and temperature, seed width and rainfall, seed mass and temperature, and germination and temperature of the seed source. As expected, differences in seed trait did not explain the variability in seedling vigour. Determining quantitative variations in seed traits and seedling vigour among provenances and the patterns along environmental gradients are essential for informing decisions on the tree improvement programme of the species.  相似文献   

7.
Half-sib seed of several eastern white pine (Pinus strobus L.) families was used to examine seed mass effects on laboratory germination, and seedling emergence and growth under moderate and low light (47 and 13% full sunlight) in a greenhouse. Percent germination and speed of germination under laboratory conditions were not related to seed mass among half-sib families or multi-family seedlots bulked by seed mass. Percent seedling emergence in the greenhouse was not related to seed mass, but families with heavier seeds exhibited faster emergence. Both rate and percent emergence were significantly increased under low light. Family differences in leaf, stem, root, and total seedling dry mass, primary root length, and the number of first-order-lateral-roots were positively related to seed mass in both light environments. Low light diminished the absolute biomass increment per unit seed mass, but the proportional change in biomass with seed mass was similar between light environments. Rate of emergence also influenced seedling size within families, with earlier emergence increasing seedling dry mass from 7 to 58%, dependent on light environment. Biomass partitioning coefficients were influenced by light environment but largely independent of seed mass.  相似文献   

8.
A study was conducted to determine the effects of electrostatic field (ESF) treatment on seed germination and seedling growth of Sorbus pohuashanesis. The experiments were arranged by uniform design computed by the Data Processing System (DPS), including three levels of seeds soaking time, four levels of ESF intensity and four levels of ESF treatment time, with 12 treatments. Ten seeds were used in each treatment with three replicates. Seed vigor, seed germinating ability, emergence rate of seedling, survival rate of seedling, and seedling height and diameter, as well as the change in activities of superoxide dismutase (SOD), soluble protein contents, total chlorophyll contents, soluble total sugar contents in leaves of S. pohuashanensis seedlings were measured after ESF treatments. The experiment results show that ESF treatment could improve the water absorption ability of dry seeds of S. pohuashanensis, resulting in fast germination at room temperature under light conditions. Combined treatment of ESF with cold stratification could increase seed germination percentage significantly (to 42.20%), promote seedling height growth, affect leaf SOD activity, and could raise contents of total chlorophyll, soluble protein, and total soluble sugar in leaves. Seed soaking time had a significant effect on seed relative electroconductivity, seed germination under light, SOD activity, soluble protein content and total soluble sugar content of seedling leaves. ESF intensity exerted a moderate effect on these indexes. ESF treatment time only had significant effect on total chlorophyll contents, no evident effect on other indexes.  相似文献   

9.
The aim of this study is to evaluate the recruitment possibilities of holly (Ilex aquifolium L.) populations under Pinus sylvestris plantations in the mountains of Central Spain. Population recruitment of holly under P. sylvestris L. plantations was studied at two localities. We sampled holly seed rain, seed bank, and seedling emergence and survival (of both emerged and planted seedlings) in both localities. Seed germination was analysed by randomly sowing Ilex seeds and their subsequent recollection and analysis over the following 3 years (only in one locality). Seed rain, seed bank and emerged seedling densities did not differ between localities. Seed bank density was between 10 and 20 seeds m−2, considerably higher than the observed seed rain (0.4–1.2 seeds m−2), and also higher than the emerged seedling density (0–4 seedlings m−2). But Ilex is not very efficient in germinating under pine forests (29.1% germination after 3 years). This may indicate a seed accumulation process of at least 5 years. Seedling survival for the first year differed among the studied sites (50–60 vs. 17%). Nevertheless these survival rates are higher than those found for the same seedling populations in different forest habitats (not Scots pine forests) from near locations. Differences in summer water stress between the study sites are proposed as the main cause of the observed differences in seedling survival. It is concluded that P. sylvestris forests may provide one of the best regeneration habitats for holly in the Mediterranean area, where this species is close to the Southern limit of its distribution.  相似文献   

10.
在大叶椴种子贮藏时期进行打破休眠对发芽率和出苗率影响的试验表明:即先从大叶椴坚硬果实内取出休眠种子在浓硫酸中脱皮10 min后,再在无基质(3℃)条件下层积催芽140~168 d(直到第1粒种子开始发芽为止).结果表明:经过处理后的种子当发芽试验中昼夜温度为3~15℃(16 h+8 h)时,几周后种子的发芽率达90%;...  相似文献   

11.
Seed mass and relative growth rate (RGR) are important determinants of early seedling growth, and hence seedling establishment. Although a positive interspecific relationship between seed mass and seedling dry mass is well established, much less is known about the relationships among seed mass, seedling mass and RGR within species. We examined relationships among seed mass, seedling mass and RGR within and among maternal plant lines of Scots pine (Pinus sylvestris L.). To assess the effects of seed mass and maternal origin on RGR, individual seeds from two seed crops (years 2004 and 2005) of ten maternal plants growing under nursery conditions were weighed and then germinated. Seed mass was strongly determined by maternal plant, and seedling mass was largely determined by seed mass, with a positive correlation between these variables both across and within maternal plants. In contrast, RGR was weakly related to seed mass, with no consistent pattern in the sign of the relationship. It is well known that species differ in RGR and that RGR is related to seed mass across species. Lack of consistent evidence for this relationship within maternal lines, and for Scots pine overall, suggests that the relationship is not directly causal, but reflects consistent evolutionary covariation in these two physiologically independent traits.  相似文献   

12.
The endozoochorous and epizoochorous dispersal of vascular plant species by roe deer (Capreolus capreolus) and wild boar (Sus scrofa) was investigated in forest areas of Schleswig-Holstein and Lower Saxony, Germany. The primary aim of this study was to learn about which plant species and in what numbers diaspores are dispersed by the two wild ungulate species. In particular, the significance of zoochory for species composition and biodiversity of forests was evaluated. Fresh faecal pellets were collected from April–November 2001 in the forests of the two study areas. In addition, the coats and hooves of shot roe deer and wild boar were brushed out. The number of viable seeds was determined by greenhouse germination (seedling emergence method). The samples were spread in trays over sterilized soil from the study forests and were kept under controlled conditions in the greenhouse for 12 months. A total of 2,473 individuals from 77 vascular plant species were recorded. While roe deer exceeded wild boar concerning seed contents in the faeces, the significance of roe deer for epizoochorous dispersal was relatively low compared with wild boar. An analysis of the habitat preference of the vascular plant species dispersed by the two ungulate species revealed a high proportion of species growing in forests as well as in the open landscape, and also of non-forest species, while woody plants and herbaceous species closely tied to forest habitats were severely underrepresented. We also discuss consequences for forest ecology and nature conservation.  相似文献   

13.
Talbotiella gentii is a critically endangered caesalpiniaceous legume endemic to Ghana, restricted in distribution to the margins of the forest zone where there has been extensive fire damage in recent decades. It occurs as isolated, near-monospecific populations, some of which show little seedling regeneration. We studied its reproduction to determine limitations that might inform efforts to prevent its extinction. We report on flowering phenology, pollen dispersal and germination, fruit and seed set, seed size and germination, and seedling survival, using controlled and open pollination. Talbotiella gentii flowers profusely in most years. Although the flowers are coloured and scented, no animal pollinators were observed but pollen can be dispersed by wind. In open pollination, the number of pollen grains on stigmas and their germination was sufficient to fertilise the three ovules, despite competition from heavy stigmatic infestation by fungal spores and hyphae. Fruit set and seed set were low due to high flower losses and fruit abortion during development but ripe seeds showed high germination. Controlled pollination experiments (self, supplemented self, and intra- and inter-population crosses) showed that, while the species is self-compatible, selfing was the least successful treatment in all of the above steps of reproduction, whereas cross-pollination enhanced most steps, the more so for inter-population crosses. Seed size was notably greater in inter-population crosses and was positively correlated with genetic distance of the cross. The larger seeds associated with cross-pollination showed higher germination and seedling survival in the nursery. We conclude that limitations to natural reproduction in T. gentii are principally due to processes between pollen germination and fruit and seed set, including pollen quality (low genetic diversity and inbreeding), fertilisation rates, flower and fruit abortion, and resource limitation. Low seed size in open and self pollination may have implications for seedling establishment. Species fitness might be improved by introducing other genotypes to existing populations, but in situ protection of the populations is essential in the medium term.  相似文献   

14.
China is one of the countries most severely affected by desertification. Haloxylon ammodendron is an ecologically important component of the desert ecosystem and is one of the main shrub species used for ecological restoration. We compared the genetic variation in seed and seedling traits among six H. ammodendron provenances arrayed from east to west in China. The experiment was carried out in a greenhouse in well-prepared seedling beds (lines 1.5 m apart and seeds with in lines 1.0 m apart, 2.0 cm deep) with five lines (seven seeds per line) per provenance in a randomized block design with six replicates. The seed traits of fruit wing length, kernel weight, germination rate, and survival rate were compared, as were the seedling traits of internode length, branch number, assimilation shoot diameter, height, collar diameter, new shoot length, main root number, main root length, aboveground fresh weight, and underground fresh weight. Moreover, correlations between each seed and seedling trait and climate and geographical factors were assessed. The results show that the seeds from Dengkou County, Inner Mongolia had the best performance. Germination rate and survival rate were significantly positively correlated with longitude; and fruit wing length, kernel weight, seedling height, and new shoot length were significantly negatively correlated with latitude. Fruit wing length was significantly correlated with altitude. Among the climatic factors, the temperature in January had a strong direct effect on fruit wing length, germination rate, seedling height, and new shoot length. The mean annual rainfall had a strong direct effect on collar diameter. Humidity had a strong direct effect on survival rate. Seedling height, aboveground weight, and collar diameter could be important criteria for early provenance selection in the seedling stage. This study provides a reference for the selection of high-quality H. ammodendron seeds for drylands of northwest China.  相似文献   

15.
We studied seed germination and early seedling growth of Pinus densata to explore the range of variability within the species and to inform afforestation practices.Phenotypes were evaluated at a forest tree nursery under conditions that support Pinus yunnanensis, one of the presumed parental species of P. densata. Seeds were collected from 20 open-pollinated trees within each of eight autochthonous populations representing the natural distribution of P. densata in China to assess variation in germination traits and early seedling growth, and to examine the relationships among these traits. Results showed that seeds from all populations germinated and seedlings established successfully. There were significant differences among populations in 13 of 14 traits evaluated. Seed germination and early seedling growth were strongly related to seed size and seed weight. Bigger seeds germinated earlier and faster than small seeds, and seedling size was positively correlated with seed size. Some germination traits were strongly and significantly correlated with climatic variables associated with the provenance of the studied populations. Based on these observations, we conclude there were large, significant, and biologically important differences among P. densata populations in seed germination and seedling growth traits. The observed variability probably reflects a high degree of adaptive differentiation among populations that is likely to be relevant for future afforestation.  相似文献   

16.
Climate warming is already influencing plant migration in different parts of the world. Numerous models have been developed to forecast future plant distributions. Few studies, however, have investigated the potential effect of warming on the reproductive output of plants. Understorey forest herbs in particular, have received little attention in the debate on climate change impacts.This study focuses on the effect of temperature on sexual reproductive output (number of seeds, seed mass, germination percentage and seedling mass) of Anemone nemorosa L., a model species for slow colonizing herbaceous forest plants. We sampled seeds of A. nemorosa in populations along a 2400 km latitudinal gradient from northern France to northern Sweden during three growing seasons (2005, 2006 and 2008). This study design allowed us to isolate the effects of accumulated temperature (Growing Degree Hours; GDH) from latitude and the local abiotic and biotic environment. Germination and seed sowing trials were performed in incubators, a greenhouse and under field conditions in a forest. Finally, we disentangled correlations between the different reproductive traits of A. nemorosa along the latitudinal gradient.We found a clear positive relationship between accumulated temperature and seed and seedling traits: reproductive output of A. nemorosa improved with increasing GDH along the latitudinal gradient. Seed mass and seedling mass, for instance, increased by 9.7% and 10.4%, respectively, for every 1000 °C h increase in GDH. We also derived strong correlations between several seed and seedling traits both under field conditions and in incubators. Our results indicate that seed mass, incubator-based germination percentage (Germ%Inc) and the output of germinable seeds (product of number of seeds and Germ%Inc divided by 100) from plants grown along a latitudinal gradient (i.e. at different temperature regimes) provide valuable proxies to parameterize key population processes in models.We conclude that (1) climate warming may have a pronounced positive impact on sexual reproduction of A. nemorosa and (2) climate models forecasting plant distributions would benefit from including the temperature sensitivity of key seed traits and population processes.  相似文献   

17.
We investigated the effect of seed mass on emergence, seedling survival and growth ofPterocarpus marsupium Roxb., a medium to large, commercially valuable and deciduous tree species. Among the three size classes viz. small (10-12 mm), medium (13-15 mm) and large (16-17 mm), the maximum proportion, of seed by number (54.12%) and dry weight (51.87%) was recorded, in the medium size seed class. Seed length and seed width were greatest in the large seed class (16.50 mm, 7.33 mm) followed by medium (13.50 mm, 5.60 mm) and small (11.37 ram, 3.66 mm). Similarly, hundred seed weight (100 sw) varied from a maximum of 12.92 g in the large seed class to intermediate 10.95 g in the medium seed class and minimum of 7.02 g in the small seed class. The large seed size showed maximum emergence and shoot length over the medium and small seed class. After six months of growth, significant variations due to seed size were also observed for the growth and dry weight of P. marsupium seedlings. Seedling vigour, expressed in terms of height, collar diameter, number of leaves and dry biomass, was sig- nificantly affected by seed class. Seedlings that emerged from large seeds showed better growth and produced heavier seedlings as compared to medium and small seeds.  相似文献   

18.
《林业研究》2021,32(2)
Acid rain has become a major concern due to increasing atmospheric pollution,particularly in China.We investigated whether acid rain inhibits the germination of seeds and subsequent emergence of seedling of four tree species from southern China:Cunninghamia lanceolata,Fokienia hodginisi,Pinus massoniana and Phoebe zhennan by simulating acid rain with pH of 2.5,3.5,4.5 and 5.5.We hypothesized that the inhibitory effect of acid rain on germination of seeds and emergence of seedling varies between species and the degree of acidity.A solution of 1 N H_2 SO_4 and 1 N HNO_3 in the ratio of 10-1 was prepared and diluted to four pH levels,and seeds were supplied with solutions of these pH values and distilled water as control and tested for germination in a controlled growth chamber.The results revealed that simulated acid rain of pH 2.5 adversely affected the germination capacity of F.hodginisi and P.zhennan;while all acid solutions significantly increased germination of P.Massoniana;but had no effect on germination of C.Lanceolata seeds.Strong acid solution(pH of 2.5) adversely affected elongation of radicle and hypocotyl as well as fresh and dry weights of radicle and hypocotyl of tender seedlings.The result demonstrated that seedling emergence is more sensitive than seed germination to simulated acid rain,and germination of conifer species are less sensitive than broad leaved species to simulated acid rain.As a whole,acid rain of pH of 3.5 is the threshold level and acid rain below this value will have a detrimental effect on seed germination and seedling emergence.  相似文献   

19.
The aim of the present study was to investigate the effect of the natural sequence of temperature conditions between the time of seed sowing and their germination on dormancy release of Prunus avium, P. mahaleb, P. divaricata, P. laurocerasus, P. spinosa, Cornus mas, C. sanguinea, and Celtis australis seeds which are enclosed in a hard stony endocarp. According to their collection date, the seeds (with the endocarp) of the above species were sown outdoor in summer, autumn, and winter and the number of emerged seedlings was counted during the following two springs. For all species, the first sowing date was immediately after seed collection and cleaning. In all species, seedling emergence occurred in early spring and dormancy was released only after the exposure of seeds to specific season conditions. The exposure of seeds of all studied species, except C. australis, to a period of warm temperatures prior to winter was necessary for dormancy breaking and germination. Autumn sowing of P. laurocerasus and C. sanguinea seeds, which were collected in summer, and the sowing immediately after seed collection of the rest species, resulted in a maximum percentage of seedling emergence in the following spring.  相似文献   

20.
七叶树(Aesculus spp.)是重要的药用经济树种,传统中药娑罗子即为七叶树种子,通常用于治疗胃寒腹胀、小儿疳积、痢疾等病症.国外在18世纪初就将欧洲七叶树(A.hippocastanum L.)种子和幼枝外皮的乙醇制剂用于解热和治疗痔疮、静脉曲张等疾病.  相似文献   

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